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Biomedical subjects

K Hegedüs

Publications and source records attributed to K Hegedüs.

At least 19 recordsLinked to original sources
PubMed1997

Effect of i.v. dipyridamole on cerebral blood flow, blood pressure, plasma adenosine and cAMP levels in rabbits.

In response to intravenous administration of dipyridamole, the quantitative and temporal changes in plasma adenosine and cyclic AMP (cAMP) levels in relation to the changes in cerebral blood flow (CBF) and mean arterial blood pressure (MABP) have not been studied. Therefore, we investigated simultaneously the changes in CBF (hydrogen and thermal clearance methods), MABP, plasma adenosine (HPLC) and cAMP (radioimmunoassay) levels for 1 h after intravenous injection of 0.7 and 1.4 mg/kg dipyridamole in rabbits. In separate experiments, only plasma adenosine concentrations were measured to determine how and for how long intravenous administration of 0.7 mg/kg dipyridamole is able to inhibit the removal of plasma adenosine. Dipyridamole decreased MABP, increased plasma adenosine and cAMP levels in a dose-dependent manner. The dose-dependency of increases in CBF could not be demonstrated owing to the marked hypotension. The increase in plasma adenosine concentrations was biphasic. The first peak could be detected at the end of the dipyridamole injection. The second peak occurred 20 min after drug administration, simultaneously with the maximal increases in plasma cAMP level and CBF, whereas the maximal fall in MABP developed earlier. Intravenous administration of 0.7 mg/kg dipyridamole inhibited adenosine uptake only by 25%, which lasted less than 10 min. We concluded that intravenously given dipyridamole is responsible only for the initial short-lasting elevation of plasma adenosine concentration, and is able to induce vasodilation without either dipyridamole itself or adenosine necessarily gaining access to the muscular layer.

Adenosine↗
PubMed1995

Beneficial vascular and metabolic effects of cobalt-ATP in spontaneously hypertensive rabbits with diffuse chronic cerebral ischaemia.

The in vivo effects of adenosine triphosphate (ATP) have not been investigated in cerebrovascular diseases. The use of the long-acting cobalt-ATP complex (Co-ATP) permits us to observe the effects of ATP without the influence of its metabolites. This study was designed to compare the effects of intravenous Co-ATP on the cerebral blood flow (CBF), polarographically detected oxygen currents (O2a), mean arterial blood pressure (MABP), heart rate, respiration rate, cerebral electrical activity, arterial blood gases, pH, and glucose in 13 normotensive (NT) rabbits to those in 14 stroke-prone spontaneously hypertensive (HT) animals. CBF was measured by the hydrogen and heat clearance methods. In response to Co-ATP, MABP decreased and CBF increased significantly in both groups. The decrease in MABP was more marked in HT rabbits, while CBF response was 25% smaller than in NT animals. The ratio of O2a to CBF diminished moderately and simultaneously with the CBF increase in NT rabbits. In HT rabbits, the decrease in O2a/CBF was larger and began when CBF response reached its maximum. We suggest that despite the restricted CBF response, long-acting ATP should still be taken into consideration as a supplementary treatment of hypertensive encephalopathy because of its beneficial effects on cerebral metabolism and hypertension.

Adenosine Triphosphate↗
PubMed1993

Effects of dipyridamole in spontaneously hypertensive rabbits with diffuse chronic cerebral ischemia.

The effect of intravenous dipyridamole (0.7 mg/kg) on cerebral blood flow (CBF), mean arterial blood pressure (MABP), heart rate, respiration rate, cerebral electrical activity, arterial blood gases, pH, and glucose was investigated in 14 normotensive and 14 stroke-prone spontaneously hypertensive anesthetized rabbits. CBF was measured by hydrogen and heat clearance. In both groups, MABP decreased (normotensive: -24 mm Hg, hypertensive: -47 mm Hg; ANOVA: P < 0.0001) and CBF increased (normotensive: +59 ml/100 g/min, hypertensive: +72 ml/100 g/min; ANOVA: P < 0.0002). CBF returned to the initial level 21 min later in hypertensive than in normotensive rabbits. Changes in other parameters were insignificant. In additional experiments, 30 mg/kg theophylline entirely prevented the cerebral vasodilator and systemic hypotensive effects of dipyridamole in both normotensive and hypertensive rabbits. We conclude that, in stroke-prone spontaneously hypertensive rabbits, the longer-lasting and larger CBF increase in response to dipyridamole may be attributed to reversible functional changes in the cerebral vasculature resulting from hypertension.

Analysis of Variance↗
PubMed1992

Effects of carbon dioxide inhalation on cerebral blood flow and oxygen tissue level in spontaneously hypertensive rabbits.

BACKGROUND AND PURPOSE: Because previous studies have yielded conflicting results, this study was designed to investigate the efficiency of cerebrovascular reactivity to carbon dioxide in hypertension associated with moderate diffuse cerebral ischemic lesions. METHODS: The effects of carbon dioxide inhalation on mean arterial blood pressure, heart and respiration rates, cerebral cortical blood flow, polarographically detected oxygen currents (oxygen availability), and cerebral electrical activity were compared in 14 spontaneously hypertensive and 16 normotensive rabbits anesthetized with urethane and alpha-chloralose. Blood flow was measured with the hydrogen clearance and thermal clearance methods. RESULTS: In the resting state the frequency of electrical activity shifted to slower components, the levels of oxygen availability and cerebral blood flow were lower (p less than 0.01), and the ratio of the two latter parameters was greater (p less than 0.01) in hypertensive rabbits than in normotensive animals. Carbon dioxide inhalation induced more marked increases in cerebral blood flow, respiration rate, and oxygen availability in hypertensive (p less than 0.01) than in normotensive (p less than 0.05) rabbits. The ratio of oxygen availability to cerebral blood flow decreased (p less than 0.01) in the former and did not change significantly in the latter group. The carbon dioxide-induced rise in blood flow was also slower and more protracted in hypertensive rabbits (p less than 0.01). Histological investigation revealed groups of neurons with ischemic changes in the cortex of the hypertensive rabbits. CONCLUSIONS: We suggest that in hypertensive rabbits the mild multiple ischemic lesions are the basis of functional disturbances, including reduced resting cerebral blood flow, greater oxygen tissue level, slower response to carbon dioxide, and greater vasodilatory capacity.

Administration, Inhalation↗
PubMed1991

Difference between the cerebrovascular effect of purinergic Co-ATP and that of the cholinesterase inhibitor, physostigmine, in vivo.

Development of the cerebrovascular effect of cobalt-ATP was compared to that of physostigmine in 34 anesthetized rabbits. The resting cortical cerebral blood flow (CBF) was estimated from the H2 clearance and the CBF changes by the heat clearance method. Systemic blood pressure, heart and respiratory rate and cerebral electrical activity were recorded simultaneously. In addition, we measured arterial glucose concentration, pH, PaO2 and PaCO2. Both drugs were found to induce a significant increase in CBF. However, the degree of the CBF increase induced by Co-ATP was inversely related, while that induced by physostigmine was directly related to both the baseline level of CBF and the value of PaCO2. We conclude that the cerebrovascular effect of ATP depends mainly on vessel tone, while the effect of physostigmine is related to the level of PaCO2.

Adenosine Triphosphate↗
PubMed1990

Myelinoclastic diffuse sclerosis: a case report.

The clinical features and pathological findings of a patient with myelinoclastic diffuse sclerosis, corresponding to those described by Schilder in 1912, are reported. The course of the disease, having lasted for ten years, was interrupted by periods of partial remissions. Peripheral nerve involvement was also found.

Adult↗
PubMed1988

Cerebral ischaemia produced by homologous blood clot emboli in rabbit.

In 40 rabbits cerebral ischaemia was induced by autologous blood clot emboli injected into the middle cerebral artery. Autologous blood clot formed spontaneously (within 2 h) in a catheter fixed in the internal carotid artery. The effects of embolization were investigated on arterial blood pressure, respiration, local cerebral blood flow, locally available O2 (aO2), steady (DC) potentials and EEG. After embolization the blood pressure and the frequency of respiration decreased transiently. On the embolized side the local cerebral blood flow, aO2, the frequency and amplitude of the EEG diminished markedly and the DC potentials shifted to negative. Similar but less marked and short-lasting changes could be seen on the contralateral side. Pathological examination of the brains revealed extensive infarction with haemorrhagic components. The technique is a promising method for inducing stroke experimentally and offers various ways for its thorough investigation.

Animals↗
PubMed1988

Akinetic mutism associated with bicingular lesions: clinicopathological and functional anatomical correlates.

The clinical symptoms and neuropathological findings of three patients suffering from akinetic mutism were summarized. The patients showed almost absolute mutism and immobility and were unable to communicate in any way. The neurological signs varied from case to case. The pathological features common to all of the cases were bilateral lesions of the rostral part of the anterior cingulate gyri which overlapped onto the neighboring supplementary motor area, while differing as regards other damage. With the help of more recent neurobiochemical findings we tried to analyze the pathomechanism of akinetic mutism on the basis of the structures damaged. There seems to be an anatomic correspondence between the mesolimbocortical dopaminergic system and the circumscribed bilateral lesions of the medial prefrontal cortex. The study suggests that damage of the mesolimbocortical dopaminergic terminal fields in the anteromedial frontal cortex is essential for this specific type of akinetic mutism.

Aged↗
PubMed1988

A new model for inducing transient cerebral ischemia and subsequent reperfusion in rabbits without craniectomy.

An artificial ball removable by an attached fiber was injected into the middle cerebral artery (MCA) of 16 rabbits, allowing the study of transient (5, 10, 15, or 30 minutes) cerebral ischemia without craniectomy. Measurements of available oxygen (aO2) in the ischemic core (the ventral part of the temporal area) followed by histologic examination verified the embolization. Electroencephalographic power spectra and steady (direct current) potentials were recorded bilaterally on the convexity remote from the actual lesion but still supplied by the MCA. Local cerebral blood flow and aO2 in the border zone between the anterior cerebral artery and the occluded MCA were measured. Embolization caused typical ischemic changes ipsilaterally and alterations characteristic of diaschisis contralaterally. Extreme border zone hyperemia developed without significant aO2 changes in the same region. Restoration of circulation via the circle of Willis induced gradual normalization. Our model for controlled embolization and recirculation proved suitable for detailed studies of the complex changes in brain function caused by transient ischemia.

Animals↗
PubMed1988

The effects of hypertension on the wall of the large intracranial arteries with special reference to the changes of some connective tissue elements.

The effect of hypertension on the wall of the major cerebral arteries of 62 patients was investigated at the light microscopical level. This series does not include patients with atherosclerosis of the large intracranial arteries. In hypertensive individuals the intracranial arteries showed concentric intimal thickening. Furthermore, the collagenous fibers occurred in the media as early as in the third decade of life in place of reticular fibers. On the basis of literary data and our findings one may suppose that under permanent mechanical influence the arterial smooth muscle cells synthetize predominantly collagenous fibers instead of reticular fibers.

Adult↗
PubMed1987

Anatomical patterns of hypoplastic posterior communicating arteries and their implications for cerebrovascular diseases.

A total of 114 undersized posterior communicating arteries (PCoA-s, external diameter less than 1 mm) and 126 larger ones were investigated histologically. Microscopic examination of hypoplastic PCoA-s revealed five different structural patterns. Two of them showed microscopic appearances characteristic of intracranial arteries seen in adults or newborns without vascular disease. Two other types resembled the histologic picture of Moya Moya disease. The last type was thin-walled and dilated. All PCoA-s larger than 1 mm displayed the adult pattern. The PCoA-s with the Moya Moya-like structure and the thin-walled, dilated pattern contained unusually few reticular fibers. It is supposed that Moya Moya disease may be restricted to the PCoA-s. Further, the types of hypoplastic PCoA-s with reticular fiber deficiency are most probably the source of the so-called unexplained subarachnoid hemorrhage regardless of the presence of infundibular widening. The latter statement stems from the observation that the structure of junctional dilatation does not differ from that of other segments of the artery that exhibit this alteration.

Adolescent↗
PubMed1986

On the pattern of reticular fibers in the intracranial arteries of mature newborn with and without intracranial hemorrhage.

A detailed histological study was carried out on the major intracranial arteries of 20 mature newborn. A substantial reduction of the reticular fiber content within the wall of the cerebral arteries was observed in all samples originating from infants with intracranial hemorrhage. No other differences occurred when comparisons were made using the conventional staining methods on the vessels from the ten newborn with hemorrhage and the ten others without bleeding. These data indicate that the structural deficiency of the brain vasculature provides the morphological basis for the development of intracranial hemorrhages in the term newborn.

Arteries↗