Acta biologica Academiae Scientiarum Hungaricae最新文献

Similarly to the effect of T3, the tail absorption of frog larvae (Rana arvalis) was stimulated in vitro by the sympathomimetic agents adrenaline, isoproterenol, ephedrine and the adrenaline analogue MMT. The effect of T3 administration was not inhibited by adrenaline, isoproterenol and MMT, but it was by ephedrine and T3 pretreatment. The adrenaline and isoproterenol effect manifested itself after early administration, but not after late and while ephedrine and MMT were effective at long-term administration, even it administered at a later time. Our experiments draw attention to the metamorphotic effect of substances capable of binding to beta-receptors. Their effect may be explained partly by the increase in the cAMP level, partly by a relationship existing between the beta-receptor and the T3 receptor.

The plaster-cast immobilization of the right hind limbs of rats has been investigated. Examinations were performed on the changes in weight of both types of skeletal muscles, i.e. the fast and the slow ones, the m. extensor digitorum longus and the m. gastrocnemius on the one hand, and the m. soleus on the other. The most significant loss in weight was observed in the gastrocnemius muscle. The ATP-Ca2+-induced isometric tension as well as the speed of contraction of glycerine-treated myofibrillar preparations considerably decreased as a result of 28-day immobilization. The most marked change was observed in the soleus muscle. There was a similar decrease in the specific activity of myofibrillar myosin ATPase prepared from immobilized muscles. The specific activity of K+-EDTA myosin ATPase did not change.

The role of the extra-embryonic organs (e.g. placenta) in the feto-maternal immunological interactions is not clear. Trophoblast cells of human placenta were studied in vitro in relation to their adaptive capacities under the immunological influence of allogeneic leucocytes of pregnant women. It was shown that after an 18-h interaction some trophoblastic cells were still viable, they were rich in glycoproteins and RNA, and elicited a prominent activity of some enzymes. Mitosis was often seen. The authors suppose that the trophoblast is highly adaptable to some immunological influences in vitro.

Gametogenesis of the snail was shown to be affected by cortisol, deoxycorticosterone and 19-nortestosterone. An activation of the ovogenetic apparatus while uncertain responses of spermiogenesis were observed. On the basis of effects of non-gonadospecific steroids it is concluded that the receptors of the snail's spermiocytes are not selective. The spermatogenesis was influenced more significantly by 19-nortestosterone as compared to testosterone, having been examined earlier.

Corticosterone was determined by means of competitive protein binding in the plasma of ovariectomized, thyroidectomized, ovariectomized and thyroidectomized, thyroxin-treated, corticosterone-treated and control Japanese quails, exposed to short or long photoperiod. Female birds exposed to short photoperiod possessed a slightly (not significantly) higher plasma corticosterone level than male ones. In photostimulated animals, however, the plasma corticosterone level showed no sex difference. Unlike in male quails, photostimulation did not enhance corticosteronaemia in the female ones. Corticosterone level was decreased by ovariectomy in both short-day and long-day birds. It was decreased by thyroidectomy and increased by thyroxine treatment in short-day birds, while the same interventions were ineffective in photostimulated ones. The data obtained point to that thyroxine treatment enhances, while the lack of ovarian sexual steroids decreases the plasma corticosterone level of female Japanese quails. Comparison of data obtained from ovariectomized + thyroidectomized birds shows that light may be responsible for elevated corticosteronaemia per se.

The dominance or recessiveness of glucocorticoid responsiveness and albumin production of different hepatoma cell lines were investigated using somatic cell hybrids. The majority of the intraspecific, intraorgan hybrids between glucocorticoid sensitive, tyrosine aminotransferase (TAT) non-inducible, albumin non-secreting parents and glucocorticoid resistant, TAT-inducible, albumin secreting parents were glucocorticoid sensitive, TAT non-inducible and albumin non-producing. The TAT inducibility was extinguished in interspecific, interorgan hybrids of TAT-inducible hepatoma and non-inducible Chinese hamster fibroblast parents. No TAT reexpression was observed among the many independent hybrid clones. The experiments provided evidence for the non-coordinate control of the expression of differentiated functions in hepatoma hybrid cells.

The serum levels of calcitonin, calcium and inorganic phosphate, and the urine concentrations of calcium and inorganic phosphate were measured in male and female rats in spring and in autumn. Significantly higher levels of serum calcitonin and calcium were found in spring than in autumn in both male and female rats. The calcium and inorganic phosphate contents of the urine were also significantly higher in spring than in autumn in both sexes. In addition to the seasonal variations, the serum level of calcitonin was higher in female than in male rats both in spring and in autumn.

A 250-fold purified ATP-dependent DNase from Bacillus cereus has been separated to DNA-dependent ATPase I and II and a DNase specific for single-stranded DNA (ssDNase) by means of high resolution of DEAE cellulose chromatography. Simultaneously with the separation of ATPase and ssDNase, a decrease in ATP-dependent DNase activity was observed. Complete separation resulted in the total loss of ATP-dependent DNase activity. Reconstitution of ATP-stimulated DNase activity was dependent on the ratio of the combined ATPase II and ssDNase.