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Biomedical subjects

C Pritchard

Publications and source records attributed to C Pritchard.

At least 19 recordsLinked to original sources
PubMed2001

MEK kinase activity is not necessary for Raf-1 function.

Raf-1 protein kinase has been identified as an integral component of the Ras/Raf/MEK/ERK signalling pathway in mammals. Activation of Raf-1 is achieved by RAS:GTP binding and other events at the plasma membrane including tyrosine phosphorylation at residues 340/341. We have used gene targeting to generate a 'knockout' of the raf-1 gene in mice as well as a rafFF mutant version of endogenous Raf-1 with Y340FY341F mutations. Raf-1(-/-) mice die in embryogenesis and show vascular defects in the yolk sac and placenta as well as increased apoptosis of embryonic tissues. Cell proliferation is not affected. Raf-1 from cells derived from raf-1(FF/FF) mice has no detectable activity towards MEK in vitro, and yet raf-1(FF/FF) mice survive to adulthood, are fertile and have an apparently normal phenotype. In cells derived from both the raf-1(-/-) and raf-1(FF/FF) mice, ERK activation is normal. These results strongly argue that MEK kinase activity of Raf-1 is not essential for normal mouse development and that Raf-1 plays a key role in preventing apoptosis.

Animals↗
PubMed1992

Recognition of the high affinity binding site in rev-response element RNA by the human immunodeficiency virus type-1 rev protein.

The Human Immunodeficiency Virus type-1 rev protein binds with high affinity to a bubble structure located within the rev-response element (RRE) RNA in stemloop II. After this initial interaction, additional rev molecules bind to the RRE RNA in an ordered assembly process which requires a functional bubble structure, since mutations in the bubble sequence that reduce rev affinity block multiple complex formation. We have used synthetic chemistry to characterize the interaction between rev protein and its high affinity binding site. A minimal synthetic duplex RNA (RBC6) carrying the bubble and 12 flanking base pairs is able to bind rev with 1 to 1 stoichiometry and with high affinity. When the bubble structure is inserted into synthetic RNA molecules carrying longer stretches of flanking double-stranded RNA, rev forms additional complexes resembling the multimers observed with the RRE RNA. The ability of rev to bind to RBC6 analogues containing functional group modifications on base and sugar moieties of nucleoside residues was also examined. The results provide strong evidence that the bubble structure contains specific configurations of non-Watson--Crick G:G and G:A base pairs and suggest that high affinity recognition of RRE RNA by rev requires hydrogen bonding to functional groups in the major groove of a distorted RNA structure.

Bacteriophage T7↗
PubMed1992

Truancy and illegal drug use, and knowledge of HIV infection in 932 14-16-year-old adolescents.

In a sample of 932 4th & 5th year comprehensive school adolescents, 41% had truanted in the current term. The truants, compared with their non-truanting peers, had three times the level of solvent misuse (14% compared with 4%), thrice the soft drug misuse (19% compared with 6%), and four times the involvement with hard drugs (9% compared with 2%). Truants were significantly more involved with other problematic behaviour and were found to score higher on all negative social indices, including parents who smoked. Despite the sample's relatively accurate knowledge about drugs and HIV infection, truants scored less well on these and other HIV-related issues. An extrapolation of the results indicates a significant number of adolescents at risk demanding urgent policy initiatives.

Acquired Immunodeficiency Syndrome↗
PubMed1992

Is there a link between suicide in young men and unemployment? A comparison of the UK with other European Community Countries.

Within the context of marked increases in suicide rates in the UK among men between 1974 and 1988, the rate among those aged 15-24 years rose more than that of any other age band. The UK suicide rate among young men also worsened compared with those of most other countries in the EC. Rises in the general male suicide rate were statistically associated with rises in unemployment in most of the EC.

Adolescent↗
PubMed1992

Youth suicide and gender in Australia and New Zealand compared with countries of the Western world 1973-1987.

Based upon standardised mortality figures, between 1973-1987, Australian male suicide rose by 39%, and New Zealand male suicide by 53%. In both countries there were even greater increases in male youth suicides (15-24 years), 66% and 127% respectively. The female suicide statistics were more varied with a fall of -24% in Australia, but an increase of 26% in New Zealand. In both countries however, female youth suicide, relative to their general rates, increased. A comparison of youth suicide in the western world demonstrated that Australia and New Zealand were unique as they were the only countries in which male and female youth suicide levels were higher than their average rates.

Adolescent↗
PubMed1992

Recombination of 4p16 DNA markers in an unusual family with Huntington disease.

The Huntington disease (HD) mutation has been localized to human chromosome 4p16, in a 6-Mb region between the D4S10 locus and the 4p telomere. In a report by Robbins et al., a family was identified in which an affected individual failed to inherit three alleles within the 6-Mb region originating from the parental HD chromosome. To explain these results, it was suggested that the HD locus (HD) lies close to the telomere and that a recombination event took place between HD and the most telomeric marker examined, D4S90. As a test of this telomere hypothesis, we examined six members of this family, five of whom are affected with HD, for the segregation of 12 polymorphic markers from 4p16, including D4S169, which lies within 80 kb of the 4p telomere. We separated, in somatic cell hybrids, the chromosomes 4 from each family member, to determine the phase of marker alleles on each chromosome. We excluded nonpaternity by performing DNA fingerprint analyses on all six family members, and we found no evidence for chromosomal rearrangements when we used high-resolution karyotype analysis. We found that two affected siblings, including one of the patients originally described by Robbins et al., inherited alleles from the non-HD chromosome 4 of their affected parents, throughout the 6-Mb region. We found that a third affected sibling, also studied by Robbins et al., inherited alleles from the HD chromosome 4 of the affected parent, throughout the 6-Mb region. Finally, we found that a fourth sibling, who is likely affected with HD, has both a recombination event within the 6-Mb region and an additional recombination event in a more centromeric region of the short arm of chromosome 4. Our results argue against a telomeric location for HD and suggest that the HD mutation in this family is either associated with DNA predisposed to double recombination and/or gene conversion within the 6-Mb region or is in a gene that is outside this region and that is different from that mutated in most other families with HD.

Adult↗
PubMed1991

Identification of molecular contacts between the U1 A small nuclear ribonucleoprotein and U1 RNA.

We recently determined the crystal structure of the RNP domain of the U1 small nuclear ribonucleoprotein A and identified Arg and Lys residues involved in U1 RNA binding. These residues are clustered around the two highly conserved segments, RNP1 and RNP2, located in the central two beta strands. We have now studied the U1 RNA binding of mutants where potentially hydrogen bonding residues on the RNA binding surface were replaced by non-hydrogen bonding residues. In the RNP2 segment, the Thr11----Val and Asn15----Val mutations completely abolished, and the Tyr13----Phe and Asn16----Val mutations substantially reduced the U1 RNA binding, suggesting that these residues form hydrogen bonds with the RNA. In the RNP1 segment Arg52----Gln abolished, but Arg52----Lys only slightly affected U1 RNA binding, suggesting that Arg52 may form a salt bridge with phosphates of U1 RNA. Ethylation protection experiments of U1 RNA show that the backbone phosphates of the 3' two-thirds of loop II and the 5' stem are in contact with the U1 A protein. The U1 A protein-U1 RNA binding constant is substantially reduced by A----G and G----A replacements in loop II, but not by C----U or U----C replacements. Based on these biochemical data we propose a structure for the complex between the U1 A ribonucleoprotein and U1 RNA.

Base Sequence↗
PubMed1991

Synthesis of site-specifically modified oligoribonucleotides for studies of the recognition of TAR RNA by HIV-1 tat protein and studies of hammerhead ribozymes.

Synthetic oligoribonucleotides having single uracil residues replaced by dU, dT, 2'-O-methylU or 5-bromodU have been prepared and used in the study of the interaction of HIV-1 tat protein with an RNA stem-loop. The preparation of phosphoramidites of 5-bromouridine and purine riboside suitable for use in solid-phase oligoribonucleotide synthesis is also described. The effect of adenine replacement by purine in a hammerhead ribozyme has also been determined.

Base Sequence↗
PubMed1990

Suicide, unemployment and gender variations in the Western world 1964-1986. Are women in Anglo-phone countries protected from suicide?

The gender related suicide and unemployment rates for 1964-1986 from twenty-three Western countries were reviewed. A statistically significant correlation was found for both genders for the 1974-1986 period, which saw major rises in both suicide and unemployment in many Western nations. This was in contrast to a non-significant correlation for 1964-1973. As unemployment reached a critical level the statistical link with suicide became stronger. This suggests that unemployment is a contributing factor in increased suicide. Major gender changes occurred, in particular rises in female suicide rates, though these were not uniform. Whilst the expected greater male/female ratio for suicide was confirmed, there were significant variations between countries, with the ratio widening particularly amongst anglo phone nations. This indicated differential gender changes in patterns of suicide. The possibility of some 'protective' mechanism against suicide for women in anglo phone countries is discussed.

Adult↗
PubMed1990

Drug and solvent misuse and knowledge of HIV infections in 14-16-year-old comprehensive school students.

This study of drug and solvent misuse and knowledge of the HIV link amongst 934 secondary school students, completes a third survey concerned with prevalence of drug misuse. Drug and/or solvent misuse was found in 16% of the sample including 5% who use hard drugs, which since 1985 represents a 3% decline, but a 1% increase in the use of hallucinogens. The misusers were compared with the non-users with regard to their social characteristics, other illegal behaviour and their knowledge of HIV and other public health concerns. There were some surprises concerning the gender results. Misusers were found to be more socially disadvantaged and more involved in other negative behaviour. Despite reasonable knowledge about HIV-related matters, the misuser group were less accurate on all public health issues, appearing to 'deny' the potential risks associated with drug misuse.

Acquired Immunodeficiency Syndrome↗
PubMed1990

A cloned DNA segment from the telomeric region of human chromosome 4p is not detectably rearranged in Huntington disease patients.

Genetic linkage studies have mapped the Huntington disease (HD) mutation to the distal region of the short arm of human chromosome 4. Analysis of recombination events in this region has produced contradictory locations for HD. One possible location is in the region distal to the D4S90 marker, which is located within 300 kilobases of the telomere. Other crossover events predict a more centromeric position for HD. Here we analyze the telomeric region of 4p in detail. Cloned DNA segments were derived from this region by utilizing a radiation-induced somatic cell hybrid as a source of DNA combined with preparative pulsed-field gel electrophoresis to enrich for the telomeric fraction. Additional DNA was obtained by using the cloned segments as multiple start points for cosmid walks. This strategy proved to be an effective method for cloning 250 kilobases of DNA in the region telomeric to D4S90. Hybridization analysis with the cloned DNA did not provide any evidence for the presence of rearrangements of 100 base pairs or greater in the DNA of individuals affected with HD. We also found no change in the size or structure of the 4p telomere in these samples.

Animals↗
PubMed1989

Comparisons between the self-assessed and observer-assessed presence and severity of colds.

The hypotheses that self-reported symptoms are a valid proxy for physicians' ratings, and that people with different social characteristics may vary in their recognition and evaluation of symptoms, were tested on volunteers attending the MRC Common Cold Unit. Eleven-hundred volunteers assessed the presence and severity of colds at the end of their stay at the unit, using the same two measures as a trained clinical observer (all ratings were double blind). On both measures there was an extremely high correlation between self- and observer-assessments, a finding encouraging for those using self-reports in community surveys. Although this high level of agreement was found within all the age, sex, occupational class and marital status groups, men were significantly more likely than women to over-rate their symptoms in comparison with the clinical observer. No such differences in over-rating were found by age, class or marital status. This finding of a sex difference in the tendency to over-rate physical symptoms is of major significance to theories of illness behaviour, and is particularly convincing because it is based on a double-blind comparison between self-reports and assessments made by a doctor.

Adolescent↗
PubMed1988

MIC2: a human pseudoautosomal gene.

MIC2 and XGR are the only known pseudoautosomal genes in man. MIC2 encodes the 12E7 antigen, a human cell-surface molecule of unknown function. XGR regulates, in cis, the expression of the XG and MIC2 genes. DNA probes derived from the MIC2 locus have been used in the construction of a meiotic map of the pseudoautosomal region and a long range restriction map into the X- and Y-specific chromosome domains. MIC2 is the most proximal marker in the pseudoautosomal region and recombination between the sex chromsomes only rarely includes the MIC2 locus. Our long-range restriction maps and chromosome walking experiments have localized the pseudoautosomal boundary within 40 kilobases adjacent to the 3' end of the MIC2 gene. The same maps have been used to predict the chromosomal location of TDF.

Amino Acid Sequence↗