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.

The course of somatization and its effects on utilization of health care resources

Patients with somatization disorder (SD), subthreshold somatization, and somatization that is comorbid with another mental or physical disorder use a remarkably high level of general medical services. Because these patients view themselves as more seriously ill than do patients in the general medical population, their use of health care services may be as high as nine times greater than that of the general population. It is important to understand the course and prevalence of SD because 1) these patients tend to overuse health care resources and services, and 2) the associated costs are enormous. It is vital that expert clinical care and research be directed at this important patient group so that appropriate treatment regimens can be developed to help these patients and control the overutilization of limited health care resources.

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.

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.

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.

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.

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.

Repurposing videodiscs for interactive video instruction: teaching concepts of quality improvement

The purpose of this study was to develop an interactive video instruction (IVI) program to teach registered nurses in the clinical setting concepts of quality improvement and to test the effectiveness of the program. The Smith Author System was used to combine text and video sequences repurposed from videodiscs developed for nursing education to describe and illustrate concepts of quality improvement. A sample of 55 registered nurses from a midwest regional medical center who used the program had a significant increase in knowledge (p < .05) from pre- to postprogram opinionnaire. More nurses with baccalaureate degrees scored above the median for the interactive video instruction program than those with associate degrees or diplomas. Registered nurses with more than 5 years of experience also expressed willingness to apply the concepts of quality improvement to their daily patient care activities and to use computers for learning.

Rural-Urban Differences in Stigma and the Use of Care for Depressive Disorders

Stigma may be a particularly important barrier to mental health care in rural communities where lack of anonymity increases the probability that someone who seeks care will be labeled "crazy." This study examined rural-urban differences in the stigma associated with depressive symptoms and the stigma associated with seeking treatment for depressive disorders. In addition, the study compared how the stigma associated with seeking treatment predicted use of care in rural and urban residents with a history of depressive symptoms. Two hundred subjects from metropolitan and adjacent non-metropolitan counties rated one of four randomly selected vignettes using 14-point semantic differential scales. The findings indicated that rural residents with a history of depressive symptoms labeled people who sought professional help for the disorder somewhat more negatively than their urban counterparts. Logistic models controlling for sociodemographic characteristics demonstrated that the more negative the labeling, the less likely depressed rural residents were to have sought professional help. Labeling was not associated with use of care among urban people with depressive symptoms. We concluded that prospective studies are warranted to inform the development of interventions to decrease the stigma associated with seeking treatment for depressive disorders in rural communities.

Single-stranded DNA binding activity of C1-tetrahydrofolate synthase enzymes

In eukaryotes C1-5,6,7,8-tetrahydrofolate (THF) synthase is a trifunctional enzyme that catalyzes the interconversion of reduced forms of folate to supply activated one-carbon units required for a variety of metabolic pathways. The enzymatic activities include 10-formyl-THF synthetase (EC 6.3.4.3), 5,10-methenyl-THF cyclohydrolase (EC 3.5.4.9), and 5,10-methylene-THF dehydrogenase (EC 1.5.1.5). In bacteria separate, monofunctional or bifunctional polypeptides catalyze the same reactions. We have purified C1-THF synthase from the fission yeast Schizosaccharomyces pombe and found its physical and enzymatic properties similar to those of other eukaryotic C1-THF synthase enzymes. Unexpectedly, the S. pombe enzyme bound strongly (Keq = 100 pM) to single-stranded DNA, but not to double-stranded DNA or to RNA. The binding was sequence-independent, apparently not cooperative, and not detectably inhibited by C1-THF synthase substrates or cofactors. Trifunctional cytoplasmic enzyme from Saccharomyces cerevisiae and monofunctional (synthetase) enzyme from Clostridium acidiurici also bound tightly to single-stranded DNA, while bifunctional (dehydrogenase and cyclohydrolase) enzyme from Escherichia coli did not, suggesting that single-stranded DNA binding is a conserved function of the synthetase domain of C1-THF synthase enzymes.

Pathogenicity of Fusobacterium necrophorum strains from man and animals

Necrobacillosis occurs in man and animals. The typical forms of the disease in animals are caused by Fusobacterium necrophorum biovar A; biovar B strains are much less pathogenic. In this study the pathogenicity for mice of eight human isolates of F. necrophorum was compared with that of animal biovar A and B strains. By subcutaneous inoculation seven of the human strains differed from biovar A but resembled biovar B in (1) producing, at the most, mild local lesions that rapidly healed, and (2) showing no enhancement of infectivity when suspended in sub-lethal doses of Staphylococcus aureus broth culture. The eighth human strain (A2433) resembled biovar A but differed from biovar B in (1) producing severe lesions, and (2) showing greatly enhanced infectivity in the presence of S. aureus. Nonetheless, strain A2433 differed from biovar A, both in the nature of the lesions produced and in its failure to cause severe general signs of illness and rapidly fatal infection. By intravenous inoculation one of two biovar B strains and all except one of the eight human strains produced purulent lesions, often severe, in the liver and elsewhere, but infection was not usually associated with general signs of illness. In contrast, intravenous injection of a biovar A strain gave rise to a rapidly fatal infection, with severe lesions in the liver or elsewhere. The results suggest that the term 'necrobacillosis' as used in human and veterinary medicine refers to diseases that differ in important respects.

Microprojectile transformation of sugarcane meristems and regeneration of shoots expressing β-Glucuronidase

Microprojectile bombardment was used to introduce the GUS reporter gene into sugarcane axillary meristems. Chimeric expression of this gene was observed in 20-40% of shoots regenerated from sugarcane meristems one month after particle bombardment. The linear pattern of GUS expression observed is consistent with periclinal division from single transformed meristematic cells. Meristems have advantages over callus cells as targets for microprojectile transformation, and have potential for introducing agronomically important genes into current commercial sugarcane varieties.

The prevalence of Fusobacterium necrophorum biovar A in animal faeces

Only a small proportion of animals tested were found to be excreting Fusobacterium necrophorum biovar A, the causative organism of necrobacillosis, in the faeces (3 of 69 wallabies, 1 of 66 deer, 2 of 81 cattle). The two positive cattle belonged to a single group of calves on a farm with a history of necrobacillosis and the litter underfoot also readily yielded biovar A organisms. All attempts to demonstrate biovar A in litter on other farms and in soil from an area populated by wallabies and deer failed. Ruminal contents from young beef cattle proved a fertile source of F. necrophorum biovar A, 15 of 18 animals giving a positive result. It is suggested that disturbance of the gastrointestinal microflora leads to intestinal multiplication and faecal excretion of the organism, which may then give rise to necrobacillosis of the body surface.

Effect of disturbance of the gastrointestinal microflora on the faecal excretion of Fusobacterium necrophorum biovar A

Oral pretreatment of mice with either a mixture of kanamycin and erythromycin or metronidazole to modify the gut microflora greatly enhanced the faecal excretion of Fusobacterium necrophorum biovar A given by mouth. This lends support to the suggestion that disturbance of the gastrointestinal microflora in animals such as cattle, which often carry the organism in the rumen, may lead to intestinal multiplication and faecal excretion, thereby providing a source of infection that may lead to necrobacillosis of the body surface.

Development of screeners for depressive disorders and substance disorder history

If screeners are going to be widely incorporated in clinical care to increase the detection of common psychiatric disorders, they need to be brief, easy to score, and sensitive across diverse patient populations. Few screeners exist that meet these criteria. This problem is addressed in this study by identifying a subset of questions from the Diagnostic Interview Schedule (DIS), which predicted simultaneously obtained DIS diagnoses. A two-item screener to detect depression or dysthymia within the last year and three-item screeners for lifetime drug disorders and alcohol disorders were tested in community residents, medical, and mental health patients. The sensitivity of the depression screener ranged between 83% and 94%. The sensitivity of the drug screener ranged between 91% and 94%, excluding one site with an extremely low prevalence of drug problems. The sensitivity of the alcohol screener ranged between 87% and 92%. Specificity for all three screeners exceeded 90% in community and medical samples, while being somewhat lower among mental health patients. These findings indicate that these brief screeners may be useful in a variety of epidemiologic studies to provide estimates of common psychiatric disorders when complete diagnostic interviews are not feasible. If further validation studies support these sensitivity and specificity estimates, these new instruments may also be valuable as initial brief screeners in a two-stage screening process to improve clinicians' recognition of common mental health problems that complicate case management and impair patient functioning.