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Biomedical subjects

M Harpold

Publications and source records attributed to M Harpold.

9 recordsLinked to original sources
PubMed1999

The Genome Sequence DataBase: towards an integrated functional genomics resource.

During 1998 the primary focus of the Genome Sequence DataBase (GSDB; http://www.ncgr.org/gsdb ) located at the National Center for Genome Resources (NCGR) has been to improve data quality, improve data collections, and provide new methods and tools to access and analyze data. Data quality has been improved by extensive curation of certain data fields necessary for maintaining data collections and for using certain tools. Data quality has also been increased by improvements to the suite of programs that import data from the International Nucleotide Sequence Database Collaboration (IC). The Sequence Tag Alignment and Consensus Knowledgebase (STACK), a database of human expressed gene sequences developed by the South African National Bioinformatics Institute (SANBI), became available within the last year, allowing public access to this valuable resource of expressed sequences. Data access was improved by the addition of the Sequence Viewer, a platform-independent graphical viewer for GSDB sequence data. This tool has also been integrated with other searching and data retrieval tools. A BLAST homology search service was also made available, allowing researchers to search all of the data, including the unique data, that are available from GSDB. These improvements are designed to make GSDB more accessible to users, extend the rich searching capability already present in GSDB, and to facilitate the transition to an integrated system containing many different types of biological data.

Animals↗
PubMed1999

Effects of ethanol on recombinant human neuronal nicotinic acetylcholine receptors expressed in Xenopus oocytes.

Alcohol and tobacco use is highly correlated in humans, and studies with animal models suggest an interaction of alcohol with neuronal nicotinic acetylcholine receptors (nAChRs). The aim of the present study was to characterize the effect of acute ethanol treatment on different combinations of human nAChR (hnAChR) subunits expressed in Xenopus oocytes. Ethanol (75 mM) potentiated ACh-induced currents in alpha2beta4, alpha4beta4, alpha2beta2, and alpha4beta2 receptors. This effect was due to an increase in Emax, without a change in the EC50 or Hill coefficient. hnAChR alpha2beta4 did not develop tolerance to repeated applications of ethanol or continuous exposure (10 min). The alpha3beta2 and alpha3beta4 combinations were insensitive to ethanol. Low concentrations of ethanol (25 and 50 mM) significantly inhibited homomeric alpha7 receptor function, but these receptors showed highly variable responses to ethanol. These results indicate that ethanol effects on hnAChRs depend on the receptor subunit composition. In light of recent evidence indicating that nAChRs mediate and modulate synaptic transmission in the central nervous system, we postulate that acute intoxication might involve ethanol-induced alterations in the function of these receptors.

Acetylcholine↗
PubMed1998

Human autoantibodies specific for the alpha1A calcium channel subunit reduce both P-type and Q-type calcium currents in cerebellar neurons.

The pharmacological properties of voltage-dependent calcium channel (VDCC) subtypes appear mainly to be determined by the alpha1 pore-forming subunit but, whether P-and Q-type VDCCs are encoded by the same alpha1 gene presently is unresolved. To investigate this, we used IgG antibodies to presynaptic VDCCs at motor nerve terminals that underlie muscle weakness in the autoimmune Lambert-Eaton myasthenic syndrome (LEMS). We first studied their action on changes in intracellular free Ca2+ concentration [Ca2+]i in human embryonic kidney (HEK293) cell lines expressing different combinations of human recombinant VDCC subunits. Incubation for 18 h with LEMS IgG (2 mg/ml) caused a significant dose-dependent reduction in the K+-stimulated [Ca2+]i increase in the alpha1A cell line but not in the alpha1B, alpha1C, alpha1D, and alpha1E cell lines, establishing the alpha1A subunit as the target for these autoantibodies. Exploiting this specificity, we incubated cultured rat cerebellar neurones with LEMS IgG and observed a reduction in P-type current in Purkinje cells and both P- and Q-type currents in granule cells. These data are consistent with the hypothesis that the alpha1A gene encodes for the pore-forming subunit of both P-type and Q-type VDCCs.

Animals↗
PubMed1980

The addition of 5' cap structures occurs early in hnRNA synthesis and prematurely terminated molecules are capped.

After cells were labeled by brief exposure to 3H-methyl-L-methionine, the majority of labeled 5' terminal cap I (m7GpppN1mpN2p) oligonucleotide structures were in nuclear RNA (hnRNA) molecules approximately 750 nucleotides or less in length. After longer label times, the proportion of cap I structures in nuclear molecules longer than mRNA rose to approximately 60% of the total, but approximately 40% of the cap I structures were still in molecules shorter than approximately 750 nucleotides. The cap I structures in both long and short hnRNA chains contained all four 2' methylated nucleotides in the N1 position in about the same proportion as in mRNA. None of the large hnRNA molecules could be demonstrated to contain 5' pppX p termini; the only such terminus in high molecular weight RNA was pppAp which was decreased markedly by low doses of actinomycin and is presumably the terminus of pre-rRNA. These results raise the possibilities that hnRNA chains can initiate with any of the four nucleotides, that capping occurs very close to or at the start of hnRNA chain synthesis and that approximately 40% of the hnRNA chains may be prematurely terminated.

Animals↗
PubMed1980

Addition of poly(A) to nuclear RNA occurs soon after RNA synthesis.

A kinetic analysis of the appearance of [3H]uridine label in RNA sequences that neighbor poly(A), as well as the incorporation of [3H]adenosine label into both the RNA chain and the poly(A) of poly(A)-containing molecules, shows that poly(A) is added within a minute or so after RNA chain synthesis in Chinese hamster ovary cells and HeLa cells. Previous conclusions by several groups (5-7) that poly(A) might be added as long as 20-30 min after RNA synthesis appear to be in error, and the present conclusion seems much more in line with several different types of recent studies with specific mRNAs that suggest prompt poly(A) addition (13-16).

Animals↗
PubMed1979

Rat growth hormone gene: intervening sequences separate the mRNA regions.

Rat genomic DNA was digested with various restriction endonucleases, separated by gel electrophoresis and hybridized to 125 I-labeled mRNA for the precursor protein to growth hormone. Restriction sites were found within the genomic DNA that were not found in the previously reported DNA sequence corresponding to the mRNA (19). It appears that the gene for growth hormone contains intervening sequences separating the DNA regions that specify mRNA sequences.

Animals↗