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Biomedical subjects

I Hopkins

Publications and source records attributed to I Hopkins.

9 recordsLinked to original sources
PubMed1990

A case of Krabbe's leukodystrophy without globoid cells.

Krabbe's globoid cell leukodystrophy is a rare hereditary progressive neurological disease of infants, in which there is deficient activity of galactosylceramide beta-galactosidase. The pathological hallmark is the presence of multinucleated globoid cells in the white matter associated with severe myelin depletion and gliosis. We report a second case where galactosylceramide beta-galactosidase deficiency was proven but no globoid cells were found in the brain. Symptoms began within the first 10 months of life and a deficiency of galactosylceramide beta-galactosidase activity was demonstrated in peripheral blood leukocytes and skin fibroblasts. The child survived till 8 yrs 7 mths. The reason for the absence of globoid cells is not clear but may be related to different effects of the gene mutation on the four substrates or possibly the interaction of sphingolipid activator protein-2.

Brain↗
PubMed1988

Capsule loss in H. influenzae type b occurs by recombination-mediated disruption of a gene essential for polysaccharide export.

The capsulation locus cap in H. influenzae type b contains directly repeated segments of DNA flanking a bridge region. Here we show that this bridge region contains a gene, bexA, encoding a 24.7 kd protein essential for export of capsular polysaccharide. bexA is disrupted, with loss of part of its coding sequence, in the spontaneous reduction of the duplicated cap locus to single-copy that accompanies loss of capsule expression. The predicted amino acid sequence of BexA aligns significantly with that of MalK from E. coli and with HisP and OppD of S. typhimurium. Thus, polysaccharide export might occur via an energy-dependent transporter with similarities to those identified for the import of various substrates into Gram-negative bacteria, BexA being the "energizer" of the transporter.

Amino Acid Sequence↗
PubMed1969

Sodium-stimulated transport of glutamate in Escherichia coli.

Wild-type Escherichia coli B grew poorly on glutamate as the sole carbon source, except at very high concentrations of the amino acid. The addition of sodium ion markedly stimulated the growth. It had the same effect in a mutant of E. coli B selected for the ability to grow at low glutamate concentrations. Sodium ion also potentiated growth inhibition by analogues of glutamate. The uptake of glutamate by nongrowing cells of the mutant was markedly stimulated by sodium ion in the presence of an energy source, chloramphenicol, and arsenite, which retarded glutamate degradation.

Ammonia↗