Synthesis and properties of oligodeoxynucleotides containing the analogue 2'-deoxy-4'-thiothymidine.

The 2'-deoxythymidine analogue 2'-deoxy-4'-thiothymidine has been incorporated, using standard methodology, into a series of dodecadeoxynucleotides containing the EcoRV restriction endonuclease recognition site (GATATC). The stability of these oligodeoxynucleotides and their ability to act as substrates for the restriction endonuclease and associated methylase have been compared with a normal unmodified oligodeoxynucleotide. No problems were encountered in the synthesis despite the presence of a potentially oxidisable sulfur atom in the sugar ring. The analogue had very little effect on the melting temperature of the self-complementary oligoeoxynucleotides so synthesised and all had a CD spectrum compatible with a B-DNA structure. The oligodeoxynucleotide containing one analogue in each strand within the recognition site, adjacent to the bond to be cleaved (i.e. GAXATC, where X is 2'-deoxy-4'-thiothymidine), was neither a substrate for the endonuclease nor was recognized by the associated methylase. When still within the recognition hexanucleotide but two further residues removed from the site of cleavage (i.e. GATAXC), the oligodeoxynucleotide was a poor substrate for both the endonuclease and methylase. Binding of the oligodeoxynucleotide to the endonuclease was unaffected but the kcat value was only 0.03% of the value obtained for the parent oligodeoxynucleotide. These results show that the incorporation of 2'-deoxy-4'-thionucleosides into synthetic oligodeoxynucleotides may shed light on subtle interactions between proteins and their normal substrates and may also show why 2'-deoxy-4'-thiothymidine itself is so toxic in cell culture.     

What are the complications of influenza and can they be prevented? Experience from the 1989 epidemic of H3N2 influenza A in general practice.

OBJECTIVES--In an epidemic: to measure the incidence and risk of complications of influenza; to determine the effect of pre-existing disease on complications; to estimate vaccine uptake and efficacy. DESIGN--Case-control study. SETTING--Primary care: two group practices. SUBJECTS--342 of the 395 cases of clinically diagnosed influenza reported to the general practice surveillance of infectious diseases scheme of the Public Health Laboratory Service during the 1989 epidemic, and 342 age and sex matched controls. INTERVENTIONS--Examination of records. MAIN OUTCOME MEASURES--Documented recognised complications; hospital admission; previous vaccination. RESULTS--Of 15 recognised complications, bronchitis was the commonest (rate 190.1/1000 cases) and significantly commoner in cases (summary odds ratio 9.7) after adjusting for higher consultation rates (mean 6.1 per annum v 4.2 among controls; p < 0.0001). No deaths were recorded. The risk of bronchitis complicating influenza was higher in patients with pre-existing illnesses regarded as an indication for vaccination (odds ratio 3.3; p < 0.0001). Observed vaccination efficacy in those with pre-existing illnesses and in elderly subjects was high (63% and 77% respectively) but uptake was low (4.5% and 6.1% respectively). CONCLUSIONS--Bronchitis complicates about one fifth of all cases of influenza presenting to general practitioners. Patients with pre-existing illnesses regarded as an indication for vaccination are particularly at risk. Vaccine uptake is extremely low, precluding an unequivocal demonstration of a protective effect.     

Effects of a variety of cytokines and inducing agents on vascular permeability factor mRNA levels in U937 cells.

Vascular permeability factor (VPF) is an approximately 40-kDa disulfide-linked dimeric glycoprotein that is active in increasing blood vessel permeability, endothelial cell growth and angiogenesis. Little is known about VPF gene regulation. In this study, we investigated the effects of a variety of cytokines and inducing agents on VPF mRNA levels in the monocyte-like U937 cell line. Transforming growth factor-beta 1 caused a 1.8-fold increase in VPF mRNA levels after 4 hours, followed by a decline to basal levels by 18 hours. Phorbol 12-myristate 13-acetate, a potent inducer of the differentiation of U937 cells, caused a 12.5-fold increase in VPF mRNA levels at 24 hours, coinciding with the differentiation of these monocyte-like cells into macrophage-like cells.     

Rapid mapping and identification of mutations in Caenorhabditis elegans by restriction site-associated DNA mapping and genomic interval pull-down sequencing

Forward genetic screens provide a powerful approach for inferring gene function on the basis of the phenotypes associated with mutated genes. However, determining the causal mutation by traditional mapping and candidate gene sequencing is often the rate-limiting step, especially when analyzing many mutants. We report two genomic approaches for more rapidly determining the identity of the affected genes in Caenorhabditis elegans mutants. First, we report our use of restriction site-associated DNA (RAD) polymorphism markers for rapidly mapping mutations after chemical mutagenesis and mutant isolation. Second, we describe our use of genomic interval pull-down sequencing (GIPS) to selectively capture and sequence megabase-sized portions of a mutant genome. Together, these two methods provide a rapid and cost-effective approach for positional cloning of C. elegans mutant loci, and are also applicable to other genetic model systems.     

Evidence that rseC, a gene in the rpoE cluster, has a role in thiamine synthesis in Salmonella typhimurium.

In Salmonella typhimurium, the genetic loci and biochemical reactions necessary for the conversion of aminoimidazole ribotide (AIR) to the 4-amino-5-hydroxymethyl-2-methyl pyrimidine (HMP) moiety of thiamine remain unknown. Preliminary genetic analysis indicates that there may be more than one pathway responsible for the synthesis of HMP from AIR and that the function of these pathways depends on the availability of AIR, synthesized by the purine pathway or by the purF-independent alternative pyrimidine biosynthetic (APB) pathway (L. Petersen and D. Downs, J. Bacteriol. 178:5676-5682, 1996). An insertion in rseB, the third gene in the rpoE rseABC gene cluster at 57 min, prevented HMP synthesis in a purF mutant. Complementation analysis demonstrated that the HMP requirement of the purF rseB strain was due to polarity of the insertion in rseB on the downstream rseC gene. The role of RseC in thiamine synthesis was independent of rpoE.