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Key points The digestive tract of larval and adult Drosophila is an excellent analogue of the mammalian gut. Enterocytes of the posterior midgut are separated by septa, with no paracellular path, and therefore perform both immune and transport functions., Using microperfusion electrophysiology, we show that larvae emerging from the embryo into sterile medium have symmetrical apical and basal membrane conductances while larvae emerging into non-sterile medium have apical membranes fivefold more conductive than basal membranes. The channels inserted into the apical membranes could originate in microbiata or host and mediate recognition of microbes., Entomopathogenic cyclic peptide toxins deplete intracellular ions reversibly, forming transient ion channels that do not conduct water, unlike an ionophore like nystatin that depletes ions irreversibly., We show the feasibility of studying the interaction of a single microbial species, or tractable combinatorials of microbial species, with only enterocytes in the primary epithelial barrier., Abstract Microbiota colonizing exposed epithelial surfaces are vital for sustenance of metazoan life, but communication between microbiota, epithelial cells and the host immune system is only beginning to be understood. We address this issue in the posterior midgut epithelium of Drosophila larvae where nutrient transport and immune functions are exclusively transcellular. We showed that larvae emerging into a sterile post-embryonic environment have symmetrical apical and basal membranes. In contrast, larvae emerging into non-sterile media, the source of microbiota, have markedly asymmetrical membranes, with apical membrane conductance more than fivefold higher than the basal membrane. As an example of pathogen action, we showed that the entomopathogenic fungal toxin destruxin A (Dx) depleted intracellular ions. Reversibility of action of Dx was verified by bilayer reconstitution in forming transient non-specific channels that conduct ions but not water. Dx was also less effective from the apical side as compared to the basal side of the epithelium. We also showed that intercellular septa are not conductive in non-sterile cells, even though most cells are isopotential. Luminal microbiota therefore impart asymmetry to the epithelium, by activation of apical membrane conductance, enhancing inter-enterocyte communication, separated by insulating septa, via the gut lumen. These results also open the possibility of studying the basis of bidirectional molecular conversation specifically between enterocytes and microbiota that enables discrimination between commensals and pathogens, establishment of the former, and elimination of the latter. [ABSTRACT FROM AUTHOR]

Key points The cortical collecting duct (CCD) plays an essential role in sodium homeostasis by fine-tuning the amount of sodium that is excreted in the urine., Ex vivo, the microperfused CCD reabsorbs sodium in the absence of lumen-to-bath concentration gradients., In the present study, we show that, in the presence of physiological lumen-to-bath concentration gradients, and in the absence of endocrine, paracrine and neural regulation, the mouse CCD secretes sodium, which represents a paradigm shift., This secretion occurs via the paracellular route, as well as a transcellular pathway that is energized by apical H+/K+-ATPase type 2 pumps operating as Na+/K+ exchangers., The newly identified transcellular secretory pathway represents a physiological target for the regulation of sodium handling and for anti-hypertensive therapeutic agents., Abstract In vitro microperfusion experiments have demonstrated that cortical collecting ducts (CCDs) reabsorb sodium via principal and type B intercalated cells under sodium-depleted conditions and thereby contribute to sodium and blood pressure homeostasis. However, these experiments were performed in the absence of the transepithelial ion concentration gradients that prevail in vivo and determine paracellular transport. The present study aimed to characterize Na+, K+ and Cl− fluxes in the mouse CCD in the presence of physiological transepithelial concentration gradients. For this purpose, we combined in vitro measurements of ion fluxes across microperfused CCDs of sodium-depleted mice with the predictions of a mathematical model. When NaCl transport was inhibited in all cells, CCDs secreted Na+ and reabsorbed K+; Cl− transport was negligible. Removing inhibitors of type A and B intercalated cells increased Na+ secretion in wild-type (WT) mice but not in H+/K+-ATPase type 2 (HKA2) knockout mice. Further inhibition of basolateral NaCl entry via the Na+-K+-2Cl− cotransporter in type A intercalated cells reduced Na+ secretion in WT mice to the levels observed in HKA2−/− mice. With no inhibitors, WT mouse CCDs still secreted Na+ and reabsorbed K+. In vivo, HKA2−/− mice excreted less Na+ than WT mice after switching to a high-salt diet. Taken together, our results indicate that type A intercalated cells secrete Na+ via basolateral Na+-K+-2Cl− cotransporters in tandem with apical HKA2 pumps. They also suggest that the CCD can mediate overall Na+ secretion, and that its ability to reabsorb NaCl in vivo depends on the presence of acute regulatory factors. [ABSTRACT FROM AUTHOR]

Objectives: Aim of this clinical study was to evaluate the angiosome concept with regard to the microcirculation of the foot in patients with CLI and to evaluate its relevance by means of combined laser Doppler flowmetrie and white-light tissue spectrophotometry. Methods: Twenty-eight patients who underwent leg revascularization in the stage of CLI were prospectively examined. The microperfusion was assessed by light guided spectrophotometry. The measuring points were set according to the angiosome concept into direct and indirect revascularized areas of the foot. Investigations were performed pre and postinterventionally and after 4 and 12 weeks in baseline-position as well as in an elevated position of the leg. Results: Microcirculation parameters (oxygen saturation, blood flow, velocity) of the revascularized leg showed a significant increase in elevation and baseline position compared to the preoperative values in most analyses. No significant differences between the direct and indirect revascularized angiosome were apparent. Conclusion: The light-guided spectrophotometry measurement proved to be feasible in terms of measuring changes in the microcirculation after leg revascularization. However, our data do not support the value of the "angiosome concept" concerning the individual changes in microperfusion of the foot in patients with CLI. [ABSTRACT FROM AUTHOR]

Purpose Anastomotic leakage is associated with increased morbidity and mortality. However, there is no accurate tool to predict its occurrence. We evaluated the predictive value of visible light spectroscopy (VLS), a novel method to measure tissue oxygenation [saturated O2 (StO2)], for anastomotic leakage of the colon and the rectum. Method Oxygen saturation in the bowel was measured in 77 colorectal resections. The anastomosis was between 2 and 30 cm (mean 13 cm) from the anal verge. The oxygen saturation was measured in the colon and rectum before and after anastomosis construction. This was compared with a reference measurement in the caecum. Data on postoperative complications were prospectively collected. Results Anastomotic leakage occurred in 14 (18%) patients. When compared with a leaking anastomosis, normal anastomoses showed rising O2 values during the operation (mean StO2 72.1 ± 9.0–76.7 ± 8.0 vs 73.9 ± 7.9–73.1 ± 7.4) ( P ≤ 0.05). There were also higher StO2 values in the caecum compared with those which ultimately leaked (73.6 ± 5.7 normal anastomoses , 69.6 ± 5.6 anastomotic leaks) ( P ≤ 0.05). Both StO2 values were predictive of anastomotic leakage. Conclusion Tissue oxygenation O2 appears to be a potentially useful means of predicting anastomotic leakage after colorectal anastomosis. [ABSTRACT FROM AUTHOR]