Biomedical subjects

E Kovács

Publications and source records attributed to E Kovács.

At least 19 recordsLinked to original sources

PubMed2006

Structural-functional changes in detached cucumber leaves, and modelling these by hormone-treated leaf discs.

Senescence and rejuvenation were investigated in detached cucumber (Cucumis sativus L.) leaves after cultivation in nutrient solution for one week or four weeks. Rooting of the petiole (visible generally from the 7th day) elicited a combination of different morphological, anatomical, and physiological changes in the lamina. Extensive growth in area and thickness, extreme regreening, changes of chloroplast structure and activity, as well as the pattern of Chl-protein complexes were observed and compared either to the corresponding parameters of young detached leaves or mature attached leaves. These responses could be provoked separately by treating excised leaf discs with kinetin, benzyladenine, or indolylacetic acid. The hormones showed mutuality in their effects, benzyladenine being responsible for the growth of cells, while indolylacetic acid and kinetin promoted an increase in chlorophyll content. However, none of the treatments resulted in the growth of the chloroplasts in the leaf discs, which was only prominent in the rooting leaves.

Aminobutyrates↗

PubMed2003

Disturbed regulation of cholesterol synthesis in monocytes of obese patients with hypercholesterolemia.

The aim of the present study was to clarify the influence of obesity on the functions of low-density lipoprotein receptors (LDL-R) and 3-hydroxy-3-methylglutarate-coenyzme A (HMG-CoA) reductase both in healthy control subjects and in patients with hypercholesterolemia (HC). Experiments were performed on monocytes of 15 non-obese (C I) and 11 obese (C II) healthy control subjects and on 22 non-obese (HC I) and 26 obese (HC II) patients with HC. [(125)I]LDL was used to determine LDL-R activity by measuring binding and intracellular degradation. The rate of endogenous cholesterol synthesis was measured using [(14)C]acetate incorporation into the cholesterol fraction of monocytes. The binding ability of [(125)I]LDL was identical across all groups. The [(14)C]acetate incorporation in resting monocytes was increased only in obese HC group. The 50-microg/mL LDL protein-induced inhibition of [(14)C]acetate incorporation was significantly diminished (P <.001) in the same group. A strong positive correlation was detected between the [(14)C]acetate incorporation by resting cells and LDL-induced inhibition in all groups except the obese HC group, in which their correlation was negative (P <.001). Furthermore, in the obese HC group, a significant positive correlation was detected between body mass index (BMI) and the basal level of [(14)C]acetate incorporation, whereas a negative correlation was found between BMI and LDL-induced inhibition of [(14)C]acetate incorporation. The present data suggest that in patients with HC the concomitant obesity results in dysregulation of cholesterol homeostasis, which may contribute to the accelerated atherosclerosis.

Acetates↗

PubMed2002

Effect of gamma and UV-B/C radiation on plant cells.

The biological effect of gamma-rays is based on the interaction with atoms or molecules in the cell, particularly water, to produce free radicals, which can damage different important compounds of plant cell. The UV-B/C photons have enough energy to destroy chemical bounds, causing a photochemical reaction. The biological effect is due to these processes. This paper is focused on the structural and biochemical changes of the cell wall and plastids after gamma and/or UV-B irradiation. Gamma-rays accelerate the softening of fruits, causing the breakdown of middle lamella in cell wall. They also influence the plastid development and function, such as starch-sugar interconversion. The penetration of UV-B light into the cell is limited, while gamma-rays penetrate through the cells. For this reason, UV-B light has a strong effect on surface or near-to-surface area in plant cells. UV-B radiation influences plastid structure (mostly thylakoid membranes) and photosynthesis. Some kinds of pigments, such as carotenoids, flavonoids save plant cells against UV-B and gamma irradiation. Plant cells are generally ozone sensitive. The detoxifying systems operate at the cellular level. Methods for studying structural changes in plant cells develop in direction to molecular biology, combined with immunoassays and new microscopical techniques. Nowadays, UV-B radiation is undergoing much research, being an environmental factor which causes damage to both humans and plant cells.

Cell Wall↗

PubMed2001

The chaperonins of Synechocystis PCC 6803 differ in heat inducibility and chaperone activity.

The chaperonins GroEL and Cpn60 were isolated from the cyanobacterium Synechocystis PCC 6803 and characterized. In cells grown under optimal conditions their ratio was about one to one. However, the amount of GroEL increased considerably more than that of Cpn60 in response to heat stress. The labile chaperonin oligomer required stabilization by MgATP or glycerol during isolation. Use of the E. coli mutant strain, groEL44 revealed that the functional properties of the two cyanobacterial chaperonins are strikingly different. Overexpression of cyanobacterial GroEL in the E. coli mutant strain allowed growth at elevated temperature, the formation of mature bacteriophage T4, and active Rubisco enzyme assembly. In contrast, Cpn60 partially complemented the temperature-sensitive phenotype, the Rubisco assembly defect and did not promote the growth of the bacteriophage T4. The difference in chaperone activity of the two cyanobacterial chaperonins very probably reflects the unique chaperonin properties required during the life of Synechocystis PCC 6803.

Bacteriophage T4↗

PubMed2001

Synthesis of new cyclitol compounds that influence the activity of phosphatidylinositol 4-kinase isoform, PI4K230.

The synthesis, chemical derivatization, and investigation of the inhibitory properties of novel cyclitol derivatives on the phosphatidylinositol 4-kinase enzymes PI4K55 and PI4K230 involved in the phosphatidylinositol cycle are reported. Some of the prepared cyclitol derivatives (i.e. 9, 11, 12, and 14) proved to be very powerful and specific irreversible inhibitors of PI4K230 at or below a concentration of 1 mM.

Animals↗

PubMed2001

Role of nitric oxide in the regulation of blood flow in the rat submandibular gland during carotid artery occlusion.

The possible involvement of nitric oxide in the preservation of blood flow to the rat submandibular gland after uni- or bilateral occlusion of the common carotid was studied. Glandular blood flow and mean blood pressure were monitored before, during and after carotid occlusion in the presence and absence of the nitric oxide synthase inhibitor N(omega)-nitro-L-arginine-methyl-ester (L-NAME). To calculate vascular resistance, the local perfusion pressure distal to the point of occlusion was also measured. In normal rats, uni- or bilateral carotid occlusion resulted in an immediate decrease in ipsilateral glandular blood flow. After the cessation of carotid occlusion, hyperaemia was observed in the submandibular gland. Both local perfusion pressure and vascular resistance decreased during carotid occlusion. In the group pretreated with L-NAME, trends in blood-flow responses to uni- or bilateral occlusion were identical to those registered in the control groups, though the magnitude of the alterations was significantly less. The well-maintained glandular blood flow was due to functioning vascular anastomoses and compensating dilatation of glandular blood vessels. Nitric oxide had only a restrained effect on this compensatory mechanism.

Analysis of Variance↗

PubMed2001

[Coronary artery bypass grafting without extracorporeal circulation].

At the Department of Cardiovascular Surgery of Semmelweis University, Budapest we have performed 57 coronary bypass operations without using cardiopulmonary bypass between 1996 and September 2001. Due to the learning phase we preferred cases of 1-2 wessel diseases, and revascularisation necessary on the anterior surface of the heart. In the beginning the stabilization of the operative field was ensured by manual methods, then by applying mechanical stabilization devices (Octopus 2, Genzyme). As to the type of operative indication overwhelmingly elective operations were performed. REDO procedure, i.e. repeated coronary bypass operation was carried out in 2 cases. Forty-eight patients recovered without complication. Two patients died, one of them suffered perioperative infarction, the other died due to cerebral complication. Total mortality was 3.5%. As a consequence of cardiac ischaemia in the direct postoperative period, we performed emergent coronary ballon dilatation (PTCA) in two cases. In three cases we experienced perioperative infarction. We followed up our patients by way of interview and telephone interview. The follow-up is 95%, the average follow-up time is 15 months. Significant cardiac event (infarction, PTCA or REDO coronary operation) took place in the case of 7 patients. In the majority of our patients the operation resulted in an improvement of condition, 43 patients are free from angina.

Adult↗

PubMed2000

Alterations of P53 and RB genes and the evolution of the accelerated phase of chronic myeloid leukemia.

Using the single-strand conformation polymorphism and heteroduplex analyses, the P53 and RB genes were analyzed in cell samples from twenty-eight patients with chronic myeloid leukemia (CML) both at diagnosis and at the onset of accelerated phase (AP) of the disease. No alterations of the P53 or RB genes were found in any of the chronic phase (CP) samples. Structural abnormalities of the P53 gene were observed in ten of twenty-eight AP samples within exons 4, 5, 7 and 9. Of the ten cases of AP disease with altered P53 genes, five patients also suffered from the deletion of the other allele. Alterations of the RB gene could be detected in six AP samples, and aberrant band patterns were found in the analysis of exons 2, 3, 4, 6, 7, 13, 14, 17, 21 and 26. Among the six AP samples with structural abnormalities of the RB gene, two showed the loss of the other allele. It is of note that alterations of both P53 and RB genes were observed in two AP samples. Our data strongly suggest that abnormalities of the P53 and RB genes and acceleration of CML are linked events in some cases of AP.

Adult↗

PubMed1999

Disturbed LDL and scavenger receptor functions in monocytes from chronic haemodialysed patients.

BACKGROUND: The most frequent complication in patients with end-stage renal failure on chronic haemodialysis (HD) treatment is atherosclerosis, i.e. the different forms of heart and vascular diseases. The complete disorder of serum lipid and lipoprotein patterns is well demonstrated, whereas our knowledge about the low-density lipoprotein (LDL) and scavenger receptor expression and function are poorly understood. METHODS: In our current work, LDL and scavenger receptor expression and functions were simultaneously studied in monocytes obtained from 15 healthy male control subjects and from 11 chronic HD male patients applied with (125)I-labelled LDL, isolated from healthy volunteers. To study the scavenger LDL receptors, labelled acetylated LDL (acLDL) was used. RESULTS: LDL binding to the monocytes of the HD-group was found to be decreased in comparison to that of the controls. As a result, the 50 microg LDL protein-induced inhibition of endogenous cholesterol synthesis was also diminished. In contrast, acLDL binding was greatly increased, though it could trigger only a low apoE synthesis. Consequently the number of cholesterol inclusions in monocytes was increased. CONCLUSIONS: The disturbed expression and function of LDL and scavenger receptors both may play significant roles in pathogenesis of cardiovascular complications in chronic HD patients. Based on our present results, it can be assumed that dysfunction of scavenger receptors is at the centre of cardiovascular complications of HD patients with renal failure.

Anticholesteremic Agents↗

PubMed1999

Altered signal pathway in granulocytes from patients with hypercholesterolemia.

In the present study the signal transduction of the formyl-Met-Leu-Phe receptor was studied in granulocytes obtained from control subjects and patients with elevated low density lipoprotein levels. According to our results, 10 nm formyl-Met-Leu-Phe in control cells activates phospholipase C inducing a pronounced inositol phosphate production followed by a Ca(2+) signal from intracellular pools. The pertussis toxin-sensitive O(2)(-) generation and leukotriene synthesis were moderate. In contrast, in granulocytes from hypercholesterolemic patients, formyl-Met-Leu-Phe triggered an intensive pertussis toxin-insensitive oxidative burst and leukotriene synthesis. The inositol trisphosphate and Ca(2+) signals were decreased significantly in granulocytes of hypercholesterolemic patients and seem to be dependent on the extracellular Ca(2+) content. Furthermore, in the resting granulocytes of hypercholesterolemic patients the [Ca(2+)]i and the membrane-bound protein kinase C activity were higher than in controls, the time of normalization after the low Ca(2+) signal was delayed, while the membrane fluidity was decreased. Our results suggest that in these ex vivo experiments, the high level of circulating low density lipoprotein in patients can affect the membrane composition of granulocytes leading to altered signal transduction by the formyl-Met-Leu-Phe receptor, to altered Ca(2+) pump-activity, and protein kinase C translocation.

Calcium Signaling↗

PubMed1998

[Molecular biologic screening test (PCR) for fragile X syndrome].

Fragile X syndrome is the most common inherited from of familial mental retardation. It is caused by an expanded CGG repeat in the first exon of the fragile X mental retardation gene. A polymerase chain reaction based technique was used for the identification of full mutations among men. According to our conditions full mutations failed to amplify. An internal control was used at a CG rich region 147 bp upstream of the polymorphic region. The bands were visualised on silver stained polyacrylamide gels. From the 57 individuals studied molecular analysis was performed on 38 males and 16 females. From the 26 males with suspected fragile X syndrome 9 males resulted in no amplification of the 500 kb product, all having a positive cytogenetic result for fragile X syndrome. One cytogeneticly positive male had normal results by molecular studies suggesting a different mutation. All control males had normal results. The results on the 16 females studied were inconclusive. We suggest that our method is highly sensitive and specific for screening males for fragile X syndrome.

Female↗

PubMed1998

[Diagnosis of Prader-Willi syndrome by reverse transcriptase polymerase chain reaction].

To approve Prader-Willi syndrome by molecular diagnostic assay, polymerase chain reaction of reverse-transcribed RNA was introduced by which indirect information can be gained on all known forms of the mutation. In this pilot study, 4 patients and 16 healthy control individuals were examined. Although the different mutation forms can not directly by identified by this approach, it is a useful and reliable test to confirm the clinical diagnosis of the Prader-Willi syndrome, and to screen for the syndrome in patients who present with only a few typical features.

Humans↗

PubMed1998

[Mutation analysis in the CTG-base multiplication in a family with myotonic dystrophy in three generations].

A PCR-based method with a novel silver staining detection was developed for the determination of CTG repeat number in the 3' untranslated region of the MD-PK gene responsible for myotonic dystrophy. Through the investigation of a family with affected members in three generations the application of the method is presented. According to the results, healthy individuals were verified easily, and the repeat number in patients with mild features or with premutation could be determined accurately. In severe clinical forms, e.g. congenital myopathy, the expansion can be deduced only from the lack of amplification, however, this is also helpful if the segregation of familial alleles is known.

Alleles↗

PubMed1998

Membrane physical state controls the signaling mechanism of the heat shock response in Synechocystis PCC 6803: identification of hsp17 as a "fluidity gene".

The fluidity of Synechocystis membranes was adjusted in vivo by temperature acclimation, addition of fluidizer agent benzyl alcohol, or catalytic lipid hydrogenation specific to plasma membranes. The reduced membrane physical order in thylakoids obtained by either downshifting growth temperature or administration of benzyl alcohol was paralleled with enhanced thermosensitivity of the photosynthetic membrane. Simultaneously, the stress-sensing system leading to the cellular heat shock (HS) response also has been altered. There was a close correlation between thylakoid fluidity levels, monitored by steady-state 1,6-diphenyl-1,3,5-hexatriene anisotropy, and threshold temperatures required for maximal activation of all of the HS-inducible genes investigated, including dnaK, groESL, cpn60, and hsp17. The causal relationship between the pre-existing thylakoid physical order and temperature set point of both the transcriptional activation and the de novo protein synthesis was the most striking for the 17-kDa HS protein (HSP17) associated mostly with the thylakoid membranes. These findings together with the fact that the in vivo modulation of lipid saturation within cytoplasmic membrane had no effect on HS response suggest that thylakoid acts as a cellular thermometer where thermal stress is sensed and transduced into a cellular signal leading to the activation of HS genes.

Cell Membrane↗

PubMed1998

Specific and scavenger low-density lipoprotein receptors involved in the disturbed lipid metabolism of patients with non-insulin-dependent diabetes mellitus are independent of obesity.

Comparative studies were performed on monocyte-derived macrophages (MDMs), prepared by a 72-hour incubation of blood monocytes obtained from patients with non-insulin-dependent diabetes mellitus (NIDDM) and age-matched obese and non-obese controls. The MDMs, after a 72-hour culturing, expressed both specific and scavenger low-density lipoprotein (LDL) receptors on their surfaces. To study the binding capacity of both receptor types, [125I]LDL and [125I] acetylated LDL (acLDL) were applied to cells and the labeled ligands were then monitored to estimate the rate of intracellular degradations. The LDL-induced inhibition of endogenous cholesterol synthesis and the acLDL-triggered apolipoprotein (apo) E secretion were also studied, as the biological marker of receptor activation. The results indicate that the binding capacities of both specific and scavenger LDL receptors were not reduced in MDMs of diabetic patients. However, the intracellular degradation after LDL incorporation was decreased. The LDL-induced inhibition of cholesterol synthesis and the acLDL-transmitted apo E secretion were also found to be decreased in the MDMs of patients with NIDDM as compared with the obese and non-obese control groups. The NIDDM-induced impaired signal transduction of both specific and scavenger LDL receptors suggests an unclarified functional alteration of both receptor structures.

Acetates↗

PubMed1998

Changes in oncogene expression implicated in evolution of chronic granulocytic leukemia from its chronic phase to acceleration.

Expression of nine oncogenes was investigated in cell samples from fifteen patients with Philadelphia chromosome (Ph)-positive chronic granulocytic leukemia (CGL) both at diagnosis and at the onset of accelerated phase (AP) of the disease. The bcr-abl fusion gene, the H-ras gene and the c-myb gene were universally expressed. In comparison with the chronic phase (CP) of the disease, an increase in the levels of bcr-abl-, c-myb- and H-ras-related transcripts was found in three, two and three AP samples, respectively. Elevation of the bcr-abl-related message was associated with duplication of the Ph chromosome and amplification of the bcr-abl fusion gene in one AP sample. No CP samples were positive for c-myc or c-sis expression. On the contrary, c-myc and c-sis were expressed in three and four AP samples, respectively. The presence of c-myc-related transcript was associated with trisomy 8 with or without amplification of the c-myc oncogene in leukemia cells of two patients with CGL in AP. No changes of oncogene expression were found in four AP samples. However, we observed deletions of chromosome 13 and 17 or i(17q) in three of them, suggesting that tumor suppressor gene alterations may also be responsible for the development of AP of CGL. Our data indicate that heterogeneous alterations in oncogenes and tumor suppressor genes accompany the evolution of CGL-CP to the AP of the disease.

Acute-Phase Reaction↗

PubMed1998

Distribution profile and in vivo RNA association of cytoplasmic AU-rich sequence binding proteins in various mammalian cells: effect of the organizational state of cellular architecture.

With the aid of sequential detergent fractionation and label transfer techniques, in this study we monitored the distribution of cytoplasmic AU-rich sequence binding proteins (AUBP) in different cell types. We show here that cells of various origin display diverse AUBP profiles when the presence and abundance of AUBPs were compared in two major cytoplasmic compartments, the non-ionic detergent-soluble and -insoluble fractions. We also demonstrate that different RNA probes derived from AU-rich 3'-UTR elements of various cytokine and proto-oncogene mRNAs detect distinct AUBPs within the same cell. When the in vivo association of these proteins with AU-rich RNA was assessed using the combination of in vivo UV-crosslinking and label transfer methods, we found that detachment of monolayer cells by trypsinization or disruption of the microfilament network by Cytochalasin treatment prior to UV light exposure, led to selective changes in both the cytoplasmic distribution and in vivo RNA association of many AUBPs. These data indicate that the organizational state of cytoarchitecture may influence processes involved in AUBP-mediated mRNA metabolism.

Actin Cytoskeleton↗

PubMed1997

Chaperonin genes of the Synechocystis PCC 6803 are differentially regulated under light-dark transition during heat stress.

Transcriptional startpoints of the two heat inducible chaperonin genes of Synechocystis PCC 6803 were mapped within the conservative CIRCE element and proved to be identical irrespective of the temperature treatment. Finding of an ORF encoding for a potential CIRCE binding repressor (HrcA) further suggests that both groEL-analogs are regulated in a CIRCE-dependent manner. In contrast to the expectations, the chaperonin twins are differentially expressed under light-dark transition during heat stress. Not the light per se, but rather the photosynthetic electron transport appears to be accountable for the regulatory differences. Our findings support the hypothesis that multiple chaperonins play different physiological roles under stress conditions.

Amino Acid Sequence↗