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Biomedical subjects

G L Jones

Publications and source records attributed to G L Jones.

At least 91 records · Page 5Linked to original sources
PubMed1983

A chemical and enzymological account of the multiple forms of human liver aldehyde dehydrogenase. Implications for ethnic differences in alcohol metabolism.

Three major low-pI zones of aldehyde dehydrogenase (aldehyde:NAD+ oxidoreductase, EC 1.2.1.3) may be visualized with specific histochemical staining after starch gel electrophoresis at pH 7.4 of Caucasian human liver extracts, whereas about 50% of Chinese human liver extracts show only two such zones. The three zones of activity were purified to apparent homogeneity from Caucasian liver. The substrate specificity of each form was investigated by double reciprocal plots using 13 aldehydes of various chemistries. The acetaldehyde-preferring isozyme I lacking in 50% of Chinese livers had a slightly lower native and subunit molecular weight than the "universal' isozymes IIa and IIb. All forms were highly sensitive to disulfiram inhibition. This inhibition could be protected against, or reversed, by dithiothreitol. 2,2'-Dithiodipyridine was a slower inhibitor of isoenzyme I. All three purified forms of the enzyme, as well as crude extracts of normal and isozyme I-deficient Chinese livers, showed positive immunoreactivity to antibodies prepared in rabbits against type I enzyme. Tryptic peptide maps of forms IIa and IIb were almost identical, whereas that of form I, although showing some similarities, was clearly different. These results provide a consistent explanation for the acetaldehyde-mediated extreme sensitivity to moderate alcohol ingestion shown normally by about 50% of oriental subjects and during disulfiram (Antabuse) therapy by all subjects.

Aldehyde Dehydrogenase↗
PubMed1983

Optimized procedures for investigating changes in human erythrocyte membrane proteins using treatment with calcium and various proteases.

In order to establish reproducible sensitive techniques for investigating diseases in which membrane defects have been implicated, human red cell membrane proteins were studied by SDS electrophoresis in ghosts prepared from the blood of 35 separate adult donors using treatment with 1 mmol/l calcium and proteolytic dissection under standardized conditions. The effects of calcium were consistent with increased binding of cytosolic proteins in membranes from fresh blood and endogenous proteolysis in membranes from aged blood. Exogenous proteolysis was most effective with trypsin and was facilitated both by pre-binding this protease to the membrane and by inclusion of 1 mmol/l Ca2+. The nature and extent of these effects was highly dependent on the storage time of the blood. Preliminary indications of cleavage fragment length polymorphism was obtained after treatment with the S. aureus V8 protease but not after trypsin or alpha chymotrypsin treatment.

Calcium↗
PubMed1983

A chemical and enzymological comparison of the common major human erythrocyte carbonic anhydrase II, its minor component, and a new genetic variant, CA II Melbourne (237 Pro leads to His).

A new variant of human erythrocyte carbonic anhydrase II (CA II) was discovered in a single Caucasian family during routine screening of blood samples from Melbourne, Australia. The normal and variant enzymes in the heterozygous CA II mixture, as well as a minor component of the normal enzyme, were resolved by isoelectric focusing following purification by a specific affinity matrix. Specific esterase activities of all three were very similar, but quite different Michaelis-Menten constants were noted for the minor component. No differences were noted with respect to inhibition by acetazolamide, but the minor component was more sensitive to chloride inhibition. Double diffusion analysis showed the immunological identity of the normal, variant, and minor components. Both the variant CA II and the minor component were less heat stable than the normal enzyme, but all forms showed identical rates of inactivation upon dialysis against the zinc chelator pyridine dicarboxylic acid. Amino acid analyses of the whole protein and the single difference peptide were consistent with a proline to histidine substitution in the variant. This was identified as 237 Pro leads to His by a process of elimination involving direct sequencing of tryptic and cyanogen bromide peptides. The numbering is by homology with the human CA I sequence.

Adult↗
PubMed1983

Discrepant in vitro versus in vivo interaction of M-positive donor red cells with IgG1 anti-M.

Following massive transfusion and a suspected sepsis, a patient produced a potent, high titer IgG1 anti-M alloantibody reactive at 37 degrees C with an indirect antiglobulin test [IAT] titer using anti-IgG of 1:512 versus MM red blood cells (RBC). During pretransfusion tests, the antibody was strongly reactive with M+ RBC using IAT, however, transfused M+ RBC remained in circulation and demonstrated normal red cell survival. The direct antiglobulin test remained negative and no antibody activity was detectable in eluates prepared at various times from red cells obtained from the patient post transfusion. There was no direct agglutination of red cells obtained from the patient post transfusion with autologous serum, even at 4 degrees C. However, these samples contained donor M+ RBC as determined by tests using various examples of human and rabbit anti-M antisera. The extraordinary findings of transfused M+ RBC, highly incompatible pretransfusion using IAT, coexisting with potent warm reactive anti-M antibody without evidence of in vivo antibody-antigen interaction represents an unusual discrepancy. Although the explanation for these findings remains unclear, it may indicate antigen modification of donor red cells in vivo.

Binding Sites, Antibody↗
PubMed1982

Purification, properties, partial sequence and evolutionary relationships of marsupial erythrocyte carbonic anhydrase.

Carbonic anhydrase (EC 4.2.1.1) has been purified from the erythrocytes of the tammar wallaby (Macropus eugenii desmarest). The enzyme was separated into four zones of activity. The three major individual forms were isolated as discrete entities. Comparison of substrate specificity, specific activities, kinetic constants and inhibition characteristics indicated that these heteromorphs represented minor post-translational modifications of a single gene product of carbonic anhydrase II type. Double-immunodiffusion and peptide mapping confirmed this proposition. The marsupial enzyme exists as a monomer with a molecular weight of about 29 000 containing one atom of zinc per mole which is much more tightly bound to the enzyme than it is in either human carbonic anhydrase I or II. The wallaby enzyme was, like human carbonic anhydrase II, partially inactivated by p-hydroxymercuribenzoate under conditions not inhibitory for human carbonic anhydrase I. The partial sequence of 51 residues of cyanogen-bromide peptides was sufficiently homologous to allow unambiguous overlap with the sequence of both human carbonic anhydrase I and II isozymes as well as with the recently published sequence of an apparent type I-like enzyme from the turtle. It is clear that the single wallaby erythrocyte carbonic anhydrase belongs to the class of separately evolving type II isozymes which have previously been defined only for placental mammals.

Acetazolamide↗
PubMed1982

The effects of clofibrate and 3-amino-1,2,4-triazole on liver catalase and lipid metabolism in mice.

Clofibrate-treated mice showed a significant decrease in plasma triacylglycerols and a parallel elevation of liver catalase. Repeated administration of aminotriazole to clofibrate-treated mice effectively abolished the elevated catalase activity, but had no significant effect on the reduced plasma triacylglycerol levels. In mice, the hypolipidemic effect of clofibrate may be dissociated from its capacity to elevate liver catalase. Repeated administration of aminotriazole to control mice resulted in significantly lowered carcass fat and plasma triacylglycerol levels even though the liver catalase activity was greatly depressed. The livers of clofibrate-treated mice showed an increase in phospholipid content. Livers of aminotriazole-treated mice showed a decrease in total lipid content, with a profound decrease in free fatty acids and triacylglycerols and a slight increase in phospholipids. The composition of the individual free fatty acids of the liver triacylglycerols showed a shift towards the shorter fatty acids and the nutritionally essential alpha-linolenic acid in clofibrate-treated mice.

Amitrole↗
PubMed1982

A polymorphic variant of human erythrocyte carbonic anhydrase I with a widespread distribution in Australian aborigines, CAI Australia-9 (8 Asp leads to Gly): purification, properties, amino acid substitution, and possible physiological significance of the variant enzyme.

Carbonic anhydrase I (EC 4.2.1.1) purified from the pooled packed red blood cells of 100 individuals typed as heterozygous for the common Australian Aboriginal carbonic anhydrase I variant CAI Australia-9 had a slightly higher specific CO2 hydratase or esterase (toward p-nitrophenyl acetate) activity than the normal component and a higher Km and Vmax using the esterase substrate. The variant enzyme was slightly more resistant to heat inactivation. The extent of inhibition of both enzymes by the specific inhibitor acetazolamide was identical, as was their immunological behavior and the lability of the active-site zinc ion. The variant enzyme was more resistant to chloride inhibition. The physiological importance of this observation is discussed in the context of a proposed adaptive advantage of the variant gene in the arid western and central regions of Australia. The amino acid substitution in the Aboriginal variant of a glycine for an aspartic acid residue has been located at residue 8 from the N terminus (i.e., 8 Asp leads to Gly), by proteolytic and partial acid hydrolyses. The possible effects of this substitution on the structure and function of the molecule are discussed.

Amino Acid Sequence↗
PubMed1982

Chemical and enzymological characterization of an Indonesian variant of human erythrocyte carbonic anhydrase II, CAII Jogjakarta (17 Lys leads to Glu).

A new variant of human erythrocyte carbonic anhydrase II (CAII) was discovered in a single heterozygous individual during routine screening of blood samples from the island of Java in Indonesia. The normal and variant components of the heterozygous CAII mixture were resolved by isoelectric focusing following purification by a specific affinity matrix. Specific esterase activities and Michaelis-Menten constants were identical. Only very small differences were noted with respect to inhibition by acetazolamide and chloride. Double diffusion analysis showed the immunological identify of the normal and variant enzymes. The variant CAII was considerably less heat stable than the normal enzyme. The variant was slightly more stable than the normal enzyme upon dialysis against the zinc chelator dipicolinic acid (PDCA), indicating a tighter binding of zinc than the normal enzyme. Analysis of tryptic peptides from the normal and variant enzymes indicated that, in the variant, lysine at position 17 from the N terminus had changed to glutamic acid. The differences in physiochemical properties observed for the normal and variant enzyme are discussed in relation to the possible effects of this substitution on the structure of the CAII molecule.

Amino Acid Sequence↗
PubMed1981

Comparison of anticonvulsant potencies of cyheptamide, carbamazepine, and phenytoin.

Carbamazepine and cyheptamide have certain stereochemical features in common with phenytoin; when superimposed, two bulky hydrophobic groups in each permit the approximate apposition of two electron donor atoms. The anticonvulsant activity of each compound was determined in mice using a standard maximal electroshock procedure, and the relative potencies are expressed in terms of the blood and brain concentrations as well as the intraperitoneal dosage. Although cyheptamide was much less potent than carbamazepine or phenytoin on the basis of intraperitoneal dosage, the difference in potency was much less when blood or brain concentrations were compared. These data should be of value for quantitative structure-activity relationship studies.

Animals↗
PubMed1980

Changes in lysosomal cathepsins during liver regeneration.

The effect of 2/3 hepatectomy in the adult rat on the specific and total activities of two lysosomal endopeptidases, cathepsins B1 and D, has been examined. The specific activity of both enzymes fell rapidly following hepatectomy when compared to paired, sham-operated controls. When changes in total protein were compared to changes in cathepsins B1 and D, all three decreased in a parallel fashion for the first 18 h. At 24 h, total liver protein increased rapidly while cathepsins B1 and D continued to decrease. Cathepsin B1 fell to a level of 12% of non-operated control levels at 36 h, while total protein was already back to 40% of control levels. In contrast to the decreases in the activities of the cathepsins, there was an increase in the activities of lactate dehydrogenase and malate dehydrogenase during the first two days of regeneration. The clear lag in replacement of the cathepsins relative to other liver proteins following partial hepatectomy suggests that cathepsin activity is selectively controlled and that lowering the levels of cathepsins B1 and D may play an important role in the decreased degradation of protein seen during the early phases of liver regeneration.

Animals↗
PubMed1980

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