Disruption of the petB-petD intergenic region in tobacco chloroplasts affects petD RNA accumulation and translation.

Translation initiation in chloroplasts is a complex process involving a variety of cis-elements and trans-acting factors. Many chloroplast mRNAs are processed products of polycistronic primary transcripts, but the functional requirement for processing is mostly enigmatic. In tobacco, the petB and petD genes, which encode subunits of the cytochrome b6/f complex, are transcribed from the psbB operon, whose primary transcript is processed into products including di- or tricistronic, but not monocistronic, petB and petD mRNAs. To begin to identify elements important for petB and/or petD translation, we generated tobacco chloroplast transformants by inserting selectable aadA marker cassette in the petB-petD intergenic region. The resulting plants required sucrose for growth, and their phenotypes depended on the orientation of the aadA cassette. When aadA was inserted in the same transcriptional orientation as the psbB operon, petB and petD mRNAs were abundantly produced but aberrant in size, and only 25% of the wild-type amount of the cytochrome b6/f complex accumulated. With the aadA cassette in the opposing orientation, however, very little petD mRNA accumulated, and the cytochrome b6/f complex was undetectable. Polysome analysis suggested that petD mRNAs in both transformants were poorly translated, indicating that the intergenic region contains essential translational elements.

The sequence and secondary structure of the 3'-UTR affect 3'-end maturation, RNA accumulation, and translation in tobacco chloroplasts.

RNA maturation and modulation of RNA stability play important roles in chloroplast gene expression. In vitro and in vivo studies have shown that both the 5'- and 3'-untranslated regions (UTRs) contain sequence and structural elements that guide these processes, and interact with specific proteins. We have previously characterized the spinach chloroplast petD 3'-UTR in detail by in vitro approaches. This stem-loop forming sequence is a weak terminator but is required for RNA maturation and also exhibits sequence-specific protein binding. To test petD 3'-UTR function in vivo, tobacco chloroplast transformants were generated containing uidA reporter genes flanked by variants of the petD 3'-UTR, including one which does not form an RNA-protein complex in vitro, and one which lacks a stem-loop structure. Analysis of uidA mRNA indicated that a stable secondary structure is required to accumulate a discrete mRNA, and that changes in the 3'-UTR sequence which affect protein binding in vitro can also affect RNA metabolism in vivo. The 3'-UTR also influenced beta-glucuronidase protein accumulation, but not in proportion to RNA levels. These results raise the possibility that in tobacco chloroplasts, the 3'-UTR may influence translational yield.

Prevalence of spit tobacco use across studies of professional baseball players.

A review of published data, together with previously unpublished information, shows that the use of spit tobacco among professional baseball players continues to be alarmingly high. In spite of efforts to make players aware of the harmful effects, approximately 35 percent to 40 percent of professional baseball players still use spit tobacco, and about half of those have associated lesions. However, current efforts of the National Spit Tobacco Education Program, Major League Baseball, the Professional Baseball Athletic Trainers Society and the Major League Baseball Players Association are expected to result in a significant reduction in spit tobacco use in this population in the next decade.

A dental-based, athletic trainer-mediated spit tobacco cessation program for professional baseball players.

During 1997 spring training, the National Spit Tobacco Education Program provided a spit (smokeless) tobacco intervention program to 16 professional baseball clubs. The program consisted of an awareness-raising presentation and an opportunity to discuss quitting spit tobacco use with an expert cessation counselor. For two clubs, however, a more extensive intervention was pilot-tested for feasibility and acceptability among their major- and minor-league teams during their regularly scheduled health examinations at the beginning of spring training. The intervention included an oral exam by a dentist who advised spit tobacco users to stop and pointed out any spit tobacco-associated lesions in the player's mouth, brief cessation counseling by a specially trained dental hygienist, and ongoing support and follow-up by the certified athletic trainer to promote cessation. Findings from this pilot study indicate that this intervention, which is dependent upon involvement of dental professionals, was feasible to implement during spring training and appeared to be well-received by the athletes. Dental professionals are in an excellent position to advise and help spit tobacco users to quit and can have an important role in helping youth overcome this rapidly growing addiction.

Science and the shifting paradigm in dental education.

Dental education is faced with continuing challenges to adjust to external as well as internal pressures. These pressures are coming from a variety of sources that are often inconsistent in the nature and direction of change they would bring about. Pressure on the future direction of dental education are coming from sources such as an Institute of Medicine report, Pew Health Professions Commission reports, changes in the academic health centers in response to health care reform, and expectations of parent universities. Reactions to these and other forces are bringing about changes in the nature and extent of scientific research in schools of dentistry. As the educational programs continue to evolve, research will receive greater attention, and more of it will be funded from private sources.

Oral effects of smokeless tobacco use by professional baseball players.

This is a review of studies conducted from 1988-90 on the oral consequences of snuff and chewing tobacco use among professional baseball players. About half of the players studied were smokeless tobacco (ST) users, the majority of whom used snuff. Compared with non-users, players who used ST showed a significantly higher prevalence of leukoplakia, which was related to placement of the ST quid, and the frequency, amount, duration, and type of ST used. Sites adjacent to these mucosal lesions showed an increased prevalence of gingival recession with associated attachment loss, cervical abrasion, and root caries than did comparable sites in non-users. Extrinsic stain and occlusal attrition were also more frequent in ST users than in non-users. While ST use placed players at significantly increased risk for mucosal lesions and other oral problems, no differences were found between ST non-users and users in measurements of batting, fielding, and pitching performance during the baseball season.

Review of whole-organism bioassays: soil, freshwater sediment, and freshwater assessment in Canada.

Whole organism bioassays for the assessment of soil, freshwater sediment, and freshwater quality were evaluated for their application in the assessment and remediation of contaminated sites in Canada under the National Contaminated Sites Remediation Program. Using 3 essential and 12 desirable methodological criteria, bioassays were categorized as currently usable, prototype, or under development. Based on further considerations related to bioassay application, a battery of usable screening and definitive tests was recommended (with suggestions for augmentation) for each medium. Of the 18 bioassays reviewed for soil quality assessment, 6 were usable, 5 were prototypes, and 7 were under development. Battery screening and definitive tests included 14-day Eisenia andrei survival, 120-hr lettuce and radish seedling emergence, and 72-hr Selenastrum capricornutum growth inhibition. Augmentation with the following bioassays was recommended: soil/freshwater bacterial growth, arthropod reproduction, earthworm reproduction, and reproduction of other soil-dependent organisms. Of the 9 bioassays reviewed for freshwater sediment quality assessment, 1 was usable, 2 were prototypes, and 6 were under development. Three bioassays in the latter two groups were considered usable with the imminent completion of research underway. Screening tests selected included 10-day Chironomus tentans survival, 10-day Hyalella azteca survival, 10-day Hexagenia spp. survival, and 72-hr S. capricornutum growth inhibition. Definitive tests included screening tests, substituting 28-day H. azteca sexual maturation for 10-day survival. Augmentation with the following bioassays was recommended: sediment/freshwater bacterial test, 28-day Tubifex tubifex reproduction, and rooted aquatic plant growth. Of the 25 bioassays considered for freshwater quality assessment, 8 were usable, 7 were prototypes, and 10 were under development. Screening tests selected included 72-hr S. capricornutum growth inhibition; 48-hr Daphnia sp. survival, and 5- and 15-min Photobacterium phosphoreum bioluminescence. Definitive tests included first screening test, 7-day Ceriodaphnia dubia, 7-day fathead minnow larval survival, or 96-hr rainbow trout survival. Augmentation with the following bioassays was recommended: Brachionus calyciflorus 24-hr survival, 48-hr reproduction; freshwater bacterial growth; and aquatic vascular plant growth.

A program to help major league baseball players quit using spit tobacco.

There are few reports in the scientific literature that describe tested methods for helping people quit using spit (smokeless) tobacco. This paper reports data from a pilot study to determine the effectiveness of two dental-oriented interventions to promote cessation of ST use among major league baseball players. These preliminary findings suggest that interventions involving an oral examination and advice to quit, combined with behavioral counseling, may effectively decrease ST use among professional baseball players.

Histopathology of smokeless tobacco lesions in professional baseball players. Associations with different types of tobacco.

We examined 142 biopsy specimens of smokeless tobacco-associated oral mucosal lesions from 133 professional baseball players. Four types of epithelial change were observed in the specimens: hyperparakeratosis, hyperorthokeratosis, pale surface staining, and basal cell hyperplasia. These types of epithelial change were associated with the type of smokeless tobacco used (snuff or chewing tobacco) but not with the duration (years) or amount (hours per day) of use. The thickness of hyperkeratosis in a specimen correlated directly with the amount of smokeless tobacco use. The use of snuff was more frequently associated with development of oral mucosal lesions than was the use of chewing tobacco, and snuff appeared to cause a greater variety and severity of epithelial change than did chewing tobacco.

Reduction of Langerhans cells in smokeless tobacco-associated oral mucosal lesions.

Localized absence of epithelial Langerhans cells (LC) has been shown to affect systemic immune responses, allow microbial colonization and play a possible role in carcinogenesis. Because use of smokeless tobacco is associated with abnormal oral mucosal changes and development of carcinoma, we examined lesion and control specimens from 17 current users of smokeless tobacco to determine whether lesions showed changes in LC number or antigen expression. We identified LC by immunohistochemistry with antibodies to the antigens T6, HLA-DR, HLA-DQ, and HLA-DP. Lesion specimens contained fewer LC (means of 6 LC/mm and 10 LC/mm2) than did the corresponding control specimens (means of 14 LC/mm and 30 LC/mm2), and in each pair of lesion and autologous control specimens the reduction in LC was on average 58% (range, 3% to 95%). There were no apparent differences between lesion and control specimens in the number of LC expressing each of the four marker antigens. Reductions in LC occurred in all types of smokeless tobacco-associated lesions, regardless of increased epithelial thickness or changes in keratinization. Our data indicate that smokeless tobacco reduces the number of Langerhans cells at its site of contact with the oral mucosa.

Smokeless tobacco use and health effects among baseball players.

The effects of smokeless tobacco (ST) use were studied in 1109 members of major and minor league professional baseball teams during spring training in 1988. The prevalence of current ST use was 39%. The median age at initiation among users was 18 years, and the median duration of use was 5 years. Among users, 75% cited a snuff brand as their usual ST product. Oral leukoplakia was present in 46% (196/423) of current-week ST users and 1.4% (7/493) of nonusers (odds ratio, 60; 95% confidence interval, 28 to 130). Prevalence of oral leukoplakia among ST users increased with hours used per day and decreased with time lapsed since last use, and was higher in snuff users than in chewing tobacco users. Of the subjects with oral leukoplakia who underwent punch biopsy, 91 had benign hyperkeratosis and one had mild dysplasia. Overall prevalence of dental caries, gingivitis, and plaque did not differ between ST users and nonusers. In analyses confined to facial surfaces of mandibular incisor teeth, where ST is most commonly used, there were significant increases among users in both gingival recession and attachment loss. Users of ST did not differ from nonusers in blood pressure, pulse, total or high-density lipoprotein cholesterol level, or white blood cell count, but among users high-density lipoprotein cholesterol levels were inversely associated with serum cotinine levels. The major health effects of ST use among professional baseball players are oral leukoplakia and localized periodontal disease. The study population was young, physically fit, and characterized by relatively moderate short-term ST use.

Preventive dentistry. II. Periodontal diseases, malocclusion, trauma, and oral cancer.

This is the second of two articles reviewing the recommendations of the US Preventive Services Task Force for interventions by physicians, nurses, and other clinicians to prevent the major oral diseases and conditions. Physicians and other health professionals should be aware of their many opportunities to assist in preventive oral health care and should take appropriate action in collaboration with the patient's dentist.

Preventive dentistry. I. Dental caries.

Primary care physicians and nurses have numerous opportunities to assist in the prevention of dental caries, periodontal diseases, malocclusion, trauma to the mouth and teeth, and oral cancer. This is the first of two articles that provide background for the US Preventive Services Task Force recommendations for interventions by physicians, nurses, and other clinicians to prevent these oral diseases and conditions. Physicians and other health professionals are urged to be aware of these opportunities and to take appropriate action in collaboration with the patient's dentist.