Redox biomarkers in saliva and nuclear abnormalities in jugal epithelial cells of individuals with type 2 diabetes mellitus and periodontitis

OBJECTIVE

To evaluate salivary redox biomarkers levels in individuals with periodontitis and type 2 diabetes mellitus (T2DM) and correlate with periodontal parameters and nuclear alterations in epithelial cells from jugal mucosa.

DESIGN

Sixty individuals were categorized into three groups: T2DM with periodontitis (DM, n = 20), non-T2DM with periodontitis (PE, n = 20), and non-T2DM with periodontal health (HC, n = 20). All participants underwent fasting blood glucose and glycated hemoglobin measurements. After a periodontal examination, samples of epithelial cells from the jugal mucosa and saliva were collected. DNA damage was assessed by counting nuclear abnormalities using cytological analysis. Biomarkers of oxidative stress were determined through biochemical methods. Significant differences among groups were assessed using Kruskal-Wallis, Mann-Whitney, and Chi-square tests at a 5% significance level. Data were analyzed using Spearman's correlation coefficient, linear regression, and logistic regression.

RESULTS

Frequencies of nuclear abnormalities, as well as levels of reduced glutathione and uric acid, were significantly higher in the DM group compared to the PE and HC groups (p < 0.05). Fasting glucose, glycated hemoglobin, nuclear abnormalities, reduced glutathione, and uric acid exhibited positive correlations with periodontal parameters (p < 0.05). Furthermore, reduced glutathione was associated with dental biofilm (OR = 1.027 [95% CI, 1.004-1.049]) and condensed chromatin (OR = 0.415 [95% CI, 0.196-0.878]).

CONCLUSIONS

Periodontitis and T2DM are correlated with nuclear abnormalities, as well as salivary reduced glutathione and uric acid levels. Moreover, a higher prevalence of teeth with dental biofilm increases the likelihood of elevated levels of reduced glutathione in saliva, while the presence of condensed chromatin decreases that likelihood.

Coronary atherosclerosis and periodontitis have similarities in their clinical presentation

Background

Periodontitis (PE) and coronary heart disease (CHD) possess multiple mechanisms for a putative association. This case-control study compared the periodontal status among CHD subjects to controls without CHD, while also investigating atheroma invasion by known periodontal pathogens.

Methods

161 subjects participated in this study were divided into three CHD groups: No CHD, chronic CHD, acute CHD. Additional analysis involved grouping subjects according to number of atheromas: no atheroma, 1-4 atheromas, 5-18 atheromas. Data were collected from medical records, periodontal examinations, and questionnaires that included demographic, behavioral, and oral health variables. Angiographic catheterizations were analyzed according to the number of atheroma lesions, lesion size, lesion location, and atheroma lesion stability. Lipoprotein profile, inflammatory markers and cells were analyzed. The microbiological branch added 30 individuals who had their atheroma lesion and subgingival plaque analyzed using polymerase chain reaction probes against the 16 s region, red complex and Aggregatibacter actinomycetemcomitans' DNA.

Results

Subjects with CHD had high levels of systemic inflammatory markers and low levels of high-density lipoproteins compared to subjects without CHD. Subjects without CHD and clear coronaries had a prevalence of mild CAL, while individuals with more atheroma lesions had advanced CAL and more active PE. Subjects with more advanced CAL were 4 times more likely to have CHD compared to subjects with less, which is comparable to smoking. Only 4 subjects had the screened pathogens detected in atheroma, although these subjects also have the screened pathogens in subgingival plaque. However, 80% of atheromas had bacteria.

Conclusions

CHD and PE showed similarities in progression while active PE led to more atheroma lesions that also tended to be larger in size.

Quantitative gingival crevicular fluid proteome in type 2 diabetes mellitus and chronic periodontitis

OBJECTIVE

The aim of this study was to investigate the proteome of the gingival crevicular fluid comparing the relative abundance of proteins from type 2 diabetes mellitus (2DM) individuals and chronic periodontitis (CP) affected sites, subjects affected by both conditions and healthy individuals.

MATERIAL AND METHODS

Twenty individuals were equally allocated in four groups, 2DM with CP, 2DM periodontally healthy, CP without 2DM, and periodontally healthy without 2DM. The relative quantification of proteins was accessed with iTRAQ labeling and mass spectrometry.

RESULTS AND CONCLUSION

A total of 104 proteins showed significant differences in abundance in pairwise comparisons. Some presented different levels in all diseased groups as compared to control, either increasing (rap guanine nucleotide exchange factor, S100A8, S100A9, and immunoglobulins) or decreasing (actins, myristoylated alanine-rich C-kinase substrate, and glutathione S-transferase). Other differences were specific for a given condition: Titin, neutrophil elastase, and myeloperoxidase levels were higher in the DP group, cathelicidin antimicrobial peptide decreased in CP, and annexin decreased in DH. These differences in the proteome can provide clues for further studies that will validate the variation in their levels and their role in both diseases.

Biosurfactant-induced remediation of contaminated marine sediments: Current knowledge and future perspectives

The contamination of marine sediments is widespread in coastal regions of the world and represents a major concern for the potential detrimental consequences on ecosystems' health and provision of goods and services for human wellbeing. Thus, there is an urgent need to find sustainable and eco-compatible solutions for the remediation of contaminated sediments. Bioremediation is a low cost and environmental-friendly strategy with a high potential for the remediation of contaminated marine sediments. Here we review the potential application of biosurfactants produced by microbial taxa for the remediation of contaminated marine sediments and we discuss future research needs to develop efficient and eco-sustainable biosurfactant-based strategies for the recovery of contaminated marine sediments, in view of large-scale applications.

No association between periodontitis and preterm low birth weight: a case-control study

PURPOSE

This study aimed to investigate the association between periodontitis in pregnant women and adverse pregnancy outcomes by heeding confounding risk factors for preterm low birth weight infants.

METHODS

This study was reported according to The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) Statement. A case-control study was conducted. Medical records of all pregnant women attending a prenatal care clinic were screened. Those between 21 and 34 years and gestational age of 28-32 weeks were initially enrolled in the study. The exclusion criteria were then applied: diabetes mellitus, genitourinary tract infections, or HIV infection; previous multiple gestations; previous preterm birth/low birth weight infants; in vitro fertilization procedures; placental, cervical/uterine abnormalities; history of infertility; history of drug abuse; and any medical conditions that required antibiotics prophylaxis. Patients' anthropometric, demographic, and behavioral characteristics were collected. The periodontal clinical parameters were obtained from six sites per tooth: clinical attachment level, probing pocket depth, dental plaque index, and gingival bleeding index. Women were then allocated into two groups: mothers of preterm and/or low birth weight newborns (cases) and mothers of full-term and normal birth weight newborns (controls).

RESULTS

Periodontal clinical parameters were analyzed and reported separately for each group, and no significant differences were observed (p > 0.05). Logistic regression analysis revealed that periodontal clinical parameters were not associated with the adverse pregnancy outcomes.

CONCLUSION(S)

After controlling for confounding factors, our results suggest that maternal periodontal disease is not a risk factor associated with preterm low birth weight infants.

Marine microorganisms as a promising and sustainable source of bioactive molecules

There is an urgent need to discover new drug entities due to the increased incidence of severe diseases as cancer and neurodegenerative pathologies, and reducing efficacy of existing antibiotics. Recently, there is a renewed interest in exploring the marine habitat for new pharmaceuticals also thanks to the advancement in cultivation technologies and in molecular biology techniques. Microorganisms represent a still poorly explored resource for drug discovery. The possibility of obtaining a continuous source of bioactives from marine microorganisms, more amenable to culturing compared to macro-organisms, may be able to meet the challenging demands of pharmaceutical industries. This would enable a more environmentally-friendly approach to drug discovery and overcome the over-utilization of marine resources and the use of destructive collection practices. The importance of the topic is underlined by the number of EU projects funded aimed at improving the exploitation of marine organisms for drug discovery.

Levels of HIV-1 in subgingival biofilm of HIV-infected patients

AIM

The aims of the current study were to compare the levels of HIV-1 in the subgingival biofilm (SHVL) between detectable and undetectable plasmatic HIV-1 viral load (PHVL) in HIV-infected patients as well as to determine the association of SHVL with PHVL and clinical periodontal parameters.

MATERIAL AND METHODS

Forty-one HIV-infected individuals were divided into two groups: detectable (21) and undetectable (20) PHVL. Subgingival biofilm samples were obtained for detection and quantification of HIV-1 by real-time RT-PCR. To estimate the effect of co-variables on the outcome undetectable SHVL, the Generalized Estimation Equation (GEE) was employed.

RESULTS

Detectable SHVL was observed only in the detectable PHVL group and the detection of the HIV-1 was observed in 40% of these individuals. In the bivariate analysis between co-variables from the individual level and the outcome SHVL, significant difference was observed only for the CD4+ T lymphocytes levels (p = 0.017). The multiple logistic model demonstrated that only CD4+ T lymphocytes levels had a significant effect on the outcome undetectable SHVL [OR 8.85 (CI 3.6-9.2), p = 0.002].

CONCLUSION

HIV-1 can be detected and quantified in the subgingival biofilm of HIV-infected individuals, but these findings are not associated with PHVL and periodontal clinical parameters.

The association between detectable plasmatic human immunodeficiency virus (HIV) viral load and different subgingival microorganisms in Brazilian adults with HIV: a multilevel analysis

BACKGROUND

This study investigates the association between detectable plasmatic human immunodeficiency virus (HIV) viral load (HVL) and high levels of periodontal- and non-periodontal-related microorganisms in the subgingival microbiota of individuals with HIV.

METHODS

Thirty-seven individuals with HIV were divided into two groups: 1) detectable HVL (n = 15); and 2) undetectable HVL (n = 22). Subgingival biofilm samples were obtained, and the levels of 35 microbial species were determined by the checkerboard DNA-DNA hybridization method. Periodontal clinical measures and laboratory and sociodemographic data were also registered. χ(2) test, Fisher exact test, and Mann-Whitney U test were used to compare groups. Multilevel ordinal regression models were used to test the association between HVL and the levels of 35 microbial species in subgingival biofilm, adjusted for confounders.

RESULTS

Of the 35 species studied, 11 (31.4%) showed higher mean levels in the detectable HVL group than undetectable HVL group (P <0.001). These species included Actinomyces naeslundii II, Actinomyces israelii, Actinomyces odontolyticus, Veillonella parvula, Capnocytophaga gingivalis, Eikenella corrodens, Campylobacter concisus, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, and Candida albicans. Significant associations between detectable HVL and high levels of microorganisms, adjusted for confounders, were observed for A. naeslundii I, Actinomyces gerencseriae, C. gingivalis, E. corrodens, C. concisus, Prevotella nigrescens, T. forsythia, and Dialister pneumosintes.

CONCLUSION

Detectable plasmatic HVL in individuals with HIV was associated with elevated levels of known periodontal pathogens, such as P. nigrescens, T. forsythia, and E. corrodens, as well as C. concisus, C. gingivalis, and D. pneumosintes in the subgingival biofilm.

Effect of non-surgical periodontal treatment on chronic kidney disease patients

Chronic kidney disease (CKD) is a debilitating systemic condition. Our working hypothesis is that CKD predialysis patients with periodontitis would respond poorly to periodontal treatment owing to immunologic compromise. Twenty-one predialysis patients (group 1) and 19 individuals without clinical evidence of kidney disease (group 2) with chronic periodontitis were subjected to non-surgical periodontal treatment with no antibiotics. Clinical periodontal and systemic parameters were evaluated at baseline and 3 months after treatment. Both groups showed significant and similar post-treatment improvements in all periodontal parameters examined. Most interestingly, periodontal treatment had a statistically significant positive effect on the glomerular filtration rate of each individual (group 1, p = 0.04; group 2, p = 0.002). Our results indicate that chronic periodontitis in predialysis kidney disease patients improved similarly in patients with chronic periodontitis and no history of CKD after receiving non-surgical periodontal therapy. This study demonstrates that CKD predialysis patients show a good response to non-surgical periodontal treatment.

The relationship between diabetes mellitus and destructive periodontal disease: a meta-analysis

PURPOSE

The aim of this study was to systematically review the studies on the association between diabetes mellitus (DM) and destructive periodontal disease.

METHODS

The methods applied include a literature search strategy, inclusion and exclusion criteria for selecting the studies, characteristics of the studies, quality assessment and meta-analysis. Data sources included PubMed, EMBASE, SciELO and LILACS. Selected papers were articles relating to human studies investigating whether or not diabetes is a risk factor for periodontitis and if it influences the response to periodontal therapy. Those papers that were published between January 1980 and June 2007 were retrieved.

RESULTS

Of the 2440 identified studies, 49 cross-sectional and eight longitudinal studies met the inclusion criteria. Twenty-seven of the 49 cross-sectional studies that are included in this review detected more periodontal disease in diabetic subjects compared with non-diabetic subjects. The greater risk of periodontal disease progression was associated with type 2 DM, and one study associated DM with response to periodontal therapy. Methodological flaws of most of the studies included inadequate control for confounders, insufficient statistical analysis and lack of information about sampling design. Random effect model showed a significant association with clinical attachment level (mean difference = 1.00 [CI 95% = 0.15 to 1.84]) and periodontal pocket depth (mean difference = 0.46 [CI 95% = 0.01 to 0.91]) between type 2 diabetics and non-diabetics.

CONCLUSIONS

Type 2 DM can be considered a risk factor for periodontitis. More studies are needed to confirm the harmful effects of type 1 DM on periodontal disease.

Oral mucosa alterations induced by cyclosporin in mice: morphological features

BACKGROUND AND OBJECTIVE

The mechanisms involved in the pathogenesis of cyclosporin A-induced gingival hyperplasia are not well understood. The present work aimed at developing a mouse model with the characteristics of the human process, i.e. time of appearance, dose dependency and the capacity of developing in a variety of genetic backgrounds. This model would present the advantages of using a very well known animal species, small and easy to handle, with a number of experimental reagents (antibodies, etc.) already available against its products.

METHODS

Three different strains of mice were used: CBA, F1(C57Bl x DBA), Balb/c. Groups of mice received different concentrations of cyclosporin A (CSA) (10 mg/kg, 25 mg/kg and 40 mg/kg body weight) intraperitoneally five times a week. Anatomical and histological alterations were recorded at various time intervals.

RESULTS

All strains of mice presented gingival hyperplasia after 8 weeks of CSA treatment. A dose-dependency was observed with regard to the time of first appearance of alterations. Increased redness was seen in all animals at the sixth week, independent of the dosage used. Histologic examination exhibited increased vascularization, epithelial and connective tissue thickening, edema and a mononuclear infiltrate.

CONCLUSIONS

It was possible to develop CSA-induced gingival hyperplasia in mice with the characteristics described in humans and other species. The use of this animal model may help in the elucidation of the process involved in CSA-induced gingival overgrowth.

Self-regulating interest: the moderating role of hardiness and conscientiousness

Sansone, Weir, Harpster, and Morgan (1992) found that individuals intentionally regulated their interest in an activity when they had both the need (the task was boring) and a reason to exert the effort (an ostensible health benefit). The present study examined Hardiness and Conscientiousness as moderators of this self-regulatory process when individuals had the option of quitting in addition to the options of persisting and of engaging in interest-enhancing strategies. Undergraduates performed a boring copying activity under instructions to stop when they felt they could evaluate the task. Half were told that their evaluations would help researchers develop good jobs for others (Benefit). Results indicated high hardy individuals copied more letters when they were provided the additional Benefit information, and this effect was mediated through their attempt to make the task more interesting. High conscientious individuals persisted longer than individuals lower in conscientiousness independently of the benefit manipulation or strategy use. Implications of individual differences in self-regulation of motivation are discussed.

The role of problem definitions in understanding age and context effects on strategies for solving everyday problems

The participants (107 preadolescents, 124 college students, 118 middle-aged adults, and 131 older adults) described 2 everyday problems (1 unconstrained, the other constrained to 1 of 6 domains) that they experienced and their goals and strategies. Problem definitions reflected interpersonal or competence components or both; strategies reflected altering cognitions, actions, or regulating and including others. Age differences in problem definitions were found. For unconstrained-domain problems, age and problem definition were related to strategies; for unconstrained-domain problems age differences in strategies were not found. For constrained-domain problems, strategies related to problem domain and problem definition, with problem definition the better predictor of strategies. The results illustrate the value of individuals' problem definitions for addressing age and context effects on strategies used.

The role of problem definitions in understanding age and context effects on strategies for solving everyday problems

The participants (107 preadolescents, 124 college students, 118 middle-aged adults, and 131 older adults) described 2 everyday problems (1 unconstrained, the other constrained to 1 of 6 domains) that they experienced and their goals and strategies. Problem definitions reflected interpersonal or competence components or both; strategies reflected altering cognitions, actions, or regulating and including others. Age differences in problem definitions were found. For unconstrained-domain problems, age and problem definition were related to strategies; for unconstrained-domain problems age differences in strategies were not found. For constrained-domain problems, strategies related to problem domain and problem definition, with problem definition the better predictor of strategies. The results illustrate the value of individuals' problem definitions for addressing age and context effects on strategies used.

The association of mutans streptococci and non-mutans streptococci capable of acidogenesis at a low pH with dental caries on enamel and root surfaces

Coronal dental plaque from each of 12 caries-positive subjects (Group I) was pooled from "white spot" tooth surface areas and, separately, from sound surface areas; sound surface areas in each of 18 caries-free subjects (Group II) were sampled similarly. Two samples, one consisting of material from a root-surface lesion and another of plaque from a sound root-surface area, were obtained from each of another 10 subjects (Group III). The samples from Groups I and II were evaluated for: (1) pH-lowering potential in vitro with dispersed plaque suspensions, excess glucose supply, and a 60-minute test; (2) the levels of mutans streptococci (MS) and lactobacilli; and (3) the distribution of the predominant non-mutans streptococci (non-MS) according to their final pH in glucose broth; only microbial analysis was done for the Group III samples. The levels of the MS were generally positively associated with caries. A weaker positive association was found for the levels of those non-MS capable of acidogenesis at low pH (final pH < 4.4). The latter generally far outnumbered the MS in all types of samples. The levels of lactobacilli were nearly always very low. The pH-lowering potential (final pH and pH drop rate) was higher for plaque from "white spot" areas than for plaque from sound surface areas (Group I). The samples from caries-free subjects (Group II), however, exhibited a pH-lowering potential which was not significantly different from that of both types of samples from the caries-active subjects (Group I).(ABSTRACT TRUNCATED AT 250 WORDS)

Once a boring task always a boring task? Interest as a self-regulatory mechanism

A process was proposed through which individuals regulate their motivation to perform necessary but uninteresting activities over time. If committed to continuing, individuals may engage in interest-enhancing strategies that can change the activity into something more positive to perform. In Study 1 Ss performed novel tasks and generated strategies to make regular performance interesting. In Study 2 Ss actually used these strategies primarily in conditions indicating a self-regulatory attempt: The task was currently boring, there was a perceived reason to continue (alleged health benefit), and a relevant strategy was available. Strategy use was associated with a change in activity definition and greater likelihood of subsequently performing the activity. In Study 3 Ss beliefs about how to maintain motivation to perform more everyday activities emphasized the importance of regulating interest relative to other self-regulatory strategies.

Once a boring task always a boring task? Interest as a self-regulatory mechanism

A process was proposed through which individuals regulate their motivation to perform necessary but uninteresting activities over time. If committed to continuing, individuals may engage in interest-enhancing strategies that can change the activity into something more positive to perform. In Study 1 Ss performed novel tasks and generated strategies to make regular performance interesting. In Study 2 Ss actually used these strategies primarily in conditions indicating a self-regulatory attempt: The task was currently boring, there was a perceived reason to continue (alleged health benefit), and a relevant strategy was available. Strategy use was associated with a change in activity definition and greater likelihood of subsequently performing the activity. In Study 3 Ss beliefs about how to maintain motivation to perform more everyday activities emphasized the importance of regulating interest relative to other self-regulatory strategies.

Mutans streptococci and non-mutans streptococci acidogenic at low pH, and in vitro acidogenic potential of dental plaque in two different areas of the human dentition

Samples of human dental plaque were obtained from sound tooth surfaces in the lower anterior and upper posterior areas of each of 11 subjects with various degrees of caries experience. Both types of plaque were compared for: (1) their pH-lowering potential [pH at 10 and 60 min after sugar addition and the pH drop between 0 and 10 min (delta pH)] with an in vitro method involving dispersed plaque suspensions and excess glucose supply; (2) the proportions of mutans streptococci; and (3) the distribution of the predominant non-mutans streptococci according to their final pH in glucose broth. Compared with plaque from the lower anterior area, plaque from the upper posterior area exhibited a significantly higher pH-lowering potential, i.e., a lower pH at 10 and 60 min and a greater delta pH and significantly higher levels of mutans streptococci. The final pH values for the non-mutans streptococci exhibited a wide range from about 4.4 to over 5.0. The proportions of such organisms designated as capable of acidogenesis at low pH (final pH less than 4.6), whether expressed as a percentage of the total non-mutans streptococci or of the total plaque flora, were significantly increased in plaque from the upper posterior area. The proportions of non-mutans streptococci capable of acidogenesis at low pH in plaque from the upper posterior area were also significantly increased, with decreasing pH values at 10 and 60 min.(ABSTRACT TRUNCATED AT 250 WORDS)

In vitro acidogenic potential and mutans streptococci of human smooth-surface plaque associated with initial caries lesions and sound enamel

Samples of human dental plaque were pooled from several "white spot" smooth tooth surface areas as well as from several clinically-sound tooth surface areas in each of 12 caries-positive college students. Each of the two samples from each subject was used for the determination of: (1) pH-lowering potential in vitro involving dispersed plaque suspensions, excess glucose supply, and a 60-minute test, and (2) the proportions of mutans streptococci and lactobacilli. When all subjects were considered, plaques from "white spot" areas, as compared with samples from sound surface areas, were characterized by significantly higher proportions of mutans streptococci, a lower starting ("resting") pH, a faster rate of pH drop between pH 6.0 and 5.0, and a lower minimum pH of the suspension; the lactobacillus proportions were generally very low in both types of plaques. For individual subjects, however, the proportions of mutans streptococci in plaque associated with "white spot" areas showed a wide range (0.001-10.0%), and samples with high as well as low levels of these micro-organisms could exhibit a high rate of pH drop and a low pH minimum. This suggests that, besides mutans streptococci and lactobacilli, other bacteria capable of acidogenesis at a low pH may contribute to the high pH-lowering potential exhibited by many plaques.

Remembering less and inferring more: effects of time of judgment on inferences about unknown attributes

Perceivers often infer the values of unknown attributes from evaluative expectancies. In 2 experiments, inferences about unknown attributes of a target made shortly after initial processing tended to be moderate, as perceivers presumably adjusted for the lack of directly relevant evidence. However, stronger inferences were drawn with the passage of time as memory of the absence of information faded. Expertise moderated this effect, as subjects highly knowledgeable of the target domain were much less likely than low or moderate knowledge subjects to draw extreme inferences over time. Memory-based inferences about unknown attributes were also found to be held with greater confidence than inferences made shortly after stimulus presentation.

Remembering less and inferring more: Effects of time of judgment on inferences about unknown attributes

Perceivers often infer the values of unknown attributes from evaluative expectancies. In 2 experiments, inferences about unknown attributes of a target made shortly after initial processing tended to be moderate, as perceivers presumably adjusted for the lack of directly relevant evidence. However, stronger inferences were drawn with the passage of time as memory of the absence of information faded. Expertise moderated this effect, as subjects highly knowledgeable of the target domain were much less likely than low or moderate knowledge subjects to draw extreme inferences over time. Memory-based inferences about unknown attributes were also found to be held with greater confidence than inferences made shortly after stimulus presentation.

Effects of instruction on intrinsic interest: the importance of context

Two studies examined how contextual cues influence the impact of receiving instructions for improving performance on intrinsic motivation. The authors proposed that whether instruction enhances or decreases motivation depends on the salience of performance goals. Goal salience was proposed to be a function of how an individual defines the activity, which, in turn, may be influenced by contextual features. To test this hypothesis, the authors used a computer game that emphasized fantasy in addition to skill, and they varied the presence of contextual cues highlighting performance. In Study 1, the authors varied the presence of prior performance feedback, and found that instruction decreased interest only when no prior performance feedback (positive or negative) was received. In Study 2, the authors explicitly manipulated contextual salience by describing the activity's goals as either skill- or fantasy-related. Instruction decreased interest in the fantasy-emphasis context, but increased interest in the skill-emphasis context. Furthermore, when instruction matched perceived goals Ss experienced greater positive affect while performing the task. The implications for models of intrinsic motivation are discussed.

Comparison of two methods for the small-scale extraction of DNA from subgingival microorganisms

Two methods were compared for the extraction of DNA from small numbers of bacterial cells. The first method involved lysis of cells with SDS in the presence of proteinase K, treatment with hexadecyltrimethyl ammonium bromide (CTAB) and precipitation of DNA with isopropanol. In the second method, DNA was extracted by treatment of the cells with guanidine hydrochloride (GHCl) and precipitated with ethanol. Thirty strains of representative gram positive and gram negative species were included in the study. Preparations derived from confluent growth on one-quarter of the surface of agar plates and from 10(8) cells were subjected to each extraction procedure and analyzed for their content of DNA, RNA and protein. The suitabilities of the resultant DNA for restriction enzyme digestion and biotin-labelling by a random primer technique were also assessed. In general, the CTAB method yielded greater amounts of DNA than the GHCl procedure. RNA was present in most preparations of both types, but in amounts detectable only by agarose gel electrophoresis. The latter technique also revealed that DNA was not excessively sheared by either procedure. Protein was detected in some CTAB and GHCl preparations, but was not consistently associated with one or the other method. DNA obtained by both methods could be digested by the restriction enzyme EcoR I. In addition, biotin-labelled DNA probes prepared from CTAB and GHCl preparations were capable of hybridizing with homologous target DNA fixed to nitrocellulose. Since the CTAB method was consistently successful in recovering DNA from preparations containing 10(8) cells, it may be more suitable for the direct treatment of single colonies taken from primary isolation plates or plaque samples.

"Reverse" DNA hybridization method for the rapid identification of subgingival microorganisms

A "reverse" hybridization method is described, in which whole chromosomal DNA was extracted from 10-20 colonies of "unknown" strains in pure culture and labelled with digoxigenin by a random primer technique. DNA probes were prepared from a total of 23 strains and hybridized with targets containing 100 ng purified, denatured DNA from 38 reference strains fixed to nitrocellulose. 21/23 digoxigenin-labelled DNA probes successfully detected all members of the homologous species present on filters. Probes to Fusobacterium nucleatum strains 364 and MG detected 3/4 and 1/4 members of this species, respectively; 13/23 probes were 100% specific, but cross reactions between 10 probes and DNA targets from closely related, heterologous species occurred in 15/834 possible instances. False-positive reactions that occurred between closely related species were, however, easily distinguished and did not prevent the accurate identification of probe strains. Digoxigenin-labelled probes were capable of detecting 100 pg of homologous DNA. The reverse hybridization procedure allows identification or grouping of a large number of isolates within 3 days and provides a more economical means of characterizing subgingival isolates than predominant cultivable techniques and conventional phenotypic testing. This method could be adapted for the direct identification of microorganisms in subgingival plaque samples.

Effects of instruction on intrinsic interest: The importance of context

Two studies examined how contextual cues influence the impact of receiving instructions for improving performance on intrinsic motivation. The authors proposed that whether instruction enhances or decreases motivation depends on the salience of performance goals. Goal salience was proposed to be a function of how an individual defines the activity, which, in turn, may be influenced by contextual features. To test this hypothesis, the authors used a computer game that emphasized fantasy in addition to skill, and they varied the presence of contextual cues highlighting performance. In Study 1, the authors varied the presence of prior performance feedback, and found that instruction decreased interest only when no prior performance feedback (positive or negative) was received. In Study 2, the authors explicitly manipulated contextual salience by describing the activity's goals as either skill- or fantasy-related. Instruction decreased interest in the fantasy-emphasis context, but increased interest in the skill-emphasis context. Furthermore, when instruction matched perceived goals Ss experienced greater positive affect while performing the task. The implications for models of intrinsic motivation are discussed.

Nicotine gum and self-help manuals in smoking cessation: an evaluation in a medical context

This study evaluated the effectiveness of nicotine chewing gum in smoking cessation, when incorporated into a behaviorally oriented self-help program. One hundred ninety-seven patients were randomly assigned to nicotine gum with a self-help manual, a self-help manual without gum, or a control condition, but received no further treatment from the prescribing physician. At six weeks, the nicotine gum group was superior to both the self-help and control conditions. By one year, many gum patients had relapsed, and the treatment effect was no longer significant. Patients who were able to quit initially were most likely to remain ex-smokers in the self-help condition. The clinical importance of these findings is discussed.