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J Kovács

Publications and source records attributed to J Kovács.

At least 19 recordsLinked to original sources
PubMed1999

Pyruvate kinase as a microtubule destabilizing factor in vitro.

Endogenous control of microtubule dynamism is essential in many cell types. Numerous microtubule-adhering proteins stabilize the polymer status, while very few protein factors are described with opposite effects. The brain- and muscle-specific M1 isoform of the enzyme pyruvate kinase is investigated here in this respect. Three pieces of evidence indicate antimicrotubular effects of this protein. (1) Pyruvate kinase inhibits taxol-induced tubulin polymerization into microtubules as revealed by turbidimetry. (2) Pelleting experiments show that pyruvate kinase partially disassembles taxol-stabilized microtubules into less sedimentable oligomers leading to the appearance of tubulin in the supernatant fractions. (3) Electron microscopy reveals the kinase-induced formation of great amounts of thread-like tubulin oligomers which tend to accumulate in a light/less sedimentable fraction. Immunoelectron micrographs using labeled antibody against pyruvate kinase provide evidence for the binding of pyruvate kinase to the thread-like oligomeric forms. The present data allow the assumption that pyruvate kinase may display multiple regulatory functions as a glycolytic control enzyme and as a modulator of microtubule dynamism.

Animals↗
PubMed1999

45T-1, an established cell line with characteristics of Sertoli cells, forms organized aggregates in vitro after exposure to tumor necrosis factor alpha.

In the testis TNF is produced by germinal cells. The putative role of tumor necrosis factor alpha (TNF) in development and differentiation was investigated in 45T-1 mouse cell cultures, a cell line with characteristic markers of Sertoli cells, established from transgenic mouse families expressing the polyoma large T antigen in their testes. Exposure to TNF elicited a gradual assembly of the cells of the monolayer into highly organized spheroids. The first morphological sign of the changes was detected one week after TNF treatment by anti-desmin immunostaining which showed the formation of foci in the culture consisting of several hundred cells connected by an increasing number of cell contacts. Between days 10-20 the cells formed large ovoid or vermiform aggregates covered by several layers of flat, elongated cells. These cells extended septae into the inner mass of the spheroids consisting of loosely arranged, large polygonal or palisadic cells. The spheroids were surrounded by radially arranged elongated cells covered by small blebs. TNF treatment upregulated laminin expression in 45T-1 cell cultures, which is known to induce formation of cord-like structures by Sertoli cells in vitro. Coculturing 45T-1 cells with immortalized germinal cells or TNF-producing HeLa cells also lead to the formation of spheroids. These observations suggest that TNF production of germinal cells might contribute to the organization/differentiation of Sertoli cells.

Animals↗
PubMed1999

New semisynthetic vinca alkaloids: chemical, biochemical and cellular studies.

A new semisynthetic anti-tumour bis-indol compound, KAR-2 [3'-(beta-chloroethyl)-2',4'-dioxo-3,5'-spiro-oxazolidino-4-dea cetoxy-vinblastine] with lower toxicity than vinca alkaloids used in chemotherapy binds to calmodulin but, in contrast to vinblastine, does not exhibit anti-calmodulin activity. To investigate whether the modest chemical modification of bis-indol structure is responsible for the lack of anti-calmodulin potency and for the different pharmacological effects, new derivatives have been synthesized for comparative studies. The synthesis of the KAR derivatives are presented. The comparative studies showed that the spiro-oxazolidino ring and the substitution of a formyl group to a methyl one were responsible for the lack of anti-calmodulin activities. The new derivatives, similar to the mother compounds, inhibited the tubulin assembly in polymerization tests in vitro, however their inhibitory effect was highly dependent on the organization state of microtubules; bundled microtubules appeared to be resistant against the drugs. The maximal cytotoxic activities of KAR derivatives in in vivo mice hosting leukaemia P388 or Ehrlich ascites tumour cells appeared similar to that of vinblastine or vincristine, however significant prolongation of life span could be reached with KAR derivatives only after the administration of a single dose. These studies plus data obtained using a cultured human neuroblastoma cell line showed that KAR compounds displayed their cytotoxic activities at significantly higher concentrations than the mother compounds, although their antimicrotubular activities were similar in vitro. These data suggest that vinblastine/vincristine damage additional crucial cell functions, one of which could be related to calmodulin-mediated processes.

Animals↗
PubMed1998

Evaluation of apoptosis and cell proliferation in experimentally induced renal cysts.

Cell proliferation and apoptosis in renal cysts induced by streptozotocin, alloxan and ferric-nitrilotriacetate were investigated in rats. In the kidneys of all treated animals dilated tubules at the cortico-medullary region, large cysts, glomerular cysts and tubular dilation in the medullary area were found. Both cell proliferation and apoptosis were increased in the epithelium of the non-dilated tubules, in the mesangial and interstitial cells. Cells lining the dilated tubules or cysts demonstrated apoptosis but their proliferating activity was low. By calculating the proliferation-apoptosis ratio we found that alloxan did not change the balance between the two mechanisms. Meanwhile streptozotocin resulted in an increased apoptosis and ferric-nitrilotriacetate in an increased cell proliferation. p53 expression might be responsible for the uncontrolled proliferation in rats treated with ferric-nitrilotriacetate as this oncoprotein was diffusely present in tubular cell nuclei. The observed apoptosis seemed to be independent of bcl-2 oncoprotein expression. We assume that the initial factor in such cystogenesis should be a cellular injury due to direct toxic or to the diabetogenic effect of the drugs. The latter is more likely as all the animals were hyperglycemic and insulin treatment following administration of streptozotocin prevented the morphologic changes.

Alloxan↗
PubMed1998

Analysis of the role of apoptosis and cell proliferation in renal cystic disorders.

Cell proliferation and apoptosis were studied in 8 patients with inherited polycystic kidney disease and in 34 patients with acquired cystic kidney conditions including solitary and multilocular cysts and segmental tubular dilation. Intact renal tissue of 20 surgically removed tumorous kidneys served as control. Cell proliferation and apoptosis were demonstrated by immunohistochemical and in situ end-labeling methods. The percentage of positively stained nuclei was calculated and statistically analyzed. Both apoptosis and cell proliferation were significantly higher (p<0.001) in polycystic kidney disease. The percentage of positively stained nuclei in the whole kidney tissue with acquired cysts did not differ from controls although cell proliferation was significantly higher (p<0.001) in cells lining the cysts. Apoptotic cells were rarely found in the cystic epithelium or were even absent in these cases. Our data indicate that while polycystic kidneys seem to be characterized by abnormal cell survival, acquired renal cysts have different behavior in which so far unknown intracellular changes are more likely to cause tubular distension probably through induced cell proliferation.

Apoptosis↗
PubMed1998

Families with multiple cases of gluten-sensitive enteropathy.

UNLABELLED: Early detection of oligosymptomatic gluten-sensitive enteropathy (GSE) may contribute to the prevention of late complications, such as malignancy. Family members of known GSE patients are at higher risk of being affected. To evaluate the frequency and clinical significance of multiple occurrence, we routinely offered an antiendomysium antibody (EmA)-based non-invasive screening to affected families. Among 997 family members of 396 GSE patients, we identified 89 subjects with EmA positivity and/or severe jejunal villous atrophy. In 83 cases GSE has been verified, four patients refused the biopsy and two subjects are under further observation for latent celiac disease. Prevalence of GSE was 8.5% (80/943) among the first-degree relatives, with significantly higher values in the siblings (13.8%) and offsprings (12.0%) than in the parents (4.2%) of the probands (p < 0.001). In 55 families (13.9% of the families studied) two, in ten families (2.5%) three, in one family four and in one other family six members were affected. Combinations of the clinical presentations of index and screening-detected cases were highly variable, with a high percentage of silent and atypical forms in the relatives. GSE cases presenting both with and without dermatitis herpetiformis occurred in 15 families. Six GSE cases with atypical or mild dermatitis herpetiformis were detected in consequence of the screening. CONCLUSIONS: EmA-assisted family screening resulted in the detection of a clinically significant number of additional GSE patients.

Adolescent↗
PubMed1997

[Peritoneal hemorrhage caused by trophoblast tissue implanted on the peritoneum 6 weeks following induced abortion].

A case of heavy intraperitoneal bleeding from perimetrical implanted trophoblast tissue on the uterus was reported following artificial abortion. The six weeks previously terminated pregnancy was verified by transvaginal ultrasound examination, the unrecognised simultaneous extrauterine pregnancy was excluded. The mechanism of peritoneal implantation of trophoblast tissue is unknown. The authors reported the successful conservative treatment and analyzed possible origin of this rare localisation of trophoblast tissue.

Abortion, Induced↗
PubMed1997

Alternative binding of two sequential glycolytic enzymes to microtubules. Molecular studies in the phosphofructokinase/aldolase/microtubule system.

Simultaneous binding of two sequential glycolytic enzymes, phosphofructokinase and aldolase, to a microtubular network was investigated. The binding of the phosphofructokinase to microtubules and its bundling activity has been previously characterized (Lehotzky, A., Telegdi, M., Liliom, K., and Ovádi, J. (1993) J. Biol. Chem. 268, 10888-10894). Aldolase binding to microtubules at near physiological ionic strength is weak (Kd = 20 microM) as compared with that of the kinase (Kd = 1 microM). The interactions of both enzymes with microtubules are modulated by their common intermediate, fructose-1,6-bisphosphate. Pelleting and electron microscopic measurements have revealed that the aldolase binding interferes with that of phosphofructokinase, although they have distinct binding domains on microtubules. The underlying molecular mechanism responsible for this finding is that in the solution phase aldolase and phosphofructokinase form a bienzyme complex that does not bind to the microtubule. The bienzyme complex formation does not influence the catalytic activity of aldolase, however, it inhibits the dissociation-induced inactivation of the kinase by stabilizing a catalytically active molecular form. The present data suggest the first experimental evidence that two sequential glycolytic enzymes do not associate simultaneously to microtubules, but their complexation in solution provides kinetic advantage for glycolysis.

Animals↗
PubMed1997

Characterization of microtubule-phosphofructokinase complex: specific effects of MgATP and vinblastine.

Phosphofructokinase interacts with both microtubules and microtubules containing microtubule-associated proteins to produce bundling and periodical cross-bridging of tubules. Immunoelectron microscopy using anti-phosphofructokinase antibodies provided direct evidence that the kinase molecules are responsible for the cross-bridging of microtubules. Limited proteolysis by subtilisin, a procedure that cleaves the N-terminal segment of the free enzyme as well as the C-terminal "tails" of tubulin subunits exposed on microtubules, showed that while phosphofructokinase becomes resistant, tubulin retains sensitivity against proteolysis within the heterologous complex. These data suggest that the N-terminal segment of the enzyme, but not the C-terminal "tail" of tubulin subunits, is involved in the interaction between the microtubule and the kinase. The phosphorylation of phosphofructokinase or microtubules containing microtubule-associated proteins by the cAMP-dependent protein kinase did not interfere with the heterologous complex formation. MgATP prevents phosphofructokinase binding to the microtubules, and it can displace the enzyme from the single microtubules. However, the bundled microtubules are apparently resistant to the MgATP dissociation effect. Modelling of the assembly process suggests that the tubulin-kinase complex is able to polymerize as the free tubulin. Vinblastine, an anti-mitotic agent, inhibits tubulin assembly; however, its inhibitory effect is partially suppressed in the presence of phosphofructokinase. Fluorescence anisotropy measurements indicated that kinase and vinblastine compete for tubulin binding with no evidence for ternary complex formation. This competitive mechanism and the ability of the tubulin-enzyme complex to polymerize into microtubules may result in the resistance of the tubulin-enzyme complex against the inhibition of assembly induced by vinblastine. Microtubules formed in the presence of vinblastine plus phosphofructokinase can be visualized by electron microscopy. A molecular model is suggested that summarizes the effects of MgATP and vinblastine on the multiple equilibria in the tubulin/microtubules/phosphofructokinase system.

Adenosine Triphosphate↗
PubMed1997

Transhiatal closure of right-sided esophageal rupture after a left pneumonectomy.

Right-sided spontaneous esophageal rupture developed 2 days after left pneumonectomy and vomiting. To avoid contamination of the pneumonectomized left thoracic cavity as well as a contralateral thoracotomy, we used a transhiatal approach for primary repair of the rupture, combined with right-sided pleural and mediastinal drainage, gastrostomy, and feeding jejunostomy. The 7-day barium meal control showed healing of the rupture.

Aged↗
PubMed1997

Interaction of a new bis-indol derivative, KAR-2 with tubulin and its antimitotic activity.

1. KAR-2 (3"-(beta-chloroethyl)-2",4"-dioxo-3,5"-spiro-oxazolidino- 4-deacetoxy-vinblastine), is a bis-indol derivative; catharantine is coupled with the vindoline moiety which contains a substituted oxazolidino group. Our binding studies showed that KAR-2 exhibited high affinity for bovine purified brain tubulin (Kd-3 microM) and it inhibited microtubule assembly at a concentration of 10 nM. 2. Anti-microtubular activity of KAR-2 was highly dependent on the ultrastructure of microtubules: while the single tubules were sensitive, the tubules cross-linked by phosphofructokinase (ATP: D-fructose-6-phosphate-1-phosphotransferase, EC 2.7.1.11) exhibited significant resistance against KAR-2. 3. The cytoplasmic microtubules of Chinese hamster ovary mammalian and Sf9 insect cells were damaged by 1 microgram ml-1 KAR-2, as observed by indirect immunofluorescence and transmission electron microscopy. Scanning electron microscopy revealed intensive surface blebbing on both types of cells in the presence of KAR-2. 4. KAR-2 was effective in the mouse leukaemia P338 test in vivo without significant toxicity. Studies on a primary cerebro-cortical culture of rat brain and differentiated PC12 cells indicated that the toxicity of KAR-2 was significantly lower than that of vinblastine. The additional property of KAR-2 that distinguishes it from bis-indol derivatives is the lack of anti-calmodulin activity.

Animals↗
PubMed1997

Quality of healthcare related software applications--setting up an accreditation system in Hungary.

Meeting expectations of high quality health care, the safe and secure operation of medical information systems is a "must". However for healthcare software nationwide quality control systems are not widely used. A quality control project of health care applications in Hungary has been launched in 1996 by the Hungarian Society of Healthcare Informatics (MEIT) and Medico-Biological Section of Johann Neumann Society of Computing (NJSZT) by establishing a joint Healthcare Informatics Applications Accreditation Board (Board ESAB). The Board developed an evaluation methodology and a legal procedure to test health care software application modules. The evaluation method is based on international standards as ISO-9126 and on emerging European standards of CEN/TC 251. First rounds of accreditation already proved that there is a need among providers and users for the accreditation process. The authors hope that establishing an accreditation system will lead to a more balanced health care software market where users have an opportunity to inform themselves by the opinion of independent experts on the product they intend to purchase.

Accreditation↗
PubMed1997

Our preliminary results in application of Stoppa technique for recurrent groin hernia.

In 1994 we have started the Stoppa technique which was only used for the recurrent groin hernia repair, when Mersilene mesh was implanted in preperitoneal position from a lower midline incision. From March, 1994 to March, 1996 seventeen Stoppa procedures were performed in our department (14 men, 3 women, mean age of 66 years). Type of hernias: 13 unilaterale, 3 bilaterale recurrent groin hernias and 1 primary bilaterale groin hernia combined with a lower midline incisional hernia. Operations were performed by 7 surgeons. The mean time of the surgery was 85 min. (35-165). The mean postoperative stay in the hospital was 9 days (7-19). The Stoppa technique could be performed in all patients. Serious early postoperative complications didn't occur. The two late recurrences were observed amongst the first five patients. All implanted mesh were well tolerated by the patients. Author believe, this procedure has some advantages: the site of the incision is located in a new place from where the dissection is easier than in the previous incision, the stich fistulas from the previous operation can be avoided, furthermore this method could be applicated for combined hernias located in the lower part of abdomen and it is cheaper than the laparoscopic hernioplasty.

Aged↗
PubMed1997

Morphology of cystic renal lesions. Lectin and immuno-histochemical study.

Renal cystic disease include heritable, developmental and acquired disorders. Morphological features were extensively studied mainly in cases of autosomal dominant polycystic and experimentally induced cystic disorders. We report the immunohistochemical (cytokeratin, epithelial membrane antigen, vimentin, Tamm-Horsfall protein, proliferating cell nuclear antigen) and lectin-binding (soybean agglutinin, Dolichos biflorus agglutinin) profile of cystic kidneys from 9 surgically removed and 21 autopsy cases. The primary renal diseases displayed great diversity. Beside polycystic kidney diseases we studied cysts associated to renal neoplasm, hemodialysis, nephrosis syndrome and chronic transplant rejection. Cystic epithelium demonstrated positive reactions with distal tubular markers (epithelial membrane antigen, cytokeratin) or collecting duct (soybean agglutinin, Dolichos biflorus agglutinin) and Henle loop markers (Tamm-Horsfall protein) but the latter in lesser extent. The large number of the vimentin positive cases are suggestive to dedifferentiation or cellular regeneration. The former might be underlined by the diffuse cytoplasmic or basolateral membrane staining of the epithelial membrane antigen in some cystic epithelial cells. Not the cystic epithelium but rather the neighbouring non-dilated tubular cells and interstitial cells presented proliferative activity which was most intense in areas where vimentin and variable nephron segment markers in the same tissue were expressed. Positive reaction of the type IV basement membrane collagen and the rate of the inflammation failed to show similar connection. This finding suggests the importance of the inflammatory cells in the development and/or expansion of the cysts.

Cell Differentiation↗
PubMed1997

Results with collagen fleece coated with fibrin glue (TachoComb). A macroscopical and histological experimental study.

Diffuse bleeding from parenchymatous organs at conventional surgery is eliminated with the usual methods coagulation tamponade or styches. We performed experimental series at 9 dogs. After resection of spleen, liver, pancreas and kidney, the bleeding surface was covered by collagen fleece coated with fibrin glue (TachoComb). Postoperatively 7 days, 10 days, 14 days and 28 days we made a relaparotomy. Then the results were analyzed macroscopically and microscopically. In the abdominal cavity neither significant quantity of blood nor greater adhesions were detected. At all cases the fibrin glue was found on place were it was put before. Histologically a perfect wound healing experienced. The fibrin glue (TachoComb) using at diffuse parenchymatous organs' bleeding give a very good results when the wound area is at least 1 cm beyond the immediate wound margin and the fibrin glue is applied onto the wound and pressed on it for 4-5 minutes.

Animals↗
PubMed1997

Protection of the renal artery in nephron-sparing surgery. I. Pathomorphological study.

It is necessary to clamp the renal artery for some time in renal surgery to preserve the organ. Not only the renal parenchyma but also the wall of the clamped renal artery may be damaged due to known ischaemic-reperfusion causes. Regional venous renal hypothermia induced by intracellular solutions (Sacks II, Euro-Collins) could provide protection against damage of the vessel wall caused by reperfusion or clamping in our experiments, in cases of clamping for 30 minutes, probably because it also ensured the cooling of the surface of the vessel wall. Similar vasoprotective effect could be achieved by systematic antioxidant treatment (MTDQ-DS) and regional renal hypothermia given in combination. Harmful effects of 45-minute clamping could be best avoided by applying antioxidant treatment alone. While there were no significant morphological changes in the renal arteries the persistent endothelial damage may trigger further complications like renal ischaemic condition.

Animals↗
PubMed1997

Protection of the renal artery in nephron-sparing surgery. II. Arterial contractility investigations.

It has been well known that reperfusion following ischaemia may cause functional and structural damage to not only the organ involved but also the blood vessels supplying that organ. As in organ-sparing renal surgery it is inevitable to clamp the renal artery for some time, it is expected that reperfusion, following the removing of clamping, causes structural changes in the vessel wall which may result in a decrease in arterial function. In our model experiments on animals, the left renal arteries were atraumatically clamped for 30, 45 and 60 minutes. Simultaneously with clamping, perfusion regional renal venous cooling was applied to some of the animals, together with nephrotomy. In some cases cooling was performed in combination with antioxidant treatment. On the 3rd postoperative day renal arteries from both sides were removed, the right, intact ones serving as control. Noradrenaline dose effect curves characterizing vessel contractility were determined to demonstrate functional changes. It was established that cooling the renal artery for only 30 minutes was enough to rule out the damage due to ischaemia-reperfusion. If clamping lasted for 45 minutes, venous cooling of the kidney in combination with antioxidant treatment was necessary to spare arterial function. Clamping for 60 minutes resulted in irreversible/permanent decrease in contractility even if hypothermia and antioxidant treatment were given simultaneously.

Animals↗