PubMed Health⌕ Search

Biomedical subjects

O N Johnson

Publications and source records attributed to O N Johnson.

11 recordsLinked to original sources
PubMed1995

beta-1,4-N-Acetylgalactosaminyltransferase involved in ganglioside synthesis: cDNA sequence, expression, and chromosome mapping of the mouse gene.

beta-1,4-N-Acetylgalactosaminyltransferase (EC 2.4.1.92; GalNAc-T) is a glycosyltransferase involved in the synthesis of gangliosides GM2 and GD2 as well as glycolipid GA2. We have isolated and sequenced the mouse Gal-NAc-T cDNA, studied GalNAc-T mRNA expression in adult tissues and in embryos, and determined the chromosomal location of the GalNAc-T gene, Ggm2. In comparison with the human cDNA, the mouse sequence was 83 and 87% identical at the nucleic acid and amino acid levels, respectively. The GalNAc-T transcript was most abundantly expressed in brain, liver, lung, spleen, and testis among the eight adult tissues examined. Relatively high levels of expression were seen early in mouse development (7-day embryos) compared to later times (11, 15, and 17 days). The Ggm2 gene was mapped to a distal position on mouse chromosome 10 that is homologous to a portion of human chromosome 12.

Amino Acid Sequence↗
PubMed1994

Structure and expression of the mouse beta-hexosaminidase genes, Hexa and Hexb.

Two genes, HEXA and HEXB, encode the alpha- and beta-subunits, respectively, of human beta-hexosaminidase. In the mouse, the corresponding genes are termed Hexa and Hexb. The subunits dimerize to yield three isozymes, beta-hexosaminidase A (alpha beta), B (beta beta), and S (alpha alpha), that have the capacity to degrade a variety of substrates containing beta-linked N-acetylglucosamine and N-acetylgalactosamine residues. Mutations in the HEXA or HEXB gene resulting in a beta-hexosaminidase deficiency cause Tay-Sachs or Sandhoff disease, respectively. As a prelude to the creation of mouse models of these lysosomal storage diseases, we have characterized the molecular biology of the mouse beta-hexosaminidase system. Protein sequences derived from the cloned Hexa and Hexb cDNAs were 55% identical to each other and were also very similar to the cognate human sequences: 84% sequence identity with human HEXA and 75% with HEXB. The mouse hexosaminidase subunits, when expressed in HeLa cells from the cDNAs, displayed specificity toward synthetic substrates similar to the human subunits. The Hexa and Hexb genes were 25 and 22 kb in length, respectively. Each gene was divided into 14 exons, with the positions of introns precisely matching those of the corresponding human genes. The 5' flanking regions of the mouse genes demonstrated promoter activity as ascertained by their ability to drive chloramphenicol acetyltransferase gene expression in transfected NIH 3T3 cells. The sequences of these regulatory regions were G+C-rich in the 200 bp upstream of the respective initiator ATGs. Several putative promoter elements were present, including Sp1, AP2, CAAT, and TATA motifs.(ABSTRACT TRUNCATED AT 250 WORDS)

3T3 Cells↗
PubMed1994

The mouse gene encoding the GM2 activator protein (Gm2a): cDNA sequence, expression, and chromosome mapping.

The GM2 activator protein forms a substrate-complex with GM2 ganglioside, which enables degradation of the ganglioside by beta-hexosaminidase A. Mutations in the human GM2 activator protein gene (GM2A) result in the GM2 gangliosidosis AB variant, a severe neurological disease. We have isolated and sequenced a mouse GM2 activator protein (Gm2a) cDNA with complete protein coding and 3' untranslated regions. Expression of the Gm2a transcript (approximately 2.3 kb) was apparent in all tissues examined and was most abundant in kidney and testis. The Gm2a gene was mapped to a region on mouse chromosome (Chr) 11 that is homologous with a segment of human chromosome 5 containing the orthologous human gene. In addition, a Gm2a-related sequence (Gm2a-rs1) was mapped to mouse Chr 5.

Animals↗
PubMed1977

What the federal x-ray regulations mean to the dentist.

The dentists should keep in mind that the Federal Performance Standard is designed to protect the public and the profession from health hazards and from inadequacies in manufacture. It offers many advantages to the dentist who uses X-ray equipment. The standard does not regulate the dentist's diagnostic use of X radiation, but it assures him of purchasing reliable, properly functioning equipment with an increased level of radiation protection.

Dentists↗
PubMed1976

A study to develop a rating system and evaluate dental radiographs submitted to a third party carrier.

An easy, efficient system for rating radiographs was developed and applied to 1,000 preauthorization case submissions. The films were evaluated and the frequency distribution of errors determined. Results showed the majority of the examined full-mouth and partial-mouth radiograph series submitted to Pennsylvania Blue Shield were substandard. Recommendations for screening radiographs to upgrade their technical quality are offered.

Blue Cross Blue Shield Insurance Plans↗