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29.5A: Qushlarning xususiyatlari - Biologiya

29.5A: Qushlarning xususiyatlari - Biologiya


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Qushlar issiq qonli hayvonlar bo'lib, qanotlari parvozga bir nechta moslashuvga ega, ammo barcha turlar ucha olmaydi.

O'quv maqsadlari

  • Qushlarning xos xususiyatlarini umumlashtiring

Asosiy nuqtalar

  • Qushlarda izolyatsiyani ta'minlovchi patlar va qanotlarida ikki turdagi uchish patlari mavjud: qanotning uchida birlamchi patlarni surish va tanaga yaqinroq ko'tarishni ta'minlaydigan ikkilamchi patlar.
  • Tanada topilgan kontur patlari silliq, aerodinamik sirt hosil qiladi.
  • Qushlarning ko'krak mushaklari yuqori darajada rivojlangan, chunki ular butun qanotning chayqalishi uchun javobgardir.
  • Qushlarning ikkita klavikulasi bir -biriga bog'lab qo'yilgan bo'lib, ular egiluvchan yoki egiluvchan suyakni hosil qiladi, bu esa egilish paytida elka kamarini ushlab turish uchun etarlicha kuchli.
  • Tana vaznini past tutish uchun qushlarning pnevmatik suyaklari, siydik pufagi yo'q va odatda bitta tuxumdon bor.
  • Qushlar havo yostiqchalari va bir tomonlama havo oqimi va qon bilan o'zaro almashinuv tizimi yordamida samarali nafas olish tizimini ishlab chiqdilar.

Asosiy shartlar

  • pnevmatik: bo'shliqlar havo bilan to'ldirilgan
  • endotermik: tana harorati ichki omillar bilan tartibga solinadigan hayvon
  • furcula: qushlarda klavikulalarning birlashishi natijasida hosil bo'lgan vilkali suyak; tilaklar suyagi
  • kloaka: baliqlar, sudralib yuruvchilar, qushlar va ba'zi ibtidoiy sutemizuvchilarda anus va jinsiy a'zolar teshigi vazifasini bajaradigan umumiy kanal

Qushlarning xususiyatlari

Qushlar endotermikdir, chunki ular uchadi, shuning uchun ular katta miqdorda energiya talab qiladi, bu esa yuqori metabolik tezlikni talab qiladi. Shuningdek, endotermik bo'lgan sutemizuvchilar singari, qushlar ham tanadagi issiqlikni saqlaydigan izolyatsion qoplamaga ega: tuklar. Pastki tuklar deb ataladigan maxsus patlar, ayniqsa, issiqlik yo'qotish tezligini kamaytirish uchun har bir patlar orasidagi bo'shliqlarda havoni ushlab turadigan izolyatsiyalash xususiyatiga ega. Qush tanasining ba'zi qismlari tuklar bilan qoplangan; boshqa patlarning tagida mayin qismi bor, yangi chiqqan qushlar esa tuklar bilan qoplangan.

Tuklar nafaqat izolyatsiya vazifasini bajaribgina qolmay, balki parvozga ham imkon beradi, bu esa havoga ko'tarilishi va ko'tarilishini ta'minlaydi. Qanotdagi tuklar egiluvchan, shuning uchun havo tuklari orasidan harakatlanayotganda kollektiv tuklar harakatlanadi va ajralib chiqadi, bu esa qanotning tortilishini kamaytiradi. Parvoz tuklari assimetrik bo'lib, ular ustidan havo oqimiga ta'sir qiladi va parvoz uchun zarur bo'lgan ko'tarish va tortish kuchini beradi. Qanotlarda uchuvchi patlarning ikki turi uchraydi: asosiy tuklar va ikkilamchi tuklar. Birlamchi tuklar qanotning uchida joylashgan va itarishni ta'minlaydi. Ikkilamchi tuklar tanaga yaqinroq joylashgan, qanotning bilak qismiga biriktirilgan va ko'tarilishini ta'minlaydi. Kontur patlari - tanada topilgan tuklar. Ular parvoz paytida shamol qarshiligi natijasida hosil bo'ladigan tortishishni kamaytirishga yordam beradi, bu esa aerodinamik tekis yuzani yaratadi, bu esa parvozni samarali amalga oshirish uchun qush tanasi ustidan silliq o'tishiga imkon beradi.

Butun qanotning chayqalishi, birinchi navbatda, ko'krak qafasi mushaklarining harakatlari orqali sodir bo'ladi: pektoralis va supracoracoideus. Qushlarda yuqori darajada rivojlangan va ko'pchilik sut emizuvchilarnikiga qaraganda tana massasining ko'p foizini tashkil etuvchi bu mushaklar, sternumda joylashgan, qayiqnikiga o'xshash, pichoq shaklidagi pog'onaga yopishib oladi. Qushlarning sternum boshqa umurtqali hayvonlarnikiga qaraganda kattaroq bo'lib, qanotlarini qoqish bilan ko'tarilish uchun etarli kuch hosil qilish uchun zarur bo'lgan katta mushaklarni o'z ichiga oladi. Ko'pchilik qushlarda uchraydigan boshqa skelet modifikatsiyasi - bu ikki klavikula (bo'yn suyagi) birlashib, furkula yoki suyak suyagini hosil qiladi. Furkula egilish paytida elkama-kamarni qo'llab-quvvatlash uchun etarlicha moslashuvchan.

Parvozning muhim talabi - tana vaznining pastligi. Tana vazni oshgani sayin, uchish uchun zarur bo'lgan mushaklarning chiqishi oshadi. Eng katta tirik qush - tuyaqush. U eng katta sutemizuvchilardan ancha kichik bo'lsa -da, u parvoz qila olmaydi. Uchadigan qushlar uchun tana vaznining kamayishi parvozni osonlashtiradi. Qushlarda tana vaznini kamaytirish uchun bir nechta modifikatsiyalar, shu jumladan suyaklarning pnevmatizatsiyasi mavjud. Pnevmatik suyaklar to'qima bilan to'ldirilgan emas, balki ichi bo'sh. Ular ba'zan havo qoplari bilan bog'langan havo bo'shliqlarini o'z ichiga oladi va ular strukturani mustahkamlash uchun suyak tirgaklariga ega. Pnevmatik suyaklar hamma qushlarda uchramaydi; ular kichik qushlarga qaraganda yirik qushlarda kengroqdir. Skeletning barcha suyaklari pnevmatik emas, garchi deyarli barcha qushlarning bosh suyaklari.

Og'irlikni kamaytiradigan boshqa modifikatsiyalar siydik pufagining etishmasligini o'z ichiga oladi. Qushlarning kloakasi bor: bu suvni chiqindilardan qonga qayta singdirish imkonini beradi. Urik kislotasi suyuqlik sifatida chiqarilmaydi, lekin u urat tuzlariga to'planadi, ular najas bilan birga chiqariladi. Shunday qilib, siydik pufagida suv ushlab turilmaydi, bu tana vaznini oshiradi. Qushlarning ko'p turlarida ikkita emas, balki bitta tuxumdon bor, bu esa tana massasini kamaytiradi.

Suyaklarga cho'zilgan, ularni pnevmatik holga keltiradigan havo qoplari ham o'pka bilan qo'shilib, nafas olish funktsiyasini bajaradi. Havo ikki yo'nalishda oqadigan sutemizuvchilarning o'pkasidan farqli o'laroq, nafas olish va chiqarish jarayonida qushlarning o'pkalari orqali havo oqimi bir yo'nalishda harakat qiladi. Havo qoplari bu bir tomonlama havo oqimiga imkon beradi, bu esa qon bilan o'zaro oqim almashinuv tizimini yaratadi. O'zaro oqim yoki qarama-qarshi oqim tizimida havo bir yo'nalishda, qon esa teskari yo'nalishda oqadi va gaz almashinuvining juda samarali vositasini yaratadi.


29.5A: Qushlarning xususiyatlari - Biologiya

Organizmlarni tasniflashning ahamiyatini belgilang.

Bu tabiiy tasnifga tegishli. Ma'lumotlarning tashkil etilishi organizmlarni aniqlashga qanday yordam berishini, evolyutsion aloqalarni taklif qilishini va guruh a'zolari tomonidan baham ko'riladigan xususiyatlarni bashorat qilish imkonini beradi.

Tirik organizmlarning umumiy ajdodlari uchun DNK va oqsil tuzilmalarining universalligi bilan ta'minlangan biokimyoviy dalillarni tushuntiring.

TOK: DNK va genetik kodning universalligi Marshal Nirenbergga va boshqa kashshof biokimyogarlarga katta ta'sir ko'rsatdi, chunki bu shuni ko'rsatdiki, odamlar umumiy hayot daraxtining bir qismi bo'lib, genetik jihatdan ajratilmagan. Bu o'zimizga va tirik dunyoga qanday qarashimizga ta'sir qilishi kerak.

Muayyan molekulalardagi o'zgarishlar filogeniyani qanday ko'rsatishini tushuntiring.

TOK: Variatsiyalar qisman mutatsiyalarga bog'liq, ular oldindan aytib bo'lmaydigan va tasodifiy hodisalardir, shuning uchun ularni talqin qilishda ehtiyot bo'lish kerak.

Biokimyoviy o'zgarishlardan evolyutsion soat sifatida qanday foydalanish mumkinligini muhokama qiling.

TOK: Biz bu soat doimiy va o'zgarmas tezlikda harakat qilishini taklif qilishdan ehtiyot bo'lishimiz kerak, shuning uchun bu erda ma'lumotlarning talqini juda aniq va noaniqliklar aniq bo'lishi kerak.

Kladistika va kladistikani aniqlang.

Misollar bilan o'xshash va gomologik xususiyatlarni ajrating.

Kladogrammalarni tuzishda ishlatiladigan usullarni va ulardan qanday xulosalar chiqarish mumkinligini aytib bering.

Oddiy kladogramma tuzing.

Morfologik yoki biokimyoviy ma'lumotlardan foydalanish mumkin.

Kladogrammalarni filogenetik munosabatlar nuqtai nazaridan tahlil qiling.

Kladogrammalar va tirik organizmlarning tasnifi o'rtasidagi munosabatni muhokama qiling.


Parrandachilik biologiyasidagi antioksidant tizimlar: superoksid dismutaza

Mualliflik huquqi: & nusxa ko'chirish 2015 Piter Surai F, Bu Creative Commons Attribution litsenziyasi shartlari asosida tarqatiladigan ochiq kirish maqolasi bo'lib, u asl muallif va manbani hisobga olgan holda, har qanday muhitda cheksiz foydalanish, tarqatish va ko'paytirishga ruxsat beradi.

Xulosa

Tijorat parrandachilik mahsuloti o'sayotgan jo'jalar, selektsionerlar va tijorat qatlamlarining mahsuldorligi va reproduktiv ko'rsatkichlarining pasayishi bilan bog'liq bo'lgan turli stresslar bilan bog'liq. Ko'payib borayotgan dalillar shuni ko'rsatadiki, parranda go'shti ishlab chiqarishdagi stresslarning aksariyati hujayra darajasida oksidlovchi stress bilan bog'liq. So'nggi paytlarda hujayra antioksidantlarini himoya qilish kontseptsiyasi qayta ko'rib chiqildi va hujayraning redoks holatini saqlash va hujayra signalizatsiyasiga alohida e'tibor berildi. Aslida, tirik hujayraning antioksidant tizimlari uchta asosiy mudofaa darajasiga asoslanadi va superoksid dismutaza (SOD) antioksidant himoya tarmog'ining birinchi darajasiga tegishli ekanligi ko'rsatilgan. Hujayra antioksidant mudofaa bir nechta variantni o'z ichiga oladi va stress sharoitida vigenen faollashishi asosiy adaptiv mexanizm sifatida ko'rib chiqiladi. Vitagen oilasi tioredoksinlar, sirtuinlar, issiqlik zarbasi oqsillari va SOD kabi himoya molekulalarining sintezini tartibga soluvchi turli genlarni o'z ichiga oladi. Biroq, yozish paytida SOD ning parranda biologiyasidagi roli va ta'siri to'g'risida keng qamrovli sharhlar mavjud emas. Shuning uchun, ushbu sharhning maqsadi - parrandachilik biologiyasida SODning rolini tanqidiy tahlil qilish, uning vazifalari vitagen tarmog'ining muhim qismi sifatida. Parranda fiziologiyasi va stresslarga moslashuvi bilan bog'liq so'nggi ma'lumotlarning tahlilidan shunday xulosaga kelish mumkin: a) SOD muhim vigenen sifatida hujayra/organizmning turli stress sharoitlariga moslashuvida asosiy harakatlantiruvchi kuch hisoblanadi. Darhaqiqat, stress sharoitida SOD ning qo'shimcha sintezi ROS hosil bo'lishini kamaytirishning moslashuvchan mexanizmi hisoblanadi b) Agar stress juda yuqori bo'lsa, SOD faolligi pasayadi va apoptoz faollashtirilsa c) SOD ifodasida to'qimalarga xos farqlar mavjud, bu ham kuchga bog'liq. Issiqlik, og'ir metallar, mikotoksinlar va boshqa stress omillari kabi stress omillarining d) Tovuq embrion to'qimalarida va urug'ida lipid peroksidlanishidan samarali himoya qilish uchun ko'rsatiladi. e) SOD issiqlik va sovuq stressda, toksiklik stressida himoya qiladi parrandachilikda, shuningdek, oksidlanish-stress bilan bog'liq boshqa sharoitlarda f) stress sharoitida gomeostazning samarali saqlanishini ta'minlash uchun hujayra/tananing antioksidant tarmog'i ichida murakkab o'zaro ta'sirlar mavjud. Darhaqiqat, ko'p hollarda ozuqa tarkibidagi ozuqaviy antioksidantlar (E vitamini, selen, karotinoidlar, fitokimyoviy moddalar va boshqalar) SOD ifodasini oshirishi mumkin g) parrandachilikning stress sharoitida SOD ko'tarilishining ozuqaviy vositalari va fiziologik va tijorat oqibatlari keyingi tekshirishni kutmoqda h. ) stress sharoitida vitagen regulyatsiyasi stressni boshqarishning samarali vositasi sifatida paydo bo'ladi.

Kalit so'zlar

Antioksidantlar tizimi tovuq HSP parranda stress vitagenlari

Qisqartmalar

AO- antioksidant ARE- antioksidant javob elementi CAT & ndash katalaz NOS- azot oksidi sintaz GSH & ndash glutatyon GSHPx- glutatyon peroksidaza GST- glutatyon transferaza HSP va ndash issiqlik zarba oqsili MDA- malondialdegid NF- va kappa-N-yadroli omil -2 bilan bog'liq omil 2 SOD &ndash superoksid dismutaza.

Kirish

Savdo parrandachilik ishlab chiqarish o'sayotgan jo'jalar, selektsionerlar va tijorat qatlamlarining mahsuldorligi va reproduktiv ko'rsatkichlarining pasayishi uchun mas'ul bo'lgan turli xil stresslar bilan bog'liq. Dalillarning ko'payishi shuni ko'rsatadiki, parrandachilikda uyali darajadagi stresslarning aksariyati oksidlovchi stress bilan bog'liq. So'nggi paytlarda hujayra antioksidantlarini himoya qilish kontseptsiyasi qayta ko'rib chiqildi va hujayraning redoks holatini saqlash va hujayra signalizatsiyasiga alohida e'tibor berildi. Tirik hujayraning antioksidant mudofaa tarmog'i uchta asosiy mudofaa darajasiga asoslangan va bir nechta variantni o'z ichiga oladi [1-2]: prooksidant fermentlarning faolligini kamaytiradigan kislorod kontsentratsiyasini kamaytirish va elektron zanjiri samaradorligini oshirish taklif qilingan. mitoxondriya va elektron oqishining kamayishi, superoksid ishlab chiqarilishiga olib keladi, ARE bilan bog'liq AO fermentlarining sintezi, shu jumladan superoksid dismutaz (SOD), glutatyon peroksidaza bilan turli transkripsiya omillarini (masalan, Nrf2, NF- va kappaB va boshqalarni) qo'zg'atishi natijasida dastlabki radikallarni tozalash orqali zanjir boshlanishining oldini oladi. (GSH-Px), katalaza (CAT), glutatyon reduktaza (GR), glutatyon transferaz (GST) va boshqalar metall ionlarini (metall bilan bog'laydigan oqsillar) va parchalanadigan peroksidlarni natrik bo'lmagan, toksik bo'lmagan mahsulotlarga (Se- GSH-Px) zanjirni peroksil va alkoksil radikallari (E, C vitaminlari, kamaytirilgan glutatyon (GSH), siydik kislotasi, ubiquinol kabi oraliq radikallarni tozalash yo'li bilan sindirish. , bilirubin va boshqalar) shikastlangan molekulalarni (metionin sulfoksid reduktaza, DNKni tiklash fermentlari, chaperonlar va boshqalar) ta'mirlash va olib tashlash va vitagen faollashishi va sintezi va himoya molekulalarining (GSH, tioredoksinlar, SOD, issiqlik zarbasi oqsillari, sirtuinlar, sirtuinlar) ko'payishi. va boshqalar.). Darhaqiqat, stress bilan kurashishning samarali strategiyalarini ishlab chiqish uchun fon sifatida parrandalarning stressga chidamliligida vitagenlarning rolini ochib berish yangi tadqiqot mavzusidir [1-5]. Ma'lumki, adaptiv SOD sintezi vitagen nazorati ostida. Biroq, yozish paytida, SODning parrandachilik biologiyasidagi o'rni va ta'siri to'g'risida keng qamrovli sharhlar paydo bo'lmadi. Shu sababli, ushbu sharhning maqsadi SOD ning parranda biologiyasidagi rolini tanqidiy tahlil qilish va uning hujayralar va butun organizmning turli xil stress sharoitlariga moslashish qobiliyatiga javob beradigan vigenen tarmog'ining muhim qismi sifatidagi funktsiyalariga alohida e'tibor berishdir.

Erkin radikallar va reaktiv kislorod va azot turlari

Erkin radikallar - bir yoki bir nechta juftlashtirilmagan elektronni o'z ichiga olgan atomlar yoki molekulalar. Erkin radikallar juda beqaror va reaktiv bo'lib, DNK, oqsillar, lipidlar va uglevodlarni o'z ichiga olgan biologik ahamiyatga ega bo'lgan barcha turdagi molekulalarga zarar etkazishga qodir. Hayvonlar tanasi organizmning normal metabolik faolligining tabiiy natijasi sifatida va immunitet tizimining bosqinchi mikroorganizmlarni yo'q qilish strategiyasining bir qismi sifatida shakllangan erkin radikallarning doimiy hujumiga duchor bo'ladi. Reaktiv kislorod turlari (ROS) va reaktiv azot turlari (RNS) degan umumiy atamalar kiritilgan [6] va ular nafaqat kislorod yoki azot radikallarini, balki kislorod va azotning ba'zi radikal bo'lmagan reaktiv hosilalarini ham o'z ichiga oladi.

Superoksid (O2 *-) biologik tizimlarda mitoxondriyada normal nafas olish paytida va 37 & degCda 1 x 10-6 soniya oralig'ida yarimparchalanish davri bilan avtoksidlanish reaktsiyalari natijasida hosil bo'ladigan asosiy erkin radikaldir. Superoksid prostetik ferment guruhining o'tish metallari bilan beqaror komplekslar hosil bo'lishi natijasida ba'zi fermentlarni faolsizlantirishi mumkin, so'ngra faol joyning oksidlanish o'zini o'zi yo'q qilishi mumkin [7]. Vaziyatga qarab, superoksid oksidlovchi yoki qaytaruvchi vosita vazifasini bajarishi mumkin. Shuni ta'kidlash kerakki, superoksid juda xavfli emas va ikki qatlamli lipid membranani tez o'tmaydi. Biroq, superoksid boshqa, kuchliroq ROS ning kashshofidir. Masalan, u azot oksidi bilan kuchli oksidlovchi peroksinitrit (ONOO-) hosil bo'lishi bilan reaksiyaga kirishadi, bu o'z-o'zidan parchalanish natijasida reaktiv oraliq mahsulotlarning paydo bo'lishiga olib keladi [9-10]. Aslida, ONOO- turli xil biomolekulalarga, shu jumladan oqsillarga (tirozin yoki triptofan qoldiqlarini nitratlash yoki metionin yoki selenosistein qoldiqlarini oksidlash orqali), DNK va lipidlarga zarar etkazishi ko'rsatilgan [11]. Superoksid, shuningdek, elektron berish orqali yanada kuchli radikallarni ishlab chiqarishda ishtirok etishi va shu bilan kamaytirishi mumkinmi? Cu 2+ va Fe 3+ dan Fe 2+ va Cu+ gacha, quyidagicha:

Fe2+ ​​va Cu+ ning H bilan keyingi reaksiyalari2O2 Fenton reaktsiyasida gidroksil radikalining manbai (*OH):

Superoksid radikalining o'tish metallari va o'tish metallarining vodorod peroksid bilan reaktsiyasi yig'indisi Xabar-Vays reaktsiyasi deb nomlanadi. Shuni ta'kidlash kerakki, superoksid radikal-ikki qirrali qilich va rdquo. Bu faollashgan polimorfonukulyar leykotsitlar va boshqa fagotsitlar tomonidan bakteritsid faoliyatining muhim tarkibiy qismi sifatida ishlab chiqarilganda foydalidir, ammo ortiqcha bo'lsa, u yallig'lanish bilan bog'liq bo'lgan to'qimalarning shikastlanishiga olib kelishi mumkin (1-rasm).

1-rasm: Hayvonlar / parrandalar fiziologiyasida SODning himoya rollari.
Superoksid (O2*) - mitoxondriyalarda normal nafas olish paytida biologik tizimlarda ishlab chiqariladigan asosiy erkin radikal. Mitokondriyadan tashqari, superoksid boshqa oksidlanish-qaytaruvchi faol fermentlar, shu jumladan ksantin oksidaza, sitokrom p450, siklooksigenaza, lipoksigenaza, nitrat oksidi sintazasi (NOS) va NADPH oksidazalari (NOXs) tomonidan ishlab chiqarilishi mumkin. Superoksid o'z-o'zidan signal beruvchi molekula sifatida juda xavfli emas. Shu bilan birga, superoksid peroksinitrit va gidroksil radikalni o'z ichiga olgan boshqa, yanada kuchli ROSning kashfiyotchisi bo'lib, u barcha turdagi biologik molekulalarga, shu jumladan oqsillarga, lipidlarga va nuklein kislotalarga zarar etkazishi mumkin. Bu immunitetning pasayishiga, ishlab chiqarish va reproduktiv ko'rsatkichlarning pasayishiga va turli kasalliklarning rivojlanishiga olib keladi. Shunday qilib, SODning uchta asosiy shakli superoksidni vodorod peroksidga aylantirish uchun javobgardir, bu esa GSH-Px va/yoki katalaza yordamida suv hosil bo'lishi bilan zararsizlantiriladi. Bu superoksid radikalining zararli ta'sirini oldini oladi.

Gidroksil radikal -bu eng reaktiv tur bo'lib, uning yarim umri atigi 10-9 soniya. U tegishi mumkin bo'lgan har qanday biologik molekulaga zarar etkazishi mumkin, ammo uning tarqalish qobiliyati reaksiyaga kirishdan oldin atigi ikki molekulyar diametr bilan cheklangan [12]. Shuning uchun ko'p hollarda gidroksil radikalining zararli ta'siri uning hosil bo'lish joyi bilan chegaralanadi. Umuman olganda, gidroksil radikali inson/hayvon tanasida tabiiy manbalardan (radon gazi, kosmik nurlanish) va sun'iy manbalardan (elektromagnit nurlanish va radionuklid bilan ifloslanish) nurlanish natijasida hosil bo'lishi mumkin. Aslida, ko'p hollarda gidroksil radikal lipid peroksidlanishida zanjirli reaktsiyaning qo'zg'atuvchisi hisoblanadi.

Shuning uchun ROS/RNS to'qimalarda fiziologik metabolizm jarayonida doimiy ravishda in vivo hosil bo'ladi. Mitokondriyadagi elektron-transport zanjiri organizmda superoksid ishlab chiqarishning asosiy qismi uchun javobgar ekanligi qabul qilingan. Mitoxondriyali elektron tashish tizimi hujayra tomonidan ishlatiladigan barcha kislorodning 85% dan ko'prog'ini iste'mol qiladi va elektronni tashish samaradorligi 100% emasligi sababli elektronlarning taxminan 1-3% zanjirdan chiqib ketadi va molekulyar kislorodning birdaniga kamayishiga olib keladi. superoksid anion hosil bo'lishi [13-15]. Taxminan 10 12 O2 Har bir kalamush hujayrasi tomonidan har kuni qayta ishlanadigan molekulalar va agar qisman kislorod molekulalarining oqishi taxminan 2%bo'lsa, bu har bir hujayradan kuniga 2 x 10 10 ta ROS molekulasini beradi. Xolliuell [17] tomonidan qiziqarli hisob-kitob qilingan bo'lib, inson organizmida yiliga 1,72 kg superoksid radikali ishlab chiqariladi. Stress holatida uning miqdori sezilarli darajada oshadi. Shubhasiz, bu hisob -kitoblar shuni ko'rsatadiki, tanadagi erkin radikallar ishlab chiqarilishi juda katta va himoyalanmagan bo'lsa, minglab biologik molekulalarga osonlikcha zarar etkazilishi mumkin.

Antioksidant himoyasining uch darajasi

Evolyutsiya davrida tirik organizmlar ROS va RNS bilan kurashish uchun o'ziga xos antioksidant himoya mexanizmlarini ishlab chiqdilar [6]. Shuning uchun faqat tirik organizmlarda kislorodli muhitda omon qolishlariga imkon beradigan tabiiy antioksidantlarning mavjudligi [13]. Bu mexanizmlar &ldquoantioksidant tizim&rdquo umumiy atamasi bilan tavsiflanadi. U turli xil va hujayralarni erkin radikallar ta'siridan himoya qilish uchun javobgardir. Ushbu tizim quyidagilarni o'z ichiga oladi [18-20]:

yog'da eriydigan tabiiy antioksidantlar (A, E vitaminlari, karotenoidlar, ubikinonlar va boshqalar).

suvda eriydigan antioksidantlar (askorbin kislotasi, siydik kislotasi, taurin, karnitin va boshqalar)

antioksidant fermentlar: GSH-Px, CAT va SOD

glutatyon tizimidan tashkil topgan tiol -redoks tizimi (glutation/glutation reduktaza/glutaredoksin/glutation peroksidaza va tioredoksin tizimi (tioredoksin/tioredoksin peroksidaza/tioredoksin reduktaza).

Himoya qiluvchi antioksidant birikmalar organellalarda, hujayra osti bo'linmalarida yoki hujayradan tashqari bo'shliqda joylashgan bo'lib, maksimal hujayra himoyasini ta'minlaydi. Shunday qilib, tirik hujayraning antioksidant tizimlari uchta asosiy himoya darajasini o'z ichiga oladi [18-21].

Birinchi mudofaa darajasi erkin radikallarning prekursorlarini olib tashlash yoki katalizatorlarni faolsizlantirish orqali erkin radikal shakllanishining oldini olish uchun javobgardir va uchta antioksidant fermentdan, ya'ni SOD, GSH-Px va CAT va metallni bog'laydigan oqsillardan iborat. Superoksid radikali hujayradagi fiziologik sharoitda hosil bo'lgan asosiy erkin radikal bo'lgani uchun [13] SOD (EC 1.15.1.1) hujayradagi antioksidant himoyaning birinchi darajasining asosiy elementi hisoblanadi [18]. Bu ferment quyidagi reaktsiyada superoksid radikalini parchalaydi:

SOD ta'sirida hosil bo'lgan vodorod periks GSH-Px yoki CAT tomonidan zararsizlantirilishi mumkin, bu esa uni suvga quyidagicha kamaytiradi:

O'tish metall ionlari, shuningdek, lipid gidroperoksidlarning aldegidlar, alkoksil radikallari va peroksil radikallari kabi sitotoksik mahsulotlarga parchalanishini tezlashtiradi. Shuning uchun ham birinchi darajali mudofaa darajasiga metallni bog'lovchi oqsillar (transferrin, laktoferrin, haptoglobin, gemopexin, metallotionin, seruloplazmin, ferritin, albumin, miyoglobin va boshqalar) kiradi. Aftidan, karnitin mitoxondriyadagi erkin radikallarni ishlab chiqarishni tartibga soluvchi funktsiyalari bilan [1] antioksidant mudofaaning birinchi darajasining bir qismi bo'lishi mumkin.

Afsuski, hujayradagi bu birinchi antioksidant himoya darajasi erkin radikal shakllanishini to'liq oldini olish uchun etarli emas va ba'zi radikallar lipid peroksidatsiyasini boshlaydigan va DNK va oqsillarga zarar etkazadigan antioksidant xavfsizlik ekranining profilaktik birinchi darajasidan o'tib ketadi. Shuning uchun ikkinchi darajadagi himoya zanjirni buzuvchi antioksidantlardan iborat - vitamin E, ubiquinol, karotenoidlar, A vitamini, askorbin kislotasi, siydik kislotasi va boshqa ba'zi antioksidantlar. Glutatyon va tioredoksin tizimlari antioksidant himoyaning ikkinchi darajasida ham muhim rol o'ynaydi. Zanjirni buzadigan antioksidantlar tarqalish reaktsiyasining zanjir uzunligini imkon qadar kichik ushlab turish orqali peroksidlanishni inhibe qiladi. Shuning uchun ular zanjir reaktsiyasida peroksil radikal oraliq moddalarni tozalash orqali lipid peroksidatsiyasining tarqalish bosqichini oldini oladi:

(LOO* lipid peroksil radikali Toc - tokoferol, Toc* - tokoferoksil radikali, LOOH &ndash lipid gidroperoksid).

Hatto hujayradagi antioksidant himoyaning ikkinchi darajasi ham ROS va RNSning lipidlar, oqsillar va DNKga zararli ta'sirini oldini ololmaydi. Bunda uchinchi darajali mudofaa buzilgan molekulalarni yo'q qiladigan yoki ularni tuzatadigan tizimlarga asoslangan. Antioksidant himoyaning bu darajasiga lipolitik (lipazlar), proteolitik (peptidazlar yoki proteazalar) va boshqa fermentlar (DNK tuzatish fermentlari, metionin sulfoksid reduktaza, ligazalar, nukleazalar, polimerazalar, oqsillar, fosfolipazalar va turli transferazalar) va xaperonlar, shu jumladan HSPlar kiradi.

Tanadagi antioksidant-prooksidant muvozanati va oksidlovchi stress

Tanada/hujayrada antioksidant mudofaa va ta'mirlash tizimlari va erkin radikallar hosil bo'lishi o'rtasida nozik tanqidiy muvozanat mavjud [18-20]. Fiziologik sharoitda &ldquobalances&rdquo deb ataladigan o'ng va chap qismlari muvozanatda bo'ladi, ya'ni erkin radikal hosil bo'lishi antioksidant tizim tomonidan neytrallanadi va ba'zi erkin radikallar va ularning metabolizm mahsulotlari hujayra signalizatsiyasi va transkripsiya faktorini faollashtirishda ishtirok etadi. Ekzogen omillar organizmning antioksidant tizimining samaradorligini oshiradigan eng muhim elementlardan biridir. Ozuqadagi tabiiy va sintetik antioksidantlar, shuningdek Mn, Cu, Zn va Se ning maqbul darajalari to'qimalarda endogen antioksidantlarning samarali darajasini saqlab turishga yordam beradi. Optimal parhez tarkibi antioksidantlarni oziq -ovqat mahsulotlarini samarali so'rilishiga va metabolizmasiga imkon beradi. Erkin radikal ishlab chiqarishdan samarali himoya qilish uchun optimal harorat, namlik va boshqa atrof-muhit sharoitlari ham talab qilinadi. Antibiotiklar va boshqa dorilar yordamida turli kasalliklarning oldini olish samarali antioksidant himoyaning ajralmas qismi hisoblanadi.

Turli xil stress sharoitlari erkin radikallarning ortiqcha ishlab chiqarilishi bilan bog'liq va oksidlovchi stressni keltirib chiqaradi, ya'ni to'qimalarning potentsial shikastlanishiga olib keladigan prooksidant-antioksidant muvozanatining buzilishi [22]. Stress sharoitlarini odatda uchta asosiy toifaga bo'lish mumkin [19]. Eng muhim qismi-bu oziqlanishdagi stress sharoitlari, shu jumladan PUFAlarning yuqori miqdori, E vitamini, Se, Zn yoki Mn, Fe-haddan tashqari yuklanish, gipervitaminoz A va ozuqada turli mikotoksinlar va boshqa toksik birikmalar mavjudligi. Stress omillarining ikkinchi guruhiga atrof-muhit sharoitlari kiradi: harorat yoki namlikning oshishi, giperoksiya, radiatsiya va boshqalar. Ichki stress omillariga turli bakterial yoki virusli kasalliklar, shuningdek allergiya kiradi. Yuqorida sanab o'tilgan barcha shartlar mitoxondriyalarda erkin radikallar hosil bo'lishini rag'batlantiradi.

Tirik hujayralar doimiy ravishda ROS hosil bo'lish va inaktivatsiya jarayonini muvozanatlashtiradi va natijada ROS darajasi past bo'lib qoladi, lekin hali ham noldan yuqori. Noqulay atrof-muhit sharoitlari organizmlarning tajovuzkor bo'lgan muhitga qarshilik ko'rsatishga urinishlarini boshlaydi [23]. Hujayralar odatda antioksidant/oksidant muvozanatini tiklash maqsadida turli xil antioksidantlarni (glutation, antioksidant fermentlar va boshqalar) qo'shimcha sintez qilish orqali engil oksidlovchi stressga toqat qila oladi. Shu bilan birga, energiya sarflari oshdi va nafas olish faollashdi, bu esa ROSning hosildorligini oshirdi [23]. Biroq, bu moslashuv mexanizmlarining imkoniyatlari cheklangan. Erkin radikal ishlab chiqarish antioksidant tizimning ularni zararsizlantirish qobiliyatidan oshib ketganda, oksidlovchi stress rivojlanadi va hujayra membranalarida to'yinmagan lipidlarga, oqsillardagi aminokislotalarga va DNKdagi nukleotidlarga zarar etkazadi va natijada membrana va hujayra yaxlitligi buziladi. Membrananing shikastlanishi turli xil ozuqa moddalarining so'rilish samaradorligining pasayishi bilan bog'liq bo'lib, organizmda vitaminlar, aminokislotalar, noorganik elementlar va boshqa oziq moddalar muvozanatining buzilishiga olib keladi. Bularning barchasi hayvonlarning mahsuldorligi va reproduktiv ko'rsatkichlarining pasayishiga olib keladi. Immunitetning etishmasligi va yurak-qon tomir tizimida, miya va neyronlar va mushaklar tizimidagi lipid peroksidlanishining kuchayishi tufayli yuzaga kelgan noxush o'zgarishlar vaziyatni yanada yomonlashtiradi [20].

Yuqorida ko'rsatilgandek, tanadagi barcha antioksidantlar antioksidant mudofaa uchun javob beradigan & ldquoteam & rdquo vazifasini bajaradi va biz bu jamoani antioksidant tizim deb ataymiz. Ushbu jamoada bir a'zo boshqasiga samarali ishlashga yordam beradi. Agar bu jamoadagi munosabatlar samarali bo'lsa, bu faqat muvozanatli ovqatlanish va antioksidantlar etarli miqdorda ta'minlangan taqdirda sodir bo'ladi, hatto E vitamini kabi antioksidantlarning past dozalari ham samarali bo'lishi mumkin. Boshqa tomondan, bu jamoa yuqori stress sharoitlariga duchor bo'lganda, erkin radikal ishlab chiqarish keskin ortadi. Bu vaqtda, tashqi yordamisiz, asosiy organlar va tizimlarning shikastlanishining oldini olish qiyin. Bu tashqi yordam & rsquo - bu tabiiy antioksidantlar kontsentratsiyasining oshishi bilan dietaga qo'shimcha. Oziqlantiruvchi yoki em -xashak ishlab chiqaruvchi uchun tanadagi ichki antioksidantlar guruhi qachon yordamga muhtojligini, bu yordamning qanchasini va iqtisodiy rentabelligini bilish juda qiyin. Erkin radikal ishlab chiqarish va antioksidant himoyasi o'rtasidagi to'g'ri muvozanatni saqlash muhimligini yana bir bor eslash kerak. Darhaqiqat, ROS va RNS fiziologik funktsiyalarni tartibga solishda ishtirok etadigan yana bir jozibali yuzga ega.

Shuning uchun antioksidant himoya mexanizmlari bir nechta variantlarni o'z ichiga oladi [1-3,19-20]:

Mahalliy kislorod kontsentratsiyasini kamaytirish

Prooksidlovchi fermentlarning faolligini pasaytirish va mitoxondriyadagi elektron zanjirining samaradorligini oshirish superoksid (karnitin) ishlab chiqarishni kamaytiradi.

Turli transkripsiya omillarini (masalan, Nrf2 va NF-kB) induktsiyasi bilan redoks signalizatsiyasi va AO fermentlari (SOD, GSH-Px, katalaza, GR, GST va boshqalar) va boshqa muhim himoya molekulalarining ARE bilan bog'liq sintezi bilan gen ekspressiyasi.

Vita-gen faollashishi va sintezi va himoya molekulalari ekspresyonining oshishi (HSP, tioredoksinlar, sirtuinlar, SOD va boshqalar).

Bog'lovchi metall ionlari (metall bog'lovchi oqsillar) va metallni xelatlash

Peroksidlarni radikal bo'lmagan, toksik bo'lmagan mahsulotlarga aylantirish orqali parchalash (Se-GSH-Px)

Peroksil va alkoksil radikallari (vitaminlar E, C, GSH, siydik kislotasi, karnitin, ubiquinol, bilirubin va boshqalar) kabi oraliq radikallarni tozalash orqali zanjirni buzish.

Antioksidant (E vitamini) qayta ishlash mexanizmlari (B1, B2, Se vitaminlari, askorbin kislotasi)

Zararlangan molekulalarni tuzatish va olib tashlash (Msr, DNA repair fermentlari, proteazomalar, HSP va boshqa chaperonlar va boshqalar)

Apoptozni faollashtirish va terminal zararlangan hujayralarni olib tashlash va mutagenezni cheklash.

Yana bir bor ta'kidlash joizki, ROS endi mitoxondriyal nafas olishning zaharli yon mahsuloti sifatida qaralmaydi, lekin ular uyali signalizatsiya yo'llarini boshqarishda ularning roli uchun qadrlanadi. Darhaqiqat, hayotimizning stressli sharoitlariga moslashish tanadagi vitagen tarmog'i orqali amalga oshiriladi.

Biologik tizimlarda superoksid dismutaza

SOD 1969 yilda Makkord va Fridovich tomonidan karbonat angidraz yoki mioglobin preparatlarida fermentativ faollik sifatida kashtan oksidaza tomonidan sitokrom C ning aerobik kamayishini inhibe qilgan [25]. Shunday qilib, ancha oldin kashf etilgan gemokuprein Cu, Zn-SODga aylandi [26]. Ushbu kashfiyot erkin radikal tadqiqotlarda yangi davrni ochdi. Hozirgi vaqtda sutemizuvchilarda SOD ning uchta alohida izoformasi aniqlangan va ularning genomik tuzilishi, cDNK va oqsillari tavsiflangan [27]. Fe-SOD fermentining to'rtinchi shakli turli bakteriyalardan ajratilgan, ammo hayvonlarda topilmagan. Bundan tashqari, nikel o'z ichiga olgan SODning yangi turi Streptomyces sp ning sitozolik fraktsiyalaridan aniq bir xillikka tozalangan. [28]. Ko'pgina biologik tizimlarda SODning biosintezi yaxshi nazorat qilinadi. Aslida, ortib borayotgan pO ga ta'sir qilish2, O ning hujayra ichidagi oqimlari kuchaygan2-, metall ionlarining buzilishi va bir nechta ekologik oksidlovchilarga ta'sir qilish prokaryotik va eukaryotik organizmlarda SOD sintezi tezligiga ta'sir qilishi ko'rsatilgan [29]. NF-&kappaB, AP-1, AP-2 va Sp1, shuningdek, CCAAT-ni kuchaytiruvchi bog'lovchi oqsil (C/EBP) kabi bir qator transkripsiya omillari barcha moddalarning konstitutsiyaviy yoki induksiyaviy ifoda darajasini tartibga solishi ko'rsatilgan. uchta SOD [30]. Bundan tashqari, transkripsiyani nazorat qilishdan tashqari, epigenetik regulyatsiya va transkripsiyadan keyingi modifikatsiyalar SOD funktsional faolligini tartibga solish uchun javobgardir [30]. SOD1, SOD2 va SOD3 ning qiyosiy xarakteristikalari umumlashtiriladi 1-jadval [30,31].

Fermentlar CuZn-SOD Mn-SOD EC-SOD
Gen belgisi (odam/sichqoncha) SOD1/Sod1 SOD2/Sod2 SOD3/Sod3
Xromosoma joylashuvi odam/sichqoncha) HAS21/MMU16 HAS6/MMU17 HAS4/MMU5
Ferment nuqsonlari tufayli yuzaga keladigan kasallik Yanal amiotrofik skleroz (ALS) Hech kim Hech kim
Metall ko-faktor(lar) Cu2+ - katalitik faol
Zn2+ - ferment barqarorligini saqlaydi
Mn2+ - katalitik faol Cu2+ - katalitik faol
Zn2+ - ferment barqarorligini saqlaydi
Faol shakl Dimer Tetramer Tetramer
Molekulyar massa, kDa 88 32 135
Hujayra ostidagi joylar Sitozol, mitoxondriyalarning membranalararo bo'shlig'i, yadro Mitoxondriya matritsasi Hujayradan tashqari matritsa va qon aylanishi
To'qimalarning taqsimlanishi (yuqoridan pastgacha) Jigar, buyrak, miya, yurak Yurak, miya, skelet mushaklari Qon tomirlari, o'pka, buyrak, bachadon
Tarjimadan keyingi o'zgartirish Nitratlanish, fosforillanish, glutatiolyatsiya, glikatsiya Asetillanish, nitrlanish, fosforlanish Glikozillanish
Induktsiya Qo'zg'almas Qabul qilinmaydi Antioksidantlar tomonidan qo'zg'atilgan va NRF orqali boshqariladi

1 -jadval: Sutemizuvchilar superoksid dismutazasining biokimyoviy xususiyatlari ([30-31] dan moslashtirilgan).

SOD1 yoki Cu, Zn-SOD bu oilaning birinchi fermenti bo'lib, mis va rux o'z ichiga olgan gomodimer bo'lib, deyarli faqat hujayra ichidagi sitoplazmatik bo'shliqlarda uchraydi. It exists as a 32 kDa homodimer and is present in the cytoplasm and nucleus of every cell type examined [27]. The chromosomal localization and characteristics of the sod1 gene have been identified in rodents, bovines, and humans and the human sod1 gene is shown to be localized on chromosome 21q22. Furthermore, sod1 gene consists of five exons interrupted by four introns, which is significantly similar in different species in terms of the size of exons, particularly the coding regions [30]. The sequence and structure of Cu, Zn-SOD is highly conserved from prokaryotes to eukaryote and mammalian SOD1 is highly expressed in the liver and kidney [32]. Enzymatic activity of SOD1 depends on the presence of the Cu and Zn. While copper is needed for SOD1 catalytic activity, Zn participates in proper protein folding and stability. Over 100 mutations in the human gene SOD1 are described to lead to some inherited diseases, but their mechanisms remain unclear [33].

The second member of the family (SOD2) has manganese (Mn) as a cofactor and therefore called Mn-SOD. SOD2 is shown to have a unique genetic organization and little similarity with SOD1 and SOD3 [30]. The primary structure of SOD2 genes is shown to be highly conserved and it shares more than 90% sequence homology in the coding region in mouse, rat, bovine and human and the human sod2 is located on chromosome 6q25.3 [30]. It was shown to be a 96 kDa homotetramer and located exclusively in the mitochondrial matrix, a prime site of superoxide radical production [6]. Therefore the expression of Mn-SOD is considered to be essential for the survival of all aerobic organisms from bacteria to humans and it participates in the development of cellular resistance to oxygen radical-mediated toxicity [34]. Indeed, Mn-SOD is shown to play a critical role in the defense against oxidant-induced injury and apoptosis in various cells. In fact, Mn-SOD is inducible enzyme and its activity is affected by cytokines and oxidative stress. Therefore, Mn-SOD has been shown to play a major role in promoting cellular differentiation and in protecting against hyperoxia-induced pulmonary toxicity [34] being a crucial determinant of redox status of the cell. Furthermore, Mn-SOD influences the activity of transcription factors (such as HIF-1&alpha, AP-1, NF-&kappaB and p53) and affects DNA stability [35]. A critical role of Mn-SOD under physiological and pathological conditions has recently been reviewed in details and the following findings of Mn-SOD confirm the critical role of Mn-SOD in the survival of aerobic life [36-39]:

Escherichia coli and yeasts lacking the Mn-SOD gene are highly sensitive to oxidative stress

Mn-SOD gene knockout mice can only survive few days after birth, with pathological findings of many various diseases due to mitochondrial disorder, suggesting a critical role of the enzyme

Cells transfected with Mn-SOD cDNAs have increased resistance to various free radical-generating toxicants (paraquat, tumor necrosis factor, doxorubicin, mitomycin C, irradiation, ischemic reperfusion, smoking, etc.)

Human Mn-SOD gene transgenic mice show reduced severity of free radical-induced pulmonary damage and adriamycin-induced myocardial damage.

In 1982, a third SOD isozyme was discovered by Marklund and co-workers and called extracellular superoxide dismutase (EC-SOD), due to its exclusive extracellular location. EC-SOD is a glycoprotein with a molecular weight of 135,000 kDa and high affinity for heparin [40]. However, there are some speciesspecific variations in molecular weight. The human EC-SOD gene has been mapped to chromosome 4q21 and consists of three exons and two introns [41]. The full-length mouse ECSOD cDNA is shown to be 82% identical to that of rat and 60% identical to the human EC-SOD [30]. EC-SOD is the only antioxidant enzyme that scavenges superoxide specifically in the extracellular space. EC-SOD is present in various organisms as a tetramer or, less commonly, as a dimer and contains one copper and one zinc atom per subunit, which are required for enzymatic activity [42]. The expression pattern of EC-SOD is highly restricted to the specific cell type and tissues where its activity can exceed that of Cu,Zn-SOD or Mn- SOD. As a copper-containing enzyme, the activity of EC-SOD is regulated by copper availability [41]. EC-SOD is comparatively resistant to high temperatures, extreme pH, and high urea concentrations it can be inhibited by various agents including azide and cyanide and inactivated by diethyldithiocarbamate and hydrogen peroxide. Oxidative stress and post-translational modification of EC-SOD are shown to cause loss of EC-SOD activity [30].

SOD in avian biology

Chicken SOD

Chicken SOD was described and purified in early 1970. Indeed, in chicken liver two types of SOD were identified, one of which was localized in the mitochondria while the other was found in the cytosol [43]. The cytosol SOD was inhibited by cyanide, whereas the mitochondrial enzyme was not. Later this feature was used to distinguish between two forms of enzymes during assays. The cytosol SOD was purified to homogeneity with apparent molecular weight in presence of mercaptoethanol to be 30,600 Da and to contain copper and zinc, being similar to the other Cu, Zn-SOD which have been isolated from diverse eukaryotes. In fact, purified cytosol SOD from chicken liver contained 0.30% copper and 0.25% zinc. This corresponds to 0.9 atom of copper and 0.8 atom of zinc per subunit. It was also shown that this chicken liver Cu, Zn- SOD had a tendency to polymerize [43]. In contrast, the mitochondrial SOD was found in chicken liver to be a manganoprotein which has a molecular weight of 80,000 Da. It is composed of four subunits of equal size, which are not covalently joined. It contains 2.3 atoms of manganese per molecule and is strikingly similar to the SOD previously isolated from bacteria. This supports the theory that mitochondria have evolved from aerobic prokaryotes. In fact, Mn-SOD was first isolated from the chicken liver [43]. The Mn- SOD was found primarily in the mitochondrial matrix space whereas the Cu,Zn-SOD, previously isolated from the cytosol, was found in the intermembrane space [44].

Cu, Zn-SOD was purified from chicken liver with a subunit Mr of 16900 [45]. Low dietary copper was associated with a decrease in SOD activity and when the 10-day-old deficient chicks were injected with 0.5 mol of CuSO4 intraperitoneally, SOD activity in aorta was restored to control levels in about 8 h. Indeed, dietary copper regulates SOD activity in the tissues of young developing animals. The authors also suggested that a copper deficiency suppresses Cu, Zn-SOD activity without inhibiting synthesis or accumulation of the Cu, Zn-SOD protein in this tissue [45]. Interestingly, molecular properties (amino acid composition, molecular mass and subunit composition) of the chicken enzyme was shown to be similar to those of a bovine erythrocyte Cu, Zn SOD [46]. Purified chicken liver Cu, Zn-SOD was confirmed to contain two subunits having Cu and Zn elements with a molecular weight of 16000+/-500 for each [47]. The optimum pH of purified Cu, Zn-SOD was determined to be 8.9. The enzyme was found to have fair thermal stability up to 45 o C at pH 7.4 over a 1-h incubation period. The SOD enzyme was not inhibited by DTT and beta-mercaptoethanol, but inhibited by CN(-) and H2O2 [47]. SOD purified from chicken heart has a molecular weight 31.0 +/- 1.0 kDa and is composed of two equally sized subunits each having 1.1 +/- 0.03 and 0.97 +/- 0.02 atoms of Cu and Zn elements, respectively [48]. The Mn-SOD cDNA in chicken heart was shown to be 1108 bp in length. The molecular weight of the mature peptide was 22 kDa. A comparison of the deduced amino acid sequence with those of the human, rat, C. elegans and D. melanogaster showed that the amino acid homology rates were 82.4%, 84.7%, 62.4%, and 59.3%, respectively [49]. SOD activity in avian tissues depends on many different factors including genetics, nutrition and various stress-related factors. For example, SOD activity in the Jungle Fowl feather melanocytes was shown to be 2- and 4-fold higher than that in Barred Plymouth Rock and White Leghorn tissue respectively [50]. Indeed, understanding the molecular mechanisms of the regulation of SOD gene expression and the factors involved in tissue- and cell-specific expression of the SOD genes are of great importance for a developing novel strategies for preventing negative consequences of various stresses in poultry production.

SOD in chicken embryo

Chick embryo tissues contain a high proportion of highly polyunsaturated fatty acids in the lipid fraction [51] and therefore need antioxidant defense [18]. The antioxidant system of the newly hatched chick includes the antioxidant enzymes SOD, GSH-Px, catalase [52], fat-soluble antioxidants vitamin E and carotenoids [53], water-soluble antioxidants ascorbic acid [53] and glutathione [52] as well as selenium [54-57]. Vitamin E [58], carotenoids [59-64] and selenium [54-57] are transferred from feed into egg and further to embryonic tissues. Glutathione and antioxidant enzymes GSHPx, SOD and catalase are also expressed in the embryonic tissues at various stages of their development [52,65]. Our results indicate that there are tissue-specific features in antioxidant defense strategy during embryonic development of the chicken and SOD plays a crucial role as an integral part of the antioxidant network.

In the embryonic liver, SOD specific activity was maximal at day 11 but decreased sharply by day 15 and remained relatively constant thereafter. By contrast, the specific activity of SOD in the brain from day 15 onwards was approximately 2 times higher than that in the liver. In the YSM SOD specific activity increased gradually between days 10 and 15 and then decreased gradually between day 15 and hatching [52]. The specific activities of SOD in kidney, lung, heart and skeletal muscle all showed a gradual decrease between day 15 and hatching. As can be seen from 2-jadval, the tissues displayed a considerable variation in the Mn-SOD activity, with the heart having the highest value and lung the lowest [65]. By contrast, the lung was characterized by high Cu,Zn-SOD activity in the heart, activity of Cu,Zn-SOD was comparable to the other tissues. Based on the total SOD activity the tissues could be placed in the following descending order: heart > muscle > YSM > kidney > lung > liver. Mn-SOD is the main enzymatic form in the liver and heart comprising 73.2 and 68% of the total SOD activity respectively. In great contrast, in the lung, YSM and thigh muscle, SOD is exclusively represented by Cu,Zn-SOD comprising 98.5, 98.3 and 84.7% of the total SOD activity respectively. In various parts of the brain (cerebrum, cerebellum, brain stem and optic lobes) of the newly hatched chick the Cu,Zn-SOD activity is also almost 2-fold higher than that of Mn-SOD [65]. Notably, in the kidney both SOD forms are equally represented. Furthermore, the tissues differed markedly in the GSH-Px activities. In all the tissues, Sedependent GSH-Px was the main enzymatic form, comprising from 65% (lung) up to 90% (heart) of the total enzyme activity. The liver and kidney displayed the highest total GSH-Px activity and the muscle the lowest. As in the case of GSH-Px, catalase activity was also maximal in the liver and kidney.

To'qimalar Mn-SOD, U/mgprotein Cu-Zn-SOD,U/mg protein Se- GSH-Px,mU/mg protein Non-Se-GSH-Px,mU/mg protein Catalase,U/mg protein
Jigar 3.81a 1.46a 177.0a 114.6a 35.8a
Buyrak 2.98b 3.15b 159.8a 58.6b 29.5a
Yurak 5.79c 2.73b 99.0b 11.6c 5.8b
O'pka 0.09d 5.79c 99.8b 53.0b 6.0b
Thigh Muscle 1.06d 6.07c 45.8c 12.6c 3.2c
YSM 0.12e 6.97c 102.6b 37.7d 15.2d

2 -jadval: Antioxidant Enzyme Activities in the Tissues of a Newly Hatched Chick (Adapted from [65].

SOD in avian semen

Despite the importance of SOD in the protection of cells against lipid peroxidation, its activity in avian semen has received only limited attention. A comparison of SOD activity in sperm from various species including boar, rabbit, stallion, donkey, ram, bull, man and chicken indicated that donkey sperm had the highest and fowl the lowest SOD activity [66]. Furthermore, turkey spermatozoa were found to contain even less SOD activity than fowl spermatozoa [67]. Our data indicate that in seminal plasma of 5 avian species, KCN inhibited 100% of SOD activity, an observation reflecting the presence of only Cu, Zn-SOD [68]. In the seminal plasma, the highest SOD activity was recorded in turkey and guinea fowl while the lowest activity was found in duck. Overall, avian species classified in accordance with decreasing SOD activity (expressed per mg seminal plasma protein) can be placed in the following order: guinea fowl>chicken>goose> duck>turkey. Similarly, in seminal plasma, the activity of GSH-Px was two times greater in the ganders than in chickens, whereas SOD activity was lower than in chickens [69]. In contrast, the SOD activity in spermatozoa, from pre-cited species is classified in an opposite order to that observed in seminal plasma (goose>duck>chicken=guinea fowl>turkey [68]). In chicken semen, the SOD activity significantly increased in cryopreserved seminal plasma with simultaneous decrease of its activity in cells [69]. In sperm both forms of SOD are expressed with significant species-specific differences. For example in goose, Cu,Zn-SOD appears twice higher than Mn- SOD and an opposite distribution between different forms of SOD was recorded in guinea fowl where Mn-SOD was more than two-fold higher compared to Cu,Zn-SOD [68]. In chicken, about 67% of total SOD activity was detected in spermatozoa as compared to 33% in seminal plasma [70]. The biological meaning and physiological consequences of such speciesspecific differences in SOD activity and distribution remain to be established. Notably, in laying hens, SOD activity in the utero-vaginal junction was shown to be increased compared to other regions of the lower oviduct (vagina, uterus [71-72]).

Dietary modulation of SOD

Mn and Cu in the diet

Mn-SOD is shown to be highly expressed in various organs containing a large number of mitochondria such as the heart, liver, and kidneys. Indeed, in comparison to other tissues, the heart has the highest steady state mRNA Mn-SOD expression level in chickens [73]. It has been proven that Mn availability is a regulating factor of Mn-SOD activity. For example, in primary cultured broiler myocardial cells Mn-SOD mRNA, Mn-SOD protein, and Mn-SOD activity were induced by manganese in dose- and time-dependent manner. Manganese regulates Mn- SOD expression not only at transcriptional level but also at translational and/or posttranslational levels [74]. In both heart and kidney, Mn-SOD activity was significantly depressed by decreased dietary manganese greatest reduction occurred in the heart [75]. Decreased heart Mn-SOD and Cu,Zn-SOD activities, resulting from dietary Mn and Cu deficiencies, were both associated with increased peroxidation [76]. It seems likely that Mn-SOD activity is very sensitive to dietary Mn levels in commercial corn-soybean meal diets. In fact, Mn deficiency in growing chickens caused the reductions of Mn concentrations of the liver and heart as well as Mn-SOD activity of the heart [77]. In chickens, dietary Mn contents required to reach the plateau of Mn concentrations of the liver, pancreas, kidney, heart, spleen and muscle and to obtain the maximum Mn-SOD activity of heart were calculated to be 110, 111, 141, 123, 109, 99 and 121ppm respectively. Interestingly, Mn-SOD of liver and pancreas were not affected. Therefore, for broilers fed the basal corn-soybean meal diet, 120ppm Mn was suggested as the required level [78] which corresponds to the presently recommended levels of Mn supplementation. Chickens fed a Mn-deficient diet from hatching had significantly lower levels of Mn-SOD activity in liver than did controls. However, activity of the Cu,Zn-SOD in the liver was higher in Mn-deficient chickens than in controls [79]. The activity of both forms of SOD reached normal levels when a Mn-supplemented (1,000 ppm) diet was fed to deficient chickens, but the activity of the manganese enzyme was not affected by feeding the supplemented diet to manganese sufficient chickens. It was shown that heart Mn- SOD activity and heart Mn-SOD mRNA levels increased linearly as dietary Mn levels increased, confirming that dietary Mn significantly affected heart Mn-SOD gene transcription [80]. Furthermore, birds fed supplemental Mn had lower MDA content in leg muscle and greater Mn-SOD activities and Mn- SOD mRNA level in breast or leg muscle than those fed the control diet [81]. Compared with control chickens fed on a diet without Mn supplementation, chickens fed Mn-supplemented diets had higher Mn concentrations, Mn-SOD mRNA levels, Mn-SOD protein concentrations, and Mn-SOD activities within heart tissue [82-83]. Therefore, dietary Mn can activate Mn- SOD gene expression at both the transcriptional and translational levels [82]. However, Mn excess can be toxic for birds. In fact the activities of SOD and GSH-Px in chicken serum and immune organs (spleen, thymus, and bursa of Fabricius [84]) and testes [85] were decreased due to Mn dietary excess.

It seems likely that dietary Cu is involved in regulation of the SOD activity and in the case of low Cu levels in the basic diet, it is possible to upregulate Cu,Zn-SOD in chickens by dietary Cu supplementation. For example, in the basal low-Cu group, Cu, Zn-SOD activity decreased in the liver, RBC and heart to 14, 25, and 61%, respectively, of control activities after 6 weeks' depletion [86]. On the other hand, Cu,Zn-SOD activity in chicken erythrocytes from the Cu- and vitamin Csupplemented birds was increased by 39 and 20% respectively [87]. Similarly, in the Cu-supplemented chickens, Cu,Zn-SOD activity in the liver, erythrocyte, kidney and heart significantly increased by 75, 40, 12, 12% respectively. Furthermore, Mn- SOD activity in the heart, liver, kidney and brain of the vitamin C &ndashsupplemented chickens was increased. In addition, in the heart of Cu-supplemented chickens Mn-SOD was found to be increased by approximately 15%, while in liver tissue of the Cusupplemented group it was reduced by 19% [88]. However, in an earlier study, hepatic Mn-SOD and Cu,Zn-SOD were not influenced by dietary Cu level or source or LPS in broiler chicks [89] probably reflecting differences in the background Cu levels.

Vitamins, carnitine and amino acids

Dietary vitamin A excess was shown to decrease SOD activity in the chicken liver and brain [90]. Similarly, increased vitamin E supplementation (40-60 mg/kg) or CCl4 injection decreased the activity of SOD in the chicken blood [91]. However, in a recent study a higher vitamin E level (60 vs 30 mg/kg) significantly increased alpha-tocopherol concentrations and SOD activity in serum of laying hens [92]. Initially, L-Carnitine dietary supplementation was shown to increase blood SOD activity in chickens [93]. Furthermore, when chicken fed corn-soybean diets supplemented with different doses of lipoic acid SOD activity in serum (300 mg/ kg), liver (100, 200 and 300 mg/kg) and leg muscle (200 or 300 mg/kg) was significantly increased [94]. It was shown that increased Lipoic acid (LA) or acetyl-l-carnitine (ALC) resulted in increased total antioxidant capacity and SOD and GSH-Px activities and decreased levels of MDA in serum and liver of birds [95]. Notably, birds fed diets ?ontaining 50 mg/kg of LA and 50 mg/kg of ALC had higher serum and liver SOD activities than those fed diets containing 100 mg/kg of LA or ALC alone. In laying hens reared in a hot and humid climate L-threonine supplementation at 0.2% maximised the SOD activity in both serum and liver [96]. Serum SOD increased linearly and quadratically in laying hens receiving excess dietary tryptophan (0·4 g/kg) [97]. Broilers given a diet containing 5.9 g/kg methionine had enhanced serum SOD activity and decreased hepatic MDA content at day 7 [98].

Low-Se diet caused a significant decrease in the activities of SOD and GSH-Px, and an increased MDA content in thymus, spleen, Bursa of Fabricius and serum [99]. Interestingly, not only Se deficiency (0.03 mg Se per kg of diet) but also Se excess (3 mg/kg) in chickens significantly lowered SOD and CAT activities in the liver and serum [100]. It seems likely that SOD in adult birds is also affected by Se status. For example, laying hens fed the Se-supplemented diet showed higher SOD and GSH-Px activity and lower MDA content in plasma compared with those fed the control (non-supplemented) diet [101]. Positive effects of dietary Se on SOD activities in avian species depend not only on Se concentration, but also on the form of Se used, with organic Se being more effective than sodium selenite. In fact, the activities of serum GSH-Px, SOD and total antioxidant capacity were significantly higher in selenium yeast than sodium selenite-fed chickens [102]. Similarly, dietary Se-Met significantly elevated T-AOC, GPX, T-SOD, CAT activities, contents of GSH and reduced carbonyl protein content in chicken breast muscle [103]. It was shown that dietary organic Se significantly increased the Se content and the activities of CAT and SOD, but decreased the MDA content in chicken breast muscle at 42 days of age [104].

Phytochemicals

Polyphenolic compounds and various plant extracts have received substantial attention as an important means of decreasing oxidative stress in vitro and in vivo. For example, in cultured muscle cells of embryonic broilers, pretreatment with low-dosage phytoestrogen equol (1&muM) restored altered (decreased) by H2O2 intracellular SOD activity. However, pretreatment with high-dosage equol (10 and 100 &muM) showed a synergistic effect with H2O2 in inducing cell damage, but had no effect on MDA content, SOD or GSH-Px activity [105]. Similarly, in chicken HD11 macrophages challenged with LPS activity of SOD increased in cells treated with the higher concentration of equol (80 &mumol/L or 160 &mumol/L, but not in 10, 20 or 40 &mumol/L groups [106]). In a chicken erythrocyte model both curcumin and cyanidin-3-rutinoside were shown to significantly attenuate apoptosis and hemolysis, decreasing MDA content, and increasing SOD activity in a time- and dosedependent manner [107]. Similarly, feeding diets with added flavonoids (hesperetin and naringenin) to laying hens increased the blood serum SOD activity [108]. There was a significant increase in the activities of SOD chicken blood due to Brahma Rasayana supplementation [109]. Dietary xanthophyll (lutein+zeaxanthin) supplementation (20 or 40 mg/kg) for 3 or 4 weeks was shown to increase serum SOD activity in chickens [110]. However, the SOD activity was not affected in the chicken liver or jejunal mucosa. Inclusion into the chicken diet of polysavone (1·5 g/kg), a natural extract from alfalfa, for 6 weeks increased serum and liver SOD activity, while breast muscle SOD activity at 6 weeks of age were significantly higher and MDA content was significantly lower in 1·0 and 1·5 g/kg polysavone groups than in the control group [111]. Notably, effects of plant extracts added to chicken diets on the SOD activity would depend on many factors including polyphenol composition, concentration and bioavailability. In fact, low availability of polyphenolic compounds for growing chickens, breeders and layers [112] is an important limiting factor of their biological efficacy and nutritive value. For example, there was no effect of dietary turmeric rhizome powder (0.25- 0.75%) on the activities of GSH-Px and SOD in thigh muscle [113] or serum [114]. Feeding to broiler chicks diets enriched with selected herbal supplements failed to affect the growth performance of chickens at 42 days of age. In addition, this supplementation had no influence on the activities of SOD and GSH-Px, concentration of vitamin A and selected lipid metabolism indices [115].

Sod up- and down-regulation in stress conditions

Heat stress

High environmental temperature is one of the most important stressors causing economic losses to the poultry industry, including poor growth performance, immunosuppression, high mortality, decreased reproductive performance and deterioration of meat quality [116]. Since SOD is an inducible enzyme, depending on conditions, stresses can tissue-specifically increase or decrease SOD activity in various avian species. For example, acute heat stress (34°C) in chickens was shown to induce a significant production of ROS, and antioxidant enzymes, including SOD, CAT and GSH-Px [117]. On exposure to chronic heat stress, GSH-Px activity remained relatively constant, though a temperaturedependent elevation in Cu,Zn-SOD activity was observed in skeletal muscle of broiler chickens [118]. Chicken exposure to heat stress increased SOD activity and MDA levels in skeletal muscle and vitamin E or vitamin E+Se dietary supplementation further enhanced SOD activity in muscles in heat-stressed birds [119]. In broiler chickens, plasma activity of SOD was increased, whereas GSH-Px was suppressed by heat stress (32 ± 1°C). Furthermore, heat exposure increased SOD and catalase activities in breast muscle but the reverse was true in thigh muscle. On the other hand, heat stress increased SOD and decreased GSH-Px activities of mitochondria regardless of muscle types [120]. Interestingly, in restrictedly fed broiler breeder&rsquos plasma MDA, protein carbonyl content, activity of SOD and corticosterone content were not altered after acute (33°C) and prolonged heat challenges [121]. Probably the stress intensity was not high enough to upregulate SOD. On the other hand, if stress is too high adaptive functions of SOD can be overwhelmed with the following SOD decrease. For example, heat stress in black-boned chickens reduced daily feed intake and BW gain decreased serum GSH and inhibited GSH-Px, SOD and CAT activities compared with birds subjected to thermo-neutral circumstances [122]. Similarly, in chickens heat stress induced higher levels of TNF-&alpha, IL-4, HSP27, HSP70, and MDA levels but lower level of IFN-&gamma, IL-2, GSH-Px, and SOD in spleen [123-124]. These responses were ameliorated by the treatment of Se, polysaccharide of Atractylodes macrocephala Koidz alone or in combination [124].

Cold stress

Environmental temperature either below or above the comfort zone causes discomfort in avian species. In fact, the increase in metabolic rate at temperatures below the comfort zone (cold stress) is a significant cause of increased mortality from the pulmonary hypertension syndrome (ascites) in broilers [125]. Initially, it was shown that when broilers were exposed to a cool environment for 3 weeks, plasma SOD activity was decreased [126]. Similarly, cold exposure reduced chicken plasma SOD and supplemental L-carnitine (100 mg/kg) was shown to restore the SOD activity in cold-stressed birds [127]. Broilers with cold-induced ascites were characterised by a significantly decreased SOD activity in the liver [128]. Opposite results were also reported. In fact, during acute cold stress, the SOD activity of the lung increased compared with their control group at each stress time point [129]. Similarly, there was a significant decrease in CAT and SOD in blood, but increased SOD activity was evident in the liver [130]. A complexity of the SOD response to various stresses is also illustrated in the next two papers. In chick duodenum, under acute cold stress MDA level increased and the activity of SOD and iNOS first increased and then decreased. In contrast, under chronic cold stress the activity of SOD, NO, and NOS in duodenum first decreased and then increased, whereas the MDA level increased [131]. In immune organs, the activities of SOD and GSH-Px were first increased then decreased, and activity of total antioxidant capacity was significantly decreased at the acute cold stress in chicks [132].

Other environmental stresses

Effects of environmental stresses on SOD activity is, probably, tissue-specific and depend on many factors, including strength and duration of the stress. For example, in broilers corticosterone administration caused decreases in serum SOD activity as well as in the apparent digestibility of energy, relative weight of bursa and thymus, total antioxidant capacity, and antibody titers to Newcastle disease virus [133]. In contrast, there was an increase in SOD activity in the chicken heart during short-term corticosterone administration [134]. In growing chickens exposed to high ammonia and low humidity blood antioxidative capacities and pectoral muscle SOD and GSH-Px activities were significantly reduced [135]. Hepatic mitochondrial SOD activity decreased at 14 d in feedrestricted broiler chicks [136]. However, the plasma SOD activity of feed-restricted birds was markedly higher than those fed ad libitum on d 35 and d 42 [126].

Toxicological stresses

Administration of cadmium to chickens decreased SOD activities in various tissues, including liver [137-138], kidney [139], blood [140], ovary [141], testes [142] and splenic lymphocytes in vitro [143]. Usually, decreased SOD activity was accompanied by decreased GSH-Px activity and increased lipid peroxidation in the same tissues. In contrast to the aforementioned results, Cd oral administration produced peroxidative damage in chickens, as indicated by increase in TBARS, reduction in GSH concentration in liver and kidney, but increased CAT and SOD activities were observed in erythrocytes [144]. Dietary nickel chloride is also shown to have a negative effect on SOD and other antioxidant enzymes (GSH-Px and CAT) in the intestine [145], cecal tonsil [146] or splenocytes [147]. Similarly, vanadium inhibited SOD activity in chicken liver and kidney [148]. The list of chicken SOD inhibitors includes aluminium [149-150], fluorine [151], polychlorinated biphenyls [152-153], 4-nitrophenol [154], dioxin [155], organophosphate [156], thiram [157], furazolidone [158], valproic acid [159], oxidised oil [160]. It seems likely that mycotoxins can also decrease SOD activity in various chicken tissues. In particular, DON decreased SOD activity in embryo fibroblast DF-1 cells [161] and AFB1 feed contamination was associated with decreased SOD in the chicken liver [162-163] and erythrocytes [164]. However, the activities of SOD, GST and non-protein thiol levels in the chicken liver were not altered by the FB1-containing (100 mg/kg) diet fed for 21 days [165].

Diseases and gut health

Various avian diseases also negatively affect antioxidant defenses including decrease SOD activity in jejunal and ileal parts of the gut challenged with Salmonella pullorum [166], brain and liver of Newcastle disease virus-infected chickens [167], erythrocytes of the Eimeria acervulina infected birds [168] and plasma of E. tenella challenged birds [169]. Since antioxidant-pro-oxidant balance in the gut plays an important role in chicken health and immunity [5], special emphasis should be given to this area of research. For example, in vitamin-D-replete chicks, Cu,Zn-SOD was shown to be associated with the apical border (microvilli) of the duodenal absorptive cells [170]. Furthermore, inclusion of &gamma- aminobutyric acid (GABA) in laying hen diet was associated with significant increasing the activity of SOD and GSH-Px and decreasing MDA levels in serum [171]. Similarly, serum SOD and catalase activities were significantly increased, and MDA was decreased by dietary sodium butyrate at 0.5 or 1.0 g/kg feeding to chickens from hatch for 21 days [172]. Broilers fed a diet supplemented with 1×10 9 cfu Clostridium butyricum/kg diet had greater SOD activity in the ileal mucosa on d21 and in jejunal mucosa on d42 than those in the other groups fed antibiotic aureomycin or lower doses of the probiotic [173].

Clinical significance of SOD activity in different tissues

When studying SOD, results interpretation could be a challenging task. First of all, plasma is easily obtained material however, the meaning of increased or decreased total SOD in plasma sometimes could be misleading. Indeed, in normal human plasma three forms of SOD are found with the lowest amount of SOD1 (5.6-35.5 ng/ml), somehow higher amount of SOD2 (47-150 ng/ml) and even more SOD3 (79-230 ng/ml [174]). Therefore, ideally individual SODs should be determined in plasma to have maximum information to analyse. However, practically in all studies related to SOD in avian plasma only total SOD was determined. Secondly, in tissues Mn-SOD and Cu,Zn-SOD should be distinguished. However, similar to plasma SOD, in most of poultry-related studies only total SOD was analysed. Thirdly, since Mn-SOD is an inducible enzyme, an increased SOD activity in tissues could mean an adaptive response to stress situation or could indicate a potential of the antioxidant defense in the stress conditions. Indeed, when natural antioxidants are supplemented with diets there could be upregulation of SOD indicating an increase in antioxidant defenses or downregulation of SOD reflecting a decreased need for SOD because of other antioxidant mechanisms are increased. However, as mentioned above SOD is the main enzyme dealing with superoxide production in mitochondria, a primary site of ROS formation, and most likely it cannot be replaced by other antioxidants. Furthermore, when stress is too strong there is a decrease in SOD activity indicating that the antioxidant defense network was overwhelmed by increased production of free radicals and the body is not able to adequately adapt to the situation. Clearly, there is a need for additional research on individual forms of SOD in avian species with specific emphasis to various transcription factors, including NF-&kappaB and Nrf2, responsible for or involved in SOD activation in stress conditions.

In general, the free radical-initiated oxidative damage of lipids, proteins, and DNA as part of the unspecific immune response caused by some viral (Marek&rsquos disease, Newcastle diseases, or infectious bursal disease), bacterial diseases (Salmonella, Staphylococcus, Clostridium, or E. coli), or parasitic infections (coccidiosis) has been recently reviewed [175]. Indeed, roles of superoxide production and SOD activity in many of those diseases in poultry await investigations. In fact, it has been suggested that oxidative damage may regulate the occurrence and development of avian infectious bronchitis and SOD activity in the serum of chickens inoculated with infectious bronchitis virus significantly decreased [176]. Similarly, blood SOD was shown to be significantly decreased in broiler birds infected with Eimeria tenella [177].

Nutritional modulation of vitagenes

The aforementioned data clearly indicate that vitagenes can be modulated by nutritional means. Indeed, vitamins E, A, carnitine, selenium and some phytochemicals can affect SOD expression and concentration in various stress conditions. It is interesting that the same compounds can affect other vitagenes, namely thioredoxins, sirtuins and heat shock proteins [2,178]. Therefore, it would be of considerable interest to develop an antioxidant-based composition/ supplement for decreasing negative consequences of various stresses in poultry and pig production. Such a composition should meet at least five important requirements [1-2]:

Vitagene activation and redox-signaling (carnitine, betaine, vitamins A, E, D, C, Se, Zn, Mn, silymarin and possibly other phytochemicals)

Maintenance of the vitamin E recycling system (vitamin C, Se, Vitamin B1 and B2)

Provision of nutrients required for carnitine synthesis (lysine and methionine, ascorbic acid, vitamin B6 and niacin)

Supporting the liver, a main site of T-2 toxin, ochratoxins, fumonisins and aflatoxins detoxification and gut, responsible to DON detoxification (vitamins E and C, selenium, carnitine, betaine, organic acids, methionine and lysine)

Possessing immunomodulating properties (vitamins A, E, D, C, carnitine, Se, Zn and Mn).

Inclusion of various protective compounds into the diet of farm animals and poultry to decrease negative consequences of stress conditions is quite complicated, firstly, by a decreased feed consumption at time of stress. Secondly, such an approach has a low flexibility, since existing feeding systems do not allow to include anything into the feed loaded into the feed storage bins located near the poultry/pig house (usually several tons of feed for several days feeding). Therefore, before the previous feed is consumed, nothing can be added to the feed. However, sometimes it is necessary to supplement animals/poultry with specific additives very quickly to deal with consequences of unexpected stresses (e.g. mycotoxins in the feed, immunosuppression, high temperature, etc.). In such a case, additive supplementation via drinking system is a valuable option [178]. In fact, modern commercial poultry and pig houses have water medication equipment installed, which can be perfectly used for the aforementioned supplementations. For example, an attempt to address the aforementioned option was implemented in a commercial product PerforMax, containing a vitagene-regulating mixture of 28 compounds, including antioxidants (vitamins E and C), carnitine, betaine, minerals (Zn and Mn) and essential amino acids, and supplied via drinking water. Its efficacy in fighting stresses in commercial poultry production has been recently reviewed [4] and prospects of its use to maintain gut health in weaned piglets and newly hatched chicks was considered [5]. Indeed, it is well known that commercial animal/poultry production is associated with a range of stress conditions including environmental (high temperature), nutritional (mycotoxins and oxidized fat) or internal (vaccinations, disease challenges, etc.) stresses [4,19-20]. In such conditions, supplying the PerforMax with drinking water was shown to have protective effects in growing birds [179-180] as well as in adult birds [4] helping maintain their health, productive and reproductive performance. Therefore, the aforementioned results are the first step to go from the development of the vitagene concept to designing a commercial product and testing it in the commercial conditions of poultry and pig production. We can suggest that this idea could be realized in human nutrition as well. Clearly more research is needed to understand a fundamental role of vitagenes in adaptation to various stresses.

Conclusions and future directions

From the aforementioned analysis of the data related to SOD in poultry physiology and adaptation to stresses it is possible to conclude:

SOD as important vitagene is the main driving force in cell/ body adaptation to various stress conditions. Indeed, in stress conditions additional synthesis of SOD is an adaptive mechanism to decrease ROS formation

If the stress is too high SOD activity is decreased and apoptosis is activated

There are tissue-specific differences in SOD expression which also depends on the strength of such stress-factors as heat, heavy metals, mycotoxins and other toxicants

SOD is shown to provide an effective protection against lipid peroxidation in chicken embryonic tissues and in semen

SOD is proven to be protective in heat and cold stress, toxicity stress as well as in other oxidative stress-related conditions in poultry production

There are complex interactions inside the antioxidant network of the cell/body to ensure an effective maintenance of homeostasis in stress conditions. Indeed, in many cases nutritional antioxidants (vitamin E, selenium, phytochemicals, etc.) in the feed can increase SOD expression

Regulating effects of various phytochemicals on HSPs need further investigation

Nutritional means of additional SOD upregulation in stress conditions of poultry production and physiological and commercial consequences await investigation. Indeed, in medical sciences manipulation of SOD expression and usage of SOD mimics are considered as an important approach in disease prevention and treatment

Vitagene upregulation in stress conditions is emerging as an effective means for stress management.


Supporting information

S1 Fig. Phylogenetic inference of West Nile virus using a maximum-likelihood tree.

The Shimodaira-Hasegawa values greater than 70% are shown at respective nodes. Tip labels are colored by proposed lineage. Sequences from Table 1 are labeled.

S2 Fig. Selection regimens acting on codons of West Nile Virus polyprotein via FUBAR method.

The dashed line marks neutral selection (dN-dS = 0), points above the line (dN>dS) are under diversifying selection and below (dN<dS) are under purifying selection. The intensity of the point color is proportional to the posterior probability to observe that codon under the selection regimen, calculated with Fubar method.

S3 Fig. Selection regimens acting on codons of West Nile Virus polyprotein via MEME method.

Using 95 WNV sequences, A) diversifying selection (dN>dS) and B) purifying selection (dN<dS) were estimated. The intensity of the point color is proportional to the posterior probability to observe that codon under the selection regimen, calculated with MEME method. Significant positively selected sites detected by other methods were also included in A).

S1 Table. Raw data for FUBAR analysis.

S2 Table. Raw data for MEME analysis.

S3 Table. List of primers used for sequencing.

The NS5, envelope and NS5-partial 3ā€™UTR regions were first amplified using flavivirus consensus or West Nile specific primers. This was followed by amplification of NS3 region using designed WNV primers. Finally, specific primers were designed according to the first sequences obtained and a second step of RT-PCR was done to obtain the complete genome.

S1 Dataset. Raw growth kinetics data.

S2 Dataset. Raw mice survival data.



Izohlar:

  1. Mahoyu

    Xayrli tong Hamma! Bu menga tabassum qildi !!!!

  2. Amell

    Qaysi nozik mavzu

  3. Kalman

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  4. L'angley

    Sizning fikringiz foydali

  5. Khamisi

    Ayol ko'p narsani xohlaydi, lekin bir erkakdan, erkak esa bir narsani xohlaydi, lekin ko'p ayollardan. Sizda bitta yaxshi narsa bor: bu dumbani dumbagacha ajratadi. Tez-tez ayol Chekish zararli, ichkilik ichish jirkanch, ammo sog'lom o'lish achinarli Metro poyezdidagi to'xtash klapan ostidagi yozuv: Agar borishga dangasa bo'lsangiz, bu jinnini torting. Biz universitetlarni tugatmadik !!! Birovning og'ziga shimingizning tugmalarini yechmang! Win95 samolyotga o'xshaydi - kasal, lekin boradigan joy yo'q! Fenita jinni komediya

  6. Samukus

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  7. Val

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  8. Cohen

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  9. Nern

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