Search PubMed⌕ Search

Biomedical subjects

J D Baxter

Publications and source records attributed to J D Baxter.

At least 163 records · Page 9Linked to original sources
PubMed1984

Creatine kinase protein sequence encoded by a cDNA made from Torpedo californica electric organ mRNA.

Creatine kinase (ATP creatine N-phosphotransferase, EC 2.7.3.2) is important in the maintenance of ATP levels in high energy-requiring tissues such as muscle and brain. A complete understanding of its function requires knowledge of its amino acid sequence. To obtain cDNA clones encoding creatine kinase sequences, a cDNA bank was constructed using mRNA from the electric organ of Torpedo californica and was screened by comparing differential colony hybridization of electric organ and liver-derived 32P-labeled cDNAs. Cloned DNAs have been isolated that can arrest the abundant synthesis of Mr 40,000-43,000 material seen after in vitro translation of electric organ mRNA. One of the clones, CK52g8, was sequenced by the dideoxy M13 method and was found to encode a Mr 42,941 protein, which is 68% homologous to a known partial sequence of rabbit muscle creatine kinase and which has a composition similar to creatine kinases from chicken and rabbit tissues. By contrast, no significant homology was found with the known sequences of kinases that use other substrates. RNA blot hybridization analysis indicated that CK52g8 is complementary to a 1600-base-pair mRNA. Primer extension analysis indicated that CK52g8 is only 5 nucleotides short of a full-length cDNA, implying that it encodes a complete protein sequence. The availability of this complete sequence should be useful in further studies of creatine kinase structure and function using techniques such as site-specific mutagenesis.

Amino Acid Sequence↗
PubMed1984

Primary structure of the human renin gene.

The gene encoding human renin has been isolated on two overlapping clones from a bacteriophage lambda library of human DNA. The entire gene spans about 12,000 bp and contains 10 exons separated by 9 intervening sequences. The gene structure is similar to that of human pepsinogen in terms of overall size, homology in the coding regions, position of introns, and sizes of the exons, suggesting that the two genes are evolutionarily related. However, a novel exon coding for only three amino acids was detected that is not present in the pepsinogen gene and whose amino acids are also not found in mouse renin. Although the nucleotide sequence of the 5'-flanking DNA differs from that of the pepsinogen gene, in both cases this region contains a structure of almost perfect dyad symmetry which immediately precedes the TATA box and may have functional importance. Furthermore, sequences resembling the putative consensus sequence for glucocorticoid regulation of gene expression are located approximately 200 and 300 bp upstream from the gene. The overall structural anatomy suggests that the human renin gene evolved by mechanisms that include a duplication of exon segments, particularly those containing the codons for the catalytically important aspartate residues, together with the insertion of other exon and flanking DNA structures. An analysis of human chromosomal DNA demonstrates that there is only one gene with high homology to human renin.

Base Sequence↗
PubMed1984

Expression and hormonal regulation of the rat growth hormone gene in transfected mouse L cells.

Expression of the rat growth hormone (rGH) gene in the pituitary and in cultured pituitary tumor cells is regulated by glucocorticoid hormones. After co-transfer of cloned DNA containing the rGH gene with the herpes simplex virus (HSV) thymidine kinase (tk) gene into mouse Ltk- cells, rGH gene transcripts were detected in eight of fifteen tk+ cell lines. However, in all eight clones, the predominant rGH gene transcript was only about 0.75 kb, 0.3 kb shorter than pituitary rGH mRNA. The 0.75-kb transcripts, examined from one clone, L-rGH-4, lacked sequences derived from exons 1 and 2 of the rGH gene. Although transcripts larger than 0.75 kb were detected, the normal 2.2-kb rGH gene primary transcript was present only at very low levels. Nuclease mapping studies also failed to reveal transcripts initiated at the normal rGH gene promoter, but instead revealed transcripts with 5' termini arising within intron B of the gene. These data suggest either that transcripts arise from internal promoters within the rGH gene or that a transcript initiated upstream from the normal promoter was processed abnormally. Dexamethasone increased the levels of the 0.75-kb rGH gene transcripts about fourfold in all eight clones expressing rGH mRNA. These data suggest that structural elements important for glucocorticoid-mediated influences on regulation of GH gene expression are contained within the transferred rGH gene fragment and can function even when the normal rGH gene promoter is not used and the pattern of expression is grossly abnormal.

Animals↗
PubMed1984

Interaction of small nuclear ribonucleoproteins with simian virus 40 in CV-1 cells: is U2 snRNA involved in regulating replication?

The small nuclear RNAs (snRNAs) in African Green Monkey kidney cells (CV-1 cells) were examined by polyacrylamide gel electrophoresis. Methodology was developed to improve their extraction from enriched fractions. Cellular fractionation studies and subsequent analysis of these RNAs indicate that they are tightly associated with chromatin. Treatment of cells with alpha-amanitin totally suppressed transcription of U1, U2, U4, U5, and partially suppressed transcription of U6, suggesting that these snRNAs are transcribed by RNA polymerase II. Upon infection of the cells by simian virus 40 (SV40), overall transcription of these and other cellular RNAs was stimulated. Gel filtration and formaldehyde crosslinking studies indicated that the ribonucleoproteins (snRNPs) containing snRNAs are associated with the viral minichromosome. Nucleotide sequence comparisons show extensive sequence complementarity between the 5' end of U2 RNA, the replication origin of SV40, and a prokaryotic RNA (RNA I) that is involved in control of plasmid replication. The clustered homologies between these RNAs and the association of snRNAs with the SV40 chromosome suggest that snRNAs may be evolutionarily related to small RNAs from plasmids and are consistent with an hypothesis that U2 RNA may be involved in DNA replication.

Antigens, Viral, Tumor↗
PubMed1984

Effects of adrenaline, calcium, and ouabain on the resting potential of frog muscle: interpretation based on the theory of allosteric control of cooperative interactions among surface anionic sites.

The surface adsorption theory of the cellular electric potential, a subsidiary of the association-induction hypothesis, can offer quantitative interpretations of the equilibrium resting potential of frog muscle in the presence of a constant concentration (100 mM) of external Na+ and varying external K+ (ranging from 0.1 mM to 100 mM) both in the absence and in the presence of cardinal adsorbents (ouabain, adrenaline, or Ca++). The theory can also quantitatively describe experimental data published by other laboratories from the studies of various cell types in the presence of these and other cardinal adsorbents, including some well known data which, up to now, have been regarded as specific evidence in support of the electrogenic pump theory.

Animals↗
PubMed1984

Undifferentiated carcinoma with lymphoid stroma of the parotid gland.

Six cases of undifferentiated carcinoma of the parotid gland with heavy lymphocytic infiltration have been treated at Montreal General Hospital over the past 23 years. A thorough review of the literature revealed another 31 similar cases which are discussed. For unknown reasons, these malignant tumors seem to be more common in North American Inuit. Their relatively better prognosis may be attributed to the protective function of the heavy lymphocytic infiltration. Surgery has been the treatment of choice with postoperative radiotherapy in indicated cases. Longer follow-up is necessary to assess the role of lymphocytic infiltration in improving survival.

Adolescent↗
PubMed1983

Acute epiglottitis: current management.

Two hundred and sixty-one cases of acute epiglottitis treated at the Montreal Children's Hospital between 1951 and 1980 are reviewed. Clinical features of the disease are described. Treatment protocol at a major children's hospital is presented. Statistics related to age, season and sex are analyzed. The authors compare nasotracheal intubation and tracheostomy as primary treatment. Bacteriology and antibiotic treatment are updated.

Acute Disease↗
PubMed1983

Nicotinamide and its derivatives increase growth hormone and prolactin synthesis in cultured GH3 cells: role for ADP-ribosylation in modulating specific gene expression.

To determine if changes in ADP-ribosylation of the chromosomal proteins can influence the expression of specific genes, the effects of compounds that influence this modification were investigated on the expression of the growth hormone (GH) and prolactin (Prl) genes in cultured rat pituitary (GH3) cells. The drugs tested, nicotinamide, N'-methylnicotinamide, 5-methylnicotinamide, 3-acetylpyridine, and 3-aminobenzamide, decrease ADP-ribosylation either by inhibiting (ADP-ribose)n synthetase and/or by decreaseing cellular levels of NAD+, the substrate for the enzyme. These drugs increased the synthesis of both GH and Prl and were synergistic in stimulating an increase in GH synthesis in response to triiodothyronine, a physiological regulator of GH synthesis. N'-methylnicotinamide, the most effective agent, was analyzed in detail; it increased the synthesis of both GH and Prl (maximally after 2 days) and increased their mRNAs in parallel; furthermore, this effect was reversible after drug removal. The effects of N'-methylnicotinamide were relatively specific for GH and Prl, since the synthesis of only a few other proteins was affected. These data suggest that changes in ADP-ribosylation can modulate the expression of specific genes.

Adenosine Diphosphate Ribose↗
PubMed1983

A method for isolation of intact, translationally active ribonucleic acid.

A method for isolation of large, translationally active RNA species is presented. The procedure involves homogenization of cells or tissues in 5 M guanidine monothiocyanate followed by direct precipitation of RNA from the guanidinium by 4 M LiCl. Modifications are described for use with tissue culture cells, yeast, tissues, or isolated nuclei. The advantages of the procedure include speed, simplicity, avoidance of an ultracentrifugation, and its applicability to large numbers of small samples. The procedure yields large mRNA precursors up to 10 kb and mRNA species which translate very well. However, small (less than 300 nucleotides) RNA species are recovered with a poor yield.

Chemical Precipitation↗
PubMed1983

Tan Sri Runme Shaw lecture. Genetic engineering and its impact on medicine.

Recent developments in recombinant DNA research promise to have a substantial impact on medicine. The technology now allows for DNA pieces to be isolated and ligated to other DNA, such as that from bacteria, and be replicated in foreign hosts. The replicated DNA can then be isolated and used to study its structure, to study gene expression and its regulation, to program microorganisms to synthesize medically, agriculturally or industrally important proteins, to transfer genes back into mammalian cells and to diagnose genetic diseases. The DNA used for cloning can be obtained by copying mRNA, by chemically synthesizing it and by isolating chromosomal DNA; each of these types of DNAs serve special uses. The results of studies with the use of these DNAs have provided an enormous amount of information, in some cases of a quite surprising nature, about the structure and function of genes. This information is already providing substantial insights into the mechanisms of diseases such as cancer and hopefully it will lead to newer therapies as well. The technology had already resulted in the synthesis in microorganisms of a number of useful proteins such as vaccines, insulin and interferon. The use of the DNA to diagnose genetic diseases has been applied as for instance to thalassemia and sickle cell anemia. Finally, the ability to transfer genes back into cells and to have these genes function promises to open a new approach with gene therapy that may be useful for treating not only genetic diseases, but a number of other diseases as well.

Animals↗
PubMed1982

Mouse glandular kallikrein genes. Nucleotide sequence of cloned cDNA coding for a member of the kallikrein arginyl esteropeptidase group of serine proteases.

A library of cloned cDNA to male mouse submaxillary gland poly(A)-containing RNA was constructed in the plasmid pBR322. Inserts containing sequences estimated to be in the 1-5% abundance class were identified by hybridization to radiolabeled cDNA and examined by nucleotide sequence analysis. A sequence coding for a peptide with 57% homology to the only complete kallikrein sequence reported to date (from pig pancreas) was identified by a computer search program. This insert appears to code for the COOH-terminal 149 amino acids of a protein presumed therefore to be a serine protease. Comparison of the predicted amino acid sequence of this protein with analogous sequences in the three characterized members of the mouse submaxillary gland kallikrein arginyl esteropeptidase group of enzymes revealed extensive homology, although not complete identity. Thus, there are at least four members of this enzyme family expressed in the mouse submaxillary gland.

Amino Acid Sequence↗
PubMed1982

Recombinant DNA.

Explore the source record for details and available documents.

DNA, Recombinant↗
PubMed1982

Mouse kallikrein arginyl-esteropeptidase genes: analysis of cloned cDNAs suggests rapid functional divergence from a common ancestral sequence.

A previously-cloned cDNA coding for a member of the kallikrein arginyl-esteropeptidase group of serine proteases, (pMK-1), was used as a hybridization probe to identify a second partial cDNA clone (pMK-2) from mouse submaxillary gland. pMK-2 shares more than a 98% nucleotide sequence homology with pMK-1; the 3' untranslated regions are identical and there are only two predicted amino acid changes over the C-terminal 66 amino acids. The site of one change is implicated in determining substrate specificity, while the other may affect the catalytic mechanism. Thus despite the marked similarity of pMK-1 and pMK-2, the differences probably give rise to functionally distinct enzymes and are not simply polymorphic alleles.

Amino Acid Sequence↗