Tight control of the amount of yeast plasma membrane ATPase during changes in growth conditions and gene dosage

The activity of the plasma membrane ATPase in growing yeast is increased by low pH and by glucose, conditions which result in a higher demand for proton pumping. The amount of enzyme is not significatively modified under these conditions. The amount of ATPase is only slightly increased by introducing extra copies of its gene in autonomous plasmids. In addition, the expression of the ATPase gene in a multi-copy plasmid causes a reduction of the copy number of the plasmid and slows growth. Therefore, overexpression of the ATPase is detrimental for the cell, justifying a regulatory mechanism based on increasing the catalytic activity and not the amount of enzyme.     

Nitroso-aldicarb induces sister-chromatid exchanges in human lymphocytes in vitro

Nitroso-aldicarb was tested for its ability to induce sister-chromatid exchanges (SCE) and cell-cycle delay in human peripheral blood lymphocytes in vitro. This derivative of aldicarb induced a dose-dependent increase in SCE values per cell. In addition, a slight decrease in the successive mitotic progression of cells in culture was observed.     

High level of divergence of male-reproductive-tract proteins, between Drosophila melanogaster and its sibling species, D. simulans

We compared male-reproductive-tract polypeptides of Drosophila melanogaster and D. simulans by using two-dimensional gel electrophoresis. Approximately 64% of male-reproductive-tract polypeptides were identical between two randomly chosen isofemale lines from these two species, compared with 83% identity for third-instar imaginal wing-disc polypeptides. Qualitatively similar differences were found between reproductive tracts and imaginal discs when D. sechellia was compared with D. melanogaster and with D. simulans. When genic polymorphism was taken into account, approximately 10% of male- reproductive-tract polypeptides were apparently fixed for different alleles between D. melanogaster and D. simulans; this proportion is the same as that found for soluble enzymes by one-dimensional gel electrophoresis. Strikingly, approximately 20% of male-reproductive- tract polypeptides of either D. melanogaster or D. simulans had no detectable homologue in the other species. We propose that proteins of the Drosophila male reproductive tract may have diverged more extensively between species than have other types of proteins and that much of this divergence may involve large changes in levels of polypeptide expression.      

Pre-induction priming of the uterine cervix with oral prostaglandin E2 and a placebo

A double blind study was undertaken to determine the effectiveness or oral prostaglandin E2 as a means of improving the pelvic score prior to induction of labour. 48 patients who were greater than 37 were gestation and who had Bishop scores of less than 6 entered the study. Ten tablets were given on an hourly regime. Of 25 patients in the prostaglandin group, 17 were considered successes (68.0%), whereas of 23 patients who received a placebo, 9 were successes (39.1%). No adverse effects were recorded. Prostaglandin E2 is therefore considered a safe and effective method for priming the unfavourable cervix prior to induction of labour.     

Monoclonal antibodies to rabbit liver cytochrome P-448

Cytochrome P-448 (mol wt 55,000 Daltons) from rabbit liver was purified to a specific content of 16.6 nmol/mg. Mice were immunised with this preparation, their spleens removed and dissociated lymphocytes hybridised with myeloma cells. Four monoclonal antibodies against cytochrome P-448 were raised and partially characterised. All four antibodies interacted with cytochrome P-448 in intact microsomal fractions and selectively immunoadsorbed cytochrome P-448 from solubilised microsomal preparations. One of the antibodies inhibited benzo[a] pyrene hydroxylase activity in a reconstituted system, one had no effect on activity and two increased activity. The possible applications of such antibodies are discussed.     

Life history and production of the burrowing mayfly Ephoron virgo (Olivier, 1791) (Ephemeroptera: Polymitarcyidae) in the lower Ebro river: a comparison after 18 years

The life history of the burrowing mayfly Ephoron virgo (Olivier, 1791) (Ephemeroptera: Polymitarcyidae) was studied during spring and summer 2005 in the lower Ebro river (Catalonia) and compared to a previous study performed in 1987 (Ibáñez, Escosa, Muñoz and Prat 1991). The results showed an advancement of Ephoron virgo life cycle and an increase of production estimates. In 2005 larval development reached the maximum size one month earlier than in 1987, and adult emergence peak began three weeks earlier. Comparing adult sex ratios (F:M), there was a major presence of females in 2005 (1:4), while the opposite was observed in 1987 (2:1). Secondary production was higher in 2005 than in 1987, obtaining 950 mg dry weight/m²/year with the increment summation method and 1080 mg dry weight/m²/year using the removal summation method. Higher water temperatures were measured for the entire 2005 larval growth period, which were related to higher air temperatures. Therefore, that temperature increment was likely the main cause of changes observed in the Ephoron virgo life cycle.     

An Extracellular Ion Pathway Plays a Central Role in the Cooperative Gating of a K2P K+ Channel by Extracellular pH

Proton-gated TASK-3 K⁺ channel belongs to the K_2P family of proteins that underlie the K⁺ leak setting the membrane potential in all cells. TASK-3 is under cooperative gating control by extracellular [H⁺]. Use of recently solved K_2P structures allows us to explore the molecular mechanism of TASK-3 cooperative pH gating. Tunnel-like side portals define an extracellular ion pathway to the selectivity filter. We use a combination of molecular modeling and functional assays to show that pH-sensing histidine residues and K⁺ ions mutually interact electrostatically in the confines of the extracellular ion pathway. K⁺ ions modulate the pK_a of sensing histidine side chains whose charge states in turn determine the open/closed transition of the channel pore. Cooperativity, and therefore steep dependence of TASK-3 K⁺ channel activity on extracellular pH, is dependent on an effect of the permeant ion on the channel pH_o sensors.     

Seasonal Habitat Use of Agoutis (Dasyprocta azarae) is Driven by the Palm Attalea phalerata in Brazilian Pantanal

Resource availability can influence animal movement causing changes in home‐range size and arrangement between seasons. We investigated the influence of acuri palm (Attalea phalerata) on the occupancy of agouti Dasyprocta azare during both the dry and rainy seasons, as well as the abandonment probabilities in the transition between seasons in the Brazilian Pantanal. The agoutis occupied a high proportion of the forested areas in the rainy season (0.83), but the occupancy decreased in the dry season (0.39). In the rainy season, occupancy by agoutis was not correlated with acuri palm availability, while in the dry season, it was positively correlated with the palm's availability. The acuri palm availability also drove the agoutis' probability of site abandonment from the rainy to the dry season, with higher abandonment probability in sites with low acuri palm availability. These findings show that this large‐seeded palm can be an important resource for the agoutis' populations during the fruit‐scarcity period. The acuri palm seeds may be particularly important for agoutis using fragmented forests, given that the large‐seeded palms are able to persist even in small fragments, which is untrue for other important resource.