Biochemistry and Nutrition, Poultry Research Institute, Borky, Kharkov Region, Ukraine, 313410. Avian embryonic tissues are characterised by the accumulation ...
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PHYSIOLOGY, BIOCHEMISTRY AND NEUROBIOLOGY
double yolked eggs (9·50 g/kg) was larger than in single yolked eggs (7·57 g/kg). In addition, the proportion of yolk in single yolked eggs was, as might have been expected from the egg weight data, closely associated with the logarithm of body weight at 1st egg (Table). Yolk proportion in double yolked eggs was not signi cantly correlated with body weight.
HUSSEIN, S.M., HARMS, R.H. & JANKY, D.M. (1993) Effect of age on the yolk to albumen ratio in the chicken egg. Poultry Science , 72: 594–597. MARCH, B.E. & MACMILLAN , C. (1990) Linoleic acid as a mediator of egg size. Poultry Science , 69: 634–639. LEWIS, P.D., PERRY, G.C. & MORRIS, T.R. (1994) Effect of breed, age and body weight at sexual maturity on egg weight. British Poultry Science , 35: 181–182.
Lipid peroxidation and the antioxidant system of the brain of developing chicken embryo P. F. SURAI1, S. N. LISENKO 1, B. K. SPEAKE, R. C. NOBLE
AND
N. H. C. SPARKS
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Department of Biochemistry and Nutrition, SAC, Auchincruive, Ayr KA6 5HW, Scotland and 1Department of Physiology, Biochemistry and Nutrition, Poultry Research Institute, Borky, Kharkov Region, Ukraine, 313410
Avian embryonic tissues are characterised by the accumulation of polyunsaturated lipids during the last week of in ovo development (Noble and Speake, 1997). The brain differs from other tissues in being a highly aerobic and totally oxygen-dependent tissue and may be especially at risk from free radical attack, because this tissue is characterised by a low content of natural antioxidants (Surai et al., 1996) and generates a greater amount of free radicals per gram of tissue than any other organ (Reiter, 1995). One consequence of these features is the development of encephalomalacia, a recognised clinical consequence of alpha-tocopherol de ciency during chick development, characterised by peroxidative damage to the cerebellum (Dror et al. , 1976). The aim of this study was to investigate the susceptibility of the chick embryo brain to peroxidation and to determine the antioxidant pro le of the cerebellum and other brain regions. Batches of fertile eggs (Ross 1 strain) were obtained from commercial hatcheries. The eggs were incubated at 37·8° C and 60% humidity in a forced draught incubator with automatic egg turning. Five embryos or chicks at each stage were killed and the brain and other tissues were dissected and used for the analysis. Four regions of the brain (cerebrum, cerebellum, optic lobes and stem) were collected. Vitamin E was determined by HPLC, vitamin C and glutathione by spectrophotometry and enzymatic activities by commercial kit systems. Brain tissue obtained from embryos at 16
to 22 d of incubation was characterised by low concentrations of malondialdehyde (MDA) in the fresh tissue but by a very high susceptibility to spontaneous and Fe-stimulated lipid peroxidation. The antioxidant pro les of the different brain regions of 1-d-old chicks are depicted in the Table, and show a signi cant difference in antioxidants between the regions. The cerebellum contained more a -tocopherol but less ascorbic acid compared to the cerebrum. The cerebellum was also characterised by greater catalase activity but a lower activity of mitochondrial Mn-SOD than the cerebrum. Because mitochondria are the main source of superoxide radical in biological systems, the low Mn-SOD activity might be a risk factor with regard to encephalomalacia development. The low concentration of vitamin E in the various regions provides effective protection against lipid peroxidation under physiological conditions because the level of MDA in fresh tissue was negligible. Protection is presumably provided by the recycling of alpha-tocopherol by the action of ascorbic acid, present at high concentration in the brain. Thus the lower ascorbic acid concentration in the cerebellum may predispose to encephalomalacia. The chick embryo had signi cantly more vitamin E in the cerebellum than in the cerebrum. Preliminary results from turkey embryos indicate the same difference between these 2 regions of the embryo brains. Comparing antioxidant concentrations in the
Table. Antioxidant proles of the chick embryo brain Antioxidants
Cerebrum
a -tocopherol (m g/g) Ascorbic acid (m g/g) Glutathione (nmol/mg protein) Mn-SOD (U/mg protein) Se-GSH-Px (mU/mg protein) Catalase (U/mg protein) *P , 0·05; **P ,
0·01.
5·22 6 889·4 6 41·12 6 3·66 6 29·83 6 1·82 6
0·32 41·2 3·22 0·29 1·77 0·11
Cerebellum 7·12 6 711·3 6 38·12 6 2·84 6 28·61 6 2·37 6
0·29** 51·2** 2·88 0·22** 2·33 0·2*
Brain stem 6·12 6 747·72 6 40·13 6 3·91 6 33·14 6 1·97 6
0·38 61·4 4·12 0·29 3·99 0·14
Optic lobes 5·66 6 850·53 6 39·56 6 3·02 6 32·60 6 1·82 6
0·41 66·4 3·22 0·21 2·44 0·15
PHYSIOLOGY, BIOCHEMISTRY AND NEUROBIOLOGY
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embryo brain with other tissues showed that the brain contained low concentrations of vitamin E, glutathione and low glutathione peroxidase and catalase activities. Thus the highly unsaturated brain tissue will be susceptible to peroxidation in stress conditions. Incubation of chicken or turkey embryo brain homogenates at 37° C produced high concentration of MDA as a result of lipid peroxidation. Our previous data demonstrate a linear relationship between the alpha-tocopherol concentration in the yolk and subsequent concentrations in the brain (Surai et al., 1997). Because the amount of vitamin E in the egg yolk re ects the amount in the food (Surai et al., 1995) vitamin E in the maternal diet is the major factor regulating the antioxidant system of the chick embryo brain providing protection against nutritional encephalomalacia.
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DROR, Y., BUDOWSKI, P., BUBIS, J.J., SANBANK , U. & WOLMAN, M. (1976) Chick nutritional encephalopathy induced by diets rich in oxidised oil and de cient in a -tocopherol. Progress in Neuropathology , 3: 343–357. NOBLE, R.C. & SPEAKE, B.K. (1997) Observations on fatty acid uptake and utilization by avian embryo. Prenatal and Neonatal Medicine , 2: 92–100. REITER, R.J. (1995) Oxidative processes and antioxidant defence mechanisms in the ageing brain. FASEB Journal , 9: 526–533. SURAI, P.F., GAAL, T., NOBLE, R.C. & SPEAKE, B.K. (1997) The relationship between the a -tocopherol content of the yolk and its accumulation in the tissues of the newly hatched chick. Journal of Science and Food Agriculture , 75: 212–216. SURAI, P.F., IONOV, I.A., BUZHIN, A. & BUZHINA , N. (1995) Vitamin E and egg quality. Proceedings of the 6th European Symposium on the quality of egg and egg products , Zaragoza, Spain, pp. 387– 394. SURAI, P.F., NOBLE, R.C. & SPEAKE, B.K. (1996) Tissue-speci c differences in antioxidant distribution and susceptibility to lipid peroxidation during development of the chick embryo. Biochemica, Biophysica Acta. 1304: 1–10.
Lipid peroxidation in avian semen: protective effect of seminal plasma P. F. SURAI1, G. J. WISHART2, A. MALDJIAN, R. C. NOBLE
AND
N. H. C. SPARKS
Department of Biochemistry and Nutrition, SAC, Auchincruive, Ayr KA6 5HW, Scotland, 1 Department of Physiology, Biochemistry and Nutrition, Poultry Research Institute, Borky, Kharkov Region, Ukraine, 313410, and 2 Avian Reproduction Group, University of Abertay Dundee, Bell Street, Dundee DD1 1HG, Scotland
Avian spermatozoa are characterised by comparatively high concentrations of 20:4n–6 and 22: 4n–6 fatty acids within their phospholipids (Surai et al. , 1998b) and are susceptible to lipid peroxidation (Surai et al. , 1997) which is considered to be a problem during sperm storage (Cecil and Bakst, 1993). There is evidence that seminal plasma can protect chicken spermatozoa against peroxidation (Fujihara and Koga, 1984; Cecil and Bakst, 1993). Our previous observations indicate that seminal plasma possesses free radical-trapping activity and expresses superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activity (Surai et al. , 1998). The free radical trapping activity of the seminal plasma was twice that of blood plasma and did not change after plasma boiling or storage during 24 h at 20°C. (Surai et al., 1998a). The precise mechanisms of the protective effect of avian seminal plasma against lipid peroxidation are not known. The aim of the present study was to investigate the protective effect of chicken and turkey seminal plasma against lipid peroxidation in an in vitro model system. The model system consisted of 0·5 ml of turkey embryo brain homogenate (10% in phosphate buffer, 0·05 M pH 7·4 containing 1·15% KCl) mixed with different volumes of seminal or blood plasma and the volume was made up to 1 ml with the same buffer. After 1 h incubation at 37°C
without an initiator of peroxidation (spontaneous lipid peroxidation) or in the presence of 0·1 mM of Fe2 1 the accumulation of malondialdehyde (MDA) was determined (Surai et al., 1997). The results (Table) indicate that chicken seminal plasma inhibited spontaneous lipid peroxidation in the model system in a concentrationdependent manner. On the other hand, turkey seminal plasma at low concentration (5%) possessed antioxidant activity which was more than 5 times higher compared to chicken seminal plasma. The data are in agreement with our previous observations, indicating higher free radical trapping activity of the turkey seminal plasma compared to chicken (Surai et al. , 1998b). The increase of turkey seminal plasma volume in incubation medium up to 10% was associated with further Table. Inhibition of spontaneous lipid peroxidation by seminal plasma or blood plasma , (%) Addition of plasma in the medium, (m l) 50 100 200 500
Chicken seminal plasma 12·2 6 21·0 6 42·7 6 84·1 6
1·2 2·5 5·1 8·1
Turkey seminal plasma 64·8 6 6·3** 82·7 6 7·1** 78·8 6 7·9** –
Chicken blood plasma 69·1 6 57·1 6 45·5 6 0·8 6
6·8** 4·9** 5·5 0·09**
Signi cance of differences compared to the chicken seminal plasma: **P , 0·01.
