Acta biologica Academiae Scientiarum Hungaricae最新文献

Late effect of the perinatal administration of oestradiol dipropionate on pituitary gonadotrophs and the morphology of the LH-RH neuronal system was tested both in male and female rats. Oestrogen caused a severe reduction in the number and size of immunodetectable gonadotrophs in both sexes. By the 90th day of life, however, immunomorphology and distribution of the gonadotroph cells had became normal, and also the LH-RH system of the animals was similar to that of the intact controls. The lack of vaginal cycles indicated, however, that oestrogen might have permanently impaired higher brain centers regulating cyclic gonadotroph hormone release.

The paper presents morphological evidence that upon deafferentation small Golgi cells and granule cells of the cerebellar cortex as well as geniculo-cortical relay cells of the Lateral Geniculate Nucleus develop presynaptic sites on their otherwise exclusively postsynaptic dendrites. The new synapses are, therefore, mostly dendro-dendritic, a logical consequence of the fact that in the absence of axonal sprouting in the two regions, the reactive synaptogenesis in the cerebellar cortex and LGN is accomplished by the participation of the (newly formed) presynaptic dendrites.

Nuclear protein phosphatase (phosphoprotein phosphohydrolase, EC. 3.1.3.16, abbreviated: NPPase) was extracted from rat liver cell nuclei and subnuclear fractions under different conditions. NPPase activity proved to be strongly bound to chromatin and its presence cannot be explained by an incomplete removal of the cytoplasm from nuclear preparations. The small extent of activation of NPPase after treatment with ethanol or mercaptoethanol suggests that NPPase is present in the nucleus in its activated form. On the other hand, cytoplasmic protein phosphatase (abbreviated: NPPase) from rat liver also showed only a small extent of activation after precipitation with ammonium sulphate or ethanol. Therefore, the pronounced activation of cytoplasmic PPase, which has been observed in rabbit liver and skeletal muscle, cannot be used for differentiation between cytoplasmic and nuclear PPases in rat liver.

A coulometric model system is described which facilitates the quantitative study of the kinetics of transformation of amorphous calcium phosphate (ACP) into calcium-hydroxy-apatite (CHA) crystals. Proteoglycans of high molecular weight and over-sulphated polysaccharides (Arteparon, dextran sulphate) delayed CHA crystal formation. The results have enabled us to characterize the structure activity relationship of inhibitors of CHA formation, and to postulate a general structural requirement for molecules with inhibitory effect. As working mechanism, binding of calcium ions by sulphate groups of polyanions was supposed, which might reversibly impair "the critical nuclei formation", and/or further deposition of calcium ions in the CHA crystals. The clinical, therapeutical significance of the determination of the threshold concentration of different compounds is discussed.

In rabbits, the right hind limb was immobilized by means of plaster cast for 1, 2, 4 or 6 weeks and the activities of some metabolic enzymes: GOT, GPT, LDH, aldolase and acid phosphatase (in part of lysosomal origin), were examined in the slow m. soleus, and in the fast m. gastrocnemius. The former muscle is known to have mainly an oxidative, while the latter mainly a glycolytic type of metabolism. The activities of enzymes highly involved in the metabolism of the muscle diminished for a certain time during atrophy, then a relative rise occurred. Acid phosphatase activity likewise decreased after an initial relative increase. Reduction of enzymatic activities is explained by the activation of proteolytic enzymes, on the basis of measurements performed in these experiments and of results published by others. The decrease of enzymatic activity was more marked in the muscle which in normal state exhibits higher activity than in the other type of muscle studied. Thus, in the gastrocnemius a high rate of degradation of glycolytic enzymes was observed, while in the soleus degradation of oxidative enzymes prevailed. This phenomenon leads to the dedifferentiation of the muscle cell during immobilization.

The Golgi method more than hundred years old can reveal new results also in the current research of CNS. The study provides examples for using the Golgi method and demonstrates the types of neurons, the various types of interneurons, characterizes the stellate cells in layer IV of the cortex. The Golgi method is applicable for the observation of maturation process and also for demonstrating different pathological alterations of neurons in the CNS.

Nausea of vestibular origin can be used instead of poisoning in the conditioned taste aversion (CTA) paradigm. In an attempt to establish the forms of vestibular stimulation best suited for inducing CTA in rats, effectiveness of 2 h rotation (Exp. 1) was compared with tonal asymmetry elicited by unilateral microinjection of 5.0 microliters of 25% KCl into the vestibular complex (Exp. 2), by unilateral electrical stimulation of vestibular nuclei (100 Hz, 1 ms, 100-200 microA, 15 min--Exp. 3) or by 10 min polarization of labyrinth through electrodes inserted in the external auditory meati (Exp. 4). Nystagmus, deviation of the head and leaning towards the blocked and away from the stimulated side were typical symptoms. When the above stimuli were applied within 10 min after saccharin drinking, galvanic stimulation was ineffective, but electrical stimulation or chemical blockade of vestibular nuclei elicited marked CTA to saccharin, considerably stronger than CTA induced by rotation. It is concluded that direct interference with the activity of vestibular nuclei elicits CTA more effectively than the stimulation of the labyrinth and is, therefore, well suited for the analytical research into the mechanisms of CTA.

The serotoninergic neuron system of the midbrain and hypothalamus was previously shown to inhibit the basal secretion of the TRH-TSH-thyroid axis. The aim of the present study was to investigate the influence of the serotoninergic system on the TSH response of the adenohypophysis to specific loads. Serum TSH levels were determined 7 days after thyroidectomy or the beginning of thiouracil administration. Animals were simultaneously treated either by intrahypothalamic implantation of serotonin-containing needles or by intraventricular or daily subcutaneous injections of the same drug. The thiouracil-induced goitre formation and increase in serum TSH concentration were significantly diminished by serotonin treatment. Similarly, the thyroidectomy-induced rapid rise in TSH blood level was also remarkably inhibited in the serotonin-treated animals. Serotonin was proved to influence rather TRH-output than pituitary TSH secretion, since exogenous TRH, injected to serotonin-pretreated animals had the same TSH-mobilizing potency as found in the not premedicated group. It is concluded that besides the inhibition of the basal secretion of the TRH-TSH-thyroid axis by serotonin, there is an integrative role of the serotoninergic system in the mediation of the reactivity of this circuit in reply to specific influences loading pituitary-thyroid function.