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Biomedical subjects

A Cerami

Publications and source records attributed to A Cerami.

At least 271 records · Page 15Linked to original sources
PubMed1983

Iron-containing superoxide dismutase from Crithidia fasciculata. Purification, characterization, and similarity to Leishmanial and trypanosomal enzymes.

Leishmania tropica, Trypanosoma brucei, Trypanosoma cruzi, and Crithidia fasciculata have superoxide dismutases which are insensitive to cyanide and sensitive to peroxide and azide, properties characteristic of iron-containing superoxide dismutase. Studies on the superoxide dismutase of C. fasciculata have revealed that: 1) the enzyme is located in the cytosol; 2) isozymes exist; 3) the major superoxide dismutase isozyme (superoxide dismutase 2) has Mr approximately equal to 43,000 and consists of two equal-sized subunits, each of which contains 1.4 atoms of iron. Comparisons of the amino acid content of this crithidial superoxide dismutase with those of superoxide dismutases from other sources suggests that the crithidial enzyme is closely related to bacterial Fe-containing superoxide dismutases, and only distantly related to human Mn- and Cu,Zn-containing superoxide dismutases and to Euglena Fe-containing superoxide dismutase. Attempts are now underway to develop specific inhibitors of the trypanosomatid superoxide dismutase which may be of use in the treatment of leishmaniasis or trypanosomiasis.

Amino Acids↗
PubMed1983

Purification and properties of dihydroorotate oxidase from Crithidia fasciculata and Trypanosoma brucei.

Dihydroorotate oxidases have been highly purified from the parasitic protozoa Crithidia fasciculata and Trypanosoma brucei. The Crithidia enzyme was purified 4200-fold from a crude soluble protein extract in four steps. The protein is a dimer as judged from the native (Mr 60 000) and subunit (Mr 32 700) molecular weights. The purified enzyme exhibits a characteristic flavin electronic spectrum, and each mole of native dimer contains 1.0 mol of tightly bound flavin mononucleotide. Under anaerobic conditions, the flavin chromophore is reduced upon addition of L-dihydroorotate. In air-saturated buffer, the enzyme catalyzes the conversion of L-dihydroorotate to orotate with concomitant reduction of equimolar amounts of molecular oxygen to hydrogen peroxide. A variety of low molecular weight oxidants (e.g., quinones or ferricyanide) may replace oxygen as the electron acceptor during catalysis. The dihydroorotate oxidase of T. brucei was purified 1400-fold to apparent homogeneity by a highly similar isolation procedure. The estimated native (Mr 62 000) and subunit (Mr 30 500) molecular weights indicated a dimeric protein comparable in size to the enzyme from Crithidia. These results suggest that dihydroorotate oxidation is mediated by flavoprotein oxidases in these parasitic protozoa rather than by pterin-linked hydroxylases as recently proposed [Kidder, G. W., & Nolan, L.L. (1973) Biochem. Biophys. Res. Commun. 53, 929-936; Gutteridge, W. E., Dave, D., & Richards, W. H. G. (1979) Biochim. Biophys. Acta 582, 390-401].

Animals↗
PubMed1983

Purification of glutathione reductase from gerbil liver in two steps.

A new method for the isolation of glutathione reductase which successively utilizes chromatography on 2'-5'-ADP-Sepharose 4B and DEAE-Sepharose CL 6B, is described. With these two steps, it was possible to purify to homogeneity the glutathione reductase from gerbil liver. Some molecular properties of the purified enzyme are reported.

Animals↗
PubMed1983

Characterization of antisera to the addition product formed by the nonenzymatic reaction of 16 alpha-hydroxyestrone with albumin.

16 alpha-Hydroxyestrone (16 alpha OHE) has been shown previously to react nonenzymatically with proteins via a Heyns rearrangement of a Schiff base intermediate. Albumin modified by the addition of 16 alpha OHE is immunogenic, despite a relatively low molar substitution. High-titre antisera can be elicited which have a very high affinity toward the estrogen hapten. Cross-reactivity analysis reveals a high specificity for the phenolic A-ring and a lack of specificity to chemical substituents in the D-ring, the site of covalent linkage. The antisera reacts equally well with 16 alpha OHE-peptides as with 16 alpha OHE-lysine, suggesting the utility of this antisera in analyzing either enzymatically or chemically hydrolyzed proteins for the presence of 16 alpha OHE adducts. Immunochemical analysis of proteins modified by 16 alpha OHE may provide insight into the pathogenesis of systemic lupus erythematosus, an autoimmune disease in which elevated levels of 16 alpha OHE are known to occur.

Animals↗
PubMed1983

Effect of arsenical drugs on glutathione metabolism of Litomosoides carinii.

Despite centuries of therapeutic use, the mechanism of action of arsenicals against various diseases remains unknown. Because of the known inhibition of sulfhydryl-containing enzymes by arsenicals, we investigated the possibility that the anti-filarial effects of arsenical drugs might be exerted specifically through impairment of parasite thiol metabolism. We find: (1) arsenicals readily inhibit glutathione reductase of Litomosoides carinii but have little effect upon mammalian enzyme. (2) Administration of Melarsen B to filaria-infected gerbils causes decreases in filarial - but not host - glutathione reductase and reduced glutathione. (3) Such in vivo treatment does not, however, acutely affect parasite energy (ATP) metabolism. These results support the proposition that arsenicals may act through preferential interference with parasite thiol metabolism. The much greater susceptibility of parasite glutathione reductase to inhibition by arsenicals suggests that this enzyme may be a useful point of attack for new drugs.

Adenosine Triphosphate↗
PubMed1983

Inhibition of the growth and differentiation of erythroid precursor cells by an endotoxin-induced mediator from peritoneal macrophages.

Conditioned medium from cultures of mouse macrophages incubated with endotoxin in a serum-free medium contains an inhibitor of the growth and differentiation of erythroid precursor cells of mouse Friend virus-transformed erythroleukemia cells. Endotoxin itself has no inhibitory effect. The endotoxin-induced macrophage mediator inhibits the growth and differentiation of dimethyl sulfoxide-, hexamethylenebisacetamide-, butyric acid-, and hypoxanthine-induced cells but has no effect on hemin-induced cells. The conditioned medium has its maximal inhibitory effect on committed erythroid precursor cells, a decreased effect on uncommitted stem cells, and no effect on fully differentiated erythroid cells. These results demonstrate that endotoxin stimulation of macrophages leads to the production of a humoral factor(s) which is critical for the growth and differentiation of erythroid precursor cells.

Animals↗
PubMed1983

Selective inhibition of synthesis of enzymes for de novo fatty acid biosynthesis by an endotoxin-induced mediator from exudate cells.

An endotoxin-induced mediator from exudate cells markedly suppresses the activities of the key enzymes for de novo fatty acid biosynthesis--acetyl-CoA carboxylase [acetyl-CoA:carbon dioxide ligase (ADP-forming), EC 6.4.1.2] and fatty acid synthetase--in differentiating 3T3-L1 murine preadipocytes. The loss in activity, at least in part, appears to be due to a specific effect on the synthesis of the enzymes, as determined by a decreased incorporation of [35S]methionine into immunoadsorbable acetyl-CoA carboxylase and fatty acid synthetase when the cells were exposed to the mediator. During this exposure, the radiolabeling of proteins with [35S]methionine in a particulate fraction was decreased by nearly 50% with little change in the soluble protein fraction. Sodium dodecyl sulfate/polyacrylamide gel analysis of the labeled protein indicated no major disturbances of protein synthesis in general; however, the syntheses of specific proteins in both the soluble and particulate fractions were enhanced or depressed. The present study demonstrates that endotoxin promotes the release of a mediator from exudate cells that regulates key anabolic activities in adipose cells.

Acetyl-CoA Carboxylase↗
PubMed1983

Preparation of high-potency, non-aggregating insulins using a novel sulfation procedure.

The marked propensity of insulin to self-associate into large aggregates causes significant mechanical problems in insulin delivery devices and may also stimulate production of a tissue-amyloid A precursor in some patients. Although conventionally prepared sulfated insulin (SI) resists aggregation, clinical application has been limited by major insulin bioactivity losses that occur during synthesis. To eliminate this problem, insulin sulfation was carried out in the organic solvent dimethylformamide in the presence of condensing agents such as N,N'-dicyclohexyl carbodiimide (DCC) and a sulfate donor. With this new procedure, the degree of sulfation could be controlled over an eightfold range by varying the amount of condensing agent. The bioactivity of these new SI derivatives varied between 78% and 87% of unmodified insulin. Insulin aggregation, induced by passage through a syringe and needle, did not occur with derivatives having two or more sulfate moieties per insulin molecule. Diffusion velocity studies using "non-aggregated" insulin solutions demonstrated that aggregates were present in crystalline zinc and sodium porcine insulin. In contrast, SI having more than 0.5 mole sulfate per mole of insulin dialyzed as it were predominantly in the monomeric form. Results from the studies described in this report now provide the means for selectively designing and preparing specific high-potency, non-aggregating insulins, which may be necessary for optimal use of current and future insulin delivery devices.

Animals↗
PubMed1983

Glycosylated insulin complexed to Concanavalin A. Biochemical basis for a closed-loop insulin delivery system.

The oligosaccharides maltose, maltotriose, mannotriose, and mannotetrose have been chemically attached to insulin molecules. Incubation of oligosaccharide and insulin at different molar ratios, with or without addition of cyanoborohydride, showed a nearly linear increase in carbohydrate attachment over time. The intravenous t1/2 of 125I-labeled sugar-insulin derivatives was identical to that of unmodified insulin (3.0 min). Biologic activity of these derivatives, assessed in rats by use of a blood glucose depression assay, did not differ significantly from control. These glycosylated insulin molecules are reversibly bound to the glucose-binding lectin Concanavalin A (Con A). Such sugar-insulin/lectin complexes serve as an insulin reservoir from which sugar-insulin molecules are displaced by glucose. Release of sugar-insulin molecules is a function of the particular sugar-insulin and of the ambient glucose concentration. Glucose displacement of glycosylated insulin complexed to Con A is in direct proportion to the amount of glucose present in the surrounding fluid. At each glucose concentration, the relative binding affinity of the maltotriose derivative is less than that of the mannotriose derivative, while the relative binding affinity of both maltotriose and mannotriose are less than that of the mannotetrose derivative. Prolonged incubation at 37 degrees C causes sugar-insulin, like unmodified insulin, to spontaneously aggregate into high-mol-wt, nondiffusable complexes. This aggregation phenomenon was found to be markedly inhibited when glycosylated insulins were synthesized utilizing partially sulfated insulin. Results from the studies described in this report provide the biochemical basis for a closed-loop, glucose-controlled insulin delivery system, utilizing glycosylated insulin complexed to Con A.

Blood Glucose↗
PubMed1983

Excessive nonenzymatic glycosylation of peripheral and central nervous system myelin components in diabetic rats.

The amount of nonenzymatic glycosylation present in normal and diabetic rat peripheral nerve myelin, whole brain, brain myelin, and individual myelin protein components was determined using NaB3H4 reduction followed by either boronic acid affinity chromatography or SDS-polyacrylamide gel electrophoresis (SDS-PAGE). Diabetic peripheral nerve myelin (PNS-M) showed a 5.2-fold increase over normal, indicating that myelin is the major peripheral nerve component undergoing excessive glycosylation in diabetes. SDS-PAGE of diabetic and normal PNS-M showed no differences in the pattern of protein bands or in the distribution of glycosylated adducts. However, in the diabetic, the amount of incorporated radioactivity was 3.74 times greater in the P0 protein and 2.8 times greater in the high-molecular-weight material that did not enter the gel. In whole brain, a 2.4-fold increase in the amount of nonenzymatic glycosylation was observed when diabetic was compared with normal, while diabetic brain myelin (CNS-M) was 3.8 times more glycosylated than normal brain myelin. SDS-PAGE of diabetic and normal CNS-M, like that of PNS-M, showed no differences in the pattern of protein bands or in the distribution of glycosylated adducts. The amount of incorporated radioactivity, however, was 3.18 times greater in the proteolipid region, 2.37 times greater for basic myelin protein, and 2.9 times greater for the high-molecular-weight proteins that did not enter the gel. This excessive nonenzymatic glycosylation of the main peripheral and central nervous system myelin components may contribute to the functional abnormalities of myelinated neurons associated with diabetes.

Animals↗
PubMed1983

Nonenzymatic glycosylation reduces the susceptibility of fibrin to degradation by plasmin.

The effect of nonenzymatic glycosylation on the susceptibility of fibrin to degradation by the specific fibrinolytic enzyme plasmin was evaluated using both a fibrin plate assay and a fluorogenic synthetic plasmin substrate assay. Data from both types of experiments demonstrate that nonenzymatic glycosylation reduces the susceptibility of fibrin to plasmin degradation. Acetylation and carbamylation have qualitatively similar effects, indicating that chemical modification of lysine amino groups is the underlying phenomenon responsible for the observed degradative defect produced by glucose. Experimental conditions that increased the rate of nonenzymatic protein glycosylation (higher monosaccharide concentration, glucose-6-phosphate) were associated with correspondingly greater degrees of resistance to degradation by plasmin. Such reduced degradation of nonenzymatically glycosylated proteins in vivo may contribute to the accumulation of fibrin and several other proteins observed in those tissues most frequently affected by the complications of diabetes.

Binding Sites↗
PubMed1982

Assessment of diabetic control by measurement of urinary glycopeptides.

The relationship between improvement in diabetic control and changes in levels of glycosylated urinary peptides was investigated. Eight poorly controlled Type 1 (insulin-dependent) diabetic patients were studied as optimal metabolic control was achieved. Mean daily blood glucose values and weekly haemoglobin A1 levels were determined simultaneously. Urinary glycosylated peptide levels fell 50% in 15 days, compared with 23 days for haemoglobin A1. Levels of glycosylated urinary peptides were sensitive to increased mean blood glucose concentrations of 9.72 mmol/l and increased linearly up to 20.0 mmol/l (r = 0.98) when compared with mean blood glucose levels obtained 8-9 days earlier. A similar correlation was found with haemoglobin A1 levels. Levels of glycosylated urinary peptides before and after optimal control were compared, and a decrease of 40% was observed (pre-control: 269 +/- 44 mumol/day, optimal control: 162 +/- 45 mumol/day, mean +/- SEM). The lag time between the fall in mean blood glucose level and the parallel fall in glycosylated urinary peptides was 8-9 days, suggesting that measurement of these compounds may become a useful clinical laboratory technique for monitoring short-term integrated glycaemia in diabetic patients.

Adolescent↗
PubMed1982

Potential antitrypanosomal agents. 1,N2-Disubstituted 2-amino-5-hydroxy-4-methylnaphtho[1,2-d]thiazolium salts and related compounds.

A series of 1-alkyl-2-(substituted-amino)-5-hydroxy-4-methylnaphtho[1,2-d]thiazoles having in vitro trypanocidal activity is described. Several caused complete lysis of Trypanosoma brucei organisms within 30 min at 10(-5) M. The presence of a hydrophobic substituent on the 2-amino group was associated with high antitrypanosomal activity. Some analogues unsubstituted at the 1-position, a known class of compounds, were also active. None of the derivatives significantly prolonged the survival of T. brucei infected mice. Inhibition of activity in vitro by bovine serum albumin was observed. Because of the structural novelty of these agents in comparison with known trypanocides, their mechanism of action warrants further investigation.

Animals↗
PubMed1982

Formation of covalent adducts between cortisol and 16 alpha-hydroxyestrone and protein: possible role in the pathogenesis of cortisol toxicity and systemic lupus erythematosus.

The incubation of albumin with cortisol or 16 alpha-hydroxyestrone results in the formation of covalent steroid-protein adducts. The rate of adduct formation increases in the presence of sodium cyanoborohydride (NaCNBH3), indicating that the reaction proceeds nonenzymatically through a Schiff base intermediate. Under nonreducing conditions, a stable adduct forms with cortisol and 16 alpha-hydroxyestrone but not with estrone, which lacks a hydroxyl group adjacent to the reactive carbonyl. It is hypothesized that a Heyns rearrangement involving the adjacent hydroxyl group traps the Schiff base and produces a stable ketoamine adduct. The binding of 16 alpha-hydroxyestrone and cortisol to albumin is significantly inhibited by acetylsalicylic acid, which has been shown to acetylate an epsilon-amino group of a lysine residue in albumin. High-pressure liquid chromatography analysis of an acid hydrolysate of 16 alpha-hydroxyestrone-albumin shows that a product containing 16 alpha-hydroxyestrone coelutes with a standard prepared by reacting 16 alpha-hydroxyestrone with the epsilon-amino group of lysine. We propose that the formation of covalent steroid-protein adducts is a generalized phenomenon which may contribute to the pathological effects produced by elevated levels of certain endogenous steroids.

Acetylation↗
PubMed1982

Lipoprotein lipase suppression in 3T3-L1 cells by an endotoxin-induced mediator from exudate cells.

Conditioned medium from cultures of mouse peritoneal exudate cells incubated wih endotoxin contains a mediator that markedly suppresses (greater than 90%) lipoprotein lipase (triacylglycero-protein acylhydrolase, EC 3.1.1.34) activity in differentiating 3T3-L1 mouse preadipocytes. The effect is dependent upon the amount of mediator and is evident as early as 30 min after the addition of the mediator-containing medium to 3T3-L1 cell cultures. Neither endotoxin nor conditioned medium from cultures of exudate cells not exposed to endotoxin shows the presence of the mediator. Lysates of the exudate cells are also unable to suppress the lipase activity. Increasing the amount of insulin does not reverse this suppression, even at 1000 times the concentration used for standard experiments. The lipoprotein lipase suppression mediator present in the conditioned medium of endotoxin-treated exudate cells is heat labile and has an apparent molecular weight of at least 12,000. The mediator does not inhibit lipoprotein lipase activity directly nor does it affect the half-life of enzyme activity released in the medium. The present study demonstrates that endotoxin promotes the release of a mediator from exudate cells that suppresses the activity of lipoprotein lipase in 3T3-L1 preadipocytes.

Adipose Tissue↗
PubMed1982

Protein binding of N-2-mercaptoethyl-1,3-diaminopropane via mixed disulfide formation after oral administration of WR 2721.

Earlier studies have shown that WR 2721 [H2N-(CH2)3-NH(CH2)2SPO3H2] is converted to its free thiol form, N-2-mercaptoethyl-1,3-diaminopropane (MDP), at the acidic pH of the stomach. MDP is a radioprotective compound and a mucolytic agent capable of decreasing sputum viscosity in the lungs of patients with cystic fibrosis. Conversion of WR 2721 and MDP to the corresponding sulfonic acid (MDP-SO3H) permits quantitative determination of these compounds in physiological fluids by use of an automatic amino acid analyzer. After oral administration of WR 2721 to human patients and rabbits it is converted to MDP and the free thiol form of the drug associates with plasma proteins by mixed disulfide linkage. The plasma proteins serve as a depot and reservoir of MDP for potential exchange at the tissues. When incubated with whole sputum or with purified mucin solutions in vitro, MDP decreased the viscosity of these solutions by reduction of the accessible disulfide bonds of the mucin molecule and was subsequently found in mixed disulfide association with the mucin molecule. The association of MDP with proteins via mixed disulfide linkage has important implications for the development of optimal dose regimens for administration of WR 2721 to patients.

Administration, Oral↗