Tolerance of bacteria to organic solvents

Organic-solvent-tolerant bacteria are a relatively novel group of extremophilic microorganisms. They overcome the toxic and destructive effects of organic solvents due to the presence of various adaptive mechanisms. Extensive studies done on the toluene tolerance of certain Pseudomonas strains have led to an understanding of the mechanisms of organic solvent tolerance involving novel adaptations such as the toluene efflux pumps, cis-trans isomerisation of membrane fatty acids, rapid membrane repair mechanisms, etc. Organic-solvent-tolerant mutants of Escherichia coli have been constructed and genes enhancing such tolerance characterised. However, there is practically no information available on the tolerance mechanisms of the reported Gram-positive organic-solvent-tolerant bacterial strains like Bacillus, Rhodococcus and Arthrobacter. This review discusses the general aspects of organic-solvent-tolerant bacteria, their history, biodiversity, mechanisms of tolerance and proposes certain probable adaptations of Gram-positive bacteria in tolerance to organic solvents.     

Potential tolerance against bromobenzene-induced acute hepatotoxicity due to prior subchronic exposure

Groups of adult male Sprague-Dawley rats were treated i.p. with 0, 0.3 and 0.5 mmole bromobenzene (BB)/kg per day in corn oil, 5 days a week for 4 weeks. Thereafter, one half of each of these groups was treated i. p. with a single acute toxic dose of 2.5 mmole BB/kg. Urines were then collected for 24 h and the animals were then sacrificed. The hepatotoxicity induced by an acute dose of BB was significantly reduced due to prior subchronic exposure to BB at 0.5 mmol/kg, but not so at 0.3 mmol/kg. These data indicate a potential tolerance against acute hepatotoxicity of BB due to prior subchronic exposure. A significant increase in the urinary excretion of thioethers or mercapturic acids of BB combined with a significant increase in the urinary level ofp-bromocatechol due to prior subchronic treatment with 0.5 mmol BB/kg relative to those due to acute treatment alone was observed. Thus enhanced bromobenzene metabolism could partly explain such potential tolerance against its acute hepatotoxicity. Such protection may also be related to certain cellular events which might occur subsequent to metabolic activation of BB.     

Learning disabilities and school problems in a regional cohort of extremely low birth weight (less than 1000 G) children: a comparison with term controls

We compared the prevalence of learning disabilities at age 8 years in a subgroup of 68 of 129 (53%) regional cohort of extremely low birth weight (ELBW) children who were considered "normal" neurologically and intellectually (IQ greater than or equal to 85) with that of 114 term group matched controls (C). Both groups were tested with a battery of psychoeducational measures, and parents and teachers completed questionnaires on the school performance of the children. ELBW children were comparable with C on measures of intelligence (ELBW 101 +/- 8, C 104 +/- 11), language, and academic achievement but fared significantly less well in motor performance (p less than .0001). The prevalence of learning disabilities (by predefined criteria) in ELBW children (26%) was not increased compared with C (19%). However, teachers rated significantly more ELBW children as performing below grade level than were C (31% vs 16%, p less than .05), and by parent report, a higher proportion of ELBW children had received special assistance in school compared with C (37% vs 16%, p less than .001). We conclude that although the prevalence of learning disabilities in normal ELBW children was not different from that in controls, ELBW children did less well and utilized more special resources.     

Endocrine effects of dehydroepiandrosterone and its fluorinated analog,fluasterone, in rats

Cancer chemoprevention is the use of pharmacologic agents to inhibit the development of cancer. The adrenal steroid dehydroepiandrosterone (DHEA) has demonstrated chemopreventive efficacy in animal models of tumorigenesis. However, due to DHEA's undesirable hormonal actions, the fluorinated analog fluasterone (fl‐DHEA), which also has chemopreventive characteristics, was synthesized as a potential alternate agent. It is not known whether fl‐DHEA has hormonal actions. The endocrinologic effects of DHEA and fl‐DHEA in adult male and female Fischer 344 rats were examined following 28 days of daily oral treatment. Initial doses tested were 30 and 300 mg/kg/day for each drug (n=12/sex/group), which are equivalent to 104 and 1,042 µmoles/kg/day DHEA, and 103 and 1,034 µmoles/kg/day fl‐DHEA. However, due to weight loss at the high dose, doses were lowered to 150 mg/kg/day for each drug (521 and 517 µmoles/kg/day DHEA and fl‐DHEA, respectively). Administration of DHEA resulted in dose‐dependent increases in plasma DHEA and DHEA‐S 1 h after dosing in week 4. DHEA produced an estrogenic effect in female rats expressed as decreased plasma FSH and LH, inhibition of ovulation, prolonged estrus, and increased uterine estrogen receptors. DHEA also increased plasma levels of androstenedione in males and females. Administration of fl‐DHEA increased the estrus cycle length due to a prolonged diestrus II phase and decreased the weights of the uterus, prostate, seminal vesicles, and testes. In addition, fl‐DHEA decreased plasma FSH, LH, and tissue estradiol, and increased plasma dihydrotestosterone levels in both sexes. These results indicate that fl‐DHEA is hormonally active and additional studies are warranted to further describe its endocrinologic effects. Drug Dev. Res. 58:169–178, 2003. © 2003 Wiley‐Liss, Inc.     

病人付费增加了中国医疗体制面临的挑战

编辑：你好。刘涛的述评（见本刊2006，4期，200页）在病人零付费问题上没有充分考虑医疗保健的政策选择问题。中国先前的情况表明，如需自己支付医药费，病人会减少看病次数，随之导致人民生活质量更差，现在的证据证实了这一点。在中国，老年人40％不看病和75％不住院的原因是由于医疗费用（病人付费）。另外，有人指出病人付费导致医疗不公平现象更加严重。进一步危害包括拖延老年病人病情造成人为的花费，以及延误治疗以增加长期的治疗费用。     

Left ventricular pseudoaneurysm after mitral valve replacement

Development of left ventricular pseudoaneurysm is a rare complication of mitral valve surgery and requires urgent surgical intervention. We describe a case of pseudoaneurysm of membranous septum following repeat mitral valve replacement with the use of multimodality imaging.