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Biomedical subjects

R M Oliver

Publications and source records attributed to R M Oliver.

At least 37 records · Page 2Linked to original sources
PubMed1989

Branched-chain alpha-keto acid dehydrogenase complex from bovine kidney: radial distribution of mass determined from dark-field electron micrographs.

Scanning transmission electron microscopy (STEM) was used to determine the radial distribution of mass within the bovine kidney branched-chain alpha-keto acid dehydrogenase complex (E1-E2) and its core enzyme, dihydrolipoamide acyltransferase (E2). The particle mass of E2 measured by STEM is (1.19 +/- 0.02) x 10(6). Assuming 24 subunits per E2 core, this value corresponds to a subunit molecular weight of (4.96 +/- 0.08) x 10(4), which agrees well with the subunit molecular weight estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of 5.2 x 10(4) (Pettit et al., 1978) and that deduced from the gene sequence, 46,518 (Griffin et al., 1988). Thus, the STEM data reaffirms the 24-subunit model for this E2. Previous studies indicated that the E2 subunits contain an extended, outer lipoyl-bearing domain connected by a trypsin-sensitive segment to a compact, inner catalytic domain. The assemblage of 24 inner domains comprises a cubelike inner core. The quantity and spatial distribution of mass determined from STEM images for the E2 inner core are consistent with this model. The lipoyl-bearing domains are shown to occupy a zone defined by radii of 80-130 A over which the lipoyl moiety may range. This zone overlaps the positions of the 24 branched-chain alpha-keto acid dehydrogenase (E1) molecules, which apparently are located on the of the cubelike inner core.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗
PubMed1989

Hyperammonaemic coma in ureterosigmoid urinary diversion.

We report on a patient with ureterosigmoid anastomosis, who presented with recurrent episodes of confusion, agitation and aggressive behaviour, culminating in coma. Investigations revealed profound hyperammonaemia, which responded to treatment with sodium benzoate and sodium phenylacetate. No definite cause was found for the abnormality, apart from possible urinary tract infection. The patient remains well on a protein restricted diet with mildly elevated levels of plasma ammonia.

Amino Acids↗
PubMed1989

Renal and pulmonary effects of angiotensin converting enzyme inhibition in chronic hypoxic lung disease.

The effects of 28 days' treatment with captopril or with placebo on renal and pulmonary function were evaluated in nine patients with stable pulmonary heart disease. Captopril (25 mg twice daily) caused a 17% rise in effective renal plasma flow but no change in glomerular filtration rate, resulting in a fall in filtration fraction likely to favour natriuresis. Captopril did not alter FEV1, lung volumes, or arterial oxygen or carbon dioxide tension.

Aged↗
PubMed1988

Progressive apical pleural fibrosis: a 'constrictive' ventilatory defect.

We report two patients with bilateral apical pleural fibrosis which may be a form of benign asbestos-related pleurisy, one of these being steroid responsive. The pulmonary function defect of reduced lung volumes with raised gas transfer coefficient is characteristic and is best described as 'constrictive'.

Adult↗
PubMed1988

Cardiac tamponade due to pneumopericardium.

Pneumopericardium is rare in acute asthma and cardiac tamponade has not been reported. The case is reported of a 20 year old asthmatic patient in whom assisted ventilation and high airway pressures resulted in tension pneumopericardium with clinical signs of cardiac tamponade that were relieved by pericardial aspiration.

Acute Disease↗
PubMed1987

Mercury pulmonary emboli following intravenous self-injection.

The attempted intravenous injection of metallic mercury resulted in multiple mercury pulmonary emboli. Few of the abnormalities of respiratory or renal function reported previously were demonstrated. In particular the isotope ventilation/perfusion scan was unhelpful in confirming the diagnosis. Extravasation of mercury at the injection site produced a severe local inflammatory reaction and in the presence of toxic blood mercury levels surgical excision was undertaken. The blood mercury levels fell significantly but remain elevated within the toxic range to date. This may be due to the continued absorption of embolized mercury. The long-term effects of chronically elevated blood mercury levels is unknown.

Adult↗
PubMed1983

A computer model analysis of the active-site coupling mechanism in the pyruvate dehydrogenase multienzyme complex of Escherichia coli.

A computer modeling system developed to analyze experimental data for inactivation of the Escherichia coli alpha-ketoglutarate dehydrogenase complex (KGDC) accompanying release of lipoyl moieties by lipoamidase and by trypsin [Hackert, M.L., Oliver, R.M. & Reed, L.J. (1983) Proc. Natl. Acad. Sci. USA 80, 2226-2230] was used to analyze analogous data for the E. coli pyruvate dehydrogenase complex (PDC). The model studies indicate that the activity of PDC, as found for KGDC, is influenced by redundancies and random processes, which we describe as a multiple random coupling mechanism. In both complexes more than one lipoyl moiety services each pyruvate dehydrogenase (EC 1.2.4.1) or alpha-ketoglutarate dehydrogenase (EC 1.2.4.2) (E1) subunit, and an extensive lipoyl-lipoyl interaction network for exchange of electrons and possibly acyl groups must also be present. The best fit between computed and experimental data for PDC was obtained with a model that has four lipoyl domains with four or, more probably, eight lipoyl moieties servicing each E1 subunit. The lipoyl-lipoyl interaction network for PDC has lipoyl domain interactions similar to those found for KGDC plus the additional possibility of interaction of a lipoyl moiety and its paired mate on each dihydrolipoamide acetyltransferase (EC 2.3.1.12) (E2) subunit. The two lipoyl moieties on an E2 subunit in PDC appear to be functionally indistinguishable, each servicing the acetyltransferase site of that E2 subunit and a dihydrolipoamide dehydrogenase (EC 1.6.4.3) (E3) subunit if the latter is bound to that particular E2 subunit. The observed difference between inactivation of PDC by lipoamidase and by trypsin appears to be due to dead-end competitive inhibition by lipoyl domains that have been modified by excision of lipoyl moieties by lipoamidase.

Amidohydrolases↗
PubMed1983

Evidence for a multiple random coupling mechanism in the alpha-ketoglutarate dehydrogenase multienzyme complex of Escherichia coli: a computer model analysis.

A computer modeling system was used to analyze experimental data for inactivation of the Escherichia coli alpha-ketoglutarate dehydrogenase complex accompanying release of lipoic acid residues by lipoamidase and by trypsin [Stepp, L. R., Bleile, D. M., McRorie, D. K., Pettit, F. H. & Reed, L. J. (1981) Biochemistry 20, 4555-4560]. The results provide insight into the active-site coupling mechanism in the alpha-ketoglutarate dehydrogenase complex. The model studies indicate that the overall activity of the alpha-ketoglutarate dehydrogenase complex is influenced by redundancies and random processes that we describe as a multiple random coupling mechanism. More than one lipoyl moiety services each E1 subunit (alpha-ketoglutarate dehydrogenase, EC 1.2.4.2), and an extensive lipoyl-lipoyl interaction network for exchange of electrons and possibly acyl groups must also be present. The best fit between computed and experimental data was obtained with a model that has two lipoyl moieties servicing each E1 subunit and a lipoyl-lipoyl interaction network that links all lipoyl moieties on the E2 cube (dihydrolipoamide succinyltransferase, EC 2.3.1.61). The single lipoyl moiety on an E2 subunit is assumed to service the coenzyme A-dependent succinyltransferase site of that E2 subunit as well as an E3 subunit (dihydrolipoamide dehydrogenase, EC 1.6.4.3) if the latter is bound to that particular E2 subunit.

Acyltransferases↗
PubMed1981

Crystallization and subunit structure of histidine decarboxylase from Lactobacillus 30a.

Histidine decarboxylase from Lactobacillus 30a has been crystallized in a variety of forms which together indicate a revised subunit structure for the native particle. Octahedral crystals of the wild type enzyme obtained at room temperature from ammonium sulfate solutions in microdiffusion cells belong to tetragonal space group I4122 with a = b = 222 A and c = 107.5 A. Trigonal and hexagonal plates of prohistidine decarboxylase and activated proenzyme obtained at 4 degrees C from polyethyleneglycol solutions by vapor equilibration using the hanging drop technique belong to the trigonal space group P321 with a = b = 100 A and c = 164 A. The space group symmetries and unit cell contents of these crystals indicate 32 point group symmetry for the subunit structure of these enzymes. Sedimentation coefficients of wild type enzyme measured as a function of ionic strength at pH 7.0 indicate a rapid equilibrium between species varying from 6.9 S to 9.4 S. Sedimentation equilibrium analysis demonstrated the existence of a nearly homogeneous particle with Mr congruent to 208,000 at ionic strengths above I = 0.20, while an additional species of approximately one-half that molecular weight is observed at very ionic strengths (I = 0.2). At the pH optimum of the enzyme (pH 4.8), te larger species is dominant at all ionic strengths tested. Electron micrographs of native wild type enzyme show a dominant tetrahedral particle approximately 60 A on an edge while similar micrographs of enzyme cross-linked with glutaraldehyde show a dumbbell-shaped particle approximately 60 A in width and 120 A in length. These results establish that: (a) the native enzyme has a Mr congruent to 208,000 and a subunit composition (alpha beta)6; (b) the proenzyme has a subunit composition (pi)6; and (c) stable (alpha beta)3 and (pi) 3 particles exist under certain conditions.

Carboxy-Lyases↗
PubMed1979

Subunit structure of dihydrolipoyl transacetylase component of pyruvate dehydrogenase complex from Escherichia coli.

Limited tryptic digestion of the pyruvate dehydrogenase complex of Escherichia coli or its dihydrolipoyl transacetylase core cleaves the trypsin-sensitive transacetylase subunits into two large fragments, A (lipoyl domain) and D (subunit binding domain). Release of fragments A from the complex does not significantly affect its sedimentation coefficient or its appearance in the electron microscope. Fragment A contains the lipoyl moieties ((3)H-labeled), is acidic with an apparent isoelectric point of about 4.0, has a M(r) of 31,600 as determined by sedimentation equilibrium analysis, and has a swollen or extended structure (f/f(o) = 1.78). Fragment A exhibits anomalous properties, probably due to its acidic nature. It is resistant to staining with Coomassie blue and it migrates on sodium dodecyl sulfate/polyacrylamide gels as if it had a M(r) of 46,000-48,000. Further tryptic digestion converts fragment A into a lipoyl-containing fragment of M(r) 20,000 (fragment B) and eventually into an apparently stable product of estimated M(r) about 10,000 (fragment C). Fragment D has a compact structure of M(r) about 29,600 as determined by sedimentation equilibrium analysis in 6 M guanidinium chloride, and it possesses the intersubunit binding sites of the transacetylase, the binding sites for pyruvate dehydrogenase and dihydrolipoyl dehydrogenase, and the catalytic site for transacetylation. The assemblage of fragments D is responsible for the cube-like appearance of the transacetylase in the electron microscope. High-resolution electron micrographs of the transacetylase show fiber-like extensions, apparently corresponding to tryptic fragment A, surrounding the cube-like core.

Acetyltransferases↗