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Biomedical subjects

J Kovarik

Publications and source records attributed to J Kovarik.

At least 55 records · Page 3Linked to original sources
PubMed1996

Impact of high-dose oral acyclovir prophylaxis on cytomegalovirus (CMV) disease in CMV high-risk renal transplant recipients.

Recent studies showed contradictory results concerning the efficacy of oral acyclovir in the prevention or amelioration of cytomegalovirus (CMV) disease after renal transplantation (TX). This study evaluated the incidence and severity of CMV disease within the first year after TX in high-risk renal transplant recipients (CMV-seropositive donor, seronegative recipient) treated prophylactically with oral acyclovir (800 to 3200 mg/day) over a period of 12 wk (ACY, N = 22), compared with high-risk patients randomly assigned as controls (CO, N = 10). Follow-up for CMV infection included serological determination of CMV-specific immunoglobulin G and immunoglobulin M antibodies, antigen detection in peripheral blood leukocytes (PP 65), shell vial culture (blood), and virus isolation/early antigen detection (urine). Severity of CMV disease was quantified by a scoring system for CMV-related symptoms. Nine patients (40.1%) in the acyclovir group and four patients (40%) in the control group developed CMV disease. Neither severity (ACY, 11.4 versus CO; 12.5 points score), nor duration of disease (ACY, 21 days; CO, 22 days), nor transplant function at the end of the observation period differed significantly. The onst of CMV disease was not delayed significantly in acyclovir-treated patients compared with controls (ACY, 47 +/- 34 days versus CO, 27 +/- 14 days after TX, not significant). Our results show no beneficial effect of oral acyclovir prophylaxis in CMV high-risk renal transplant recipients.

Acyclovir↗
PubMed1995

Early tolerance of different organs to fast fractionation in clinical practice.

PURPOSE: To assess the feasibility of accelerated hyperfractionated radiotherapy in the treatment of breast, abdominal cavity, and pelvic tumors. METHODS AND MATERIALS: Between August 1989 and March 1993, 39 patients were treated in Portsmouth by an accelerated, hyperfractionated regimen giving 45 to 54 Gy three times a day over 12 days. Twenty patients had abdominal cavity or pelvic tumors and 19 patients breast carcinoma, 9 of whom were treated prophylactically after local excision. RESULTS: No local recurrence has been observed in the 19 patients with breast carcinoma, and out of the 20 with abdominal or pelvic tumors, 6 showed complete regression and so far no severe late damage has been observed. In those patients who had pelvic or abdominal tumors treated, the acute toxicity varied widely from minimal to very intensive. No surgical intervention was necessary and most reactions settled within a 6-week period. CONCLUSION: Accelerated fractionation by small increments is well tolerated by the breast, pelvic, and abdominal organs.

Abdominal Neoplasms↗
PubMed1995

p53 derived from human tumour cell lines and containing distinct point mutations can be activated to bind its consensus target sequence.

Mutation of the p53 gene is one of the most common genetic lesions observed in human cancer. The p53 protein functions as a transcription factor, however it is still unresolved to what extend this property is related to its tumour suppressor activity. Since there is evidence that protein modifications as well as protein-protein interactions may regulate p53 function, we have studied p53 protein-DNA complex formation in nuclear extracts prepared from human tumour cell lines. In 13 different cell lines PAb421-induced DNA binding activity was compared to the level and conformation of the endogenous p53 protein. Surprisingly, sequence-specific p53 DNA binding activity was detected not only in cell lines that express wild-type p53, but also in seven cell lines which contain only mutant protein. Oligonucleotide competition analyses with various p53 target sequences and methylation interference experiments establish that wild-type and mutant p53 differ significantly in their sequence-specific interactions. Our analysis also provides evidence that the PAb1620 conformation is neither sufficient nor essential for DNA binding of endogenous p53 and that the cellular environment in addition to the specific point mutation may influence p53 DNA binding activity.

Base Sequence↗
PubMed1995

High dose-rate microselectron molds in the treatment of skin tumors.

PURPOSE: The feasibility of high dose rate iridium afterloaded molds in the treatment of skin tumors. METHODS AND MATERIALS: Expanded silicone rubber and bronchial applicator tubes were used in the construction of various molds. The number of tubes used and the separation between them depends on the size and area to be treated. Source dwell position and time are set to follow Paterson-Parker rules. Single plane expanded silicone rubber molds between 15 X 15 mm and 60 X 70 mm were used in 120 different sites, and of the others, seven were perspex double molds, two were cylindrical applicators, and one was a partially shielded intranasal applicator. One hundred and thirty lesions of various site and histology were treated in all. After exclusion of treatments that were combined with either external beam or chemotherapy, 106 lesions (76 patients) were evaluated. RESULTS: Full response was obtained in all but four basal cell carcinomas. The acute reaction ranged from moist desquamation (27 sites) to erythema only. Follow-up at 5 or more months revealed no changes whatever in 47 sites; 53 showed an excellent cosmetic outcome, although slight changes in pigmentation or minimal atrophy was demonstrable and 6 sites became noticeably atrophic with patchy pigmentation. For 9.6 months of average follow-up time, no recurrences have been observed. CONCLUSION: The high-dose-rate iridium-loaded skin applicators offer the possibility of improved therapeutic ratio in the treatment of superficial skin tumors. With the availability of a high-dose-rate afterloader this technique is simple and straightforward.

Aged↗
PubMed1995

Conformational changes in p53 analysed using new antibodies to the core DNA binding domain of the protein.

The p53 protein contains a protease resistant core section that binds to DNA in a sequence specific manner and whose crystal structure has been determined. This core is flanked at the N-terminus by the transcriptional transactivation domain and at the C-terminus by sequences involved in the oligomerisation of the protein. Extensive immunochemical analysis of p53 has shown that dominant antigenic sites lie within these N- and C-terminal domains while few antibodies to the central core have been identified. One of these, PAb240, has been extensively characterised as its epitope is cryptic in the native DNA binding core structure but is exposed by denaturation. This epitope is also exposed on many p53 proteins that contain point mutations in the core domain suggesting that these mutations may have a common affect on the structure of the core. To investigate this further we have generated several new antibodies to novel sites on p53 and mapped their epitopes using synthetic peptides. We find that antibodies to two other discrete sites in the core can also, like PAb240, recognize cryptic epitopes and distinguish mutant from wild-type conformations implying that the point mutations found in p53 in human tumours have widespread effects on the folding pattern of the DNA binding domain.

Amino Acid Sequence↗
PubMed1995

Immunoregulation and drug treatment in chronic relapsing experimental allergic encephalomyelitis in the Lewis rat.

Chronic relapsing experimental allergic encephalomyelitis (CR.EAE) was induced by immunizing Lewis rats with total guinea-pig spinal cord (GPSC) tissue emulsified in enriched complete Freund's adjuvant (CFA). The proliferative responses of draining inguinal and popliteal lymph node cells to GP.MBP, purified protein derivative (PPD) and concanavalin A (ConA) appeared significantly modulated according to the clinical state of the animals. Responses appeared significantly decreased in both lymphoid compartments during the recovery periods compared with that during relapses. Therapeutic treatment of CR.EAE with cyclosporin and different lysolecithin derivatives, such as ET-18-OCH3, SRI 62-843 and MLS 266-337, starting at the spontaneous remission of the first disease bout, could suppress the manifestation of further relapses. Whereas cyclosporin only delayed the onset of the disease relapse until discontinuation of treatment, all lysolecithins showed a curative effect in most animals. Plasma corticosterone levels measured at different time points in placebo, cyclosporin and MLS 266-377-treated rats showed a strong correlation with the clinical state of the animals. High corticosterone levels were detected during stages of acute paralysis, whereas a decrease to normal levels was noted during each recovery phase.

Animals↗
PubMed1995

Absence of p53 autoantibodies in a significant proportion of breast cancer patients.

We analysed antibodies specific for human p53 in sera from primary breast cancer patients using three different immunoassays and we related these results to the p53 level in tumour tissue detected by immunohistochemistry. Only 44% (11/25) of apparently enzyme-linked immunosorbent assay (ELISA)-positive sera were from patients with a high level of p53 protein in more than 50% of their tumour cells. Surprisingly, 36% (9/25) of the sera originated from patients with no detectable p53 protein at all. Immunoprecipitation data suggested that the reason for this discrepancy is that at least some of the antibodies detected as positive in the ELISA in these sera from patients with clinical stage I and stage II breast cancers may be induced by immunogens other than p53 protein. Many of these reactions give apparently positive signals in a variety of p53 assays, and very stringent analysis is required to avoid possible misinterpretation of these responses as a p53-specific B-cell response in human cancer patients.

Autoantibodies↗
PubMed1995

MDR1 gene expression in lymphocytes of patients with renal transplants.

The MDR1 gene, a multidrug resistance gene, codes for P-glycoprotein which pumps hydrophobic drugs out of the cells. Since cyclosporins also bind to P-glycoprotein and might be pumped by this transmembrane protein, we determined the expression of the MDR1 gene in the lymphocytes of 32 patients with renal transplants. MDR1 RNA expression of lymphocytes was measured by slot blot analysis and compared to the expression of drug-sensitive KB-3-1 cells and multidrug-resistant KB-8-5 cells. MDR1 RNA expression was detected in the lymphocytes of 9 (28%) patients, whereas no expression was seen in the remaining 23 patients. No association between MDR1 RNA expression and transplant function or hematological parameters was observed. However, none of the 6 patients who had transplants for more than 40 months expressed the MDR1 gene in their lymphocytes. In conclusion, expression of the MDR1 gene does occur in lymphocytes of patients with renal transplants and might reduce the immunosuppressive efficacy of cyclosporins through enhanced efflux of cyclosporins.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

A comparison of organ cultured fetal pancreas allo-, iso-, and xenografts (pig) in non-immunosuppressed non-obese diabetic mice.

The response of non-immunosuppressed non-obese diabetic/Lt mice to an isograft (H-2g7), major histocompatibility complex-mismatched allografts (CBA, H-2K; BALB/c, H-2d), and xenograft of fetal pig pancreas was assessed by light microscopy. In non-obese diabetic mice, isografts were rapidly invaded by lymphoid cells, and the graft pathology was similar to that in the host pancreas. In prediabetic mice the graft site was invaded by small mononuclear cells (CD4 and CD8+ve T cells) and macrophages, and in diabetic mice specific beta-cell destruction was found. The allografts were invaded and destroyed within 10 to 14 days by mononuclear cells that included many blast cells. In the allograft sites the infiltrating cells soon disappeared, and within 3 weeks only a scar remained. The xenografts, in contrast, were invaded by macrophages and eosinophils with some neutrophils and mast cells and multinucleated giant cells. Xenograft destruction also occurred over 8 to 10 days, but the site remained large and swollen with a central necrotic zone and massive fibrosis forming a large granuloma, and the infiltrate persisted for many weeks. Thus, there are marked differences in the host response to a challenge with tissue that is prone to cell-specific autoimmune disease, to a graft of immunogenic allogeneic tissue, and to a transplant of discordant xenogeneic islets. Because of the differences in the host response to these grafts different immunosuppressive strategies may be needed to cope with their destruction.

Animals↗
PubMed1994

Specific down-regulation of proliferative T cell alloresponsiveness by interference with CD2/LFA-3 and LFA-1/ICAM-1 in vitro.

T cell activation requires Ag contact with the TCR in the presence of costimulatory signals provided by APCs. When Ag is presented without costimulation, T cells are functionally inactivated. Here we demonstrate that interference with distinct adhesion molecules during Ag contact using mAbs leads to Ag-specific functional inactivation of alloreactive T cells. We found that the presence of a mixture of mAbs specific for CD2, LFA-3, LFA-1 alpha- and beta-chain, and ICAM-1 during primary MLC leads to down-regulation of secondary proliferative responses to Ag from the donor used for priming. Cells from pretreated cultures proliferated well, however, when stimulated with Ag from third party donors, mitogens, or mitogenic CD3 mAb. Because specific reactivity could be restored by addition of IL-2 to restimulation cultures, altered secondary responsiveness appeared to be caused by anergy and not by elimination of specific clones. Furthermore, specific down-regulation of alloresponsiveness was prevented by addition of IL-2 to primary cultures in the presence of mAb. Interference by mAb with either CD2/LFA-3, LFA-1/ICAM-1, CD2/LFA-1, or LFA-3/ICAM-1 had a substantial, though less pronounced effect on secondary responsiveness. After pretreatment with the Ab mixture, CTL generation was substantially but incompletely down-regulated against the original and third party donors. Because a decrease in the reactivity of unstimulated responders by culture was also observed, these findings might be explained by the loss of cytotoxic precursors after culturing under nonstimulating conditions. In conclusion, our data demonstrate that T cells enter a state of anergy when T cell activation is modulated by simultaneous interference with distinct adhesion molecules during Ag contact, which thus might reflect at least partly overlapping functions of particular receptor-ligand pairs in T cell costimulation.

Antibodies, Monoclonal↗
PubMed1994

The viable motheaten (mev) mouse--a new model for arthritis.

Homozygous mev mice are first identified at the age of 3-4 days by focal depigmentation of the skin, followed by patchy absence of hair and by necrotic lesions on paws, tail and ears. Of particular interest are the inflammatory reactions in the paws of these animals which consist mainly of polymorphonuclear and mononuclear cell infiltration in the subcutaneous tissue extending to the periosteum and joint, resulting in focal destructive arthritis and osteomylitis. These lesions are to some extent reminiscent of an acute form of rheumatoid-like arthritis. Since mev mice are sterile, a limited number of symptomatic offspring can be obtained by cross-breeding their heterozygous siblings which are phenotypically not distinguishable from mice lacking this mutation. In order to produce a sufficient number of diseased animals for performing pharmacological studies, we have established a model by transferring this disease in lethally irradiated, 8- to 10-week-old syngeneic mice which were grafted with mev spleen cells. Such reconstituted recipients develop first inflammatory symptoms of the paws 2 to 3 weeks after cell transfer. The arthritic inflammation finally affects all paws and toes by 30 to 50 days. This procedure increased the number of mev-like mice expressing arthritis, allowing assessment of the effects of standard reference drugs used in the therapy of rheumatoid arthritis (RA). The immunosuppressants cyclosporin and rapamycin and the steroid dexamethasone at therapeutic concentrations exert a strong inhibitory effect on the development of arthritis in this novel model. In contrast, the non-steroidal anti-inflammatory drug phenylbutazone shows only a moderate effect. These results indicate the particular sensitivity of this model for efficacy of potentially new therapeutic but non-cytostatic compounds for clinical use.

Animals↗
PubMed1994

Recombinant human erythropoietin in renal transplant recipients with renal anemia.

Thirty-seven kidney graft recipients with chronically declining transplant function accompanied by renal anemia were treated with recombinant human erythropoietin for 3 months. In all these patients anemia improved and mean hemoglobin levels increased from 7.67 +/- 1.26 g/dl to 9.83 +/- 1.94 g/dl (p < 0.01). Mean creatinine increased from 4.23 +/- 1.82 to 4.62 +/- 2.42 (p < 0.05) but the progression of transplant failure was not influenced when compared with pretreatment values obtained at least 6 months before study entry. Mean blood pressure levels were not altered but 12 patients required additional antihypertensive medication.

Adult↗
PubMed1993

Reactive oxygen product formation after Fc gamma receptor-mediated neutrophil activation by monomeric mouse IgG2a: implications for the generation of first dose effects after OKT3 treatment.

In the present study, we provide evidence that IgG2a monoclonal antibody (mAb) OKT3 is able to induce reactive oxygen intermediate (ROI) formation in polymorphonuclear leukocytes (PMN) when Fc gamma RIIIB as well as Fc gamma RII are bound concomitantly. Inhibition of binding to either Fc gamma R by specific mAb (3G8 or IV.3, respectively) resulted in complete abrogation of the OKT3-induced respiratory burst. The effect of OKT3 was independent from its specificity and thus also from its T cell-activating property, since nonbinding IgG2a isotype controls induced similar amounts of ROI. The IgG2b mAb BMA031 as well as the respective nonbinding isotype control were only minimally effective. With regard to the potential role of PMN activation in inflammation and tissue damage, our findings offer an extended explanation for the generation of initial adverse reactions to OKT3. Thus, one might speculate that the concerted action of cytokines liberated after its administration, what may lead to margination of leukocytes, and activation of PMN via Fc gamma R might produce first-dose reactions to OKT3 by directing radical-mediated damage against the endothelium.

Animals↗