Overview of systematic reviews in allergy epidemiology.

BACKGROUND: There is a substantial body of evidence on the epidemiology of allergic conditions, which has advanced the understanding of these conditions. We aimed to systematically identify systematic reviews and meta-analyses on the epidemiology of allergic diseases to assess what has been studied comprehensively and what areas might benefit from further research. METHODS: We searched PubMed and EMBASE up to 12/2014 for systematic reviews on epidemiological research on allergic diseases. We indexed diseases and topics covered and extracted data on the search characteristics of each systematic review. RESULTS: The search resulted in 3991 entries after removing duplicates, plus 20 other items found via references and conference abstracts; 421 systematic reviews were relevant and included in this overview. The majority contained some evidence on asthma (72.9%). Allergic rhinitis, atopic eczema and food hypersensitivity were covered in 15.7%, 24.5% and 9.0%, respectively. Commonly studied risk factors for atopic eczema included dietary and microbial factors, while for asthma, pollution and genetic factors were often investigated in systematic reviews. There was some indication of differing search characteristics across topics. CONCLUSION: We present a comprehensive overview with an indexed database of published systematic reviews in allergy epidemiology. We believe that this clarifies where most research interest has focussed and which areas could benefit from further research. We propose that this effort is updated every few years to include the most recently published evidence and to extend the search to an even broader list of hypersensitivity/allergic disorders.

para-aminobenzoate synthesis from chorismate occurs in two steps.

Escherichia coli p-aminobenzoate synthase is composed of two nonidentical subunits encoded by pabA and pabB and has been assumed to be the sole enzyme responsible for p-aminobenzoate biosynthesis from chorismate and glutamine. Plasmids were constructed that overproduce the p-aminobenzoate synthase subunits 250-500-fold. Partial purification of the subunits revealed that they form a diffusible intermediate that is subsequently converted to p-aminobenzoate by a second enzyme (Mr = 49,000) temporarily designated enzyme X.

Nucleotide sequence of the Acinetobacter calcoaceticus trpGDC gene cluster.

A plasmid library of Acinetobacter calcoaceticus HindIII fragments was constructed, and clones that complemented an Escherichia coli pabA mutant were selected. Plasmids containing a 3.9-kb fragment of A. calcoaceticus DNA that also complemented E. coli trpD and trpC-(trpF+) mutants were obtained. We infer that complementation of E. coli pabA mutants was the result of the expression of the amphibolic anthranilate-synthase/p-aminobenzoate-synthase glutamine-amidotransferase gene and that the plasmid insert carried the entire trpGDC gene cluster. In E. coli minicells, the plasmid insert directed the synthesis of polypeptides of 44,000, 33,000, and 20,000 daltons, molecular masses that are consistent with the reported molecular masses of phosphoribosylanthranilate transferase, indoleglycerol-phosphate synthase, and anthranilate-synthase component II, respectively. A 3,105-bp nucleotide sequence was determined. Comparison of the A. calcoaceticus trpGDC sequences with other known trp gene sequences has allowed insight into (1) the evolution of the amphibolic trpG gene, (2) varied strategies for coordinate expression of trp genes, and (3) mechanisms of gene fusions in the trp operon.

GC-rich murine adenosine deaminase gene promoter supports diverse tissue-specific gene expression.

The murine adenosine deaminase (ADA) gene has a GC-rich promoter that is structurally typical of many mammalian "housekeeping" gene promoters. The ability of the ADA gene promoter to support diverse tissue-specific gene expression was investigated. Endogenous ADA gene expression in different mouse tissues was found to vary over a greater than 3000-fold range in a highly complex pattern. This range of expression was also observed in cultured human cell lines derived from different tissues. The ADA levels in all tissues and cell lines examined correlated closely with steady-state ADA mRNA levels. Several of the mouse tissues examined also showed stage-specific variation during postnatal development. In order to determine whether tissue-specific ADA expression was controlled by cis-acting sequences upstream of the coding region, constructs containing a reporter gene regulated by the ADA gene's 5' flanking sequences were used to generate transgenic mice. All transgene-expressing mice obtained showed diverse reporter gene expression in the tissues analyzed. Our results demonstrate that both in vivo and in the context of an integrated transgene this GC-rich promoter can support highly diverse gene expression in all tissues of the animal.