Uptake of calcium by microvillous membranes of intestinal epithelial cells

Uptake or “binding” of Ca²⁺ ions by microvillous membranes occurs in the absence or presence of ATP. In its absence uptake is independent of temperature (3–37°C), reduced by the presence of other cations and is dependent upon pH and the number and type of “binding” sites of which there are at least two classes. Under certain conditions uptake of Ca²⁺ is increased by ATP. The degree of stimulation is dependent upon both the concentration of Ca²⁺ and ATP, the time and temperature of incubation and is partly dependent upon the presence of Mg²⁺ ions.     

Studies of insulin release and rat pancreatic islet metabolism with diastereomers of D-glucose

Studies of insulin release with diastereomers and other analogues of D-glucose demonstrated that only sugars which undergo oxidation to CO₂ stimulate insulin release by the pancreatic islet. None of the non-metabolizable diastereomers of glucose stimulated insulin release in the presence of a substimulatory concentration of glucose for fuel. Although 5.5 mM glucose formed 77% as much CO₂ as 16.7 mM mannose and twice that of 16.7 mM fructose, 5.5 mM glucose did not stimulate insulin release whereas 16.7 mM mannose and fructose did stimulate insulin release. These results indicate that the important stimulus for glucose-induced insulin release involves metabolism of glucose, but that the stimulus does not involve solely a fuel function of glucose.     

Kinetics and dynamics of annealing during sub-gel phase formation in phospholipid bilayers: A saturation transfer electron spin resonance study

The saturation transfer electron spin resonance (STESR) spectra of spin-labeled phosphatidylcholine have been used to follow the kinetics of conversion from the gel phase to the sub-gel phase in aqueous bilayers of dipalmitoyl phosphatidylcholine. This is a simple, well-defined model system for lipid domain formation in membranes. The integrated intensity of the STESR spectrum from the chain-labeled lipid first increases and then decreases with time of incubation in the gel phase at 0°C. The first, more rapid phase of the kinetics is attributed to the conversion of germ nuclei to growth nuclei of the sub-gel phase. The increase in STESR intensity corresponds to the reduction in chain mobility of spin labels located in the gel phase at the boundaries of the growth nuclei and correlates with the increase in the diagnostic STESR line height ratios over this time range. The second, slower phase of the kinetics is attributed to growth of the domains of the sub-gel phase. The decrease in STESR intensity over this time regime corresponds to exclusion of the spin-labeled lipids from the tightly packed sub-gel phase and correlates quantitatively with calibrations of the spin label concentration dependence of the STESR intensity in the gel phase. The kinetics of formation of the sub-gel phase are consistent with the classical model for domain formation and growth. At 0°C, the half-time for conversion of germ nuclei to growth nuclei is ∼7.7 h and domain growth of the sub-gel phase is characterized by a rate constant of 0.025 h^-1. The temperature dependence of the STESR spectra from samples annealed at 0°C suggests that the subtransition takes place via dissolution of sub-gel phase domains, possibly accompanied by domain fission.     

Serotonin paracrine signaling in tissue fibrosis

The molecule serotonin (5-hydroxytryptamine or 5-HT) is involved in numerous biological processes both inside and outside of the central nervous system. 5-HT signals through 5-HT receptors and it is the diversity of these receptors and their subtypes that give rise to the varied physiological responses. It is clear that platelet derived serotonin is critical for normal wound healing in multiple organs including, liver, lung heart and skin. 5-HT stimulates both vasoconstriction and vasodilation, influences inflammatory responses and promotes formation of a temporary scar which acts as a scaffold for normal tissue to be restored. However, in situations of chronic injury or damage 5-HT signaling can have deleterious effects and promote aberrant wound healing resulting in tissue fibrosis and impaired organ regeneration. This review highlights the diverse actions of serotonin signaling in the pathogenesis of fibrotic disease and explores how modulating the activity of specific 5-HT receptors, in particular the 5-HT2 subclass could have the potential to limit fibrosis and restore tissue regeneration. This article is part of a Special Issue entitled: Fibrosis: Translation of basic research to human disease.     

Synthesis of 2-ethylhexyl oleate catalyzed by Candida antarctica lipase immobilized on a magnetic polymer support in continuous flow

Bioprocess and Biosystems Engineering - This study investigated the synthesis of 2-ethylhexyl oleate catalyzed by Candida antarctica lipase immobilized on magnetic poly(styrene-co-divinylbenzene)...