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Biomedical subjects

A Szabó

Publications and source records attributed to A Szabó.

At least 19 recordsLinked to original sources
PubMed2003

Effects of Ca2+ on catalytic activity and conformation of trypsin and alpha-chymotrypsin in aqueous ethanol.

The effects of calcium ions on the conformation and catalytic activity of trypsin and alpha-chymotrypsin were studied in aqueous ethanol. The activity of alpha-chymotrypsin was practically lost within 10 min in the presence of 60% ethanol while trypsin preserved about 40% of its original activity even in 85% ethanol at pH 3. The catalytic activity of alpha-chymotrypsin did not decrease in the presence of 1.2M CaCl2 and 0.6M CaCl2 with trypsin in ethanolic solvent. In the latter case an activation of enzyme was observed. The stabilizing effects of calcium ions were accompanied by an increase in the helical content in both enzymes, as followed by circular dichroism measurements.

Calcium↗
PubMed2003

Dopaminergic contributions to the visual categorization of natural scenes: evidence from Parkinson's disease.

Recent evidence raised the possibility that dopaminergic mechanisms in the neostriatum play an important role in categorization. In this study, we examined the electrophysiological correlates of natural scene categorization in Parkinson's disease (PD), which is characterized by the depletion of dopamine in the neostriatum. Event-related potentials (ERPs) were recorded in PD patients and age-matched control subjects using a natural scene categorization task. Subjects had to decide whether a briefly presented image contained animals or non-animals. In the control group, the mean amplitudes of N1 (150-250 ms) and N2 components (400-600 ms) were more negative for non-animal scenes as compared with stimuli containing animals, whereas P2 (250-350 ms) was more positive for animals. In contrast, in the PD group the mean amplitudes of N1 and N2 components were similar for both animal and non-animal stimuli, and the P2 amplitudes were reduced. In the case of N1 peak latency, there was no between-group difference, whereas the N2 and P2 components were significantly delayed in the PD group. These results suggest that both perceptual (N1) and semantic (N2) processes related to the categorization of natural scenes are specifically impaired in PD. In the temporal domain, the slowed semantic processing is preceded by a relatively normally paced perceptual analysis. These findings are in agreement with the hypothesis emphasizing the importance of striatal dopaminergic mechanisms in classification functions.

Aged↗
PubMed2003

Behavioural changes in rats treated with a neurotoxic dose regimen of dextrorotatory amphetamine derivatives.

Repeated administration of amphetamine derivatives is reported to induce neurotoxicity in rat brain. Methamphetamine (MA) impairs the function of both the dopaminergic and serotonergic systems, 3,4-methylenedioxymethamphetamine (MDMA, Ecstasy) affects primarily the latter system. The neurochemical deficits induced by these amphetamines have been described in detail, but relatively few data have been reported regarding the behavioural consequences of the neurotoxic treatment. The aim of the present study was to investigate short- and long-term behavioural consequences of treatment with neurotoxic doses of (+)MA or (+)MDMA. Spontaneous locomotor activity in novel surroundings and cognitive function (avoidance behaviour) were evaluated. Rats were treated with four s.c. injections of 10 mg/kg (+)MA or (+)MDMA with a 2-hour interval between each injection. Behavioural tests were then carried out 3 days, 1, 2 and 4 weeks after these treatments. A reduction of spontaneous locomotor activity in novel surroundings was detected 3 days after the treatment with the study drugs, but not after 1, 2 and 4 weeks. No change in passive and active avoidance learning was observed. The lack of marked behavioural changes after a neurotoxic dose regimen indicates that some compensatory mechanisms may develop and counterbalance the neurochemical changes induced by these amphetamine compounds.

Animals↗
PubMed2002

Short-term omeprazole treatment does not influence biochemical parameters of bone turnover in children.

Gastric proton pump inhibitors are widely used in the treatment of dyspeptic problems and for the eradication of H. pylori infection. Data are not available on whether omeprazole, a representative of proton pump inhibitors, influences the function of osteoclastic H+-pump in children. We studied the impact of short-term omeprazole administration on the biochemical parameters of bone turnover in pediatric patients. Urinary calcium excretion, serum total alkaline phosphatase activity, collagen type 1 crosslinked C-telopeptide, and osteocalcin levels were determined in 34 children [20 girls (9 prepubertal) and 14 boys (6 prepubertal)] before and after 2 weeks of omeprazole treatment at a dose of 20 mg/day. The measured parameters were within the healthy reference range in each patient. None of them altered during the study in any age or in any gender. We conclude that omeprazole, at a dose of 20 mg/day, does not significantly influence the investigated biochemical parameters of osteoclast and osteoblast function in pediatric patients.

Adolescent↗
PubMed2002

Gender differences in panic disorder symptoms and illicit drug use among young people in Hungary.

The authors have investigated the frequency of illicit drug use, and spontaneous and drug-provoked panic disorder symptoms in Hungarian youths. A semi-structured self-reporting questionnaire (with questions about drug usage and the persistence of some DSM-IV panic disorder symptoms) was filled out in discos/nightclubs, secondary schools and universities. Almost 17% of the total sample (n = 1298) reported on illicit drug-use at least once in their life, and this rate was significantly higher among males. Regardless of the illegal drug use 14.6% of the total sample reported on four or more DSM-IV symptoms of panic disorder, and this rate was significantly higher among females. Analyzing the panic disorder symptoms only among drug-users (n = 219), the frequency of persons with four or more anxiety symptoms was 14.1% before drug use, and it increased to 30.6% during the period of drug use (P < 0.001). The findings support previous results showing (i) higher prevalence of anxiety symptoms among females; (ii) higher rate of illicit drug use among males; and (iii) a possible anxiety-provoking effect of illicit drugs.

Adult↗
PubMed2002

Experimental studies on the nature of bonding of DNA*bipyridyl-(ethylenediamine)platinum(II) and DNA*netropsin complexes in solution and oriented wet-spun films.

The stability of complexes of NaDNA with bipyridyl- (ethylenediamine)platinum(II) (abbreviated [(bipy)Pt(en)](2+)) and with netropsin has been studied using two techniques: (i) ultraviolet (UV) melting experiments were done on NaDNA* [(bipy)Pt(en)](2+), showing that the [(bipy)Pt(en)](2+) ligand stabilizes the DNA double helix structure; and (ii) swelling measurements (via optical microscopy) as a function of relative humidity were done on wet-spun oriented films of NaDNA*[(bipy)Pt(en)](2+) and of NaDNA*netropsin. The swelling data shows that an irreversible transition of the films occurs at high relative humidity, first for the NaDNA*netropsin, then for pure NaDNA, and lastly for the NaDNA*[(bipy)Pt(en)](2+). These results are indicative that the [(bipy)Pt(en)](2+) complex stabilizes the intermolecular bonds which mediate the film swelling characteristics. A model is suggested for the binding of [(bipy)Pt(en)](2+) to DNA to explain why the swelling experiments show this ligand as increasing the intermolecular bond strength between the DNA double helices, while netropsin decreases this degree of stabilization.

2,2'-Dipyridyl↗
PubMed2002

Training-induced alterations of the fatty acid profile of rabbit muscles.

The present study was designed to investigate whether meat-type rabbits are able to perform treadmill running as a daily routine exercise, and if so, whether the exercise induces specific proportional changes in the fatty acid composition of their muscles. After a four-week training period 8-week-old rabbits were slaughtered and the total activity of plasma lactate dehydrogenase was measured, showing a significant difference between the exercised and control groups (429 +/- 126 IU/l vs. 639 +/- 203 IU/l). Furthermore the fatty acid composition of m. longissimus dorsi (MLD) and m. vastus lateralis (MVL) was determined by means of gas chromatography. Exercise increased the proportions of oleic acid (C18:1 n-9) in both MLD and MVL as compared to the control group. However, the level of stearic (C18:0) and arachidonic (C20:4 n-6) acids significantly decreased in the MVL after the exercise. Changes in the fatty acid profile resulting from the physically loaded condition were of the same tendency in both muscles, adding that the MVL might have been exposed to the exercise more intensively; alterations there occurred in a more pronounced manner. Based on the inference that the composition of membrane structure was also affected, these alterations may have important consequences on meat quality.

Animal Feed↗
PubMed2002

Analysis of the random distribution of station-tested pigs based on their genetic merit.

The analysis was conducted on the national database of the station tests carried out between May 1996 and February 2001, using the Hungarian Large White (LW) and Hungarian Landrace (LR) breeds, and the A-line of the Ka-Hyb hybrid (MLW). Days of test, total amount of feed consumed and valuable cuts were taken into the analysis to test the random distribution of the animals' phenotypic measurements and predicted breeding values across the contemporary groups of origin. The phenotypic measurements of all traits were clearly positively associated with the herds of origin (b = 0.52-1.08). Animals with favourable phenotypic measurements originated from better herds. On the contrary, the predicted breeding values seemed to be independent of the herd effects (b = -0.16-0.08) and suggested a possible random distribution across the contemporary groups.

Analysis of Variance↗
PubMed2001

Immunohistochemical investigation of actin-anchoring proteins vinculin, talin and paxillin in rat brain following lesion: a moderate reaction, confined to the astroglia of brain tracts.

The present study investigated the immunoreactivity of vinculin, talin and paxillin following stab wounds in the cortex and the underlying white matter of adult rats. These proteins participate in the anchoring of actin filaments to the cell membrane at the focal adhesion plaques, and they are of essential importance in cell motility. Without lesion, vinculin, talin and paxillin immunopositive astrocytes were not recognizable in the cortex and only scarcely in the white matter, if at all. Following lesion, several astrocytes immunopositive to vinculin, talin and paxillin appeared in the white matter, whereas none of them was found in the overlying cortex. Glial fibrillary acidic protein (GFAP) immunopositivity was intense in both areas. The distribution of the actin-anchoring proteins following lesions was similar to that found of the intermediate-filament associated protein plectin, in our previous study.

Animals↗
PubMed2001

Signs of autonomic neuropathy in childhood uremia.

To evaluate the presence of autonomic neuropathy in childhood uremia, cardiovascular autonomic reflexes were examined in children with chronic renal failure. Cardiovascular autonomic reflexes of 10 uremic patients on chronic dialysis and 10 transplanted patients were compared to assess the effect of transplantation on autonomic neuropathy. Resting heart rate, heart rate changes induced by deep breathing, by Valsalva maneuver, and following standing up, and blood pressure change induced by handgrip test were examined. Of the 10 uremic children, 4 showed early involvement and 2 had definite involvement of autonomic neuropathy. Only 1 of the 10 transplanted patients showed early signs of autonomic neuropathy. Autonomic tests demonstrated predominantly parasympathetic dysfunction. In conclusion, cardiovascular autonomic neuropathy is not rare in children and adolescents and young adults with chronic renal failure. In contrast, the prevalence is very low in transplanted patients with similar uremic precedents. Efforts should be made to prevent or delay this uremia-related complication.

Adolescent↗
PubMed2001

Monitoring cardiovascular changes during hemodialysis in children.

Hemodialysis (HD) causes rapid volume shifts and circulatory changes. In chronic renal failure (CRF) Na+/K+ATP-ase is depressed, whereas endogenous digoxin-like factor (EDLF) is elevated. Our aim was to characterize HD-induced cardiovascular adaptation and its possible links to Na+/K+ATP-ase and EDLF. Eleven children with CRF on HD (aged 14.7 +/- 3.7 years) and 11 healthy children were investigated for basic circulatory parameters. Thoracic impedance (Zo) and circulatory parameters were monitored by impedance cardiography (ICG) during HD. Erythrocyte Na+/K+ATP-ase and EDLF were measured before and after HD. Up to the loss of 6% of total body weight, Zo rose linearly with fluid removal, above this no further increase occurred. Heart rate and mean arterial pressure (MAP) were inversely related (r = -0.97); MAP rose in the first and decreased in the second part of HD. Systemic vascular resistance paralleled MAP, whereas stroke volume rapidly decreased, but stabilized in the second part of HD. The ratio of preejection period/ventricular ejection time (PEP/VET) correlated positively with HD duration (r = 0.92), suggesting diminished cardiac filling. Cardiac index (CI) remained stable. EDLF was high in uremia accompanied by depressed Na+/K+ATP-ase (P < 0.05 and P < 0.01, respectively). Following HD Na+/K+ATP-ase normalized. Correlation between Na+/K+ATP-ase activity and MAP was linear (r = 0.85). In conclusion, ICG during HD provides detailed information concerning circulatory adaptation resulting in stable CI, suggesting that the dialysis-induced hypovolemia is compensated by the centralization of the blood volume. Changes of Na+/K+ATP-ase indicate that dialyzable blood pressure-regulating substance(s) inhibit(s) the pump. However, lack of further correlation between Na+/K+ATP-ase, EDLF, and cardiovascular parameters indicates the complexity of the regulatory processes.

Adolescent↗
PubMed2001

Abundance and activity of Ca2+-ATPase in hypercalciuric children.

The plasma membrane Ca2+-ATPase (PMCA) is one of the main regulators of cell Ca2+ homeostasis. The aim of our study was to determine whether the abundance and activity of PMCA are altered in erythrocytes of children with idiopathic hypercalciuria. Twenty-four children with idiopathic hypercalciuria (13 girls and 11 boys, mean age 10.6+/-4.8 years; mean urinary calcium concentration 0.85+/-0.20 mmol/mmol creatinine) and 30 healthy age-matched children were enrolled. PMCA protein abundance was determined by Western blot analysis. Enzyme activity was determined spectrophotometrically. The abundance of PMCA did not differ in hypercalciuric patients from that of control subjects (98+/-22% vs 100+/-18%). Moreover, the activity was not different between the studied groups (3141+/-1494 vs 2953+/-780 nmol ATP/mg protein/h). The extent of hypercalciuria did not correlate with enzyme abundance or activity. Assuming that erythrocytes may reflect the renal tubular transporting processes, our data suggest that other Ca2+-transport mechanisms than PMCA might be involved in the development of idiopathic hypercalciuria in children.

Adolescent↗
PubMed2001

Treatment of intraocular pressure elevation after photorefractive keratectomy.

PURPOSE: To study the effect of timolol maleate, dorzolamide, or a combination of both in post photorefractive keratectomy (PRK) eyes with an elevated intraocular pressure (IOP) after topical steroid administration. SETTING: Refractive Surgery Outpatient Department, 1st Department of Ophthalmology, Semmelweis University, Budapest, Hungary. METHODS: Forty-five patients with elevated IOP were randomly enrolled in 3 groups: Group 1 received timolol maleate 0.5% twice a day; Group 2 received timolol maleate 0.5% twice a day and dorzolamide 2% 3 times a day; and Group 3 received only topical dorzolamide 2% 3 times a day. Intraocular pressure was measured 3 days and 1, 3, and 6 weeks after the antiglaucoma medication was started. RESULTS: The mean preoperative IOP was 15.25 mm Hg +/- 1.28 (SD). Following administration of topical fluorometholone, the IOP increased a mean of 27.39 +/- 2.88 mm Hg. Six weeks after the antiglaucoma therapy was started, the mean IOP reduction was 6.6 mm Hg in Group 1, 8.86 mm Hg in Group 2, and 4.64 mm Hg in Group 3. CONCLUSIONS: A combination therapy of timolol 0.5% and dorzolamide 2% was most effective in treating secondary IOP elevation after PRK. Dorzolamide alone did not adequately control secondary post-PRK IOP elevation.

Administration, Topical↗
PubMed2001

Intraoperative flow measurement of native coronary artery can help decision making before CABG.

We report the case of a patient with three-vessel coronary artery disease whose right coronary artery had been stented at the time of the diagnostic procedure. He had recurrent angina 12 days later and was transferred for urgent coronary artery bypass grafting. No repeat coronary angiography was performed. In the operating room, the flow on the native right coronary artery was determined with an ultrasonic flow probe.

Aged↗
PubMed2001

Scanning laser polarimetry versus frequency-doubling perimetry and conventional threshold perimetry: changes during a 12-month follow-up in preperimetric glaucoma. A pilot study.

PURPOSE: To evaluate the possibility for detecting the progression in preperimetric primary open angle glaucoma (POAG) using scanning laser polarimetry (SLP), frequency-doubling technology (FDT), and conventional automated perimetry (AP). PATIENTS AND METHODS: 22 eyes of 11 preperimetric POAG patients were evaluated using SLP (Nerve Fiber Analyzer, GDx), AP (Humphrey 24-2 threshold test) and FDT (30 degrees threshold test). All eyes had intraocular pressure (IOP) higher than 21 mmHg before treatment, but were consistently lower than 22 mm Hg with unchanged topical medication before and during the study. At the initial evaluation session optic nerve heads showed mild glaucomatous changes but the visual fields were normal (MD better than 2.0 dB, Glaucoma Hemifield Test: within normal limits or borderline). AP and FDT measurements were repeated 6 months later, and all three tests were repeated 12 months after the first investigation. RESULTS: IOP, AP and FDT measurements showed no statistically significant changes during the 12-month follow up period. In contrast to this, a tendency for a glaucomatous type decrease was seen with SLP in the retinal nerve fibre layer (RNFL) thickness parameters (mean superior and inferior sector thickness values, ellipse average thickness and maximal modulation). The mean decrease of RNFL thickness in the superior and inferior sectors was 2.77 microm and 2.48 microm, respectively. Using the two-way nested ANOVA, which considers the relation between the right and left eyes of the subjects, the decrease was statistically significant (p=0.021) for the inferior sector RNFL thickness. CONCLUSION: The results suggest that scanning laser polarimetry is a useful technique to detect and measure glaucomatous progression in early glaucoma. Scanning laser polarimetry of the RNFL may help to detect and quantify early progression even if worsening is not seen with perimetry and FDT tests.

Adult↗