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Biomedical subjects

L D Johnson

Publications and source records attributed to L D Johnson.

At least 73 records · Page 4Linked to original sources
PubMed1976

Isolation and characterization of an epithelial basement membrane glycoprotein from murine kidney and further characterization of an epithelial basement membrane glycoprotein secreted by murine teratocarcinoma cells in vitro.

A glycoprotein component of epithelial basement membranes (EBM) has been isolated from murine kidney homogenates by extraction with 0.05 M phosphate buffer, pH 7.2, precipitation with (NH4)2SO4 and chromatography on controlled pore glass. Antiserum produced against this glycoprotein reacts specifically with the basement membranes of renal glomeruli and tublules. The EBM glycoprotein of renal origin is antigenically identical with a glycoprotein component of epithelial basement membrane secreted by a murine teratocarcinoma grown in vitro, and the amino acid composition of the two EBM glycoproteins is markedly similar. Both glycoproteins were isolated as high molecular weight aggregates. Disaggregation with sodium dodecyl sulfate and 2-mercaptoethanol resulted in release of monomers of 32 000 and 34 000 daltons for kidney EBM glycoprotein and teratocarcinoma EBM glycoprotein, respectively. The difference in molecular weight is apparently due to increased amounts of fucose, mannose, N-acetylglucosamine and sialic acid in the glycoprotein secreted by the teratocarcinoma. In addition, both EBM glycoproteins contain galactose, glucose and N-acetylgalactosamine.

Amino Acids↗
PubMed1976

Automated gel permeation chromatographic cleanup of animal and plant extracts for pesticide residue determination.

Applications of an improved gel-solvent system for cleanup of pesticide residues by gel permeation chromatography (GPC) were investigated. Elution characteristics using Bio-Beads SX-3 gel and a toluene-ethyl acetate (1+3) elution solvent were determined for 16 nonionic chlorinated pesticides, 3 polychlorinated biphenyls (PCBs), 14 chlorophenoxy herbicide esters, and 7 organophosphate insecticides. Elution patterns for vegetable and animal lipids were also studied. Quantitative recoveries of the pesticides were achieved. No liquid-liquid partitioning cleanup steps were required with any type of nonionic chlorinated pesticide or sample matrix. Only GPC cleanup was required for the nonionic chlorinated pesticides, PCBs, and organophosphate pesticide residues in chicken and turkey fat samples. Electron capture and flame photometric detectors were used in the gas chromatographic method for the respective pesticides. Samples containing up to 0.5 g lipid each were processed at the rate of one every 30-40 min with the automated system. Results were in excellent agreement with those from accepted manual partitioning methods and were achieved with significant savings of both labor and chemicals.

Adipose Tissue↗
PubMed1975

The site of 5S RNA genes in human chromosome 1.

The major site of genes for human 5S RNA is in the long arm of chromosome 1. We find no evidence of sites in other chromosomes; if such exist, they are much smaller than the site in 1q.

Chromosome Mapping↗