Results of the IPCS collaborative study on complex mixtures.

The International Programme on Chemical Safety (IPCS) sponsored a collaborative study to examine the intra- and inter-laboratory variation associated with the preparation and bioassay of complex chemical mixtures. The mixtures selected were National Institute of Standards and Technology (NIST) Standard Reference Materials (SRMs). 20 laboratories worldwide participated in the collaborative trial. The participating laboratories extracted the organic portion of two particulate samples--an air-particulate sample and a diesel-particulate sample--and bioassayed the extracts. The laboratories simultaneously bioassayed a NIST-prepared extract of coal tar and two control compounds (benzo[a]pyrene, and 1-nitropyrene). The bioassay method used was the Salmonella/mammalian microsome plate-incorporation test using strains TA98 and TA100. Study design also allowed for a comparison of sonication and Soxhlet extraction techniques. The mean extractable masses for the air particles and diesel particles were approximately 5% and 17.5%, respectively. The particulate samples were mutagenic in both strains with and without activation in all 20 laboratories. For TA100 the with and without activation slope values for the air particulate were 162 and 137 revertants per mg particles, respectively. For TA98 the respective diesel slope values were 268 and 269. The mutagenicity slope values for the diesel particles ranged from 3090 (TA98, +S9) to 6697 (TA100, +S9) revertants per mg particles. The coal tar solution was negative for both strains when exogenous activation was not used but was mutagenic in both strains with exogenous activation. The benzo[a]pyrene and 1-nitropyrene were used as positive controls and gave results consistent with the literature. This paper provides a complete summary of the data collected during the collaborative study. Companion papers provide further analysis and interpretation of the results.     

Noncontact dipole effects on channel permeation. III. Anomalous proton conductance effects in gramicidin

Proton transport on water wires, of interest for many problems in membrane biology, is analyzed in side-chain analogs of gramicidin A channels. In symmetrical 0.1 N HCl solutions, fluorination of channel Trp(11), Trp-(13), or Trp(15) side chains is found to inhibit proton transport, and replacement of one or more Trps with Phe enhances proton transport, the opposite of the effects on K(+) transport in lecithin bilayers. The current-voltage relations are superlinear, indicating that some membrane field-dependent process is rate limiting. The interfacial dipole effects are usually assumed to affect the rate of cation translocation across the channel. For proton conductance, however, water reorientation after proton translocation is anticipated to be rate limiting. We propose that the findings reported here are most readily interpreted as the result of dipole-dipole interactions between channel waters and polar side chains or lipid headgroups. In particular, if reorientation of the water column begins with the water nearest the channel exit, this hypothesis explains the negative impact of fluorination and the positive impact of headgroup dipole on proton conductance.     

Lifestyle modifications to prevent and control hypertension. 4. Recommendations on physical exercise training. Canadian Hypertension Society,Canadian Coalition for High Blood Pressure Prevention and Control,Laboratory Centre for Disease Control at Health Canada,Heart and Stroke Foundation of Canada

OBJECTIVE: To provide updated, evidence-based recommendations for health care professionals concerning the effects of regular physical activity on the prevention and control of hypertension in otherwise healthy adults. OPTIONS: People may engage in no, sporadic or regular physical activity that may be of low, moderate or vigorous intensity. For sedentary people with hypertension, the options are to undertake or maintain regular physical activity and to avoid or moderate medication use; to use another lifestyle modification technique; to commence or continue antihypertensive medication; or to take no action and remain at increased risk of cardiovascular disease. OUTCOMES: The health outcomes considered were changes in blood pressure and in morbidity and mortality rates. Because of insufficient evidence, no economic outcomes were considered. EVIDENCE: A MEDLINE search was conducted for the period 1966-1997 with the terms exercise, exertion, physical activity, hypertension and blood pressure. Both reports of trials and review articles were obtained. Other relevant evidence was obtained from the reference lists of these articles, from the personal files of the authors and through contacts with experts. The articles were reviewed, classified according to study design and graded according to level of evidence. VALUES: A high value was placed on avoidance of cardiovascular morbidity and premature death caused by untreated hypertension. BENEFITS, HARMS AND COSTS: Physical activity of moderate intensity involving rhythmic movements with the lower limbs for 50-60 minutes, 3 or 4 times per week, reduces blood pressure and appears to be more effective than vigorous exercise. Harm is uncommon and is generally restricted to the musculoskeletal injuries that may occur with any repetitive activity. Injury occurs more often with jogging than with walking, cycling or swimming. The costs include the costs of appropriate shoes, garments and equipment, but these were not specifically measured. RECOMMENDATIONS: (1) People with mild hypertension should engage in 50-60 minutes of moderate rhythmic exercise of the lower limbs, such as brisk walking or cycling, 3 or 4 times per week to reduce blood pressure, (2) Exercise should be prescribed as an adjunctive therapy for people who require pharmacologic therapy for hypertension, especially those who are not receiving beta-blockers. (3) People who do not have hypertension should participate in regular exercise as it will decrease blood pressure and reduce the risk of coronary artery disease, although there is no direct evidence that it will prevent hypertension. VALIDATION: These recommendations agree with those of the World Hypertension League, the American College of Sports Medicine, the report of the US Surgeon General on physical activity and health, and the US National Institutes of Health Consensus Development Panel on Physical Activity and Cardiovascular Health. These guidelines have not been clinically tested. SPONSORS: The Canadian Hypertension Society, the Canadian Coalition for High Blood Pressure Prevention and Control, the Laboratory Centre for Disease Control at Health Canada, and the Heart and Stroke Foundation of Canada.     

Characterization of intracellular polygalacturonic acidtrans-eliminase fromKlebsiella oxytoca,Yersinia enterocolitica,andErwinia chrysanthemi

Intracellular polygalacturonic acidtrans-eliminase (PATE) was purified and characterized fromKlebsiella oxytoca andYersinia enterocolitica, enterobacteria unable to macerate plant tissue. The well-studied PATE from a strain ofErwinia chrysanthemi, a phytopathogen able to macerate plant tissue and cause soft-rot disease, was included for comparison. PATE from all strains displayed endo-splitting activity with pH optima between pH 8.5 and 9.0E. chrysanthemi had three isozymes (pls at pH 9.4, 9.0, and 7.8),K. oxytoca had two isozymes (pIs at pH 5.9 and 5.3), andY. enterocolitica had one isozyme (pI at pH 5.8). Molecular weights for theKlebsiella andYersinia PATEs were 71,000 and 55,000, respectively, compared with 33,000 for theErwinia PATE. Unlike theErwinia enzyme, theKlebsiella andYersinia PATEs did not require divalent cations for activity and could not macerate plant tissue without addition of pectinmethylesterase. The polygalacturonic acid-degrading enzymes found inK. oxytoca andY. enterocolitica appear to represent a separate type of PATE enzyme. It is unlikely that these organisms are phytopathogens; however, their ability to degrade polygalacturonic acid is probably advantageous to their survival in environments containing decomposing plant residues.     

Development of codominant markers for identifying species hybrids

Herein we describe a simple method fordeveloping species-diagnostic markers thatwould permit the rapid identification of hybridindividuals. Our method relies on amplifiedlength polymorphism (AFLP) and single strandconformation polymorphism (SSCP) technologies,both of which can be performed in any molecularbiology facility using standard laboratoryequipment. We demonstrate the utility of theAFLP-SSCP method by developing threetaxon-specific markers that will be suitablefor monitoring introgression in endangeredKlamath basin suckers.     

Klebsiella planticola sp. nov.: A new species of enterobacteriaceae found primarily in nonclinical environments

The nameKlebsiella planticola sp. nov. is proposed for a group of organisms isolated primarily from botanical and daquatic environments. Both numerical and molecular taxonomy techniques show that the species belongs within the genusKlebsiella and that it is distinct from other described species of the genus. The new species has 3 biogroups.K. planticolla is phenotypically identical toK. pneumoniae in classical biochemical tests, but it is distinguishable fromK. pneumoniae based on its ability to grow at 10°C and its inability to produce gas from lactose at 44.5°C. Additional reactions that can be used in combination with the temperature criteria includel-sorbose fermentation and ability to utilize hydroxy-l-proline as a sole carbon source. Strain V-236 (ATCC 33531; CDC 4245-72) is the type strain of the new species.