Pertussis toxin modification of PC12 cells inhibits a protein phosphatase 2A-like phosphatase.

We have found that modification of rat PC12 cells with pertussis toxin resulted in an approximately 50% inhibition of a protein phosphatase 2A-like phosphatase. Protein phosphatase 2A (PP2A) is a major cellular serine/threonine-specific protein phosphatase. Treatment of extracts from pertussis toxin-modified PC12 cells with either immobilized alkaline phosphatase or Ca2+ reversed this inhibition.

Two-component kinase-like activity of nm23 correlates with its motility-suppressing activity.

Nm23 genes, which encode nucleoside diphosphate kinases, have been implicated in suppressing tumor metastasis. The motility of human breast carcinoma cells can be suppressed by transfection with wild-type nm23-H1, but not by transfections with two nm23-H1 mutants, nm23-H1(S12OG) and nm23-H1(P96S). Here we report that nm23-H1 can transfer a phosphate from its catalytic histidine to aspartate or glutamate residues on 43-kDa membrane proteins.

Comparative activities of new fluoroquinolones, alone or in combination with amoxicillin, trimethoprim-sulfamethoxazole, or rifampin, against intracellular Listeria monocytogenes.

We studied the activities of the new fluoroquinolones clinafloxacin, levofloxacin, ofloxacin, and sparfloxacin alone or in combination on the intracellular growth of Listeria monocytogenes. Against intracellular growth of the four strains tested, a similar reduction of the bacterial count was obtained with clinafloxacin at the dose of 10 x MIC (delta log10 CFU/ml = -2.19 +/- 0.

Developing and evaluating the student assessment system in the preclinical problem-based curriculum at Sherbrooke.

Background: Students' learning was used as an outcome measure in the first phases of the major curriculum reform started in 1987 by the Université de Sherbrooke Faculty of Medicine, which shifted from a traditional to a student-centered, problem-based learning (PBL) and community-oriented program. The system for evaluating preclinical students' learning is intended to reinforce the integration of basic and clinical sciences.

Method: To discover whether the evaluation system was fulfilling its intended goals, the authors used data from the classes of 1991-1993 to assess the reliability and validity of three evaluation instruments.

Phosphorylation of ATP-citrate lyase by nucleoside diphosphate kinase.

Rat liver nucleoside diphosphate kinase (NDPK) and PC12 cell cytosol were used to determine whether NDPK could function as a protein kinase. NDPK was phosphorylated on its catalytic histidine using [gamma-32P]ATP, and the phosphorylated NDPK separated from [gamma-32P]ATP. The addition of phosphorylated NDPK to dialyzed PC12 cell cytosol resulted in the phosphorylation of a protein with a subunit molecular mass of about 120 kDa.

An in-vitro evaluation of silicone elastomer latex for topical drug delivery.

A silicone elastomer latex was evaluated as a topical drug-delivery system. With the addition of a fumed silica and the removal of water, the latex produced elastomeric solid films. The water vapour permeability of the solid film was found to be a function of the film composition.

Comparing checklists and databases with physicians' ratings as measures of students' history and physical-examination skills.

Purpose: To compare two methods of rating students' performances on history and physical examination: (1) by using checklists completed by standardized patients (SPs) and databases completed by students, and (2) by using ratings of students by three physicians for each SP-student encounter.

Method: Four cases were chosen for the study, and 30 students were examined per case. The students were all in their fourth year at the Southern Illinois University School of Medicine in the spring of 1991.

Immigrant and refugee children in Canada.

In view of Canada's commitment to immigration, understanding the sources of successful adaptation by immigrant and refugee children is vital. This paper reviews the literature on the mental health of migrant children and suggests an agenda for future research.

Stimulation of secretion in permeabilized PC12 cells by adenosine 5'-[gamma-thio]triphosphate: possible involvement of nucleoside diphosphate kinase.

The addition of Ca2+, adenosine 5'-[gamma-thio]triphosphate (ATP[S]) or guanosine 5'-[gamma-thio]triphosphate (GTP[S]) to digitonin-permeabilized PC12 cells stimulates noradrenaline secretion. Both ATP[S] and GTP[S] stimulate release in the absence of Ca2+. Whereas ADP and adenosine 5'-[beta gamma-imido]triphosphate inhibited ATP[S]-stimulated release, they did not inhibit Ca(2+)-stimulated release even in the absence of added ATP.

ATP-induced secretion in PC12 cells and photoaffinity labeling of receptors.

Secretion of catecholamines by rat PC12 cells is strongly stimulated by extracellular ATP via a P2-type purinergic receptor. ATP-induced norepinephrine release was inhibited 80% when extracellular Ca2+ was absent. Only four nucleotides, ATP, ATP gamma S, benzoylbenzoyl ATP (BzATP), and 2-methylthio-ATP, gave substantial stimulation of norepinephrine release from PC12 cells.

Clinical performance-based test sensitivity and specificity in predicting first-year residency performance.

To assess the use of a standardized-patient-based postclerkship examination (PCX) to predict students' performances in their first year of residency, the authors used data from 202 students of the classes of 1987, 1988, and 1990 at the Southern Illinois University School of Medicine. The PCX was found to be more sensitive than specific in that it identified more correctly those students who received high ratings in their first year of residency than those who received low ratings. Consequently, while the rate of false negatives was low across the three classes, the rate of false positives was relatively high.

Effects of examinee gender, standardized-patient gender, and their interaction on standardized patients' ratings of examinees' interpersonal and communication skills.

Purpose: To assess the effects of examinee gender, standardized-patient (SP) gender, and, in particular, their interaction on ratings made by SPs of examinees' interpersonal and communication skills in a performance-based examination of clinical competence.

Method: The examination was administered to four classes of senior medical students (about 70 per class) at Southern Illinois University School of Medicine, 1988-1991. The skill dimensions tested were clarity of communication, thoroughness of explanation, professional manner, personal manner, and overall patient satisfaction.

Small membrane-associated GTP-binding proteins of catecholamine-secreting cells.

1. Four GTP-binding proteins (23-27 kDa) were identified in membranes from PC12 cells by [alpha 32P]GTP binding to nitrocellulose blots of SDS-polyacrylamide gels. 2.

Screening test length for sequential testing with a standardized-patient examination: a receiver operating characteristic (ROC) analysis.

The feasibility of using sequential testing (i.e., using a screening test) to reduce the length and expense of a performance-based examination with standardized-patient cases was demonstrated previously.

Anti-(14-3-3 protein) antibody inhibits stimulation of noradrenaline (norepinephrine) secretion by chromaffin-cell cytosolic proteins.

Incubation of digitonin-permeabilized bovine chromaffin cells in the absence of Ca2+ results in a loss of both cytosolic proteins and Ca(2+)-dependent secretion. Addition of these leaked proteins prevents this loss of secretory activity. We have purified a protein from an extract of bovine adrenal medulla which can partially prevent this loss of Ca(2+)-dependent secretion.

Iontophoretic permeation of sodium cromoglycate through synthetic membrane and excised hairless mouse skin.

The iontophoretic transport properties of sodium cromoglycate were characterized using a synthetic membrane and excised hairless mouse skin. The permeation rate of sodium cromoglycate through the synthetic membrane was found to be linearly dependent on the density of electrical current applied. Passive diffusion through the excised hairless mouse skin was not demonstrated for sodium cromoglycate; however, under iontophoresis, an appreciable permeation was exhibited by the drug through the animal skin, which was also found to be a function of the electrical current density.