Osmotic swelling-provoked release of organic osmolytes in human intestinal epithelial cells

Human Intestine 407 cells respond to osmotic cell swelling by the activation of Cl(-)- and K(+)-selective ionic channels, as well as by stimulating an organic osmolyte release pathway readily permeable to taurine and phosphocholine. Unlike the activation of volume-regulated anion channels (VRAC), activation of the organic osmolyte release pathway shows a lag time of approximately 30-60 s, and its activity persists for at least 8-12 min. In contrast to VRAC activation, stimulation of organic osmolyte release did not require protein tyrosine phosphorylation, active p21(rho), or phosphatidylinositol 3-kinase activity and was insensitive to Cl(-) channel blockers. Treatment of the cells with putative organic anion transporter inhibitors reduced the release of taurine only partially or was found to be ineffective. The efflux was blocked by a subclass of organic cation transporter (OCT) inhibitors (cyanine-863 and decynium-22) but not by other OCT inhibitors (cimetidine, quinine, and verapamil). Brief treatment of the cells with phorbol esters potentiated the cell swelling-induced taurine efflux, whereas addition of the protein kinase C (PKC) inhibitor GF109203X largely inhibited the response, suggesting that PKC is involved. Increasing the level of intracellular Ca(2+) by using A-23187- or Ca(2+)-mobilizing hormones, however, did not affect the magnitude of the response. Taken together, the results indicate that the hypotonicity-induced efflux of organic osmolytes is independent of VRAC and involves a PKC-dependent step.     

Intrinsic Innervation of the Chicken Lower Digestive Tract

We have studied the different components of the enteric nervous system in the rectum and cloaca of the chicken by means of hystochemical and immunohistochemical techniques. We found cholinergic neuronal bodies as well as nervous fibers, which constitute part of the Meissner and Auerbach plexuses. We also observed plentiful catecholaminergic fibers in both plexuses, though there were no catecholaminergic neuronal bodies. With respect to the Vasoactive Intestinal Peptide (VIP) and substance P (SP) positive peptidergic innervation, only positive fibers were found, which were less abundant than in the other zones of the gastrointestinal tract. The optic microscopy results were confirmed by electron microscopy.     

Parenchymal cells purified from Xenopus liver and maintained in primary culture synthesize vitellogenin in response to estradiol-17β and serum albumin in response to dexamethasone

Xenopus liver was disaggregated by perfusion with collagenase. The released cells were separated according to their equilibrium densities on gradients of Metrizamide. Highly purified populations of parenchymal cells, sinusoidal cells, and melanocytes were obtained. All the parenchymal cells in an animal, before, during, and after hormone stimulation, are contained within a single density peak and subpopulations are not observed. Normal female parenchymal cells are less dense than normal male cells and estrogen stimulation causes a decrease in the peak density of the parenchymal cell population. Electron microscopic examination revealed the appearance and disappearance of lipid vacuoles in parenchymal cells following estrogen treatment. We hypothesize that the changing lipid content of these cells accounts for the shift in cell density. Immunofluorescent staining revealed that all liver parenchymal cells contain either vitellogenin or serum albumin, depending upon the prior treatment with hormones in vivo. Primary cultures of purified parenchymal and sinusoidal cells were established and were found to secrete different sets of proteins. The addition of estradiol-17β to cultures of parenchymal cells from either male or female frogs induces the synthesis and secretion of vitellogenin and two other polypeptides. Furthermore, the synthesis and secretion of polypeptides normally produced by parenchymal cells are curtailed as a result of estrogen treatment. Addition of glucocorticoids to a similar population of cells produces an increase in the synthesis and secretion of polypeptides, one of which is serum albumin. These results demonstrate that every parenchymal cell is responsive to two different classes of steroid hormones, estrogens and glucocorticoids, and in response to these hormones the same cells can synthesize and secrete alternate sets of polypeptides.     

Structural characteristics of algal communities in thermally altered artificial streams

Algal community structure on natural substrates of thermally altered artificial streams was studied for one year. The streams were fed by a natural blackwater stream near Aiken, South Carolina. Temperature-related shifts in the abundance of major species were demonstrated. Red algae were absent from a stream heated 12·5°C above ambient, but remained abundant in streams heated 7·5°C or less. Water temperatures above 30°C produced blue-green algal dominance and eliminated several indigenous species. Substrate specificity was exhibited by all major taxa. Several taxa were abundant only on the bottom sediments and some showed a distinct affinity for either sand or silt, the principal bottom types.     

Temperature-regulated expression of bacterial virulence genes

Virulence gene expression in most bacteria is a highly regulated phenomenon, affected by a variety of parameters including osmolarity, pH, ion concentration, iron levels, growth phase, and population density. Virulence genes are also regulated by temperature, which acts as an 'on-off' switch in a manner distinct from the more general heat-shock response. Here, we review temperature-responsive expression of virulence genes in four diverse pathogens.     

Identification of potential bladder progenitor cells in the trigone

Urothelial cells are specialized epithelial cells in the bladder that serve as a barrier toward excreted urine. The urothelium consists of superficial cells (most differentiated cells), intermediate cells, and basal cells; the latter have been considered as urothelium progenitor cells. In this study, BrdU or EdU was administrated to pregnant mice during E8–E13 for 2 consecutive days when bladder development occurs. The presence of label retaining cells was investigated in bladders from offspring. In 6 months old mice ~1% of bladder cells retained labeling. Stem cell markers as defined for other tissues (e.g., p63, CD44, CD117, trop2) co-localized or were in close vicinity to label retaining cells, but they were not uniquely limited to these cells. Remarkably, label retaining cells were distributed in all three cell layers (p63+, CK7+, and CK20+) of the urothelium and concentrated in the bladder trigone. This study demonstrates that bladder progenitor cells are present in all cell layers and reside mostly in the trigone. Understanding the geographic location of slow cycling cells provides crucial information for tissue regenerative purposes in the future.     

Isolation from cattle of a prion strain distinct from that causing bovine spongiform encephalopathy

To date, bovine spongiform encephalopathy (BSE) and its human counterpart, variant Creutzfeldt-Jakob disease, have been associated with a single prion strain. This strain is characterised by a unique and remarkably stable biochemical profile of abnormal protease-resistant prion protein (PrP(res)) isolated from brains of affected animals or humans. However, alternate PrP(res) signatures in cattle have recently been discovered through large-scale screening. To test whether these also represent separate prion strains, we inoculated French cattle isolates characterised by a PrP(res) of higher apparent molecular mass--called H-type--into transgenic mice expressing bovine or ovine PrP. All mice developed neurological symptoms and succumbed to these isolates, showing that these represent a novel strain of infectious prions. Importantly, this agent exhibited strain-specific features clearly distinct from that of BSE agent inoculated to the same mice, which were retained on further passage. Moreover, it also differed from all sheep scrapie isolates passaged so far in ovine PrP-expressing mice. Our findings therefore raise the possibility that either various prion strains may exist in cattle, or that the BSE agent has undergone divergent evolution in some animals.     

Synthesis and biological activity of the first cyclic biphalin analogues

Biphalin is a linear octapeptide with strong opioid activity. Its structure is based on two identical sequences derived from enkephalins joined C-terminal to C-terminal by an hydrazide bridge (Tyr-D-Ala-Gly-Phe-NH-NH<--Phe<--Gly<--D-Ala<--Tyr). In this study we present the design, synthesis, and biological evaluation of the first cyclic biphalin analogues. d-Alanine residues in positions 2, 2' of the parent peptide were replaced by d- and l-cysteine and an intramolecular disulfide bond between the cysteine thiol groups was introduced. We obtained two cyclic analogues with quite different biological profiles.