Evidence for unique DNA repair activity encoded by a cloned Serratia marcescens gene: suppression of Escherichia coli mutations that reduce repair of alkylated DNA.

A recombinant plasmid containing a Serratia marcescens DNA repair gene has been analyzed biochemically and genetically in Escherichia coli mutants deficient for repair of alkylated DNA. The cloned gene suppressed sensitivity to methyl methanesulfonate of an E. coli strain deficient in 3-methyladenine DNA glycosylases I and II (i.e., E. coli tag alkA) and two different E. coli recA mutants. Attempts to suppress the methyl methanesulfonate sensitivity of the E. coli recA mutant by using the cloned E. coli tag and alkA genes were not successful. Southern blot analysis did not reveal any homology between the S. marcescens gene and various known E. coli DNA repair genes. Biochemical analysis with the S. marcescens gene showed that the encoded DNA repair protein liberated 3-methyladenine from alkylated DNA, indicating that the DNA repair molecular is an S. marcescens 3-methyladenine DNA glycosylase. The ability to suppress both types of E. coli DNA repair mutations, however, suggests that the S. marcescens gene is a unique bacterial DNA repair gene.     

Common mental health problems in immigrants and refugees: general approach in primary care

Background:

Recognizing and appropriately treating mental health problems among new immigrants and refugees in primary care poses a challenge because of differences in language and culture and because of specific stressors associated with migration and resettlement. We aimed to identify risk factors and strategies in the approach to mental health assessment and to prevention and treatment of common mental health problems for immigrants in primary care.

Methods:

We searched and compiled literature on prevalence and risk factors for common mental health problems related to migration, the effect of cultural influences on health and illness, and clinical strategies to improve mental health care for immigrants and refugees. Publications were selected on the basis of relevance, use of recent data and quality in consultation with experts in immigrant and refugee mental health.

Results:

The migration trajectory can be divided into three components: premigration, migration and postmigration resettlement. Each phase is associated with specific risks and exposures. The prevalence of specific types of mental health problems is influenced by the nature of the migration experience, in terms of adversity experienced before, during and after resettlement. Specific challenges in migrant mental health include communication difficulties because of language and cultural differences; the effect of cultural shaping of symptoms and illness behaviour on diagnosis, coping and treatment; differences in family structure and process affecting adaptation, acculturation and intergenerational conflict; and aspects of acceptance by the receiving society that affect employment, social status and integration. These issues can be addressed through specific inquiry, the use of trained interpreters and culture brokers, meetings with families, and consultation with community organizations.

Interpretation:

Systematic inquiry into patients’ migration trajectory and subsequent follow-up on culturally appropriate indicators of social, vocational and family functioning over time will allow clinicians to recognize problems in adaptation and undertake mental health promotion, disease prevention or treatment interventions in a timely way.Changing patterns of migration to Canada pose new challenges to the delivery of mental health services in primary care. For the first 100 years of Canada’s existence, most immigrants came from Europe; since the 1960s, there has been a marked shift, with greater immigration from Asia, Africa, and Central and South America.¹ The mix differs across the provinces, although nearly all immigrants settle in Canada’s largest cities.² The task of preventing, recognizing and appropriately treating common mental health problems in primary care is complicated for immigrants and refugees because of differences in language, culture, patterns of seeking help and ways of coping.^3–6In consultation with experts in immigrant and refugee mental health, we reviewed the literature to determine associated risks and clinical considerations for primary care practitioners in the approach to common mental health problems among new immigrant or refugee patients.^7–10 In this paper, we review the effect of migration on mental health, use of health care and barriers to care. We outline basic clinical strategies for primary mental health care of migrants including the use of interpreters, family interaction and assessment, and working with community resources.     

Carbon and Nitrogen Mineralization of Lead Treated Soils in the Eastern Mediterranean Region,Turkey

The aim of this study was to determine the first effect of lead on microbial activity in soil. The study was carried out in the soil samples from four different radish (Raphanus sativus L. var. radicula, Brassicaceae) fields along the highway in a district (Kadirli, Osmaniye) of the Eastern Mediterranean Region, Turkey. After the calculation of Pb contents, the Pb amounts of the soil samples were brought up to 50 and 100 mg Pb kg^?1 by treatment with Pb(NO ₃ ) ₂ , and the samples for the carbon and the nitrogen mineralization were incubated under controlled conditions (28°C, constant moist). The carbon mineralization was determined by a CO ₂ respiration method for 30 days. The nitrogen mineralization was observed in vitro for 6 weeks. The untreated group was statistically different from the 50 and 100 mg Pb kg^?1 treatments in the aspect of the C(CO ₂ ) outlet during mineralization (P ≤ 0.05), but difference between the 50 and 100 mg Pb kg^?1 treatments was not significant. NH ₄ -N and NO ₃ -N contents of each soil were shown differences between across treatments. Based on these results, it is possible to conclude that the addition of 50 and 100 mg Pb kg^?1 provided a toxic effect threshold for the microbial activity into 30 days.     

Incidence of mycoflora and mycotoxins in some edible fruits and seeds of forest origin

Twelve fungi namelyAlternaria alternata, Aspergillus flavus, A niger, A ochraceus, Actinomucor repens, Capnodoium spp., Curvularia lunata, Fusarium pallidoroseum, F solani, F verticillioides, Penicillium citrinum and Rhizopus stolonifer were recorded from samples ofAegle marmelos, Aesculus indica, Buchanania lanzan andPinus gerardiana. In case ofPrunus amygdalus only Rstolonifer was recorded. A significant variation in pattern of mycoflora incidence was observed in terms of source and season. Fungal infestation in most of the substrates was found to be highest during monsoon. Aflatoxins were the most common mycotoxins elaborated by different isolates ofA flavus obtained fromA marmelos, B lanzan andP gerardiana. The amount of aflatoxins produced by the toxigenic isolates ofA flavus was in the range of traces to 0.9–26.0 μg/ml inA marmelos, 0.8–17.5 μg/ml inP gerardiana and 0.65–13.2 μg/ml inB lanzan. The percentage toxigenicity was comparatively lower in the isolates of other mycotoxigenic fungi. Aflatoxins were detected almost in all the samples analyzed for mycotoxin contamination. However, traces of zearalenone were detected inA marmelos. The concentration of aflatoxin B₁ was in the range of 0.13–0.75 μg/g inA marmelos, 0.09–0.60 μg/g inP gerardiana and 0.01–0.20 ug/g inB lanzan. Mycotoxins were not detected inAesculus indica andPrunus amygdalus.     

Synergistic interaction between yeast nucleotide excision repair factors NEF2 and NEF4 in the binding of ultraviolet-damaged DNA.

Saccharomyces cerevisiae RAD4, RAD7, RAD16, and RAD23 genes function in the nucleotide excision repair (NER) of ultraviolet light (UV)-damaged DNA. Previous biochemical studies have shown that the Rad4 and Rad23 proteins are associated in a stoichiometric complex named NEF2, and the Rad7 and Rad16 proteins form another stoichiometric complex named NEF4. While NEF2 is indispensable for the incision of UV-damaged DNA in the in vitro reconstituted system, NEF4 stimulates the incision reaction. Both NEF2 and NEF4 bind UV-damaged DNA, which raises the intriguing possibility that these two complexes cooperate to achieve the high degree of specificity for DNA damage demarcation required for nucleotide excision repair in vivo. Consistent with this hypothesis, we find that NEF2 and NEF4 bind in a synergistic fashion to UV-damaged DNA in a reaction that is dependent on ATP. We also purify the Rad7 protein and show that it binds DNA but has no preference for UV-damaged DNA. Rad7 physically interacts with NEF2, suggesting a role for Rad7 in linking NEF2 with NEF4.     

Complex formation with damage recognition protein Rad14 is essential for Saccharomyces cerevisiae Rad1-Rad10 nuclease to perform its function in nucleotide excision repair in vivo

Nucleotide excision repair (NER) in eukaryotes requires the assembly of a large number of protein factors at the lesion site which then coordinate the dual incision of the damaged DNA strand. However, the manner by which the different protein factors are assembled at the lesion site has remained unclear. Previously, we have shown that in the yeast Saccharomyces cerevisiae, NER proteins exist as components of different protein subassemblies: the Rad1-Rad10 nuclease, for example, forms a tight complex with the damage recognition protein Rad14, and the complex of Rad1-Rad10-Rad14 can be purified intact from yeast cells. As the Rad1-Rad10 nuclease shows no specificity for binding UV lesions in DNA, association with Rad14 could provide an effective means for the targeting of Rad1-Rad10 nuclease to damage sites in vivo. To test the validity of this idea, here we identify two rad1 mutations that render yeast cells as UV sensitive as the rad1Delta mutation but which have no effect on the recombination function of Rad1. From our genetic and biochemical studies with these rad1 mutations, we conclude that the ability of Rad1-Rad10 nuclease to associate in a complex with Rad14 is paramount for the targeting of this nuclease to lesion sites in vivo. We discuss the implications of these observations for the means by which the different NER proteins are assembled at the lesion site.