Nitrogen Oxyanion-dependent Dissociation of a Two-component Complex That Regulates Bacterial Nitrate Assimilation

Nitrogen is an essential nutrient for growth and is readily available to microbes in many environments in the form of ammonium and nitrate. Both ions are of environmental significance due to sustained use of inorganic fertilizers on agricultural soils. Diverse species of bacteria that have an assimilatory nitrate/nitrite reductase system (NAS) can use nitrate or nitrite as the sole nitrogen source for growth when ammonium is limited. In Paracoccus denitrificans, the pathway-specific two-component regulator for NAS expression is encoded by the nasT and nasS genes. Here, we show that the putative RNA-binding protein NasT is a positive regulator essential for expression of the nas gene cluster (i.e. nasABGHC). By contrast, a nitrogen oxyanion-binding sensor (NasS) is required for nitrate/nitrite-responsive control of nas gene expression. The NasS and NasT proteins co-purify as a stable heterotetrameric regulatory complex, NasS-NasT. This protein-protein interaction is sensitive to nitrate and nitrite, which cause dissociation of the NasS-NasT complex into monomeric NasS and an oligomeric form of NasT. NasT has been shown to bind the leader RNA for nasA. Thus, upon liberation from the complex, the positive regulator NasT is free to up-regulate nas gene expression.     

Analysis of four microsatellite markers on the long arm of chromosome 9 by meiotic recombination in flow-sorted single sperm.

Meiotic recombination in flow-sorted single sperm was used to analyze four highly polymorphic microsatellite markers on the long arm of chromosome 9. The microsatellites comprised three tightly linked markers: 9CMP1 (D9S109), 9CMP2 (D9S127), and D9S53, which map to 9q31, and a reference marker, ASS, which is located in 9q34.1. Haplotypes of single sperm were assessed by using PCR in a single-step multiplex reaction to amplify each locus. Recombinant haplotypes were identified by their relative infrequency and were analyzed using THREELOC, a maximum-likelihood-analysis program, and an adaptation of CRI-MAP. The most likely order of these markers was cen-D9S109-D9S127-D9S53-ASS-tel with D9S109, D9S127, and D9S53 being separated by a genetic distance of approximately 3%. The order of the latter three markers did not however achieve statistical significance using the THREELOC program.     

Ueber die Lehensweise vonSlrigops habroplilus, dem Kakapo oder Nachtpapageien Neuseeland's

Ohne Zusammenfassungübersetzt von Dr. G. Hartlaub.     

Heat shock protein 27 is increased in cyanotic tetralogy of Fallot myocardium and is associated with improved cardiac output and contraction

Tetralogy of Fallot (TOF) is a congenital heart condition in which the right ventricle is exposed to cyanosis and pressure overload. Patients have an increased risk of right ventricle dysfunction following corrective surgery. Whether the cyanotic myocardium is less tolerant of injury compared to non-cyanotic is unclear. Heat shock proteins (HSPs) protect against cellular stresses. The aim of this study was to examine HSP 27 expression in the right ventricle resected from TOF patients and determine its relationship with right ventricle function and clinical outcome. Ten cyanotic and ten non-cyanotic patients were studied. Western blotting was used to quantify HSP 27 in resected myocardium at (1) baseline (first 15 min of aortic cross clamp and closest representation of pre-operative status) and (2) after 15 min during ischemia until surgery was complete. The cyanotic group had significantly increased haematocrit, lower O₂ saturation, thicker interventricular septal wall thickness and released more troponin-I on post-operative day 1 (p?<?0.05). HSP 27 expression was significantly increased in the <15 min cyanotic compared to the <15 min non-cyanotic group (p?=?0.03). In the cyanotic group, baseline HSP 27 expression also significantly correlated with oxygen extraction ratio (p?=?0.028), post-operative basal septal velocity (p?=?0.036) and mixed venous oxygen saturation (p?=?0.02), markers of improved cardiac output/contraction. Increased HSP 27 expression and associated improved right ventricle function and systemic perfusion supports a cardio-protective effect of HSP 27 in cyanotic TOF.     

Heat Shock Protein 27 Is Spatially Distributed in the Human Placenta and Decreased during Labor

Placental oxidative stress is a feature of human labor. Heat shock proteins (HSPs) play a key role in cellular stress. We hypothesized that placental expression of the small HSP 27 would be altered during labor and expression would vary in different regions of the placenta. Six women in labor who delivered vaginally and 6 women not in labor, who were delivered by Cesarean section, were recruited. Four equally spaced pieces were sampled from the inner, middle and outer regions of each placenta (total 12 samples per placenta). HSP 27 expression was investigated by Western blot analysis and RT-PCR. For non-labor, there was less HSP 27 protein in the inner placenta region compared with both the middle region (p<0.05) and outer region (p<0.05). For labor, there was also less HSP 27 protein in the inner region compared with both the middle (p<0.02) and outer region (p<0.01). When the 3 regions of the placenta were compared for non-labor versus labor there was less HSP 27 in the labor group at both the inner (p<0.05) and middle regions (p<0.005) compared to non-labor. Similar to HSP 27 protein, there was less HSP 27 mRNA in the labor group in both the inner region (p<0.05) and middle region (p<0.02) compared to non-labor. This study suggests that placental HSP 27 may play a role in labor and is spatially controlled. The results have important implications for how data obtained from studies in the placenta can be influenced by sampling methods.     

Modulation of rat chorda tympani NaCl responses and intracellular Na+ activity in polarized taste receptor cells by pH

Mixture interactions between sour and salt taste modalities were investigated in rats by direct measurement of intracellular pH (pH(i)) and Na(+) activity ([Na(+)](i)) in polarized fungiform taste receptor cells (TRCs) and by chorda tympani (CT) nerve recordings. Stimulating the lingual surface with NaCl solutions adjusted to pHs ranging between 2.0 and 10.3 increased the magnitude of NaCl CT responses linearly with increasing external pH (pH(o)). At pH 7.0, the epithelial sodium channel (ENaC) blocker, benzamil, decreased NaCl CT responses and inhibited further changes in CT responses induced by varying pH(o) to 2.0 or 10.3. At constant pH(o), buffering NaCl solutions with potassium acetate/acetic acid (KA/AA) or HCO(3)(-)/CO(2) inhibited NaCl CT responses relative to CT responses obtained with NaCl solutions buffered with HEPES. The carbonic anhydrase blockers, MK-507 and MK-417, attenuated the inhibition of NaCl CT responses in HCO(3)(-)/CO(2) buffer, suggesting a regulatory role for pH(i). In polarized TRCs step changes in apical pH(o) from 10.3 to 2.0 induced a linear decrease in pH(i) that remained within the physiological range (slope = 0.035; r(2) = 0.98). At constant pH(o), perfusing the apical membrane with Ringer's solutions buffered with KA/AA or HCO(3)(-)/CO(2) decreased resting TRC pH(i), and MK-507 or MK-417 attenuated the decrease in pH(i) in TRCs perfused with HCO(3)(-)/CO(2) buffer. In parallel experiments, TRC [Na(+)](i) decreased with (a) a decrease in apical pH, (b) exposing the apical membrane to amiloride or benzamil, (c) removal of apical Na(+), and (d) acid loading the cells with NH(4)Cl or sodium acetate at constant pH(o). Diethylpyrocarbonate and Zn(2+), modification reagents for histidine residues in proteins, attenuated the CO(2)-induced inhibition of NaCl CT responses and the pH(i)-induced inhibition of apical Na(+) influx in TRCs. We conclude that TRC pH(i) regulates Na(+)-influx through amiloride-sensitive apical ENaCs and hence modulates NaCl CT responses in acid/salt mixtures.     

On the Emsian (Lower Devonian) arthropods of the Rhenish Slate Mountains: 2. The synziphosurineWillwerathia

Willwerathia laticeps (Størmer 1936) originally described as a eurypterid is reinterpreted as a synziphosurine belonging to Family WeinberginidaeRichter &Richter 1929. Recently collected material from the locality, from which the destroyed holotype comes, suggests thatWillwerathia possessed ten opisthosomal tergites, deduced from all available arrays of disarticulates.Willwerathia is the largest synziphosurine yet discovered with a carapace approximately 90 mm across. The occurrence of synziphosurines with eurypterids mirrors previously described preservational associations.