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PubMed2001

The variation in slope of concentration-effect relationships.

Implementing the variation within populations in ecological modeling of risk and effects of toxicants could contribute to a more sophisticated way of modeling. To give insight into the magnitude and spread in sensitivity within test populations the variation in sensitivity of individuals expressed as the slope of a concentration-effect curve (Sm) within more than 300 test populations from toxicity tests with 36 species and 116 substances is analyzed. The overall average variation from this study is 0.65 (Sm) and corresponds to an EC50/EC5 ratio of 2.9. The mode of action is often suggested as an explanation for the different slopes of concentration-effect curves. For metals, indeed, significant different median slope values are observed compared with organic substances. However, within the group of organic substances no distinction between the slope values of narcotic substances and substances with a specific mode of action could be made. Between species groups, significant differences in the amount of variation could be demonstrated. The median slopes for all toxicants within the data set of 96-h tests specified for fishes and mollusks are significantly steeper (median slopes of 0.38 and 0.37, respectively) than those for algae and crustaceans (1.2 and 0.72, respectively). Experimental factors that might explain these differences are discussed. The results from this study provide insight into the variation within a test population and can be used to estimate sensitivity parameters for risk and effect modeling.

Animals↗
PubMed1999

The effectiveness of vitamin C in preventing and relieving the symptoms of virus-induced respiratory infections.

BACKGROUND: An ever increasing demand to evaluate the effect of dietary supplements on specific health conditions by use of a "significant scientific" standard has prompted the publication of this study. OBJECTIVE: To study the effect of megadose Vitamin C in preventing and relieving cold and flu symptoms in a test group compared with a control group. DESIGN: Prospective, controlled study of students in a technical training facility. SUBJECTS: A total of 463 students ranging in age from 18 to 32 years made up the control group. A total of 252 students ranging in age from 18 to 30 years made up the experimental or test group. METHOD: Investigators tracked the number of reports of cold and flu symptoms among the 1991 test population of the facility compared with the reports of like symptoms among the 1990 control population. Those in the control population reporting symptoms were treated with pain relievers and decongestants, whereas those in the test population reporting symptoms were treated with hourly doses of 1000 mg of Vitamin C for the first 6 hours and then 3 times daily thereafter. Those not reporting symptoms in the test group were also administered 1000-mg doses 3 times daily. RESULTS: Overall, reported flu and cold symptoms in the test group decreased 85% compared with the control group after the administration of megadose Vitamin C. CONCLUSION: Vitamin C in megadoses administered before or after the appearance of cold and flu symptoms relieved and prevented the symptoms in the test population compared with the control group.

Adolescent↗
PubMed1998

[Differentiated contact allergy lists serve in quality improvement].

Through cooperation between the German Contact Dermatitis Research Group (DKG) and the Information Network of Departments of Dermatology (IVDK), results of standardized patch tests performed by the participating centres are centrally recorded in Germany. For this study, data from 24 departments of dermatology (19678 patients) were evaluated retrospectively and separately for 1995 and 1996. With decreasing frequency, nickel, fragrance mix, balsam of peru, and thimerosal yielded positive reactions most often; surprisingly high numbers of positive reactions were also seen with amerchol L-101 and palladium. Differentiated lists of allergens were compiled for 1995, referring to subgroups of patients (defined by gender, age, localization of eczema, geographical region, occupation, sensitization) and particular problems. In men, percentages of positive reactions were markedly lower for nickel, fragrance mix and balsam of peru than in women. Younger patients reacted more often to thimerosal and older ones to topical medical preparations. Medical allergens were also often positive in patients with leg eczema, whereas occupational allergens were found more frequently in patients with hand eczema. A comparison of positive reactions obtained in distinct geographical regions was problematic because of differences between test populations. The spectrum of allergens found in office workers was similar to that of the whole test population. Patients with positive reactions to nickel and fragrance mix had more positive reactions to unrelated allergens than the total test population. Sex- and age-adjusted frequencies of sensitization revealed a decrease in reactions to nickel and an increase in reactions to mercury allergens from 1995 to 1996. The clinical relevance of mercury reactions was often not apparent. Differentiated lists of allergens can be used to improve the quality of diagnostic and prophylactic procedures in allergic contact dermatitis.

Adolescent↗
PubMed1984

Factors influencing the regularity of meditation practice in a clinical population.

Tests were administered to out-patients before learning meditation. High pre-test scores on sensitization, suggestibility, introversion, neuroticism and perceived symptomatology predicted a low practice frequency. Gender, expectations, credibility, locus of control and self-esteem were unrelated to outcome. By two years, 54 per cent had stopped meditating. Meditation appeared to be more rewarding for subjects with milder complaints.

Adult↗
PubMed1983

Paraoxonase phenotype distribution in Canadian Indian and Inuit populations.

Test objects were the sera of 57 North American Indian and 67 Inuit subjects. The paraoxon-hydrolyzing activity, a, was determined, as well as the paraoxonase-phenotyping ratio, c/b, a ratio designating enzyme activation by Na+ in the presence of Ca2+. The values of c/b were clearly bimodally distributed. Location of the modes and of the antimodal gap were in perfect agreement with the results previously obtained on Caucasian sera. This allowed us to retain the criterion which had been already established in the study of Caucasians, i.e., c/b less than 1.5 = "low-activity" phenotype, and c/b greater than 1.5 = "high-activity" phenotype. The proportions of individuals in each mode differed, however. In Caucasians, the frequency of the "low-activity" phenotype had been estimated as 51.2%. In Indians and Inuits, it was 7.0% and 6.0%, respectively. Independent of phenotype, Indian and Inuit sera displayed lower paraoxon-hydrolyzing activity than did Caucasian sera.

Aryldialkylphosphatase↗
PubMed1986

The presence of anti-HBc in a dental school patient population.

Testing for three serum markers in screening for hepatitis B disclosed 34 of 292 patients testing positive to anti-HBc. Responses to the medical history alone disclosed only one patient with a history of hepatitis. Seroanalysis, plus a complete history, yields the most reliable results.

Adolescent↗
PubMed1985

The prevention of cervical cancer: the place of the cytological smear test.

Population screening by cervical cytology, if properly carried out, can substantially reduce mortality and morbidity due to cancer of the cervix. The technique of smear taking requires careful attention as well as maintenance of high standards in cytology screening laboratories. Patients with abnormal cytology are at high risk for cervical cancer and should be managed appropriately and followed up indefinitely. The terminology used in cytology reporting is discussed.

Adenocarcinoma↗
PubMed2001

Results of a quality of life questionnaire in a patch test clinic population.

There has been increasing interest in quality of life outcomes, but there has been little reported on this topic for individuals with contact dermatitis. The objectives of this study were (i) to pilot a dermatology-specific quality of life instrument to assess its acceptability in a patch test clinic population, (ii) to see the effects of contact dermatitis on the patients' lives and (iii) to determine what factors may influence quality of life outcomes in this population. A dermatology-specific quality of life instrument was modified and used for 339 patients undergoing patch testing in a contact dermatitis clinic. The most common effect was pain or itching in 61%. Approximately 1/3 noted embarrassment, interference with work, or sleep disturbance. Other concerns were reported by less than 25% of the population. On multivariate analysis, the key factor influencing most outcomes was hand involvement. The instrument was well accepted by the clinic population and is now being used in a prospective study of outcomes. In the population assessed, it demonstrated the effects of disease. Analysis suggests that a key factor influencing these quality of life outcomes is hand involvement.

Activities of Daily Living↗
PubMed1999

Effect of process temperature, pH and suspended solids content upon pasteurization of a model agricultural waste during thermophilic aerobic digestion.

Thermophilic aerobic digestion(TAD), or liquid composting, is a versatile new process for the treatment and stabilization of high strength wastes of liquid or, perhaps more importantly, slurry consistency. The pattern of inactivation of various pathogenic and indicator organisms was studied using batch digestions under conditions that may be expected to be found in full-scale TAD processes. Rapid inactivation of test populations occurred within the first 10 min from the start of digestion. The inactivation rate was slightly lower when digestions were conducted below 60 degrees C. In some instances, a 'tail' was apparent, possibly indicating the survival of relatively resistant sub-populations particularly in the case of Serratia marcescens and Enterococcus faecalis, or of clumping or attachment of cells to particulate materials. The effect of pH on the inactivation of the test populations depended on the temperature of digestion, but varied with the test population. At 55 degrees C Escherichia coli was more sensitive to temperature effects at pH 7 than at pH 8, but was more sensitive at pH 8, 60 degrees C. The reverse was the case at 60 degrees C for Ent. faecalis. An increase in the solid content of the digesting waste caused a progressive increase in the protection of test organisms from thermal inactivation. Challenging a TAD process with test strains allows (via estimation of D-values) a quantification of the cidal effects of such processes, with a view to manipulating process variables to enhance such effects.

Agriculture↗
PubMed2006

Accuracy of dual-source CT coronary angiography: First experience in a high pre-test probability population without heart rate control.

The aim of this study was to assess the diagnostic accuracy of dual-source computed tomography (DSCT) for evaluation of coronary artery disease (CAD) in a population with extensive coronary calcifications without heart rate control. Thirty patients (24 male, 6 female, mean age 63.1+/-11.3 years) with a high pre-test probability of CAD underwent DSCT coronary angiography and invasive coronary angiography (ICA) within 14+/-9 days. No beta-blockers were administered prior to the scan. Two readers independently assessed image quality of all coronary segments with a diameter > or =1.5 mm using a four-point score (1: excellent to 4: not assessable) and qualitatively assessed significant stenoses as narrowing of the luminal diameter >50%. Causes of false-positive (FP) and false-negative (FN) ratings were assigned to calcifications or motion artifacts. ICA was considered the standard of reference. Mean body mass index was 28.3+/-3.9 kg/m2 (range 22.4-36.3 kg/m2), mean heart rate during CT was 70.3+/-14.2 bpm (range 47-102 bpm), and mean Agatston score was 821+/-904 (range 0-3,110). Image quality was diagnostic (scores 1-3) in 98.6% (414/420) of segments (mean image quality score 1.68+/-0.75); six segments in three patients were considered not assessable (1.4%). DSCT correctly identified 54 of 56 significant coronary stenoses. Severe calcifications accounted for false ratings in nine segments (eight FP/one FN) and motion artifacts in two segments (one FP/one FN). Overall sensitivity, specificity, positive and negative predictive value for evaluating CAD were 96.4, 97.5, 85.7, and 99.4%, respectively. First experience indicates that DSCT coronary angiography provides high diagnostic accuracy for assessment of CAD in a high pre-test probability population with extensive coronary calcifications and without heart rate control.

Adult↗
PubMed1995

A population genetic test of selection at the molecular level.

The role of natural selection in molecular evolution has been inferred primarily by rejection of null hypotheses based on neutral theory, rather than by acceptance of specific predictions based on selection. In this report, a population genetic test of a specific prediction for selection on DNA polymorphism is presented. Pyrethroid insecticide use constitutes an experiment for which form of selection and molecular target (voltage-gated sodium channels) are both known. As predicted, differential pyrethroid selection on tobacco budworm populations generated significant geographic heterogeneity in sodium channel marker allele frequencies, compared with arbitrary loci.

Alleles↗
PubMedDate not supplied

Enumeration procedure for monitoring test microbe populations on inoculated carriers in AOAC use-dilution methods.

The AOAC Use-Dilution methods do not provide procedures to enumerate the test microbe on stainless steel carriers (penicylinders) or guidance on the expected target populations of the test microbe (i.e., a performance standard). This report describes the procedures used by the U.S. Environmental Protection Agency to enumerate the test microbe (carrier counts) associated with conducting the Use-Dilution method with Staphylococcus aureus (Method 955.15) and Pseudomonas aeruginosa (Method 964.02) and the examination of historical data. The carrier count procedure involves the random selection of carriers, shearing bacterial cells from the carrier surface through sonication, and plating of serially diluted inoculum on trypticase soy agar. For each Use-Dilution test conducted, the official AOAC method was strictly followed for carrier preparation, culture initiation, test culture preparation, and carrier inoculation steps. Carrier count data from 78 Use-Dilution tests conducted over a 6-year period were compiled and analyzed. A mean carrier count of 6.6 logs (approximately 4.0 x 10(6) colony-forming units/carrier) was calculated for both S. aureus and P. aeruginosa. Of the mean values, 95% fell within +/- 2 repeatability standard deviations. The enumeration procedure and target carrier counts are desirable for standardizing the Use-Dilution methods, increasing their reproducibility, and ensuring the quality of the data.

Colony Count, Microbial↗
PubMed1998

HIV testing among populations at risk for HIV infection--nine states, November 1995-December 1996.

Extending acquired immunodeficiency syndrome (AIDS) case surveillance systems to include confidential (name-based) reporting of human immunodeficiency virus (HIV) infections provides data representing recent HIV transmission patterns. These data may improve the ability of public health agencies to plan and evaluate HIV prevention and treatment services. Thirty-two states conduct name-based HIV infection case surveillance as an extension of AIDS case surveillance, and such surveillance is being considered in other states. Some community representatives and public health officials, however, are concerned that HIV infection surveillance may deter some at-risk persons from seeking HIV testing. This report describes the results of a survey conducted to assess deterrents to HIV testing in populations at risk for HIV infection during 1995 and 1996. The findings indicate that in these populations knowledge of state HIV reporting policies was low, and fear of a positive HIV test result and a lack of perceived risk for HIV infection were the most common deterrents to testing in all risk groups. However, untested men who have sex with men (MSM) who resided in states with name-based reporting cited concerns about reporting as a reason they had not tested more often than untested MSM in states without name-based reporting.

AIDS Serodiagnosis↗
PubMed1999

Are there temporarily non-infectious dauer stages in entomopathogenic nematode populations: a test of the phased infectivity hypothesis.

Many studies of entomopathogenic nematodes (Heterorhabditidae and Steinernematidae) have reported that only a small proportion (typically < 40%) of infective stages (dauers), even under apparently ideal conditions, actually infect a host. The 'phased infectivity hypothesis' is most frequently invoked to explain this pattern of low infection with entomopathogenic nematodes. It proposes that at a given point in time not all individuals are infectious i.e. infectiousness is delayed in some individuals. We tested experimentally several predictions based on this hypothesis. Specifically, if phased infectivity occurs, we should be able to expose dauers to increasing numbers of potential hosts until dauers no longer infect and still be able to recover viable dauers. These recovered dauers which did not infect should be infectious at some later point in time. However, our results do not support the phased infectivity hypothesis for 3 species of Steinernema: most dauers could be recovered in one sampling round when provided with sufficient suitable hosts. In contrast, Heterorhabditis bacteriophora frequently did not infect all available hosts, and infectious dauers were recovered in subsequent sampling rounds. This result is more consistent with the phased infectivity hypotheses, but further research is needed before we can be more confident in the hypothesis. For all species tested, the number of available hosts influenced population levels of nematode infectivity. This suggests that the infection status of hosts can influence whether a dauer infects. Our results indicate that phased infectivity is not a common phenomenon in entomopathogenic nematode dauers, despite the widespread acceptance of this hypothesis.

Animals↗
PubMed2003

Biochemical detection of pyrethroid resistance mechanisms in Anopheles minimus in Thailand.

Enzyme-based metabolic mechanisms of insecticide resistance were investigated, comparing a deltamethrin-susceptible parent stock and resistant colonies of Anopheles minimus species A using biochemical assays. The control parent colony was determined susceptible to the diagnostic lethal concentration of deltamethrin (0.05%), whereas the 6 resistant test populations at selected 4, 8, 12, 14, 16, and 18 filial generations (F4, F8, F12, F16, and F18) demonstrated varying levels of tolerance/resistance to deltamethrin. Expression of levels of non-specific esterases, monooxygenases, and glutathione S-transferases (GSTs) were measured. Results indicated that monooxygenase activity was consistently elevated in resistant-selected test populations compared to the parent colony and increased as resistance intensified from F8 to F18. There was a 5-fold increase in monooxygenase in the F18 generation compared to the parental stock. Fluctuations in alpha and beta-esterase activity, measured by hydrolysis of alpha and beta-naphthylpropionate, provided no conclusive evidence of an association with pyrethroid resistance in this mosquito species. GSTs were not elevated in the 6 resistant test populations. Based on our results, it appears likely that the development of physiological resistance to deltamethrin in laboratory, resistant-selected generations of An. minimus is primarily associated with increased detoxification by over-expression of monooxygenases. The oxidases are the major contributors to pyrethroid resistance and the importance of kdr has yet to be convincingly determined. This finding represents the first report from Thailand of this metabolic mechanism of resistance in anophelines.

Animals↗
PubMed1998

Factors associated with non-use of Pap test. A population survey.

BACKGROUND: Cervical cancer is the most important cancer in Mexican women. Early detection is possible by means of the Papanicolaou (Pap) test; however, the coverage in Mexico is low. METHODS: A cross-sectional survey was carried out in a representative sample of women from the Tlalpan area of Mexico City. Social, reproductive and health care factors associated with the lack of use of the Pap test with respect to adequate use and misuse were identified. Both bivariate and logistic regression analyses were used for the adjustment of variables. RESULTS: Of 1,215 women studied, 22.5% had never had a Pap smear, 42% had misused the test (< 90% of triennial performance), and 35.5% had adequately used the test (> or = 90% of triennial performance). The main factors related to the lack of use were the following: not knowing about the Pap test (ORa = 35.16, 95% C.I. = 17.4-70.9); having fewer than 6 years of education (ORa = 4.5, 95% C.I. = 2.5-8.4); women younger than 30 years of age (ORa = 3.4 95% C.I. = 2.3-5.1); use of contraceptives (ORa = 0.4, 95% C.I. = 0.2-0.8); history of sexually transmitted diseases (ORa = 0.3, 95% C.I. = 0.1-0.8), and the principal informant about the Pap test, i.e., the health services personnel (ORa = 0.02, 95% C.I. = 0.0008-0.05). CONCLUSIONS: The lack of use and the misuse of Pap smears vary importantly among the different social and reproductive factors. But the principal reasons for lack of use were not knowing about the Pap test and a low educational level. We propose a greater diffusion on the benefits of the test in the Mexican population, through massive means of communication and health services.

Adult↗
PubMed1985

Influence of genetic composition of test-animal populations on chronic toxicity studies used for risk estimation.

A lifespan exposure of mice to benzidine dihydrochloride was conducted for 33 m using both sexes of two populations of mice with the same gene pool. One population was the genetically homogeneous F1 hybrid produced by crossing BALB/cStCrlC3Hf/Nctr males with C57BL/6jfC3Hf/Nctr females. The second population consisted of genetically heterogenous monohybrid cross (MC) offspring produced by mating the F1 hybrids inter se. Data comparisons were made to determine if gene distribution among members of a population affects the response to a toxic insult. Endpoints tested consisted of mortality, liver tumor incidence and time of tumor onset, mortality from reticulum-cell sarcoma, and body weights. In most instances it was noted that among animals not dosed (controls), the F1 population had lower background incidence of lesions and lived longer than the MC population. However, among the dosed animals, the F1 mice were generally more susceptible to the toxic agent and developed higher incidences of the chemically induced lesions than did the MC population. The F1 hybrid population gave a more conservative estimate of risk than did the MC population. The calculation of the liver tumor risk for these two populations showed that lifespan exposure to benzidine would be predicted to result in a larger number (higher risk) when using the F1 data. A 4.5-fold difference in the toxic response was observed between the F1 females and the MC males. This emphasizes the importance of gene distribution in risk estimation studies.

Animals↗