PubMed Health⌕ Search

Biomedical subjects

G Molnar

Publications and source records attributed to G Molnar.

At least 19 recordsLinked to original sources
PubMed2002

Influence of the irradiation temperature on the dosimetric and high temperature TL peaks of Al2O3:C.

The TL glow curves of Al2O3:C crystals have been investigated as a function of the irradiation temperature. The nature of the observed TL peaks has been studied by optical annealing. The filling of traps was found strongly dependent on the irradiation temperature in the case of UV exposure, which has been explained by the temperature dependence of the photoionisation of F centres. This latter phenomenon could have a part in the luminescence quenching and UV bleaching of F centres.

Aluminum Oxide↗
PubMed1998

HIV-1 diversity in Romania.

OBJECTIVES: To evaluate the prevalence and the dynamics of HIV-1 subtypes in Romanian adults and children, and to investigate the origins of the nosocomial epidemic. DESIGN: A total of 1000 serum and plasma samples, from adults (n = 579) and children (n = 421) who were diagnosed as being HIV-1-infected during 1990-1997 in 39 of the 41 Romanian districts, were serotyped. Viral DNA was isolated from blood samples of 84 patients and the viruses were genotyped. METHODS: Serotyping was performed with a peptide subtype-specific enzyme immunoassay (SSEIA), based on in vitro competition for antibody binding between the representative V3 peptides of the different clades (A-F). Proviral HIV-1 DNA was genotyped by heteroduplex mobility assay or by sequence analysis of the C2-V3 env region. RESULTS: SSEIA showed that 93% of the samples from horizontally infected children were serotype F, 1% were serotype B, and the remaining 6% were uninterpretable. In vertically infected children, 74% of strains were serotype F, 10% were serotype A, 3% were serotype B, and 3% were serotype E. Serotype F was also the dominant subtype in adults (68%), but serotypes A, B, C, D and E were also detected. SSEIA gave indeterminate results in 7% of cases. A strong correlation (90%) between serotyping and genotyping for subtype F was found. Analysis of the relative incidence of the different serotypes over a 7-year period (1990-1997) showed a stable distribution. CONCLUSIONS: Subtype F largely dominates the epidemiology of HIV-1 infection in both children and adults in Romania, although other major subtypes are present. The predominance of subtype F in Romania may be a future potential source of HIV-1 variability in Europe.

Adult↗
PubMed1998

3'-end cDNA pool suitable for differential display from a small number of cells.

We have generated a 3' cDNA pool from the RNA of only 1000 or fewer cells by reverse transcription (RT) from an extended oligo(dT) primer with a 3' degenerate base and a second strand primer with four degenerate 3' bases, followed by PCR. Reproducible differential displays (DD) can be made from this essentially inexhaustible source of DNA. The method produced DD patterns that are comparable but not identical in band number and size distribution with those obtained by the original RT-DD technique. Northern blots performed with the excised bands verified altered gene expressions. The data indicate that this 3'-end cDNA pool can supplement current PCR-based methods of expression genetics. This pool of cDNA sequences also provides a reliable source for primer-specific gene amplifications.

Blotting, Northern↗
PubMed1997

Skeletal muscle satellite cells cultured in simulated microgravity.

Satellite cells are postnatal myoblasts responsible for providing additional nuclei to growing or regenerating muscle cells. Satellite cells retain the capacity to proliferate and differentiate in vitro and, therefore, provide a useful model to study postnatal muscle development. Most culture systems used to study postnatal muscle development are limited by the two-dimensional (2-D) confines of the culture dish. Limiting proliferation and differentiation of satellite cells in 2-D could potentially limit cell-cell contacts important for developing the level of organization in skeletal muscle obtained in vivo. Culturing satellite cells on microcarrier beads suspended in the High-Aspect-Ratio-Vessel (HARV) designed by NASA provides a low shear, three-dimensional (3-D) environment to study muscle development. Primary cultures established from anterior tibialis muscles of growing rats (approximately 200 gm) were used for all studies and were composed of greater than 75% satellite cells. Different inoculation densities did not affect the proliferative potential of satellite cells in the HARV. Plating efficiency, proliferation, and glucose utilization were compared between 2-D culture and 3-D HARV culture. Plating efficiency (cells attached divided by cells plated x 100) was similar between the two culture systems. Proliferation was reduced in HARV cultures and this reduction was apparent for both satellite cells and nonsatellite cells. Furthermore, reduction in proliferation within the HARV could not be attributed to reduced substrate availability because glucose levels in medium from HARV and 2-D cell culture were similar. Morphologically, microcarrier beads within the HARV were joined together by cells into 3-D aggregates composed of greater than 10 beads/aggregate. Aggregation of beads did not occur in the absence of cells. Myotubes were often seen on individual beads or spanning the surface of two beads. In summary, proliferation and differentiation of satellite cells on microcarrier beads within the HARV bioreactor results in a 3-D level of organization that could provide a more suitable model to study postnatal muscle development than is currently available with standard culture methods.

Animals↗
PubMed1996

Starch synthesis, and tuber storage protein genes are differently expressed in Solanum tuberosum and in Solanum brevidens.

Studying in vitro stem cuttings of Solanum tuberosum induced for tuberization and those of a non-tuberizing Solanum species, differences both in morphology and in gene expression were detected. Stolon formation essentially depended on light while tuberization was triggered by the elevated level of sucrose in the medium. Genes involved in starch synthesis were induced by sucrose in both species, however, starch granules were detected only in potato. A new tuber specific cDNA clone, GM7, encoding a putative metallocarboxypeptidase inhibitor and the cDNA of a proline rich cell wall protein with S. brevidens specific expression were isolated by differential screening. Sucrose mediated transcription of the tuber storage proteins like patatin and proteinase inhibitors (Kunitz-type, winI, GM7) failed in S. brevidens.

Amino Acid Sequence↗
PubMed1996

Evidence for multiple satellite cell populations and a non-myogenic cell type that is regulated differently in regenerating and growing skeletal muscle.

We have performed studies to determine if different populations of satellite cells provide nuclei to growing and regenerating skeletal muscle fibers. Satellite cells were isolated from regenerating or growing anterior tibialis muscles, and their phenotypic properties were compared in vitro. Isolates from regenerating muscle contained 31% satellite cells, and those from control muscle contained 66% satellite cells, as determined by their expression of desmin. Among the desmin-positive satellite cells present from each preparation, two distinct populations of satellite cells were evident. Approximately 28% of satellite cell colonies were composed of only large cells, contained less than 50 cells/colony, and were designated as type 1 colonies. The remainder of satellite cell colonies isolated from either regenerating or control muscles were primarily composed of small cells, contained from 60 to 150 cells/colony, and were designated as type 2 colonies. Despite dramatic differences in the ratio of myogenic to non-myogenic cell types, satellite cells from regenerating and control muscles formed myotubes and expressed myosin heavy chain at similar levels. Treatment of regenerating cultures with dexamethasone resulted in a 16% increase in the number of desmin-positive colonies and dramatically decreased the proliferation of non-myogenic cells. These results suggest that at least two distinct populations of satellite cells can be isolated from regenerating and control skeletal muscles, and that non-myogenic cells are differentially regulated in regenerating versus non-regenerating environments.

Animals↗
PubMed1995

Quantification of DNA-protein interaction by UV crosslinking.

Measurement of the affinity of a protein for a promoter sequence is critical when assessing its potential to regulate transcription. Here we report that the DNA protein crosslinking (DPC) assay can be used to measure affinity, amount and molecular weight of DNA binding proteins to specific and non-specific DNA sequences. By applying a theoretical analysis to evaluate the binding data, it was shown that the affinity constants of two proteins (named DPC80 and DPC107) to the MT3 region of the mouse thymidine kinase promoter were 2 x 10(-9) M, which is 10(4) times higher than to non-specific DNA. Similar affinity constants were found when the purified proteins corresponding to DPC80 and DPC107 instead of nuclear extracts were used to assess the reliability of the DPC assay. A value for crosslinking efficiency was determined as 0.07, however, it is not needed for computation of the DNA-protein affinity, but with it the abundance of a binding protein can be estimated. In summary, the DPC assay is useful for quantifying DNA binding proteins and thereby judging their influence on transcription.

3T3 Cells↗
PubMed1994

Cyclin D1/cdk2 kinase is present in a G1 phase-specific protein complex Yi1 that binds to the mouse thymidine kinase gene promoter.

Our studies provide evidence for the presence of cyclin D1 in an early G1 cycle-specific DNA binding complex Yi1. Previously we identified several complexes including Yi and E2F that at different times during G0 to S transition bind to three distinct DNA sequences (MT1, MT2, MT3) located in the mouse thymidine kinase upstream promoter. These various complexes contain DNA binding proteins (Sp1, E2F, p110, p60), cyclins A and E, cyclin-dependent kinase 2 (cdk2), and retinoblastoma-related proteins (pRB, p107). Here we report that Yi1 is different from the E2F complexes. Yi1 contains cyclin D1/cdk2 kinase as shown by using specific antibodies to cyclins, cdks and the Yi1 DNA-binding protein in gel retardation, western blotting, and immunoprecipitation assays. Yi1 binding is specific to a consensus sequence different from that of E2F.

3T3 Cells↗
PubMed1994

Cyclin E, a potential prognostic marker for breast cancer.

A fundamental cause of cancer is changed properties of genetic material, which may deregulate normal development of the tissue or provide selective growth advantage to the tumor cell. This deregulation of cell proliferation results from altered production of a handful of proteins that play key roles in progression through the eukaryotic cell cycle. Some of these proteins include tumor suppressor genes or oncogenes. However, no one general change or alteration of a critical gene has yet been found in all cancers. Using surgical material obtained from patients with various malignancies, we show that breast cancers and other solid tumors, as well as malignant lymphocytes from patients with lymphatic leukemia, show severe quantitative and qualitative alterations in cyclin E protein production independent of the S-phase fraction of the samples. Hence, these alterations represent a true difference between normal versus tumor tissue. In addition, in breast cancer, the alterations in cyclin E expression become progressively worse with increasing stage and grade of the tumor, suggesting its potential use as a new prognostic marker.

Biomarkers, Tumor↗
PubMed1994

The immediate-early gene Egr-1 regulates the activity of the thymidine kinase promoter at the G0-to-G1 transition of the cell cycle.

Production of thymidine kinase (TK) protein parallels the onset of DNA synthesis during the cell cycle. This process is regulated at transcriptional, posttranscriptional, and translational levels to cause a 40- to 50-fold increase in cytosolic enzymatic activity as cells progress from G1 to S phase. Transcriptional activation of the mouse TK gene through the cell cycle is dependent upon previously characterized cis elements of the proximal promoter, called MT1, MT2, and MT3, that bind at least two different complexes: TKE during the transition of cells from quiescence (G0) to G1, and Yi later at the G1/S boundary. To identify the transcription factors involved in this regulation, we screened a mouse fibroblast cDNA expression library with a labeled MT3 oligonucleotide probe and isolated a clone that encodes Egr-1, an immediate-early transcription factor, whose expression is regulated by serum or growth factors during the G0-to-G1 transition when cells reenter the cell cycle. Electrophoretic mobility shift assays demonstrate that Egr-1 is involved in the TKE complex that binds to the MT3 element and that expression of Egr-1 induces transcription of a mouse TK-chloramphenicol acetyltransferase reporter in transient transfections. These results suggest a role for Egr-1 in regulating expression of the TK gene at the G0-to-G1 transition.

Animals↗
PubMed1993

The thymidylate synthase inhibitor, ICI D1694, overcomes translational detainment of the enzyme.

We have investigated the mechanism of inactivation of thymidylate synthase (TS) by ICI D1694 (a folate-based quinazoline) in normal versus tumor-derived human mammary epithelial cells. ICI D1694 is a very potent cytotoxic agent against these cells with IC50 values of 1-2 nM. Its growth inhibitory activity was completely reversed by the addition of thymidine, confirming that TS is its sole target in these cells. Remarkably, TS protein levels rose by 10-40-fold following treatment with ICI D1694, depending on cell type, while TS mRNA levels remained constant. The mechanism appears to be a release of "detainment" of TS translation, since addition of cycloheximide, a translational inhibitor, blocked the TS protein levels from rising. But coadministration of 5,6-dichlorobenzimidazole, a transcriptional inhibitor, did not overcome protein accumulation, nor did thymidine which overcomes growth inhibition by ICI D1694. 5,10-Methylenetetrahydrofolate (via folinic acid), however, did block the effects of ICI D1694, showing that the drug has its effect upon both detainment and enzyme inhibition by binding to the folate substrate site of TS. In addition, in the presence of ICI D1694, TS protein was no longer cell cycle-regulated as evident by its constitutive expression in synchronized cells. This accumulation and constitutive expression of TS induced by D1694 should increase drug resistance under a clinical setting. We suggest that an ideal inhibitor of TS would target the TS allosteric site that binds to TS mRNA, responsible for specific translation of the protein, thereby complimenting inactivation of the enzyme.

Cell Cycle↗
PubMed1991

Cytometric analysis of DNA replication inhibited by emetine and cyclosporin A.

DNA staining methods based on aspecific interactions with dye molecules have been replaced by an immunofluorescent approach to measure DNA replication. Biotin-11-dUTP was incorporated into permeable thymocytes isolated after emetine or cyclosporin A treatment of mice. Active sites of DNA replication were amplified based on biotin-avidin interaction and verified under fluorescent microscope. Cytometry of fluorescent images allow the direct measurement of replicating DNA without aspecific detection of total cellular DNA. Cytometric analysis of replication revealed that emetine acts at the early S phase, while cyclosporin A blocks in vivo DNA synthesis at mid S phase.

Animals↗
PubMed1991

Prodromal symptoms and intermittent drug medication in mood disorders.

There has been very little interest in research on prodromal symptoms of mood disorders. This paper reviews the literature concerned with bipolar disorder and unipolar depression. In both illnesses, recent preliminary studies would suggest that within each patient there is a striking consistency in prodromal symptoms preceding each episode. Since the appearance of prodromal symptoms generally precedes the full syndrome by weeks or months, the findings pave the way for the intermittent use of medications (antidepressants and lithium) in mood disorders.

Antidepressive Agents↗
PubMed1991

Plantar weight-bearing pattern in idiopathic scoliosis.

Eighty-four patients were objectively evaluated with a weight-bearing pattern analyzer to determine whether spine deformity has an effect on the amount of weight borne on the right versus left foot and on the fore versus the hind foot. Patients with idiopathic scoliosis treated with bracing and surgery and patients with Scheuermann's kyphosis treated with bracing were compared with control subjects. Patients with right thoracic and thoracolumbar curves did not bear more weight on the right foot, as was previously thought. Patients with relatively unaffected lumbar spines exhibited normal sagittal plane weight-bearing patterns, whereas patients with double major and lumbar curves did show abnormalities in the weight-bearing pattern. Bracing of curves less than 40 degrees did not alter the plantar weight-bearing pattern, but it did significantly alter the pattern in curves greater than 40 degrees. Surgically treated patients were found to have increased hindfoot weight-bearing irrespective of the curve type or surgery.

Adolescent↗
PubMed1990

Altered glycosaminoglycan composition in reactive and neoplastic human liver.

We have investigated the glycosaminoglycan composition of normal human liver, focal nodular hyperplasia, hepatic adenoma, and hepatocellular carcinoma. Uronic acid increased about 4 fold in the benign and reactive lesions, and greater than 7 fold in the carcinoma. Whereas in focal nodular hyperplasia and adenoma dermatan sulfate was the predominant glycosaminoglycan, in hepatocellular carcinoma chondroitin sulfate was the predominant species; it increased 24 fold over normal liver and 3-5 fold over all the other tissues. HPLC analysis of chondroitinase ABC or AC digests showed a 58 fold increase in Delta-Di-OS disaccharides in hepatocellular carcinoma, indicating significant undersulfation of chondroitin sulfate. Surprisingly, the normal-appearing liver surrounding the carcinoma showed glycosaminoglycan changes similar to adenoma and nodular hyperplasia. These results thus indicate that specific glycosaminoglycan changes occur in hepatocellular carcinoma, and suggest for the first time that proteoglycan metabolism is also altered in the non-cirrhotic, hepatic parenchyma adjacent to liver carcinoma.

Adenoma↗