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Biomedical subjects

M D Kramer

Publications and source records attributed to M D Kramer.

At least 163 records · Page 9Linked to original sources
PubMed1986

A fast-acting cytotoxin derived from Con A-activated porcine leukocytes. II. Mechanism of target cell lysis.

Serum-free culture supernatants of Con A-stimulated pig leukocytes contain cytotoxins (PCT) which have a fast-acting lytic effect on a variety of murine lymphomas. Mathematical analysis revealed that the cytodestructive reaction which leads to the immediate release of 51Cr from labeled target cells follows "single hit"/"first order" kinetics. The release of labeled compounds was found to be size dependent, such that low molecular isotope (86Rb) was released at faster rates than high molecular 51Cr-labeled complexes. The 51Cr release was strongly reduced by lowering the temperature to 4 degrees C. PCT-mediated target cell lysis could be competed by cold target cells and the factor could be absorbed by intact cells, plasma membranes and artificial liposomes. Neither the presence of EDTA or of various monosaccharides, nor exposure of target cells to trypsin, metabolic inhibitors, and cytoskeletal antagonists altered the target cells susceptibility to PCT-mediated lysis. Labeling of target cell DNA and subsequent exposure of these target cells to PCT revealed that target cell DNA is degraded into low-molecular-weight split products which is similar to that seen during T-cell mediated target cell lysis. The analysis of the lytic event mediated by PCT thus revealed similarities to T-cell mediated target cell lysis. PCT was clearly distinct from the well-known cytolytic agents lymphotoxin (LT), tumor necrosis factor (TNF), or complement (C'). Taken together, the described characteristics make PCT a unique-acting cytolytic cytokine with anticancer activity and suggest further research concerning its mode of action and its possible therapeutic application.

Animals↗
PubMed1985

Sequential degradation of heparan sulfate in the subendothelial extracellular matrix by highly metastatic lymphoma cells.

A highly metastatic variant (ESb) of a methylcholanthrene-induced T lymphoma elaborates a heparan sulfate (HS) degrading endoglycosidase (heparanase) to a much higher extent than its non-metastatic parental subline (Eb). Whereas a serum-free medium conditioned by either subline contained a trypsin-like serine protease, heparanase activity was detected only in the ESb-conditioned medium (CM). ESb CM was incubated with a naturally produced, sulfate-labelled subendothelial extracellular matrix (ECM) or with a soluble, high-MW labelled proteoglycan first released from the ECM by incubation with Eb CM or with the partially purified ESb protease. Sulfate labelled degradation products were analyzed by gel filtration on Sephrose 6B. The optimal pH for degradation of ECM-bound HS was 6.2 as compared to pH 5.2 for degradation of the soluble proteoglycan. Heparanase-mediated degradation of both ECM-bound and soluble HS was inhibited by heparin. Addition of either trypsin, plasmin or to a lower extent, the purified ESb protease, stimulated between 5- and 20-fold the ESb CM-mediated degradation of ECM-bound HS but had no effect on heparanase-mediated degradation of the soluble proteoglycan. This stimulation was inhibited in the presence of heparin or protease inhibitors. These results indicate that both a protease and heparanase are involved in the ESb-mediated degradation of ECM-bound HS and that one enzyme produces a more accessible substrate for the next enzyme. This sequential cleavage is characteristic of degradation of a multimolecular structure such as the subendothelial ECM and hence cannot be detected in studies with its isolated constituents.

Animals↗
PubMed1985

Characterization of an extracellular matrix-degrading protease derived from a highly metastatic tumor cell line.

A proteolytic activity associated with the microsomal fraction of L-5178Y/Esb tumor cells has been characterized. The enzyme has a molecular weight of 80-90 kD as determined by affinity-labelling with [3H]DFP and SDS-gel electrophoresis. It cleaves ester substrates at the carboxyl position of lysine and arginine and can activate the proenzyme plasminogen. The enzyme is found to be associated with the plasma membranes of high and low metastatic tumor cell lines and is shed in high-molecular-weight form mainly by the high metastatic variant. The pH optimum for esterase and protease activities was 7.5-8.5. Although similar to trypsin in substrate specificity, the enzyme was not inhibited by lima-bean trypsin inhibitor but was inhibited by DFP, PMSF, aprotinin and leupeptin. Partially purified preparations of the protease can alone degrade 125I-labelled endothelial cell extracellular matrix, pointing at the putative role of this enzyme in tumor invasion.

Animals↗
PubMed1985

Biotechnological production and functional characterization of leukocytic cytokine(s) with cytotoxic effect on resting but not activated thymocytes.

In the present report we describe the analysis of suppressive and cytotoxic factor(s) derived from Con A-induced porcine leukocyte culture supernatant solution(s) (PCAS). The supernatant solution(s) had been produced on a biotechnological scale using porcine peripheral blood leukocytes isolated from 200 to 1000 1 of porcine blood. The supernatant solution(s) were tested for their effect during murine T cell activation. We found that crude supernatant solution(s) contain suppressive and cytotoxic factor(s) (SF) which have a similar selectivity for non-activated thymocytes as suppressive factor(s) previously detected in the supernatant solution(s) of allo-antigen-stimulated murine spleen cell cultures. SF was obtained from crude serum-free culture supernatants by fractionated ammonium-sulphate precipitation between 35 and 45% saturation. SF has the following characteristics: its release into the culture supernatant is dependent on mitogenic stimulation, it acts during early stages of T lymphocytic activation, the activity towards naive thymocytes is most likely caused by an irreversible cytolytic mechanism, and phenotypically and functionally immature thymocytes are preferentially affected through exposure to SF.

Animals↗
PubMed1985

Efficacy of percutaneous transluminal coronary angioplasty compared with single-vessel bypass.

The use of percutaneous transluminal coronary angioplasty has been increasing rapidly. When the procedure is successful, the clinical relief of symptoms is similar to that achieved with direct coronary artery bypass. It has been suggested that the angioplasty procedure, however, can accomplish these results with potentially less morbidity and mortality, along with a shorter hospital stay. In order to evaluate the results of percutaneous transluminal coronary angioplasty with single-vessel coronary artery bypass, we performed a retrospective review. From January, 1982, to December, 1983, a total of 198 angioplasty procedures were performed. They were successful in 142 patients (71.7%). Emergency bypass was performed in 21 (10.6%) of the 56 patients who had undergone unsuccessful angioplasty procedures. Perioperative myocardial infarction occurred in eight of these patients (38.1%). There were no operative deaths, but there was one death after angioplasty. Elective bypass was performed in 28 of the patients who had angioplasty procedures, with no perioperative myocardial infarctions or operative deaths. Recurrent symptoms developed in 31 (21.8%) of the 142 patients who had undergone initially successful angioplasty. From 1982 to 1983, single-vessel bypass was performed in 143 patients. The internal mammary artery was utilized in 102 patients and the autogenous saphenous vein in 41 patients. There were no perioperative myocardial infarctions or deaths. No patients developed recurrent symptoms during the study interval. Percutaneous transluminal coronary angioplasty is an acceptable alternative to coronary artery bypass in patients with localized lesions that are sufficiently serious to cause symptoms and warrant surgical bypass. However, the angioplasty procedure, when compared to single-vessel coronary artery bypass, may result in an increased incidence of acute myocardial infarction and in a significantly (p less than 0.001) increased incidence of early recurrence of symptoms.

Adult↗
PubMedDate not supplied

The outer surface protein A (OspA) of Borrelia burgdorferi: a vaccine candidate and bioactive mediator.

In the search for a suitable vaccine candidate for Lyme borreliosis the principles of protective immunity were studied in a murine model of Borrelia burgdorferi infection. It was found that the spirochetal outer surface protein A (lipOspA) in its native and recombinant lipidated form induces monospecific immune sera, which in passive transfer experiments protect SCID mice against experimental and tick-borne infection and disease. These and similar findings of independent groups led to the development of a vaccine formulation containing lipOspA. When tested in clinical phase I/II safety trials the recombinant lipOspA vaccine was shown to be safe, immunogenic and able to elicit borreliacidal antibodies. At present, clinical phase III efficacy trials are being conducted. B. burgdorferi infection involves the dissemination of the spirochetes from the site of the tick bite, infection of distant organs, and induction of a chronic inflammatory process. Recent studies indicate that the spirochetes may utilize host-derived enzyme systems to increase their virulence/pathogenicity. It was found that lipOspA serves as a surface receptor for the host-derived proteolytic enzyme plasmin(ogen), the central component of the so-called plasminogen activator system. Moreover, it was found that spirochetes are able to activate endothelial cells and blood-derived leukocytes, such as monocytes/macrophages, B cells and T cells, to express functions and/or secrete molecules, which are known to promote inflammatory responses. Part of these activities were exerted by the isolated lipOspA. The studies indicate an important role of lipOspA, both for the induction of a protective immune response by the host, as well as for the pathogenic processes elicited during B. burgdorferi infection.

Adult↗
PubMedDate not supplied

Tick factors and in vitro cultivation influence the protein profile, antigenicity and pathogenicity of a cloned Borrelia garinii isolate from Ixodes ricinus hemolymph.

A Borrelia garinii isolate (NE11H) was obtained from the hemolymph of infed Ixodes ricinus. NE11H expressed four major proteins of 33 kDa, 32 kDa, 23 kDa and 22 kDa. During in vitro culture, NE11H successively lost the expression of the 22 kDa and 23 kDa proteins and the NE11H variant (NE11Hp15) was not recognized by an immune serum specific for the OspC protein (anti-OspC IS). However, when reintroduced into tick midguts, NE11Hp15 spirochetes present in the midgut again reacted with anti-OspC IS. A clone derived from the wild type line, cNE11H, lacked the 22 kDa but not the 23 kDa protein. The 23 kDa protein of cNE11H was recognized by anti-OspC IS. In addition, the two descendant lines (NE11Hp15 and cNE11H) lost their capacity to induce clinical arthritis in SCID mice. When cNE11H was reintroduced into ticks and reisolated from various tick organs, most reisolates presented the same reaction with anti-OspC IS as cNE11H. Interestingly, two reisolates obtained from the tick midgut reexpressed large amounts of the 22 kDa protein which was recognized by anti-OspC IS and these two reisolates induced clinical arthritis in SCID mice. The results confirm that proteins of 22/23 kDa are differentially expressed during in vitro subcultures and in ticks, and show that proteins which are not detectable after in vitro culture may be reexpressed after reexposure of B. burgdorferi to its former environment in the tick. The data suggest that the pathogenicity of B. burgdorferi for mice might be influenced by environmental factors via differential expression of 22/23 kDa proteins.

Animals↗
PubMedDate not supplied

Internal mammary artery bypass: thirteen years of experience. Influence of angina and survival in 5125 patients.

Internal mammary artery (IMA) bypass to the anterior descending coronary artery (ADA) was performed in 5125 patients from January 1978 to December 1990. The average age of patients was 68 years; males accounted for 68% (3485 patients) and 82% (4203) were NYHA Class III. Left ventricular function was impaired (ejection fraction < 40%) in 68% (3485 patients). The average number of additional saphenous vein graft (SVG) per patient was 2.2. Operative mortality was 1.8%. Mediastinitis occurred in 51 patients (1.0%). Reoperation for bleeding was necessary in 56 patients (1.1%). Perioperative myocardial infarction was seen in 102 patients (2.0%) and neurological complications occurred in 51 patients (1%). Repeat coronary angiography was performed in 1414 patients (28%) and demonstrated a patency rate of 96% in IMA grafts and 75% in SVG grafts (p < 0.001). Survival at 13 years was 80% from all causes and 90% when non-cardiac deaths were excluded. Recurrence of angina occurred in 768 patients (15%) and reoperation or PTCA was performed in 61 (1.2%). During the same time period, 2345 patients underwent coronary artery bypass utilizing solely SVG. Survival at 13 years was 68% from all causes and 78% when non-cardiac deaths were excluded (p < 0.001). Recurrent angina was present in 727 patients (31%) (< 0.001). This data suggests that long-term probability of cumulative survival and occlusion free survival were significantly greater and the probability of recurrent angina and reoperative CABG and death from cardiac causes were significantly less in the IMA patients and should be the conduit of choice in coronary bypass surgery.

Adult↗
PubMedDate not supplied

[Morphology of synovial cells of the human in organ and explant cultures].

Biopsy material of synovial tissue was taken from 36 patients (with arthrosis, rheumatoid arthritis, traumatic and unaffected joints). Cell and tissue cultures, as well as cells dissociated by enzymes, were investigated by light microscopy (LM), immunohistochemistry, and electron microscopy. Synovial A-cells were endowed with all morphological characteristics of phagocytic capacity but lacking the peroxidase reaction. In contrast to the monocytes, they were not immunostained by OKM-1 antibodies. The A-cells could be observed in subsequent in vitro growth for up to 2 weeks. In addition to B-cells, a third cell type was identified. This cell type had the morphological characteristics of a dendritic cell and was glass and plastic adherent. It can be referred to also as a stellate cell. We assume that these stellate cells represent modified synovial fibroblasts.

Arthritis, Rheumatoid↗