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Biomedical subjects

M Gibbs

Publications and source records attributed to M Gibbs.

At least 19 recordsLinked to original sources
PubMed1995

Phosphorylation changes following weakly reinforced learning and ACTH-induced memory consolidation for a weak learning experience.

The formation of a protein synthesis-dependent long-term memory stage in day-old chicks trained on a passive discriminated avoidance task has been shown to occur only with an adequate level of reinforcement, and is preceded by a significant change in the phosphorylation state of the forebrain synaptosomal membrane protein GAP43 protein. In the present study, it is shown that weakly reinforced training did not lead to formation of a long-term memory stage or to any change in phosphate incorporation into forebrain P2M protein bands. However, administration of ACTH immediately posttraining led to both the formation of the long-term memory stage and a preceding significant increase in the phosphorylation of GAP43. These findings are consistent with the view that a reinforcement-dependent neurohormone-mediated change to the phosphorylation of this synaptosomal membrane protein may be implicated in the triggering of long-term memory consolidation.

Animals↗
PubMed1993

A tetranucleotide repeat mouse minisatellite displaying substantial somatic instability during early preimplantation development.

The highly variable mouse minisatellite Hm-2 is located on chromosome 9 and consists of GGCA tetranucleotide repeats with alleles containing up to 5000 repeat units. This locus is unstable with a germline mutation rate to new length alleles of at least 3.6% per gamete. Hm-2 also shows substantial somatic instability, producing mutational mosaicism detectable in 20% of adult mice. Analysis of allele dosage in mice carrying somatic mutations, plus studies of mosaicism in mouse embryos and extraembryonic tissues, suggests that somatic mutant alleles preferentially arise during preimplantation development and particularly during the first two cell divisions after fertilization.

Alleles↗
PubMed1991

Spontaneous mutation at the hypervariable mouse minisatellite locus Ms6-hm: flanking DNA sequence and analysis of germline and early somatic mutation events.

Hypervariability at minisatellite loci is maintained by spontaneous mutation to new-length alleles. At the most variable loci, mutation rate is directly measurable by pedigree analysis. The mouse minisatellite locus Ms6-hm has a germline mutation rate of 2.5% per gamete and is therefore one of the most unstable loci yet identified in the mouse genome. Mutation events at this locus also occur during early mouse development, resulting in mice mosaic for cells carrying a common non-parental allele in different somatic tissues and the germline. The DNA sequence flanking Ms6-hm is rich in dispersed repetitive elements; the minisatellite array has expanded from within a member of the Mouse Transcript family which is flanked by two additional Mouse Transcript elements, and a B2 element lies further 3' to the minisatellite. To define the characteristics of mutation events at Ms6-hm we have analysed 19 germline and 13 somatic length-change events. Germline mutation events at Ms6-hm are not accompanied by the exchange of flanking markers in three informative mutant alleles analysed.

Alleles↗
PubMed1991

Principles and recent advances in human DNA fingerprinting.

Since 1985, DNA typing systems have played an increasingly important role in many aspects of human genetics, most notably in forensic and legal medicine. This article reviews the development of multilocus and single locus minisatellite DNA probes, and more recently the use of PCR to amplify hypervariable DNA loci, as well as discussing the biological properties of the unstable regions of DNA which form the basis of almost all DNA fingerprinting systems.

Base Sequence↗
PubMed1989

Characterization of a highly unstable mouse minisatellite locus: evidence for somatic mutation during early development.

A highly unstable mouse minisatellite locus, Ms6-hm, has been identified in mouse DNA fingerprints produced by cross-hybridization with human minisatellite probe 33.6. A 7-kb allele of Ms6-hm was cloned from a C57BL/6J mouse and collapsed to a 400-bp plasmid insert on propagation in Escherichia coli due to loss of the majority of minisatellite repeat units. Sequence analysis revealed that Ms6-hm has evolved by amplification within a member of the MT (mouse transcript) family of interspersed repetitive elements. Linkage analysis localized Ms6-hm near the brown coat color gene (b) on chromosome 4. Multiallelism and heterozygosity at this locus within inbred strains result from a high germline mutation rate to new-length alleles (2.5% per gamete). Mice mosaic for cells carrying a nonparental allele in somatic tissue, and in some cases also in the germline, provide evidence for additional, somatic, mutation events at Ms6-hm. In two mosaic mice the fraction of cells containing the nonparental allele has been shown to be indistinguishable in different adult tissues. These somatic mutation events at Ms6-hm must therefore occur very early in development, preceding the allocation of somatic lineages, and the same pool of primitive ectoderm cells must contribute equally to all somatic tissues. Under low-stringency hybridization conditions the collapsed subclone of Ms6-hm cross-hybridizes to other unstable loci in the mouse genome to generate a novel and highly individual specific mouse DNA fingerprint.

Alleles↗
PubMed1988

Distribution of muscarinic cholinergic receptors in the dorsal vagal complex and other selected nuclei in the human medulla.

Muscarinic cholinergic receptors were localized in human brainstem by quantitative autoradiography, using the radioligand [3H]quinuclidinyl benzilate. Receptor densities were highest in the hypoglossal nucleus. The second highest density was found in the medial region of the nucleus of the solitary tract (NTS). Moderately high numbers of receptors were present in the dorsal motor nucleus of the vagus, the dorsal NTS, subpostremal NTS, lateral NTS and ventral NTS. Intermediate densities were present in the dorsal and medial accessory nuclei of the inferior olive and the spinal trigeminal nucleus pars interpolaris. Low densities were found in the area postrema, principle nucleus of the inferior olive, gracile nucleus, cuneate nucleus and the tractus of the NTS. Muscarinic cholinergic receptors in the dorsal vagal complex are an important component of the neural substrate governing visceral function. These receptors may be the central site of action of anticholinergic medications in suppressing emesis.

Autoradiography↗
PubMed1988

Encephalitis lethargica-like illness in a girl with mycoplasma infection.

We describe a patient with mycoplasma infection and clinical manifestations of encephalitis lethargica. The patient was brought to our attention after acute neurologic deterioration followed by a prolonged sleep-like state and the emergence of extrapyramidal features. MRI of the brain disclosed a striking pattern of subcortical involvement by the inflammatory process, corroborating the clinical picture.

Brain↗
PubMed1986

Astrocyte culture on nitrocellulose membranes and plastic: detection of cytoskeletal proteins and mRNAs by immunocytochemistry and in situ hybridization.

Neonatal rat brain astrocyte secondary cultures were established on nitrocellulose membrane filters (13-mm diameter Millipore disk) and on plastic coverslips in serum-supplemented medium. On these substrata, cultured astrocytes changed their shape from flat and polygonal to stellate in the absence of hormones or growth factor supplements. Cultures became confluent after 4 days, and astrocytes on nitrocellulose filters continued to differentiate morphologically and biochemically, as evidenced by extensive cytoplasmic process formation and glial fibrillary acid protein (GFAP) accumulation. Cultures were immunostained for GFAP and vimentin. mRNAs to GFAP, vimentin, alpha and beta tubulin, and actin also were detected by in situ hybridization with biotinylated cDNA probes. The astrocyte culture method on nitrocellulose provides a simple, versatile means of comparing undifferentiated, morphologically mature, reactive, and neoplastic astrocytes in vitro.

Animals↗
PubMed1986

Tort law reform.

Explore the source record for details and available documents.

Malpractice↗
PubMed1984

Remodeling of sperm chromatin following fertilization: nucleosome repeat length and histone variant transitions in the absence of DNA synthesis.

Within the first cell cycle following fertilization the average nucleosomal repeat length of sea urchin male pronuclear chromatin declines by 30-40 base pairs to a value typical of that found in the embryo. This decline occurs after a lag of about 30 min postfertilization, and is accompanied by replication of the male chromatin and accumulation of cleavage-stage (CS) core histone variants. When replication is inhibited by greater than 95% with aphidicolin, the decline in repeat length still occurs, although it is slightly retarded. The decline in repeat length also occurs when protein synthesis is blocked by greater than 98% and DNA synthesis by 60-70% with emetine. The adjustment of nucleosome repeat length therefore can occur in vivo without extensive movement of replication forks across the length of the chromatin, or normal progression of the cell cycle, and appears to require no proteins synthesized postfertilization. Blocking of DNA synthesis or protein synthesis also does not prevent the normal histone variant transitions involved in male pronuclear chromatin remodeling. Although their accumulation is slowed, CS core variants eventually become the predominant male pronuclear histones in their classes when replication is inhibited. Since a shortening of the average nucleosomal repeat length of approximately 10-20% is not sufficient to account for this large acquisition of CS variants, some of the sperm (Sp) core histones are probably displaced from the replication-blocked pronucleus. Therefore, accumulation of CS H2A and CS H2B are temporally correlated with the repeat length transition, whereas replication, normal progression of the cell cycle, and the early histone transitions involving SpH1 and SpH2B are not.

Animals↗
PubMed1984

School children's attitudes towards the handicapped.

This study set out to determine the attitude of a group of normal British 13-year-old school children towards handicapped people while avoiding problems of previous research. As has been shown in previous studies it was demonstrated that the children's attitudes to the physically handicapped were more positive than those towards the mentally handicapped. Whereas there were very few sex differences indicating that males were more negative to the handicapped in general than females, there were a number of contact differences. Children who knew or interacted with a handicapped person were by-and-large more positive in their attitudes than those who had little or no contact with handicapped people. The results of this study are discussed in terms of the integration of handicapped and non-handicapped school children.

Adolescent↗
PubMed1981

In vivo enamel fluoride uptake from and caries inhibition by topical fluoride agents.

Acidulated phosphate fluoride (APF), Duraphat or Fluor Protector, was applied to the molar teeth of rats fed a cariogenic diet. The first maxillary molar teeth were subjected to a microbiopsy procedure for fluoride analysis and the mandibular molars scored for caries. All three topical fluoride agents produced a significant increase in the fluoride content of the outermost 5.0 micron of enamel. Only APF produced a significant reduction in caries incidence at all sites.

Acidulated Phosphate Fluoride↗