Studies on serum oestrogen and progesterone levels during the oestrous cycle and early pregnancy in mares

Concentrations of progesterone and oestrogens were determined by radioimmunoassay in the peripheral blood of 22 Percheron and Breton breed mares from the 6th day of oestrus to the 150th day of pregnancy. Periodical variation patterns for the mean values of oestrone, oestradiol 17beta and total oestrogens in the cycling mares were found, with two peaks on the third day before and the 15th day after ovulation, and one depression on the 6th day of oestrus. In pregnant mares, the concentrations of oestrone and oestradiol 17beta increased rapidly (P less than 0.05) after Day 105 of gestation. Progesterone levels declined after Day 18 of the cycle in cycling mares, whereas they increased in the pregnant mares. Marked changes in the ratio of total oestrogen to progesterone concentrations were found in cycling mares, especially at oestrus, but in pregnant mares the ratio always remained below 1.00.

Synthesis and degradation of methylated proteins of mouse organs: correlation with protein synthesis and degradation

L-(Methyl-14C)-methionine was administered i.p. to mice, and the incorporation of radioactive methionine into proteins and methyllysine and methylarginine residues formed by the transfer of the methyl-14C group of methionine were measured. Tissue protein was actively methylated in organs having a high activity of protein synthesis, and the in vivo methylating activity in organs was not correlated with theprotein methylating activity of the organs determined in vitro. Puromycin inhibited both protein synthesis and protein methylation in mouse organs to a similar degree. Neither the formation of S-adenosyl-(methyl-14C)-methionine nor protein methylase was inhibited by puromycin. The data suggests that proteins are methylated immediately after protein synthesis, that is, newly synthesized proteins are the substrates of protein methylation. Radioactive methionine and the [C14] methyl groups of methyllysine and methylarginine residues of tissue proteins are degraded in parallel over a period of 3 wk, suggesting that protein methylation is an irreversible type of protein modification.

Physicochemical studies of taste reception. III. Interpretation of the water response in taste reception

The model membrane composed of a Millipore filter paper and the total lipids from bovine tongue epithelium or phosphatidylcholine from egg yolk simulated well the water response of a living taste cell, The water response observed with the model membrane adapted to various salt solutions was interpreted in terms of changes in electric potential at the membrane-solution interface, i.e. the water response was attributed to the e.m.f. change produced by diffusion of the electrolytes dissolved in (or adsorbed on) the membrane surface into the bulk solution. The water response of the frog tongue was also investigated by measuring the neural response of the glossopharyngeal nerve. The results obtained were consistent with the mechanism proposed in the present paper. The response of the frog to Ca2+ was examined under the condition where the water response was suppressed, and it was concluded that the water response of the frog is different from the response to Ca2+.

Pysicochemical studies of taste reception. V. Suppressive effect of salts on sugar response of the frog

The tast responses of frog to various kinds of sugars were measured quantitatively by use of the glossopharyngeal nerve activity under an appropriate condition where the water response was completely suppressed. The concentration dependences of response of frog tongue to D-fructose, D-glucose, and sucrose were almost the same, D-galactose, however, elicited a much larger response in comparison with the other sugars in the whole range of concentrations examined. The sugar response was suppressed extensively by the presence of small amount of salts in the stimulating sugar solution. The suppressive effects of NaCl, KCl, MgCl2, MgSO4, and K4Fe(CN)6 were examined with a fixed concentration of sugar. The results obtained with these salts, added in various concentrations, fell on a single curve when the data were plotted against the ionic strength in the stimulating solution. The present results were consistent with the notion that the taste receptor potential for salts or acids is attributable to a change in the phase boundary potential at the membrane-solution interface as proposed in the previous papers of this series.

Physico-chemical studies of taste reception. IV. Response of individual phospholipid membrane to a variety of chemical stimuli

Variations in the membrane potential across model membranes made of Millipore filter paper and various single phospholipids were measured in response to salt, acid and distilled water. The phospholipids used were phosphatidylcholine (c), spingomyelin (SM), phosphatidylethanolamine (PE), and phosphatidylserine (PS). Results were compared with those obtained with the model membrane made of the total lipids extracted from bovine tongue epithelium, which simulated well the receptor potential observed with intact tast organs. The membrane potential of PE- and PS-membranes increased monotonously with increase of the concentration of 1:1 type salt, while that of PC- and SM-membranes exhibited no appreciable change in 1:1 salt solutions. Application of CaC12 to the membranes brought about a varity of response depending on the species of lipids used. PE- and PS-membranes showed a larger change in the membrane potential than PC- and SM-membranes when pH of the solution was varied. Fe-3+ was strongly absorbed on the surface of PC and SM-membranes, while Fe-3+ bound to PE- and PS-membranes was easily removed by an application of salt solution. A transient increase in the membrane potential was observed when distilled water was applied to the membrane adapted to an appropriate salt solution, which was similar to the water response observed in taste cells. PC- and SM-membranes responded to water when the membrane adapted to either NaC1 or CaC12, but PS-membrane responded only when the membrane was adapted to a solution containing CaC12. PE-membrane did not respond to water in any cases examined. The membrane prepared with a mixture of two species of phospholipids responded neither to salt nor to water, while the membranes prepared with the total lipids or a mixture of three species of lipids in appropriate ratio responded to both. The water response of the total lipids membrane vanished in a high temperature medium, while the water response of PC-membrane retained in all temperature ranges examined, i.e. between 20 degrees and 62 degrees C. The results obtained suggest that a mosaic structure, where each domain has different functions against various chemical stimuli, is formed on the surface of the model membrane made of the total lipids.