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Biomedical subjects

K Carpenter

Publications and source records attributed to K Carpenter.

53 records · Page 3Linked to original sources
PubMed1992

Human liver long-chain 3-hydroxyacyl-coenzyme A dehydrogenase is a multifunctional membrane-bound beta-oxidation enzyme of mitochondria.

We have purified to homogeneity the long-chain specific 3-hydroxyacyl-CoA dehydrogenase from mitochondrial membranes of human infant liver. The enzyme is composed of non-identical subunits of 71 kDa and 47 kDa within a native structure of 230 kDa. The pure enzyme is active with 3-ketohexanoyl-CoA and gives maximum activity with 3-ketoacyl-CoA substrates of C10 to C16 acyl-chain length but is inactive with acetoacetyl-CoA. In addition to 3-hydroxyacyl-CoA dehydrogenase activity, the enzyme possesses 2-enoyl-CoA hydratase and 3-ketoacyl-CoA thiolase activities which cannot be separated from the dehydrogenase. None of these enzymes show activity with C4 substrates but all are active with C6 and longer acyl-chain length substrates. They are thus distinct from any described previously. This human liver mitochondrial membrane-bound enzyme catalyses the conversion of medium- and long-chain 2-enoyl-CoA compounds to: 1) 3-ketoacyl-CoA in the presence of NAD alone and 2) to acetyl-CoA (plus the corresponding acyl-CoA derivatives) in the presence of NAD and CoASH. It is therefore a multifunctional enzyme, resembling the beta-oxidation enzyme of E. coli, but unique in its membrane location and substrate specificity. We propose that its existence explains the repeated failure to detect any intermediates of mitochondrial beta-oxidation.

Acyl-CoA Dehydrogenase, Long-Chain↗
PubMed1992

Differential diagnosis of hydroxydicarboxylic aciduria based on release of 3H2O from [9,10-3H]myristic and [9,10-3H]palmitic acids by intact cultured fibroblasts.

Intact cultured fibroblasts from patients with deficiency of long-chain 3-hydroxyacyl-CoA dehydrogenase release 3H2O from [9,10-3H]myristic acid and [9,10-3H]palmitic acid more slowly than normal. The ratio of activity (palmitate/myristate) is also low and the expression (rate with palmitate2/(rate with myristate) gives good differentiation between affected and unaffected cells. In some patients who have shown hydroxydicarboxylic aciduria when unwell there is reduced 3H2O production from [9,10-3H]myristic and [9,10-3H]palmitic acids by intact cultured fibroblasts but normal 3-hydroxyacyl-CoA dehydrogenase activities in disrupted cells. The palmitate/myristate ratio is higher than in long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency. The basic defect in these patients is still unknown but it is suggested that caution be used over the administration of medium-chain triglyceride.

3-Hydroxyacyl CoA Dehydrogenases↗
PubMed1992

Synthesis and transport of GAP-43 in entorhinal cortex neurons and perforant pathway during lesion-induced sprouting and reactive synaptogenesis.

Metabolic labeling and quantitative 2D gel autoradiography were used to assess changes in the synthesis and transport of GAP-43 in entorhinal cortex (EC) neurons and perforant pathway during lesion-induced sprouting and reactive synaptogenesis. In normal adult rats, there is a high constitutive level of GAP-43 synthesis and transport in EC neurons projecting to the hippocampus. Following unilateral EC lesions, there is a 2-fold (100%) increase in the transport of newly synthesized GAP-43 to the contralateral or 'sprouting' hippocampus. The timing of this upregulation (between 6 and 15 days) suggests that changes in GAP-43 expression occur in response to the growth of presynaptic terminals during sprouting.

Animals↗
PubMed1991

Later rather than sooner: extralinguistic categories in the acquisition of Thai classifiers.

An experimental elicitation task with children between the ages of 1;8 and 11;3 shows that children learning Thai numerical classifiers begin with purely distributional information: specifically, (1) that classifiers must appear in the post-numeral position, and (2) that classifiers comprise a conventional, closed set of words. Semantic organizing features, such as salient features of the head noun's referent, appear later than these syntagmatic organizing features. Use of such semantic information is not an immature 'first guess' at grammatical categories, but rather, a necessary component of adult linguistic competence, because the categories are productive both for older children and for adults.

Child↗
PubMed1991

Anterograde amnesia with fornix damage following removal of IIIrd ventricle colloid cyst.

Two patients developed anterograde amnesia following the apparently uncomplicated transcallosal-transventricular removal of a colloid cyst. Damage to the fornical columns was demonstrated on CT and MRI scans, whilst other memory related structures were entirely normal. Longitudinal neuropsychological evaluation, over 12-24 months, has revealed a very similar pattern of deficit in the two cases: verbal memory has remained persistently impaired whilst nonverbal anterograde memory has improved to some degree. Formal tests of remote public (famous faces and events) and personal autobiographical memory have supported the clinical impression that neither patient has a temporally extensive retrograde amnesia. These findings address the role of the fornix, and the dissociation of memory processes in humans.

Adult↗
PubMed1983

Generation and characterization of monoclonal antibodies reactive with human B lymphocytes.

Four novel monoclonal antibodies directed at determinants on human B lymphocytes were produced and characterized by flow cytometry using indirect immunofluorescence analysis. The antibodies, OKB1, OKB2, OKB4, and OKB7, define antigens not previously described on human B lymphocytes using B cell reactive monoclonal antibodies or standard B cell phenotypic markers. OKB4 [immunoglobulin M (IgM)] and OKB7 (IgG2a) were reactive with greater than 95% of all surface membrane immunoglobulin positive (Smlg+) lymphocytes and were restricted to the B cell lineage. OKB2 (IgG1) likewise reacted with greater than 95% of all Smlg+ lymphocytes; however, the antigen was also expressed on all granulocytes. In contrast to OKB2, OKB4, and OKB7, OKB1 reacted with a variable percentage of normal peripheral B cells (approximately 70 to 95%). Functional studies employing polyclonally activated B cells in a pokeweed mitogen (PWM) driven system and the reverse hemolytic plaque assay for the quantitation of Ig secreting plasma cells demonstrated that OKB1 and OKB2 inhibited the generation of plaque-forming cells (PFC) when added to cultures at day 0. OKB4 had a marginal inhibitory effect, whereas OKB7 consistently enhanced the PFC response. Immunoprecipitation studies with OKB1, OKB4, and OKB7 demonstrated that these antibodies precipitated antigens of approximately 168,000, 87,000, and 175,000 m.w., respectively. The OKB2 antigen is presently under study.

Animals↗