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Biomedical subjects

E L Thomas

Publications and source records attributed to E L Thomas.

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

Retinal and choroidal vascular occlusion following intralesional corticosteroid injection of a chalazion.

Unilateral visual loss following periocular corticosteroid injection is a reported complication of injections of tonsillar, nasal, scalp, and retrobulbar sites. This is the first reported case, to our knowledge, of intralesional corticosteroid injection of a chalazion producing ipsilateral microembolization and infarction of retinal and choroidal vasculature. An eight-year-old boy underwent reexcision of an upper lid chalazion under general anesthesia. Intraoperatively, 0.5 ml of depot-steroid preparation was injected into the excision site. Postoperatively, vision was unilaterally reduced to light perception only. Examination revealed an afferent pupillary defect, retinal and choroidal emboli, retinal edema, and a macular "cherry red spot". Anterior chamber paracentesis, carbon dioxide rebreathing, carbonic anhydrase inhibitors and ocular massage failed to change the embolic pattern. No visual recovery resulted. Fundus photography and fluorescein angiography demonstrated occlusion of the retinal and choroidal vasculature. Extreme care should be exercised during and immediately following intralesional corticosteroid injection of chalazia.

Child↗
PubMed1985

Evidence for a role of taurine in the in vitro oxidative toxicity of neutrophils toward erythrocytes.

Production of hydrogen peroxide and secretion of myeloperoxidase by stimulated neutrophils resulted in myeloperoxidase-catalyzed oxidation of chloride to hypochlorous acid (HOCl), the reaction of HOCl with taurine to yield taurine monochloramine (TauNHCl), and accumulation of TauNHCl in the extracellular medium. When erythrocytes were present, the yield of TauNHCl was lower as the result of uptake of TauNHCl into erythrocytes. The zwitterion taurine was not taken up, but the anion TauNHCl and other anionic oxidants including taurine dichloramine (TauNCl2) and L-alanine chloramines were transported into erythrocytes by the anion-transport system. Oxidation of intracellular components such as glutathione (GSH) by taurine chloramines resulted in reduction of the chloramines and trapping of taurine within erythrocytes. At high oxidant:erythrocyte ratios, TauNHCl also oxidized hemoglobin (Hb) and depleted ATP, but caused little lysis. TauNCl2 was much more effective as a lytic agent. At low oxidant:erythrocyte ratios, the chloramines caused net loss of GSH when no glucose was provided, but Hb was not oxidized and GSH content returned to normal when glucose was added. Therefore, anionic chloramines may mediate oxidative toxicity when the neutrophil:erythrocyte ratio is high. Under more physiologic conditions, chlorination of taurine by neutrophils and the uptake and reduction of TauNHCl by erythrocytes prevents accumulation of oxidants and may protect blood cells, plasma components, and tissues against oxidative toxicity.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1984

Chlorination of endogenous amines by isolated neutrophils. Ammonia-dependent bactericidal, cytotoxic, and cytolytic activities of the chloramines.

Isolated human neutrophilic leukocytes were stimulated to produce hydrogen peroxide (H2O2) and to secrete cytoplasmic granule components including myeloperoxidase into the medium. Myeloperoxidase catalyzed the oxidation of chloride (Cl-) by H2O2 to yield hypochlorous acid (HOCl), which reacted with endogenous nitrogen compounds to yield derivatives containing nitrogen-chlorine (N-Cl) bonds. Compounds available for reaction with HOCl were ammonia (NH+4), taurine, alpha-amino acids, and granule proteins and peptides that were released into the medium. A portion of the N-Cl derivatives formed under these conditions accumulated in the extracellular medium. These long lived oxidizing agents were characterized as hydrophilic, low molecular weight, mono-N-chloramine (RNHCl) derivatives based on their absorption spectrum, ability to oxidize 5-thio-2-nitrobenzoic acid and to chlorinate ammonia (NH+4), and behavior upon ultrafiltration, gel chromatography, and extraction with organic solvents. The RNHCl derivatives were of low toxicity, but reacted with NH+4 to yield the lipophilic oxidizing agent monochloramine (NH2Cl). Therefore, the addition of NH+4 conferred bactericidal, cytotoxic, and cytolytic activities on the RNHCl derivatives. The results indicate that taurine and other neutrophil amines protect neutrophils and other cells against oxidative attack by acting as a trap for HOCl and by competing with endogenous NH+4 for reaction with HOCl. However, the RNHCl derivatives act as a reserve of oxidizing equivalents that is converted to a toxic form when an increase in NH+4 concentration favors formation of NH2Cl.

Amines↗
PubMed1984

Role of monochloramine in the oxidation of erythrocyte hemoglobin by stimulated neutrophils.

Stimulation of the oxygen (O2) metabolism of isolated human neutrophilic leukocytes resulted in oxidation of hemoglobin of autologous erythrocytes without erythrocyte lysis. Hb oxidation could be accounted for by reduction of O2 to superoxide (O-2) by the neutrophils, dismutation of O-2 to yield hydrogen peroxide (H2O2), myeloperoxidase-catalyzed oxidation of chloride (Cl-) by H2O2 to yield hypochlorous acid (HOCl), the reaction of HOCl with endogenous ammonia (NH+4) to yield monochloramine ( NH2Cl ), and the oxidative attack of NH2Cl on erythrocytes. NH2Cl was detected when HOCl reacted with the NH+4 and other substances released into the medium by neutrophils. The amount of NH+4 released was sufficient to form the amount of NH2Cl required for the observed Hb oxidation. Oxidation was increased by adding myeloperoxidase or NH+4 to increase NH2Cl formation. Due to the volatility of NH2Cl , Hb was oxidized when neutrophils and erythrocytes were incubated separately in a closed container. Oxidation was decreased by adding catalase to eliminate H2O2, dithiothreitol to reduce HOCl and NH2Cl , or taurine to react with HOCl or NH2Cl to yield taurine monochloramine . NH2Cl was up to 50 times more effective than H2O2, HOCl, or taurine monochloramine as an oxidant for erythrocyte Hb, whereas HOCl was up to 10 times more effective than NH2Cl as a lytic agent. NH2Cl contributes to oxidation of erythrocyte components by stimulated neutrophils and may contribute to other forms of neutrophil oxidative cytotoxicity.

Catalase↗
PubMed1984

Disulfide reduction and sulfhydryl uptake by Streptococcus mutans.

Incubation of Streptococcus mutans cells with certain disulfide compounds resulted in accumulation of reduced sulfhydryl compounds in the extracellular medium or in both the medium and the cells. Oxidized lipoic acid and lipoamide competed for reduction. At high concentrations, these compounds were reduced at rates comparable to that of glucose metabolism, and all of the increase in sulfhydryls was in the medium. Cystamine did not compete with these compounds for reduction but was also reduced at high rates and low apparent affinity, and all of the cysteamine produced from cystamine accumulated in the medium. In contrast, glutathione disulfide (GSSG) and L-cystine were reduced slowly but with high apparent affinity, and 60 to 80% of the increase in sulfhydryls was intracellular. NADH-dependent lipoic acid or lipoamide reductase activity was present in the particulate (wall-plus-membrane) fraction, whereas NADPH-dependent GSSG reductase activity was present in the soluble (cytoplasmic) fraction. Two transport systems for disulfide and sulfhydryl compounds were distinguished. GSSG, L-cystine, and reduced glutathione competed for uptake. L-Cysteine was taken up by a separate system that also accepted L-penicillamine and D-cysteine as substrates. Uptake of glutathione or L-cysteine, or the uptake and reduction of GSSG or L-cystine, resulted in up to a 10-fold increase in cell sulfhydryl content that raised intracellular concentrations to between 30 and 40 mM. These reductase and transport systems enable S. mutans cells to create a reducing environment in both the extracellular medium and the cytoplasm.

Biological Transport↗
PubMed1983

Inhibition of Streptococcus mutans by the lactoperoxidase antimicrobial system.

Inhibition of bacterial metabolism by the lactoperoxidase (LP)-hydrogen peroxide (H2O2)-thiocyanate system was studied with representatives of serotypes a through g of Streptococcus mutans. The aims were to determine whether the amount of H2O2 released from these catalase-negative bacteria is sufficient to activate the LP system and whether these oral bacteria are resistant to inhibition by the LP system, which is active in human saliva. When the washed, stationary-phase cells were incubated aerobically with LP, thiocyanate, and glucose (Glc), greater than 90% inhibition of Glc utilization and lactate production was obtained with strains that released large amounts of H2O2 (BHT, FA-1, OMZ-176); 20 to 50% inhibition was obtained with strains that released about half as much H2O2 (B-13, Ingbritt); and no inhibition was obtained with strains that released only small amounts of H2O2 (AHT, HS-6, GS-5, LM-7, OMZ-175, 6715-15). Inhibition was most effective at pH 5, whereas release of H2O2 and accumulation of the inhibitor (hypothiocyanite ion) were highest at pH 8. With H2O2-releasing cells from early stationary phase, preincubation with Glc abolished inhibition, though it did not influence H2O2 release. Cells harvested 24 h later were depleted of sulfhydryl compounds. Inhibition of these cells was abolished by preincubation with Glc and certain sulfhydryl or disulfide compounds (reduced or oxidized glutathione, cysteine or cystine). This preincubation increased cell sulfhydryl content but had no effect on H2O2 release. All strains were inhibited when incubated with LP, thiocyanate, and added (exogenous) H2O2. Smaller amounts of H2O2 were required to inhibit at pH 5, and larger amounts were required to inhibit cells preincubated with Glc or with Glc and the sulfhydryl or disulfide compounds. The results indicate that pH, amount of H2O2, cell sulfhydryl content, and stored-carbohydrate content determine susceptibility to inhibition.

Disulfides↗
PubMed1983

Oxygen metabolism of Streptococcus mutans: uptake of oxygen and release of superoxide and hydrogen peroxide.

Oxygen (O2) uptake and release of O2 metabolites to the extracellular medium were studied with representatives of serotypes a through g of Streptococcus mutans. When incubated with glucose, washed cells of all strains took up O2 at rates proportional to the O2 concentration. When O2 was held constant at 0.2 mM, 0.2 to 0.5 mol of O2 was taken up per mol of glucose metabolized. Despite the similar rates of O2 uptake, the strains fell into three classes according to the amount of hydrogen peroxide (H2O2) released. Strains BHT, FA-1, and OMZ-176 released up to 90% of O2 taken up as H2O2, which accumulated in the medium to concentrations as high as 2 mM. The high levels of H2O2 accumulation were correlated with low ability to reduce exogenous H2O2 to water. Strains Ingbritt and B-13 released about half as much H2O2, but H2O2 in the medium did not exceed 0.05 to 0.1 mM. Strains HS-6, AHT, GS-5, OMZ-175, LM-7, and 6515-15 released less than 10% of O2 taken up as H2O2, and H2O2 did not accumulate. Within this class, strains HS-6 and AHT released about 6% of O2 taken up as superoxide (O2-). Release of O2 metabolites was correlated with enzyme activities in cell-free extracts. Extracts from all strains catalyzed NADH-dependent O2 uptake. Extracts from H2O2-accumulating strains produced H2O2 when incubated with NADH and O2 and had low ability to catalyze NADH-dependent reduction of H2O2. Extracts from HS-6 and AHT had low superoxide dismutase activity, which may account for O2- release and the O2-sensitive growth of these strains.

Hydrogen Peroxide↗
PubMed1983

Irreversible visual loss in Waldenström's macroglobulinaemia.

A patient with Waldenström's macroglobulinaemia presented with visual reduction in both eyes. The funduscopic and angiographic demonstrations of venous engorgement ('string of sausages'), retinal haemorrhages at all levels, retinal and disc oedema, and serous detachment of the maculas were consistent with this diagnosis. The cryoprecipitation of the immunoglobulin at a temperature slightly below body temperature precluded routine blood studies and plasmapheresis. Plasmapheresis was ultimately performed without difficulty with the patient and equipment at 88 degrees F (31 degrees C). Despite marked improvement in the funduscopic and angiographic appearance of the retina, perifoveal capillary nonperfusion and serous elevation of the macula persisted. Even when the maculas flattened in both eyes, no visual recovery occurred. Early diagnosis, even on a clinical basis when laboratory studies cannot be performed, and early plasmapheresis to reduce serum viscosity are warranted to prevent intravascular occlusion in the perifoveal capillary bed, deposition of immunoglobulin in the retina, and transudation in the subretinal space.

Blood Viscosity↗
PubMed1983

Myeloperoxidase-dependent effect of amines on functions of isolated neutrophils.

Isolated neutrophilic leukocytes were incubated with primary amines and related nitrogenous compounds. Stimulation of neutrophil oxygen (O2) metabolism with phorbol myristate acetate or opsonized zymosan resulted in production of hydrogen peroxide (H2O2), myeloperoxidase-catalyzed oxidation of chloride (C1-) to hypochlorous acid (HOC1), and the reaction of HOC1 with the added compounds to yield nitrogen-chlorine (N-C1) derivatives. Formation of N-C1 derivatives of low lipid solubility resulted in accumulation of the derivatives in the extracellular medium. These oxidizing agents were identified and measured on the basis of their absorption spectra and their ability to oxidize 5-thio-2-nitrobenzoic acid to the disulfide form. The yield of N-Cl derivatives was in the order: taurine greater than Tris greater than spermidine greater than spermine greater than glucosamine greater than putrescine greater than guanidinoacetate. Accumulation of N-C1 derivatives was also observed in the absence of added amines, owing to the reaction of HOC1 with endogenous taurine and other amines that were released from the cells into the medium. In the presence of compounds that yield lipophilic N-C1 derivatives, little or no accumulation of oxidizing agents was observed. Instead, these compounds inhibited the accumulation of N-C1 derivatives that was obtained with taurine, and their effect was competitive with taurine. Inhibition was in the order: methylamine greater than ethanolamine greater than phenylethylamine greater than p-toluenesulfonamide greater than ammonia greater than guanidine. Formation of lipophilic N-C1 derivatives also resulted in inhibition of O2 uptake and glucose metabolism. Inhibition was prevented by adding catalase to eliminate H2O2, dapsone to inhibit myeloperoxidase, taurine to compete for reaction with HOC1, or compounds that are rapidly oxidized by HOC1 or N-C1 derivatives, to reduce these oxidizing agents. The results indicate that: (a) formation of N-C1 derivatives that do not penetrate biological membranes can protect leukocytes against the cytotoxicity of HOC1 and lipophilic N-C1 derivatives, and (b) formation of membrane-permeable N-C1 derivatives in the absence of target cells or readily oxidized substances results in oxidative attack by the N-C1 derivatives on leukocyte components and inhibition of leukocyte functions.

Adult↗
PubMed1982

Myeloperoxidase-catalyzed incorporation of amines into proteins: role of hypochlorous acid and dichloramines.

Myeloperoxidase-catalyzed oxidation of chloride (Cl-) to hypochlorous acid (HOCl) resulted in formation of mono- and dichloramine derivatives (RNHCl and RNCl2) of primary amines. The RNCl2 derivatives could undergo a reaction that resulted in incorporation of the R moiety into proteins. The probable mechanism was attack of RNCl2 or an intermediate formed in the decomposition of RNCl2 on histidine, tyrosine, and cystine residues and on lysine residues at high pH. Incorporation of radioactivity from labeled amines into stable, high molecular weight derivatives of proteins was measured by acid or acetone precipitation and by gel chromatography and electrophoresis. Whereas formation of RNCl2 was favored at low pH, the subsequent incorporation reaction was favored at high pH. Up to several hours were required for the maximum amount of incorporation, which was less than 10% of the label in RNCl2. For the amines tested, incorporation was in the order histamine greater than 1,2-diaminoethane greater than putrescine greater than taurine greater than lysine greater than glucosamine greater than leucine greater than methylamine. Initiation of the reaction required HOCl, and oxidized forms of bromide, iodide, or thiocyanate did not substitute. Inhibitors of incorporation fell into three classes. First, ammonia or amines competed with the labeled amine for reaction with HOCl, so that larger amounts of HOCl were required. Second, readily oxidized substances such as sulfhydryl or diketo compounds or thioethers (methionine) reduced RNCl2. Third, certain compounds competed with protein as the acceptor for the incorporation reaction. The amount required to block incorporation into protein depended on protein concentration. Among these inhibitors were imidazole compounds (histidine), phenols (tyrosine), and disulfides (glutathione disulfide, GSSG). Low yields of derivatives of histidine, tyrosine, and GSSG were detected by thin-layer chromatography. Acid-precipitable derivatives were obtained by reacting RNCl2 with polyhistidine or polytyrosine, and to a lesser extent with polylysine at high pH, but not with other poly(amino acids). Precipitable derivatives were also obtained by incubating MPO-containing extracts from leukocyte granules with hydrogen peroxide, Cl-, and labeled amines. The extracts were found to have a high content of substances with primary amino groups, which competed for incorporation. The results account for oxidative incorporation of amines into proteins in leukocytes and provide evidence that HOCl and nitrogen-chlorine (N-Cl) derivatives are formed in these cells. The characteristics of the incorporation reaction suggest that it would not contribute significantly to the antimicrobial activity of myeloperoxidase (MPO). Nevertheless, the reaction may provide a sensitive method for studying MPO action in vivo.

Amines↗
PubMed1982

Idiopathic progressive unilateral vitreous fibrosis and secondary traction retinal detachment.

Two eyes with idiopathic progressive avascular fibrocellular proliferation involving the posterior vitreous surface and causing visual loss due to traction on the optic nervehead, peripapillary retina, and macula were studied. This occurred in one eye of each of two elderly patients. There were no other apparent abnormalities. Vitreous surgery was used to remove the posterior vitreous surface and most of the abnormal tissue. This reduced the traction on the retina, although partial visual loss persisted because of chronic macular edema in each case. Ultrastructural examination of the excised tissue confirmed the fibrocellular nature of the membranes. New-formed collagen was identified in one case, indicating collagen synthesis by the cellular elements. The cells were identified as fibrocytes and myofibrocytes. The latter cells contained cytoplasmic microfilaments thought to be contractile protein, and contraction of the cells was thought to account for the vitreoretinal traction observed clinically. The origin of these cells could not be established by ultrastructural criteria, although clinical features suggest that cells (possibly fibrous astrocytes) from the optic nervehead were responsible for the cellular proliferation.

Aged↗
PubMed1982

Peroxidase antimicrobial system of human saliva: hypothiocyanite levels in resting and stimulated saliva.

The antimicrobial oxidizing agent hypothiocyanite ion (OSCN-) was measured in resting (drooling) and stimulated (expectorated) whole saliva. Stimulation of the saliva flow rate resulted in a rapid decrease in OSCN- concentration, whereas the thiocyanate ion (SCN-) concentration and peroxidase activity were increased. The decrease in OSCN- levels was greater than could be accounted for by dilution of the whole saliva volume. Assuming that the antimicrobial activity of the salivary peroxidase system is proportional to OSCN- concentration, this system may be more effective in resting saliva than in stimulated saliva.

Adult↗