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Biomedical subjects

T Dick

Publications and source records attributed to T Dick.

At least 55 records · Page 3Linked to original sources
PubMed1993

Effects of intraphrenic injection of potassium on diaphragm activation.

The purpose of the present study was to determine whether potassium, injected into the arterial supply of the diaphragm, would reflexly alter efferent diaphragmatic motor outflow and systemic arterial pressure. Studies were performed using in situ canine diaphragm muscle strips in which the inferior phrenic artery and vein were cannulated and all other sources of strip blood flow were ligated. Injection of potassium (0.1 meq) into the inferior phrenic artery elicited a small transient (1-2 breaths) decrease in the peak strip tension developed during spontaneous muscle contractions, in peak integrated strip electromyographic (EMG) activity, and in the peak integrated EMG activity of the contralateral hemidiaphragm. This was followed by a more pronounced and more sustained increase in each of these parameters as well as an increase in systemic arterial pressure. This latter excitatory response was qualitatively similar to that induced by the injection of capsaicin (5 and 25 micrograms) into the phrenic artery. Section of the left phrenic nerve abolished the effects of intra-arterial potassium and capsaicin on systemic arterial pressure and right hemidiaphragm EMG activity. These data support the existence of a potent excitatory phrenic-to-phrenic reflex that can be activated by potassium injection into the diaphragm. Activation of this pathway increases diaphragm motor activation and augments systemic arterial pressure.

Afferent Pathways↗
PubMed1991

Two closely linked Drosophila POU domain genes are expressed in neuroblasts and sensory elements.

We have characterized two Drosophila POU genes designated dPOU-19 and dPOU-28. These genes are transcribed as 3.1- and 2.2-kilobase mRNAs, respectively, which accumulate maximally during the first 12 hr of embryogenesis. The mRNAs encode 601- and 475-amino acid deduced proteins; their POU domains are most related to those of the human OCT1 and OCT2. Both genes give similar nervous system expression patterns and map to an indistinguishable site at 33F on the cytological map. Transcription of the genes is first observed in the cellular blastoderm. In the course of embryonic development, expression is observed in the neuroectoderm, with subsets of neuroblasts in the procephalic and germband central nervous system as well as a subset of peripheral nervous system elements. The expression patterns of the two POU genes suggest a possible functional role for these putative transcription factors in neurogenesis and neurospecification.

Amino Acid Sequence↗
PubMed1990

Chloramphenicol-induced translational activation of cat messenger RNA in vitro.

The expression of the chloramphenicol-inducible chloramphenicol acetyltransferase gene (cat) of the staphylococcal plasmid pUB112 is regulated at the post-transcriptional level. Previous in vivo analyses suggested that the antibiotic stalls ribosomes that are translating a regulatory leader peptide, and that a stalled ribosome activates the ribosome binding site of the acetyltransferase encoding sequence by opening an attenuating leader mRNA hairpin structure. To test this model, we used a Bacillus subtilis S-30 extract for an in vitro translation system and in vitro synthesized cat in RNAs. We showed that the leader portion of the cat transcript acts as a translational attenuator of cat gene expression in absence of chloramphenicol. The drug stimulates acetyltransferase synthesis by a leader mRNA-dependent activation of translation of the cat message. By using 5' end-labeled transcripts and employing the endogenous RNase activity of the S-30 extract we demonstrated that this activation is due to an antibiotic-induced stalling of a ribosome on cat leader mRNA.

Bacillus subtilis↗
PubMed1990

A point mutation at the X-chromosomal proteolipid protein locus in Pelizaeus-Merzbacher disease leads to disruption of myelinogenesis.

A group of inherited neurological disorders are the X-chromosome linked dysmyelinoses, in which myelin membranes of the CNS are missing or perturbed due to a strongly reduced number of differentiated oligodendrocytes. In animal dysmyelinoses (jimpy mouse, msd-mouse, md rat, shaking pup) mutations of the main integral myelin membrane protein, proteolipid protein, have been identified. Pelizaeus-Merzbacher disease (PMD) or sudanophilic leucodystrophy is an X-linked dysmyelinosis in humans. We report here on the molecular basis of the defect of affected males of a PMD kindred. Rearrangements of the PLP gene were excluded by Southern blot hybridisation analysis and PCR amplification of overlapping domains of the PLP gene. Sequence analysis revealed one single C----T transition in exon IV, which leads to a threonine----isoleucine substitution within a hydrophobic intramembrane domain. The impact of this amino-acid exchange on the structure of PLP in the affected cis membrane domain is discussed. A space filling model of this domain suggests a tight packing of the alpha-helices of the loop which is perturbed by the amino-acid substitution in this PMD exon IV mutant. The C----T transition in exon IV abolishes a Hph I restriction site. This mutation at the recognition site for Hph I (RFLP) and allele-specific primers have been used for mutation screening the PMD kindred.

Base Sequence↗
PubMed1989

Characterization of the ribosomal DNA from Trichinella spiralis.

Ribosomal DNA (rDNA) from three isolates of Trichinella was cloned into phage and sublcloned into the plasmid pBR322. The basic repeat unit of rDNA was variable in size, with the mapped clones ranging from 10-12 kb. There were differences in restriction sites within the genic region among the three isolates which were due to variations in the internal transcribed region (ITS) and the intergenic spacer (IGS). Three RsaI sites were mapped to the IGS repeat unit of the isolate AF1, and one RsaI site was mapped to the IGS repeat unit of Trichinella spiralis pseudospiralis (isolate Tp). The number of repetitive units in the IGS region varied markedly within and between the isolates. It was estimated that the basic repeat unit for the rDNA of isolate P1 was 10.6-28 kb, for AF1 10.7-37 kb, and for Tp it was 11-14.9 kb. There appeared to be a greater frequency of some sizes of the basic repeat unit in each of the populations, based on the relative intensity with which certain bands hybridize to the probe.

Animals↗
PubMed1989

Effect of some metal ions on blood and liver delta-aminolevulinate dehydratase of Pimelodus maculatus (Pisces, Pimelodidae).

1. delta-ALA-D from Pimelodus maculatus was inhibited in vitro by Cd2+ greater than Pb2+ greater than Hg2+ greater than Cu2+ greater than Zn2+ in blood and by Pb2+ greater than Cd2+ greater than Hg2+ greater than Cu2+ = Zn2+ in the liver. 2. Kinetic analysis of the inhibition by the metal ions showed that Cd2+ and Hg2+ act as non-competitive inhibitors on both sources. 3. Pb2+ showed a mixed type of inhibition in blood and a non-competitive type in the liver. 4. Zn2+ acted as a competitive or mixed inhibitor, on both sources, depending on concentration.

Animals↗
PubMed1989

Major histocompatibility complex class I-restricted activation of cloned T cells by a soluble protein in the absence of accessory cells.

A T-cell clone, 10BK.1, was established from the draining lymph nodes of (B10 x B10.BR)F1 mice immunized with ovalbumin (OVA) according to standard protocols. Upon coculture with the antigen, 10BK.1 cells reacted by production of lymphokines and by proliferation despite the absence of additional antigen-presenting cells. These T cells do not express major histocompatibility complex (MHC) class II molecules on the cell surface as assessed on the basis of several criteria: by cytofluorometric analysis I-A and I-E determinants were not detectable; 10BK.1 cells could not act as antigen-presenting cells for long-term-cultured MHC class II-restricted T-cell clones; and monoclonal antibodies directed at both MHC class II isotypic complexes (I-A, I-E) did not suppress their OVA-induced activation. In contrast, proliferation of 10BK.1 T cells in response to OVA was abrogated by antibodies directed at H-2Kb antigens. Inhibition experiments employing antibodies directed at Lyt-2 and L3T4 antigens in addition to cytofluorometric analysis revealed that T-cell clone 10BK.1 exhibits the Thy-1+,Lyt-2+,Ly-1-,L3T4- phenotype. 10BK.1 cells pulsed with OVA and fixed with glutaraldehyde induced proliferation of untreated 10BK.1 cells. These data support the theory that 10BK.1 T cells present the exogenous globular protein OVA to one another in an MHC class I-restricted manner, resulting in cell activation and proliferation independent of added accessory cells.

Animals↗