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Biomedical subjects

H S Jacob

Publications and source records attributed to H S Jacob.

196 records · Page 11Linked to original sources
PubMed1968

Altered sulfhydryl reactivity of hemoglobins and red blood cell membranes in congenital Heinz body hemolytic anemia.

The mechanisms of hemoglobin precipitation into Heinz bodies and hemolytic anemia that characterize congenital Heinz body hemolytic anemia (CHBHA) were studied in patients with the unstable hemoglobins, Köln (beta-98 valine --> methionine) and Hammersmith (beta-42 phenylalanine --> serine). The cysteines in the 93rd position of the beta-chains of CHBHA hemoglobins bound glutathione excessively in mixed disulfide linkage. The resulting diminished "free" GSH within the cell accelerated hexose monophosphate shunt metabolism. The unique precipitability of CHBHA hemoglobins when heated at 50 degrees C could be induced in normal hemoglobin A by artificially blockading its sulfhydryl groups with paramercuribenzoate (PMB). Reflecting the previously reported excessive flux of hemes from hemoglobin Köln, the expected heme/globin ratio in this hemoglobin was reduced by 30%. The further increment in heme loss that occurs with heat (50 degrees C) underlies the unique heat precipitability of CHBHA hemoglobins; it was retarded if detachment of heme was inhibited by cyanide or carbon monoxide.Heinz bodies were attached to red cell membrane thiol groups presumably through mixed disulfide bonds, being released by mercaptoethanol. Binding of hemoglobin Köln-(59)Fe to red cell ghosts, which was markedly enhanced when Heinz bodies were generated at 50 degrees C, was inhibited if membrane thiols were preblockaded by PMB. The depletion of membrane thiols by their reaction with Heinz bodies rendered CHBHA red cells hypersusceptible to membrane sulfhydryl inhibitors, as manifested by inordinate cation leakage, osmotic fragility, and autohemolysis. We conclude that both cellular and membrane thiols bind beta-93 sulfhydryls of CHBHA hemoglobins as mixed disulfides. Concomitantly, heme avidity to beta-92 lessens, suggesting that degradation of the resulting excessively freed heme may produce the pigmented dipyrroluria of this syndrome. Heinz bodies, reflecting the heightend precipitability of heme-deficient globin, attach to, thereby depleting, membrane sulfhydryl groups. This, as shown previously, could underlie the hemolytic anemia of this syndrome by causing membrane hyperpermeability, premature splenic entrapment, and ultimately osmotic destruction of red blood cells.

Anemia, Hemolytic, Congenital↗
PubMed1967

Concomitant alterations of sodium flux and membrane phospholipid metabolism in red blood cells: studies in hereditary spherocytosis.

The role of membrane phosphatides in transport processes has been investigated in red cells from splenectomized patients with hereditary spherocytosis (HS). Incorporation of inorganic (32)phosphate into the membrane phosphatides of HS red cells was approximately twice normal, coinciding with the nearly twofold increment in flux of sodium ions in the cells.A consistent, inordinate increase in specific activity of a chromatographic fraction containing phosphatidylserine provided the bulk of the over-all increase in labeling of HS red cell phosphatides. The specific activity of phosphatidic acid was increased but not consistently. Radioactivity of the "acidic phosphatides" (phosphatidylserine and phosphatidic acid fractions) decreased, in general, when the sodium flux was low, i.e., when the cells were suspended in media of low sodium content. When the cation flux was elevated (hypotonic media), there was a marked (ca. 35%) increase in the labeling of phosphatidylserine fractions. Normal red cells whose permeability to cations was increased by exposure to 0.5 N butanol also exhibited increased labeling of acidic phosphatides. Considerations of the stoichiometry of cation transport and phosphatide labeling make it unlikely that phospholipids act directly as carrier molecules for cations in red cell membranes. On the other hand, the involvement of these lipid substances in cation movements is substantiated by correlating several different states of sodium flux with the labeling of the phosphatidic acid and phosphatidylserine fractions.

Biological Transport↗
PubMed1967

Membrane lipid depletion in hyperpermeable red blood cells: its role in the genesis of spherocytes in hereditary spherocytosis.

Hereditary spherocytosis (HS) red cells lose membrane lipids excessively during incubation in vitro. Individual phosphatides as well as cholesterol are lost in proportion to their content in membranes, suggesting that fragments of membrane are removed. Supplementation of HS red cells with glucose during incubation has no consistent protective effect, whereas diminishing the excessive sodium flux through these cells by suspending them in either sodium-free or hypertonic media prevents membrane fragmentation. The characteristic excessive increase in osmotic fragility which occurs in incubated HS red cells results both from inordinate accumulation of intracellular sodium ions which produces osmotic swelling, and from depletion of surface material which generates microspherocytosis. Inhibiting both of these processes by incubating HS red cells in sodium-free media completely prevents increases in osmotic fragility despite prolonged incubation. Normal red cells rendered hyperpermeable to cations by exposure either to n-butanol or to inhibitors of membrane sulfhydryl groups, lose membrane lipid upon incubation in a similar fashion to untreated HS red cells; perfectly smooth microspherocytes, akin to those seen in HS, are thereby generated.I conclude that depletion of membrane lipids in HS which leads to microspherocytosis is correlatable with the excessive cation flux and possibly to the stimulated metabolism of acidic phosphatides in these red cells. It is suggested that this relation is derived from the fact that these phosphatides are in some way involved in maintaining the proper alignment of repeating membrane lipoprotein units, and that this function is adversely affected when these molecules are turning over more rapidly in response to increased cation flux.

Benzoates↗
PubMedDate not supplied

Plasma exchange in the treatment of immune disease.

Plasma exchange was investigated as an alternative to the use of toxic drugs to remove unwanted antibody. Studies in rabbits immunized with bovine serum albumin demonstrate that exchange transfusion after a primary immunization results in a rebound of antibody to above preexchange levels. However, exchange transfusion seven, 11, or 18 days after secondary immunization results in permanent lowering of antibody levels. Plasma exchange with the continuous flow centrifuge was used in four patients with hematologic diseases. White cell isoantibodies were removed in a septic leukopenic patient, permitting white cell transfusions. Two patients with immune thrombocytopenia were exchanges; one showed prompt and permanent elevation of platelet count, while the other did not improve. A patient with immune hemolytic anemia had stabilization of hemoglobin levels and decreased Coombs reactivity following plasma exchange.

Adult↗
PubMedDate not supplied

Hemin: a possible physiological mediator of low density lipoprotein oxidation and endothelial injury.

Oxidized low density lipoprotein (LDL), formed in vivo from presently unknown reactions, may play a role in atherogenesis. In vitro, transition metals such as iron and copper will facilitate LDL oxidation, but these metals are unlikely to exist in free form in normal body fluids. We have explored the possibility that LDL oxidation may be promoted by heme, a physiologically ubiquitous, hydrophobic, iron-containing compound. Indeed, during several-hour incubation, heme caused extensive oxidative modification of LDL; however, such modification requires only minutes in the presence of small amounts of H2O2 or preformed lipid hydroperoxides within the LDL. Oxidative interactions between heme, LDL, and peroxides lead to degradation of the heme ring and consequent release of heme iron, which further accelerates heme degradation. Coupled (evidently iron-catalyzed) heme degradation and LDL oxidation are both effectively inhibited by hydrophobic antioxidants and iron chelators. That such hemin-induced LDL oxidation may be involved in atherogenesis is supported by the finding that LDL oxidized by hemin is extremely cytotoxic to cultured aortic endothelial cells. Overall, these investigations not only lend support to the idea that LDL oxidation by physiological substances such as heme may play a role in the process of atherogenesis but also may have broader implications, as similar oxidative reactions between heme and unsaturated fatty acids may occur consequent to hemorrhagic injury.

Catalysis↗
PubMedDate not supplied

Neutrophil oxidants inactivate alpha-1-protease inhibitor and promote PMN-mediated detachment of cultured endothelium. Protection by free methionine.

Activated granulocytes have been implicated in mediating pulmonary endothelial damage in the Adult Respiratory Distress Syndrome. In another lung disease, emphysema, pulmonary granulocytes (PMNs) are thought to be doubly responsible for lung dissolution: they release potent proteolytic enzymes including elastase, and they generate reactive oxygen species that oxidize a reactive site methionine group in alpha-1-protease inhibitor (alpha-1-PI) rendering it, in turn, impotent as an anti-elastase. This suggested an analogous scenario for pulmonary vascular damage: namely, undefended PMN elastase might also mediate endothelial injury. Our strategy to prove this notion used 51chromium-labeled human endothelial cells exposed to intact PMN or to enucleate "neutroplasts." The latter are elastase-free cytoplasmic blebs derived from PMN. When activated, both PMN and neutroplasts generate similar amounts of toxic oxygen species; yet neutroplasts caused insignificant endothelial damage, measured as 51Cr "lift-off"from anchoring matrix (PMN = 24.3% +/- 1.8% vs neutroplast = 1.2% +/- 0.4%; p less than 0.001). Adding pure elastase back to neutroplasts increased endothelial cell lift-off (7% +/- 0.2%). Although the prototypic serine protease inhibitor phenyl methylsulfonylfluoride (PMSF) protected endothelium from PMNs, pure alpha-1-PI (also a potent anti-elastase) when added in physiologic amounts did not protect endothelial cells from PMN assault, suggesting that PMN oxidants might inactivate it. By adding exogenous myeloperoxidase (MPO) to MPO-deficient neutroplasts, we demonstrated that MPO-dependent oxidants, probably N-chloramines, are critical inactivators of alpha-1-PI. This was further confirmed since added free methionine, a scavenger of chloramine, protected alpha-1-PI from inactivation by reagent chloramine or that produced by rearmed neutroplasts or PMN.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Proteins↗