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Biomedical subjects

E Barta

Publications and source records attributed to E Barta.

At least 19 recordsLinked to original sources
PubMed1992

Heterogeneity in geometrical alterations of main branches of left coronary artery induced by increase in ventricle volume.

With the use of ultrasound technique, segment length and diameter of ramus circumflexus (RC) and ramus interventricularis anterior (RIA) in the dog heart, placed in a bath, were monitored under constant pressure. When the left and/or right ventricular volume was increased by 150% of the normal diastolic filling, segment length of RC increased by 2.54 +/- 0.17 and 2.15 +/- 0.06%, respectively, and diameter of RC decreased by 4.72 +/- 0.20% and by 4.60 +/- 0.20%, respectively. The same filling of the left and/or right ventricle induced in the proximal third of RIA an increase in segment length by 11.40 +/- 0.55 and 12.2 +/- 0.42%, respectively, and a decrease in diameter by 9.41 +/- 0.42% and by 10.01 +/- 0.31%, respectively. The latter values of RIA were significantly higher (P less than 0.001) than those registered in RC. The deformations of RIA decreased toward the periphery of the vessel. By the fact that conduit coronary artery tracks instantaneously the increase of the volume of the left and right ventricle, its contribution to the total coronary resistance increases dynamically. With the ventricular volume increased by 150%, the RC contributes to the total coronary resistance by 14% and RIA in the proximal part contributes by 23%, with values significantly higher than control (10%) (Malindzak, G. S. In: The Coronary Artery. London: Croom Helm, 1982, p. 241-267). The results imply a methodical consequence, namely that the diameter of the respective coronary artery is an index of smooth muscle activity only if both perfusion pressure and volume of the heart are maintained constant.

Animals↗
PubMed1991

Complex pattern of alternative splicing generates unusual diversity in the leader sequence of the chicken link protein mRNA.

We report here the isolation of the 5' end and the promoter region of the gene for chicken cartilage link protein, and demonstrate extensive heterogeneity of the leader sequence arising from differential utilization of multiple splice sites within the 5'-most exon. The 500-base pairs (bp) exon 1 consists of solely untranslated sequence and is followed by an intron greater than 33 kilobase pairs (kb). Together, the five exons predict a gene size longer than 100 kb. Multiple transcription initiation sites were mapped 34, 46, 56, 66 and 76 bp downstream of a TATA-like motif. Sequence analysis revealed that in addition to the non-spliced variant, multiple mRNA species were generated by alternative splicing resulting in the exclusion of 92, 166, 170, 174 and 263 nucleotides (nt), respectively, from exon 1. Polymerase chain reaction confirmed the existence of various splice forms, and showed cell type- and developmental stage-specific expression for one group of them. Secondary structure predictions indicated that the leaders of the splice forms could form stable hairpin structures with different free energies of formation (up to delta G = -110 kcal/mol), suggesting translational control. The splice variant detected in the largest amount had the least stable predicted hairpin (delta G = -31.7 kcal/mol).

Animals↗
PubMed1990

Identification of positive and negative regulatory regions controlling expression of the cartilage matrix protein gene.

A complex pattern of regulation of the cartilage matrix protein gene was revealed by transient expression experiments. A minimal promoter from positions -15 to +64 functioned in chondrocytes and fibroblasts. An enhancer located in the first intron exerted chondrocyte-specific stimulation on the minimal promoter activity. The same fragment, however, had a negative effect in fibroblasts. Between -334 and -15, a silencer was found which inhibited the gene expression driven from its homologous as well as heterologous promoters both in chondrocytes and fibroblasts. Additional positive and negative control regions were mapped further upstream of the promoter.

Animals↗
PubMed1990

[Perioperative myocardial infarct in association with surgical treatment of coronary heart disease].

Perioperative myocardial infarction is a major complication of revascularization surgery of the heart which can negatively affect both the quality and duration of the patient's life. The aim of the paper is to contribute to the understanding of the problem which involves the definition, incidence, pathogenesis, diagnosis, complications, therapy and prognosis of perioperative myocardial infarction. One of the basic factors implicated in the development of perioperative derangement of the cardiac muscle is closely analyzed, namely insufficient protection of the myocardium with subsequent ischemia-reperfusion induced myocardial damage. Pitfalls of electrocardiographic diagnosis are pointed out and the rather complicated interpretation of increased enzyme levels following cardiac surgery is discussed. Complications, management, as well as early and late prognosis of patients with perioperative myocardial infarction are also dealt with.

Coronary Disease↗
PubMed1989

Protective effect of oestradiol on the heart of rats exposed to acute ischaemia.

Sex-related differences in mortality from ischaemic heart disease are attributed chiefly to difference in the incidence of atherosclerosis. Little attention has been paid to the influence of sex hormones on resistance of the myocardium itself to acute ischaemia. Experiments on rats showed that isolated female hearts were more resistant than male hearts. A period of eight weeks spent at an altitude of 1,350 m raised heart resistance only in males. Conversely, gonadectomy abruptly reduced the resistance of the male heart to ischaemia, especially under conditions of mild altitude hypoxia. The administration of oestradiol to gonadectomized male rats largely abolished the disturbance caused by isolated gonadectomy. Since coronary vasoconstriction and vasospasm lead to temporary ischaemia and even to infarction, the above effect of the sex hormones may play a role in the increased incidence of heart attacks after the gonads have ceased to function.

Animals↗
PubMed1989

The influence of exaprolol upon the ischaemic rat heart and its interaction with sarcolemmal (Na+ + K+)-ATPase.

The capability of cyclohexylphenol exaprolol of protecting the ischaemic myocardium during ischaemic cardiac arrest was assessed in the isolated working rat heart. Exaprolol added to the perfusion medium in a dose of 10(-7) mol.l-1 only minimally influenced the left ventricular function (reduced the stroke volume by 18.84% and cardiac output by 14.63%). The hearts were subjected to global ischaemia for 75 min at 26 degrees C and subsequently reperfused for 60 min at 37 degrees C. The recovery of left ventricular function following reperfusion, expressed as a percentage of preischaemic functional performance was used as an indicator of the ischaemic tolerance of the heart. The effect of exaprolol on sarcolemmal (Na+ + K+)-, Mg2+- and Ca2+-ATPase activities was also examined. Exaprolol-pretreated hearts revealed better postischaemic recovery of the left ventricular dP/dt max and stroke volume as well as improved efficiency in the transformation of chemical energy to mechanical work. Exaprolol in 10(-4) mol.l-1 concentration significantly stimulated the specific activity of sarcolemmal (Na+ + K+)-ATPase. Possible mechanisms of the salutary effect of exaprolol on the ischaemic heart are discussed.

Adrenergic beta-Antagonists↗
PubMed1988

Age-dependent influence of a moderate altitude (1,350 m) on the rat cardiopulmonary system.

The aim of the study was to determine whether a moderate altitude (1,350 m, Strbské Pleso, High Tatras) would act as a hypoxic stimulus on the cardiopulmonary system of young and adult rats. We used three experimental groups of animals differing in the duration of time for which they were kept at the given altitude (60 and 120 days) and the age at which they were acclimatized (from the 5th and the 60th day of life). The controls were kept at an altitude of 200 m (Prague). We found that an altitude of 1,350 m produced a significant increase in blood pressure in the lesser circulation; this response did not depend on the animals' age. Right ventricular enlargement occurred at the same time and was more pronounced in rats which had been acclimatized from infancy. The systemic blood pressure fell mildly, but significantly, only in animals exposed to altitude from adulthood; elevation of the haematocrit was likewise recorded only in this group. The results show that even a moderate altitude influences the cardiopulmonary system of the rat in a manner characteristic of the effect of chronic hypoxic hypoxia.

Acclimatization↗
PubMed1987

3-D ventricular myocardial electrical excitation: a minimal orthogonal pathways model.

This study is part of our attempt to develop a fast-responding interactive computer simulator of the left ventricle (LV) which describes the spatial and temporal myocardial characteristics and the global performance of the LV, accounting for the continuous interactions between the electrical activation sequence, fiber mechanics, blood perfusion and transmural metabolism and oxygen demand. Here, the activation propagation front throughout the healthy 3-dimensional LV myocardium is simulated in a macro global level by utilizing an analytical model based on the principle of the propagation of the electric activation signal along minimal pathways in an elliptically assumed LV geometry. The Purkinje network dominates the propagation at the endocardial layer while three orthogonal directions of propagation are assumed within the myocardium. The shortest path consists of the geodetic line at the endocardial layer and the normal that connects the endocardium with the point considered. The generated three-dimensional propagation front maps are in fair agreement with reported experimental data. The study thus presents a new approach that permits a quick reconstruction of the 3-D isochrons in a relatively simple but useful model of the normal heart.

Computer Simulation↗
PubMed1987

T-cell depletion of Cercopithecus aethiops monkey bone marrow with Campath-1 monoclonal antibody and complement.

The effectiveness of anti-human monoclonal antibody (Campath 1) plus complement (C') in removal of T-cells from Cercopithecus aethiops monkey bone marrow was studied. Recovery of haemopoietic progenitor cells (CFU-GM) was also investigated in vitro after treatment with Campath-1 plus C'. The results showed that the cell-yield was 37.2 +/- 9.8 after Ficoll separation and 44.2 +/- 13.2% after Campath-1 + + C' treatment. The CFU-GM yields referred to the original total CFU-GM were 88.9 +/- 24.0 and 40.0 +/- 14.3%, respectively. After Campath-1 treatment, CFU-GM per 10(5) bone marrow cells was 269.3 as compared to the pretreatment value of 213.0. In the T-cell-depleted bone marrow suspensions mature T lymphocytes could not be detected. Following cryopreservation more than 70% of CFU-GM could be recovered in T-cell depleted bone marrow suspensions kept in frozen state for two months. Cercopithecus aethiops monkeys can be used as a model to study T-cell depletion of bone marrow with Campath-1 plus C' for studying allogeneic bone marrow transplantation.

Animals↗