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Biomedical subjects

H T Wright

Publications and source records attributed to H T Wright.

At least 55 records · Page 3Linked to original sources
PubMed1984

Ovalbumin is an elastase substrate.

Ovalbumin is partially homologous in sequence with the proteinase inhibitors alpha 1-proteinase inhibitor and anti-thrombin III. The region of sequence in ovalbumin which corresponds to the reactive sites of these proteinase inhibitors is susceptible to attack by subtilisin, elastase, thermolysin, bromelain, and Bacillus cereus protease. The esterase activity of elastase is not inhibited by ovalbumin, but ovalbumin is efficiently cleaved by elastase. In contrast with these proteases, trypsin does not cleave ovalbumin.

Amino Acid Sequence↗
PubMed1984

A functional role for cysteine disulfides in the transmembrane transport of diphtheria toxin.

Diphtheria toxin was modified at one or both of its cysteine disulfide bridges by iodoacetamide, methylmethanethiosulfonate, and atomic mercury. The products of these reactions were characterized and tested for toxicity in vitro and in vivo. All were toxic in vitro, but had lost almost all cytotoxic activity toward HeLa cells. It was possible to show from in vivo protection experiments that modification of the cysteine disulfide in the B-chain interfered with cell surface binding, while modification of the cysteine disulfide linking the A and B domains inhibits a step subsequent to binding in the intoxication process. The latter finding supports a functional role for this interdomain cysteine disulfide in the membrane transport process.

Adenosine Diphosphate Ribose↗
PubMed1984

Thermal stability of different forms of diphtheria toxin.

Diphtheria toxin and its enzymatically active A fragment have been examined by differential scanning calorimetry. The thermal stability was measured for different forms of these molecules, including tryptically nicked and intact, nucleotide-bound and free, cysteine alkylated, and cysteine oxidized and reduced. Three ranges of denaturation temperature have been observed among the different forms of diphtheria toxin studied, and there is a correlation of the thermal stability of these different forms with their biological activity. At the concentrations used for measurement, all forms of the 62,000-Da diphtheria toxin are irreversibly denatured by heating to 100 degrees C, while free A chain is reversibly denatured. In vivo and in vitro activities of the samples were measured before and after heating, and all were found to retain significant degrees of activity after heating.

Diphtheria Toxin↗
PubMed1984

A method for covalent insertion of mercury into the cysteine disulfide bridges of proteins.

A method is described by which atomic mercury can be taken up by thiol groups and inserted into the disulfide bridges of proteins which can be reversibly reduced and denatured. The method utilizes tandem columns of Sephadex G-10 and Biogel P2. Protein samples are separated from reducing and denaturing agent on the Sephadex column and then react with mercury, which is bound to the Biogel P2 column. Of eight proteins tested, all took up mercury using this method. The amount of mercury incorporated by this method differed from that found using other methods and was closer to the stoichiometry of the disulfide bridges of the protein than these methods.

Chromatography, Gel↗
PubMed1981

Nalidixic acid, oxolinic acid, and novobiocin inhibit yeast glycyl- and leucyl-transfer RNA synthetases.

Nalidixic acid and novobiocin inhibit the aminoacylation and pyrophosphate exchange activities of glycyl- and leucyl-transfer RNA synthetases from bakers' yeast. Similar types of inhibition are observed for both enzymes, suggesting similar mechanisms. The potency of these inhibitors is comparable to that observed for their inhibition of in vivo DNA synthesis in eukaryotic cells.

Amino Acyl-tRNA Synthetases↗
PubMed1979

Meningococcal sepsis with endophthalmitis.

Endophthalmitis is a rare complication of meningococcemia. A child had endophthalmitis as the initially occurring complaint. Although both eyes appeared inflamed, the pupil in the right eye was fixed and dilated, the fundus could not be seen, and a hypopyon was seen in the right anterior chamber. There was gradual improvement when the child received antibiotic therapy. Since the introduction of antimicrobial drugs, endophthalmitis has rarely been observed as a complication of meningococcal disease. However, this report is evidence that meningococcemia may occur with unusual sites of local infection.

Child, Preschool↗
PubMed1978

Acute pericarditis associated with hepatitis B infection.

Patients infected with hepatitis B have demonstrated a wide spectrum of clinical manifestations other than hepatitis. Immune complex formation has been proposed as a possible mechanism for such varied disease presentations. The present report describes a case in which acute pericarditis is associated with hepatitis B surface antigen-positive disease. Speculations are made relating the pericardial changes to the formation of immune complexes following hepatitis B virus infection.

Acute Disease↗
PubMed1977

Secondary and conformational specificities of trypsin and chymotrypsin.

Specific and non-specific trypsin substrates of known structure have been examined for common features. This analysis suggests that trypsin has a specificity for a particular conformation near the scissile bond which I denote as a conformational specificity. This conformation is a bent left-handed helix at the third and fourth (P3 and P4) amino acid positions toward the amino terminus from the scissile bond which I denote as a conformational specificity. This conformation is a bent left-handed show a high frequency of proline and glycine at these positions consistent with the left-handed helical conformation. This apparent secondary specificity for a particular substrate residue other than that at the primary position is not related to the nature of the residues at the third and fourth positions. Rather, these residues determine the bend of left-handed helix which has the effect of exposing main chain hydrogen-bonding groups of the substrate peptide chain to hydrogen-bonding groups on the enzyme. Thus, the secondary specificity of trypsin is not sequence-specific, but is for peptide main chain in the third and fourth positions and is determined by the tertiary structure of the substrate. This hypothesis for conformational and secondary specificity in trypsin can be extended to chymotrypsin. It also provides a means for the regulation of certain processes in vivo catalyzed by other proteases.

Chymotrypsin↗
PubMed1977

HBs antigenemia in renal allograft recipients.

Serial HBs Ag determinations were performed on 98 renal allograft recipients with functioning grafts for 6 to 108 months, 85 of whom were followed from the initiation of dialysis. Twenty-six (27%) recipients had HBs antigenemia following transplantation. Thirteen (50%) of the 26 recipients were HBs Ag positive during the period of dialysis and 13 developed HBs antigenemia 1 to 44 months following transplantation. Seventeen (65%) of the 26 HBs Ag positive patients had hepatic dysfunction which was detected by biochemical surveillance and not associated with clinical symptomatology. There was no evidence of progressive hepatic insufficiency. HBs Ag persisted in 24 (92%) recipients for 6 to 49 months. Clearing of antigenemia occurred in only two patients, both of whom ultimately rejected their grafts. The presence of HBs Ag had no adverse effect on graft function. Temporary reduction in azathioprine dosage with hepatic dysfunction was not associated with rejection episodes. The major hazard posed by the HBs Ag positive recipient is the potential reservoir for spread to the general population because of the persistence of antigenemia.

Alanine Transaminase↗
PubMed1975

Hepatitis B in a pediatric hemodialysis unit.

Serial HB Ag determinations were obtained on 62 children undergoing hemodialysis during a 31/2-year period. Thirty six (58%) of the patients had atleast one positive HB Ag determination (titer larger than 1:8) either during the period of dialysis or within 2 months after transplantation. Of the children who became HB Ag positive during the period of dialysis, 89% demonstrated hepatitis B antigenemia during the initial 6 months of dialysis. Becuase of the temporal relationship between the development of HB Ag positivity and the duration of dialysis, contamination of equipment was proposed as a contributing source for transmission of HB Ag. Although 67% of the patients who were HB Ag positive during dialysis developed biochemical evidence of hepatic dysfunction, only two patients had clinical manifestations. The incidence of hepatic involvement appeared to be related to age; only one of nine children less than 12 years of age had evidence of hepatic disease. Intermittent persistence of HB Ag for periods larger than 3 years was observed. Both the incidence and persistence of HB Ag indicate the need to prevent its acquisition by pediatric patients undergoing hemodialysis.

Adolescent↗