Prophylactic and curative effects of Bacopa monniera in gastric ulcer models.

Bacopa monniera Wettst. (BM, syn. Herpestis monniera L; Scrophulariaceae), is an Ayurvedic drug used as a rasayana. Its fresh juice was earlier reported to have significant antiulcerogenic activity. In continuation, methanolic extract of BM (BME) standardized to bacoside-A content (percentage-38.0 ± 0.9), when given in the dose of 10–50 mg/kg, twice daily for 5 days, showed dose-dependent anti-ulcerogenic on various gastric ulcer models induced by ethanol, aspirin, 2 h cold restraint stress and 4 h pylorus ligation. BME in the dose of 20 mg/kg, given for 10 days, twice daily showed healing effects against 50% acetic acid-induced gastric ulcers. Further work was done to investigate the possible mechanisms of its action by studying its effect on various mucosal offensive acid-pepsin secretion and defensive factors like mucin secretion, mucosal cell shedding, cell proliferation and antioxidant activity in rats. BME 20 mg/kg showed no effect on acid-pepsin secretion, increased mucin secretion, while it decreased cell shedding with no effect on cell proliferation. BME showed significant antioxidant effect per se and in stressed animals. Thus, the gastric prophylactic and curative effects of BME may be due to its predominant effect on mucosal defensive factors.     

Collagen receptors mediate early events in the attachment of epithelial (MDCK) cells

Summary Madin-Darby canine kidney (MDCK) cells kept in suspension culture for 12–15 hr displayed high-affinity binding sites for¹²⁵I-lathyritic (soluble) collagen (120,000/cell,K _D =30nm) and preferred collagens types I and IV over laminin or fibronectin as substrates during the first hour of attachment. On the other hand, after 4 hr, attachment to all four substrates was equally efficient. Upon challenge with a collagen substrate, the high-affinity sites were rapidly recruited on it (T1/2=6 min). Their occupancy by soluble collagen triggered the exocytosis of a second large population of low-affinity collagen binding sites that included laminin and seems to be involved in a second cell-attachment mechanism. These results are compatible with a twostep model of MDCK cell attachment to the substrate: first, via high-affinity collagen binding sites, and second, via laminin of cellular origin.     

Increased cholesterol content of erythrocyte and brain membranes in ethanol-tolerant mice

Mice were treated with ethanol for eight or nine days, using a liquid diet regimen known to produce physical dependence. In previous experiments, synaptosomal plasma membranes and erythrocyte ghosts from such ethanoltreated animals were found to be resistant to the fluidizing effects of ethanol in vitro, as measured by electron paramagnetic resonance. In the present experiments, corresponding membranes were analysed for phospholipid and cholesterol. The ratio of cholesterol to phospholipid was found to be significantly increased in both types of membrane after chronic ethanol treatment. The changed ratio was produced by an increase in cholesterol. There was little or no change in phospholipid content of the membranes. Increased cholesterol may explain the previously observed alteration of physical properties of the membranes.     

Glycosaminoglycans of the plasma membranes of renal tubule and liver cells

Glycosaminoglycans were isolated from plasma membranes of hepatic and renal tubule cells of guinea pig. Plasmalemma of renal tubule cells contained more total glycosaminoglycans, hyaluronic acid, chondroitin-4 sulfates and chondroitin-6 sulfates, and less dermatan sulfates and heparin sulfates than liver plasma membranes. These glycocalyx components, owing to their polyanionic properties, may have a role in the transport of water, ions, and macromolecules across the cell membrane.     

Genomic Patterns of Positive Selection at the Origin of Rust Fungi

Understanding the origin and evolution of pathogenicity and biotrophic life-style of rust fungi has remained a conundrum for decades. Research on the molecular mechanisms responsible for rust fungi evolution has been hampered by their biotrophic life-style until the sequencing of some rust fungi genomes. With the availability of multiple whole genomes and EST data for this group, it is now possible to employ genome-wide surveys and investigate how natural selection shaped their evolution. In this work, we employed a phylogenomics approach to search for positive selection and genes undergoing accelerated evolution at the origin of rust fungi on an assembly of single copy genes conserved across a broad range of basidiomycetes. Up to 985 genes were screened for positive selection on the phylogenetic branch leading to rusts, revealing a pervasive signal of positive selection throughout the data set with the proportion of positively selected genes ranging between 19.6–33.3%. Additionally, 30 genes were found to be under accelerated evolution at the origin of rust fungi, probably due to a mixture of positive selection and relaxation of purifying selection. Functional annotation of the positively selected genes revealed an enrichment in genes involved in the biosynthesis of secondary metabolites and several metabolism and transporter classes.     

Vacuolar apical compartment (VAC) in breast carcinoma cell lines (MCF-7 and T47D): failure of the cell-cell regulated exocytosis mechanism of apical membrane

Abstract. We have previously shown that an integral plasma membrane glycoprotein (AP2) is highly polarized to the apical domain in confluent Madin-Darby canine kidney (MDCK) epithelial cells. However, when the monolayers are prevented from forming intercellular contacts, approximately 60% of the AP2 cellular content is stored in the intracellular vacuolar apical compartment (VAC). In the current work we found that AP2 was present in the non-tumorigenic human mammary epithelial cell line MCF-10A. in the breast carcinoma cell lines MCF-7 and T47D, and in breast ductal carcinomas in vivo. By radioimmunoassay, an intracellular Compartment of AP2 was identified in the mammary cell lines in culture. In MCF-10A, this compartment behaved as in MDCK cells; namely it was observed only when the cells cannot form cell-cell contacts. However, in the carcinoma cell lines MCF-7 and T47D, a significant AP2 intracellular compartment was observed also under conditions permissive for the formation of intercellular contacts. These results were confirmed by immunofluorescence and immunoelectron microscopy experiments that showed VACs in MCF-7 and T47D, even in cells with extensive intercellular contacts. In MCF-7 cells, the addition of serum caused a partial decrease of the AP2 intracellular compartment. The exocytosis of VACs occurred towards the center of multi-cellular groups, forming intercellular lumens, similar to those transiently observed in MDCK cells and to structures described by others during embryo development. Altogether, these results suggest that VAC exocytosis is controlled by cell-cell contact signalling, which may be defective in carcinoma cells.     

Spatio-temporal convergence (STC) in otolith neurons

It has been recently demonstrated that some primary otolith afferents and most otolith-related vestibular nuclei neurons encode two spatial dimensions that can be described by two vectors in temporal and spatial quadrature. These cells are called broadly-tuned neurons. They are characterized by a non-zero tuning ratio which is defined as the ratio of the minimum over the maximum sensitivity of the neuron. Broadly-tuned neurons exhibit response gains that do not vary according to the cosine of the angle between the stimulus direction and the cell's maximum sensitivity vector and response phase values that depend on stimulus orientation. These responses were observed during stimulation with pure linear acceleration and can be explained by spatio-temporal convergence (STC) of primary otolith afferents and/or otolith hair cells. Simulations of STC of the inputs to primary otolith afferents and vestibular nuclei neurons have revealed interesting characteristics: First, in the case of two narrowly-tuned input signals, the largest tuning ratio is achieved when the input signals are of equal gain. The smaller the phase difference between the input vectors, the larger the orientation differences that are required to produce a certain tuning ratio. Orientation and temporal phase differences of 30–40° create tuning ratios of approximately 0.10–0.15 in target neurons. Second, in the case of multiple input signals, the larger the number of converging inputs, the smaller the tuning ratio of the target neuron. The tuning ratio depends on the number of input units, as long as there are not more than about 10. For more than 10–20 input vectors, the tuning ratio becomes almost independent of the number of inputs. Further, if the inputs comprise two populations (with different gain and phase values at a given stimulus frequency), the largest tuning ratio is obtained when the larger population has a smaller gain. These findings are discussed in the context of known anatomical and physiological characteristics of innervation patterns of primary otolith afferents and their possible convergence onto vestibular nuclei neurons.     

The apparent absence of serotonin-mediated vascular thermogenesis in perfused rat hindlimb may result from vascular shunting

Vasoconstriction by norepinephrine, angiotensin II and vasopressin in the constant-flow perfused rat hindlimb is associated with increased oxygen uptake and has given rise to the concept of vascular thermogenesis. In the present study serotonin (5-hydroxytryptamine, 5HT) was found to inhibit oxygen uptake by up to 40% in a dose dependent manner whilst inducing vasoconstriction in this model, whereas norepinephrine increased oxygen consumption by up to 100% during vasoconstriction. This contrasted with the perfused isolated rat mesenteric artery arcade in which serotonin stimulated oxygen uptake by up to 130% in association with vasoconstriction in a dose dependent manner similar to the previously described norepinephrine induced vascular thermogenesis in this arterial preparation. In both perfusion systems, changes in pressure and oxygen uptake mediated by serotonin were completely blocked by ketanserin. These results and evidence from dye washout studies suggest that serotonin-mediated vascular thermogenesis, if it occurs in the constant-flow hindlimb, is masked by vascular shunting.