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Biomedical subjects

R J Gregory

Publications and source records attributed to R J Gregory.

At least 91 records · Page 5Linked to original sources
PubMed1987

Primary sequence and developmental expression of a novel Drosophila melanogaster src gene.

We have sequenced a cDNA clone for the Drosophila melanogaster gene Dsrc28C, a homolog of the vertebrate gene c-src. The cDNA contains a single open reading frame encoding a protein of 66 kilodaltons which contains features highly conserved within the src family of tyrosine protein kinases. Novel structural features of the Dsrc28C protein include a basic pI and a polyglycine domain near the amino terminus. Cell-free translation of in vitro-transcribed RNA yielded a protein of the predicted size which could be immunoprecipitated by anti-v-src antisera. RNA blot hybridization revealed that the gene is expressed predominantly during embryogenesis, in imaginal disks of third-instar larvae, and in adult females. In situ hybridization showed that expression in adult females is largely confined to nurse cells and developing oocytes.

Amino Acid Sequence↗
PubMed1986

Site-directed mutagenesis of the binding site for ribosomal protein S8 within 16S ribosomal RNA from Escherichia coli.

Twelve specific alterations have been introduced into the binding site for ribosomal protein S8 in Escherichia coli 16S rRNA. Appropriate rDNA segments were first cloned into bacteriophage M13 vectors and subjected to bisulfite and oligonucleotide-directed mutagenesis in vitro. Subsequently, the mutagenized sequences were placed within the rrnB operon of plasmid pNO1301 and the mutant plasmids were used to transform E. coli recipients. The growth rates of cells containing the mutant plasmids were determined and compared with that of cells containing the wild-type plasmid. Only those mutations which occurred at highly conserved positions, or were expected to disrupt the secondary structure of the binding site, increased the doubling time appreciably. The most striking changes in growth rate resulted from mutations that altered a small internal loop within the S8 binding site. This structure is phylogenetically conserved in prokaryotic 16S rRNAs and may play a direct role in S8-16S rRNA recognition and interaction.

Base Sequence↗
PubMed1984

Interaction of ribosomal proteins S6, S8, S15 and S18 with the central domain of 16 S ribosomal RNA from Escherichia coli.

The co-operative interaction of 30 S ribosomal subunit proteins S6, S8, S15 and S18 with 16 S ribosomal RNA from Escherichia coli was studied by (1) determining how the binding of each protein is influenced by the others and (2) characterizing a series of protein-rRNA fragment complexes. Whereas S8 and S15 are known to associate independently with the 16 S rRNA, binding of S18 depended upon S8 and S15, and binding of S6 was found to require S8, S15 and S18. Ribonucleoprotein (RNP) fragments were derived from the S8-, S8/S15- and S6/S8/S15/S18-16 S rRNA complexes by partial RNase hydrolysis and isolated by electrophoresis through Mg2+-containing polyacrylamide gels or by centrifugation through sucrose gradients. Identification of the proteins associated with each RNP by gel electrophoresis in the presence of sodium dodecyl sulfate demonstrated the presence of S8, S8 + S15 and S6 + S8 + S15 + S18 in the corresponding fragment complexes. Analysis of the rRNA components of the RNP particles confirmed that S8 was bound to nucleotides 583 to 605 and 624 to 653, and that S8 and S15 were associated with nucleotides 583 to 605, 624 to 672 and 733 to 757. Proteins S6, S8, S15 and S18 were shown to protect nucleotides 563 to 605, 624 to 680, 702 to 770, 818 to 839 and 844 to 891, which span the entire central domain of the 16 S rRNA molecule (nucleotides 560 to 890). The binding site for each protein contains helical elements as well as single-stranded internal loops ranging in size from a single bulged nucleotide to 20 bases. Three terminal loops and one stem-loop structure within the central domain of the 16 S rRNA were not protected in the four-protein complex. Interestingly, bases within or very close to these unprotected regions have been shown to be accessible to chemical and enzymatic probes in 30 S subunits but not in 70 S ribosomes. Furthermore, nucleotides adjacent to one of the unprotected loops have been cross-linked to a region near the 3' end of 16 S rRNA. Our observations and those of others suggest that the bases in this domain that are not sequestered by interactions with S6, S8, S15 or S18 play a role involved in subunit association or in tertiary interactions between portions of the rRNA chain that are distant from one-another in the primary structure.(ABSTRACT TRUNCATED AT 400 WORDS)

Base Sequence↗
PubMed1984

Effects of site-directed mutations in the central domain of 16 S ribosomal RNA upon ribosomal protein binding, RNA processing and 30 S subunit assembly.

Using a multicopy plasmid encoding the Escherichia coli rrnB ribosomal RNA operon and the techniques of in vitro site-directed mutagenesis, we have introduced several small alterations into the central domain of 16 S rRNA, which encompasses nucleotides 560 to 890. Four of the rRNAs studied contained deletions and one contained an insertion. The altered small ribosomal subunit rRNAs were used to investigate relationships among 16 S rRNA processing, protein-16 S rRNA interactions and assembly of the 30 S ribosomal subunit. Analysis of plasmid-coded transcripts from maxicells revealed that products from wild-type 16 S rRNA genes were fully processed and assembled into mature 30 S subunits. Under the same conditions, the processing and assembly of transcripts derived from the mutant plasmids were severely impaired. In some instances, the mutations completely blocked both processes, while in other cases rRNA maturation and ribosome assembly were retarded, but not eliminated completely. In all cases, the mutations led to the accumulation of the 17 S precursor to 16 S rRNA. The mutant 17 S rRNAs were purified and incubated with various combinations of E. coli ribosomal proteins S6, S8, S15 and S18, which are known to bind to the central domain of 16 S rRNA. Ribonuclease digestion of the resulting protein-17 S rRNA complexes and fractionation of the products permitted detection of three distinct protein-RNA fragment complexes which contained S8, S8 + S15, or S6 + S8 + S15 + S18. Whereas wild-type 17 S rRNA was able to form all three of these complexes, deletion of nucleotides 693 to 721 or 822 to 874 abolished the interaction of S6 and S18, and removal of nucleotides 659 to 718 prevented the binding of S6, S15 and S18. In contrast, elimination of residue 614, or the presence of a 16-base insertion between nucleotides 614 and 615, had no significant effect on the binding of any of the four proteins tested. Together, our results demonstrate that 16 S rRNA maturation and 30 S subunit assembly are tightly coupled, and show that, in at least some cases, defects in these processes can be correlated with the inability of particular ribosomal proteins to associate with altered rRNA molecules. Moreover, we have confirmed the essentiality of certain rRNA sequences for the formation and/or stabilization of these protein-rRNA interactions.(ABSTRACT TRUNCATED AT 400 WORDS)

Centrifugation, Density Gradient↗
PubMed1979

A short form of the Category Test for adults.

Proposed a 120-item version of the 208-item Category Test for adults. When the test protocols of 70 diverse Ss including 18 with definite brain impairment were scored for both the standard and short form, a very high degree of correlation (r = .95) was found, which suggests that the two forms are nearly equivalent. The application of cut-off scores (normal vs. brain impaired) resulted in only 3 Ss changing classifications from the standard to the short form, with 2 of those changes in the correct direction. A savings in administration time of about one half was observed.

Adolescent↗
PubMed1979

Reliability of the Finger Tapping Test and a note on sex differences.

The reliability of the Finger Tapping Test was investigated in two studies. In the test-retest condition 30 male and 30 female college students were tested twice by the same examiner. In the inter-examiner condition 30 male and 30 female college students were tested once by each of two examiners. Reliability coefficients for the dominant and nondominant hands were high in both studies (about .8), as contrasted with that of the ratio score (about .5), casting doubt on the use of the ratio score to lateralize impairment. Significant sex differences (males about 3 taps faster) were found, calling into question the use of single test interpretation schemes. Slight inter-examiner differences in mean scores were also detected.

Adult↗
PubMed1978

Adjective correlates for women on the CPI scales: a replication.

In a replication of a ten-year-old study by Gough, peer-rated adjectives from the Adjective Check List were correlated with scores on the 18 standard scales of the California Psychological Inventroy (CPI) for 95 college sorority members. For each scale, the ten most positively and negatively correlated adjectives were selected for comparison with Gough's results. The absolute magnitude of the correlations, the qualitative content of the adjectives, and the degree of correspondence with Gough's findings were used to assess the extent to which each CPI scale achieved its stated objective.

Achievement↗
PubMed1971

Exchange transfusion with dextran 40 in polycythaemia secondary to hypoxic lung disease.

In eight patients with polycythaemia secondary to hypoxic lung disease 10 elective exchange transfusions were performed to reduce red cell mass, packed cell volume (P.C.V.), and whole blood viscosity. The rationale for reducing P.C.V. is discussed. It is concluded that patients with P.C.V. of 60% or over will benefit from exchange transfusion and that most patients with P.C.V. over 50% and true polycythaemia will also benefit. We also confirm that the technique of exchange transfusion is a rapid, safe, and effective method of achieving large venesections and reducing red cell mass.

Aged↗