Comparative biochemistry and physiology. Comparative physiology最新文献

1. The muscle tension and the state of high-energy phosphate metabolism during contraction of the sartorius muscle in frogs (Rana catesbeiana) starved for 1-5 months was studied by in vivo 31P-NMR spectrometry. 2. Muscle tension began to decrease after 2-month starvation compared with the control group and decreased to about one-third of the control value after a 5-month starvation. 3. Muscle contraction induced by electrical stimulation or the use of anaerobic perfusion fluid did not decrease the concentration of creatine phosphate (PCr) or beta-ATP, and only negligibly changed the PCr/Pi ratio from starvation. 4. These results suggest a decrease in creatine kinase activity in the muscle of starved frogs.

1. We evaluated the effect of electric shock on swimming leeches by measuring changes in high-energy phosphate metabolism using in vivo 31P-NMR. 2. Leeches electrically stimulated during swimming showed anodal galvanotaxis and stopped swimming with stimulation at strong current. 3. Comparison of the concentrations of high-energy phosphate metabolites before and after electric shock using 31P-NMR revealed a marked decrease in beta-ATP and an increase in that of Pi. 4. Electric shock apparently induces excessive muscle fatigue in leeches, resulting in transient paralysis.

1. Receptor currents in frog taste cells induced by taste stimuli of NaCl and HCl were studied in situ using a voltage clamp method with a single microelectrode. 2. Under voltage clamping of a taste cell at -20 mV an inward receptor current of a mean of 176 pA was induced by taste stimulation with 0.5 M NaCl and the input resistance was largely reduced during the stimulation. 3. A large sustained inward current was evoked by HCl stimulation but the input resistance was slightly reduced. 4. Increasing the holding potential in the negative direction linearly increased the inward receptor current by NaCl stimulation but did not remarkably change it by HCl stimulation.

1. The generative mechanism of the acid-induced receptor potential in frog taste cells was re-examined with micro-electrodes. 2. The amplitude of receptor potentials in a taste cell induced by 1 mM acetic acid increased as the concentration of Ca2+, Sr2+ and Ba2+ on the tongue surface was increased. 3. The amplitude of the acid-induced receptor potential was inhibited by about 40% by a proton pump blocker DCCD (N,N'-dicyclohexylcarbodiimide) added to superficial normal saline. 4. It is concluded that most of the acid-induced response in a frog taste cell was generated by current carried through proton-gated Ca2+ channel of the apical receptive membrane. The remaining part of the acid response was generated by current carried through a DCCD-sensitive proton transporter of the receptive membrane.

1. Binding sites for testosterone (TR) and dihydrotestosterone (DHTR) were separately detected in various organs of the rabbit. 2. Possibilities obtained were suggested as follows. 3. Sexual dimorphism of TR or DHTR level was present among organs. 4. The responsiveness of TR or DHTR levels to estradiol-17 beta with testosterone, but not estradiol-17 beta alone is different among organs, with sexual minor dimorphism.

1. Electrophysiological properties of cardiac muscle in Suncus murinus were compared with those of rat and guinea pig. 2. The resting potential and resting potassium permeability were smallest in suncus heart. 3. The action potential duration in suncus was also shortest, and effects of tetraethylammonium suggested that transient outward current is well developed in suncus. 4. Elicitation of slow response was very difficult in suncus, suggesting poor development of the calcium channel.

1. The relationship between body fat reserves and blood variables was calculated in 26 wild boar in order to evaluate blood variables as indicators for the nutritional status. 2. In juveniles only a relationship between bone marrow fat and haemoglobin, packed cell volume, albumin, total globulin, gamma globulin, alkaline phosphatase and urea were found. 3. Urea and packed cell volume accounted (together) for more than 90% of the variance of bone marrow fat.

1. To either an agar-containing diet or an agar-free diet, 0, 0.3 and 2.0 mg/100 g of beta-carotene were incorporated and fed to groups of five rats for 28 days. 2. Weight gain and food consumption of rats fed different dietary groups did not show a significant difference (P > 0.05). 3. Colon weight, colonic mucosal DNA and RNA were generally higher in rats fed agar diets than rats fed agar-free diets at either beta-carotene supplementation level. 4. Mucinase activity was higher (P < 0.05) in rats fed the agar diet than in rats fed an agar-free diet without beta-carotene. However, the difference was not observed (P > 0.05) when beta-carotene was incorporated. 5. These data suggest that colonic mucin degradation in rats fed an agar diet decreased when the dietary beta-carotene inclusion level increased.

1. Ca2+ concentration in blood plasma and Ca(2+)-ATPase activity in epiphysis of tibia at 3 and 15 weeks of age were compared among three quail lines (LL, RR and SS) selected for body weight. 2. The Ca2+ concentrations in blood plasma were higher in order of LL, RR and SS at 3 and 15 weeks of age in both sexes. Ca2+ concentrations in blood plasma at 3 weeks of age were lower than those of 15 weeks of age in both sexes. 3. At 15 weeks of age, the concentration of females was significantly higher than that of males in all lines. 4. The activities of Ca(2+)-ATPase in epiphysis of tibia was higher in order of SS, RR and LL at both ages and in both sexes. 5. The activities of Ca(2+)-ATPase at 3 weeks of age were significantly higher than those of 15 weeks of age in all lines. 6. These results suggest that the selection for body weight changed the concentration of Ca2+ in blood plasma and the activities of Ca(2+)-ATPase in epiphysis of tibia, parallel to the change of tibia length.

1. Serum Ca level of goldfish administered with homogenate of the corpuscles of Stannius (CS) taken from 1/3 seawater-acclimated goldfish was significantly lower than that of the control goldfish up to 2 hr after administration. 2. Serum Ca, Mg, Pi, Na and K levels of rats administered with CS homogenates of freshwater eels, 1/3 seawater-acclimated goldfish, or seawater-inhabited wrasse were not statistically different from those of control rats during the 3 hr investigation. 3. It was concluded that in rats, CS homogenates did not decrease the serum mineral levels under the present conditions.