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1. Birds have been proposed as a suitable model for studies on ageing because of their long life in comparison with similar-sized mammals. However, some weak fliers, such as Galliformes, are the exception to this rule. The aim of the present study was to determine the effects of the treatment with rooibos tea (Aspalathus linearis), a natural source of flavonoid antioxidants and compounds with phyto-oestrogenic activity, on postnatal development and egg production of aged Japanese quail (Coturnix coturnix japonica). 2. Substitution of drinking water with traditional rooibos tea or diet supplementation with ground rooibos tea affected body weight of Japanese quail up to 100 d of age. The body weight of males drinking rooibos tea or eating rooibos-supplemented food decreased significantly. There was a trend toward increased body weight of tea drinking females and a significant increase in the body weight of hens fed the rooibos-supplemented diet. Although rooibos treatment did not significantly increase egg production in young hens, the decrease in egg production of rooibos-treated aged hens (360 d of age) was significantly reduced, regardless of the egg production levels (high - 80%; low - 20%) before the treatment. 3. The results suggest that treatment with rooibos tea positively affected body weight and egg production in quail hens and prolonged the productive period of aged animals. Further studies would be needed to address the question whether these effects are due to the antioxidant or phyto-oestrogenic activities of rooibos.

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The discovery of hormone leptin has led to better understanding of the energy balance control. In addition to its effects on food intake and energy expenditure, leptin has now been implicated as a mediator of diverse physiological functions. Recently, leptin has been cloned in several domestic species. The sequence similarity suggests a common function or mechanism of this peptide hormone across species. Leptin receptors are expressed in most of tissues, which is consistent with the multiplicity of leptin functions. The main goal of this review was to summarize knowledge about effect of leptin on physiology of farm animals. Experiments point to a stimulatory action of leptin on growth hormone (GH) secretion, normal growth and development of the brain. Surprisingly, leptin is synthesized at a high rate in placenta and may function as a growth factor for fetus, signalling the nutritional status from the mother to her offspring. Maturation of reproductive system can be stimulated by leptin administration. Morphological and hormonal changes, consistent with a major role of leptin in the reproductive system, have also been described, including the stimulation of the release of luteinizing hormone (LH), follicle-stimulating hormone (FSH) and prolactin. Leptin has a substantial effect on food intake and feeding behaviour in animals. Administration of leptin reduces food intake. Its level decrease within hours after initiation of fasting. Leptin also serves as a mediator of the adaptation to fasting, and this role may be the primary function for which was the molecule evolved.

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Potential changes in the activity of endocrine axes related to growth as a result of leptin administration during embryonic development of birds were evaluated in the Japanese quail as a model bird with fast growth and development. On day 5 of incubation, 0.1 microg or 1 microg of recombinant mice leptin in 50 microl of phosphate buffered saline were injected into the albumen of eggs. Animals from each group were killed by decapitation on day 0, 2, 5, 7, 14, 21, 28, 35, 42, 49 and 56 of life. Plasma concentrations of triiodothyronine (T(3)), thyroxin (T(4)), corticosterone, testosterone, total lipids, triacylglycerols, cholesterol, glucose and alkaline phosphatase activity were measured. Quail treated by leptin hatched earlier (5-24 hours) and had a higher body weight than the control group (P<0.05-0.001). Mean body weight across the whole observed period was higher in both treated groups as compared to the control group (P<0.05). Leptin in ovo administration was accompanied by changes of endocrine and metabolic parameters during postembryonic development. The most prominent changes appeared immediately after hatching (T(3), T(4), total lipids, triacylglycerols) and before sexual maturity. It is suggested that leptin acts as a general signal of low energy status to neuroendocrine systems in birds which improves utilization of nutrients.

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In the present study we used the primary cultures of chick embryonic muscle and liver cells as a model for potential mutual combination effects of leptin and insulin, respectively. The influence of both homones on the proliferation and protein synthesis was dose-dependent and related to the age of embryos from which the cells were isolated. Leptin (10 and 100 ng/well) increased the proliferation (estimated by DNA content and incorporation of labeled thymidine into DNA) and protein synthesis (determined by incorporation of labeled leucine into proteins) of muscle cells. The effect of leptin and insulin in muscle cells was similar. In younger embryo (11-day-old) the lower dose of leptin was more effective than the higher one compared to the insulin effect. Mutual effects of leptin and insulin were neither additive nor synergistic and were equivalent to the effects of individual hormones. In hepatocytes the influence of leptin was dependent on the age at which the cells were isolated (11- and 19-day-old embryos). The presence of insulin neither potentiated nor inhibited the effect of leptin.

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The pineal hormone melatonin controls reproduction of photoperiodic mammals and is an integral part of the circadian organization in birds. Recent findings indicate an involvement of this hormone also in more basic physiological processes, including growth, development, and aging. Melatonin may modulate growth in poultry through interaction with transcriptional factors, through interaction with hormones involved in growth control, and by modulation of energy metabolism and decreasing physical activity. Our studies showed that a single melatonin injection increased plasma growth hormone (GH) concentrations in the Japanese quail. Specific serotonin receptor blocker ketanserin did not preclude a stimulatory action of melatonin on GH synthesis. Serotonin agonist quipazine increased GH levels but failed to enhance the stimulatory effect of melatonin. Pretreatment with melatonin in drinking water did not affect the magnitude of the GH response to subcutaneous (s.c.) administration of thyrotropin releasing hormone (TRH) that considerably stimulated GH secretion. Present data suggest that melatonin modulates rather central neural pathways involved in the control of GH synthesis at the hypothalamic level than the sensitivity of the pituitary gland.

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In contrast to the situation in mammals, in which circadian melatonin production by the pineal gland does not begin until some time after birth, the development of pineal gland rhythmicity is an embryonic event in the precocial domestic fowl. A distinct melatonin rhythm was found in 19-d-old chick embryos maintained under light:dark (LD) 16:8. No significant variation in melatonin levels was detected in embryos exposed to LD 8:16. The melatonin rhythm in the pineal gland and plasma of chick embryos incubated for 18 d in LD 12:12 persisted for 2 d in constant darkness indicating that melatonin production is under circadian control at least from the end of embryonic life. A 1-d exposure to a LD cycle during the first postembryonic day was sufficient to entrain the melatonin rhythm, and previous embryonic exposure to either LD or constant darkness (DD) neither modified this rapid synchronization nor did it affect the melatonin pattern during the two subsequent days in DD. It is suggested that, in contrast to the situation in mammals, the avian embryo has evolved its own early circadian melatonin-producing system because, as a consequence of its extrauterine development, it cannot use the system of its mother.

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The pineal cells of chick embryos incubated in vitro exhibited a daily rhythm of melatonin synthesis under a 12:12 light:dark (LD) cycle at the embryonic days 16 and 19. In order to elucidate whether cyclic adenosine monophosphate (cAMP)--a component of the melatonin generating system--is already at work in the embryonic period, we measured the effects of forskolin and isobuthylmethylxantine (IBMX) on melatonin production, cAMP efflux and accumulation. Forskolin (after 10, 20, 30, 45, 60 and 90 min of administration) and IBMX (6 h), when applied during the light phase of LD cycle, stimulated melatonin production and cAMP efflux and accumulation during the embryonic period (at days 16 and 19 fo development). Our results suggest that the biochemical pathway involving cAMP, which controls melatonin production in the postnatal period, is developed before hatching and already on embryonic day 19 works in a way similar to that in post-hatched chicks. Differences in response to cAMP stimulation between 16- and 19-day-old pinealocytes seem to be mostly quantitative.

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Rooibos tea (RT) extract contains natural antioxidants and scavenging agents. We investigated the effects of different concentrations of RT extract in medium on growth and changes of growth parameters of cultured chick embryonic skeletal muscle cells. Presence of 2, 10 and 100% of RT extract in the culture of primary cells significantly inhibited cell proliferation. The inhibition of cell growth reflected on decreased DNA, RNA and protein contents in primary cell culture and fibroblasts and myoblasts. The ability of the primary cells, fibroblasts and myoblasts to synthesize DNA and protein in the presence of RT extract, measured as an amount of [3H]thymidine and [3H]leucine incorporated into DNA and de novo synthesized protein, corresponded with decreasing DNA and protein contents in all three cell types. The inhibition effect of RT rose with increasing concentration of the tea extract in the culture medium. Ornithine decarboxylase activity was significantly affected only by 100% RT extract in every examined cell types. These results suggest that the inhibitory effect of RT extract on the growth of primary cells, fibroblasts and myoblasts is due to the potent scavenging activity of the RT extract.

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Melatonin as a highly lipophilic compound readily enters all subcellular compartments and acts by various mechanisms. In the present study, we investigated the effects of different concentrations of melatonin in medium (physiological and supraphysiological doses) at two treatment times (48 and 120 hr) on growth and changes of growth parameters of cultured chick embryonic skeletal muscle cells. The physiological doses of melatonin (100 pg to 10 ng/ml of medium) stimulated proliferation of cells and raised DNA, RNA protein contents and an incorporation of [3H]leucine into cell protein after 48 hr of treatment. The prolongation of exposure to melatonin in the physiological dose to 120 hr or an increase of melatonin dose to a supraphysiological one evoked the inhibition of cell growth and proliferation by decreasing the number of cells and the amount of labeled leucine incorporated into cell protein. Results demonstrate that melatonin's action in these cells is time and dose dependent.

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The ability of beta-adrenergic agonists to stimulate ornithine decarboxylase activity (ODC) in chick muscle cell culture prepared from 11-day old embryos was evaluated. After 72 h of preincubation (myotube formation) the medium was supplemented for 4 h with noradrenaline, ritodrine, isoproterenol or clenbuterol, at concentrations of 10(-12), 10(-9) and 10(-6) mol/l. No significant response of ODC activity to noradrenaline was observed. The highest concentration (10(-6) mol/l) of the beta-adrenergic agonists ritodrine and isoproterenol elevated the activity of ODC. Clenbuterol was the most active beta-adrenergic agonist. The lowest concentration (10(-12) mol/l) had an apparent effect on ODC activity in muscle cell culture, and the substitution of media at levels of 10(-9) and 10(-6) mol/l had a similar effect in comparison to controls. The potency of beta-adrenergic agonists in increasing ODC activity was on the following order: noradrenaline, ritodrine, isoproterenol, clenbuterol. Results indicate that beta-adrenergic agonists may directly stimulate ODC activity followed by physiological processes in the muscle cells in the early stage of chick embryonic development.

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The chick pineal gland exhibits circadian rhythms in melatonin synthesis under in vivo and in vitro conditions. A daily rhythm of melatonin production was first detectable in pineal glands isolated from chick embryos at embryonic day 16 and incubated under a LD cycle. All pineal glands isolated from 17-day-old and older embryos were rhythmic while no gland isolated at embryonic day 14 and 15 exhibited a daily rhythm in melatonin synthesis. Melatonin production in static cultures of embryonic pineal cells was rhythmic over 48 h if the cells were kept under a LD cycle. When embryonic pineal cells were incubated in constant darkness the rhythm in melatonin production was damped within 48 h. These results suggest that chick pineal cells from embryonic day 16 onwards are photosensitive but that the endogenous component of the melatonin rhythm is not completely developed at that age. A soluble analogue of cAMP stimulated and norepinephrine inhibited melatonin synthesis in cultured embryonic pineal cells. These findings indicate that the stimulatory and inhibitory pathways controlling melatonin synthesis in the mature pineal gland are effective in pineal cells isolated from chick embryos at least 2 days before hatching.

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The importance of thyroid hormones (TH) in the normal development of muscles has been repeatedly postulated. The effects of physiological TH doses on ornithine decarboxylase (ODC) and protein synthesis in muscle cells have been studied using cell cultures prepared from 11-day-old chick embryos. Triiodothyronine nuclear receptors in primary muscle cell culture were characterized on the basis of the specific binding analysis as a single receptor class with the equilibrium dissociation constant Kd = 1.2 +/- 0.4 x 10(-10) mol/l and binding capacity Bmax = 0.21 +/- 0.09 fmol/micrograms DNA. While the physiological amounts of both triiodothyronine (T3) and thyroxine (T4) stimulated ODC activity after 2 hr of treatment, only T3 had the same stimulatory effect after 4 hr of treatment. Twenty-four hour exposure of muscle cell culture to TH did not change ODC activity. The incorporation of [3H]leucine into proteins was elevated only after 120 hr incubation in the presence of T4. Application of T4 caused also an increase in the protein content after 24 hr.

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The aim of the present experiments was to test two methods of separating myoblasts and fibroblasts (selective plating, differential trypsinization) from chick embryonal skeletal muscle and to compare their characteristics. Ornithine decarboxylase (ODC) activity, the amount of incorporated [3H]leucine into proteins and incorporation of [3H]thymidine into DNA were significantly higher in myoblasts than in fibroblasts separated by selective plating. When comparing myoblasts and fibroblasts separated by differential trypsinization, significantly higher ODC activity and greater incorporation of [3H]leucine into protein, but no incorporation of [3H]thymidine into DNA, were found in myoblasts. Higher ODC activity and greater incorporation of labelled leucine were found in fibroblasts separated by the selective plating than in fibroblasts separated by differential trypsinization. The incorporation of labelled thymidine into DNA was higher in myoblasts separated by selective plating than in myoblasts obtained by differential trypsinization. The method of selective plating appears to be simpler and adequate for obtaining myoblastic and fibroblastic cell cultures with sufficiently low mutual contamination. The method of differential trypsinization involves a more drastic treatment of cells and is more time consuming.

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1. Melatonin administration in drinking water (5 micrograms/ml) to Japanese quail resulted in a 20-fold increase of plasma melatonin levels in comparison with the control, day time concentration (0.34 +/- 0.05 vs 6.88 +/- 1.10 nmol/l). 2. Plasma triiodothyronine levels increased (5.8 +/- 0.93 vs 7.97 +/- 0.64 nmol/l), corticosterone decreased (28.04 +/- 3.42 vs 15.96 +/- 2.56 nmol/l) and no significant changes were recorded in thyroxine concentration after the treatment. 3. A higher occurrence of sleeping and lower occurrence of pecking were found in melatonin treated quail. 4. Abdominal fat deposition as well as the content of total lipids in the breast muscle and triacylglycerols in plasma were decreased in treated birds indicating an inhibitory effect of melatonin on lipogenesis. 5. Melatonin increased RNA content in the breast muscle but did not affect plasma glucose concentration and body weight.

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The variability of DNA content in turkey spermatozoa of four different lines and its correlation with body weight and sperm concentration were studied. In lines selected for lower body weight the DNA content was 2.034 and 2.036 pg per spermatozoon. In lines selected for higher body weight the DNA content was 2.267 and 2.370 pg per spermatozoon. Sperm concentration in 1 mm3 of semen, however, was higher in lines with a lower body weight (6.08-6.21 million) in comparison with lines selected for higher body weight (5.46-5.67 million). The correlations between the DNA content and sperm concentration were negative (r ranged from -.457 to -.860).

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We studied the influence of an embryonal application of antiestrogen tamoxifen on gonad differentiation and sex dimorphism during the growth of Slovgal chickens. A single application of 500 micrograms tamoxifen to the incubated eggs before the onset of gonad differentiation induced in pullets the growth of the right gonad, which usually develops only in cockerels. Comparing the size of both gonads it is clear that the above dose of antiestrogen had the 22.31% masculinizing effect. Morphological changes observed just after hatching correlated with the testosterone concentration in plasma. The pullets masculinized by tamoxifen had a significantly higher level of male hormone. The changes in sex differentiation were reflected in the altered growth of pullet bodies. With respect to the higher growth rate and more effective feed conversion, their growth can be appreciated as masculinized. The higher body weight at the end of seven-week fattening (4.25% in comparison with the control group of pullets) was due to the higher trunk weight. The growth was stimulated by tamoxifen application also in cockerels (5.57% increase in body weight) but it was not accompanied by any changes in feed conversion.

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A study of growth activity in the Japanese quail showed the rate of growth to be the highest, in both sexes, between the ages of 5 and 20 days. Positive allometry was manifested in skeletal muscle development, negative allometry or isometry in the case of the liver and heart. The protein/P DNA ratio rose progressively with age in all the given tissues and attained the maximum prior to sexual maturation. The P RNA/P DNA ratio rose markedly in all the tissues after only a few days and remained high throughout the whole period of development. Growth dynamics in the both sexes followed the same course; the only exception were proteosynthesis indicators, which attained higher values in females, in correlation to their greater body weight.

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