PubMed Health⌕ Search

Biomedical subjects

G R Smith

Publications and source records attributed to G R Smith.

At least 19 recordsLinked to original sources
PubMed1992

A single-stranded DNA exonuclease from Schizosaccharomyces pombe.

We have purified to near homogeneity a DNA exonuclease from meiotic cells of Schizosaccharomyces pombe. The enzyme, designated exonuclease II (ExoII), had an apparent molecular weight of 134,000 and was abundant in the cell. It specifically degraded single-stranded DNA in the 5'----3' direction with an apparent Km for 5' DNA ends of 3.6 x 10(-11) M and produced 5' deoxynucleoside monophosphates. Its mode of degradation is similar to that of the RecJ protein from Escherichia coli; ExoII may, therefore, be involved in genetic recombination and DNA damage repair.

Chromatography, Affinity↗
PubMed1992

RecBCD enzyme is altered upon cutting DNA at a chi recombination hotspot.

During its unidirectional unwinding of DNA, RecBCD enzyme cuts one DNA strand near a properly oriented Chi site, a hotspot of homologous genetic recombination in Escherichia coli. We report here that individual DNA molecules containing two properly oriented Chi sites were cut with about 40% efficiency at one or the other Chi site but not detectably at both Chi sites. Furthermore, initial incubation of RecBCD with Chi-containing DNA reduced its ability both to unwind DNA and to cut at Chi sites on subsequently added DNA molecules much more than did initial incubation with Chi-free DNA; the nuclease activity was less severely affected. These results imply that RecBCD loses its Chi-cutting activity upon cutting at a single Chi site and provide a mechanism for ensuring single genetic exchanges near the ends of DNA molecules.

Bacteriophage lambda↗
PubMed1992

A DNA exonuclease induced during meiosis of Schizosaccharomyces pombe.

In meiotic cells of the fission yeast Schizosaccharomyces pombe, a DNA exonuclease activity increased approximately 5-fold after premeiotic S-phase and decreased to the initial level before the meiotic divisions. We have purified this activity, designated exonuclease I, to near homogeneity. The activity co-purified with a polypeptide with an apparent molecular weight of 36,000. With a linear double-stranded DNA substrate, exonuclease I degraded only the 5'-ended strand from each end to produce 3'-single-stranded tails. The enzyme also acted on nicked circular DNA with comparable affinity. The meiotic induction of exonuclease I and its mode of action, similar to that of recombination-promoting exonucleases from bacteria, suggest that exonuclease I is involved in meiotic homologous recombination in S. pombe.

Chromatography, Affinity↗
PubMed1992

Chromosomal context dependence of a eukaryotic recombinational hot spot.

The single base-pair mutation M26 in the ade6 gene of the fission yeast Schizosaccharomyces pombe creates a hot spot for meiotic homologous recombination. When DNA fragments containing M26 and up to 3.0 kilobases of surrounding DNA were moved to the ura4 gene or to a multicopy plasmid, M26 had no detectable hot spot activity. Our results indicate that nucleotide sequences at least 1 kilobase away from M26 are required for M26 hot spot activity and suggest that, as for transcriptional promoters, a second site or proper chromatin structure is required for activation of this eukaryotic recombinational hot spot. We discuss the implications of these results for studies of other meiotic recombinational hot spots and for gene targeting.

Chromosomes, Fungal↗
PubMed1992

Transient expression of the coat protein of sugarcane mosaic virus in sugarcane protoplasts and expression in Escherichia coli.

The coat protein (CP) of strain SC of sugarcane mosaic virus (SCMV-SC) was expressed transiently in sugarcane protoplasts after electroporation with one of two plasmids encoding the CP gene. The CP gene was fused with either the cauliflower mosaic virus 35S promoter or the synthetic monocotyledon promoter "Emu". The coat protein gene was also inducibly expressed in Escherichia coli when fused to the trc promoter. The protein expressed in both systems had the same electrophoretic mobility and antigenic specificity as purified SCMV-SC coat protein. Transient expression of the 35S-CP gene in protoplasts could only be demonstrated in Western blots developed with the chemiluminescence enzyme substrate luminol.

Base Sequence↗
PubMed1992

Pathogenicity of Fusobacterium necrophorum biovar B.

Previous studies showed that the high minimum infective dose (more than 10(6) organisms) of biovar A strains of Fusobacterium necrophorum for mice by subcutaneous inoculation could be greatly reduced, often to less than 10 organisms, by suspending the fusobacteria in sublethal doses of broth cultures of certain other bacterial species, such as Staphylococcus aureus. The present study showed that no such enhancement of infectivity occurred with two biovar B strains. This observation, together with the low pathogenicity of pure cultures of these strains for mice, suggests that biovar B plays no more than a minor role in the aetiology of necrobacillosis.

Animals↗
PubMed1992

The comorbidity of DSM-III-R personality disorders in somatization disorder.

In order to understand psychiatric factors that complicate the medical management of somatizing patients, 94 subjects with known somatization disorder (SD) were evaluated for 13 personality disorders with the Structured Clinical Interview for DSM-III-R Personality Disorders. Referred from multiple primary care settings, the patient sample was predominantly female (85%), married (67%), high school graduates (64%), and had a mean age of 43. Structured interviews documented that 23.4% of SD patients had one personality disorder, and 37.2% had two or more disorders. The four most frequently identified personality disorders were avoidance 26.7%, paranoia 21.3%, self-defeating 19.1%, and obsessive-compulsive 17.1%. Interestingly histrionic personality disorder was identified in only 12.8% of the sample and antisocial personality disorder in 7.4%. In making the diagnosis of SD, health care providers need to avoid the common clinical impression that histrionic behavior often accompanies the disorder. Further research with SD patients is needed to examine the relationship of co-occurring personality disorders to symptom recurrence, health care utilization, and readiness for psychiatric referral.

Adult↗
PubMed1992

The epidemiology and treatment of depression when it coexists with somatoform disorders, somatization, or pain.

This article reviews the relationship between depressive disorders and somatoform disorders, somatization, and pain. These disorders and symptoms are clinically interrelated, yet the nature of the interrelation is not well understood. This review of the literature from 1975 through mid-year 1990 addresses the epidemiology and treatment of these conditions and/or symptoms when they occur together. When robust criteria are used to determine which publications are included, only 14 are available that address depressive disorders, somatoform disorders, and somatization. Similarly, there are only 13 that address depressive disorders and pain. Taken together, these studies indicate that 1) in somatization disorder patients, there is a high prevalence of depression; 2) in patients with major depression, there are substantial levels of hypochondriacal and somatizing symptoms; 3) that depression in the face of coexisting somatization disorder can be successfully treated; 4) in chronic pain patients, there is a high prevalence of depressive disorders; 5) in patients with major depression, pain is a frequent complaint; 6) and finally, that pain improves with the treatment of depression. What is most striking from this review, however, is the very limited number of studies that address these important problems. This lack of research-based data calls for new aggressive research efforts in this area.

Antidepressive Agents↗
PubMed1992

PCR amplification of a specific double-stranded RNA region of Fiji disease virus from diseased sugarcane.

A 450-bp region from one species of the segmented dsRNA genome of Fiji disease virus (FDV) was amplified from total nucleic acid extracts of diseased plants by reverse transcription with MMLV, followed by amplification with Taq DNA polymerase (RT-PCR). Other FDV-specific regions (c 150 bp and c 270 bp) were also amplified from the dsRNA template. FDV cDNA was only synthesised when the viral dsRNA template was boiled and quenched with FDV-specific or random hexamer primers. The reverse transcriptase/DNA polymerase enzyme rTth appeared to yield only the 150 bp fragment from the dsRNA template under the conditions used. The level of sensitivity of RT-PCR for purified FDV dsRNA was 100 ag, approximately 10(4)-fold more sensitive than detection with biotinylated DNA probe.

Base Sequence↗
PubMed1992

Psychological modulation of the delayed type hypersensitivity skin test.

Considerable data have demonstrated that psychological states can influence the immune system in animals. Whether human immune function can be intentionally modulated by the central nervous system is unknown. This article presents data from two studies that sought to demonstrate intentional modulation of the immune system by psychological interventions. It also discusses the methodological complexities involved with this type of research in humans.

Adult↗
PubMed1992

Seventeen complementation groups of mutations decreasing meiotic recombination in Schizosaccharomyces pombe.

We have analyzed 43 recessive mutations reducing meiotic intragenic recombination in Schizosaccharomyces pombe. These mutations were isolated by a screen for reduced plasmid-by-chromosome recombination at the ade6 locus. Sixteen of the mutations define 10 new complementation groups, bringing to 17 the number of genes identified to be involved in meiotic recombination. The mutations were grouped into three discrete classes depending on the severity of the recombination deficiency in crosses involving the ade6-M26 recombination hotspot. Class I mutations caused at least a 1000-fold reduction in M26-stimulated intragenic recombination at the ade6 locus. Class II mutations reduced M26-stimulated recombination approximately 100-fold. Class III mutations caused a 3-10-fold reduction in either M26-stimulated or non-hotspot recombination. We obtained multiple alleles of class I and class II mutations, suggesting that we may be nearing saturation for mutations of this type. As a first step toward mapping, we used mitotic segregation to assign fourteen of the rec genes to chromosomes. Mutations in the six rec genes tested also caused a decrease in intragenic recombination at the ura4 locus; five of these mutations also reduced intergenic recombination between the pro2 and arg3 genes. These results indicate that these multiple rec gene products are required for high level meiotic recombination throughout the S. pombe genome.

Alleles↗
PubMed1992

Meiotically induced rec7 and rec8 genes of Schizosaccharomyces pombe.

The Schizosaccharomyces pombe rec7 and rec8 genes, which are required for meiotic intragenic recombination but not for mitotic recombination, have been cloned and their DNA sequences determined. Genetic and physical analyses demonstrated that the cloned fragments contained the rec genes rather than rec mutation suppressors. A 1.6-kb DNA fragment contained a functional rec7 gene, and a 2.1-kb fragment contained a functional rec8 gene. The nucleotide sequences of these fragments revealed open reading frames predicting 249 amino acids for the rec7 gene product and 393 amino acids for the rec8 gene product. Northern hybridization analysis showed that both rec gene mRNAs were detectable only at 2-3 hr after induction of meiosis. The absence of these mRNAs in mitosis and their disappearance at 4 hr and later in meiosis suggest that the rec7 and rec8 gene products may be involved primarily in the early steps of meiotic recombination in S. pombe.

Amino Acid Sequence↗
PubMed1992

Chi enhances heteroduplex DNA levels during recombination.

The major pathway of homologous recombination in Escherichia coli, the RecBCD pathway, is stimulated by Chi sites. To determine whether Chi enhances an early or late step in recombination, we measured formation of heteroduplex DNA (hDNA) in extracts of lambda-infected E. coli. Chi elevated hDNA levels in these extracts, supporting a role for Chi early (before hDNA formation) in recombination. RecA protein and RecBCD enzyme were both necessary for detection of hDNA, indicating that they, too, act early. Analysis of a panel of recBCD mutants indicated that Chi-nicking activity was needed for Chi's stimulation of hDNA formation. These results support a previously proposed model of recombination. Further results suggested that RecBCD enzyme has an additional role late in recombination.

Bacteriophage lambda↗
PubMed1992

Measuring the outcomes of care for mental health problems. The case of depressive disorders.

To conduct effectiveness research in mental health, many nontrivial problems need to be addressed. A multidisciplinary expert panel designed an outcomes module for major depression and dysthymia to measure disease-specific outcomes, treatments routinely provided, and patient characteristics that influence treatment or its outcomes. The outcomes module was pilot-tested to evaluate its ability to identify a diagnostically homogeneous group of patients, to establish its reliability and validity, and to assess the feasibility of administering the module in a mental health setting. In a cohort of 40 patients, the module identified all 31 patients who had a research diagnosis of major depression or dysthymia (100% sensitivity), and 2 of 9 patients who did not have this diagnosis (77.8% specificity). The outcomes module measured key constructs accurately enough to discriminate between groups of depressed patients expected to differ, indicating positive construct validity. High rates of instrument completion supported the feasibility of using the module in specialty settings. Extensive efforts locating patients for follow-up will be needed to draw valid conclusions about treatment effectiveness.

Adult↗
PubMed1992

Family psychiatric history of patients with somatization disorder.

We estimated the prevalence of psychiatric disability and disorders (depression, mania, schizophrenia, alcohol disorder, drug disorder, antisocial personality, and somatization) in the parents, siblings, and children of three groups of index cases: primary care patients with somatization disorder (n = 70), primary care patients who approached, but did not reach, DSM-III-R criteria for somatization disorder (n = 29), and randomly-selected community residents with no psychiatric disorder (n = 1633). Nearly all psychiatric disorders were more common in relatives of both patient samples than in relatives of community residents, and the patient samples rarely differed from each other. In the patient samples, the 22.9% rate of patients with multiple unexplained medical problems is substantially higher than previous investigations of somatization would predict. The most common disorders in patients' relatives were depression and alcohol disorder. There was little difference in the rates of depression in relatives of somatization patients who were or were not themselves depressed. A similar pattern occurred for alcohol disorder. There was a high risk for antisocial personality disorder in parents of patients meeting DSM-III-R criteria for somatization disorder, but this increase was not found for other relatives.

Adult↗
PubMed1992

An analysis of panel data. The impact of a psychiatric consultation letter on the expenditures and outcomes of care for patients with somatization disorder.

In this study, the cost and health outcomes of a psychiatric consultation letter to primary care physicians caring for a sample of patients diagnosed with somatization disorder, a psychiatric condition associated with multiple, unexplained medical complaints, was assessed. To accommodate the small sample size of 73 patients, outcome effects were calculated using panel analysis. Study patients were randomized to a consultation or noconsultation group, and were repeatedly assessed at equal time intervals. Data were analyzed using parsimonious regression models derived from economic theory. During the 1-year follow-up period, a psychiatric consultation letter was associated with a 12% reduction in health care costs ($455 per patient within first year), with no evidence of deterioration in physical, mental, or general health. Less powerful t-test comparisons between treated and control groups lead to different conclusions. Reasons for these differences are discussed.

Adult↗
PubMed1992

Return to work after an initial myocardial infarction and subsequent emotional distress.

We examined how return to work predicted subsequent change in emotional distress in 143 patients who had been employed at the time of initial myocardial infarction. Ninety patients (63%) returned to work by 4 months and remained employed at 12 months. There were no differences in mental health at baseline between those who returned to work and those who did not, but emotional distress decreased significantly between 4 and 12 months only in the group who returned to work. Emotional distress declined after resuming work even when employees returned to jobs with which they reported dissatisfaction at the time of the myocardial infarction. The relationship between return to work and decreasing emotional distress remained after controlling for initial physical and psychological adjustment as well as sociodemographic and social support characteristics. The improvements in mental health associated with return to work should reassure clinicians who emphasize the emotional as well as economic value of work after an initial myocardial infarction.

Employment↗