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Biomedical subjects

A Chambers

Publications and source records attributed to A Chambers.

At least 19 recordsLinked to original sources
PubMed1992

Sexually transmitted diseases amongst a sample of people seeking HIV testing.

AIMS: To examine the incidence of sexually transmitted diseases according to gender, age, sexual orientation, sexual behaviour and drug use. METHODS: Data were collected from 814 clients attending anonymously for HIV testing at the Burnett Centre in Auckland. During pretest counselling clients were asked questions designed to assess their risk of HIV infection including a detailed history of sexually transmitted diseases (STDs). RESULTS: Amongst attenders 44% reported at least one lifetime STD including 16% reporting more than one. Multiple STDs were not associated with gender or sexual orientation but they were associated with the practice of anal sex and with a history of multiple sex partners. Alcohol and drug use were also related to multiple STDs. For men the most common STD was NSU with 20% of them reporting it whereas for women genital warts was the most common reported by 18%. Amongst those under 20 years 9% reported genital warts, 7% NSU and 6% chlamydia. CONCLUSIONS: The findings confirm that it is sexual practices which put people at risk of infection from STDs rather than their sexual orientation. They also draw attention to the role that drugs and alcohol play in the practice of unsafe sex and the consequent transmission of STDs. Finally they suggest that screening for STDs as well as HIV in AIDS clinics should be encouraged.

Adult↗
PubMed1992

Condom use in anal intercourse amongst people who identify as homosexual, heterosexual or bisexual.

AIMS: to study condom use amongst those who practice anal intercourse. METHODS: a sample of 814 clients attending anonymously for pretest counselling for HIV infection at the Burnett Clinic, Auckland, gave detailed information about their sexual behaviour. RESULTS: insertive or receptive anal intercourse was reported in 39% of clients. This included 89% among homosexual men, 78% among bisexual men, 17% among heterosexual men and 21% among heterosexual women. In those practising anal intercourse concomitant condom use was reported by 71% of homosexual men, 53% of bisexual men, 16% of heterosexual men and 7% of heterosexual women. Those most likely to use condoms were homosexual men, prostitutes, those with multiple partners and those with an HIV infected partner. Those least likely to use condoms were heterosexual men or women. CONCLUSIONS: whilst substantial changes in sexual practices appear to have been made in the homosexual community, heterosexuals practising anal intercourse have made few such changes. More explicit AIDS education may be necessary which acknowledges that anal intercourse is practised by heterosexuals and advises condom use accordingly.

Ambulatory Care Facilities↗
PubMed1991

Aging, sleep disorders, and male sexual function.

The relation between age, sleep disorders, nocturnal penile tumescence, and sexual behavior was investigated in 70 healthy married men aged 45-75 years. They had an extensive psychosexual interview, a medical and psychiatric evaluation, and were studied in the sleep laboratory for four nights. Electroencephalogram (EEG), eye movements, muscle tone, and penile tumescence were monitored continuously, and respiratory airflow and bilateral anterior tibialis recordings were obtained during the first sleep session. There was a marked age-related increase in sleep-disordered breathing, but no significant changes in periodic leg movements with age. Respiratory distress and periodic leg movement (PLM) indices were mostly unrelated with nocturnal penile tumescence (NPT) measures as well as with all sexual behavior dimensions when age was taken into account in the analysis of results. Men with a respiratory distress disorder did not differ from a nondisordered group of similar age in NPT and behavioral parameters. Men with PLM disorder differed from their comparison group in only two variables: fewer number of maximum tumescent episodes and less frequent sexual thoughts. Men who met criteria for erectile impotence did not differ significantly in degree of respiratory or PLM disturbances or in the prevalence of sleep disorders when compared to an aged-matched sexually nondysfunctional group. The overall results did not support the notion that sleep disorders are involved in the increased prevalence of erectile impotence in healthy older individuals. Assessment of blood oxygenation and respiratory effort, in addition to airflow, need to be carried out before final conclusions can be drawn on the significance of sleep-disordered breathing in male sexuality.

Age Factors↗
PubMed1990

Phosphorylation influences the binding of the yeast RAP1 protein to the upstream activating sequence of the PGK gene.

Yeast repressor activator protein 1 (RAP1) binds in vitro to specific DNA sequences that are found in diverse genetic elements. Expression of the yeast phosphoglycerate kinase gene (PGK) requires the binding of RAP1 to the activator core sequence within the upstream activating sequence (UAS) of PGK. A DNA fragment Z+ which contains the activator core sequence of the PGK(UAS) has been shown to bind RAP1. Here we report that phosphatase treatment of RAP1 affected its binding to the PGK(UAS) but that this depended on the nature of the sequence flanking the 5' end of the activator core sequence. When the sequence flanking the 5' end of the activator core sequence was different from the PGK RAP1-binding site, phosphatase treatment of RAP1 decreased its binding to the DNA. When the 5' end of the binding site was a match to the PGK RAP1-binding site dephosphorylation of RAP1 increased RAP1 binding to the DNA. These observations were reproduced when the minimal functional DNA-binding domain of the RAP1 protein was used, implicating a phosphorylation-dependent binding of RAP1. This is the first evidence for phosphorylation-dependent binding of RAP1.

Amino Acid Sequence↗
PubMed1990

ARS binding factor 1 binds adjacent to RAP1 at the UASs of the yeast glycolytic genes PGK and PYK1.

The UAS of the yeast gene encoding the glycolytic enzyme phosphoglycerate kinase (PGK) contains several different sequence elements involved in transcriptional activation. These elements include the activator core sequence, which is bound by the RAP1 protein, and three copies of the pentamer sequence 5' CTTCC 3'. Upstream of the activator core sequence is a region (Yfp), identified as the site of a strong DNA-protein interaction. The Yfp region contains the consensus binding site for the factor ABF1. We have purified the Y protein, which binds to the Yfp region, to homogeneity. The Y protein migrates as a doublet on SDS-polyacrylamide gel electrophoresis with an apparent molecular weight of 125 KDa. These properties are similar to those of ABF1. ABF1 synthesised in vitro bound strongly to the Yfp region and formed a gel retardation complex of identical mobility to the complex formed by the Y protein. UAS1 of the pyruvate kinase gene (PYK1) promoter contains a RAP1 binding site and single copy of the CTTCC sequence. We have now identified an ABF1 binding site close to the RAP1 binding site and CTTCC sequence in the PYK1 promoter. This site is strongly bound by ABF1 in vitro. The organisation of the PGK and PYK1 UASs is thus similar to each other and to the transcriptional silencer HMR(E) which also contains these sequences.

Base Sequence↗
PubMed1990

A nuclear translational block imposed by the HIV-1 U3 region is relieved by the Tat-TAR interaction.

Replication of HIV-1 depends on the viral Tat protein, which functions via a target sequence, TAR, present in the proviral long terminal repeat (LTR) and at the 5' end of viral mRNAs. We have shown that Tat potentiates the expression of TAR-containing RNAs, but only when Tat and the TAR-containing RNA are present in the nucleus. We now show that a small change in the TAR loop abolishes nuclear potentiation by Tat. Furthermore, the HIV-1 U3 region induces expression incompetence in mRNA synthesized by this promoter. RNAs of identical structure are, however, translated efficiently when produced from the CMV-IE promoter. The Tat-TAR system appears, therefore, to rescue the expression potential of HIV-1 LTR-directed RNA.

Animals↗
PubMed1990

Characterisation of the DNA binding domain of the yeast RAP1 protein.

The 827 amino acid yeast RAP1 protein interacts with DNA to regulate gene expression at numerous unrelated loci in the yeast genome. By a combination of amino, carboxy and internal deletions, we have defined an internal 235 amino acid fragment of the yeast RAP1 protein that can bind efficiently to the RAP1 binding site of the PGK Upstream Activation Sequence (UAS). This domain spans residues 361 to 596 of the full length protein and lacks any homology to the DNA binding 'zinc finger' or 'helix-turn-helix' structural motifs. All the RAP1 binding sites we have tested bind domain 361-596, arguing that RAP1 binds all its chromosomal sites via this domain. The domain could not be further reduced in size suggesting that it represents the minimal functional DNA binding domain. The relevance of potential regions of secondary structure within the minimal binding domain is discussed.

Base Sequence↗
PubMed1989

Characterization of the transcriptional potency of sub-elements of the UAS of the yeast PGK gene in a PGK mini-promoter.

The upstream activator (UAS) of the yeast PGK gene comprises three different sequence elements. These are 1) a region of strong protein binding called the YFP, 2) three repeats of the motif CTTCC and 3) an essential activator core (AC) sequence that binds the protein RAP1. To assess the function of each of these elements in transcriptional activation we have inserted them individually and in various combinations into a PGK mini-promoter. This comprises only the transcription initiation elements from the PGK promoter and is inactive in the absence of activator sequences. None of the individual sequence elements was capable of activating the mini-promoter. However either the YFP or the CTTCC boxes in conjunction with the AC box resulted in efficient expression. Transcription levels were not however as high as when all three elements were inserted. These data suggest that the efficiency of PGK transcription depends upon the interactions between three different sequences. Furthermore while RAP1 per se is not a transcriptional activator it can associate promiscuously with other factors to create a functional transcription complex.

Base Sequence↗
PubMed1989

HIV-1 TAT "activates" presynthesized RNA in the nucleus.

Replication of the human immunodeficiency virus (HIV-1) depends upon the viral TAT protein. TAT stimulates gene expression via a target response sequence (TAR) located within the HIV-1 LTR. As TAR is located in the transcribed region it could act as a signal in either the DNA, the RNA, or both. To test whether TAT acts on transcription and/or posttranscriptionally, we produced TAT in yeast and monitored its activity after microinjection into the nucleus or cytoplasm of Xenopus oocytes. The TAT protein stimulated TAR-dependent expression, but this activation was not inhibited by transcriptional inhibitors. Furthermore, TAR-containing RNA, produced in vitro, was "activated" by TAT after coinjection into oocytes. This activation only occurred, however, when the RNA was injected into the nucleus and not into the cytoplasm. Our data indicate, therefore, that in the Xenopus system TAT acts on presynthesized RNA and that the nucleus is involved in this action.

Animals↗
PubMed1989

Transcriptional control of the Saccharomyces cerevisiae PGK gene by RAP1.

The promoter of the yeast glycolytic gene encoding phosphoglycerate kinase (PGK) contains an upstream activation sequence between bases -538 and -402 upstream of the initiating ATG. The upstream activation sequence contains multiple functional elements, including an essential region called the activator core (AC) sequence and three copies of the pentamer 5'-CTTCC-3'. The AC sequence shows strong homology to the consensus binding sites for the yeast proteins RAP1 (GRF1) and TUF. We have demonstrated that the yeast protein which interacts with the AC sequence is the DNA-binding protein RAP1. Expression of the PGK gene is found to be regulated according to the carbon source in the growth medium. PGK mRNA levels are high in yeast cells grown in glucose medium but low in yeast cells grown in media containing carbon sources such as pyruvate and acetate. This carbon source regulation of transcription was found to be mediated, in part, via regulation of RAP1 binding to the AC sequence. The promoters of many other yeast glycolytic genes also contain consensus RAP1-binding sites and copies of the CTTCC pentamer. This suggests that RAP1 may be involved in transcriptional control of many other glycolytic genes in addition to the PGK gene.

Antibodies↗
PubMed1989

Comparison of a lactose-free formulation of sodium cromoglycate and sodium cromoglycate plus lactose in the treatment of asthma.

A double-blind, parallel group, 7-centre trial was carried out to compare the clinical efficacy and patient acceptability of two formulations of sodium cromoglycate for inhalation in patients suffering from asthma. Each single-dose capsule for use in a breath-actuated inhaler contained either a blend of sodium cromoglycate (20 mg) plus lactose (20 mg) or a lactose-free pelletized formulation of sodium cromoglycate (20 mg). Data were summarized from 529 asthmatic patients who had been using the blend formulation for at least 3 months previously. Two hundred and sixty-five patients then received pelletized sodium cromoglycate and 264 patients remained on sodium cromoglycate plus lactose for at least 3 months. Regular assessments were made by patients and clinicians during the trial period of treatment effectiveness. No clinically significant differences were observed between the two formulations after 3 months on test treatment. After a treatment period of 6 months, the pelletized formulation was shown to have some advantages over the blend formulation which were not observed at 3 months, with a significantly higher proportion of 'very effective' assessments being recorded by both patients and clinicians. The capsules of pelletized sodium cromoglycate required significantly less inhalations to empty compared to the capsules of the blend. No differences were observed between the two formulations with regard to the incidence of transient cough and throat irritation after inhalation.

Adolescent↗
PubMed1988

The UAS of the yeast PGK gene is composed of multiple functional elements.

The UAS (upstream activator sequence) of the yeast PGK gene contains a transcriptional activator domain located between bases -479 and -402 upstream from the initiating ATG. This region of the UAS contains three direct repeats of the sequence 5'CTTCC3'. The roles in transcriptional activation of these repeats and other sequences within the activator domain were investigated. When short regions containing the repeats were removed PGK expression was considerably reduced, the magnitude of the effect depended upon which CTTCC block was absent. Sequences between -473 and -458 which did not contain a CTTCC block were also shown to be necessary for high levels of PGK expression. A DNA fragment containing activator sequences up to -473 was shown to interact specifically in vitro with a yeast nuclear protein extract. DNase I footprinting identified a protected region between -473 and -458 and single base changes in DNase I sensitivity at the CTTCC repeats.

Chromosome Deletion↗
PubMed1988

Molecular cloning and chromosomal localization of a gene coding for human cardiac myosin heavy-chain.

A human cardiac myosin heavy-chain (MHC) gene, cloned in a charon 4A phage, was isolated using two rat cardiac pCMHC DNA clones (pCMHC26: alpha-MHC type; and pCMHC5: beta-MHC type) as probes and shown to correspond to cardiac myosin heavy-chain of the alpha-type. The 4.3-KB cardiac genomic DNA clone was used as a probe in the Southern analysis of human genomic DNA from human-Chinese hamster or human-mouse somatic cell hybrids. The results show that the human cardiac MHC gene is assigned to chromosome 14 and the human cardiac and skeletal MHC genes do not cosegregate as do the mouse cardiac and skeletal MHC genes.

Chromosome Mapping↗
PubMed1988

RNA 3' cleavage and polyadenylation in oocytes and unfertilized eggs of Xenopus laevis.

Xenopus laevis histone H4 and H1 genes were transcribed in vitro to generate artificial precursor mRNAs (pre-mRNAs). These pre-mRNAs were microinjected into oocytes, matured oocytes, and unfertilized eggs of Xenopus laevis and their 3' cleavage and polyadenylation were investigated. In the oocyte nucleus both H4 and H1 pre-mRNAs were 3' cleaved but were not detectably polyadenylated. In the oocyte cytoplasm there was neither 3' cleavage nor polyadenylation of these histone pre-mRNAs. When injected into either matured oocytes or unfertilized eggs, the pre-mRNAs underwent 3' cleavage but this was inefficient when compared to the oocyte nucleus. In addition approximately 50% of the remaining uncleaved pre-mRNA was subject to a polyadenylation activity which added A tails of approximately 70 A residues. In contrast, artificial mouse beta-globin pre-mRNAs were not detectably 3' cleaved or polyadenylated in either microinjected oocytes or unfertilized eggs.

Animals↗