Muscarinic M3 receptors are coupled to two signal transduction pathways in rat submandibular cells

The receptor subtypes involved in muscarinic-induced phosphoinositide hydrolysis and adenylate cyclase inhibition in rat submandibular acinar cells were characterized by comparing the inhibitory potencies of four muscarinic antagonists on the two signal transduction responses. Carbachol-induced phosphatidylinositol 4,5-bisphosphate (PIP2) hydrolysis was inhibited by all antagonists with a potency rank order of 4-diphenylacetoxy-N-methyl piperidine methobromide (4-DAMP) = atropine much greater than pirenzepine much greater than AF-DX 116 (P less than 0.01). The same rank order was observed in antagonist-reversal of the reduction of cAMP caused by carbachol in the model. These findings suggest that muscarinic effects are mediated by M3 receptors in both the phosphoinositide and adenylate cyclase pathways in the submandibular gland.     

Human liver microsomal N-hydroxylation of dapsone by cytochrome P-4503A4.

One of the major routes of elimination of dapsone (4,4'-diaminodiphenylsulfone) is by N-oxidation, to produce a hydroxylamine metabolite. The specific form of cytochrome P-450 (P-450) involved in this oxidation reaction was examined in human liver microsomal preparations previously characterized with respect to their content of several known P-450 enzymes. Among five preparations, the rank order of activity for dapsone hydroxylamine formation was most well correlated with the immunochemically determined level of P-4503A4 (r = 0.94, p less than 0.03). Moreover, inhibition of microsomal oxidation was observed with antibodies specific to P-4503A, with a maximum reduction of greater than 90%, but was not produced by antibodies specific to P-4501A2, P-4502CMP, or P-4502E1. Prior incubation of microsomes with gestodene (100 microM) or troleandomycin (20 microM), known selective mechanism-based inhibitors of P-4503A enzymes (in the presence of NADPH), led to 75% and 40% reductions in catalytic activity, respectively. In contrast, preincubation with increasing concentrations of alpha-naphthoflavone, a known activator of P-4503A4, increased dapsone N-hydroxylation in a concentration-dependent manner, with 5-fold activation being observed at 50 microM alpha-naphthoflavone. Finally, P-4503A4 isolated from human liver microsomes and cDNA-expressed P-4503A4 (in yeast) were both able to catalyze dapsone N-hydroxylation, with the latter preparation exhibiting a 3-fold activation in the presence of 100 microM alpha-naphthoflavone. Collectively, these findings demonstrate that N-oxidation of dapsone in human liver is predominantly mediated by P-4503A4, and they suggest that quantitative measurement of this metabolic pathway in vivo might serve as an index of the activity of this enzyme.     

Prospective trial of supranormal values as goals of resuscitation in severe trauma.

We prospectively tested the effect of the early postinjury attainment of supranormal values of cardiac index (> or = 4.52 L/min per square meter), oxygen delivery (> or = 670 mL/min per square meter), and oxygen consumption (> or = 166 mL/min per square meter) on outcome in traumatized patients with an estimated blood loss of 2000 mL or more. The goals in control patients were to attain normal values for all hemodynamic measurements. During the 6-month period, 33 protocol patients and 34 control patients with similar vital signs, estimated blood losses, and severity of injuries were enrolled in the study. Eight (24%) protocol patients died, while 15 (44%) control patients died. The protocol patients had fewer mean (+/- SEM) organ failures per patient (0.76 +/- 1.21 vs 1.59 +/- 1.60), shorter stays in the intensive care unit (5 +/- 3 vs 12 +/- 12), and fewer mean days requiring ventilation (4 +/- 3 vs 11 +/- 10) than did the control patients (P < .05 for each). We conclude that attaining supranormal circulatory values improves survival and decreases morbidity in the severely traumatized patient.     

F-19 MR imaging of glucose metabolism in the rabbit

Noninvasive metabolic magnetic resonance (MR) imaging reflecting glucose metabolism in the aldose-reductase-sorbitol (ARS) pathway was performed in the rabbit head; after administration of the fluorinated glucose analogue 3-fluoro-3-deoxy-D-glucose (3FD-glucose), fluorine-19 images were generated. Images of 3FD-glucose showed significant 3FD-glucose uptake by adipose tissue, indicating its buffering effects in case of excess loads of glucose. Images of 3-fluoro-3-deoxy-D-sorbitol (3FD-sorbitol) demonstrated the spatial distribution of aldose reductase activities and significant sorbitol accumulation in the lens. Images of 3-fluoro-3-deoxy-D-fructose (3FD-fructose) showed preferential uptake of fructose by muscle tissue. The extremely low toxicity of 3FD-glucose indicates promise for its clinical application in metabolic imaging.     

Development and testing of a decision tree for blunt trauma

The aim of the present study was to examine the essential problems in a retrospective study of 381 organ injuries in 260 patients, to identify problems, to define criteria, to describe decision rules, and to organize these rules into branch-chain decision trees or clinical algorithms. The basic hypothesis of this study is that criteria organized into a prioritized decision tree can provide objective standards to evaluate the quality of trauma care and to compare alternative approaches. The algorithm was designed to provide prompt therapy for the most life-threatening problems: respiratory and cardiac arrest, shock, head injury, tamponade, lacerations of the great vessels, cardiac contusion, ruptured parenchymal organs, lacerated viscera, and injury to other intraperitoneal organs. Resuscitation from shock, correction of circulatory problems, and monitoring of physiologic variables were prioritized to evaluate the presence of circulatory deficits and the adequacy of specific therapy to correct them. Concomitantly, diagnosis of the underlying problems was approached using peritoneal lavage, abdominal and chest x-rays, iv urograms, cystograms, endoscopy, upper and lower GI barium or hypaque studies, ultrasound, scintograms, and CT scans. In emergency conditions these are limited to a large extent by time factors. The diagnostic accuracy, priorities, and limitations of each of these were evaluated in emergency conditions. The algorithm was used to track management decisions in a prospective series; the mortality of 51 patients with satisfactory compliance was 4% and 44% in nine patients with major deviations from the algorithm.     

Evaluation of the occult blood test in screening for colorectal neoplasms. A prospective study using flexible endoscopy

Survival rates from colorectal cancer will rise only when polyps and cancers are found at an earlier, curable stage. Consequently, the purpose of the present study was to compare the yield of colonic neoplasms from flexible sigmoidoscopy and colonoscopy with that from occult blood testing. Results from 474 flexible sigmoidoscopies and 1,115 colonoscopies were prospectively recorded during a four-year study period. Colorectal polyps were found in 111 (23.4%) patients undergoing flexible sigmoidoscopy and 325 (29.1%) patients undergoing colonoscopy. Among the 436 patients with polyps, the occult blood test was negative in 282 (64.7%). Among the 51 patients with colorectal cancers, the occult blood test was negative in 20 (39.1%). Thus, testing for occult blood missed the majority of polyps and a large percentage of the carcinomas. These data indicate that lower gastrointestinal endoscopy is superior to occult blood testing as a screening test for detecting colorectal polyps or cancers. Furthermore, given the high incidence of neoplasia in this patient population, the authors suggest that colonoscopy become the screening test of choice for colorectal cancer.