Limits of life in hostile environments: no barriers to biosphere function?

Environments that are hostile to life are characterized by reduced microbial activity which results in poor soil- and plant-health, low biomass and biodiversity, and feeble ecosystem development. Whereas the functional biosphere may primarily be constrained by water activity (a w) the mechanism(s) by which this occurs have not been fully elucidated. Remarkably we found that, for diverse species of xerophilic fungi at a w values of = 0.72, water activity per se did not limit cellular function. We provide evidence that chaotropic activity determined their biotic window, and obtained mycelial growth at water activities as low as 0.647 (below that recorded for any microbial species) by addition of compounds that reduced the net chaotropicity. Unexpectedly we found that some fungi grew optimally under chaotropic conditions, providing evidence for a previously uncharacterized class of extremophilic microbes. Further studies to elucidate the way in which solute activities interact to determine the limits of life may lead to enhanced biotechnological processes, and increased productivity of agricultural and natural ecosystems in arid and semiarid regions.

Effect of pioglitazone on endothelial function in impaired glucose tolerance

Aim: Flow-mediated dilation (FMD) is a surrogate marker of endothelial function, which has been proposed as a barometer of vascular health. Impaired microvascular response to reactive hyperaemia is thought to be the mechanism behind reduced shear stress and subsequently impaired FMD, which has been associated with cardiovascular events. This study aims to assess the effect of pioglitazone on the vasculature of patients with impaired glucose tolerance (IGT).

Materials and Methods: Forty IGT patients with no cardiovascular disease were compared with 24 healthy age- and sex-matched controls. Endothelial function was assessed using FMD of the brachial artery. Adiponectin (ADN) levels were measured and insulin sensitivity was calculated using homeostasis model assessment of insulin resistance (HOMA-IR). A randomised double-blind placebo-controlled trial of the IGT subjects was then performed, with subjects receiving either pioglitazone 30 mg od or matched placebo for 12 weeks before the measurements were repeated.

Results: The IGT subjects had a significantly impaired FMD compared with the controls (p < 0.001). Diastolic shear stress (DSS) was also significantly reduced in IGT (p = 0.04). High molecular weight (HMW) ADN was significantly lower in the IGT group than in controls (p = 0.03). On analysis of the IGT group after 12 weeks treatment, FMD was significantly increased in the pioglitazone group compared with placebo (p = 0.03) as was endothelium-independent dilation (EID) (p = 0.03). A significant increase in total ADN (p < 0.001), HMW ADN (p < 0.001) and HMW/total ratio (p = 0.001) occurred in the pioglitazone group compared with placebo.

Conclusions: Pioglitazone improved endothelial function in IGT. Treatment with pioglitazone may reduce the risk of cardiovascular disease in this patient group.

Interstitial Cells in the Urinary Bladder-Localization and Function

Aims: This review summarizes the currently available literature on the localization and proposed functions of a novel group of cells in the urinary bladder known as interstitial cells or interstitial cells of Cajal (ICC).

Methods: On-line searches of "Pubmed" for bladder, c-Kit, ICC, interstitial cell and myofibroblast were performed to identify relevant studies for the review.

Results: The literature contains substantial data that several sub-populations of ICC are present in the wall of the mammalian urinary bladder. These are located in the lamina propria and within the detrusor with distinctive cell shapes and morphological arrangements. Bladder ICC are identified with transmission electron microscopy or by immunohistochemical labeling using antibodies to the Kit receptor which is an established ICC marker. Lamina propria-ICC form a loose network connected via Cx43 gap junctions and are associated with mucosal nerves. Detrusor ICC track the smooth muscle bundles and make frequent contacts with intramural nerves. Both groups of ICC exhibit spontaneous electrical and Ca²⁺-signalling and also respond to application of neurotransmitter substances including ATP and carbachol. There is emerging evidence that the expression of ICC is upregulated in pathophysiological conditions including the overactive bladder.

Conclusions: There is now a convincing body of evidence that specialized ICC are present in the urinary bladder making important associations with other cells that make up the bladder wall and possessing physiological properties consistent with a role of bladder activity modulation. Neurourol. Urodynam. 29: 82–87, 2010. © 2009 Wiley-Liss, Inc.