Biomedical subjects

R Silber

Publications and source records attributed to R Silber.

At least 37 records · Page 2Linked to original sources

PubMed1991

[Taylorella equigenitalis: cell wall proteins, gene fingerprints, plasmids, adhesion and toxicity].

In this study 55 strains of Taylorella equigenitalis isolated from horses of four different studs in Austria, and a comparative strain from the Federal Republic of Germany were investigated by different methods. These investigations were carried out with the help of SDS-PAGE, immunoblotting, the analyses of genomes and by proof of plasmids. Furthermore, pathogenic mechanisms such as adhesion or the formation of toxins were investigated in vitro. On the basis of the results carried out by means of SDS-PAGE and immunoblotting all tested strains of Taylorella equigenitalis were alike, whereas by DNA analyses the strains could be divided into five groups. The comparative strain from the FRG, which clearly differed from the Austrian strains, formed one group all by itself. From three studs, which are related to each other because of an intensive exchange of horses, representatives (n = 53) of three DNA fingerprint groups were isolated. These three fingerprint patterns were very similar to each other, while the hybridisation patterns from the other two Austrian strains were very different. One of these strains, isolated from a diseased mare, could not be distinguished from the other strain isolated from a clinical healthy stallion from the same study by this method. Only 47.3% from the investigated strains showed attachment to HeLa cells, while cell extracts of all of them caused morphological changes of a varying degree of both Y1 and Vero cells. There were no connexions between these adhesion-cytotoxicity-properties and the DNA fingerprint groups as well as the studs, respectively. No plasmids were found in the Taylorella equigenitalis strains used in this study.

Animals↗

PubMed1990

Characterization of glutathione S-transferase expression in lymphocytes from chronic lymphocytic leukemia patients.

Chronic lymphocytic leukemia (CLL) is a disease state which frequently responds to alkylating agent chemotherapy but ultimately becomes refractory through acquired resistance mechanisms. In the present study, we have examined the expression of glutathione S-transferases (GST) in both CLL and normal control lymphocytes, as these enzymes have been implicated in mechanisms of natural and acquired resistance. Lymphocyte GST was purified from samples by high-pressure liquid affinity chromatography, and subunits were identified by two-dimensional gel electrophoresis and immunoblotting by using polyclonal antibodies specific for individual subunits. Analysis of CLL lymphocyte GST activity using the general substrate 1-chloro-2,4-dinitrobenzene showed a statistically significant 2-fold increase in cells from chlorambucil-resistant patients over those from untreated patients and normal individuals. Furthermore, chlorambucil therapy was seen to cause a 1.3- to 1.5-fold elevation of enzyme activity in three previously drug-naive patients. Analysis of GST isozyme subunits indicated that 95% of the CLL patients examined were positive for the pi isozyme, and this appeared quantitatively to be the major isozyme present. The alpha and mu isozymes were also expressed in 63 and 53% of the patients, respectively. Examination of control lymphocytes, as well as separated B- and T-cell subpopulations, yielded similar results. The present study indicates that a high degree of interindividual variation occurs and that the pattern of CLL lymphocyte GST expression differs from that of other tumor tissues. While there were no obvious correlations between the disease state or stage and isozymes expressed, the quantitative increase in GST activity in chlorambucil-resistant CLL patients may be of relevance to the overall resistant phenotype.

Aged↗

PubMed1990

Decreased L system amino acid transport and decreased gamma-glutamyl transpeptidase are independent processes in human chronic lymphocytic leukemia B-lymphocytes.

The L system of amino acid transport is markedly diminished in chronic lymphocytic leukemia (CLL) B-lymphocytes, with a maximal velocity less than 15% that of normal B-lymphocytes. Another membrane-associated function, the activity of the ectoenzyme, gamma-glutamyl transpeptidase (GGT), is diminished in CLL B-cells to 30% that of normal B-cells. In addition to its transpeptidase activity, a role for GGT has been postulated in the transport of amino acids. In the present report, the possible relationship of these two physiologic functions CLL B-cells was studied. The L system transport defect in CLL is restored by phorbol ester-induced cell maturation; following incubation with 0.15 microM tetradecanoyl phorbol acetate (TPA) for 17 hours, the L system initial velocity showed a 20-fold increase. In contrast, there was no significant effect on GGT activity with cell maturation. Furthermore, an antibody which diminished GGT activity by 50% in lymphoid cells did not inhibit L system transport. Thus, the impaired L system amino acid transport and GGT activity appear to be independent processes in CLL B-cells.

Amino Acids↗

PubMed1990

Evidence that the sheep associated form of malignant catarrhal fever is caused by a herpes virus.

Out of a cow, which was infected with the sheep form of malignant catarrhal fever (MCF), blood and spleen samples were inoculated into rabbits. From the spleen cells of an infected rabbit, which were cocultivated with bovine embryonic gingiva cells, a herpesvirus could be isolated. The isolate showed crossreactions with reference sera against the strain WC 11 (wildebeest form) in the SNT. An immunosuppressed heifer, which was infected with the isolate, contracted typical clinical symptoms of MCF. The isolate was named No. 732.

Animals↗

PubMed1990

[Surgical treatment and prognosis of lung metastases].

From 1979 through 1988, 215 patients with pulmonary metastases were treated in our department. Surgery was possible in 112 patients. Eighty-two patients were resected curatively, whereas 30 had only palliative surgery. The operation mortality was 1.8%. The essential prognostic factors were the complete removal of all pulmonary metastases, the portal or caval path of metastasis, involvement of the hilus lymph nodes and presence of clinical symptoms upon hospital admission. The 5-year-survival rate of patients undergoing potentially curative operations was 31%. This was significantly higher than in patients who underwent palliative operations (9%).

Follow-Up Studies↗

PubMed1990

[The detection of antibodies to the agent of malignant catarrhal fever in sheep and goat sera].

An epidemiologic study was undertaken by means of the SNT on three sets of sheep sera and one set of goat sera to evaluate for the occurrence of antibodies against strain WC11. Out of 791 sera of a sheep breeding organisation 57 samples (7.2%) showed positive titers. The positive samples originated from 24 farms (36.4%) out of 66 farms under test. Out of 118 sheep sera sent in from different parts of Austria 35 (29.7%) showed positive titers. 73 sheep sera out of a farm where MCF had clinically occurred were also tested. 20 samples (27.4%) scored positive. Also 40 goat sera (20.3%) out of 197 samples showed positive titers. The results are in accordance with publications from other countries. Special reference is made to goats as possible carriers and transmitters of MCF.

Animals↗

PubMed1990

[Peripheral round lesion of the lung: diagnosis, therapy, prognosis].

A total of 407 patients were hospitalized on account of a peripheral round lesion in the lungs (PR); 176 of these patients were inoperable for a wide range of different reasons. In 32.9% of the cases, a peripheral bronchial carcinoma presented, in 26.9%, the lesions were metastases, and in 2% malignant growths that were not further classified. All the remaining PR were benign. The following surgical procedures were performed: 39.8% lobectomies, 19.2% wedge resections, 20.6% enucleations, 6.4% segmental resections, 5.1% bilobectomies, 2.2% pneumonectomies, 6.7% various other procedures. The surgical mortality rate was 1.7% (0% in the case of the benign lesions); the re-thoracotomy rate for complications was 4.5%. The five-year survival probability for all bronchial carcinoma patients was 36%, and for all meta patients 47%. The poorest prognosis was seen in patients with PR when a small cell carcinoma or adenocarcinoma presented, and also in T3 tumours.

Carcinoma, Bronchogenic↗

PubMed1989

DNA topoisomerase I--targeted chemotherapy of human colon cancer in xenografts.

Drug development is needed to improve chemotherapy of patients with locally advanced or metastatic colon carcinoma, who otherwise have an unfavorable prognosis. DNA topoisomerase I, a nuclear enzyme important for solving topological problems arising during DNA replication and for other cellular functions, has been identified as a principal target of a plant alkaloid 20(S)-camptothecin. Significantly increased concentrations of this enzyme, compared to that in normal colonic mucosa, were found in advanced stages of human colon adenocarcinoma and in xenografts of colon cancer carried by immunodeficient mice. Several synthetic analogs of camptothecin, selected by tests with the purified enzyme and tissue-culture screens, were evaluated in the xenograft model. Unlike other anticancer drugs tested, 20(RS)-9-amino-camptothecin (9-AC) induced disease-free remissions. The overall drug toxicity was low and allowed for repeated courses of treatment.

Adenocarcinoma↗

PubMed1989

DNA topoisomerase II-mediated interaction of doxorubicin and daunorubicin congeners with DNA.

Three groups of doxorubicin and daunorubicin analogues, differing by their substituents on the chromophore and sugar moieties, were used in this study. The 3'-N-unsubstituted (Group 1), 3'-N-acyl (Group 2), and 3'-N-alkyl (Group 3) analogues were tested for: (a) in vivo antitumor activity and in vitro cytotoxicity; (b) cellular or tissue uptake and metabolic conversion; (c) strength of DNA intercalation; and (d) interaction with DNA topoisomerase II (topo-II). Compounds of Group 1 were cytotoxic, were strongly intercalative, and, except for those with C-14 side chain substitution, induced the formation of topo-II-DNA cleavable complexes. As shown previously, esterolysis of C-14-acyl substituents was required to yield a metabolite which can interact with topo-II in the purified system. The C-14-substituted compounds of Group 2 and their C-14-unsubstituted metabolites were cytotoxic. These drugs were weak intercalators, and the C-14-unsubstituted cogeners induced cleavable complex formation in the purified system, but with reduced potency relative to doxorubicin. The type of the 3'-N-position substituent determined whether Group 3 analogues were cytotoxic and strong intercalators, or less active and nonintercalating. Although C-14-unsubstituted intercalators of Group 3 did not form cleavable complexes in the purified system, they were cytotoxic. The study shows that DNA intercalation is required but not sufficient for the activity by topo-II-targeted anthracyclines. In addition to the planar chromophore which is involved in intercalation, two other domains of the anthracycline molecule are important for the interaction with topo-II: (a) substitution of the C-14 position totally inhibits drug activity in the purified system, but enhances cytotoxicity by aiding drug uptake and presumably acting on other cellular targets; and (b) substitutions on the 3'-N position of the sugar ring can, depending on the nature of the substituent, inhibit intercalation and/or topo-II-targeting activity. These findings may provide guidance for the synthesis and development of new active analogues.

Animals↗

PubMed1989

Lack of drug-induced DNA cross-links in chlorambucil-resistant Chinese hamster ovary cells.

Chlorambucil (CLB) is an alkylating agent commonly used in the treatment of several neoplastic disorders. The mechanisms underlying resistance to this drug are not fully defined. We used the DNA alkaline elution technique to study cross-link formation in the wild type (K1) and a CLB-resistant (ChlR) Chinese hamster ovary cell line. [14C]CLB was used to measure drug uptake. The CLB-resistant cells were found to have negligible DNA cross-link formation compared to K1 cells at all time points tested. There was a correlation between the resistance to CLB and the decreased ability of resistant cells to form DNA cross-links. Results of drug uptake experiments excluded altered CLB accumulation as the basis for these findings. Assays of O6-alkylguanine transferase and topoisomerase. II provide evidence against a role of these enzymes in CLB resistance. These studies suggest that the mechanism of CLB cytotoxicity involves the formation of DNA cross-links. Reduced cross-link formation may confer resistance to CLB.

Animals↗

PubMed1989

DNA topoisomerase I-mediated DNA cleavage and cytotoxicity of camptothecin analogues.

20(S)-Camptothecin, the 20(S)-camptothecin sodium salt, and 12 analogues with substituents on the A ring differ widely in their effectiveness in the treatment of murine L1210 lymphoblastic leukemia in vivo. The drugs were screened in the following systems: System 1, the cleavage of DNA in the presence of purified topoisomerase I; System 2, drug-induced trapping of topoisomerase I in a covalent complex with DNA; and System 3, the induction of protein-associated DNA breaks in drug-treated L1210 leukemia cells. 9-Amino-20(S), 10-amino-20(RS), and 10,11-methylenedioxy-20(RS), drugs effective against murine L1210 leukemia in vivo, stabilize topoisomerase I-DNA cleavable complexes in a purified system and in cultured L1210 cells. Other analogues, inactive against L1210 leukemia in vivo, were totally ineffective in topoisomerase I-directed screens. The rest of the analogues were intermediate in terms of their antitumor and topoisomerase I-directed activities. The study shows that the drug-induced accumulation of enzyme-DNA cleavable complexes is directly proportional to drug cytotoxicity and antitumor activity.

Animals↗

PubMed1989

Chlorambucil pharmacokinetics and DNA binding in chronic lymphocytic leukemia lymphocytes.

Chlorambucil (CLB) uptake by chronic lymphocytic leukemia lymphocytes was studied using a radiometric and a newly developed high-performance liquid chromatography assay. CLB labeled with 14C in either the chloroethyl group or phenyl ring was used with identical results. Drug accumulation by the cells was found to peak at 30 s, was independent of temperature, and was proportional to medium CLB concentration over a wide range. Efflux from cells loaded with CLB and resuspended in drug-free medium was nearly complete at 30 s. The metabolic inhibitors 2-deoxyglucose and NaN3, the nitrogen mustard transport inhibitor hemicholinium-3, and another alkylating agent, melphalan, had no effect on drug uptake. We conclude that CLB enters and exits chronic lymphocytic leukemia lymphocytes by simple diffusion. Cells from 17 patients with all stages of chronic lymphocytic leukemia were studied including three with CLB-resistant disease, and no heterogeneity was found in the peak cell-associated CLB content or in metabolite pattern on high-performance liquid chromatography. These findings make it unlikely that transport or cellular drug metabolism are factors in drug resistance. Drug-DNA binding was found to be temperature-sensitive and increased with time of incubation. Gel filtration of DNA before and after enzymatic digestion indicated the presence of drug-DNA adducts. High-performance liquid chromatography analysis of digested DNA and DNA treated by neutral thermal hydrolysis suggested the presence of multiple adducts. Most of the radioactivity was found as purine adducts. Studies with CLB labeled at two different sites revealed the presence of the phenyl group and ethyl chains in the adducts. A survey of patients showed increased drug-DNA binding in cells from patients with clinical CLB resistance.

Chlorambucil↗

PubMed1989

Studies on drug resistance in chronic lymphocytic leukemia.

Chronic lymphocytic leukemia is a neoplastic disease in which drug resistance invariably occurs. We have studied the uptake and interaction with molecular targets of two drugs, chlorambucil and adriamycin, in CLL lymphocytes and CHO cell lines. Resistance does not appear related to uptake for either drug. Exposure to CLB causes DNA cross-links in the sensitive but not in the resistant cell line. The GSH content of B-CLL lymphocytes is depleted after a 20-hr incubation. An inability to maintain its GSH content may contribute to this cell's vulnerability to CLB. The resistance of CLL lymphocytes to ADR may be related to the undetectable levels of its target enzyme DNA topoisomerase II. Future approaches may involve study of novel anthracyclines, DNA topoisomerase I inhibitors and the development of in vitro predictive tests.

Animals↗

PubMed1989

Antioxidant enzymes in lymphocytes from normal subjects and patients with chronic lymphocytic leukaemia: increased glutathione peroxidase activity in CLL B lymphocytes.

The activities of several enzymes that protect against oxidative injury were determined in blood lymphocytes from patients with B chronic lymphocytic leukaemia (CLL) and from normal subjects. Similar glutathione reductase (GR), catalase and glucose-6-phosphate dehydrogenase (G6PD) activities were found in normal and CLL lymphocytes. Higher glutathione peroxidase (GP) activity was found in CLL lymphocytes. This activity in CLL B lymphocytes was 2-fold higher than that of normal B lymphocytes, and 3-fold higher than that of T lymphocytes from either source. Several disease processes have been associated with decreased glutathione peroxidase activity. Our finding with CLL B lymphocytes is believed to be the first example of an increased GP activity in a disease. It may reflect either the expansion of a rare type of B cell population or be an expression of the malignant process.

B-Lymphocytes↗

PubMed1989

[A successful procedure in mitral valve rupture accompanied by rupture of the papillary muscle and the chordae tendinae following multiple injuries and blunt thoracic trauma].

In a considerable number of cases, blunt chest trauma also involves cardiac lesions including myocardial contusion or disruption pericardial effusion, or valve rupture. Definite cardiac trauma poses a challenge to everyone involved in intensive care, as early diagnosis and prompt treatment may be necessary to prevent a fatal outcome. We report a 32-year-old patient with fractures of the humerus, forearm, left clavicle and 2nd rib, and right ribs 4-6 after an 8 m fall. He was intubated in the emergency room because of arterial hypoxemia. Despite fluid administration the blood pressure deteriorated and the patient rapidly developed congestive heart failure that required huge doses of catecholamines. A systolic murmur was heard in the apex and left axilla. Conventional transthoracic echocardiography showed mitral valve prolapse and was suggestive of a flail mitral valve. Transesophageal echocardiography confirmed the diagnosis of mitral valve rupture, which proved to be grade IV by angiography. Because of continuous deterioration with low cardiac output and critical blood pressures and heart rates, surgery was carried out on the day of admission. Complete rupture of the anterolateral papillary muscle was found with laceration of the ventricular muscle, rupture of the secondary chordae tendineae, partial rupture of the valve base and partial dissection of the valve leaflets from the base. As expected from the echocardiography, there was no pericardial effusion. The destroyed valve was replaced by a Duromedics prosthesis. Operative stabilization of the subcapital humeral fracture followed 3 days later.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1988

The association of progressive, atrophying, chronic, granulomatous dermohypodermitis with Hodgkin's disease.

The case of a patient with an unusual skin disorder--progressive, atrophying, chronic, granulomatous dermohypodermitis (PACGD)--who developed Hodgkin's disease is reported. A review of the literature revealed only two other cases of PACGD, one of which affected a patient who also was found to have Hodgkin's disease. In an additional report, the diagnosis of Hodgkin's disease was made in a patient who may have had the same dermatologic disorder. The case is reported because the association of these two rare diseases is believed to be more than a chance event.

Adult↗

PubMed1988

The monocyte differentiation antigen, CD14, is anchored to the cell membrane by a phosphatidylinositol linkage.

CD14 is a myeloid differentiation Ag expressed primarily on peripheral blood monocytes and macrophages. Although its function is unknown, the CD14 gene maps to a region encoding several myeloid growth factors and receptors. Analysis of the CD14 protein sequence deduced from the cDNA shows that although the CD14 protein contains a characteristic leader peptide, it lacks a characteristic transmembrane region, suggesting that CD14 may be anchored to the membrane via glycosylphosphatidylinositol (PI). Treatment of monocytes as well as a CD14-expressing neuroglioma cell line with PI-phospholipase C removed CD14 from the cell surface. Furthermore, monocytes from a patient with paroxysmal nocturnal hemoglobinuria, a disease characterized by lack of expression of other PI-linked proteins, failed to express CD14. Interestingly, the CD14-expressing neuroglioma cell line, which had been transfected with a single CD14 cDNA, released a soluble form of CD14 into the supernatant. Soluble forms of CD14 have previously been observed in serum of normal individuals and in culture supernatants of CD14+ cells. Biosynthetic experiments reveal that this soluble form of CD14 (48 kDa), which is smaller than the form released from the membrane by PI-phospholipase C (53 kDa), does not contain ethanolamine, the first constitutent of the PI-anchoring system. These studies demonstrate that CD14 is a member of the family of PI-anchored proteins and suggest that soluble forms of CD14 represent molecules that completely lack the PI-anchoring system.

Amino Acid Sequence↗

PubMed1988

The major Fc receptor in blood has a phosphatidylinositol anchor and is deficient in paroxysmal nocturnal haemoglobinuria.

Fc receptors on phagocytic cells in the blood mediate binding and clearance of immune complexes, phagocytosis of antibody-opsonized microorganisms, and potently trigger effector functions, including superoxide anion production and antibody-dependent cellular cytotoxicity. The Fc receptor type III (Fc gamma R III, CD 16), present in 135,000 sites per cell 1 on neutrophils and accounting for most of FcR in blood, unexpectedly has a phosphatidylinositol glycan (PIG) membrane anchor. Deficiency of Fc gamma R III is observed in paroxysmal nocturnal haemoglobinuria (PNH), an acquired abnormality of haematopoietic cells affecting PIG tail biosynthesis or attachment, and is probably responsible for circulating immune complexes and susceptibility to bacterial infections associated with this disease. Although a growing number of eukaryotic cell-surface proteins with PIG-tails are being described, none has thus far been implicated in receptor-mediated endocytosis or in triggering of cell-mediated killing. Our findings on the Fc gamma R III raise the question of how a PIG-tailed protein important in immune complex clearance in vivo and in antibody-dependent killing mediates ligand internalization and cytotoxicity. Together with our results, previous functional studies on Fc gamma R III and Fc gamma R II suggest that these two receptors may cooperate and that the type of membrane anchor is an important mechanism whereby the functional capacity of surface receptors can be regulated.

Hemoglobinuria, Paroxysmal↗