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Biomedical subjects

H R Matthews

Publications and source records attributed to H R Matthews.

At least 163 records · Page 9Linked to original sources
PubMed1978

Altered nucleosome structure containing DNA sequences complementary to 19S and 26S ribosomal RNA in Physarum polycephalum.

The localization of DNA sequences coding for ribosomal RNA was studied by hybridization of purified ribosomal RNA to DNA from chromatin fragments prepared by limited digestion of Physarum nuclei with staphylococcal nuclease. The 32P-labeled 19S and 26S RNA hybridized to DNA from nucleosome monomers, dimers, trimers, and higher oligomers, separated by sucrose gradient centrifugation, although the level of hybridization to DNA from nucleosome fractions was less than the level of hybridization to undigested nuclear DNA. The distribution of 19S and 26S rDNA sequences in the nucleosome fractions differed from the distribution of bulk DNA in that the rDNA sequences were recovered primarily in two fractions containing monomer-sized DNA lengths (140-160 base pairs). The percentage of DNA hybridizing to 19S plus 26S RNA was greater in peak A, the more slowly sedimenting monomer peak, than in any other chromatin fraction at all stages of digestion. Peak A and monomer particles differed in protein content and distribution. The presence of ribosomal cistrons in an altered nucleosome configuration may be related to changes in functional states of rDNA chromatin.

Chromatin↗
PubMed1977

Selectively deuterated amino acid analogues. Synthesis, incorporation into proteins and NMR properties.

Selectively deuterated analogues of histidine, tyrosine, phenylalanine and tryptophan have been synthesized by chemical exchange. These analogues have been characterized by NMR spectrometry and used for growth of bacteria. Active lactose repressor protein has been isolated from cells grown on the deuterated amino acids, and denatured 1H and 2H NMR spectra have been determined for the protein.

Amino Acids↗
PubMed1976

Organisation of genes for ribosomal RNA in Physarum polycephalum.

Physarum polycephalum nucleolar satellite DNA has been analysed by restriction enzyme digests and hybridisation to ribosomal RNA. The nucleolar DNA is isolated as molecules of molecular weight 39 X 10(6). The positions of sites of endo R-EcoRI and endo R-HindIII digestion have been determined accurately in the whole molecule. The endo R-EcoRI sites and one endo R-HindIII site are within the26-S rRNA complementary sequence and the other endo R-HindIII site is within the 19-S rRNA complementary sequence. The sites are arranged symmetrically about the centre of the molecule as if it were a palindrome.

Cell Nucleolus↗
PubMed1976

Effect of delta-THC on ethanol withdrawal in mice.

Delta-THC (10 mg/kg, i.p.) administered to mice immediately after withdrawal from a 3-day exposure to ethanol vapor was found to intensify withdrawal reactions. No effect was seen when delta-THC was administered chronically during the exposure to ethanol.

Alcoholism↗
PubMed1976

Cell-cycle dependence of two nuclear histone kinase enzyme activities.

Growth-associated histone kinases have been extracted from Physarum polycephalum nuclei and resolved into two components by ion-exchange chromatography. The two component activities have different substrate specificities and different times of appearance in the cell cycle. It is proposed that the enzyme(s) phosphorylate H1 histone in vivo in G2 phase, possibly sequentially in time at different sites in the H1 amino acid sequence.

Cell Division↗
PubMed1976

The subunit structure of chromatin from Physarum polycephalum.

Nucleosome DNA repeat lengths in Physarum chromatin, determined by nuclease digestion experiments, are shorter than those observed in most mammalian chromatin and longer than those reported for chromatin of certain other lower eukaryotes. After digestion with staphylococcal nuclease for short periods of time an average repeat length of 190 base pairs is measured. After more extensive digestion an average repeat length of 172 base pairs is measured. Upon prolonged digestion DNA is degraded to an average monomer subunit length of 160 base pairs, with only a small amount of DNA found in lengths of 130 base pairs or smaller. Mathematical analysis of the data suggests that the Physarum nucleosome DNA repeat comprises a protected DNA segment of about 159 base pairs with a nuclease-accessible interconnecting segment which ranges from 13 to 31 base pairs. The spacing data are compatible with measurements from electron micrographs of Physarum chromatin.

Animals↗