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Biomedical subjects

B T Johnson

Publications and source records attributed to B T Johnson.

At least 19 recordsLinked to original sources
PubMed2002

Toxicity assessment of sediments from the Grand Calumet River and Indiana Harbor Canal in Northwestern Indiana, USA.

The objective of this study was to evaluate the toxicity of sediments from the Grand Calumet River and Indiana Harbor Canal located in northwestern Indiana, USA. Toxicity tests used in this assessment included 10-day sediment exposures with the amphipod Hyalella azteca, 31-day sediment exposures with the oligochaete Lumbriculus variegatus, and the Microtox Solid-Phase Sediment Toxicity Test. A total of 30 sampling stations were selected in locations that had limited historic matching toxicity and chemistry data. Toxic effects on amphipod survival were observed in 60% of the samples from the assessment area. Results of a toxicity test with oligochaetes indicated that sediments from the assessment area were too toxic to be used in proposed bioaccumulation testing. Measurement of amphipod length after the 10-day exposures did not provide useful information beyond that provided by the survival endpoint. Seven of the 15 samples that were identified as toxic in the amphipod tests were not identified as toxic in the Microtox test, indicating that the 10-day H. azteca test was more sensitive than the Microtox test. Samples that were toxic tended to have the highest concentrations of metals, polycyclic aromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs). The toxic samples often had an excess of simultaneously extracted metals (SEM) relative to acid volatile sulfide (AVS) and had multiple exceedances of probable effect concentrations (PECs). Metals may have contributed to the toxicity of samples that had both an excess molar concentration of SEM relative to AVS and elevated concentrations of metals in pore water. However, of the samples that had an excess of SEM relative to AVS, only 38% of these samples had elevated concentration of metals in pore water. The lack of correspondence between SEM-AVS and pore water metals indicates that there are variables in addition to AVS controlling the concentrations of metals in pore water. A mean PEC quotient of 3.4 (based on concentrations of metals, PAHs, and PCBs) was exceeded in 33% of the sediment samples and a mean quotient of 0.63 was exceeded in 70% of the thirty sediment samples from the assessment area. A 50% incidence of toxicity has been previously reported in a database for sediment tests with H. azteca at a mean quotient of 3.4 in 10-day exposures and at a mean quotient of 0.63 in 28-day exposures. Among the Indiana Harbor samples, most of the samples with a mean PEC quotient above 0.63 ( i.e., 15 of 21; 71%) and above 3.4 ( i.e., 10 of 10; 100%) were toxic to amphipods. Results of this study and previous studies demonstrate that sediments from this assessment area are among the most contaminated and toxic that have ever been reported.

Animals↗
PubMed2001

Heart versus reason in condom use: implicit versus explicit attitudinal predictors of sexual behavior.

We test the hypothesis that explicit and implicit measures of attitudes would differentially predict deliberate versus spontaneous behavior in the domain of condom use. Students completed explicit attitudinal and thought-listing measures about using condoms and implicit measures using attitude priming and Implicit Association Test (IAT) procedures. An attitude IAT measured the association between condom images and affective images; a self-identity IAT measured association of condoms with the self. We predicted and found that condom use with main partners was predicted by explicit measures but not implicit measures; the opposite was true for condom use with casual partners. Although the attitude priming measure was not positively correlated with casual condom use, the IATs were. The patterns of relations, however, were unexpectedly complex, due to a strong decrease in IAT effects over time, and different IATs assessing unique attitudinal dimensions.

Adult↗
PubMed2001

Theories of reasoned action and planned behavior as models of condom use: a meta-analysis.

To examine how well the theories of reasoned action and planned behavior predict condom use, the authors synthesized 96 data sets (N = 22,594) containing associations between the models' key variables. Consistent with the theory of reasoned action's predictions, (a) condom use was related to intentions (weighted mean r. = .45), (b) intentions were based on attitudes (r. = .58) and subjective norms (r. = .39), and (c) attitudes were associated with behavioral beliefs (r. = .56) and norms were associated with normative beliefs (r. = .46). Consistent with the theory of planned behavior's predictions, perceived behavioral control was related to condom use intentions (r. = .45) and condom use (r. = .25), but in contrast to the theory, it did not contribute significantly to condom use. The strength of these associations, however, was influenced by the consideration of past behavior. Implications of these results for HIV prevention efforts are discussed.

Attitude↗
PubMed2001

Conducting meta-analyses of HIV prevention literatures from a theory-testing perspective.

Using illustrations from HIV prevention research, the current article advocates approaching meta-analysis as a theory-testing scientific method rather than as merely a set of rules for quantitative analysis. Like other scientific methods, meta-analysis has central concerns with internal, external, and construct validity. The focus of a meta-analysis should only rarely be merely describing the effects of health promotion, but rather should be on understanding and explaining phenomena and the processes underlying them. The methodological decisions meta-analysts make in conducting reviews should be guided by a consideration of the underlying goals of the review (e.g., simply effect size estimation or, preferably theory testing). From the advocated perspective that a health behavior meta-analyst should test theory, the authors present a number of issues to be considered during the conduct of meta-analyses.

HIV Infections↗
PubMed2000

An evaluation of the toxicity of contaminated sediments from Waukegan Harbor, Illinois, following remediation.

Waukegan Harbor in Illinois was designated as a Great Lakes Area of Concern due to high concentrations of sediment-associated polychlorinated biphenyls (PCBs). The objective of this study was to evaluate the toxicity of 20 sediment samples collected after remediation (primarily dredging) of Waukegan Harbor for PCBs. A 42-day whole sediment toxicity test with the amphipod Hyalella azteca (28-day sediment exposure followed by a 14-day reproductive phase) and sediment toxicity tests with Microtox(R) were conducted to evaluate sediments from Waukegan Harbor. Endpoints measured were survival, growth, and reproduction (amphipods) and luminescent light emission (bacteria). Survival of amphipods was significantly reduced in 6 of the 20 sediment samples relative to the control. Growth of amphipods (either length or weight) was significantly reduced relative to the control in all samples. However, reproduction of amphipods identified only two samples as toxic relative to the control. The Microtox basic test, conducted with organic extracts of sediments identified only one site as toxic. In contrast, the Microtox solid-phase test identified about 50% of the samples as toxic. A significant negative correlation was observed between reproduction and the concentration of three polynuclear aromatic hydrocarbons (PAHs) normalized to total organic carbon. Sediment chemistry and toxicity data were evaluated using sediment quality guidelines (consensus-based probable effect concentrations, PECs). Results of these analyses indicate that sediment samples from Waukegan Harbor were toxic to H. azteca contaminated at similar contaminant concentrations as sediment samples that were toxic to H. azteca from other areas of the United States. The relationship between PECs and the observed toxicity was not as strong for the Microtox test. The results of this study indicate that the first phase of sediment remediation in Waukegan Harbor successfully lowered concentrations of PCBs at the site. Though the sediments were generally not lethal, there were still sublethal effects of contaminants in sediments at this site observed on amphipods in long-term exposures (associated with elevated concentrations of metals, PCBs, and PAHs).

Animals↗
PubMed2000

Highly unsaturated (n-3) fatty acids, but not alpha-linolenic, conjugated linoleic or gamma-linolenic acids, reduce tumorigenesis in Apc(Min/+) mice.

We showed previously that dietary eicosapentaenoic acid [EPA, 20:5(n-3)] is antitumorigenic in the APC:(Min/+) mouse, a genetic model of intestinal tumorigenesis. Only a few studies have evaluated the effects of dietary fatty acids, including EPA and docosahexaenoic acid [DHA, 22:6(n-3)], in this animal model and none have evaluated the previously touted antitumorigenicity of alpha-linolenic acid [ALA, 18:3(n-3)], conjugated linoleic acid [CLA, 77% 18:2(n-7)], or gamma-linolenic acid [GLA, 18:3(n-6)]. Stearidonic acid [SDA, 18:4(n-3)], the Delta6-desaturase product of ALA, which is readily metabolized to EPA, has not been evaluated previously for antitumorigenic efficacy. This study was undertaken to evaluate the antitumorigenicity of these dietary fatty acids (ALA, SDA, EPA, DHA, CLA and GLA) compared with oleic acid [OA, 18:1(n-9)] at a level of 3 g/100 g in the diets of APC:(Min/+) mice and to determine whether any alterations in tumorigenesis correspond to alterations in prostaglandin biosynthesis. Tumor multiplicity was significantly lower by approximately 50% in mice fed SDA or EPA compared with controls, whereas less pronounced effects were observed in mice fed DHA (P: = 0.15). ALA, CLA and GLA were ineffective at the dose tested. Although lower tumor numbers coincided with significantly lower prostaglandin levels in SDA- and EPA-fed mice, ALA and DHA supplementation resulted in equally low prostaglandin levels, despite proving less efficacious with regard to tumor number. Prostaglandin levels did not differ significantly in the CLA and GLA groups compared with controls. These results suggest that SDA and EPA attenuate tumorigenesis in this model and that this effect may be related in part to alterations in prostaglandin biosynthesis.

6-Ketoprostaglandin F1 alpha↗
PubMed1999

Leakage associated with single or multiple increment backfill with the Obtura II gutta-percha system.

The purpose of this in vitro study was to compare dye leakage between canals backfilled in a single increment and canals backfilled in multiple increments using the Obtura II system with two different sealers. Sixty extracted single canal teeth were decoronated, cleaned, and shaped. After master cone fit and placement of either Roth 801 or AH26 sealers, the canals were down-packed to 4 mm from working length. The teeth were then divided into 4 groups of 15: group 1--Roth 801 sealer with 1 increment of Obtura II back-fill; group 2--Roth 801 sealer backfilled in 4- to 5-mm increments; group 3--AH26 sealer with 1 increment of backfill; and group 4--AH26 sealer backfilled in 4- to 5-mm increments. After sealer set, the teeth were apicected 5 mm from working length. The apices were discarded. The coronal segments were coated with two layers of fingernail polish, except for the resected apical end. The teeth were immersed in Pelikan ink for 5 days. The teeth were then decalcified, dehydrated, and rendered transparent in methylsalicylate. Dye penetration was measured on four surfaces of each root. The mean measurements of each tooth were averaged for each group. Leakage of group 1 was 6.69; group 2, 5.39; group 3, 5.71; and group 4, 5.02. Differences were not statistically significant (p > 0.05). This study suggests that it may be clinically acceptable to backfill canals up to 10 mm in a single increment using sealer and the Obtura II gutta-percha system.

Analysis of Variance↗
PubMed1999

beta-Hemolytic streptococci and other beta-hemolytic organisms in apical periodontitis and severe marginal periodontitis.

Thirteen teeth with necrotic pulps and apical periodontitis and nine severe periodontal pockets were cultured for presence of beta-hemolytic streptococci and other beta-hemolytic organisms. Samples were dispersed and plated on two non-selective and one selective growth media and incubated anaerobically and in 10% CO2 in air. A total of 59 beta-hemolytic colonies were purified and identified. Eight beta-hemolytic streptococcal isolates were obtained from three of the severe marginal periodontitis sites. All were identified as belonging to the Streptococcus sanguis group. No beta-hemolytic streptococci were detected in apical periodontitis samples. Twenty obligately anaerobic isolates were detected, all of which were known periodontal and endodontic pathogens. Isolates from apical periodontitis sites were identified as Propionibacterium acnes, Actinomyces naeslundii, Actionomyces odontolyticus and Peptostreptococcus micros, while severe marginal periodontal sites contained the same species with the addition of Actinomyces viscosus and Actinomyces meyeri. Of 19 staphylococci and micrococci, Staphylococcus epidermidis was the predominant isolate in both apical periodontitis and severe marginal periodontitis sites. However, less commonly known organisms such as Staphylococcus cohnii and Micrococcus sp. were identified in severe marginal periodontitis sites. The isolation of Bacillus sp. (12 isolates) in one severe marginal periodontitis and two apical periodontitis subjects was especially interesting, warranting consideration of this organism as a legitimate isolate and potential pathogen in oral disease.

Bacillus↗
PubMed1999

Effects of HIV counseling and testing on sexual risk behavior: a meta-analytic review of published research, 1985-1997.

OBJECTIVES: This study examined whether HIV counseling and testing leads to reductions in sexual risk behavior. METHODS: The meta-analysis included 27 published studies that provided sexual behavior outcome data, assessed behavior before and after counseling and testing, and provided details sufficient for the calculation of effect sizes. The studies involved 19,597 participants. RESULTS: After counseling and testing, HIV-positive participants and HIV-serodiscordant couples reduced unprotected intercourse and increased condom use more than HIV-negative and untested participants. HIV-negative participants did not modify their behavior more than untested participants. Participants' age, volition for testing, and injection drug use treatment status, as well as the sample seroprevalence and length of the follow-up, explained the variance in results. CONCLUSIONS: HIV counseling and testing appears to provide an effective means of secondary prevention for HIV-positive individuals but, as conducted in the reviewed studies, is not an effective primary prevention strategy for uninfected participants. Theory-driven research with attention given to the context of testing is needed to further explicate the determinants of behavior change resulting from HIV counseling and testing, and the effectiveness of specific counseling approaches.

AIDS Serodiagnosis↗
PubMed1997

Enhancing motivation to reduce the risk of HIV infection for economically disadvantaged urban women.

This research evaluated a motivation-based HIV risk reduction intervention for economically disadvantaged urban women. Participants completed a survey that assessed HIV-related knowledge, risk perceptions, behavioral intentions, sexual communication, substance use, and risk behavior. A total of 102 at-risk women (76% African American) were randomly assigned to either the risk reduction intervention or to a waiting list. Women were reassessed at 3 and 12 weeks. Results indicated that treated women increased their knowledge and risk awareness, strengthened their intentions to adopt safer sexual practices, communicated their intentions with partners, reduced substance use proximal to sexual activities, and engaged in fewer acts of unprotected vaginal intercourse. These effects were observed immediately, and most were maintained at follow-up.

Adolescent↗
PubMed1997

The self-reference effect in memory: a meta-analysis.

In this review, the authors examine the basis for the mnemonic superiority that results from relating material to the self. A meta-analysis confirms the expected self-reference effect (SRE) in memory, with self-referent encoding strategies yielding superior memory relative to both semantic and other-referent encoding strategies. Consistent with theory and research that suggest self-reference (SR) produces both organized and elaborate processing, the SRE was smaller (a) when SR is compared with other-reference (OR) rather than semantic encoding and (b) when the comparison tasks promote both organization and elaboration. Thus, the SRE appears to result primarily because the self is a well-developed and often-used construct that promotes elaboration and organization of encoded information. The authors discuss the implications of these and other findings for theories of the SRE and for future research.

Adult↗
PubMed1996

Effectiveness of yohimbine in the treatment of erectile disorder: four meta-analytic integrations.

The results of four independent yet convergent meta-analyses to examine the efficacy of yohimbine in the treatment of erectile disorder are reported. These meta-analyses integrated data from (i) controlled clinical trials of yohimbine (when used alone), (ii) uncontrolled trials examining yohimbine (alone), (iii) controlled trials of yohimbine when used in combination with other drugs, and (iv) uncontrolled trials of yohimbine plus other drugs. Results document a consistent tendency for yohimbine, and for other medications containing yohimbine, to enhance erectile functioning relative to placebo. We also identify methodological and reporting difficulties that characterize much of the literature.

Alkaloids↗
PubMed1996

Interpersonal contact and acceptance of persons with psychiatric disorders: a research synthesis.

This meta-analytic review predicted and confirmed that interpersonal contact between mental health employees or students and persons diagnosed with psychiatric disorders is associated with improved attitudes toward the latter group. As also predicted, the amount of attitude change was found to be smaller, although still significant, when the evaluative measure described a group of the "mentally ill" rather than specific individuals, and when the respondents were mental health employees rather than students. Contrary to predictions, contact interventions of longer duration were not associated with greater attitude changes. It is concluded that contact interventions occurring in mental health settings are effective in promoting attitude changes toward persons with psychiatric disorders, and methodological refinements that should strengthen the effectiveness of future contact interventions are outlined.

Humans↗
PubMed1996

Elevated blood pressure and personality: a meta-analytic review.

A meta-analysis of 295 relevant effect sizes obtained from 25,469 participants confirmed expectations that elevated blood pressure (BP) and essential hypertension (EH) would be associated with lower affect expression but with more negative affectivity and defensiveness. The strongest associations occurred for defensiveness and measures of anger and affect expression linked to an interpersonal context(s). However, a number of other factors also were found to moderate associations of BP with personality measures, including awareness of BP status, gender, occupation, and diastolic versus systolic BP assessment. Given these moderators, the authors conclude that a traditional view of personality causing EH is untenable and that, not incorporating multifactorial, synergistic approaches is likely to obscure associations of personality-behavior with EH.

Adult↗
PubMed1988

Attitudes toward older and younger adults: a meta-analysis.

Attitudes toward the elderly have been examined in a number of empirical studies, yet the question of whether the elderly are viewed more negatively than younger persons has not been resolved. A meta-analysis of the literature was conducted to examine this question; results demonstrated that attitudes toward the elderly are more negative than attitudes toward younger people. However, smaller differences between the evaluations of elderly and younger targets were found when (a) the study used measures of personality traits (compared with measures of competence), (b) there were a larger number of dependent measures included in the effect size, (c) specific information was provided about the target person (compared with when a general target such as old person was used), and (d) a between-subjects design (compared with a within-subjects design) was used. These results support Lutsky's (1981) conclusion that age, in and of itself, seems to be less important in determining attitudes toward the elderly than other types of information. The methodological limitations within the literature and a need to consider multiple components of attitudes toward older individuals are discussed.

Adult↗
PubMed1984

Impact of an oil field effluent on microbial activities in a Wyoming river.

The survival, functions, and physiological diversity of autochthonous sediment microbiota were examined in situ at five stations along the Little Popo Agie River, WY; one station above, one at, and three below a discharge point for oil wastewater from Union Oil Company's Dallas Field. Below the oil wastewater discharge point there were increases in electron-transport activity, carbon dioxide production, and microbial populations of heterotrophs, ammonifiers, hexadecane degraders, starch hydrolyzers, protein hydrolyzers, and sulfate reducers. At a station 1420 m below the discharge point, however, overall sediment microbial activities and all of the physiological groups of bacteria, except hexadecane-degrading microbiota, were at levels comparable with those at the control station above the discharge point. Similarly, mineralization of glucose, amino acids, hexanoic acid, and hexadecane was elevated at stations directly below the discharge point, but appeared to subside rapidly. Xenobiotic biodegradation potential of the sediments varied with the chemical and the sample location and was not directly related to oil residue levels in the sediment. Microorganisms thus appeared to maintain physiological diversity and increased in numbers and activity in a riverine environment that contained petroleum hydrocarbon concentrations known to be deleterious to freshwater fish and macrobenthic communities.

Alkanes↗