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Biomedical subjects

A J Hay

Publications and source records attributed to A J Hay.

At least 73 records · Page 4Linked to original sources
PubMed1984

Identification of the influenza virus transcriptase by affinity-labeling with pyridoxal 5'-phosphate.

Pyridoxal 5'-phosphate (PLP), a reversible inhibitor of in vitro transcription by fowl plaque virus, has been used to identify the transcriptase. Kinetic analyses showed that PLP competitively inhibits the addition of each nucleoside triphosphate in ApG-primed reactions, suggesting that both initiation and elongation are affected. The irreversible inhibition by PLP following reduction with borohydride was prevented by preincubation with the first substrate: GTP in unprimed reactions or CTP in the presence of ApG. On reaction of FPV proteins with PLP and [3H]borohydride the core protein PB1 was preferentially labeled and the labeling was selectively blocked by GTP or ApG + CTP. These data suggest that PB1 has the nucleotide-binding site of the transcriptase, is responsible for both initiation and elongation, and is apparently associated with the 3' ends of template RNAs in virions.

Affinity Labels↗
PubMed1983

The carbohydrate units of asialo-ovomucoid: their heterogeneity and enzymic degradation.

An ovomucoid variant free from sialic acid has been prepared in a pure state by ion-exchange chromatography on DEAE-cellulose. The purified glycoprotein contained 10-11 residues of mannose, 2-3 residues of galactose, and 21 residues of 2-acetamido-2-deoxyglucose. Glycopeptides have been prepared by exhaustive digestion with Pronase followed by ion-exchange chromatography on Dowex 50 (X2) resin. Three fractions were obtained, all with similar contents of mannose and hexosamine but with various contents of galactose. The sugar-aspartic acid ratios indicated that all of the fractions were heterogeneous, the major fraction having mannose-galactose-hexosamine-aspartic acid ratios of 2.6:0.5:5.8:1.0. Cleavage of asialo-ovomucoid with cyanogen bromide and proteolytic digestion of the isolated fragments gave two heterogeneous glycopeptide fractions of similar composition. Both asialo-ovomucoid and the principal glycopeptide fraction were degraded with beta-D-galactosidase, alpha-D-mannosidase, and beta-N-acetylglucosaminidase singly and in sequence. Removal of much of the carbohydrate from asialo-ovomucoid had no appreciable effect on its anti-tryptic activity. By sequential degradation of the glycopeptide, a pentasaccharide core alpha-D-Man-[alpha-D-Man]-beta-D-Man-beta-D-GlcNAc-beta-D-GlcNAc-Asn was obtained. Other structural features revealed by enzymic degradation are discussed.

Animals↗
PubMed1983

The carbohydrate units of asialo-ovomucoid: structural features.

The structural features of a heterogeneous glycopeptide fraction from asialo-ovomucoid have been investigated by methylation analysis of the fraction and of products obtained at each stage of its sequential degradation with exo-glycosidases. All glycopeptides in the fraction had a common core-structure beta-D-GlcpNAc-(1 leads to 4)-[beta-D-GlcpNAc-(1 leads to 2)]-alpha-D-Manp-(1 leads to 3)-[beta-D-GlcpNAc-(1 leads to 4)]-[beta-D-GlcpNAc-(1 leads to 2)-alpha-D-Manp-(1 leads to 6)]-beta-D-Manp-(1 leads to 4)-beta-D-GlcpNAc-(1 leads to 4)-beta-D-GlcpNAc leads to Asn. Heterogeneity in the fraction arose from variation in the amount of terminal galactose attached via a hexosaminyl residue to the alpha-D-Manp-(1 leads to 3) residue, and from limited variation in the number of terminal hexosaminyl groups attached to the alpha-D-Manp-(1 leads to 6) residue. One glycopeptide in the fraction contained the unusual feature of two different, triply-substituted mannosyl residues. Other structural features of the glycopeptide are discussed.

Asialoglycoproteins↗
PubMed1983

The isolation and immunochemical characterisation of a cell-wall carbohydrate and a membrane lipocarbohydrate antigen of group B streptococcus, type II.

Two distinct carbohydrate antigens were isolated from the cell surface of group B streptococcus, type II. One antigen was extracted from SDS-purified cell walls by cold trichloroacetic acid and contained galactose, glucose, rhamnose, glucosamine and sialic acid in the approximate molar proportions 1.7:1.0:3.4:0.9:0.21 respectively. The serological activity of this polymer indicated that it is the group-specific antigen common to all group B streptococci. The second antigen was extracted by phenol from cell membranes and contained galactose, glucose, glucosamine, phosphorus and fatty acid in a molar ratio of 1.6:1.0:0.35:2.6:0.016 respectively. This antigen was shown to be specific for type II, group B streptococcus.

Antigens, Bacterial↗
PubMed1982

Genetic composition and virulence of influenza virus: differences in facets of virulence in ferrets between two pairs of recombinants with RNA segments of the same parental origin.

Facets of virulence for ferrets of 16 recombinant clones of two parent viruses A/Finland/4/74 (H3N2) and A/Okuda/57 (H2N2) were determined and viewed in relation to their genetic composition. Of the five pairs of recombinant clones with RNA segments of the same parental origin, differences in facets of virulence were detected between members of two of the pairs. One pair differed in ability to produce fever, and another pair in ability to infect the lower respiratory tract. Subsequent analyses indicated slight differences in two genes of the first pair of viruses. Of all the recombinant clones examined the three that derived their surface antigens from the attenuated parent (A/Okuda) were less virulent than the 13 which possessed the surface antigens of the virulent parent (A/Finland). The virulence of the latter clones tended to decrease as the number of RNA segments that were derived from A/Okuda increased.

Animals↗
PubMed1982

Studies of fowl plague virus temperature-sensitive mutants with defects in transcription.

Two fowl plague virus temperature-sensitive (ts) mutants belonging to different complementation groups were studied. Both were defective in the syntheses of unpolyadenylated complementary RNA [A(-)cRNA] and virus RNA (vRNA) at non-permissive temperature whereas primary transcription was unaffected. In addition, ts 29, in which the ts mutation is in gene 1 coding for polypeptide P3, has a defect in 'secondary' synthesis of mRNA at non-permissive temperature whereas inhibition of mRNA synthesis by ts 131, in which the ts mutation is in gene 2 coding for polypeptide P1, appeared to result from a defect in vRNA synthesis. These results indicate, therefore, that different enzymes are responsible for the syntheses of virus mRNAs and A(-)cRNAs, which is consistent with the apparent differences in initiation and termination of transcription in the two reactions. The patterns of synthesis of the various types of virus RNA during infection are discussed.

Cycloheximide↗
PubMed1981

Survey of bacteria in private swimming pools.

In a survey of the bacteria in swimming pools treated with either chlorine or Baquacil in private gardens in Melbourne, the water was frequently found to be at the incorrect pH and to contain biocides at suboptimal concentrations. The general bacterial flora count was commonly greater than 200 per mL; only 14% of chlorine-treated pools and 27% of Baquacil-treated pools consistently gave counts of less than 200 per mL. Coliforms were detected in 66% of chlorine-treated pools and in 22% of Baquacil-treated pools. Escherichia coli was detected in 32% of chlorine-treated pools and 8% of Baquacil-treated pools. Staphylococcus aureus was detected in 36% of chlorine-treated pools and in 8% of Baquacil-treated pools. Pseudomonas aeruginosa was detected in 7% of chlorine-treated pools, but not at all in Baquacil-treated pools. When the biocides were maintained at the correct concentration, the indicator organisms were well controlled by both biocides. This survey indicates that owners of pools need to be made aware that their pools can harbour potentially pathogenic bacteria unless biocides are constantly maintained at the correct concentration. Baquacil generally remains above the minimum recommended concentration for approximately 14 days between routine additions, whereas chlorine can dissipate from the pool within hours of addition on hot sunny days. This probably contributed to the superior over-all performance of Baquacil in this survey.

Biguanides↗
PubMed1980

Structure and synthesis of influenza virus complementary RNAs.

Two classes of genome transcript are involved in the replication of influenza viruses, both of which contain molecules complementary to all eight genome RNAs. One of these classes, which comprises the viral mRNAs, consists of transcripts that have additional 5' terminal non-viral sequences including "cap" structures and 3' terminal polyadenylate sequences but which lack sequences corresponding to nucleotides 1-16 at the 5' termini of the virus RNAs. The members of the other class are complete genome transcripts with no additional sequences and these are thought to be the templates for genome replication. The syntheses of the two classes of molecules have a number of distinctive features which together with their structural properties indicate that they are synthesized by different mechanisms.

Base Sequence↗
PubMed1979

The matrix protein gene determines amantadine-sensitivity of influenza viruses.

The genetic composition of several recombinant strains, produced by mixed infection with an amantadine-sensitive and an amantadine-resistant influenza virus, have been compared with their response to amantadine. It is concluded that transfer of resistance or sensitivity to amantadine is determined by a single gene, that coding for the matrix protein.

Amantadine↗
PubMed1979

Characterization of influenza virus RNA transcripts synthesized in vitro.

Polyadenylated transcripts synthesized in vitro by detergent-disrupted influenza virus resemble virus mRNAs in that they possess the complement of the 3' terminus of the genome RNAs but lack sequences corresponding to the same 5' terminal region, including the homologous sequence of nucleotides 1 to 22. Transcription is initiated at the 3' terminus by both ApG and GpG as well as in the absence of added primer.

Base Sequence↗
PubMed1979

Differentiation of the haemagglutinin genes of variant influenza viruses by RNA-RNA hybridization.

The genetic compositions of four antigenic variants of A/Memphis/1/71 (H3N2) influenza virus, which were selected by growth in the presence of monoclonal antibodies against the haemagglutinin, were compared. The results indicate that the mutant haemagglutinin genes can be differentiated by polyacrylamide gel electrophoresis of the double stranded RNA hybrids formed between virion RNA and transcripts isolated from infected cells.

Genes, Viral↗
PubMed1978

Nucleotide sequences at the 5' termini of influenza virus RNAs and their transcripts.

The results of analyses of the 5'-terminal sequences of Fowl Plague virus RNAs are presented. The first 13 residues of each of the eight RNA molecules which constitute the genome are in the identical sequence 5'AGUAGAAAUUAGG- and this conservation of sequence is shown to extend to other influenza viruses. The 5'-terminal sequences of virion RNA transcripts produced in vitro are also reported and again the first 12 nucleotides of these are identical for all influenza type A transcripts examined in the sequence 5'AGCAAAAGCAGG-. In addition the results of attempts to determine the sequence relationship between vRNAs and the two classes of complementary RNA synthesized in influenza infected cells are described which support the conclusion that influenza messenger RNAs are incomplete transcripts.

Base Sequence↗
PubMed1978

On the mechanism of inhibition of influenza virus replication by amantadine hydrochloride.

The results of analyses of fowl plague virus-specific RNA and protein synthesis in infected chick embryo fibroblasts incubated in amantadine hydrochloride are reported. They indicate that provided amantadine is present from the time of virus addition no expression of the virus genome occurs and that the synthesis of even the first detectable transcripts catalysed by the polymerase of the infecting virus particles is prevented. In agreement with previous reports it is concluded that amantadine prevents an unknown event which occurs immediately following virus infection.

Amantadine↗