Effect of radiation and contrast media on chromosomes. Preliminary report

Measurements of chromosome aberrations or micronuclei in lymphocytes obtained from 7 patients indicate that angiocardiography produced chromosome damage corresponding to an average absorbed dose of about 50 rads. This is an order of magnitude larger than was estimated from the exposure rate. Experiments on lymphocytes suspended in solutions of methylglucamine and sodium diatrizoate (Renografin) or sodium diatrizoate alone (Hypaque) indicate that the chromosome damage observed in the patients is due in larger part to two effects: (a) an increased absorption of x rays as compared to blood and (b) a breakage of chromosomes even in the absence of x rays.     

Acidosis, alkalosis, and aqueous humor dynamics in rabbits

Systemic acidosis induced by intravenous administration of hydrochloric acid lowered intraocular pressure in unanesthetized rabbits. Aqueous humor flow was reduced by approximately 50%, as measured by the iodide method and as calculated from tonographic data. Outflow facility, episcleral venous pressure, plasma osmolality, blood pressure, pulse, and body temperature were not altered by systemic acidosis. Systemic alkalosis induced by intravenously administered sodium bicarbonate was associated with an increased intraocular pressure. Aqueous humor flow following systemic alkalosis was increased by approximately 100%, as measured by the iodide method and as calculated from tonographic data. Alkalosis was not associated with alterations in outflow facility, episcleral venous pressure, plasma osmality, blood pressure, pulse, or rectal temperature.     

Multiple choice questions for continuing education in family medicine

Multiple choice questions used in continuing medical education may require characteristics different from those used in tests and examinations. The questions of three continuing education exercise were assessed by 48 board certified family physicians. Each physician answered one third of the questions and then judged them on usefulness in patient management, as discriminators of quality of medical care, and on educational value. The relevance of each question was determined by a composite index based on these factors. The content of each question was independently analyzed by three physicians. Relevant questions tended to be those concerned with surgery, symptoms, and management, and those requiring more than simple factual recall. Questions on office management or concerning specific diagnoses were considered less relevant. Neither the manner of asking the question nor the severity of the illness appeared to influence relevance. This information should benefit those developing continuing education programs for family physicians, especially those designed for self-administered individual learning.     

Cyclin E2, a novel G1 cyclin that binds Cdk2 and is aberrantly expressed in human cancers

A novel cyclin gene was discovered by searching an expressed sequence tag database with a cyclin box profile. The human cyclin E2 gene encodes a 404-amino-acid protein that is most closely related to cyclin E. Cyclin E2 associates with Cdk2 in a functional kinase complex that is inhibited by both p27(Kip1) and p21(Cip1). The catalytic activity associated with cyclin E2 complexes is cell cycle regulated and peaks at the G1/S transition. Overexpression of cyclin E2 in mammalian cells accelerates G1, demonstrating that cyclin E2 may be rate limiting for G1 progression. Unlike cyclin E1, which is expressed in most proliferating normal and tumor cells, cyclin E2 levels were low to undetectable in nontransformed cells and increased significantly in tumor-derived cells. The discovery of a novel second cyclin E family member suggests that multiple unique cyclin E-CDK complexes regulate cell cycle progression.     

Predicting unit performance by assessing transformational and transactional leadership.

How do leadership ratings collected from units operating under stable conditions predict subsequent performance of those units operating under high stress and uncertainty? To examine this question, the authors calculated the predictive relationships for the transformational and transactional leadership of 72 light infantry rifle platoon leaders for ratings of unit potency, cohesion, and performance for U.S. Army platoons participating in combat simulation exercises. Both transformational and transactional contingent reward leadership ratings of platoon leaders and sergeants positively predicted unit performance. The relationship of platoon leadership to performance was partially mediated through the unit's level of potency and cohesion. Implications, limitations, and future directions for leadership research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The constitution and phase stability of overlapping melt trails in Ag- Cu alloys produced by continuous laser melt quenching

Coatings consisting of overlapping trails melted with a scanning CW CO₂ laser have been produced on Ag-Cu alloys with the following compositions: Cu 17 at. pct Ag; Cu 37 at. pct Ag; Cu 61.7 at. pct Ag; Cu 71.8 at. pct Ag; and Cu 82 at. pct Ag. The laser beam was scanned at a velocity of 34 cm s¹ and with an intensity of 3.6 MW cm^-2. Selected trails were examined by X-ray diffractometry, optical microscopy, and scanning electron microscopy in the as-irradiated condition and after annealing for various periods of time in the temperature range 100 to 450 ° C. Time-temperature-transformation diagrams based on the annealing studies are presented. Significant amounts of the metastable extended solid solution (γ) were observed in the Ag-rich alloy trails. The silver rich terminal solid solution (α) was also detected, formed probably by solid state precipitation. An α’ phase with lattice parameter lying between that ofy and α was also observed in the Cu 61.7 at. pct Ag alloy. A metastable equilibrium diagram has been constructed and is employed to interpret these observations. The most striking microstructural feature of the trails are bands marking sequential positions of the melt-solid interface. We propose that these bands are evidence for planar, oscillating - steady-state, interface motion. The observation of a periodic cellular breakdown of the planar interface in the Cu 61.7 at. pct Ag alloy is attributed to a diffusional instability previously predicted by Baker and Cahn.     

Laxative-like effects of nonsteroidal anti-inflammatory drugs on intestinal fluid movement and membrane integrity

Certain nonsteroidal anti-inflammatory drugs (NSAID) of the fenamate chemical class are known to cause diarrhea in clinical use. Paradoxically, this action is shared by prostaglandins, against whose syntheses are inhibited by NSAID. This study was done to investigate the laxative potential of 5 NSAID (meclofenamate, flufenamate, mefenamate, indomethacin and aspirin). The ability to produce a laxative response was assessed by determining effects on fluid absorption in vitro in hamster everted sacs and by the enteropooling assay in hamster small intestine. In addition, the lytic action of these drugs on the erythrocyte membrane was determined to arrive at a possible mechanism of action. All of the NSAID, except aspirin, produced dose-related inhibition of fluid transport, similar to prostaglandin E1 and E2. The order of inhibition was flufenamate greater than meclofenamate greater than mefenamate greater than indomethacin. Like results were obtained when enteropooling was measured in vivo. Flufenamate and meclofenamate produced lumenal fluid accumulation comparable to two laxatives, dioctyl sodium sulfosuccinate and ricinoleic acid. Finally, the effects of these NSAID on fluid movement paralleled their lytic action on the erythrocyte membrane model, suggesting that NSAID may produce diarrhea in a manner similar to certain laxatives, by increasing mucosal permeability through membrane damage.     

Electrophysiological and pharmacological responses of chronically denervated lower esophageal sphincter of the opossum

BACKGROUND & AIMS: Achalasia is characterized by loss of myenteric neurons and incomplete relaxation of the lower esophageal sphincter (LES). The aim of this study was to develop an achalasia model in the opossum using the surfactant benzyldimethyltetradecylammonium chloride (BAC). This study further characterizes the achalasia model. METHODS: BAC or saline was injected circumferentially into the LES of 14 adult opossums. Eight months after injection, manometry, isolated muscle bath studies, electrical field stimulation, and histochemical analysis were performed. RESULTS: Manometrically, the LES of BAC-treated opossums showed higher pressures (38.7 +/- 12 mm Hg vs. 17 +/- 3.0 mm Hg) and reduced esophageal body contraction amplitudes (4.2 +/- 3 mm Hg vs. 27.4 +/- 12 mm Hg). Isolated muscle strips challenged with carbachol and sodium nitroprusside contracted and relaxed similarly to controls. Electrical field stimulation failed to induce relaxation in BAC-treated tissue but did induce contraction. Contractile responses were markedly reduced by tetrodotoxin and atropine in BAC-treated animals and controls. An altered nitric oxide system was shown by the lack of response to L-arginine and N omega-nitro-L-arginine. Histology showed loss of myenteric neurons and increased cholinergic nerve bundles. CONCLUSIONS: Loss of NO inhibitory myenteric neurons markedly reduces the relaxation of the LES, and histology and pharmacological responses suggest a proliferation of cholinergic nerves into the LES contributing to the static elevated pressures of the amyenteric LES.