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Biomedical subjects

P Barrett

Publications and source records attributed to P Barrett.

At least 109 records · Page 6Linked to original sources
PubMed1989

Sexual problems in the elderly.

This article looks at sexual distress in the elderly and describes a case history which shows how fear can interfere with normal sexual relationships.

Aged↗
PubMed1987

An alternative protein factor which binds the internal promoter of Xenopus 5S ribosomal RNA genes.

In small oocytes of Xenopus species, two sets of 5S RNA genes, oocyte-type and somatic-type, are fully activated. The 5S RNA transcripts are temporarily stored, half in association with TFIIIA to form a 7S particle, the other half in association with tRNA and two proteins (p48 and p43) to form a 42S particle. It has been established previously that TFIIIA binds to the internal control region of 5S RNA genes and promotes their transcription. Here we show that protein can be translocated from the 42S particles to 5S RNA genes, but only after treatment of the particles with ribonuclease. Nevertheless, once transferred, stable protein-DNA complexes are formed and DNase-protection experiments show that binding is specific to the gene promoter, covering exactly the same sequence as TFIIIA. The DNA-binding protein is identified as p48 which, after isolation by ion-exchange chromatography, will bind to 5S RNA genes in the absence of ribonuclease.

Animals↗
PubMed1987

Phosphorylation of a 60 kDa polypeptide from Xenopus oocytes blocks messenger RNA translation.

The stored mRNP particles of Xenopus oocytes contain protein kinase activity and two major phosphoproteins of 60 kDa (pp60) and 56 kDa (pp56). These proteins can be phospholabelled in the particles either in vivo or in vitro and then isolated by SDS-PAGE. On renaturing pp60 in the presence of globin mRNA, a stable RNA-protein complex is formed. The complex has a uniform density in Cs salt gradients, corresponding to the binding of about 10 protein molecules to each mRNA, probably at the poly(A) sequence. Compared with uncomplexed mRNA, the RNP complex is translated poorly both in vitro and in vivo. Translation of the complex can be regained after treatment with protein phosphatase. It is shown that dephosphorylation destabilizes the binding of protein to RNA, making the mRNA accessible for translation. Studies with native mRNP particles show that their translation also can be enhanced by dephosphorylation.

Animals↗
PubMed1987

A cellular protein binds to a conserved sequence in the adenovirus type 2 enhancer.

A sensitive gel retention assay has been utilized to detect proteins from uninfected Hela nuclei which interact with the adenovirus type 2 enhancer. This assay has been employed to monitor fractionation of nuclear extracts. Three enhancer binding factors were resolved by chromatography on DEAE-Sepharose and one of the factors was further purified by chromatography on heparin-Sepharose. DNase protection experiments have shown that the heparin-Sepharose fraction contains a factor which binds predominantly to the conserved sequence GTGGAAATTT present at position 160 in the adenovirus type 2 genome and found in many viral and cellular enhancers. Protection of this sequence from DNase I digestion was abolished by competition with a synthetic duplex oligonucleotide spanning bases 144-181. This region corresponds to the sequence defined by Hen et al. as possessing enhancer function. Competition experiments indicated that the enhancer binding factor also bound, albeit with reduced affinity, to multiple sites in the Ela upstream region located between positions 192 and 353. Within the sequences which compete are regions with homology to the high affinity site at position 160. The enhancer binding factor also binds with high affinity to sequences within the SV40 enhancer demonstrating that this factor interacts with sequences common to both the adenovirus and SV40 enhancers.

Adenoviruses, Human↗
PubMed1987

Calcium in the regulation of aldosterone secretion and vascular smooth muscle contraction.

A model of angiotensin II action has been developed in which the flow of information from cell surface to cell interior proceeds by two temporally distinct branches: a calmodulin branch largely responsible for initiating the response; and a C-kinase branch for sustaining it. There are at least two initial events: a prompt and sustained increase in calcium influx rate, and prompt hydrolysis of phosphatidylinositol 4,5-bisphosphate. The latter leads to the generation of water-soluble inositol 1,4,5-trisphosphate and lipid soluble diacylglycerol. The rise in inositol 1,4,5-trisphosphate concentration causes the redistribution of intracellular calcium, a transient rise in the calcium concentration in the cytosol, and the activation of calmodulin-dependent enzymes, including protein kinase(s). As a result, several cellular proteins are rapidly phosphorylated and initiate the cellular response. The rise in calcium and these initial phosphorylation events are transient, however, so that an additional mechanism is necessary to sustain the response. The rise in diacylglycerol content, along with the transient rise in cytosolic calcium, leads to a shift of the C-kinase from a calcium-insensitive to a calcium-sensitive, plasma membrane-associated form. In this location, the activity of C-kinase is regulated by the rate of calcium flux across the plasma membrane. As a result of the activity of the C-kinase, a second set of cellular proteins becomes phosphorylated, and these control the sustained phase of the response.

Adrenocorticotropic Hormone↗
PubMed1987

The relationship between agoraphobia, social phobia and blood-injury phobia in phobic and anxious-depressed patients.

This paper reports the results of principal components and stepwise discriminant analyses of anxiety, depression and fear scores for 74 phobic and anxious-depressed psychiatric patients. Factor analysis indicated a coherent agoraphobia factor, with less coherent blood-injury and social phobia factors. Discriminant analysis showed a high degree of correct classification of diagnosed agoraphobic, blood-injury and social phobic patients particularly for agoraphobia. A frequency distribution of the phobia scores indicated an all or nothing quality to agoraphobic fears. The results indicate that agoraphobia is a fairly coherent syndrome, but that more work is needed on the concepts and measurement of blood-injury and social phobias.

Adult↗
PubMed1987

The role of sequence-specific DNA-binding proteins in adenovirus DNA replication.

In prokaryotes it is well established that proteins which recognise defined DNA sequences are involved in the control of gene expression and replication. Cellular proteins in eukaryotes which may perform a similar function have been identified by their interactions with control regions of the human adenovirus genome. Immediately after infection a small region (E1a) at the left end of the adenovirus genome is expressed. Proteins coded by the E1a region transcriptionally activate the viral early genes. The products of a number of these early genes are directly involved in replication of the viral DNA. DNA sequences which are required for efficient E1a transcription and for the initiation of DNA replication have been identified by mutational analysis. Cellular proteins which recognise these sequences were detected using a sensitive gel retention assay. The basis of this assay is that during electrophoresis DNA-protein complexes migrate more slowly through a polyacrylamide gel than free DNA. In this way a cellular protein which binds to a conserved sequence in the adenovirus enhancer has been identified and partially purified. Cellular proteins which bind to adenovirus type 2 and 4 origins of replication have also been fractionated from nuclear extracts of uninfected HeLa cells. The roles of these proteins in adenovirus replication will be discussed.

Adenoviridae↗
PubMed1985

Identification of a 60-kDa phosphoprotein that binds stored messenger RNA of Xenopus oocytes.

Rapidly labelled, polyadenylated RNA is contained in three distinct fractions isolated from homogenized amphibian oocytes: (a) in ribonucleoprotein particles that are associated with a fibrillar matrix, the complexes sedimenting at greater than 1500S; (b) in ribonucleoprotein particles that sediment at 20-120S and have the characteristics of stored (maternal) messenger ribonucleoprotein (mRNP) and (c) in polyribosomes that sediment at 120-360S. We have compared the RNA and protein components of the first two of these RNP fractions. The polyadenylated RNA extracted from the two RNP fractions differs in that the RNA from fibril-associated RNP contains a much higher content of repeat sequences than does the RNA from mRNP. In other words, the RNA from fibril-associated RNP is largely unprocessed and may constitute a premessenger state, which for convenience is referred to as premessenger RNP (pre-mRNP). RNA-binding experiments demonstrate that the polypeptide most tightly bound in pre-mRNP is a 54-kDa component (p54), whereas the polypeptide most tightly bound in mRNP is a 60-kDa component (p60). Antibodies raised against p60 are used to show that this polypeptide is a common major component of pre-mRNP and mRNP and that it is also located in oocyte nuclei. However the state of p60 is modified between the premessenger and stored message levels: the polypeptide in mRNP is heavily phosphorylated whereas the equivalent polypeptide in pre-mRNP is completely unphosphorylated. The relative roles of the presence of repeat sequences and phosphorylation of mRNA-associated protein in blocking translation are discussed.

Animals↗
PubMed1984

Distribution and utilization of 5 S-RNA-binding proteins during the development of Xenopus oocytes.

At early stages of oogenesis in Xenopus laevis most of the ribosomal 5S RNA is complexed with three proteins to form two types of cytoplasmic RNP storage particle. A particle sedimenting at 42S contains 5S RNA and tRNA together with two proteins of Mr 48000 (P48) and Mr 43000 (P43) and a second particle sedimenting at 7S contains 5S RNA plus a protein of Mr 40000 (P40, also known as the transcription factor, TFIIIA). In this report we use antibodies monospecific for each protein to follow the movement of 5S RNA from nucleus to cytoplasm to nucleolus to cytoplasm and to determine the fate of each of the proteins that associate with 5S RNA during these transitions. Both P48 and P43 have roles additional to the formation of the 42S RNP storage particle; P48 is detected in the nucleus during early oogenesis and is cleaved to yield an Mr-33000 fragment that remains associated with 5S RNA that is excess to ribosome requirement during late oogenesis; P43 appears to be cleaved to yield fragments of Mr 28000 and 17000, the latter being present in ribosomal fractions. Apparently, there is no function for P40 in addition to those already described in transcription of 5S RNA genes and in storage of 5S RNA as a 7S RNP particle.

Animals↗
PubMed1984

Immunological identity of proteins that bind stored 5S RNA in Xenopus oocytes.

In small oocytes of Xenopus laevis, the three most abundant proteins are isolated as basic polypeptides with molecular weights of 48 kD (P48), 43 kD (P43) and 40 kD (P40, also known as transcription factor IIIA). All three proteins share common properties in being able to bind specifically ribosomal 5S RNA molecules and influence, in different ways, their rates of production and utilization. It has been shown by biochemical analysis and immunological characterization that the three proteins are structurally distinct and are most probably the products of different genes. Immunostaining and radio-immunoassays indicate that both P48 and P43 have diverged considerably in structure between the amphibian genera Xenopus and Triturus. Antibodies raised against the transcription factor for Xenopus laevis 5S RNA genes (P40/TFIIIA) do not cross-react with the transcription factor isolated from oocytes of the closely related species Xenopus borealis. A protein equivalent of TFIIIA is not found in 5S RNA-containing RNP storage particles of Triturus oocytes. The functions of the three Xenopus oocyte proteins in transporting 5S RNA between different cellular compartments are considered in the light of these variations.

Animals↗
PubMed1984

Age, drinking habits and the effects of alcohol.

Some explanations for the common observation that older persons drink less alcohol than younger persons were tested in a sample of 41 men social drinkers aged 19-63. Subjects reported their drinking habits and performed balance beam and bead-stringing tasks under a moderate dose of alcohol (.72 ml absolute alcohol/kg). Self-reports of dose (ml absolute alcohol/kg) on a typical social occasion, and hourly dose (which controlled for individual differences in the duration of these occasions) were found to decline linearly with age. Alcohol absorption and elimination rates in the sample were not significantly related to age. The Ponderal Index (an estimate of percentage of body water in body weight) was negatively correlated with age and with peak blood alcohol levels (BALs). Older subjects had proportionately less body water (i.e., a smaller volume for distribution of alcohol) and obtained higher BALs. When individual differences in BAL were controlled for, the amount of alcohol-induced impairment in task performance was still found to increase significantly with age. This evidence was considered to suggest that a reduction in the volume of distribution for alcohol and an intensified behavioral effect of alcohol may operate jointly to cause older persons to reduce their dose of alcohol on social drinking occasions.

Adult↗
PubMed1983

Specific interaction of proteins with 5 S RNA and tRNA in the 42 S storage particle of Xenopus oocytes.

During early oogenesis in amphibia, most of the 5 S RNA and tRNA is stored in a ribonucleoprotein particle that sediments at 42 S. In Xenopus laevis the 42 S particle contains two major proteins: of Mr 48 000 (P48) and 43 000 (P43). It is shown that heterogeneity in composition of the 42 S particle reflects a changing situation whereby initially, both 5 S RNA and tRNA are complexed with P48 (1 molecule 5 S RNA: 1 molecule P48; 2 or 3 molecules tRNA: 1 molecule P48), but later, tRNA becomes increasingly associated with P43 (in a 1:1 ratio) although 5 S RNA remains complexed with a cleavage product of P48. These changes relate to the eventual utilization of the excess 5 S RNA and tRNA in ribosome assembly and protein synthesis.

Animals↗