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Biomedical subjects

G R Smith

Publications and source records attributed to G R Smith.

At least 127 records · Page 7Linked to original sources
PubMed1995

Active and inactive transplacement of the M26 recombination hotspot in Schizosaccharomyces pombe.

The ade6-M26 mutation of the fission yeast Schizosaccharomyces pombe creates a meiotic recombination hotspot that elevates ade6 intragenic recombination approximately 10-15-fold. A heptanucleotide sequence including the M26 point mutation is required but not sufficient for hotspot activity. We studied the effects of plasmid and chromosomal context on M26 hotspot activity. The M26 hotspot was inactive on a multicopy plasmid containing M26 embedded within 3.0 or 5.9 kb of ade6 DNA. Random S. pombe genomic fragments totaling approximately 7 Mb did not activate the M26 hotspot on a plasmid. M26 hotspot activity was maintained when 3.0-, 4.4-, and 5.9-kb ade6-M26 DNA fragments, with various amounts of non-S. pombe plasmid DNA, were integrated at the ura4 chromosomal locus, but only in certain configurations relative to the ura4 gene and the cointegrated plasmid DNA. Several integrations created new M26-independent recombination hotspots. In all cases the non-ade6 DNA was located > 1 kb from the M26 site, and in some cases > 2 kb. Because the chromosomal context effect was transmitted over large distances, and did not appear to be mediated by a single discrete DNA sequence element, we infer that the local chromatin structure has a pronounced effect on M26 hotspot activity.

Chromosomes, Fungal↗
PubMed1995

An intron-containing meiosis-induced recombination gene, rec15, of Schizosaccharomyces pombe.

Mutations in the rec15 gene of Schizosaccharomyces pombe reduce meiotic recombinant frequencies, in the three intervals tested, as much as 1000-fold but have no detectable mitotic phenotype. The rec15 gene was mapped to within 1 cM of mat1. The gene was cloned by genetic complementation and its nucleotide sequence determined. Deletion analysis and gene replacement confirmed that the clones contained the rec15 gene on DNA fragments as short as 1.3 kb. The nucleotide sequence of the 1.3 kb fragment predicted that rec15 had a 49 bp intron separating two exons encoding a 180-amino-acid polypeptide product. This predicted intron was confirmed by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. During thermally induced meiosis in a pat1-114 (Ts) mutant, the rec15 transcripts were induced to maximal levels at 2-3h but were present at much lower levels before and after this time. The transient induction of the transcripts and the phenotype of a rec15 null (deletion) mutation suggest that the rec15 gene product is required during the early stages of meiosis for meiotic recombination.

Amino Acid Sequence↗
PubMed1995

The process and outcomes of care for major depression in rural family practice settings.

Although primary care physicians provide the majority of care for rural residents with major depression, little is known about the quality of the care they provide. The aim of this study was to characterize the process and outcomes of care for rural patients with major depression, and to examine the relationship between the process and outcomes of care in this population. Six hundred and thirty-one patients in 21 primary care practices in small towns were screened; 47 patients (7.4% of patients screened) meeting DSM-III-R criteria for current major depression were recruited into the study, and 38 (81.0% of patients recruited) were followed an average of five months later using the Depression Outcomes Module (Rost, Smith, Burnam, & Burns, 1992). While 24 (63.1%) of the 38 depressed subjects received a prescription for one or more antidepressants between the index visit and follow-up, only 11 (28.9%) received pharmacologic treatment in concordance with the new Agency for Health Care Policy and Research (AHCPR) guidelines; 26 (68.4%) of 38 depressed patients continued to meet criteria for major depression at five months. Those who received pharmacologic treatment concordant with AHCPR guidelines showed more improvement at follow-up. The findings suggest that outcomes for major depression may be worse in rural family practice settings than in urban settings. The study also demonstrates that AHCPR guidelines define effective treatment for major depression in the study sample. The Depression Outcomes Module appears to be a reliable and valid instrument for monitoring the outcomes of care for major depression in family practice settings.

Arkansas↗
PubMed1995

DSM-IV field trial: testing a new proposal for somatization disorder.

OBJECTIVE: The purpose of this study was to evaluate for APA a proposed strategy to diagnose somatization disorder for possible inclusion in DSM-IV. METHOD: Five sites--Washington University, University of Kansas, University of Iowa, University of Arkansas, and Mount Sinai Medical Center in New York--participated in a collaborative field trial. Female subjects (N = 353) were recruited from several different services (psychiatry, internal medicine, and family practice) and were evaluated for the presence or absence of the disorder. This assessment was performed with a new instrument constructed by combining all the criteria for somatization disorder from the proposed criteria for DSM-IV, DSM-III, DSM-III-R, Perley-Guze, and proposed criteria for ICD-10. RESULTS: A high level of concordance was found between the proposed diagnostic strategy for DSM-IV and the current criteria (DSM-III-R), as well as the earlier criteria (Perley-Guze and DSM-III). The ICD-10 criteria agreed poorly with all other criteria sets. The level of experience of the rater (expert versus novice) with the earlier (Perley-Guze, DSM-III) and current (DSM-III-R) criteria did not influence the identification of cases by use of DSM-IV criteria. No racial effect was introduced by any of the criteria sets. CONCLUSIONS: The strategy for DSM-IV is an accurate and simpler method of diagnosing somatization disorder that does not require special expertise for proper use.

Adult↗
PubMed1995

Workers' compensation issues in home care.

Workers' compensation expenses can add up quickly for home care agencies, where employees are in and out of patients' homes all day, often with no supervision or with no help in transferring patients or heavy equipment. Simple precautions and proper training and followup can greatly reduce this financial burden.

Back Pain↗
PubMed1995

The risks of using complex technology in home care.

New medical devices make it possible to care at home for patients who are dependent on ventilators, have cardiac problems, or need respiratory monitors, dialysis, or high-risk pregnancy monitoring. Yet this technology has also increased risks for this growing industry. Can these risks be addressed and lessened?

Caregivers↗
PubMed1995

Families who somatize.

This investigation extends a previous study of children of people with somatization disorder and children of less severely affected somatizers. We used the revised Diagnostic Interview for Children and Adolescents, revised, and abstracted medical records to compare families in which a child as well as a parent had unexplained somatic complaints; we also identified parental predictors of children's somatization. Children in families with somatizing children had more emergency room use, more suicidal behavior, and more disability. Children in families of somatization disorder adults had 11.7 times as many emergency room visits as less severely affected somatizers and missed 8.8 times as much school. Parental somatization, substance abuse, and antisocial symptoms predicted children's somatization. Physicians in primary care should be aware of the frequency with which somatization occurs in other members of a family when it is identified in one member.

Adolescent↗
PubMed1994

A heteromeric protein that binds to a meiotic homologous recombination hot spot: correlation of binding and hot spot activity.

Homologous recombination hot spots are DNA sites that increase the frequency of recombination in their vicinity. The M26 allele of the ade6 gene in Schizosaccharomyces pombe is the first meiotic hot spot with an identified unique nucleotide sequence. We have purified 40,000-fold a heteromeric protein, containing polypeptides Mts1 (70 kD) and Mts2 (28 kD), that binds to the M26 site. Binding in vitro strictly correlates with hot spot activity in vivo for numerous single base pair substitutions in the vicinity of the M26 site, indicating that Mts1/Mts2 activates the M26 site and promotes a rate-limiting step of meiotic recombination. These and other data suggest that homologous recombination may be regulated primarily by discrete DNA sites and proteins that interact with those sites.

Activating Transcription Factor 1↗
PubMed1994

Quantification of the interaction between lysolecithin and phospholipase A2.

The rate of hydrolysis of phosphatidylcholine bilayers by phospholipase A2 may be either enhanced or inhibited by the presence of lysolecithin depending on the experimental conditions examined. To further understand the relationship of lysolecithin to phospholipase A2 activity, the binding of lysolecithin to phospholipase A2 from the venom of Agkistrodon piscivorus piscivorus was examined by fluorescence spectroscopy. The tryptophan emission intensity of the enzyme was enhanced by 70% upon addition of lysolecithin. The binding isotherm for lysolecithin to the phospholipase A2 estimated from the fluorescence change was biphasic, with a clear break in the curve occurring at the critical micelle concentration of the lysolecithin. Several observations suggested that the phospholipase A2 was capable of hydrolyzing the lysolecithin although at a rate far below that of phospholipid hydrolysis. These experiments were repeated using several other species of phospholipase A2, and the results were found to be general among the enzymes except the lys-49 isozyme from A. p. piscivorus which displayed neither the dependence on the critical micelle concentration for binding nor the ability to hydrolyze lysolecithin. These results were used as the basis for a quantitative analysis of enzyme fluorescence changes that occur during the time course of phospholipid hydrolysis and of the mechanism whereby lysolecithin inhibits the hydrolysis of phosphatidylcholine bilayers by phospholipase A2.

Agkistrodon↗
PubMed1994

Hotspots of homologous recombination.

Homologous recombination occurs at higher than average frequency at and near hotspots. Hotspots are special nucleotide sequences recognized by proteins that promote, directly or indirectly, a rate limiting step of recombination. This review focuses on two well-studied examples, the Chi sites of the bacterium Escherichia coli and the M26 site of the fission yeast Schizosaccharomyces pombe. Chi, 5' G-C-T-G-G-T-G-G 3', is recognized by the RecBCD enzyme, which nicks the DNA near Chi and produces a 3'-ended single-stranded DNA 'tail'; this tail is a potent substrate for homologous pairing by RecA and single-stranded DNA binding proteins. M26, 5' A-T-G-A-C-G-T 3', is recognized by a heterodimeric protein and stimulates, by an as-yet-unknown mechanism, meiotic recombination at and near the ade6 gene. Additional hotspots in bacteria, fungi, and mammals enhance recombination directly or indirectly via a variety of mechanisms. Although hotspots are widespread among organisms, the biological role of their localized enhancement of recombination remains a matter of speculation.

Binding Sites↗
PubMed1994

Decontamination studies with the agents of bovine spongiform encephalopathy and scrapie.

Macerates of bovine brain infected with bovine spongiform encephalopathy (BSE) agent, and rodent brain infected with the 263K or ME7 strains of scrapie agent, were subjected to porous-load autoclaving at temperatures between 134 and 138 degrees C for < or = 60 min. Bioassay in rodents showed that none of the regimens produced complete inactivation. Homogenates of BSE-infected bovine brain were exposed for < or = 120 min to solutions of sodium hypochlorite or sodium dichloroisocyanurate containing < or = 16,500 ppm available chlorine. There was no detectable survival of infectivity after the hypochlorite treatments but none of the dichloroisocyanurate solutions produced complete inactivation. Homogenates of BSE-infected bovine brain, and rodent brain infected with the 263K and ME7 strains of scrapie agent, were exposed for < or = 120 min to 1M or 2M sodium hydroxide but no procedure produced complete inactivation of all agents tested.

Animals↗
PubMed1994

Chemiluminescent detection of Fiji disease virus with biotinylated DNA probes.

Biotinylated Fiji disease fijivirus specific cDNA probes detected the presence of the virus in total nucleic acid extracts from infected sugarcane plants. Hybridised biotinylated probes were detected with streptavidin-alkaline phosphatase conjugate and the light generating substrate AMPPD. Samples were either blotted manually, or by alkaline capillary transfer using 100 mM NaOH. Transfer of nucleic acids to charge modified nylon with sodium hydroxide was superior to denaturation with glyoxal or formamide and salt-citrate buffer transfer as the bands were clearly resolved and no degradation of the FDV dsRNA was observed. Transfer of either total nucleic acid extracts or purified dsRNA in manifold blots generated false positive signals with the non-radio-active chemiluminescent detection systems tested. Manual or northern blots had a limit of detection for purified target double-stranded RNA of approximately 10 pg and 0.5 pg respectively. Manual blots were tested for practical application to screen germplasma for FDV infection. The virus was detected in leaf samples from FDV-infected plants, in some instances prior to development of the characteristic gall symptom.

Biotin↗
PubMed1994

The production of Clostridium botulinum type A, B and D toxin in rotting carcasses.

Carrion is a major source of botulinal toxin for animals. A type D strain of Clostridium botulinum differed from type A and B strains in producing (1) much higher concentrations of toxin in putrefying mouse carcasses at several different temperatures over a period of 35 days, (2) toxicity that sometimes persisted in mouse carcasses for at least a year, and (3) mouse carcasses with exceptionally high oral toxicity. Fish carcasses were much less favourable than mouse carcasses for type D toxigenesis. The study, together with earlier studies on types C and E, indicated that carrion contaminated with C. botulinum type C or D is likely to be particularly dangerous for animals that may ingest it. This accords with the observation that carrion-transmitted botulism in animals is usually caused by type C or D.

Animals↗
PubMed1994

Landfill sites, botulism and gulls.

Botulism due to Clostridium botulinum type C causes considerable mortality in gulls in the UK, and refuse disposal sites are suspected as a major source of toxin. C. botulinum types B, C and D were each found in 12 (63.2%) of 19 landfill sites examined. Type E was detected in only one (5.2%) and types A, F and G were not found. The prevalence of type C spores was much higher than that demonstrated in the UK environment by earlier surveys. The presence of these spores, together with the rotting organic matter and generated heat associated with landfill sites, undoubtedly leads to bacterial proliferation and toxigenesis. This is likely to result in botulism in scavenging gulls unless skilled landfill management prevents the ingestion of toxic material. Type D spores were previously shown to be rare in the UK environment and their high prevalence on landfill sites was therefore surprising. Four composite samples of refuse collected before distribution on a landfill gave negative results for C. botulinum and it seems likely that the gulls themselves play a major role in introducing contamination.

Animals↗
PubMed1994

Transient, meiosis-induced expression of the rec6 and rec12 genes of Schizosaccharomyces pombe.

Two meiotic recombination genes, rec6 and rec12, from Schizosaccharomyces pombe have been cloned by genetic complementation and their DNA sequences determined. Gene replacements demonstrated that the cloned fragments contained the rec6 and rec12 genes. Further analysis showed that the functional rec6 gene was within a 1.3-kb fragment and rec12 within a 1.7-kb fragment. The nucleotide sequences of these fragments revealed open reading frames (ORFs) predicting 143 amino acids for the rec6 gene product and 139 amino acids for the rec12 gene product. After pat1-114 temperature-induced meiosis, the transcripts of rec6 and rec12 were induced to maximal levels at 2-3 hr, at about the time of premeiotic DNA synthesis, but were present at much lower levels before and after this time. The transient induction of the transcripts and the phenotypes of the mutants suggest that the rec6 and rec12 gene products are involved primarily in the early steps of meiotic recombination in S. pombe. Near the rec6 gene are two additional ORFs potentially encoding proteins with homology to ribosomal protein S7 of Saccharomyces cerevisiae (ORF137) and to the homeodomain of developmental regulatory proteins (ORF201). The roles of these S. pombe ORFs remain to be determined.

Amino Acid Sequence↗
PubMed1994

Region-specific activators of meiotic recombination in Schizosaccharomyces pombe.

Schizosaccharomyces pombe rec mutants were previously isolated on the basis of their deficiency in meiotic recombination at the ade6 locus. We surveyed their meiotic recombination deficiencies at and between other loci. In rec10 mutants recombinant frequencies in the approximately 2-Mb region surrounding the ade6 locus were reduced 10- to 100-fold, but recombinant frequencies at or between nine other unlinked loci were reduced < 3-fold. The rec10 mutations are recessive and are on chromosome I; the ade6 region is on chromosome III. These results indicate that the rec10 gene product is required for activation of meiotic recombination in the approximately 2-Mb region surrounding ade6 but not in the other regions surveyed. Similar ade6 regional specificities were observed for rec8 and rec11. We infer that there are multiple activators of meiotic recombination, each specific for a limited set of loci, and we discuss how these regional activators may work.

Chromosomes, Fungal↗