P2X4 receptor is a glycosylated cardiac receptor mediating a positive inotropic response to ATP

Although P2X receptors are suggested to play a role in synaptic neurotransmission, the specific physiological role of each P2X receptor subtype remains largely unknown. We used cultured chick embryo ventricular myocytes as a model to study a potential physiological role of the P2X(4) receptor in mediating the positive inotropic effect of ATP. The chick P2X4 receptor (cP2X(4)R) mRNA was expressed in the heart and the pharmacological features of the ATP-induced positive inotropic response were similar to those of the cP2X(4)R in terms of insensitivity to blockade by known P2 receptor antagonists and the ineffectiveness of adenosine 5'-(alpha,beta-methylene)triphosphate as an agonist. Treatment of myocytes with antisense oligonucleotides specific to the 5' region of cP2X(4)R abrogated the P2 agonist-stimulated (45)Ca influx. Similarly, antisense oligonucleotide treatment also blocked the 2-methylthio-ATP-stimulated increase in contractile amplitude. The data suggest that the native P2X(4) receptor is involved in mediating the P2 agonist-stimulated response in the heart. In characterizing the biochemical property of the P2X(4) receptor, antibody against cP2X(4)R detected a 44-kDa and a 58-kDa protein in the immunoblot. Inhibition of N-linked glycosylation by tunicamycin converted the 58-kDa protein to the 44-kDa protein, suggesting that the 58-kDa protein was a glycosylated P2X(4) receptor. The nonglycosylated 44-kDa P2X(4) receptor was resistant to various detergent/aqueous extraction, consistent with a role of glycosylation in maintaining its detergent solubility and hydrophilicity. Cross-linking the cell surface proteins with N-hydroxysuccinimide-SS-biotin followed by affinity precipitation with streptavidin-conjugated agarose and subsequent immunoblotting with anti-cP2X(4)R showed that only the glycosylated 58-kDa P2X(4) receptor was expressed on the cell surface, indicating an important role of glycosylation for the receptor's localization on the plasma membrane. These data revealed a novel physiologic function of the P2X(4) receptor and suggested the importance of N-linked glycosylation in its cell surface expression and detergent solubility.     

Distribution and sampling of the whiteflies Aleurothrixus floccosus, Dialeurodes citri, and Parabemisia myricae (Homoptera: Aleyrodidae) in citrus in Spain

From 1993 to 1995 data sets were collected from four citrus groves in Valencia, Spain, to determine the distribution patterns of eggs and nymphs of Aleurothrixus floccosus (Maskell), Dialeurodes citri (Ashmead), and Parabemisia myricae (Kuwana) on leaves, and to develop reliable sampling plans for estimating densities of immature whiteflies. A. floccosus showed higher aggregation than the other two species. The dispersion index b from the Taylor power law did not vary between different developing stages for A. floccosus and D. citri, reaching overall values of 1.70 and 1.53, respectively. In P. myricae, b was 1.60 for eggs and N1, and 1.46 for the remaining nymphs. The minimum number of leaves to estimate the population density with a coefficient of variation of 0.25 for densities above 10 immature whiteflies per leaf was 40 for D. citri and P. myricae, and 250 for A. floccosus. Binomial sampling programs for the three species were rejected for pest management purposes due to the high sample sizes required. The enumerative procedure of counting the number of insects per leaf appears to be the most suitable method for D. citri and P. myricae. For A. floccosus an index of occupation (from 0 to 10) linearly related to the proportion of the leaf undersurface occupied by this insect was found to be reliable and time-saving. Examining 150 leaves with this index achieves the desired relative variation level of 0.25 for most population densities usually found in commercial groves.     

A mathematical model of the response of semicircular canal and otolith to head rotation under gravity

The mathematical model of the system composed of two sensors: semicircular canal and sacculus, is presented. The system is described by three series of blocks: biomechanical block, mechanoelectrical transduction mechanism and hair cell ionic currents and membrane potential dynamics. The response of the aforecited system to various stimuli (head rotation under gravity and falling) was investigated. The identification of the model parameters was fulfilled for the experimental data, obtained for the axolotle (Ambystoma tigrinum) in Institute of Physiology, Autonomous University of Puebla, Mexico. The comparative analysis of canal and sacculus membrane potential was realized.     

Overexpression of WISP-1 down-regulated motility and invasion of lung cancer cells through inhibition of Rac activation

Wnt-induced-secreted-protein-1 (WISP-1) is a cysteine-rich, secreted factor belonging to the CCN family. These proteins have been implicated in the inhibition of metastasis; however, the mechanisms involved have not been described. We demonstrated that overexpression of WISP-1 in H460 lung cancer cells inhibited lung metastasis and in vitro cell invasion and motility. We investigated the possibility that WISP-1 may regulate activation of Rac, a small GTPase important for cytoskeletal reorganizations during motility. In an indirect assay, WISP-1-expressing cells exhibited marked reduction in Rac activation compared with control cells. Blocking antibodies to alpha(v)beta(5) and alpha(1) integrins restored Rac activation in WISP-1 cells, suggesting that the inhibitory effect of WISP-1 on Rac lies downstream of integrins. Constitutively activated Rac mutant (RacG12V) was transfected into WISP-1 cells to restore Rac activation and these WISP-1/RacG12V transfectants were used for further studies. We performed microarray and real-time PCR analyses to identify genes involved in invasion that may be differentially regulated by WISP-1. Here, we showed decreased expression of metalloproteinase-1 (MMP-1) in WISP-1 cells compared with controls but increased expression in WISP-1/RacG12V cells. In an invasion assay across collagen I, an MMP-1 target matrix, WISP-1 cells were significantly less invasive compared with controls, whereas WISP-1/RacG12V cells showed elevated invasion levels. This work illustrates a negatively regulated pathway by WISP-1 involving integrins and Rac in the down-regulation of invasion.     

Fetal alcohol exposure alters neurosteroid modulation of hippocampal N-methyl-D-aspartate receptors

The actions of ethanol on brain ligand-gated ion channels have important roles in the pathophysiology of alcohol-related neurodevelopmental disorders and fetal alcohol syndrome. Studies have shown that N-methyl-d-aspartate (NMDA) receptors are among the ligand-gated ion channels affected by prenatal ethanol exposure. We exposed pregnant dams to an ethanol-containing liquid diet that results in blood ethanol levels near the legal intoxication limit in most states (0.08%). Primary cultures of hippocampal neurons were prepared from the neonatal offspring of these dams, and NMDA receptor function was assessed by patch clamp electrophysiological techniques after 6-7 days in culture in ethanol-free media. Unexpectedly, we did not detect any changes in hippocampal NMDA receptor function at either the whole-cell or single-channel levels. However, we determined that fetal alcohol exposure alters the actions of the neurosteroids pregnenolone sulfate and pregnenolone hemisuccinate, which potentiate NMDA receptor function. Western immunoblot analyses demonstrated that this alteration is not due to a change in the expression levels of NMDA receptor subunits. Importantly, in utero ethanol exposure did not affect the actions of neurosteroids that inhibit NMDA receptor function. Moreover, the actions of pregnenolone sulfate on type A gamma-aminobutyric acid and non-NMDA receptor function were unaltered by ethanol exposure in utero, which suggests that the alteration is specific to NMDA receptors. These findings are significant because they provide, at least in part, a plausible mechanistic explanation for the alterations in the behavioral responses to neurosteroids found in neonatal rats prenatally exposed to ethanol and to other forms of maternal stress (Zimmerberg, B., and McDonald, B. C. (1996) Pharmacol. Biochem. Behav. 55, 541-547).     

Receptor-dependent cell stress and amyloid accumulation in systemic amyloidosis

Accumulation of fibrils composed of amyloid A in tissues resulting in displacement of normal structures and cellular dysfunction is the characteristic feature of systemic amyloidoses. Here we show that RAGE, a multiligand immunoglobulin superfamily cell surface molecule, is a receptor for the amyloidogenic form of serum amyloid A. Interactions between RAGE and amyloid A induced cellular perturbation. In a mouse model, amyloid A accumulation, evidence of cell stress and expression of RAGE were closely linked. Antagonizing RAGE suppressed cell stress and amyloid deposition in mouse spleens. These data indicate that RAGE is a potential target for inhibiting accumulation of amyloid A and for limiting cellular dysfunction induced by amyloid A.     

Prospecting of potentially probiotic lactic acid bacteria from bovine mammary ecosystem: imminent partners from bacteriotherapy against bovine mastitis

International Microbiology - Mastitis is one of the most important causes of loss of cattle production, burdening producers due to the increased cost of milk production and decreased herd...     

Alleviation of metal stress by Pseudomonas orientalis and Chaetomium cupreum strains and their effects on Eucalyptus globulus growth promotion

Plant and Soil - More sustainable agricultural systems, which contribute to C sequestration and biological N fixation, require accurate quantification of plant C and N inputs into soils. This has...     

Cercopithecine and Colobine Abundance Across Protected and Unprotected Land in the Greater Mahale Ecosystem,Western Tanzania

International Journal of Primatology - Most primates live in unprotected land where abundances and threats may differ from those in protected areas. We therefore need to establish population...