Reconstitution of the Na+K+ pump of Ehrlich ascites tumor and enhancement of efficiency by quercetin

Plasma membranes from Ehrlich ascites tumor cells were solubilized by octylglucoside in the presence of phospholipids. The Na+K+-ATPase was purified from this extract by adsorption and elution from thio-Seph-arose 4B. The enzyme (specific activity, 7 mumoles of ATP hydrolyzed min-1 mg of protein -1) was reconstituted into liposomes by the octyglucoside dilution procedure. An ATP-dependent Na+ influx with low efficiency was observed. On addition of appropriate amounts of quercetin, the Na+ flux/ATP hydrolysis ratio was increased from 0.4 to 1.4.     

The phosphorylation of the primary gene products of alpha-crystallin

The alpha-crystallin primary gene product A2 and its post-translational modified counterpart A1 were isolated from calf lens cortex. The amino acid compositions determined from both chains were almost identical and in excellent agreement with that calculated from the reported sequence of A2. Chemical analysis of phosphate revealed 1 mol/mol of A1 and was negative in A2. Phosphoamino acid analysis demonstrated the presence of phosphoserine only in A1. Chymotryptic peptide maps of A2 and A1 resolved approximately 50 peptides and were strikingly similar. An apparent change in the relative mobility of one peptide was the only difference observed between A1 and A2. Phosphate analysis of this peptide obtained from A1 and A2 was positive only in the peptide from A1. Identical amino acid composition and the sequence Arg-Leu-Pro-Ser-Asn-Val-Asp-Gln-Ser-Ala-Leu was found for the peptide isolated from both chains, corresponding to residues 119 to 129 in the reported sequence of A2. These results indicate that the post-translational modification of A2 to A1 is the result of a phosphorylation reaction rather than a spontaneous nonenzymatic deamidation as previously suggested.     

Presence of a non-peptide morphine-like compound in human cerebrospinal fluid

A non-peptide morphine-like compound (MLC) is present in human ventricular and lumbar cerebro spinal fluid (CSF). None of the patients studied had received any narcotic drugs. MLC was determined by using a radioimmunoassay produced for morphine.     

Active Transport of Nicotine by the Isolated Choroid Plexus In Vitro

Abstract: In vitro , the transport of [¹⁴C]nicotine into the isolated choroid plexus, the anatomical locus of the blood–CSF barrier, was studied. The isolated rabbit choroid plexus accumulated [¹⁴C]nicotine by two processes: an active saturable transport process and a nonsaturable process. The [¹⁴C]nicotine accumulation process by choroid plexus was not due to binding or intracellular metabolism of the [¹⁴C]nicotine. The [¹⁴C]nicotine accumulation process in isolated choroid plexus was inhibited by weak bases, including tolazoline and lidocaine, but not by the weak acid probenecid. The accumulation process was decreased 60% by iodoacetate and dinitrophenol and by low temperatures. These results are consistent with previous autoradiographic evidence showing the choroid plexus concentrated [¹⁴C]nicotine in vivo , and suggest that the choroid plexus may transfer nicotine between blood and CSF in vivo .     

Genetics of NAD metabolism in Salmonella typhimurium and cloning of the nadA and pnuC loci.

The nadA and pnuC loci of S. typhimurium were cloned and found to reside within a 2.2-kilobase region. Two-dimensional O'Farrell gel electrophoresis of the proteins produced after chloramphenicol amplification and subsequent release from chloramphenicol inhibition revealed NadA and PnuC to be 43,000- and 25,000-molecular-weight proteins, respectively. The data indicated that nadA and pnuC represent two distinct genes.     

Essential roles of core starvation-stress response loci in carbon-starvation-inducible cross-resistance and hydrogen peroxide-inducible adaptive resistance to oxidative challenge in Salmonella typhimurium

The starvation-stress response (SSR) of Salmonella typhimurium encompasses the physiological changes that occur upon starvation for an essential nutrient, e.g. C-source. A subset of SSR genes, known as core SSR genes, are required for the long-term starvation survival of the bacteria. Four core SSR loci have been identified in S. typhimuriumrpoSstiAstiB, and stiC. Here we report that in S. typhimurium C-starvation induced a greater and more sustainable cross-resistance to oxidative challenge (15 mM hydrogen peroxide (H₂O₂) for 40 min) than either N- or P-starvation. Of the four core SSR loci, only rpoS and stiC mutants exhibited a defective C-starvation-inducible cross-resistance to H₂O₂ challenge. Interestingly, (unadapted) log-phase S. typhimurium rpoS and stiA mutants were very sensitive to oxidative challenge. Based on this, we determined if these core SSR loci were important for H₂O₂ resistance developed during a 60 min adaptive exposure to 60 μM H₂O₂ (adapted cells). Both unadapted and adapted rpoS and stiA mutants were hypersensitive to a H₂O₂ challenge. In addition, a stiB mutant exhibited normal adaptive resistance for the first 20 mins of H₂O₂ challenge but then rapidly lost viability, declining to a level of about 1.5% of the wild-type strain. The results of these experiments indicate that: (i) the rpoS and stiC loci are essential for the development of C-starvation-inducible cross-resistance to oxidative challenge, and (ii) the rpoSstiA, and, in a delayed effect, stiB loci are needed for H₂O₂-inducible adaptive resistance to oxidative challenge. Moreover, we found that both stiA and stiB are induced by a 60 μM H₂O₂ exposure, but only stiA was regulated (repressed) by (reduced form) OxyR.