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Biomedical subjects

M Blumenstein

Publications and source records attributed to M Blumenstein.

At least 55 records · Page 3Linked to original sources
PubMed1989

B cell lymphokines in human systemic lupus erythematosus.

B lymphocytes of patients with systemic lupus erythematosus were studied to determine if they were intrinsically hyperresponsive to lymphokine mediators. Peripheral blood B cells from 25 lupus patients and 16 normal individuals matched for age and sex were cultured with recombinant lymphokines. B cells both from patients and normal subjects did not show increased [3H]thymidine uptake when cultured with interleukins 1, 2, and 4. The addition of Staphylococcus aureus Cowan I as costimulant increased [3H]thymidine uptake by B cells of patients and normal subjects. In the absence of T cells these recombinant lymphokines did not increase in vitro IgG or IgM production by lupus or normal B cells. Other recombinant lymphokines, interleukin 3, interferon gamma, lymphotoxin, tumour necrosis factor, and colony stimulating factors for granulocytes and macrophages were tested on lymphocytes from smaller numbers of patients and controls. Most patients in this study had inactive disease and all data suggested that B cells from patients with inactive lupus were not hyperresponsive to the lymphokines tested. In addition, the use of lymphokine gene probes for interleukins 2, 3, and 4 did not show spontaneous expression of these genes in circulating lymphocytes.

Adult↗
PubMed1989

Activation of mononuclear cells by aqueous extracts from hollow-fibre haemodialysers.

Monocytes from patients treated by long-term haemodialysis with cellulosic membranes can show functional signs of activation depending on the dialyser module. To elucidate the mechanism of this phenomenon, aqueous extracts of various hollow-fibre dialysers were tested for their ability to induce in-vitro interleukin-1 generation in peripheral blood mononuclear cells from healthy donors. Extracts were prepared by passing 0.5 litres of sterile endotoxin-free water from the dialysate to the blood compartment of the dialyser. Different dialysers containing cellulosic membranes, i.e. cuprophan, and hemophan, were studied. Extracts were dried by lyophilisation and resuspended in cell culture medium before incubation with peripheral blood mononuclear cells for 18 hours at 37 degrees C in a 5% CO2 atmosphere. Interleukin-1 was assayed by biological or radioimmunological methods. Extracts from steam-autoclaved, dry-stored, or gamma-sterilised, wet-stored cuprophan and hemophan modules resulted in interleukin-1 activity that did not differ from negative controls. By contrast, extracts from cuprophan caused significant interleukin-1 production when prepared from ethylene oxide-sterilised, dry-stored dialysers. This monokine-inducing activity could not be neutralised by the addition of polymyxin B and was heat unstable, indicating that the cell-activating stimulus was not endotoxin. Extensive rinsing of the module with water before extract preparation totally mitigated the in-vitro production of interleukin-1. Our results suggest that the extract-induced activation of peripheral blood mononuclear cells found with some dialysers containing membranes of cellulosic origin cannot be exclusively related to the membrane polymer, but depends on a number of other parameters such as sterilisation and storage mode of a given membrane.

Adjuvants, Immunologic↗
PubMed1989

[Biocompatibility in long-term hemodialysis: facts--theories--clinical significance].

Biocompatible hemodialysis membranes do not cause major untoward effects due to blood-interface reactions. In principle, however, every component of the extracorporeal circuit may have detrimental effects. Biocompatibility parameters include for example complement components, leukocyte drop, elastase release and interleukin-1 generation. Furthermore, ethylene oxide sensitization, beta 2-microglobulin clearance and endotoxin contamination are of importance. The clinical relevance of biocompatibility in modern hemodialysis is critically discussed.

Biocompatible Materials↗
PubMed1988

Altered interleukin-1 production in patients undergoing hemodialysis.

The capacity of peripheral blood mononuclear cells (PBMC) to undergo spontaneous and induced interleukin-1 (IL-1) production was examined in 10 healthy controls and in 10 patients undergoing intermittent hemodialysis (HD) using cuprophane membranes. Extracellular and cytoplasmic IL-1 activity was assayed by biologic and radioimmunologic methods. Spontaneous extracellular IL-1 activity was low in the patient and the control groups. However, spontaneous cytoplasmic IL-1 activity was greatly increased in the patients. Both assays gave comparable results. In contrast, the IL-1 response to lipopolysaccharide was significantly decreased in PBMC from the patients compared to controls. From these results we conclude that PBMC from HD patients show functional signs of activation, but an impaired response to exogenous stimuli, such as endotoxin.

Adult↗
PubMed1985

IgA1 protease cleaves heavy chains independently in dimeric human IgA1.

Bacterial IgA1 proteases have substrate specificity for human IgA1 immunoglobulin, and cleave both the heavy (alpha) chains where they are paired by disulfide bonds in the hinge region. To determine if the close apposition of the alpha chains allows a single enzyme-substrate-binding event to cleave both hinge region peptides we quantitated the relative levels of intermediate products during the course of complete hydrolysis of an IgA1 paraprotein. The substrate had four Fab regions, analogous to a secretory IgA dimer. The experimental data were then compared to computer-generated models in which various levels of cooperativity among Fab regions were tested. The results most closely conformed to a model in which each individual alpha chain is proteolyzed independently, without regard to the total number of hinge region peptides available in the substrate IgA1. These results will be used to guide the design of IgA1 hinge region peptide analogues as IgA1 protease inhibitors.

Autoradiography↗
PubMed1985

Current status of membrane plasma separation and plasma filtration techniques.

Blood and plasma processing by membranes was introduced into clinical medicine in 1979. In the meantime, membrane plasma separation (plasmapheresis) has become very satisfactory and is now a routine therapeutic procedure in many apheresis centers. Plasma fractionation by membranes (plasma filtration or cascade filtration) for unselective removal of high molecular weight pathogens from the separated plasma is technically possible but its routine clinical application is still limited to a few diseases with at least IgM-sized target proteins. The separation of IgG from albumin needed to treat many autoimmune diseases requires further development of both the membranes and the filtration technology.

Filtration↗
PubMed1984

Carbon-13 chemical shifts on oxytocin as a consequence of its interaction with neurophysins.

Carbon-13 NMR was used to study the interaction of the hormone oxytocin with neurophysin (NP). Oxytocins specifically enriched to 90% 13C in the alpha-carbons of Leu-3 (in [3-leucine]oxytocin), Gln-4, and Leu-8 and in the carbonyl carbon of Cys-6 were synthesized, so that the effect on these positions of binding to NP could be monitored. The alpha-carbons of residues 3 and 4 experienced shifts of -4.2 and -1.5 ppm (negative shifts are downfield), respectively, upon binding of the hormone to NP. The carbonyl carbon of residue 6 underwent a shift of +0.7 ppm, while the alpha-carbon of residue 8 displayed no shift. For each enriched residue, the hormone diastereoisomer in which this residue had the D configuration was also synthesized. NMR was then used to determine the binding affinity of the various diastereoisomers to NP, as well as to measure the NMR parameters of the bound peptides. When position 3 had the D configuration, the binding affinity for NP was 10-20% that of the native hormone. For positions 4, 6, and 8, the D diastereoisomers bound with the same affinity as oxytocin. The alpha-carbons of D residues of positions 3 and 4 shifted by -2.5 and +0.4 ppm, respectively, the carbonyl carbon of D-Cys-6 shifted by +1.4 ppm, and the alpha-carbon of D-Leu-8 was unshifted on binding to NP. The shift and diastereoisomer binding data, combined with previous results involving enriched carbons and/or diastereoisomers of residues 1, 2, and 9, support the conclusion that residues 1 and 2 are most crucial for binding of oxytocin to NP, residue 3 is less important, and residues 4-9 are of only slight significance.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Membrane plasma exchange: principles and application techniques.

Membrane plasmapheresis was introduced in 1978 as a new method for performing therapeutic plasma exchange. Its principal advantages over traditional techniques include speed, ease of performance, and ready adaptability to clinical centers already performing routine extracorporeal therapy. The appearance of a membrane plasmapheresis circuit (vascular access, anticoagulation, connectology) is similar to that of hemodialysis and especially hemofiltration; the operating protocols (treatment time, filtration rates, pressures, pharmacokinetics) are quite different. Particular attention must be paid to avoiding operating conditions that lead to hemolysis. In clinical use membrane plasma separation is as effective as centrifugal plasma exchange in removing plasma proteins. The sieving coefficients for proteins with a molecular weight (MW) ranging from 67,000 (albumin) to 2,400,000 (beta-lipoprotein) daltons are unity. An exchange of one patient plasma volume has been shown to cause a 55% reduction of the serum levels of intravascular proteins. There are no significant differences between membrane and centrifugal plasmapheresis in substitution fluid requirements (human albumin or fresh frozen plasma), indications for treatment and complications. The next major advance in plasmapheresis technology will almost certainly be development of a "closed loop" circuit in which filtered plasma is treated to remove the offending moiety and returned to the patient. This would eliminate both the cost and the possible side effects of replacement fluid. Membrane-based systems are already available for removing cryoglobulins or proteins with MW of at least 900,000 daltons.

Anticoagulants↗
PubMed1983

Plasma exchange in systemic lupus erythematosus.

Of 20 patients who presented to our hospital with the histologically confirmed diagnosis of SLE, nine met the criteria of presence of both a rapidly progressive disease state and contraindications for conventional therapy required for admission to our plasma exchange programme. Five patients improved; two patients progressed to end-stage renal failure; two patients died as a result of complications of advanced SLE. Severe lupus erythematosus (SLE) is usually treated with a combination of steroids and cytotoxic drugs. Even when treated with high dose therapy some patients develop life-threatening complications, such as renal failure, heart failure and respiratory insufficiency. Moreover, both treatment with high dose of corticosteroids and long lasting cytotoxic therapy may produce troublesome side-effects, including severe infections, gastroduodenal ulcers, bone marrow depressions and lymphomas (1, 2). One of the manifestation of SLE is the presence of antibodies against ds-DNA and ss-DNA. These antibodies can either react with DNA bound to te basement membrane and induce an inflammatory reaction (3), or can form circulating immune complexes which deposit in tissues and may impair the function of lymphocytes or macrophages in the RES (4, 5). The presence of anti-DNA-antibodies appears to be secondary to enhanced B-cell activity along with a depression of suppressor T-cells function proteins mediating the inflammatory process, such as fibrinogen, may deposit in membranes already compromised by the disease. Even though the pathogenic mechanisms operating in SLE are not completely understood, it can be expected, from a theoretical point of view, that the extracorporeal removal of any immunopathogens could improve the disease state.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗