Comparative biochemistry and physiology最新文献

1. Incorporation of the thymidine analog 5-¹³¹iodo-2′-deoxyuridine (¹³¹IUDR) was measured in vivo in cotton rats, Sigmodon hispidus, white-footed mice, Peromyscus leucopus and pine voles, Microtus (Pitymys) pinetorum.

2. The percentage of initial activity retained per 10 g of body weight 48 hr post-injection o f 1 μc of ¹³¹IUDR was used as an index to cell proliferation in the intestinal epithelium. The values were: Sigmodon male 0·22, female 0·26; Peromyscus male 0·68, female 1·00; Microtus male 1·40, female 1·50.

3. When measurements of ¹³¹IUDR retention were plotted as a function of average oxygen consumption for these species the resulting regression equation indicated that for every 1 ml increase in oxygen consumption there was a doubling in cell proliferation. Animals tested which had high rates of metabolism likewise had high rates of cell proliferation.

1. Rump feathers in parental and hybrid populations of Ramphocelus tanagers along an altitudinal cline varied from scarlet to lemon yellow. However, spectral and chromatographic data indicated the presence of only a single carotenoid pigment. Dilution and statistical tests indicate that the observable colors were a function of pigment concentration. Spectral differences may be correlated with a single peak (470 nm) in the absorbance curve.

2. In a color variant of R. passerinii the spectral and chromatographic data suggest only a difference in pigment concentration. In both cases, these results were unexpected when compared to previous studies on seasonal change and the pigmentation of genetic mutants.

3. Melanic mutant scarlet tanagers retained the feather structure typical of carotenoid-containing feathers.

4. These observations relate to other studies on the biochemistry, metabolic and genetic control of avian carotenoid pigments and to proposed relationships between feather structure and pigment content.

1. In vivo and in vitro studies were carreid out comparing the effects of chicken insulin with those of equal amounts of beef insulin on the glycogen body of the domestic chicken.

2. The glycogen body glycogen moiety was unaltered regardless of experimental design indicating that the constancy of this structure's polysaccharide levels is neither attributable to use of a non-homologous hormone nor to restriction of the hormone by the avian blood-brain barrier.

1. Melatonin causes body blanching in rainbow trout (Salmo gairdneri) and the response is dose-dependent. A significant change in coloration was evoked by doses as low as 0·007 μg/g (intraperitoneal) and 2 μg/ml (in ambient water). Evidence is presented that melatonin given in ambient water affects coloration both through uptake in the blood as well as via possible diffusion through the skin. In spite of the apparently pharmacological nature of dose levels, the feasibility of a biological role of melatonin is evaluated.

2. Melatonin induced a dose-dependent impairment of body movements and equilibrium indicating that it has neural effects. The relative time course of impairment and blanching responses supports the view that the regulation of coloration may be mediated by action of melatonin primarily on peripheral sites.

3. Observations on blinded trout (with or without pineal) and the results of background reversal experiments indicate possible involvement of a melanophore-stimulating hormone. The possibility of an interaction of melatonin with this hormone and/or direct effect at the sympathetic terminal-melanophore level is considered.

4. Pinealectomy in trout with eyes intact had no effect either on responses to melatonin or on swimming activity. However, melatonin led to a significant inhibition of the latter. It was not possible to differentiate between the toxic effect and possibly specific effect of melatonin on swimming activity.

5. The significance of the present observations in relation to pineal function is also discussed.

1. Survival of Amphibolurus lizards in the field is enhanced by sodium retention during periods of water deprivation.

2. The water and electrolyte physiology of A. ornatus is conditioned by the growth rate of the individual.

3. Slow-growing A. ornatus are exceptionally tolerant to hypernatraemia and resist plasma sodium levels of almost 300 mmM/l for long periods in the field without loss of condition.

4. Fast-growing A. ornatus are unable to restrict indefinitely the sodium load to the extracellular fluid and penetration of the cells by sodium ions is accompanied by drastic weight losses which lead ultimately to death.

5. During weight loss the circulating fluid volume in maintained at the expense of other fluid compartments. Sodium levels in the tissues increase progressively but potassium levels are regulated by excretion.

6. Desert-living Amphibolurus species have a reduced rate of evaporative water loss which is evident in both cutaneous and pulmonary components.

1. ¹⁴C-inulin passage across the avian blood-brain barrier was facilitated by beef insulin.

2. Insulin-like activity of normal chicken cerebrospinal fluid was determined by the rat diaphragm method and equated to beef insulin standards.

3. Intravenous insulin did not alter cerebrospinal fluid-insulin-like activity levels; tolbutamide increased the insulin-like activity 5 min after injection and possibly again 60 min later.

1. During each of 12 consecutive months plasma acid mucopolysaccharides were extracted from new groups of cold-torpid and room-temperature Pseudemys and Chrysemys turtles. Acid mucopolysaccharides were separated as cetylpyridinium complexes into hyaluronic acid, chondroitin sulfate and heparin fractions and quantitated individually as uronic acid.

2. Levels of all three fractions were elevated, significantly, during the winter.

3. Significant differences were found for some of the three fractions between the sexes, the two species and the two environmental temperatures.

4. Correlation between heparin levels, blood clotting times and the period of natural dormancy indicate that increased plasma heparin constitutes at least part of an endogenous mechanism for the maintenance of hemofluidity during dormancy.

1. Ten lots of Dugesia tigrina, each consisting of 300–600 individuals, were extracted according to the method of Anton and Sayre for catecholamines and the extracts subjected to thin-layer chromatography.

2. Dopamine and lesser amounts of noradrenaline were found in the Dugesia extracts.

3. One lot each of Procotyla fluviatilis and Phagocata oregonensis yielded detectable amounts only of dopamine.

4. Dopamine appears to be the dominant catecholamine in these three species of planarians.

1. Neutral lipids of haemolymph and tissue of nonparasitized and parasitized Heliothis virescens (Fab.) and its insect parasite, Cardiochiles nigriceps Viereck, were fractionated into individual classes by a combination of silicic acid and Florisil® column chromatography.

2. Triglycerides were the predominant fraction in all groups and accounted for 48–60 per cent of the neutral lipid matter. Sterol esters were second to triglycerides in solid tissue and haemolypmh samples and made up 10–18 per cent of the total neutral lipids. These two fractions were followed closely by the free fatty acids (8–9 per cent) fraction.

3. Fatty acid analysis of the different neutral lipid spectra revealed the presence of two major fatty acids (palmic and oleic acid) and several minor fatty acids (myristic, myristoleic, palmitoleic and linoleic acid).

4. In general, the fatty acid content of the parasite resembled that of nonparasitized host tissue and haemolypmh.

5. The free fatty acid fraction of the neutral lipid spectrum was the most representative fraction found in the host and parasite.

1. Studies of growth and nitrogen balance were made on individual fish. The effects of temperature and diet change were investigated.

2. Feeding a low fat content diet tended to confirm the finding of other workers that 12°C is approximately the optimum temperature for trout growth.

3. 12°C is a compromise between efficient absorption in the gut and high energy demands at 16°C, and an inefficient absorption and low energy demands at 8°C.

4. Feeding high content diets resulted in fish at 16°C showing greater growth rates than those kept at 12°C.

5. Accompanying this, there was a greater reduction in ammonia excretion and a higher proportion of ingested nitrogen was retained for growth.

6. With temperature rise, a greater percentage of ingested fat was absorbed by the fish.

7. In these diets, fat replaces nitrogenous compounds as an energy source, and increasingly so with rise in temperature.