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One of the major classes of ionotropic glutamate receptors is the class of N-methyl-D-aspartate receptors (NMDARs). Receptor activation recruits, via calcium signal transduction mechanisms which play important roles in oxidative metabolism, mitochondrial free radical production and occurrence of other mitochondrial factors which potentially contribute to excitotoxicity and neuronal death. In the present study, the effects of stimulation of NMDARs by applying N-methyl-D-aspartic acid (NMDA) in the brain, liver, kidneys and pancreas on change of the activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSHPx) and in the amount of reduced glutathione (GSH) in blood, brain, liver and kidneys has been investigated. Statistically significant decrease of the activity of SOD, CAT and GSHPx and in the amount of reduced glutathione (GSH) was found in the examined organs after administration of NMDA, an agonist of NMDA receptors, demonstrating that NMDA administration compromises the antioxidant status in the investigated organs of the mouse.

The effect of acute exposure of intraperitoneal injection of kainic acid (KA) on the activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSHPx), amount of reduced glutathione (GSH) and content of ascorbic acid (ASC) has been studied in brain, liver and kidneys of male mice. Animals (n= 144) were treated KA with one dose, i.e. 12 mg/kg body weight or saline solution. The influence of KA on the tested parameters after 2, 4, 6 and 24 hours was estimated. After the injection of KA it has been found that the activity of SOD, GSHPx and CAT is very clearly reduced in the brain and to a lesser extent in liver and kidneys. Simultaneously a decrease in the activity of antioxidant enzymes in the brain, liver and kidneys was accompanied by a decrease of the amount of GSH and ASC. A decrease in the activity of SOD, CAT, GSHPx (after 2 and 4 h) and amount of GSH and ASC in the brain, liver and kidneys suggests that oxidative stress plays important role in the pathogenesis of KA in mice. The obtained results suggest that KA not only is toxic to the brain but also for the liver and kidneys of mice.

Caryometric measurements in tanycytes of the median eminence (ME) in sexually mature male and femaleRana temporaria captured in their natural habitat showed distinct annual fluctuations of nuclear volume.In both sexes, largest nuclear volumes were observed in these cells during the annual phase preceding breeding period (1st decade of March), and minimal values of nuclear volume in the middle of the period of active life (2nd decade of July). The role of the ependymal cells of the ME in transport of neurohormones from the cerebrospinal fluid to the portal vessels of the ME is discussed.

Diurnal changes in content of cytoplasmic RNA in the supraoptic nucleus (SON) and arcuate nucleus (AN) neurons of the mouse hypothalamus induced by ACTH were analysed microspectrophotometrically. Single injections of ACTH were administered in a dose of 100 I.U./kg at the same or different times of day and night. A single dose of ACTH administered at the same or a different time caused, within the first 4 h, a decrease in the total content of cytoplasmic RNA in neurocytes of the examined hypothalamic nuclei, and subsequently, a significant increase in later hours as compared to control values. At the same time, ACTH induced a significant shift in maximum and minimum values of cytoplasmic RNA level in SON and AN neurocytes, as compared with control material.

In sexually mature male and femaleRana temporaria L. frogs of similar body length caught in their natural habitat in seven periods of their life, the nuclear volume was measured in subfornical organ (SFO) neurocytes containing lipofuscin pigment (LFP). Content of pigment was also determined. The nuclear volume in SFO neurocytes containing LFP as well as the content of pigment were found to undergo a distinct fluctuation in thecourseof the year. The largest volume of the nuclei was observed during the period immediately preceding the breeding period in males and females (1st decade of March), and the lowest volume in the middle of the period of active life (2nd decade of July). Analogous changes in the content of lipofuscin were observed in the course of the year. The problem is discussed whether lipofuscins, aside from their metabolic character, also play a part in storage and secretory function in amphibians.

Using various staining techniques and methods, the following cells were differentiated from pars distalis of the pituitary gland in the mouse: corticotropic, somatotropic, lactotropic, thyrotropic and gonadotropic cells.Diurnal activity of the differentiated cells in pars distalis of the pituitary gland was determined by the method of karyometry.The karyometric analysis showed the existence of a distinct diurnal rhythm in nuclear volume in all five types of the differentiated cells in both sexes.

Sexually mature male and femaleRana esculenta L. were captured in their natural habitat in six phases of the annual cycle. Nuclear volumes of neurocytes in the ventral lateral septum (VLS) were found to fluctuate distinctly in the course of the year. In both sexes nuclear volumes of neurocytes were maximal in the phases preceding the breeding season (3rd decade of January, and 1st decadeof April), and minimal in the phaseat the beginning of hibernation (3rd decade of October). The results lead to the assumption that the VLS ofRana esculenta may have an active role in controlling gonadotropin release.

In sexually mature male and female mice the percentage of neurocytes containing lipofuscin pigment (LFP) has been specified as well as the accumulation of this pigment in the para-ventricular nucleus (PVN), the arcuate nucleus (AN), and the supraoptic nucleus (SON). It has been found that the number of neurocytes containing LFP as well as the accumulation of LFP in PVN, AN and SON show essential diurnal changes. The greatest number of neurocytes containing LFP and also the concentration of this pigment in PVN, AN and SON were observed at 18.00 h, both in males and in females, and the smallest number at 6.00 h.

The nuclear volume in cells of the subfornical organ of Rana esculenta shows a cyclic annual size change. It is pronounced both in the so-called Gomori-positive cells and the ependymal covering of the organ. There appears a maximum in April in the epen-dyma and in May in the Gomori-positive cells. The amount of neurosecretory material present in the subependymal layer also shows a maximum in April.

Sexually mature male and female Rana esculenta L. were captured in their natural habitat in six phases of the annual cycle. Nuclear volumes in APOA cells were found to fluctuate distinctly in the course of the year. In both sexes nuclear volumes were maximal in the phases preceding the breeding season (IIIrd decade of January, and 1st decade of April), and minimal throughout the phases of active life (IIIrd decade of May, IInd decade of July, and 1st decade of September). No aldehydefuchsin or Gomori-positive material was found in the APOA perikaryons.

A very distinct annual cycle of activity, as judged from nuclear volume changes, has been found in glandular cells of the pars tuberalis of the hypophysis and neurons in the nucleus tuberis hypothalami of adult green frogs (Rana esculenta). The changes are very similar at both sites, a single maximum in April and a single minimum in September being observed. Ependymal tanycy tes of the region which was investigated showed only very moderate activity changes. No sex differences were found with regard to the character of the cycle and the amplitude of changes. Only quantitative differences in absolute nuclear volume were found between the two sexes.