Antimicrobial activity of aqueous extracts of Larrea divaricata Cav (jarilla) against Helicobacter pylori.

We studied here the effect of aqueous extracts of Larrea divaricata Cav on the growth of Helicobacter pylori. Results show that cold extract, infusion, decoction and simulated digestion had inhibitory activity at 0.04-0.1 mg/l against clarithromycin and metronidazole susceptible and resistant H. pylori strains. These results support the popular use of L. divaricata Cav in gastric disturbances and prompt further research to characterize these compounds with a therapeutic potential against gastric ulcers and gastric cancer associated with H. pylori.

Structural analysis of the GAP-related domain from neurofibromin and its implications.

Neurofibromin is the product of the NF1 gene, whose alteration is responsible for the pathogenesis of neurofibromatosis type 1 (NF1), one of the most frequent genetic disorders in man. It acts as a GTPase activating protein (GAP) on Ras; based on homology to p120GAP, a segment spanning 250-400 aa and termed GAP-related domain (NF1GRD; 25-40 kDa) has been shown to be responsible for GAP activity and represents the only functionally defined segment of neurofibromin. Missense mutations found in NF1 patients map to NF1GRD, underscoring its importance for pathogenesis. X-ray crystallographic analysis of a proteolytically treated catalytic fragment of NF1GRD comprising residues 1198-1530 (NF1-333) of human neurofibromin reveals NF1GRD as a helical protein that resembles the corresponding fragment derived from p120GAP (GAP-334). A central domain (NF1c) containing all residues conserved among RasGAPs is coupled to an extra domain (NF1ex), which despite very limited sequence homology is surprisingly similar to the corresponding part of GAP-334. Numerous point mutations found in NF1 patients or derived from genetic screening protocols can be analysed on the basis of the three-dimensional structural model, which also allows identification of the site where structural changes in a differentially spliced isoform are to be expected. Based on the structure of the complex between Ras and GAP-334 described earlier, a model of the NF1GRD-Ras complex is proposed which is used to discuss the strikingly different properties of the Ras-p120GAP and Ras-neurofibromin interactions.

Confirmation of the arginine-finger hypothesis for the GAP-stimulated GTP-hydrolysis reaction of Ras.

RasGAPs supply a catalytic residue, termed the arginine finger,into the active site of Ras thereby stabilizing the transition state of the GTPase reaction and increasing the reaction rate by more than one thousand-fold, in good agreement with the structure of the Ras.RasGAP complex.

Chemical and physical oral findings in a case of anorexia nervosa and bulimia.

The deleterious effect on enamel of continual acid challenge from regurgitation of gastric contents in bulimic subjects is well documented. No previous reports, however, have been published on chemical and physical measurements of teeth from such subjects, or on the importance of fluoride in maintaining their dentition. Teeth were obtained from a deceased anorexic and bulimic patient. Shortly before death this patient had saliva analyses and in vivo enamel biopsies at our clinic, before and after a 3-week regimen of daily rinsing with 0.05% NaF. After 4 years of daily regurgitation there was an almost normal thickness of the enamel surfaces typically "at risk", i.e. the palatal surfaces of the maxillary anterior teeth, with normal hardness measurements 10 micron away from the outer surface. SEM micrographs showed an irregular topography, with crystalline deposits rich in calcium, phosphate and fluoride. These surfaces were more reactive to uptake of additional fluoride when given as a daily rinse, than the more protected, and therefore, presumed unaffected surfaces. Our findings suggest that frequent and meticulous oral hygiene measures can substantially minimize the erosive effect on tooth enamel of gastric contents in bulimic patients, especially if fluoride products are used regularly.

Dentists' verbal communication leads during an interview with geriatric patients.

A reliable method has been developed to describe dentists' verbal communication leads using closed circuit television. The purpose of this investigation was to compare these leads during the greeting and initial discussion portion of an initial dental interview for ten dentists with 20 patients older than 65 years. Leads were categorized as controlling, noncontrolling, or neutral. A controlling lead was defined as a lead that allowed the dentist to exert authority in a controlling manner. The most frequently used leads in this category were closed-ended questions and structuring. Leads were categorized as noncontrolling if the lead allowed patients to express themselves (acceptance, approval, clarification, interpretation, and open-ended question). Examples of frequently observed neutral leads included small talk and information giving. The frequency of noncontrolling, neutral, and controlling leads was 28%, 40%, and 32%, respectively. Correlations between these three categories were weak and indicated that they were measuring different qualities of the communication process. When the three categories of leads were analyzed by doctors and patients' gender, the mean numbers of leads were similar, although male dentists tended to be more controlling with male patients and less controlling with female patients. These differences were not statistically significant using the analysis of variance.