D. Lamošová

Perinatal development of circadian melatonin production in domestic chicks

Abstract: 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 I‐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.

DEVELOPMENT OF RHYTHMIC MELATONIN SYNTHESIS IN CULTURED PINEAL GLANDS AND PINEAL CELLS ISOLATED FROM CHICK EMBRYO

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.

Effect of restraint upon hypothalamic and adrenal catecholamines in Japanese quail.

1. Changes in catecholamine concentration after periods of restraint up to 48 h in male Japanese quail have been measured. 2. Hypothalamic catecholamines decreased after 10 min restraint. Dopamine concentration increased after 4 h and persisted to 48 h. 3. Plasma catecholamines increased after 10 min, remained high for 2 h and then decreased despite continuing restraint. Catecholamine content of adrenals slightly decreased during restraint. 4. The activity of adrenal phenylethanolamine-N-methyl transferase increased from the 4th hour of restraint.

INFLUENCE OF MELATONIN ON CHICK SKELETAL MUSCLE CELL GROWTH

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 melatonins action in these cells is time and dose dependent.

Regulation of rhythmic melatonin production in pineal cells of chick embryo by cyclic AMP.

Abstract. The pineal cells of chick embryos incubated in vitro exhibited a daily rhythm of melatonin synthesis under a 1212 lightdark (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 of 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 pinealo cytes seem to be mostly quantitative.

Effect of rooibos tea ( Aspalathus linearis ) on Japanese quail growth, egg production and plasma metabolites

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.

L‐thyroxine increases susceptibility of adult rats to low K+‐induced ventricular fibrillation, and sinus rhythm restoration in old rats

Hypokalaemia increases the risk for life‐threatening arrhythmias; however, data about interaction with thyroid status are lacking. The aim of this study was to investigate vulnerability of l‐thyroxine (T4)‐treated adult and old rats to low K+‐induced ventricular fibrillation (VF) as well as the ability of the heart to recover sinus rhythm. The experiments were performed on isolated heart preparations using the heart of 4‐ and 20‐month‐old female Wistar rats without and with feeding with T4 50 μg (100 g day)−1 over a period of 2 weeks. Perfusion of the isolated heart with oxygenated Krebs–Henseleit solution at constant pressure was followed by perfusion with K+‐deficient solution until occurrence of VF (< 10 min). After 2 min of sustained VF, the heart was perfused with normal solution for 10 min, during which sinus rhythm was restored. ECG, left ventricular pressure (LVP) and coronary flow were continuously monitored. The results showed that compared with untreated rats, the onset of low K+‐induced ventricular premature beats was delayed and their number was significantly decreased in both T4‐treated groups. Nevertheless, VF occurred earlier in T4‐treated than in non‐treated adult rats (6.78 ± 0.28 vs. 9.59 ± 0.55 min, P < 0.05), whereas the difference was not significant in aged animals. Furthermore, sinus rhythm appeared earlier in old T4‐treated rats compared with non‐treated rats (7.18 ± 0.57 vs. 8.94 ± 0.64 min, P < 0.05), whereas in adult hearts it set in at practically the same time regardless of treatment. In conclusion, our results indicate that administration of a pharmacological dose of T4 can increase the risk of low K+‐induced VF in adult but not in old animals; in the latter it even facilitated restoration of sinus rhythm. Moreover, enhanced mechanical function was observed in both adult and old T4‐treated hearts.

Selection of Japanese Quail for Resistance to Hypodynamy and Physiological Consequences of Selection

Ivanova I. Ye., T. A. Derendiayeva, G. I. Meleshko, Yeo Ya. Shepelev: Higher Plants in a Biological Life SupportSystemfor Man. Acta vet. Bmo 1996,65: 27-32. A model of human biological life support system (BLSS) was created with a photoautotrophic link including unicellular algae and higher plants having an equal oxygen production. This system model supported the vital activities of two people at the biomass regeneration of 92% from that consumed by them. The plant cultures studied were wheat grown on 11.25 m2 (of a total 15 m2) and several vegetable species. The total photosynthetic productivity of the plants was high, stable over the studied time span, and independent on the composition of the system. However, the grain productivity of wheat decreased periodically, and during certain harvests it decreased to almost zero. A detailed analysis revealed that this decrease was not caused by any of the systems adjacent links as a similar decrease in yield was also found in the control period with an autonomous growth of the plants in a closed volume of a chamber. Inclusion of bigher plants into BLSS led to a considerable improvement od food supply regeneration for man as compared to the previous model with only 26% regeneration effect. This inclusion did not exert any marked effect upon the general closure of the cycle. However, the biological value of the food for man was increased dramatically. This improvement is the main goal of designing and operating such BLSS systems. Regeneration. ecosystem. photosynthesis, photoautotroph link, unicellular algae. higher p.lants The prospect of long-teon existence of man outside the Earths biosphere (interplanetary flights, lunar and planetary bases) is connected with creating an artificial environment with the help of regenerating it from the products of vital activity. This environment must correspond to the evolutionarily conditioned biological needs of the humans and to provide their lives for generations. The fact of adaptive biology shows that the full-value environment for humans and other terrestrial organisms is the natural environment of the Earth. In order to recreate that environment artificially it is necessary to reproduce the mechanisms existing on Earth, i. e. to foon closed ecological systems including man. The lack of our knowledge about the natural environment of the humans prevents us from reproducing it by non-biological means, even if it were possible. The investigation of the problem of creating biological life-support systems (BLSS) of man began as early as in the 60ies. By the present time, experimental BLSS models have been created with different structures and different degrees of the cycle closure. , The creation of the systems was based on the ecological concept according to which strategy and tactics were worked out providing the organisms and populations were studied and then united into biocenoses, including also humans. The main method of solving the problem was the method of experimental modelling from the simple to the complex (Rashevski 1966).

Growth and Carcass Composition in Broiler-Type Chickens Following Passive Immunization of Insulin-Like Growth Factor-2 (IGF-2) Between 2 and 4 Weeks of Age

Abstract Ten broiler-type chickens at 2 weeks of age were injected daily with 0.5 ml of normal sheep serum while 10 others were similarly injected with 0.5 ml of a sheep anti-IGF-2 serum. Immunization with anti-IGF-2 serum had no significant effect upon body weight gain, on carcass composition, on appetite or food conversion. Liver weight was significantly increased (P