Nucleolar specific acidic phosphoprotein C23 is highly methylated

Protein C23 (Mr = 110,000; pI, 5.5) is the major phosphoprotein in the nucleolus of Novikoff hepatoma cells and comprises 9.5% of the total nucleolar protein. In addition to being highly phosphorylated (1.2 mol % of phosphoserine), it is also highly methylated. Protein C23 contains 1.3 mol % of NG,NG-dimethylarginine and a trace of NG-monomethylarginine.     

Three-dimensional structure of AmpC beta-lactamase from Escherichia coli bound to a transition-state analogue: possible implications for the oxyanion hypothesis and for inhibitor design

The structures of AmpC beta-lactamase from Escherichia coli, alone and in complex with a transition-state analogue, have been determined by X-ray crystallography. The native enzyme was determined to 2.0 A resolution, and the structure with the transition-state analogue m-aminophenylboronic acid was determined to 2.3 A resolution. The structure of AmpC from E. coli resembles those previously determined for the class C enzymes from Enterobacter cloacae and Citrobacter freundii. The transition-state analogue, m-aminophenylboronic acid, makes several interactions with AmpC that were unexpected. Perhaps most surprisingly, the putative "oxyanion" of the boronic acid forms what appears to be a hydrogen bond with the backbone carbonyl oxygen of Ala318, suggesting that this atom is protonated. Although this interaction has not previously been discussed, a carbonyl oxygen contact with the putative oxyanion or ligand carbonyl oxygen appears in most complexes involving a beta-lactam recognizing enzyme. These observations may suggest that the high-energy intermediate for amide hydrolysis by beta-lactamases and related enzymes involves a hydroxyl and not an oxyanion, although the oxyanion form certainly cannot be discounted. The involvement of the main-chain carbonyl in ligand and transition-state recognition is a distinguishing feature between serine beta-lactamases and serine proteases, to which they are often compared. AmpC may use the interaction between the carbonyl of Ala318 and the carbonyl of the acylated enzyme to destabilize the ground-state intermediate, this destabilization energy might be relieved in the transition state by a hydroxyl hydrogen bond. The structure of the m-aminophenylboronic acid adduct also suggests several ways to improve the affinity of this class of inhibitor and points to the existence of several unusual binding-site-like features in the region of the AmpC catalytic site.     

Regulation of class I-restricted epitope processing by local or distal flanking sequence

Influenza A/Puerto Rico/8/34 nucleoprotein (NP) contains an H-2Kd-restricted CD8+ T cell (T CD8+) epitope spanning amino acid residues 147-155. It was previously demonstrated that expression of NP147-155 and NP147-158 in isolation via "minigene"/recombinant vaccinia virus (vac) technology leads to sensitization of target cells for NP-specific killing while expression of 147-158 lacking the arginine at position 156 (termed here as 147-155TG) does not. The presentation block was overcome by placing this fragment into the context of full length NP. We show that addition of a single amino acid, Met159, to the C terminus of the blocked peptide (creating 147-155TGM) restores presentation. Presentation of 147-155TGM was not due to trimming in the exocytic compartment, consistent with severe limitations on C-terminal trimming activity in this location. Rescued presentation was also achieved when the blocked construct was extended in the N-terminal direction only, but in this case more than 55 amino acids of flanking sequence were required. The transition to presentation was abrupt, with 91-155TG and shorter constructs showing little or no detectable presentation and 90-155TG showing full level presentation. Presentation could not be attributed to acquisition of conventional targets for ubiquitination since mutation of all Lys residues, to which the ubiquitin moiety is conjugated, does not abrogate presentation. Rescued presentation was not inhibited by the peptide aldehyde N-acetyl-L-leucinyl-L-leucinal-L-norleucinal, suggesting that the added elements may be recruiting nonproteasomal activity. We have therefore identified and begun to characterize protease targeting of regulatory elements, both local and distal to an epitope, which strongly influence the ability of the epitope to be excised.     

A comparison of sustained-release bupropion and placebo for smoking cessation

BACKGROUND AND METHODS: Trials of antidepressant medications for smoking cessation have had mixed results. We conducted a double-blind, placebo-controlled trial of a sustained-release form of bupropion for smoking cessation. We excluded smokers with current depression, but not those with a history of major depression. The 615 subjects were randomly assigned to receive placebo or bupropion at a dose of 100, 150, or 300 mg per day for seven weeks. The target quitting date (or "target quit date") was one week after the beginning of treatment. Brief counseling was provided at base line, weekly during treatment, and at 8, 12, 26, and 52 weeks. Self-reported abstinence was confirmed by a carbon monoxide concentration in expired air of 10 ppm or less. RESULTS: At the end of seven weeks of treatment, the rates of smoking cessation as confirmed by carbon monoxide measurements were 19.0 percent in the placebo group, 28.8 percent in the 100-mg group, 38.6 percent in the 150-mg group, and 44.2 percent in the 300-mg group (P<0.001). At one year the respective rates were 12.4 percent, 19.6 percent, 22.9 percent, and 23.1 percent. The rates for the 150-mg group (P=0.02) and the 300-mg group (P=0.01) -- but not the 100-mg group (P=0.09) -- were significantly better than those for the placebo group. Among the subjects who were continuously abstinent through the end of treatment, the mean absolute weight gain was inversely associated with the dose (a gain of 2.9 kg in the placebo group, 2.3 kg in 100-mg and 150-mg groups, and 1.5 kg in the 300-mg group; P= 0.02). No effects of treatment were observed on depression scores as measured serially by the Beck Depression Inventory. Thirty-seven subjects stopped treatment prematurely because of adverse events; the frequency was similar among all groups. CONCLUSIONS: A sustained-release form of bupropion was effective for smoking cessation and was accompanied by reduced weight gain and minimal side effects. Many participants in all groups were smoking at one year.     

Bilateral cerebral mycotic aneurysm in a child. Report of a case and review of the literature]

Bronchial provocation tests by "occupational" exposure to flour provoked dual asthmatic reactions accompanied by rhinitis in two atopic bakers engaged in the manufacture of bread and pies. Ingestion tests with uncooked flour produced no reactions. Skin prick tests with aqueous extracts of flour produced positive immediate reactions in both bakers, and negative reactions in nine of ten atopic asthmatic control subjects with no occupational exposure to flour. Intracutaneous tests, performed in one precipitin negative baker, gave dual responses. Precipitating antibodies to an aqueous extract of flour were found in the unconcentrated serum of the other baker, and not in ten control subjects.     

Using a newsletter to deliver the message of cost containment

Nurse educators often ask themselves how they can affect the bottom line of their organization. At the University of Minnesota Hospital and Clinic, Education Services is using a newsletter to promote cost-effective practice. "Dollars and Sense" has proven to be an effective and efficient educational methodology. A small investment of time and resources can reap substantial savings at the bedside. This article discusses how to develop a similar newsletter.     

Nephrotoxicity of notexin in experimental mice

Notexin, a well known neurotoxin, derived from tiger snake venom, was shown to have direct nephrotoxic properties in experimental mice. A single subcutaneous dose of 1.38 micrograms/kg body weight of notexin produced renal tubular and glomerular damage within 24 hours. Renal damage increased in severity proportional to the dose of notexin injected. At a high dose of notexin, thrombotic "spherules" were found in glomeruli. These thrombotic spherules have not been previously reported to be associated with notexin or snake venoms.