Biomedical subjects

H L Ley

Publications and source records attributed to H L Ley.

11 recordsLinked to original sources

PubMed1995

Linear chromosomes of Lyme disease agent spirochetes: genetic diversity and conservation of gene order.

We have constructed physical and genetic maps of the chromosomes of 21 Lyme disease agent spirochetes from geographically diverse locations. All have linear chromosomes whose lengths range from 935 to 955 kbp, and all contain multiple linear plasmids in the 16- to 175-kbp size range. The locations of 11 gene clusters on the chromosomes of these different isolates are indistinguishable at the resolution achieved in this study, indicating that the members of this related group of species have highly conserved chromosomal gene orders. However, chromosomal restriction endonuclease cleavage site maps are unique for nearly all isolates. The 22 chromosomal maps currently available define eight classes of Lyme disease agents. Four of these correspond to the previously proposed species Borrelia burgdorferi, Borrelia garinii, Borrelia afzelii, and Borrelia japonica. In addition, the North American isolates 21038, DN127 c19-2, 25015, and CA55 typify four additional chromosomal types that are as phylogenetically distinct as the species listed above. These findings support the idea that comparison of restriction maps is currently the most robust and definitive method for determining overall chromosomal relationships among closely related bacteria. In the course of this work, we located on the chromosome the previously unmapped outer surface protein-encoding LA7 gene and genes homologous to the Escherichia coli priA, plsC, parE, and parC genes, and we have substantially refined the locations of the recA, fla, p22A, and flgE genes.

Animals↗

PubMed1983

Isolation and characterization of hepatic metallothionein from rainbow trout (Salmo gairdneri).

1. A low molecular weight (7,700) Zn- and Cu-containing protein was isolated from the livers of Zn-injected rainbow trout by gel filtration and ion exchange chromatography. Purity of the isolated protein was assessed by native and denaturing polyacrylamide gel electrophoresis and isoelectric focusing. 2. The purified protein was positively identified as a metallothionein on the basis of its molecular size, high metal content (3.6 g atoms Zn and 2.6 g atoms Cu per mole; 5.2% metal), heat stability, u.v. absorption spectrum, charge and amino acid composition (25% cysteine, no histidine and tryptophan, and trace tyrosine and phenylalanine). 3. The relatively high Cu content of this protein was unexpected and may be attributed to the presence of high levels of Cu, as Cu-thionein, in the livers of non-injected fish. 4. The comparative differences in the metal content of hepatic MT in trout and other animals are discussed.

Amino Acids↗

PubMed1970

Efficacy of pre-1962 drugs.

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Drug Industry↗

PubMed1970

Bladder tumors in rats fed cyclohexylamine or high doses of a mixture of cyclamate and saccharin.

Papillary transitional cell tumors were found in the urinary bladders in 8 rats out of 80 that received 2600 milligrams per kilogram of body weight per day of a mixture of sodium cyclamate and sodium saccharin (10:1) for up to 105 weeks. From week 79 on, several of these rats received cyclohexylamine hydrochloride (125 milligrams per kilogram per day, the molecular equivalent of the conversion of about 10 percent of the cyclamate dosage to cyclohexylamine) in addition to the sodium cyclamate and sodium saccharin. In another study in which 50 rats were fed daily 15 milligrams of cyclohexylamine sulfate per kilogram of body weight for 2 years, eight males and nine females survived. One of the eight males had a tumor of the urinary bladder. In neither study were bladder tumors found in the control rats or in rats treated with lower doses of the compounds.

Amines↗

PubMed1970