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Biomedical subjects

H S Jacob

Publications and source records attributed to H S Jacob.

At least 145 records · Page 8Linked to original sources
PubMed1978

Plasma exchange in the treatment of fulminant idiopathic (autoimmune) thrombocytopenic purpura.

Rapid plasma exchange in a young man with idiopathic (autoimmune) thrombocytopenic purpura and life-threatening haemorrhage acutely increased the platelet-count and enhanced haemostasis. The patient had not responded to steroids, and massive intra-abdominal bleeding had developed after splenectomy, despite numerous platelet transfusions. After plasma exchange, his haemoglobin concentration became normal without further transfusion and his abdominal girth decreased. Therefore emergency reoperation because of intra-abdominal bleeding was no longer required. A cumulative-sums plot of his platelet-count confirmed that plasmapheresis on 2 occasions was followed by a pronounced rise in mean platelet-count. Neither prednisone nor vincristine therapy altered the slope of the plot. The high initial anti-platelet antibody concentration in this patient fell after plasma exchange. These findings indicate that plasmapheresis accelerated clearance of circulating anti-platelet factors in fulminant idiopathic thrombocytopenic purpura.

Adult↗
PubMed1978

Folate-induced remission in aplastic anemia with familial defect of cellular folate uptake.

Severe aplastic anemia developed in a young man with an extensive family history of leukemia, pancytopenia, and neutropenia. Megaloblastic changes became evident, and treatment with high doses of folic acid resulted in striking clinical improvement. However, red-cell folate levels remained persistently low despite high serum folate levels. A defect in cellular folate uptake was suspected, and, indeed, uptake of 5-14CH3-H4-folate by stimulated lymphocytes and by bone-marrow cells from the patient was significantly reduced (P less than 0.05 as compared to normal cells. Further characterization of folate metabolism showed that intestinal absorption of the vitamin, membrane transport of 5-14CH3-H4-folate by mature red cells, folate utilization in the conversion of deoxyuridylate to thymidylate and polyglutamate formation were all normal. At least five other family members manifest decreased uptake of 5-14CH3-H4-folate by stimulated lymphocytes. These studies suggest that a genetically induced abnormality of folate uptake contributed to this patient's severe, but reversible, aplasia.

Adult↗
PubMed1978

Calcium-induced damage of haemoglobin SS and normal erythrocytes.

An ionophore specific for divalent cations has been used to load normal erythrocytes and erythrocytes from patients with sickle cell anaemia (Hb SS disease), with small amounts of calcium. Such calcium accumulation leads to decreased cellular water, potassium, adenosine triphosphate (ATP), and osmotic fragility, all characteristics of irreversibly sickled cells (ISCs). In addition, calcium loading of Hb SS, but not normal, erythrocytes causes a marked decrease of haemoglobin oxygen affinity; another, and specific, hallmark of ISCs. Ionophore-induced accumulation of calcium by deoxygenated Hb SS erythrocytes also leads to temporary retention of sickled shape following reoxygenation, despite the absence of detectable intracellular haemoglobin S fibres. All these effects require calcium in the incubation medium and support the idea that increased intracellular calcium is important in the formation of ISCs in patients with Hb SS disease.

Anemia, Sickle Cell↗
PubMed1978

Oxygen radicals mediate endothelial cell damage by complement-stimulated granulocytes. An in vitro model of immune vascular damage.

During hemodialysis, alternative pathway complement activation leads to pulmonary sequestration of granulocytes, with loss of pulmonary vascular endothelial integrity and, at times, protein-rich pulmonary edema. An in vitro model of this phenomenon was constructed utilizing 51Cr-labeled human umbilical vein endothelial cell cultures. In this system, granulocytes, when exposed to activated complement (C), induce endothelial damage; this injury is mediated primarily by oxygen radicals produced by the granulocytes. C5a appears to be the C component responsible for granulocyte-induced cytotoxicity; studies with cytochalasin B-treated granulocytes suggest that close approximation of the granulocytes and endothelial cells is necessary for maximal cell injury.

Blood Vessels↗
PubMed1978

The mechanism of 5-methyltetrahydrofolate transport by human erythrocytes.

The mechanism involved in 5-methyltetrahydrofolate uptake by human cells is poorly understood. To more clearly elucidate this physiologically important process, transport of the vitamin was studied in human erythrocytes. 5-methyltetrahydrofolate uptake was found to increase with reticulocytosis, but measurable incorporation occurred in erythrocyte suspensions depleted of reticulocytes, leukocytes, and platelets, indicating uptake by mature erythrocytes. Incubation of erythrocytes with increasing concentrations of [(14)C]5-methyltetrahydrofolate resulted in increasing uptake but decreasing percentage incorporation, consistent with saturation of a carrier system. Both influx and efflux phases of uptake were temperature dependent, with almost no transport at 4 degrees C. Uptake of [(14)C]5-methytetrahydrofolate was effectively inhibited by unlabeled 5-methyltetrahydrofolate, 5-formyltetrahydrofolate, and methotrexate, but not by pteroylglutamic acid. Prior incubation with 5-formyltetrahydrofolate increased uptake of [(14)C]5-methyltetrahydrofolate, and extracellular 5-formyltetrahydrofolate enhanced efflux of [(14)C]5-methyltetrahydrofolate. Nearly total depletion of ATP increased uptake of [(14)C]5-methyltetrahydrofolate, but efflux was unchanged. Column chromatography of membrane-free hemolysate after incubation with [(14)C]5-methyltetrahydrofolate showed 95% of radioactivity corresponded to marker radioisotope, and no other peak was noted. Thus peripheral erythrocytes incorporate 5-methyltetrahydrofolate by a saturable, temperature-dependent, substrate-specific process which is influenced by counter-transport. This mechanism is qualitatively similar to the carrier-mediated transport of folate compounds previously described in other cell types. Therefore, human erythrocytes should be useful for detailed characterization of this membrane carrier system.

Anemia, Aplastic↗
PubMed1978

Monoclonal gammopathy in hereditary spherocytosis: a possible pathogenetic relation.

Two cases of monoclonal gammopathy in patients with hereditary spherocytosis led us to consider the possible pathogenetic relation between these two disorders. Twelve adult patients with hereditary spherocytosis had significant hypergammaglobulinemia in comparison to normal subjects. Retrospective analysis of previous illness in 140 patients with multiple myeloma showed a significant association between IgA myeloma and previous gallbladder disease. We propose that the chronic reticuloendothelial stimulation due to extravascular hemolysis, possibly potentiated by the inflammation associated with cholelithiasis and cholecystitis, may foster neoplastic transformation of immunocytes in patients with hereditary spherocytosis, ultimately leading to the development of monoclonal gammopathy.

Aged↗
PubMed1977

In vitro granulocyte adherence and in vivo margination: two associated complement-dependent functions. Studies based on the acute neutropenia of filtration leukophoresis.

To study mechanisms and mediators regulating the distribution of intravascular granulocytes between circulating and marginated pools, a human model with extreme transient margination, the neutropenia of continuous flow filtration leukophoresis, was analyzed. Studies in animals demonstrated the existence of a complement (C)-derived granulocytopenia-inducing factor. Thus, autologous plasma, exposed to nylon fibers (NF) of the filtration system, produced an acute selective decrement of circulating granulocytes and monocytes. This phenomenon was blocked by decomplementing plasma, by pretreatment of plasma with EDTA or hydrazine, and by preheating at 56 degrees C, but did occur after recombination of heat-inactivated and hydrazine-treated plasma before NF exposure. Preheating plasma at 50 degrees C did not inhibit the neutropenic response, suggesting involvement of the classical pathway of C activation. Ultrafiltration studies indicated that the NF-provoked neutropenia-inducing factor has a mol wt in the range of 10,000-30,000, and is heat stable (56 degrees C). To analyze the hypothesis that C- induced neutrophil margination might be consequent to increased cell adhesiveness to endothelial surfaces, the role of C in promoting granulocyte adherence was evaluated in vitro. Measured with a plastic Petridish assay, granulocyte adherence was significantly reduced in heat- inactivated (56 degrees C) and hydrazine-treated plasma, but adherence promoting capacity was restored by mixing the two plasmas, or by adding purified C3 to hydrazine-treated plasma. After exposure to activated C, neutrophils showed significantly increased adhesiveness which was maintained when cells were resuspended in heat-inactivated plasma, but progressively lost when resuspended in fresh plasma. On the basis of these results we conclude that granulocyte adhesiveness in vitro and margination in vivo are closely associated, C-dependent phenomena.

Agranulocytosis↗
PubMed1977

Complement and leukocyte-mediated pulmonary dysfunction in hemodialysis.

During hemodialysis, cardiopulmonary decompensation may appear in uremic patients, possibly caused by plugging of pulmonary vessels by leukocytes. In 34 patients we noted leukopenia (20% of initial levels) during hemodialysis that in 15 was associated with impaired pulmonary function. When we infused autologous plasma, incubated with dialyzer cellophane, into rabbits and sheep, sudden leukopenia and hypoxia occurred, with doubling of pulmonary-artery pressures and quintupling of pulmonary-lymph effluent. Histologic examination showed severe pulmonary-vessel-leukostasis and interstitial edema. The syndrome was prevented by preinactivation of complement but was reproduced by infusions of plasma in which complement was activated by zymosan. Thus, acute pulmonary dysfunction from complement-mediated leukostasis may play a major part in the acute cardiopulmonary complications of cellophane-membrane hemodialysis.

Adolescent↗
PubMed1977

Hemodialysis leukopenia. Pulmonary vascular leukostasis resulting from complement activation by dialyzer cellophane membranes.

Acute leukopenia occurs in all patients during the first hour of hemodialysis with cellophanemembrane equipment. This transient cytopenia specifically involves granulocytes and monocytes, cells which share plasma membrane reactivity towards activated complement components. The present studies document that complement is activated during exposure of plasma to dialyzer cellophane, and that upon reinfusion of this plasma into the venous circulation, granulocyte and monocyte entrapment in the pulmonary vasculature is induced. During early dialysis, conversion of both C3 and factor B can be demonstrated in plasma as it leaves the dialyzer. Moreover, simple incubation of human plasma with dialyzer cellophane causes conversion of C3 and factor B, accompanied by depletion of total hemolytic complement and C3 but sparing of hemolytic C1. Reinfusion of autologous, cellophane-incubated plasma into rabbits produces selective granulocytopenia and monocytopenia identical to that seen in dialyzed patients. Lungs from such animals reveal striking pulmonary vessel engorgement with granulocytes. The activated complement component(s) responsible for leukostasis has an approximate molecular weight of 7,000-20,000 daltons. Since it is generated in C2-deficient plasma and is associated with factor B conversion, it is suggested that activation of complement by dialysis is predominantly through the altermative pathway.

Adult↗
PubMed1977

Complement (C5-a)-induced granulocyte aggregation in vitro. A possible mechanism of complement-mediated leukostasis and leukopenia.

Activated plasma complement will induce biphasic aggregation of human granulocytes dectable by standard nephelometric techniques. The responsible active component was suggested to be C5a by molecular weight and heat-stability assays; moreover, aggragating activity was ablated by anti-C5 but not anti-C3 antibodies. C5a prepared by trypsinization of purified C5 reproduced the aggregating activity of whole activated plasma, whereas plasma from a C5-deficient donor did not support aggregation. Embolization of granulocyte aggregates might be a previously unsuspected cause of leukostasis and pulmonary damage in various clinical situations where intravascular complement activation occurs.

Cell Aggregation↗