Abstract. As a part of the nitroso signalling pathway, nitroso-compounds serve as stores and carriers of NO; as part of the sulphide signalling pathway, bound sulfane-sulphur compounds serve as stores and carriers of H 2 S. Here we hypothesise a coupled sulphide-nitroso signalling pathway, in which H 2 S plays a main role. H 2 S releases NO from the endogenous S-nitroso-compounds nitrosocysteine, nitroso-acetylcysteine and nitroso-albumin. Relaxation of noradrenaline-precontracted aortic rings by H 2 S is also enhanced in the presence of nitroso-albumin, which may implicate the involvement of the nitroso signalling pathway. Pretreatment of albumin, cysteine, N-acetylcysteine and lipids with H 2 S results in binding of sulphur to these compounds creating thus new-modified sulphur compounds that release NO from nitroso-compounds directly and/or through released H 2 S, which suggests sulphide-nitroso signalling pathway participation. This hypothesis is supported by the observation that the pretreatment of noradrenaline-precontracted aortic rings with H 2 S significantly enhanced relaxation induced by nitroso-glutathione in the absence of H 2 S. We assume that the NO release from nitroso-compounds directly by H 2 S or indirectly by the H 2 S-induced sulphur-bound compounds represents coupled sulphide-nitroso signalling, which may explain some of the numerous biological effects of H 2 S that are shared with NO.

Nucleolar ultrastrure was studied in fully grown human oocytes obtained from multilaminar preantral follicles and from follicles at different stages of antrum formation. Selective staining for ribonucleoproteins and 3H‐uridine labeling were used in attempt to better understand the nature and functional significance of homogeneous dense nucleoli found in oocytes from large antral follicles. There was an apparent increase in the radio of nucleonema to nucleolar interstices, accompanied by a gradual degranulation of the nucleolonema during early stages of antrum fromation. The process of nucleolar homogenization continued in oocytes from medium‐size antralfollicles, island of more tightly packed fibrils being hybothesized to represent persisting active transcription units. Entirely filamentous and homogeneous nucleoli were typical for oocytes from large antral follicles. They were demonstrated to ribonucleoprotein filaments embedded in pale‐ staining matrix. They were demonstrated to contain newly synthesized RNA after a 30‐min pulse with 3H‐uridine. The described nucleolar transformations are interpreted as acorrelate of nucleolar transition from a site of RNA synthesis into a site of RNA Storage during in human oocyte preovulatory development.

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The age-dependent differences in basic cardiovascular parameters, geometry and structure of coronary arteries between Wistar and spontaneously hypertensive rats (SHR) were evaluated. SHR of the age 3-, 9-, 17-, and 52-week and age-matched Wistar rats were used. Blood pressure (BP) was measured by the plethysmographic method. Animals were perfused with a glutaraldehyde fixative under pressure of 90 mmHg (3-week-old) and 120 mmHg (9-, 17-, 52-week-old). Coronary arteries were processed for electron microscopy. The proportions and cross sectional areas (CSA) of extracellular matrix in intima and media, endothelial and muscle cells were determined by point counting method. Cardiac hypertrophy and except of 3-week-old rats also BP increase and coronary wall hypertrophy was found in all ontogenic periods in SHR compared to Wistar rats. Arterial wall hypertrophy was evoked by increase of CSA of medial extracellular matrix and smooth muscle cells. In 52-week-old SHR, CSA of muscle cells did not differ from that in 17-week-old SHR but the CSA of intimal and medial extracellular matrix significantly increased. The CSA of endothelial cells and CSA of intimal extracellular matrix were increased only in 52-week-old SHR. The independency between BP and trophicity of individual components of the coronary wall during ontogeny of SHR was documented.

Abstract. The status of nitric oxide (NO) in spontaneously hypertensive rats (SHR) is unclear and its bioavailability may be affected by imbalance with reactive oxygen species. We studied cardiovascular effects of an NO donor, pentaerythrityl tetranitrate (PETN) in SHR. We used Wistar rats, SHR and SHR treated with PETN (100 mg/kg/day). After six weeks, myocardium and aorta from each group were taken for biochemical and iliac artery for functional and morphological study. Long-term administration of PETN to SHR increased cGMP level in platelets and did not affect blood pressure. In myocardium, the therapy resulted in a decrease in cardiac hypertrophy and MDA level, and the increased antioxidant enzyme activity of superoxide dismutase (SOD) and glutathione peroxidase (GPx). In aorta, PETN decreased the NO-synthase activity and had no affect on the enzyme activities of SOD and GPx or on MDA level. In the iliac artery, the endothelium-dependent relaxation to acetylcholine was slightly improved and the maximum vasoconstriction to noradrenaline was decreased. Wall thickness, cross-sectional area, inner diameter, and wall thickness/ inner diameter measured after perfusion fixation (120 mmHg) were not affected. The small effect of PETN on cardiovascular system suggests that NO deficiency is probably not the main cause of pathological alterations in SHR.