A search strategy for occupational health intervention studies.

BACKGROUND: As a result of low numbers and diversity in study type, occupational health intervention studies are not easy to locate in electronic literature databases. AIM: To develop a search strategy that facilitates finding occupational health intervention studies in Medline, both for researchers and practitioners. METHODS: A gold standard of articles was created by going through two whole volumes of 19 biomedical journals, both occupational health specialty and non-occupational health journals. Criteria for occupational health intervention studies were: evaluating an intervention with an occupational health outcome and a study design with a control group. Each journal was searched independently by two of the authors. Search terms were developed by asking specialists and counting word frequencies in gold standard articles. RESULTS: Out of 11 022 articles published we found 149 occupational health intervention studies. The most sensitive single terms were work*[tw] (sensitivity 71%, specificity 88%) and effect*[tw] (sensitivity 75%, specificity 63%). The most sensitive string was (effect*[tw] OR control*[tw] OR evaluation*[tw] OR program*[tw]) AND (work*[tw] OR occupation*[tw] OR prevention*[tw] OR protect*[tw]) (sensitivity 89%, specificity 78%). The most specific single terms were "occupational health"[tw] (sensitivity 22%, specificity 98%) and effectiveness[tw] (sensitivity 22%, specificity 98%). The most specific string was (program[tw] OR "prevention and control"[sh]) AND (occupational[tw] OR worker*[tw]) (sensitivity 47%, specificity 98%). CONCLUSION: No single search terms are available that can locate occupational health intervention studies sufficiently. The authors' search strings have acceptable sensitivity and specificity to be used by researchers and practitioners respectively. Redefinition and elaboration of keywords in Medline could greatly facilitate the location of occupational health intervention studies.

Comparison of detection methods for trichothecenes produced by Fusarium sporotrichioides on fodder and grains at different air humidities.

Growth and toxin production of a highly toxic strain of Fusarium sporotrichioides Sherb were studied on oat and wheat grains and on straw under experimental conditions, in which relative humidity (RH) of air was regulated. The materials were incubated at three different RH levels at a range of 84-100%. F. sporotrichioides grew well on oat and wheat grains at RH 97-100% but grew less well at RH 84-88% and on straw. Toxin production was measured with three biological toxicity tests (cytotoxicity test, dermotoxicity test, and yeast cell toxicity test), with chemical analysis, and T-2 ELISA assay. Cytotoxicity and production of trichothecene mycotoxins were detected in all the samples incubated at all three RH levels. On oat and wheat grains, T-2 toxin, neosolaniol, and diacetoxyscirpenol were found, and on straw T-2 toxin, HT-2 toxin, neosolaniol, and T-2 tetraol were determined. In the T-2 ELISA assay, all material samples were found to contain T-2 toxin. The cytotoxicity test was the most sensitive method for detecting biological toxicity of samples inoculated with fungus. The T-2 ELISA assay and chemical analysis were about equally sensitive to detect T-2 toxin in samples.

Factors affecting the results of T-2 mycotoxin ELISA assay.

Certain substances in the sample may increase or decrease the reaction between the enzyme and substrate in ELISA assays. During a survey of T-2 trichothecene in food and animal feed 75% of milled grain samples gave a higher O.D. value in competitive T-2 toxin ELISA than the negative control. In samples spiked with small quantities (10 micrograms/kg) of T-2 toxin this type of reaction resulted in underestimates of toxin content. However, the effect was weak and, owing to the high sensitivity of the assay, it did not result in false negative reactions. The low efficiency of the carrier solvent and natural peroxidases in food and feed were considered to be the cause of the inaccurate reactions. A few fermented and processed foodstuffs and feed gave positive results in the T-2 toxin ELISA assay, but verification of the results by gas chromatography (GC) showed that the reactions were false. Certain substances in the samples destroyed or decreased the enzyme activity. False positive reactions can be distinguished from correct ones by retesting the extracts in different dilutions.

Structure and expression of the ompB operon, the regulatory locus for the outer membrane porin regulon in Salmonella typhimurium LT-2.

The ompB operon of Salmonella typhimurium encodes a positive transcriptional regulator OmpR and an inner membrane protein EnvZ. Both proteins are needed for the proper expression of the outer membrane proteins OmpC and OmpF. We have determined the nucleotide sequence of the ompB locus and its adjacent regions. A comparison between the S. typhimurium and Escherichia coli sequences revealed that the ompB locus is highly conserved. The sequence data also showed that ompR and envZ form an operon, where the coding regions overlap by four base-pairs. Utilizing ompR-lacZ and envZ-lacZ gene fusions, the translational levels of expression of these two genes were measured, showing that ompR is considerably more efficiently expressed than envZ. Analysis of ompR frameshift mutations showed that translation of envZ is almost totally dependent on the translation of the upstream gene ompR. The mechanism of this translational coupling appears to be a reinitiation of the ribosome at the overlapping region of the two genes. The characteristics of the OmpR and EnvZ proteins were in agreement with the known functions and cellular locations of these proteins. OmpR was found to contain a putative DNA binding site, while EnvZ contained two hydrophobic stretches typical of transmembrane regions. Both OmpR and EnvZ show extensive homologies with many proteins from a number of different origins, all of which function in pairs and through which environmental signals modulate gene expression. Hence, the tightly coupled synthesis of these proteins seems to be essential in eliciting a proper response in the transmembrane regulation of gene expression.

Mutangenicity and toxicity of amitrole. I. Drosophila tests.

Amitrole was highly toxic at early larval stages of Drosophila (LD50 is 40 ppm in medium). Toxicity of amitrole was also revealed by prolongation of development time even at 10 ppm. However, no mutagenic effects of amitrole were observed either in the sex chromosome non-disjunction test (females reared on medium containing amitrole at 10 ppm) or in the sex-linked recessive lethal test (males reared on medium containing amitrole at 10 ppm).

Mutagenicity and toxicity of amitrole. II. Human lymphocyte culture tests.

Effects of amitrole (3-amino-1,2,4-triazole) on human leucocytes in culture were investigated. Amitrole interfered with lymphoblast transformation and inhibited cell growth in concentrations of 0.2% w/v and higher. Selected metaphases were examined for the presence of chromosome and chromatid aberrations. No clastogenic effects were observed.

Mutagenicity and toxicity of amitrole. III. Microbial tests.

Amitrole (3-amino-1,2,4-triazole) inhibits bacterial growth both in Escherichia coli and Salmonella typhimurium at a concentration of 0.5% in minimal medium. Repression of growth already occurs at a concentration of 0.1% of amitrole in this medium. In complete medium the bacteria tolerate concentrations of amitrole as high as 1.7-2.4% before growth ceases. Mutagenicity was tested by differential growth comparisons on E. coli strains W 3110 thy pol A1, defective in DNA polymerase I, and its revertant pol A+. Known mutagens (MMS, NTG, mitomycin C) were used as positive controls. Analogous negative results were also obtained in a revertant test when several trp mutant strains of Salmonella were used.