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Biomedical subjects

H S Jacob

Publications and source records attributed to H S Jacob.

At least 73 records · Page 4Linked to original sources
PubMed1986

Magnesium sulfate: rationale for its use in preeclampsia.

Preeclampsia is a disorder of pregnancy characterized clinically by hypertension, proteinuria, and edema and characterized pathologically in its late stages by widespread microvascular thrombi. There is evidence from a number of studies that production of prostacyclin (prostaglandin I2, PGI2), a potent vasodilator and inhibitor of platelet aggregation, is deficient in preeclamptic compared to normal pregnancy. Traditional therapy utilizes infusions of large amounts of MgSO4, but the physiologic basis for this is not clear. We studied the effect of MgSO4 on PGI2 release by cultured human umbilical vein endothelial cells (HUVEC) by several methods. By platelet aggregometry, the known antiaggregatory effect of intact HUVEC was enhanced by MgSO4. By radioimmunoassay for 6-keto-PGF1 alpha, the stable metabolite of PGI2, it was shown that MgSO4 amplifies release of PGI2 by HUVEC in a dose-dependent manner, with a peak occurring between 2 and 3 mM. In separate experiments, MgSO4 overcame the enhanced adherence of platelets to HUVEC exhausted by repeated exposure to thrombin. Finally, PGI2 production was 2- to 5-fold greater by HUVEC incubated with plasma obtained from preeclamptic patients undergoing MgSO4 therapy than by HUVEC incubated with pretherapy plasma. We conclude that MgSO4 mediates enhanced production of PGI2 by vascular endothelium, thereby potentially enhancing its thromboresistant properties.

Cells, Cultured↗
PubMed1986

G6PD-deficiency infectious haemolysis: a complement dependent innocent bystander phenomenon.

Dramatic haemolysis may accompany viral hepatitis and pneumococcal pneumonia in G6PD-deficient patients. Since red blood cells (RBCs) are richly endowed with receptors for activated complement, particularly C3b, we hypothesized that bulky, complement-activating immune complexes (IC) consisting of microbes and antibody might attract granulocytes (PMNs), facilitating oxidative 'innocent bystander' RBC damage. Indeed, opsonization with only two type-2 pneumococcus (PN3)/anti-PN3/C3b complexes per RBC caused agglutination of RBC, a phenomenon termed immune adherence. Addition of as few as one PMN per 20 opsonized RBCs caused the glutathione (GSH) levels of co-incubated G6PD-deficient RBCs to fall by 30% (from 3.5 to 1.8 +/- 0.8 mumoles GSH/g Hb) compared to identically incubated, but nonopsonized, G6PD-deficient RBCs. GSH levels remained normal (5.2 +/- 0.4 mumoles/g Hb) in PMN-exposed opsonized normal RBCs. GSH depletion in G6PD-deficient RBC was directly related to disease severity--falling a mean 33% in RBCs from two Black G6PD A- subjects but 59% in two Caucasian G6PD deficient RBCs. Prevention of C3b generation (with 10 mM EDTA) during opsonization abrogated both immune adherence and PMN-mediated GSH decline in oxidant-sensitive cells. Similarly, removal of C3b receptors by brief trypsin incubation of RBCs eliminated immune adherence and GSH decline. Thus, both phenomena are dependent on IC complement activation and subsequent binding of the bacterial IC to the RBC complement receptors. Although clearance of IC by RBCs may be beneficial in protecting other tissues from inflammatory damage, G6PD-deficient RBCs are vulnerable to oxidants generated by juxtaposed phagocytes--cells attracted to, and stimulated by, the immune complex/C3b combination. It is suggested that this 'Good Samaritan' activity of RBCs may lead to haemolysis during periods of exuberant antibody response to microbes.

Anemia, Hemolytic↗
PubMed1986

Platelets augment granulocyte aggregation and cytotoxicity: uncovering of their effects by improved cell separation techniques using Percoll gradients.

The 'standard' technique of granulocyte preparation for in vitro studies uses dextran removal of erythrocytes and Ficoll-Hypaque gradient centrifugation to increase granulocyte purity. The procedure is lengthy, approximately 150 min in our hands, and provides granulocytes significantly contaminated with platelets (approx. 5 platelets/PMN). We report a technique that replaces dextran with hydroxy-ethylstarch and Ficoll-Hypaque with Percoll. Preparation time is reduced by approximately 40% and platelet contamination by more than 80%. Granulocytes, so prepared, function metabolically (O2-generation, chemiluminescence, HMP-shunt maxima) and, in motility/phagocytosis assays, identically to 'standard' preparations. However, an augmentatory effect of platelets in granulocyte aggregation responses and their mediation of cytotoxicity is uncovered. Ficoll-Hypaque purified cells (platelet-rich) aggregate to a significantly greater degree with FMLP or activated complement lectins and excessively kill 51Cr-labelled target cells when compared to Percoll-preparations (platelet-poor). Re-addition of purified platelets or of platelet release supernatants to the latter reproduces results using the 'standard' preparations.

Blood Platelets↗
PubMed1985

Protection against lethal hyperoxia by tracheal insufflation of erythrocytes: role of red cell glutathione.

Intact erythrocytes placed into the tracheobronchial tree of hyperoxic rats dramatically improved their chances for survival. Over 70 percent of the animals so treated survived more than 12 days during continuous exposure to 95 percent oxygen, whereas all of the control animals died within 96 hours. Lungs from erythrocyte-protected rats showed almost none of the morphologic damage suffered by untreated animals. Erythrocytes containing cyanomethemoglobin were as beneficial as normal erythrocytes, but cells in which glutathione was partially blocked were significantly less protective. Analogous results were obtained in vitro: 51Cr-labeled target cells released 70 to 90 percent of their label when exposed briefly to hydrogen peroxide or to toxic oxygen species generated by phorbol ester-stimulated neutrophils. Addition of intact erythrocytes decreased release by approximately 75 percent, but significantly less than this if red blood cell glutathione was partially blocked. These results suggest that insufflated erythrocytes, through their recyclable glutathione, protect rats from toxic oxygen species engendered by hyperoxia.

Animals↗
PubMed1985

Oxygen radical-induced erythrocyte hemolysis by neutrophils. Critical role of iron and lactoferrin.

Human neutrophils (PMN), when stimulated with such chemotaxins as phorbol myristate acetate (PMA), destroy erythrocytes and other targets. Cytotoxicity depends on PMN-generated reactive oxygen metabolites, yet the exact toxic specie and its mode of production is a matter of some dispute. Using 51Cr-labeled erythrocytes as targets, we compared various reactive-O2 generating systems for their abilities to lyse erythrocytes as well as to oxidize hemoglobin to methemoglobin. PMA-activated PMNs or xanthine oxidase plus acetaldehyde were added to target erythrocytes in amounts that provided similar levels of superoxide. PMNs lysed 68.3 +/- 2.9% (SEM) of targets, whereas the xanthine oxidase system was virtually impotent (2.3 +/- 0.8%). In contrast, methemoglobin formation by xanthine oxidase plus acetaldehyde was significantly greater than that caused by stimulated PMNs (P less than 0.001). A similar dichotomy was noted with added reagent H2O2 or the H2O2-generating system, glucose plus glucose oxidase; neither of these caused 51Cr release, but induced 10-70% methemoglobin formation. Thus, although O2- and H2O2 can cross the erythrocyte membrane and rapidly oxidize hemoglobin, they do so evidently without damaging the cell membrane. That a granule constituent of PMNs is required to promote target cell lysis was suggested by the fact that agranular PMN cytoplasts (neutroplasts), although added to generate equal amounts of O2- as intact PMNs, were significantly less lytic to target erythrocytes (P less than 0.01). Iron was shown to be directly involved in lytic efficiency by supplementation studies with 2 microM iron citrate; such supplementation increased PMN cytotoxicity by approximately 30%, but had much less effect on erythrocyte lysis by neutroplasts (approximately 3% increase), and no effect on lysis in the enzymatic oxygen radical-generating systems. These results suggest a critical role for an iron-liganding moiety that is abundantly present in PMN, marginally so in neutroplasts, and not at all in purified enzymatic systems--a moiety that we presume catalyzes very toxic O2 specie generation in the vicinity of juxtaposed erythrocyte targets. The obvious candidate is lactoferrin (LF), and indeed, antilactoferrin IgG, but not nonspecific IgG, reduced PMN cytotoxicity by greater than 85%. Re-adding 10(-8) M pure LF to neutroplasts increased their ability to promote hemolysis by 48.4 +/- 0.9%--to a level near that of intact PMNs. We conclude that O-2 and H2O2 are not sufficient to mediate target cell lysis, but require iron bound to LF, which, in turn, probably generates and focuses toxic O2 radicals, such as OH, to target membrane sites.

Cytoplasmic Granules↗
PubMed1985

Human platelets exert cytotoxic effects on tumor cells.

Monocytes are thought to play a role in host resistance to tumor cell growth in animals and humans. In addition, platelets are known to be involved in tumor metastases. To investigate the interaction of these two cell types and their effect on tumor cells, human monocytes and platelets were examined using an in vitro monocyte-tumor cell cytotoxicity assay. Monocytes alone resulted in 32% +/- 1.5 (mean +/- SEM) tumor cell kill. When platelets were added to monocytes in a 1:1 ratio, an increase in cytotoxicity to 61% +/- 3.2 was observed. The cytotoxicity noted when platelets were added to a fixed number of monocytes and tumor cells was dependent on the number of platelets added. A decrease in cytotoxicity from 32% +/- 1.5 to 12% +/- 2.3 was observed when contaminating platelets were removed from monocyte preparations. Platelets added to tumor cells in the absence of any monocytes were also toxic, resulting in a maximum kill of 95% at a 4:1 platelet/tumor cell ratio. Secreted products of freshly isolated platelets may be responsible for much of the observed cytotoxicity, since supernatants from the platelets were toxic for tumor cells. Platelets pretreated with a cyclooxygenase inhibitor (ASA) or a lipoxygenase inhibitor had decreased cytotoxicity compared with untreated platelets. Our results indicate that products of platelet arachidonate metabolism are toxic for tumor cell lines. They also suggest that the role of the platelet must be considered when studying monocyte-tumor cell cytotoxicity.

Blood Platelets↗
PubMed1985

Extracellular matrix proteins (fibronectin, laminin, and type IV collagen) bind and aggregate bacteria.

The normal microbial colonization of sites in the body's tissues by certain bacteria requires that the bacteria first bind to extracellular secreted constituents, cell-surface membranes, or cell matrixes. This study examines two interactions of a variety of bacteria with the cell matrix noncollagenous proteins fibronectin and laminin and with basement membrane (Type IV) collagen. Adherence of bacteria to matrix proteins coated on tissue culture wells was examined with the use of radiolabeled bacteria. Staphylococcus aureus, Streptococcus pyogenes, and Streptococcus sanguis bound well to fibronectin, laminin, and Type IV collagen, whereas a variety of gram-negative organisms did not bind. The interaction of soluble laminin, fibronectin, and Type IV collagen with bacteria was monitored by nephelometry with the use of a platelet aggregometer. S. aureus aggregated in response to fibronectin, laminin, or Type IV collagen. In contrast, gram-negative organisms did not aggregate with these proteins. It appears that fibronectin, laminin, and Type IV collagen can bind and aggregate certain gram-positive bacteria, and this binding is dependent on the surface characteristics of the organism. These adhesion molecules may play a role in the normal colonization of sites by microorganisms and in invasion during infections.

Adhesiveness↗
PubMed1985

Sp alpha I/65: a new variant of the alpha subunit of spectrin in hereditary elliptocytosis.

Two molecular defects involving the spectrin heterodimer (SpD) contact site of the alpha chain (the alpha I domain) were previously identified using limited tryptic digestion followed by two-dimensional isoelectric focusing/sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Both are characterized by atypical peptide maps which reveal a marked decrease of the 80,000-dalton alpha I domain and a formation of new major peptides of either 74,000 (Sp alpha I/74) or 46,000 (Sp alpha I/46) daltons. We now report a third variant of the spectrin alpha chain, designated Sp alpha I/65, in three unrelated black families. In all three probands, the percentage of SpD in the low ionic strength (O degrees C) membrane extracts was increased to 19% to 32%. One- and two-dimensional electrophoretic separations of limited tryptic digests of spectrin from all three probands revealed a decrease of the alpha I domain of spectrin and the concomitant appearance of peptides at 65,000 daltons and isoelectric points ranging from 5.2 to 5.3. The abnormal 65,000-dalton peptides could be stained with an antiserum which had been raised against the alpha I domain, indicating that it was derived from the alpha I domain.

Adult↗
PubMed1985

Sodium morrhuate stimulates granulocytes and damages erythrocytes and endothelial cells: probable mechanism of an adverse reaction during sclerotherapy.

Stimulated by a patient with dyspnea, thrombocytopenia, and leukopenia after sodium morrhuate sclerotherapy, we studied the effect of this agent on the plasma coagulation and complement systems, the formed elements of the blood, and cultured human endothelial cells. The addition of sodium morrhuate to citrated plasma did not cause clotting or shorten the prothrombin time or partial thromboplastin time. Incubation of a 1:100 dilution of the clinical sodium morrhuate preparation in heparinized plasma led to a modest rise in [C3a]. The addition of the drug (dilutions 1:50 to 1:300) to granulocytes caused prompt aggregation (and, at the higher concentrations, granulocyte cytotoxicity [trypan blue exclusion; lactate dehydrogenase release]), but the same dilutions failed to aggregate platelets. However, 0.05% morrhuate added to washed red blood cells caused a prompt 84.0% (+/- 0.8% SEM) hemolysis, rendering the supernatant buffer a potent platelet aggregant. Not only was this sclerosing agent toxic to granulocytes and red cells, but a 1:1000 dilution of the drug also caused the destruction of 35.5% (+/- 6.6%) of cultured endothelial cells as measured by chromium 51 release. Three other agents in current use (ethanolamine oleate, sodium tetradecyl sulfate, and polidocanol) were studied and found to cause effects qualitatively similar to those of sodium morrhuate. We conclude that these drugs cause phlebosclerosis not primarily through induction of plasma coagulation, but by directly damaging endothelium and red cells, triggering platelets, and aggregating granulocytes at the venous wall endothelium. These effects likely derive from the surfactant properties of sodium morrhuate as well as its high arachidonate content.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Coagulation↗
PubMed1984

A dermatitis-eosinophilia syndrome. Treatment with methylprednisolone pulse therapy.

A 47-year-old man had a generalized, eczematous erythroderma and eosinophilia one week after a wasp sting. These changes persisted for four months despite intensive topical therapy and oral corticosteroids. He was then given corticosteroid pulse therapy with methylprednisolone sodium succinate (2 g, intravenously). One week later, a second pulse treatment was administered. This therapy was followed by permanent resolution of the dermatitis within two weeks.

Adrenocorticotropic Hormone↗
PubMed1984

Ibuprofen inhibits granulocyte responses to inflammatory mediators. A proposed mechanism for reduction of experimental myocardial infarct size.

The use of nonsteroidal antiinflammatory agents to reduce myocardial infarct size has demonstrated a dichotomy between ibuprofen, which reduces myocardial infarct size, and aspirin, which does not. A feline model of coronary ischemia using ligation of the anterior descending artery demonstrated that intravenous ibuprofen (2.5-20 mg/kg) given immediately and 2 h after ligation significantly decreased (by about 40%) myocardial infarct size. In contrast, aspirin did not diminish infarct size at any achieved dose; in fact, at some doses it tended to increase infarct size. In vitro studies with purified granulocytes demonstrated a similar dichotomy between ibuprofen and aspirin. Ibuprofen inhibits granulocyte aggregation, superoxide production, lysosomal enzyme release, and granulocyte-mediated endothelial cytotoxicity, while aspirin is without effect on these modalities. We propose that ibuprofen's beneficial effect in experimental myocardial ischemia is related to its ability to inhibit activated granulocytes and thus to diminish myocardial cell death in experimental myocardial infarction.

Animals↗
PubMed1984

Quinidine-induced neutropenia: report of a case with drug-dependent inhibition of granulocyte colony generation.

We describe a case of quinidine-induced agranulocytosis in which in vitro marrow culture studies suggested immune inhibition of committed human granulocyte-macrophage progenitors (CFU-GM). Autologous, but not allogeneic, inhibition of CFU-GM was seen with 'acute' serum from the patient in the presence of quinidine but not other drugs. Cytotoxic antibodies to mature granulocytes were not found. These studies provide a novel mechanism for drug-induced neutropenia and suggest that a battery of in vitro assays of progenitor and of mature granulocyte cytotoxicity might identify offending agents in suspected drug-induced neutropenias.

Agranulocytosis↗
PubMed1984

Bacterial adherence to fibronectin and endothelial cells: a possible mechanism for bacterial tissue tropism.

In the pathophysiology of endocarditis, bacteria must initially adhere to the endothelial surface components of the cardiac valve before invasion and colonization. The attachment of bacteria to endothelial cell surfaces is dependent on surface characteristics of both the bacteria and the endothelial cell. Fibronectin, a glycoprotein produced by endothelial cells, binds to some bacteria but not all. This report examines bacterial adherence to human endothelial cells and to fibronectin-coated surfaces. Radiolabeled Staphylococcus aureus (Cowan I strain) and viridans streptococci avidly bound to fibronectin-coated surfaces and endothelial cell monolayers. In contrast, gram-negative organisms such as Escherichia coli bound poorly to both substrates. The adherence of S. aureus was dependent on time as well as on the concentration of fibronectin or the endothelial cell number. Bacterial adherence was specific for endothelial cells or fibronectin, since none occurred to plastic or to wells coated with collagen or albumin. The binding of S. aureus to fibronectin or endothelial cells appeared dependent on a bacterial surface protein, since treatment of the bacteria with proteases markedly decreased adherence. S. aureus was not dependent on the protein A or teichoic acid content of the cell wall, but adherence was markedly decreased in bacterial strains that had a carbohydrate capsule. S. aureus pretreated with serum or purified fibronectin manifested enhanced adherence to endothelial cells, suggesting fibronectin-fibronectin interactions. Bacteria specifically attach to endothelial cells and to fibronectin-coated surfaces, which suggests that the ability of a bacterium to attach to these substrates may reflect the propensity to invade and colonize vascular tissues such as cardiac valves.

Bacterial Physiological Phenomena↗
PubMed1984

Insufflated red cells protect lungs from hyperoxic damage: role of red cell glutathione in scavenging toxic O2 radicals.

Hyperoxia-mediated pulmonary damage may involve formation of toxic oxygen species such as superoxide, hydrogen peroxide, and hydroxyl radical. Intact red cells evidently scavenge these when insufflated in small numbers into the tracheobronchial tree of rats. Such manipulation protects hyperoxic rats for prolonged periods of time and preserves normal pulmonary histology. Of several potential oxygen metabolite scavengers, a role for red cell glutathione seems particularly likely. It has not escaped our attention that an ironic, and previously unsuspected, connotation of our results emerges: namely, that a small degree of spontaneous alveolar bleeding, which is not an uncommon feature in respiratory distress situations, may actually be beneficial to patients--particularly those ventilated with excessive inspired oxygen concentrations. If confirmatory studies from other laboratories are forthcoming, the tracheal insufflation of autologous red cells in ventilated patients might be considered in the future.

Animals↗