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Biomedical subjects

L Horváth

Publications and source records attributed to L Horváth.

At least 19 recordsLinked to original sources
PubMed1992

[False positive results of exercise tests with thallium myocardial scintigraphy].

The authors have examined supposed causes of positive Th-201 stress scintigraphy. Patients were divided into two groups according to the presence of exercise-induced transitory hypoperfusion or in absence of it. In both groups negative coronarograms were verified. Results of two groups were compared according to parameters of the left ventricle function, pulmonary pressure, to the presence of disorder of system stimulus-conduction (LBBB, RBBB), mitral prolapsus, foramen ovale apertum, anomalous coronary anatomy, level of load during exercise, body weight, heart volume-index. Significant difference was found in disorder of left ventricle motion, ejection fraction and in comprehensive value of left ventricle function (F1).

Adult↗
PubMed1992

Effects of calmodulin antagonists on antibody binding to calmodulin. Distinct conformers of calmodulin induced by the binding of drugs.

An indirect enzyme-linked immunosorbent assay has been used to study the interactions between calmodulin and two calmodulin antagonists, trifluoperazine and a neuropeptide isolated from the hypothalamus. The binding of a monospecific anti-calmodulin antibody, raised in rabbit against dinitrophenylated calmodulin, to calmodulin was tested at various concentrations of these drugs under equilibrium conditions. Trifluoperazine at low concentrations stimulated, but at relatively high concentrations inhibited, immunocomplex formation. The neuropeptide displaced the antibody from calmodulin at nanomolar concentrations. Enzyme-linked immunosorbent assays were also carried out with the large tryptic fragments of calmodulin. The results suggest that (i) the C-terminal fragment binds the antibody with an affinity which is comparable with that of intact calmodulin; (ii) the neuropeptide can form complexes with both N- and C-terminal fragments, but with two orders of magnitude less activity in case of the C-terminal fragment; and (iii) trifluorperazine does not stimulate antibody binding to the C-terminal fragment. Therefore the tertiary structure of calmodulin must be intact to ensure long-distance interactions between the binding sites of trifluoperazine, the neuropeptide and the antibody. These interactions may produce distinct conformers of calmodulin which may exhibit altered potency, not only for antibody binding but also for stimulation/inhibition of target enzymes.

Animals↗
PubMed1991

Quantitative evaluation of indirect ELISA. Effect of calmodulin antagonists on antibody binding to calmodulin.

A simple linearization procedure has been developed to determine the apparent dissociation constant of the interaction between antigen and antibody from the data of indirect, non-competitive enzyme-linked immunosorbent assays (ELISA). Applying this dissociation constant the binding constant of ligands to antigen can be determined and the quantitative evaluation of the competitive ELISA experiments makes it possible to analyse the affinity of antibody to antigen on the surface and in solution. The binding of the monospecific anti-calmodulin antibody to calmodulin and to solid-phase bound calmodulin has been tested by non-competitive and competitive assays. We have developed an experimental system where binding of the antibody to the solid-phase bound calmodulin has been studied under equilibrium conditions. Competitive ELISA experiments showed that the affinity of antibody to calmodulin on the surface and in solution was almost the same. The binding constant of a hypothalamic neuropeptide to calmodulin was determined using the quantitative ELISA approach. The neuropeptide was found to be of very high inhibitory potency (Kd = 2 nM) and competed with the antibody for calmodulin binding. This simple and sensitive procedure is suitable for screening molecules with anti-calmodulin activity and comparing their efficacy.

Antigen-Antibody Reactions↗
PubMed1991

[Angina pectoris, provocable by exercise, and silent myocardial ischemia in the light of results of coronary angiography].

Correlation between coronary anatomy and the presence or absence of chest pain was studied during bicycle exercise testing in 101 patients. All of them had significant ST segment depression during the stress test. ECG changes were accompanied by chest pain in 66 patients (group A). 35 patients were free of symptoms (group B). Coronary arteriography showed significant stenosis of one or more coronary artery branch in 50 patients of group A, and in 24 patients of group B, the difference was not significant statistically. The presence or absence of chest pain weren't valuable markers in the differential diagnosis of true and false positive ST segment depression. Frequency of three-vessel disease was significantly higher in group A (14 cases), than in the other group (1 case). In conclusion, if a significant ST segment depression occurs during exercise stress either with or without anginal pain coronary arteriography is recommended to perform.

Angina Pectoris↗
PubMed1990

Calmodulin is a potent target for new hypothalamic neuropeptides.

Recently, five glycopeptides with coronaro-constrictory properties were isolated from bovine hypothalamus [(1988) Neurochemistry (USSR) 7, 519-524]. Calmodulin has been recognized in our laboratory as a target protein for the neuropeptides isolated from hypothalamus. The results of indirect enzyme-linked immunosorbent assay have shown that the new hypothalamic neuropeptides antagonize with the monospecific anti-calmodulin antibody for calmodulin binding although they are not fragments of calmodulin. The inhibitory potency of the peptides is dependent on their concentration and the length of the polypeptide chain. Four out of five peptides are effective in nM concentration range. Ca2+ stimulates the binding of peptides to calmodulin; however, immunocomplex can be formed in the absence of Ca2+ as well. The effects of trifluoperazine and peptides on the calmodulin/antibody interaction are not additive, suggesting the cooperativity between the binding sites on calmodulin. Under physiological conditions the presence of the peptides could produce distinct conformers of calmodulin which may exhibit altered potency for stimulation/inhibition of target enzymes.

Animals↗
PubMed1990

[Septal Q wave responses to exertion in the diagnosis of proximal stenosis of the anterior descending coronary artery].

In 29 patients with coronary artery disease (CAD) involving the proximal segment of left anterior descending coronary artery (LAD) and in 25 patients with normal coronary anatomy (control group) Q wave amplitude changes were studied in response to exercise with bicycle and treadmill. Decrease of the Q wave amplitude was observed only in the patient group. Increase in amplitude was found only in the control group. The sensitivity of bicycle test for a significant ST segment depression was 51.7%. The same value, obtained by treadmill exercise was 50%. When either a significant ST depression or decrease of Q wave amplitude was evaluated as an abnormal response to exercise, the sensitivity was 62% (bicycle) and 65% (treadmill). Taking both ST segment depression and reduction of Q wave amplitude, an increased sensitivity of exercise ECG examination can ben attained.

Coronary Disease↗
PubMed1990

[Stress tolerance in patients with right ventricular infarct during the rehabilitation period].

199 patients with myocardial infarction were divided into 4 groups according to the localisation of necrosis (anterior, inferior, anterior + right ventricle, inferior + right ventricle). Exercise capacity was determined by bicycle ergometer test at the beginning of rehabilitation and 3 weeks later. Exercise capacity and ejection fraction were better in case of inferior comparing with anterior infarction. There was no significant change in exercise capacity whether inferior or anterior left ventricle necrosis was accompanied by right ventricle infarction. In chronic phase of myocardial infarction exercise capacity of patients is not influenced by right ventricle necrosis accompanied by left ventricle infarction.

Exercise Test↗
PubMed1990

[The normal right-side electrocardiogram].

QRS complex, ST segment and T wave were investigated in V1R--V8R right chest wall leads in 122 healthy individuals (76 women, 46 men, mean age: 36.8 years). There was no Q wave in V1-3R. Going towards V8R, occurrence of QR and QS complexes increased. R/S ratio was the highest in V8R, while second r wave (r') was found to be most frequent (in 20.5%) in V6R. ST elevation at 80 msec after J point was found in all right chest wall leads, most frequently (in 91%) in V2R. All three forms of T wave morphology (positive, negative, isoelectric) were observed in these leads.

Adult↗
PubMed1989

Immobilization of pig muscle aldolase on a silica-based support.

Pig muscle aldolase was covalently attached to a silica-based support possessing aldehyde functional groups. The activity of the immobilized enzyme was 37 U/g solid, and the specific activity calculated on a bound protein basis was 1.9 U/mg protein. The optimum pH for the catalytic activity was pH 7.5. The apparent optimum temperature was found to be 45 degrees C. The Km app value of the immobilized aldolase with D-fructose 1,6-diphosphate as substrate was 1.25 X 10(-4) M. The conformational stability was improved by the immobilization. The immobilized aldolase was used for the continuous splitting of D-fructose 1,6-diphosphate.

Animals↗
PubMed1989

Follicular cells of tonsils metabolise more deoxycytidine than other cell populations.

Nine subpopulations of tonsillar lymphocytes and the unseparated cells were compared in their utilization of exogenous deoxycytidine ([5-3H]CdR) and thymidine ([3H]TdR). Uptake phosphorylation and incorporation of labeled precursors were determined in B and T lymphocytes, in low density (LD; enriched in S phase cells) and in high density (HD; enriched in G0/G1 phase cells) cell fractions as well as in LD and HD subfractions of B and T lymphocytes, and in cells isolated from follicles of tonsils. As expected, LD cells and B lymphocytes were more active in TdR incorporation than HD cells and T lymphocytes. However, the ratio of [5-3H]CdR to [3H]TdR in their total phosphorylation and incorporation into DNA was much lower than the expected value of 1: about 0.5 for total phosphorylation and about 0.3 for incorporation in all subpopulations, except for the follicular cells, where these ratios were 1.0 and 0.7, respectively. These results show that the relative utilization of the two pyrimidine deoxyribonucleoside precursors varies among different lymphocyte subpopulations. However, this variation is not due to the different rate of DNA synthesis; rather, it depends on the differentiation stage of lymphocytes occurring in the germinal center of the follicles.

Cell Differentiation↗
PubMed1989

[A case presenting differential diagnostic difficulties in eosinophilic gastritis].

The diagnosis of eosinophilic gastritis in a 45 year old man was definitely established only through laparotomy, after inconclusive radiological, endoscopical and biopsy histological findings. The diagnostic difficulties in this particular case were characteristic for this condition, as evident from the literature.

Diagnosis, Differential↗
PubMed1987

Surgical treatment of renovascular hypertension.

Unilateral stenosis of the renal artery was verified by angiography in 34 patients with hypertension. The cause-effect relationship between elevated blood pressure and stenosis of the renal artery was proved by detailed renin studies (basic plasma renin activity, plasma renin activity following orthostatic and diuretic stimulation, renal vein renin activity). Surgical treatment was applied in 39 cases: they were aortorenal bypass in 9, autotransplantation in 7, patch graft in 2, denervation in 2, decompression in 3 and nephrectomy in 16 cases. Six months following the operation, 68.4% of the patients were normotensive without drugs and 18.4% of them with a reduced dose of drugs. To achieve normotension preoperative treatment had to be continued only in 13.2% of the patients. Two to four years postoperatively, 29 patients were subjected to control examinations and in 23 cases also to angiography. Restenosis was observed in 4 patients (17.4%). As a result of surgical treatment, the increased response to hyperreninaemia and to various stimuli decreased. Based on the control examinations, 58.7% of the patients could be considered to be cured.

Adolescent↗
PubMed1987

[ECG and coronarographic signs of an anterior wall myocardial infarct accompanied by a right ventricular infarct in the rehabilitation phase].

QRS-complex and ST-segment were analyzed by ECG using 12 routine leads in three right chest wall leads (V3R, V4R, V5R) in patients with chronic anterior wall myocardial infarction. A QRS-complex was found in leads V3R and V4R in proximal occlusion of the LAD in all (n = 22) but four patients, where retrograde filling of the septal branch of the LAD was observed. When the medial LAD was occluded (n = 13), rS-complex was present in the right chest wall leads. Similar ECG findings were revealed in normal coronary arteries (n = 46). QS-complex in leads V3R and V4R refers to right ventricle infarction in the chronic phase of anterior wall myocardial infarction, when the proximal LAD is occluded.

Adolescent↗