MgATP-concentration dependence of protection of yeast vacuolar V-ATPase from inactivation by 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole supports a bi-site catalytic mechanism of ATP hydrolysis

Catalytic site occupancy of the yeast vacuolar V-ATPase during ATP hydrolysis in the presence of an ATP-regenerating system was probed using sensitivity of the enzyme to inhibition by 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl). The results show that, regardless of the presence or absence of the proton-motive force across the vacuolar membrane, saturation of V-ATPase activity at increasing MgATP concentrations is accompanied by only partial protection of the enzyme from inhibition by NBD-Cl. Both in the presence and absence of an uncoupler, complete protection of V-ATPase from inhibition by NBD-Cl requires MgATP concentrations that are significantly higher than those expected from the K(m) values for MgATP. The results are inconsistent with a tri-site model and support a bi-site model for a mechanism of ATP hydrolysis by V-ATPase.     

Day-to-day alteration of 24-hour sleep pattern immediately before and after giving birth

Sleep and Biological Rhythms - The current literature suggests that nighttime sleep is compromised during late pregnancy and early postpartum periods, but little is known about the 24-hour sleep...     

Development of enzyme-immunoassays based on egg yolk antibodies for the detection of mycotoxins

Enzyme-linked immunosorbent assays (ELISA) proved to be a fast and simple method for the detection of mycotoxins and other undesired contaminants in food and feed. The present study is focused on the optimisation and exploitation of the egg yolk antibody technology in order to develop competitive ELISAs for the detection of mycotoxins in cereals. Due to its importance as one of the most relevant Fusarium mycotoxins, the trichothecene deoxynivalenol (DON) was selected as representative. Chickens were immunised with different protein conjugates performing varying booster intervals. The antibodies were isolated by the poly(ethylene glycol) precipitation method according to Polson. By use of these antibodies an indirect competitive ELISA was developed for the detection of DON. First investigations of naturally contaminated wheat samples showed a good correspondence with results obtained by GC-ECD when calibration in blank wheat extracts was performed.     

Functional interaction between information processing pathways in Escherichia coli and the nature of Δ-H+ (redox)-sensing

Glucose taxis and O₂-taxis in Escherichia coli signal to flagella via a pathway that includes PTS^glc and adenylate cyclase. Information from a number of attractants and repellents is focused at the level of methy-accepting chemotaxis proteins (MCPs) and information is passed to flagella by a separate pathway. Mutants defective in adenylate cyclase (Δcya) had a residual taxis to glucose that was eliminated by preincubating the cells with MCP attractants, or by depleting the -CH₃ donor. A methyltransferase mutant had a decreased sensitivity to MCP repellents and this response was completely blocked by preincubating the cells with glucose. Likewise, the response of cells, depleted for -CH₃, towards repellents, was blocked if bacteria carried a pts mutation. It is concluded that PTS and MCP pathways exchange information. In cya cells, O₂ taxis was restored in the presence of maltose, an MCPII attractat. It is suggested that MCPII is an additional protonmotive force (pmf) sensor.     

Mechanisms of polarized targeting of the FSH receptor]

Gonadotropin and TSH receptors belong to a subgroup of G protein-coupled receptors. TSH and FSH receptor present a particular intracellular traffic: they present a polarized basolateral expression in thyroid follicular cells and in Sertoli cells respectively. By contrast, the LH receptor is expressed circumferentially in target gonadic cells. We expressed these receptors in MDCK cells (a well characterized model of polarized epithelial cells) to understand this difference of properties. We show that the three receptors have a polarized basolateral expression in these cells. All contain a basolateral targeting signal. Furthermore, gonadotropin receptors undergo a partial transcytosis which is not observed for the TSH receptor. We show that heterotrimeric G proteins play a role in this mechanism of transcytosis. This effect is not mediated by adenylate cyclase activation and involves a population of G proteins different from that involved in signal transduction. We thus used in vitro mutagenesis to delineate the basolateral localization signal of the FSH receptor. Surprisingly, the signal is localized in the C-terminal tail of the intracellular domain which is not conserved between the three receptors. It contains 14 amino-acids and its activity is mainly dependent on a tyrosine and a leucine residue. The basolateral localization signal of the FSHR is not colinear with its internalization signal. This signal is autonomous and dominant because, when transferred to an apically targeted membrane protein, the neurotrophin receptor, it redirects the chimeric construct to the basolateral domain of MDCK cells. The basolateral localization signal of the FSH receptor is thus the first signal identified for a G protein-coupled receptor and more generally for a hormone receptor.     

Long-term platinum retention after treatment with cisplatin and oxaliplatin

Background  

The aim of this study was to evaluate long-term platinum retention in patients treated with cisplatin and oxaliplatin.