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Biomedical subjects

M Ryba

Publications and source records attributed to M Ryba.

At least 37 records · Page 2Linked to original sources
PubMed1991

The respiratory response to magnetic stimulation of the cortex in the unanaesthetized baboon.

Transcranial magnetic stimulation has been used to study cortical input to the respiratory system in unanaesthetized baboons. Single magnetic pulse caused usually a short-latency excitation with subsequent inhibition in stimulated inspiratory phase and change in the amplitude and timing of the respiratory cycle. The results suggest that cortical information is processed by the medullary pattern generator.

Animals↗
PubMed1990

An electron immunocytochemical study of the basilar artery in rabbits after subarachnoid haemorrhage (SAH): a preliminary report.

Vascular endothelial cells of the basilar artery and secretory axons of the neurohypophysis from rabbits after experimental subarachnoid haemorrhage were investigated by postembedding peroxidase--anti-peroxidase technique for electron microscopy to detection of vasopressin (VP). The results indicate an lack of VP-positive endothelial cells in basilar artery, while VP-positive secretory granules were commonly present in the neurohypophysis. The results are discussed in terms of pathophysiological aspect of subarachnoid haemorrhage.

Animals↗
PubMed1989

Immunological method for prediction of progress in neurological deficit in patients with intracranial aneurysm rupture.

Skin tests of nonspecific antigens (immunoskin test Sevac) were performed on patients suffering from intracranial aneurysms, scheduled for surgical clipping. It was found that high antibody titre correlated well with the severity and progress of neurological deficit developing after surgery. This deficit was absent in patients who exhibited low antibody titre in response to the skin test before surgery. These results indicate that the immunological processes may play a role in the development of neurological deficit after neurosurgical procedures. Thus the skin test employed may have prognostic value in predicting neurological deficit following intracranial aneurysm surgery.

Adult↗
PubMed1989

[Nasal obstruction in patients with sleep apnea].

The authors described the clinical signs and consequences of suffocations during sleep apnea. They presented the results of the surgical intervention of nasal obstruction in patients with sleep apnea. The during-all-night examinations of these patients proved the possibility of positive effects of surgical intervention of nasal obstruction in patients with sleep apnea.

Adult↗
PubMed1987

Cooling of ventral medullary intermediate areas and respiration in the cat.

We sought to address the contribution of the ventral medullary intermediate (I) areas to respiratory regulation in the close loop condition. The experiments were done on anesthetized, spontaneously breathing cats. The transient and steady-state neural respiratory output responses to longlasting cooling of the I areas and to vagotomy and hyperoxia performed during the cooling period were investigated. Cooling of the I areas resulted in an initial transient inhibitory response followed by respiratory output increase in the steady-state, provided other respiratory inputs were maintained intact. This investigation calls into question the crucial role of the I areas in regulation of respiration in the close loop condition.

Animals↗
PubMed1985

Brain metabolism in deep controlled hypotension in neurosurgical patients.

Changes in the lactate and pyruvate levels and lactic dehydrogenase activity in the cerebrospinal fluid were followed in 56 patients anaesthetised for neurosurgery. Mean arterial blood pressure (MAP) was reduced in these patients from about 90 to about 35 mm Hg. This allowed to safely place a clip at a brain artery aneurysm. In spite of deep hypotension, ischaemia described by other authors in such cases was never observed. Changes in lactate and pyruvate concentrations, lactate/pyruvate ratio and lactic dehydrogenase activity justify the conclusion that we were dealing with an undisturbed metabolism of the brain tissue. The levels of metabolic parameters, even when increased in hypotension, fell well within the range of physiological values. Attention is called to the fact that partial oxygen pressure in arterial blood during controlled hypotension was about 100 mm Hg, a value considered as limiting to oxygen metabolic transformation within the central nervous system in deep hypotension. We also suggest a different mechanism of passage of lactates and pyruvates through the blood-brain barrier.

Adult↗
PubMed1985

Influence of vagal input on cerebral blood flow in monkeys and dogs after experimental cerebral vasospasm.

Cerebral blood flow (CBF) was a response to experimental subarachnoid haemorrhage (SAH) in four monkeys ,and three dogs. Decrease in CBF was observed in the white and gray matter and in the flow measured within the internal carotid artery as the result of SAH. Bilateral vagotomy enhanced CBF in the gray matter and blood flow in the internal carotid artery to values exceeding the control ones. Results suggest the existence of a receptor susceptible to subarachnoid haemorrhage and connected with vagal nuclei.

Animals↗
PubMed1984

Kinetics of transport and metabolism of 1-beta-D-arabinofuranosylcytosine and structural analogs by everted perfused rat jejunum.

Few reports have dealt with the kinetics and metabolism of AraC and analogs by rat intestine. Using everted rat jejunum with continuous perfusion, it was possible to demonstrate that AraC and Cyd cross the intestinal barrier(s) by a carrier mediated process which was saturable and exhibited fairly good fitting of the flux rate by Michaelis-Menten equation. The transport rate of different analogs was not consistent with the pH-partition theory of membrane transport of drugs being rather dependent on the chemical structure of the nucleoside. A free amino group of cytosine increased the rate of transport within the present series of AraC analogs. There was a detectable deaminase as well as esterase activity towards AraC and its analogs in rat jejunum.

Animals↗
PubMed1984

Structure-intestinal transport and structure-metabolism correlations of some potential cancerostatic pyrimidine nucleosides in isolated rat jejunum.

Both transport and biotransformation processes for a series of pyrimidine nucleobases, ribonucleosides, 2'-deoxyribonucleosides, and acetyl and 5'-substituted derivatives of the cancerostatic agent araC were studied in the isolated everted rat jejunum with a continuous perfusion technique. Metabolic alterations during penetration were assessed by HPLC. 5'-Halogeno and 5'-deoxy derivatives of cytosine nucleosides exhibited higher transport rates and higher stability towards the deamination reaction than did unsubstituted derivatives. Octanol-buffer partition coefficients were estimated for the study compounds, and fragmental constants for the sugar moieties of nucleosides were assessed. With the present study compounds there was no correlation between lipophilicity and transport rate, as previously reported, but there was a correlation between lipophilicity and metabolic alteration of araC derivatives (r = 0.99, n = 5).

Animals↗
PubMed1982

Arterial blood--spinal fluid oxygen gradient diminishes during alkalaemia in hyperoxic man.

We investigated the effect of intravenous sodium bicarbonate (2 mmol x kg-1) on the arterial blood-spinal fluid PO2 gradient in twelve anaesthetized hyperoxaemic human subjects who were in preparation for surgical procedures The steady-state samples of arterial blood and lumbar fluid were withdrawn for the assessment of the acid-base status and electrolyte content in both fluid compartments before and after NaHCO3 injection. We found that NaHCO3 increased the arterial pH and PCO2, and decreased the blood-spinal fluid PO2 gradient significantly. The latter was a result of an increase in spinal fluid PO2 and a decrease in PaO2. The diminished PO2 gradient can be accounted for by the specific effect of carbamate and bicarbonate, distinct from that of pH, lowering the affinity of haemoglobin for oxygen. This might favor the maintenance of an adequate oxygen supply in the brain tissue under unfavorable conditions.

Adult↗
PubMed1982

Study of persistence of maternal antibodies to varicella-zoster virus by indirect haemagglutination, with result control by radioimmunoassay.

The persistence of maternal antibody against varicella-zoster virus was studied by the method of indirect haemagglutination (IH) and a control of the results was performed by radioimmunoassay (RIA). The findings were analysed with reference to the constant half-life of passively acquired IgG and the titre range and frequency of antibodies in 220 persons of fertile age representative of the normal population. Statistical analysis of expected and the experimentally obtained data was performed. Among the normal population, the expectancy is a gradual decrease in maternal IH antibody titres to negativity during the first 10 months of life and 100% sero-negativity by the 11th and 12th month. The experimental data showed a decrease in IH seropositivity from the initial 100% in 1-month infants to 27% in 6-month and 7% in 12-month infants. Nine out of twelve of the experimentally found positive titres in infants during the second half of their first year of life deviated from the normal population sample. The results obtained by both of the methods used were in good agreement.

Antibodies, Viral↗