High-affinity binding ofβ-alanine to cerebral synaptosomes might involve glycine-receptors

Summary High-affinity, Na⁺-independent binding of -alanine to a synaptosomal fraction of rat brain was potently inhibited by glycine and by some other -amino acids, but not by taurine or GABA. This binding mechanism, which was also sensitive to both bicuculline and strychnine, might involve synaptic receptors for both -alanine and glycine.This study was supported in part by Centro Ramón y Cajal and Fundacion Juan March.     

Control of obesity inA vy /a mice by 5α-androstan-17-one

Summary Treating VY/WfL-A ^vy /a mice with 5-androstan-17-one, a mammalian glucose-6-phosphate dehydrogenase inhibitor, prevented the mice from becoming obese. The weight difference between treated and controlA ^vy /a mice was mainly due to a decreased accumulation of triacylglycerol. The compound did not suppress appetite, had no detectable toxicity and did not affect the lipogenesis rates in the liver and carcass. The weight-controlling effect of 5-androstan-17-one inA ^vy /a mice was reversible upon withdrawal of treatment.The authors wish to thank Mr W.R. Gibson and Drs C.G. Culbertson and P.N. Harris for performing the pathological examinations.     

Reciprocal changes in serum free thyroxine fraction and thyrotropin level after administration of thiocyanate to rats

Summary The administration of thiocyanate to rats caused a significant increase of serum free thyroxine fraction, which coincided with the significant decrease of TSH level. The other components (AFT₄, T₄, T₃) in serum at this time were decreased or unchanged. The finding suggests the role of free thyroxine fraction in feed-back regulation of TSH secretion.Acknowledgment. We thank Dr A. Parlow and the NIAMDD, Rat Pituitary Hormone Distribution Program, for material for rat TSH immunoassay; Dr J. Nauman (Inst. Postgrad. Med., Warsaw, Poland) for T₃ antibody, and to Ing. J. Sadlo, Mrs M. t'astná and Miss R Fajkoová for technical assistance.     

Age-dependent response of lactate dehydrogenase of pituitary of rat to testosterone

Summary The effects of time and various doses of testosterone on the responsiveness of lactate dehydrogenase of pituitary of 7-, 38- and 78-week-old rats were studied. The activity of the enzyme increases in 78-week-old rats. Castration decreases the enzyme activity at all ages. Maximum increase in the enzyme activity is seen with 50 and 100 g of testosterone 4 h after administration of hormone to castrated rats. No further time and dose-dependent effect is observed. The magnitude of increase for the enzyme is higher at the age of 38 weeks and decreases in 78-week-old rats.To whom all correspondence should be addressed. The authors are grateful to Professor M.S. Kanungo, Biochemistry Laboratory, Department of Zoology, Banaras Hindu University for the suggestions and encouragement. K.V.G. thanks the PL-480 for a research fellowship.     

Seasonal variations in fat body metabolism of the green frog Rana esculenta (L.).

Rana esculenta (L.), kept under natural conditions, show almost constant body weights in the annual cycle. Fat body weight, however, has a distinct maximum in October decreasing continuously to a May minimum which is also evident in the fat body index. The triglyceride and protein contents show the same course. Suprisingly high amounts of glycogen are found, which reach a maximum in August.     

Demonstration of generators of the locomotor and respiration rhythms in the cervico-thoracic spinal cord of rabbits

In curarized Rabbits whose cervico-thoracic cord has been isolated through C2 and Th12 transections, a pharmacological activation (nialamide-DOPA) disclosed distinct rhythmic efferent activities, locomotor-like bursts in forelimb muscle nerves and "respiratory" discharges in the phrenic nerves: they originate respectively from a cervico-thoracic locomotion generator and from a "respiration" generator; these spinal generators appear to be interconnected with each other.     

The effect ofβ-adrenergic stimulation and blockade on the efflux of PGE1-like material from the isolated perfused rabbit heart

Summary Prostaglandin (PG) release was measured from the isolated perfused rabbit heart. The effects of -adrenergic stimulation and blockade suggest that PG synthesis is regulated in part by adrenergic mechanisms.     

Androgen levels in the rete testis fluid during sexual development

Summary The concentrations of testosterone (T) and 5-dihydrotestosterone were measured in fluid collected from the rete testis of immature and adult rats. The results indicate that adult levels of T are attained in the seminiferous tubules much earlier than in the peripheral circulation.This work was performed at the Worcester Foundation for Experimental Biology, Shrewsbury, Massachusetts, USA and supported by the National Institutes of Health through grants HD12641 and HD12642. We thank Dr B.V. Caldwell for antiserum to testosterone.