Comparative biochemistry and physiology. Comparative physiology最新文献

The ability of the bullfrog gustatory system to discriminate odorants was examined by the cross-adaptation technique. Application of various odorants to the tongue increased the frequency of impulses of the gustatory nerve. The magnitude of the response to the second odorant, after the response to the first odorant was adapted, varied greatly with combination of odorants. Analysis of data obtained by a multidimensional scaling suggests that the ability of the frog gustatory system to discriminate odorants is similar to that of the human olfactory system.

The neural reaction to bitter stimuli was tested in the glossopharyngeal (GL) and chorda tympani (CT) nerves of mice. Relative responses to several bitter stimuli (quinine, iso-alpha-acids, L-tryptophan and L-phenylalanine) were greater in the GL nerve than in the CT nerve. Strain variability for taste sensitivity to bitter stimuli existed between two strains (C57BL and BALB/C). The GL nerve response to caffeine, iso-alpha-acids and L-phenylalanine in the BALB/C strain was greater than the response in the C57BL strain.

This experiment was undertaken to determine the changes in the mixed function oxidase system (MFO) in hepatic microsomes of male broiler chicks fed a 15% crude protein (LP) or 23% crude protein (HP) diet at different ages. The cytochromes P-450 and b5 content per unit of microsomal protein increased with age, while those per unit of body weight reached a maximum at 6 weeks of age, regardless of dietary protein levels. The activity of the MFO in chicks fed the HP diet was greater than those in chicks fed the LP diet during the first 9 weeks after hatching. At 4 weeks of age, cytochromes P-450 and b5, and NADPH-cytochrome c reductase were reduced by feeding the HP diet, but not by the LP diet.

The effect of dietary sorbose on diabetes after the incidence of the syndrome in the nonobese diabetic mouse was investigated in the animals from 8 to 14 weeks of age. When sucrose (200 g/kg diet) in a control diet was replaced by sorbose, the body weight and the blood glucose concentration were significantly reduced, but the serum insulin concentration was unchanged. The urinary glucose concentration was the same for both sucrose and sorbose diets. It is suggested that after the incidence of diabetes, dietary sorbose could not improve urinary excretion of glucose, even though sorbose could reduce the blood glucose concentration.

Olfactory responses (EOG: electro-olfactogram) of 11 species of teleost (five Cypriniformes and six non-Cypriniformes) to F-prostaglandins (PGF2 alpha, 15-keto-PGF2 alpha, 13,14-dihydro-15-keto-PGF2 alpha) were examined. All the Cypriniformes showed distinct EOG responses to F-prostaglandins at 10(-7) M. By contrast, non-Cypriniformes with the exception of ayu, Pleccoglossus altivelis, showed responses to 10(-7) M F-prostaglandins of < 22% of that to 10(-5) M L-serine, and they were anosmic to 10(-8) M F-prostaglandins. These results indicate that F-prostaglandins are potent chemical stimulants in Cypriniformes, and suggest that F-prostaglandins may be commonly used as sex pheromones in Cypriniformes, whereas they seem not to have pheromonal functions in most non-Cypriniformes examined.

We examined the effects of tetrodotoxin and reduced extracellular sodium concentrations on the myocardial action potential plateau in neonatal and adult guinea-pigs. Control action potential duration at 50% repolarization (APD50) was significantly shorter in the neonate than in the adult. Tetrodotoxin and low sodium shortened APD50 more prominently in the adult than in the neonate. Since a late sodium current with slow inactivation kinetics is reported in the ventricular myocytes, the results suggest that the late sodium current might contribute to the development prolongation of the action potential duration observed in the guinea-pig myocardium.

Purified porcine antithrombin III stimulates motility and acts as a chemoattractant of washed boar sperm. Porcine follicular fluid and blood plasma both possess chemotactic activity. Porcine antithrombin III-immunoreactive molecules are distributed on the zona pellucida of ovulated eggs flushed from the swine oviducts. We propose that antithrombin III plays important roles in the mammalian fertilization process in vivo.

1. A simplified two-time-point method for measuring whole-body protein synthesis of chicken embryos cultured in vitro was developed. 2. The chicken embryos at 7 days of egg incubation age were cultured with a synthetic medium containing L-[4-3H]phenylalanine in a rotatory whole-embryo culture apparatus for a period of up to 60 min. 3. An adequate combination of measurement time points was examined by comparing fractional synthesis rates calculated by the simplified two-time-point method with those estimated by a full curve-fitting method which would give best estimates. The effect of fragmented bovine growth hormone added to the culture medium on fractional synthesis rates was also tested. 4. The results indicated that the closest fractional synthesis rates by the simplified two-time-point method to the one by the full curve-fitting method were obtained by taking the time points of t1 at 10 min and t2 at 30 or 60 min with intraperitoneal injection of the tracer prior to the culture period. 5. With the simplified two-time-point method, the fragmentation of bovine growth hormone was shown to increase the biopotency in inducing fractional synthesis rates approximately 100 times as high as that of the intact growth hormone. 6. It was concluded, therefore, that the present assay method would be convenient and sensitive for searching physiologically active compounds in promoting growth and protein synthesis in the chicken.

1. Uptake of L-leucine, L-phenylalanine, L-proline and L-lysine into brush border membrane vesicles from rats fed either a medium-chain triglyceride (MCT) or a long-chain triglyceride (LCT) diet was studied under conditions of the presence of absence of a Na+ gradient. 2. From the results of initial rate, Na(+)-dependent transport in LCT feeding were lower than in feeding MCT. The Na(+)-independent transport did not vary in either group except for L-lysine uptake. 3. For L-leucine, L-phenylalanine and L-proline in Na+ dependence, kinetic analysis revealed 4-6-fold smaller Vmax values in LCT group than in MCT group. L-Lysine in Na(+)-independent transport was 10-fold lower in LCT group than in MCT group. The Km values were not affected by feeding the LCT or MCT diet. 4. It is clear that amino acid transport is regulated by different types of dietary fat. We consider that the alteration of transport activity is attributable to the changes in number of membrane-bound transport carriers but not to their affinity.