Effect of three NiTi files on transportation of the apical foramen.

AIM: To compare landed and nonlanded rotary file overinstrumentation on transportation of the apical foramen in the curved canals of extracted teeth. METHODOLOGY: Severely curved molar root canals (n = 45) were distributed into three equal groups (n = 15) according to angle (mean 54°) and radius of curvature (mean 5 mm). Canals were overinstrumented 0.5 mm beyond the foramen to a size 35 master apical file using landed (ProFile ISO), nonlanded (ProFile Vortex) or nonlanded, reduced shape memory (Vortex Blue) files. Post-instrumentation images of the apical foramen were compared with pre-instrumentation control images for differences in area, circularity and ratio of Feret's diameters. Groups were compared using anova or Kruskal-Wallis tests with significance of P < 0.05. RESULTS: There were no differences between pre-treatment groups in the parameters tested. All groups demonstrated alterations in the geometry of the apical foramen. There were no significant differences between ProFile ISO, ProFile Vortex or Vortex Blue in area, circularity and ratio of Feret's diameters. CONCLUSIONS: Landed, nonlanded and nonlanded reduced shape memory files all produced transportation of the apical foramen when overinstrumented by 0.5 mm in severely curved canals. There was no difference between these file systems with regard to the degree of this effect.

Effects of ketanserin on the discrimination of electrical stimulation of the dorsal raphé nucleus in rats.

The electrical stimulation of the dorsal raphé nucleus was used as a training cue in a discrimination paradigm. Sprague-Dawley rats were trained to discriminate between electrical stimulation (ES; 200 microA) of the dorsal raphé nucleus (DRN) and non-stimulation. This was accomplished by associating ES with intraperitoneal (i.p.) injection of lithium chloride (LiCl), following the session with electrical stimulation. This made the drinking of saccharin during ES aversive by conditioned taste aversion. Following training, rats decreased saccharin consumption in ES sessions. This discrimination was learned within three pairings of the ES with LiCl. Lowering the ES current to 50-100 microA resulted in levels of saccharin consumption similar to non-stimulation levels, whereas 150 microA showed a response intermediate between the stimulation response at 200 microA and non-stimulation. The discrimination of ES of the DRN (200 microA) was not affected by prior administration of the 5-HT2 antagonist ketanserin (1 or 2 mg/kg, i.p.), suggesting that activation of 5-HT2 receptors is not the primary discriminative cue generated by ES. However, the 5-HT2A/2C agonist DOI (0.25-0.5 mg/kg, i.p.), substituted for ES of the DRN, i.e. animals reduced saccharin consumption following DOI administration. This substitution of DOI for ES was antagonized by the administration of ketanserin (1 mg/kg, i.p.). These results suggest that ES of the DRN has properties that are similar to the activation of 5-HT2A/2C receptors by DOI. However, other stimuli such as activation of other 5-HT receptors are also involved, given that the discriminative cues of ES are not blocked by the 5-HT2A/2C antagonist ketanserin.

Current trends in endodontic treatment: report of a national survey.

The authors surveyed 360 general dentists and 291 endodontists to obtain information on routine, nonemergency endodontic treatments adapted to clinical practice. Frequent practices and recent advances in treatment modalities-including instrumentation, obturation, intracanal preparations, medications and restorations-are highlighted.

Water for thought!--Private water supplies and the consumer factor.

Individual supplies from non-mains water to private dwellings were studied in a local area of East Devon. Underground spring water piped from hilltop level to holding tanks, or gathered at ground level for household wells, was tested for bacterial contamination at its point of use. Purification methods if any, and their maintenance were observed.

The application of continuous quality improvement tools in reducing the length of stay for hip replacement patients: a base hospital's experience.

The quality assurance (QA) initiative has been slow to show results. Quality assurance tools have been underdeveloped, and quality by inspection unacceptable to clinicians. A base hospital's experience with continuous quality improvement (CQI) as a means to more effective quality assurance is described. Discharge data grouped into diagnosis related groups (DRG) and analysed for inter-hospital comparison provided reliable statistical data with which to monitor the hospital's performance. The CQI tools were used to analyse the nature of the problem, and correct the deficiency. The new methodology would seem to indicate greater promise for successful quality assurance programmes in the future.

Stones in the common bile duct: experience with medical dissolution therapy.

Thirty-one patients with radiolucent common bile duct stones received medical treatment. Nineteen had Rowachol, a terpene preparation, eight (42%) achieving complete stone disappearance within 3 to 48 months. Fifteen (including 3 of the above) took Rowachol with bile acid (chenodeoxycholic in 11, ursodeoxycholic in 4) for 3 to 60 months: 11 (73%) achieved complete dissolution within 18 months. Persistent symptoms and complications settled on conservative management: 8 (25%) patients required admission (2 biliary colic, 1 obstructive jaundice, 4 cholangitis, 1 pancreatitis). One patient died of a myocardial infarction during recovery from pancreatitis; the other continued treatment, 2 achieving complete dissolution/disappearance. Oral dissolution therapy with Rowachol and bile acids should be considered when endoscopic sphincterotomy or surgery is not feasible, but careful attention to potential complications is required while stones persist.

Pilot study of combination treatment for gall stones with medium dose chenodeoxycholic acid and a terpene preparation.

Thirty patients with radiolucent stones in a radiologically functioning gall bladder were treated for up to two years with a combination of Rowachol (one capsule twice daily), a mixture of cyclic monoterpenes, and chenodeoxycholic acid (7.0-10.5 mg/kg/day). The patients were not selected for body weight or size of stones. All complete dissolutions diagnosed by oral cholecystography were confirmed or refuted by ultrasound examination. Control of symptoms was excellent, only one patient withdrawing from the study because of persistent biliary pain. No evidence of hepatotoxicity was detected biochemically, and diarrhoea due to chenodeoxycholic acid was minimal at this dose. Stones disappeared completely in 11 patients (37%) within one year and in 15 (50%) within two years. These results compared favourably with those obtained with similar doses of chenodeoxycholic acid alone, in particular those of the National Co-operative Gallstone Study (complete dissolution in 13.5% of patients at two years). Treatment with a combination of medium dose chenodeoxycholic acid with Rowachol for radiolucent gall stones is economical, effective, and likely to minimise persistent symptoms and adverse effects of treatment.

Synthesis of hypoxanthine, guanine, and 6-thiopurine nucleosides of 6-deoxy-D-allofuranose.

Hypoxanthine, guanine, and 6-thiopurine nucleosides of 6-deoxy-D-allofuranose have been prepared as potential antitumor agents. Thus, reaction of 6-deoxy-beta-D-allofuranosyl bromide (1) with the trimethylsilyl derivatives of hypoxanthine and guanine afforded mixtures of the 9- and the 7-substituted bases, which were separated and deblocked with ammonia to give 9-(6'-deoxy-beta-D-allofuranosyl)hypoxanthine (6), 7-(6'-deoxy-beta-D-allofuranosyl)hypoxanthine (7), 9-(6'-deoxy-beta-D-allofuranosyl)guanine (8), and 7-(6'-deoxy-beta-D-allofuranosyl)guanine (9). The two nucleosides with the purine joined at the N-9 position, namely, 6 and 8, are easily distinguished from the other two nucleosides (7 and 9), having N-7 junctions, by their NMR spectra. Reaction of 1 with the trimethylsilyl derivative of 6-chloropurine afforded 10, which upon treatment with thiourea and deblocking gave 9-(6'-deoxy-beta-D-allofuranosyl)-6-thiopurine (12). The hypoxanthine and guanine nucleosides showed no inhibition of mouse leukemia L1210 when tested in vivo, but the thiopurine nucleoside 12 showed strong inhibition of growth of L1210 both in vivo and in vitro. Compound 7 strongly inhibited purine nucleoside phosphorylase (KI = 8.8 X 10(-5) M), while compounds 8, 9, 6, and 12 were inactive.

An n locus multiallele model for gene substitution.

We discuss the conceptual conflict between a slow series of gene substitutions as the mechanism of evolutionary change, and the apparent need for rapid and coordinated changes at many loci simultaneously in producing complex adaptations. To improve on the limitations of classical theory and accommodate the enormous amount of variability disclosed by electrophoretic studies, we develop a model that can deal with gene substitution at n loci, with numerous alleles at each locus. Fitness is treated somewhat differently from the usual way by allowing it to vary between zero and the number of offspring an individual of a particular species can produce. As maximum fitnesses, we chose five as typical of large mammals, 100 for insects like Drosophila, and 1000 for very prolific species. When our model is applied to the classical problem of determining the number of generations required to change the gene frequency from 0.0001 to 0.9999 (but for 100 loci rather than one), we find that it requires 22,899 generations when maximum fitness is five, 7,984 generations when maximum fitness is 100 and 5,333 generations when it is 1000. This is something of an improvement over the 300,000 generations calculated by Haldane (1957). By allowing the fitnesses in our model to be explicitly frequency dependent, these results are reduced considerably. In addition, allowing varying proportions of the population to inbreed reduces the number of generations required for the classical problem by as much as 50%. We also point out that, given the large amount of observed genetic variation, evolutionary change may not be so much a matter of classical gene substitution as it is of changing from one array of alleles to another. With our model, the array (0.5, 0.15, 0.2, 0.1, 0.05) can be changed to (0.03, 0.1, 0.2, 0.17, 0.5) at 1000 loci in 6,043, 2,108, or 1,408 generations, depending on whether the maximum fitness is five, 100, or 1000. Finally, we note that it is possible to substitute one array for another while continuously favoring heterozygotes.

Lead content of human hair (1871-1971).

Samples of antique and contemporary human hair were analyzed for lead by atomic absorption spectroscopy. Antique hair contained a significantly greater amount of lead than did contemporary hair.