Comparative biochemistry and physiology最新文献

1. The physiological potencies of l-thyroxine (l-T₄) and l-triiodothyroxine (l-T₃) are equal in propylthiouracil (PTU)-fed radiothyroidectomized (RT̄) chicks.

2. Propylthiouracil does not seem to interfere in the peripheral activity of T₄ or T₃ in the chick.

3. Liver hypertrophy and liver glycogen accumulation are distinct criteria of hypothyroidism in the chick and are restored to near normal levels by small daily doses of T₄ or T₃.

4. The thyroid enlargement subsequent to the feeding of PTU is further increase by the administration of multiple subnormal doses of T₄ or T₃.

5. The poor growth rate of PTU-fed and RT̄ chicks compared to control chicks is due to decreased food intake. The apparent digestibility of protein, fat, and energy, as well as the efficiecy of food utilization are affected equally by T₄ or T₃ in PTU-fed or radiothyroidectomized chicks.

1. The nitrogen, amino acid and carbohydrate content of the different regions of the gastro-intestinal tract differ significantly depending on source of dietary protein.

2. There are significant differences in the molar ratios of the intestinal amino acid pool up to 4 hr after feeding.

3. The molar ratios and concentrations of individual amino acids depend on the dietary protein source, the region of the intestine and time after feeding.

4. Endogenous nitrogen recruitment is insufficient to maintain homeostasis in the entire intestine.

1. The oxygen affinity of the horseshoe crab (Tachypleus tridentatus) hemocyanin is greatly reduced by removing calcium ions either by dialysis against Tris buffer or by addition of EDTA. This effect is largely reversed by the addition of CaCl₂.

2. The logarithmic plot of P₅₀ against calcium ion concentration is a linear function.

3. At low concentrations of calcium ion, the oxygen affinity of hemocyanin varies with changes in the concentration of free calcium ions and also the degree of oxygenation.

4. At concentrations of calcium ion above 20 mM, it depends only on the concentration of free calcium ions.

5. Succinylated hemocyanin has a different absorption spectrum with maximal absorption peaks at 390 mμ. It is incapable of binding reversibly with oxygen.

1. Specific granular cells were found in the heart, mantle and subesophageal ganglia of the snails Helix aspersa and Strophocheilus oblongus.

2. Histochemical methods for the demonstration of enterochromaffin granules gave positive results in these cells.

3. Differential osmium reduction by nerves in these hearts showed two kinds of fibres: osmiophilic and non-osmiophilic nerves and gives histological evidence of a double innervation (inhibitory and stimulatory fibres) to the snail heart.

4. Osmiophilic endings are reported in the ventricle and auricle and are shown to end very close to the granular cells.

5. No neurosecretory-staining material could be traced along nerves in these hearts.

6. One large bipolar neuron is described in these hearts.

7. Histological preparations of the heart of Strophocheilus oblongus that had long been stimulated through its cardiac nerve show a release of the granular content in the cells and disclose stages of a secretory cycle. It is suggested that these cells are glandular tissue and perform a hormonal function.

1. Clearances of creatinine, inulin and para-aminmohippurate as well as diluting ability and response to hypertonic saline infusion were measured in Macaca speciosa.

2. Clearance values obtained are similar to those reported in other small primate species and similar to values in humans.

3. Diluting ability is comparable to that in man.

4. This species alters sodium excretion in response to hypertonic saline infusion by changes in tubular reabsorption, rather by changing glomerular filtration rate.

1. The temperature dependence of the frequency of induced waves of the olfactory bulbs of toads, iguanas and snakes has been determined.

2. Linear, semilogarithmic and log/log transformations of these data were equally statistically significant.

3. The semilogarithmic transformations yielded Q₁₀ values varying between 1·36 and 1·71 for the four species examined.

4. The results support the likelihood that a common mechanism for the generation of olfactory induced waves exists amongst the vertebrata.

1. Comparative studies on biliary amylase were done in fish, amphibian, reptile, bird and mammal.

2. Pancreatic amylase is tenfold and eightfold more active in Passer domesticus and Corvus spledens respectively than biliary amylase.

3. Amylase in bile is either absent or with only little activity in carnivore vertebrates. The reducing sugar produced was 4.5 mg and 5.7 mg/100 ml in toad and Calotes respectively.

4. NaCl dependence is pronounced and leads to about 50 per cent increase in activity.

5. Optimum pH 4.9, for amylolytic activity in bile and liver of crow, corresponds with the luminal pH of the duodenum.