Low frequency sound propagation in activated carbon.

Activated carbon can adsorb and desorb gas molecules onto and off its surface. Research has examined whether this sorption affects low frequency sound waves, with pressures typical of audible sound, interacting with granular activated carbon. Impedance tube measurements were undertaken examining the resonant frequencies of Helmholtz resonators with different backing materials. It was found that the addition of activated carbon increased the compliance of the backing volume. The effect was observed up to the highest frequency measured (500 Hz), but was most significant at lower frequencies (at higher frequencies another phenomenon can explain the behavior). An apparatus was constructed to measure the effective porosity of the activated carbon as well as the number of moles adsorbed at sound pressures between 104 and 118 dB and low frequencies between 20 and 55 Hz. Whilst the results were consistent with adsorption affecting sound propagation, other phenomena cannot be ruled out. Measurements of sorption isotherms showed that additional energy losses can be caused by water vapor condensing onto and then evaporating from the surface of the material. However, the excess absorption measured for low frequency sound waves is primarily caused by decreases in surface reactance rather than changes in surface resistance.

In vitro metabolism of the specific endothelin-A receptor antagonist ZD4054 and clinical drug interactions between ZD4054 and rifampicin or itraconazole in healthy male volunteers.

ZD4054 is an oral specific endothelin-A receptor antagonist in development for the treatment of hormone-resistant prostate cancer. Both renal and metabolic processes contribute to its overall clearance. Two preclinical in vitro studies investigated the metabolism of ZD4054 using human liver microsomes, individual cytochrome P450 (CYP) isozymes, and flavin-containing monooxygenase isoforms. Two Phase I open-label crossover volunteer studies subsequently investigated in vivo drug interactions between ZD4054 and the CYP450 inducer rifampicin or CYP3A4 inhibitor itraconazole. The most abundant metabolite produced in in vitro incubations accounted for 12.8% of radioactivity after ZD4054 was incubated with CYP3A4. No significant flavin-containing monooxygenase metabolism of ZD4054 was observed. In the in vivo studies, rifampicin co-administration reduced the area under the concentration-time curve and maximum plasma concentration of ZD4054 by 68% and 29%, respectively, whilst co-administration with itraconazole was associated with an increase in ZD4054 area under the curve of approximately 28%. While co-administration of CYP450 inducers might be associated with reduced efficacy of ZD4054, dose reduction is unlikely to be required with concomitant administration of CYP3A4 inhibitors.

A gene encoding gamma-adaptin is required for apical extension growth in Ustilago maydis.

The nucleotide (nt) sequence of an Ustilago maydis (Um) gene that complemented a partially osmotic-remedial temperature-sensitive (or-ts) mutant defective in apical extension growth has been determined. It contained a continuous open reading frame (OFR) predicted to encode a protein of 853 amino acids (aa). The deduced aa sequence was homologous to gamma-adaptin, a component of clathrin-coated vesicles derived from the Golgi.

Discussion: diet and nutrition in dental health and disease.

The recognition in 1993 by the International Association of Dental Research (IADR) for the initiation of a Nutrition Research Group within the Association prompted this nutrition symposium related to diet and nutrition in health and disease. The IADR Nutrition Research Group is encouraged to collaborate with other nutritional research groups in important areas of medicine, food science technology, and agriculture to target health issues influenced by dietary choices, nutritional adequacy, and dental health status.

Dental caries at five and twelve years in a South African Indian community: a longitudinal study.

In 1979, 515 of 767 available Indian children born in Lenasia in 1974 were examined and their dental caries status was described. In 1986, 515 of the original 715 were re-examined in order to determine the pattern of dental caries in the primary and permanent dentitions of the same individuals. In contrast to studies in the literature in which treatment records have been used, both investigations were formal epidemiological field studies using calibrated examiners and WHO (1971) caries diagnostic criteria. A firm association was found between caries in the primary and permanent dentitions (r = 0.34).

Isolation and characterization of Campylobacter pyloridis from gastric biopsies.

Gastric biopsy specimens were examined microbiologically and histologically for the presence of Campylobacter pyloridis. Of 51 randomly selected patients, 22 (43%) were found to harbor C. pyloridis in the gastric mucosa. The histologic demonstration of spiral organisms observed by staining with hematoxylin and eosin correlated well with microbiologic isolation of the organisms. There was a strong association (95.5%) between C. pyloridis in the gastric mucosa and histologically defined gastritis. However, there was no obvious association between C. pyloridis and ulcers. All C. pyloridis strains isolated exhibited uniform biochemical characteristics and had almost identical protein profiles, which indicated that they belong to a relatively homogeneous group distinct from other Campylobacter species. All C. pyloridis isolates were uniformly susceptible to ampicillin, amoxicillin, cephalothin, gentamicin, kanamycin, tetracycline, coumermycin, ciprofloxacin, novobiocin, clorobiocin, and nitrofurantoin. They were moderately resistant to nalidixic acid.

Isolation of an Ustilago maydis ERG11 gene and its expression in a mutant deficient in sterol 14 alpha-demethylase activity.

A gene (ERG11) encoding cytochrome P450 sterol 14 alpha-demethylase (P450(14DM)) was isolated from the maize pathogen, Ustilago maydis, by amplifying part of the coding region of the gene using PCR and by employing the amplified DNA fragment as a hybridization probe to recover the complete gene from an U. maydis lambda EMBL3 genomic library. The deduced amino acid sequence of the U. maydis gene showed homology to P450(14DM)s from other organisms and contained specific motifs which were hallmarks of P450s. Expression of the gene in an U. maydis mutant (A20) deficient in P450(14DM) led to only a partial restoration of P450(14DM) activity. Accumulation of ergosta-7,22-dienol and ergost-7-enol in A20 transformants containing the ERG11 gene implied that an additional mutation affecting sterol delta 5,6-desaturase activity accompanied the P450(14DM) lesion.

Water fluoridation and fluoride supplementation: considerations for the future.

The extensive literature on water fluoridation and fluoride supplementation is discussed, looking critically at the benefits of systemic fluoride availability in the prevention of dental caries and at the adverse factors of enamel fluorosis which can occur from the ingestion of too much fluoride during the period of tooth development. Recommendations are made for the future use of fluorides, emphasizing that water fluoridation is a safe and proven health measure which should be continued. Caution in the use of other fluoride supplementation methods is raised, especially when related to compliance and the use of fluoride supplements which are under the control of the individual. Targeting of children who would benefit from fluorides and additional preventive dental health measures is recommended.

The level and timing of systemic exposure to fluoride with respect to caries resistance.

Material related to water fluoridation and fluoride availability has been examined for changing patterns of fluoride intake by humans over recent years. The difficulty of separating systemic and topical fluoride action from water and foods from that found in fluoride agents used in preventive treatment programs is discussed. Recommendations are made that water fluoridation is a well-proven program and should be continued, but that fluoride supplementation programs under the control of the individual should be carefully evaluated and, if used, should be restricted to periods after the secretory stage of enamel formation is normally finished for anterior teeth, with supplements commenced during the pre-eruption maturation period and continuing until permanent tooth eruption is complete. Although supplements can also give a topical source to the teeth, depending on the way the supplement is consumed and the duration of time it is available in the mouth, other methods of topical fluoride provision are endorsed, and these should continue through life. It is suggested, in respect of epidemiology studies, that data collected before the availability of fluoride dentifrices in 1971 should be re-examined.

Fluoride intake from beverage consumption.

Previous studies have shown that fluoride is present in beverages prepared with fluoridated water. The purpose of this study was to determine the availability of fluoride from beverages consumed in adjacent fluoridated and non-fluoridated communities taking into account fluoride supplementation regimens. Children in grade six were invited to participate in recording of beverage intake in two cities in Alberta, Canada: Wetaskiwin, with water supplies fluoridated at 1.08 ppm F, and Camrose, non-fluoridated with water supplies at 0.23 ppm F. Three-day beverage intake records--"Drink Diaries"--were collected from 179 children in Wetaskiwin and 230 children in Camrose. Fluoride values, based on the analyses of Hargreaves, were assigned to the reported consumption of the children with the three highest and three lowest total beverage intakes in each community. A wide range of available fluoride was found. A substantial source of fluoride was shown to be available in the non-fluoridated community from beverages other than water, primarily from carbonated beverages commercially prepared with fluoridated water. Available beverages and actual consumption should be considered in the prescription of fluoride supplementation for children with minimal fluoride in their drinking water.

Epidemiology of dental caries in the premolar and second molar teeth of Scottish children in relation to pits and fissures.

To evaluate the potential benefits from elimination of dental caries in the fissures of teeth, surface patterns of decay were calculated for all surfaces of the premolar and second molar teeth of 98 children followed longitudinally for 5 years, between ages 11 and 15 years. Tooth eruption and susceptibility were also examined in relation to the administration of sealant programs. The children who were part of the control group of a fluoride dentifrice study on the Scottish Isle of Lewis, had low exposure to fluorides, high caries attack and very low restorative treatment levels; so true surface caries distribution was not masked. Variation in tooth eruption and susceptibility suggested that semiannual applications of preventive agents at each year age 10 through 15 might be required. Using hypothetical percentage reductions, the substantial potential benefits for caries control of the early use of completely retained occlusal, as well as buccal and lingual (molars), fissure sealants are conclusively demonstrated. However, improvements in the present technology of fissure sealants and their application are apparently required if these benefits are to be extended to large groups of children.

Dental caries and social factors in 12-year-old South African children.

Dental caries prevalence (percentage caries-free) and experience (DMFS) were recorded, in 414 12-yr-old Indian and 401 white children living in adjacent urban communities with the same fluoride concentration in the drinking water (0.21-0.33 ppm) using WHO (11) criteria. Details of social factors: education level, family income, home space and occupants and parental occupation were obtained by questionnaire. Dental caries was significantly worse in the Indian children with regard to numbers caries-free (30%--white and 40%--Indian) and DMFS mean (sd) (3.65 (3.98) and 2.66 (3.49) working group, respectively). Social class, white or blue collar, family income and room to person ratio were significantly associated with dental caries in the white children but there were no significant associations in the Indian children. Multiple regression analysis showed race and sex to be significant factors.

Energy intake, dental caries and periodontal disease in 11-year-old black children in two regions of Southern Africa: KwaZulu and Namibia.

The study examined energy intake in relation to dental caries and periodontal disease in 11-yr-old rural and urban black children in low fluoride areas of KwaZulu and Namibia (0.15 ppm F) and one higher fluoride area of Namibia (1.56 ppm F). Twenty-four hour dietary recalls were conducted by trained interviewers and daily energy intake estimated using the MRC dietary analysis programme. DMFS was recorded according to WHO criteria: periodontal disease was measured using CPITN and SAS was used for statistical analysis. The prevalence of dental caries and periodontal disease (using CPITN), were compared within three energy groupings; < or = 850 kcal/day; > 850, < 1400 kcal/day and > or = 1400 kcal/day. The rural low fluoride Namibian children had the lowest mean energy intake (616 kcal/day), which also was the grouping with highest healthy periodontal prevalence (65%). The urban groups had higher energy intakes than the rural communities. Statistically significant effects on caries prevalence were seen for country and fluoride grouping; for periodontal disease, significant effects were noted for country, fluoride group and environment. Energy intake had no statistically significant effect, so this is not a risk marker for the disease.

Study of a fissure sealant in mentally retarded Canadian children.

The occlusal fissure of 812 permanent and primary posterior teeth of 160 retarded children were sealed with a fluid resin which was polymerized with an ultra-voilet lamp. A half mouth technique was used to evaluate the effectiveness of the sealant in the prevention of fissure caries. The 1st year, the sealant was retained intact on 73 percent of the permanent teeth and on 64 percent of the primary teeth. After 2 years, the sealant was retained intact on 61% of the permanent teeth and on 40% of the primary teeth. The retention of the fissure sealant was better on premolars than molars both in the 1stand in the 2nd year. A single application of the fissure sealant was effective in reducing fissure caries up to 2 years.

A 5-year clinical evaluation of the effectiveness of a fissure sealant in mentally retarded Canadian children.

The occlusal fissures of 812 permanent and primary posterior teeth were sealed with an ultraviolet polymerisable resin. A half mouth technique was used to evaluate the effectiveness of the sealant in the prevention of fissure caries. At the end of 5 years 19.3% of 409 teeth in 103 children had the sealant completely intact and fissures were partially sealed in 20.8%. Retention was greatest in the mandibular pre-molars. The decay rate was less than half in the treated teeth compared to the control teeth. The net gain was 62 teeth and the percent effectiveness was 57.9%. Thus there was still a highly significant effect of a single application of the fissure sealant after 5 years. Simple cost benefit calculations indicate that the technique is not suitable as a public health measure but has merit for mentally retarded persons and in private practice situations.

The dmfs and dmft of young South African children.

As part of a series of frequent epidemiological field studies to determine caries prevalences in the primary dentition of young South African children, 1436 children of 1-4 yr of age from five ethnic groups were examined. Using WHO diagnostic criteria decayed, missing, and filled surfaces were determined with mirror and probe and caries free, dmfs, dfs, ds, mfs, and dmft scores were calculated. The investigation has shown that urban coloured and Indian children have the highest caries prevalences and urban white children have the lowest. It is suggested that the percentage of caries-free children should be used to set goals for reduction in caries.

Accumulation, distribution, and toxicity of copper in sediments of catfish ponds receiving periodic copper sulfate applications.

Copper sulfate (CuSO4) is applied periodically to commercial channel catfish (Ictalurus panctatus) ponds as an algicide or parasiticide. Current understanding of the chemistry of copper in soil-water systems suggests that copper may accumulate in pond sediments, although the forms and potential bioavailability of copper in catfish pond sediments are not known. This study investigated the accumulation and distribution of copper in the sediment of catfish ponds receiving periodic additions of CuSO4.5H2O. All ponds were constructed in Sharkey (very-fine, smectitic, thermic Chromic Epiaquert) soil. Nine 0.40-ha ponds received 59 applications of 2.27 kg CuSO4.5H2O per application per pond over 3 yr; no CuSO4.5H2O applications were made to nine additional ponds. Total Cu concentration in the sediments of CuSO4.5H2O-amended catfish ponds (172.5 mg kg(-1)) was four to five times higher than that in the sediments of nonamended ponds (36.1 mg kg(-1)). Copper accumulated in catfish pond sediments at a rate of 41 microg kg(-1) dry sediment for each 1 kg ha(-1) of CuSO4. 5H2O applied to ponds. Copper in the sediments of amended ponds was mainly in the organic matter-bound (30.7%), carbonate-bound (31.8%), and amorphous iron oxide-bound (22.1%) fractions with a considerable fraction (3.4%; 3 to 8 mg kg(-1)) in soluble and exchangeable fractions. This indicates that Cu accumulates differentially in various fractions, with proportionally greater initial accumulation in potentially bioavailable forms. However, toxicity bioassays with amphipods (Hyallela azteca) and common cattail (Typha latifolia L.) indicated that the effect of exposure to amended or nonamended pond sediments was not different.

An inquiry into the effects of health related behaviour on dental health among young Asian children resident in a fluoridated city in Canada.

In low-fluoride areas, infant feeding practices have been implicated in the aetiology of extensive caries found in young Asian children. The purpose of this study was to compare the findings in low-fluoride Leeds, UK with fluoridated Edmonton, in Canada. A multilingual interpreter interviewed Asian parents, and their children aged 2 to 5 years were then given a dental examination. From the initial sample contacted by post, a 72 per cent response rate was achieved. Of the 72 parents interviewed, three-quarters reported that the child was initially breast fed, 11 for over 12 months. The majority of children continued bottle feeding beyond 24 months of age, and one-third drank sweetened milk. Two-thirds of the sample were caries free. The continued use of a feeding bottle per se was not associated with caries experience, but caries was more likely to occur if sugar, honey or cereal were added to the drink. A positive association was found between caries experience and sustained breast feeding beyond 12 months of age. Social variables, including father's occupation and mother's ability to speak English were not related to caries experience. The results confirm that, as in the UK, South Asian parents in Canada provide feeding bottles for their children's drinks well beyond infancy. Nevertheless, in a fluoridated city, bottle-feeding practices were not associated with caries experience unless drinks were sweetened. However, prolonged breast feeding was found to be harmful to dental health. The role of fluoride ingestion in relation to these feeding practices is discussed.

Community Periodontal Index of Treatment Needs (CPITN) in KwaZulu and Namibia in 11-year-old children in 1988.

A sample of 603 11-year-old children from four low fluoride (less than 0.15 ppm) and one higher fluoride (1.56 ppm) communities in Namibia and KwaZulu were examined in 1988 using the CPITN. In a rural low fluoride community in Namibia only 6 per cent of children had healthy mouths compared with 42-58 per cent in the other communities. The main periodontal lesion seen was gingival bleeding (19-47 per cent) followed by calculus (6-47 per cent). There is a need for both oral hygiene improvement and simple intervention.

The periodontal status of 13-year-old children in western Canada using the CPITN index.

A large study of the dental health of children in the Canadian province of Alberta was undertaken in 1985. A ten per cent sample of 13-year old children (3117) was selected. This study reports on the gingival status of the children using the community periodontal index of treatment needs (CPITN). The findings show that the children have few periodontal problems and that the main treatment needs are oral prophylaxis and improvement in personal oral hygiene. The World Health Organisation guideline for the year 2000 in respect of the long-term goals for periodontal health is met in this Canadian population.