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PubMed2005

Avoidance bio-assays may help to test the ecological significance of soil pollution.

We measured the short-term (100 min) avoidance of a soil heavily polluted by hydrocarbons by the soil springtail Folsomia candida, at six rates of dilution in a control, unpolluted soil. We compared the results with those of long-term (40-day) population tests. Five strains were compared, of varying geographical and ecological origin. When pure, the polluted soil was lethal in the long-term and avoided in the short-term by all strains. Avoidance tests, but not population tests, were able to discriminate between strains. Avoidance thresholds differed among strains. Two ecological consequences of the results were discussed: (i) toxic compounds may kill soil animals or deprive them from food, resulting in death of populations, (ii) pollution spots can be locally deprived of fauna because of escape movements of soil animals. Advantages and limitations of the method have been listed, together with proposals for their wider use in soil ecology and ecotoxicology.

Animals↗
PubMed2005

[Genetic diversity of Hepatacodium miconioides natural populations in Zhejiang Province].

Hepatacodium miconioides is the Class II protected plant species in China. This paper studied the genetic diversity and differentiation of its nine natural populations in Zhejiang Province by using random amplified polymorphic DNA (RAPD) technique. Twelve random primers were selected in the amplification, and 164 repetitive loci were produced. The percentage of polymorphic loci in each H. miconioides population ranged from 14.60% to 27.44%, with an average of 20.73%. Among the test populations, Kuochangshan population had the highest percentage of polymorphic loci, Simingshan population took the second place, and Guanyinping population had the lowest one. As estimated by Shannon index, the genetic diversity within H. miconioides populations accounted for 27.28% of the total genetic diversity, while that among H. miconioides populations accounted for 72.72%. The genetic differentiation among H. miconioides populations as estimated by Nei index was 0.7157. The genetic differentiation estimated by Nei index was generally consistent with that estimated by Shannon index, i.e., the genetic differentiation among populations was relatively high, but that within populations was relatively low. The gene flow among H. miconioides populations was relatively low (0.1987), and the genetic similarity ranged from 0.6557 to 0.8119, with an average of 0.7306. The highest genetic distance among populations was 0.4229, while the lowest one was 0.2083. All the results showed that there was a distinct genetic differentiation among H. miconioides populations. The genetic distance matrix of nine test populations was calculated by using the method, and the clustering analysis was made by using the unweighted pair group method with arithmetic mean (UPGMA). The cluster analysis suggested that the nine populations of H. miconioides in Zhejiang Province could be divided into two groups, i.e., eastern Zhejiang group and western Zhejiang group.

Caprifoliaceae↗
PubMed1975

The N2 closing volume test in population studies: sources of variation and reproducibility.

Sources of variation in the nitrogen closing volume test and derived measurements were examined in the results of 13 subjects, each of whom performed 3 sequential trials on 2 occasions 30 to 60 minutes apart, on 2 separate days 1 week apart (156 trials in all). Results were examined to evaluate the relative sensitivity of the various measurements for differences between sujbects and, by implication, their potential value in population studies. Using the ratio of signal (between-subject variance) to noise (within-subject variance) as the criterion, the sensitivities of the ratio of closing volume to vital capacity (CV/VC,%) and the ratio of closing capacity to total lung capacity (CC/TLC,%) were comparable; contrary to expectation, sensitivity decreased rather than increased with side-by-side compared to independent tracing analysis. Comparison of various test schedules showed the greatest sensitivity when the mean of 3 measurements was used, with a single measurement of CV/VC,% being only one-third as sensitive, and a single measurement of CC/TLC,% being one-half as sensitive as the mean. In addition, the validity of the measurements of total lung capacity from nitrogen dilution in a single oxygen breath was confirmed by the demonstration of good agreement with helium dilution values.

Adult↗
PubMed2001

Quantitative similarity-based association tests using population samples.

Although genetic association studies using unrelated individuals may be subject to bias caused by population stratification, alternative methods that are robust to population stratification, such as family-based association designs, may be less powerful. Furthermore, it is often more feasible and less expensive to collect unrelated individuals. Recently, several statistical methods have been proposed for case-control association tests in a structured population; these methods may be robust to population stratification. In the present study, we propose a quantitative similarity-based association test (QSAT) to identify association between a candidate marker and a quantitative trait of interest, through use of unrelated individuals. For the QSAT, we first determine whether two individuals are from the same subpopulation or from different subpopulations, using genotype data at a set of independent markers. We then perform an association test between the candidate marker and the quantitative trait, through incorporation of such information. Simulation results based on either coalescent models or empirical population genetics data show that the QSAT has a correct type I error rate in the presence of population stratification and that the power of the QSAT is higher than that of family-based association designs.

Computer Simulation↗
PubMed2003

[Manifestation of glutathione S-transferase GSTM1 and GSTT1 in female patients with bleomycin-positive chromosome instability].

OBJECTIVES: The purpose of this research is to assess the incidence of gene polymorphisms coding the GSTM1 and GSTT1 enzymes in a population of female patients with chromosome instability. MATERIALS AND METHODS: The PCR method was used to determine the genotype for GSTM1 and GSTT1. The breaks per cell and the percentage of damaged cells were calculated. The separation point used to diagnose chromosome instability in tested females was assumed to be 2.5. RESULTS: In a tested population of 85 females with chromosome instability, the deletion of both the alleles of the GSTT1 gene was observed in 22 females (25% of the group) and deletion of both the alleles of the GSTM1 gene was observed in 42 females (53% of the group). In addition, the incidence of individual genes was calculated for the tested population. The X2 test showed that the differences between the observed and expected values of the tested genes were statistically immaterial, i.e. the likelihood of randomness for these differences exceeded 99%. CONCLUSIONS: No relationship between the manifestation of genotypes for the GSTM1 and GSTT1 glutathione S-transferases and an increased chromosome instability confirmed with the bleomycin test was proven for a population of females with a neoplastic risk.

Adult↗
PubMed1984

Phenotypic basis for a feeding change in an insular population of garter snakes.

Predation on birds, an unusual behavior for the common garter snake (Thamnophis sirtalis), has been observed and documented in an insular garter snake population. Feeding preference tests were performed on naive neonatal snakes and experienced adults from both the island test population and a nearby mainland control population. No significant preference for birds as a prey item was found for either neonates or adults from either population. Therefore, neither a genetic nor an ontogenetic basis for the observed behavior was demonstrable. Birds tainted with a piscine odor, however, elicited a positive feeding response from adult snakes from both geographical sources. We propose that the observed behavior in the field is a result of learning to exploit an abundant, readily available resource already in the predator's repertoire.

Animals↗
PubMed1992

Effect of conventional dental restorative treatment on bacteria in saliva.

Dental caries results from the dissolution of mineralized dental tissues by the metabolic by-products of oral bacteria colonizing the surface of teeth. The principal modality for dealing with this infectious process is through restorative treatment which removes the pathologic tissue and replaces it with a variety of inert materials. The purpose of this study was to evaluate the effect of traditional restorative treatment on select oral bacterial populations. Fifty-two females demonstrating high levels of mutans streptococci (greater than or equal to 2.5 x 10(4) colony forming units (cfu) per ml saliva) with no more than four missing posterior teeth were recruited for this study. Salivary levels of mutans streptococci, lactobacilli, total streptococci, and total cultivable bacteria were evaluated before, during, and after restorative treatment. Initial DMFS scores were established by two standardized examiners using bitewing radiographs and clinical examination, which was conducted under optimal conditions. All restorative treatment was completed by faculty members of the University of Alabama School of Dentistry using treatment plans developed by the DMFS examiners. The participants received a mean of 16.4 restored surfaces, which resulted in significant reductions of all the bacterial populations tested. All microbial populations monitored were predicted to return to their baseline levels within 151 days after restorative treatment in 50% of the participants. This study shows that conventional restorative treatment results in a significant reduction of bacterial populations including those associated with the dental caries process, i.e., mutans streptococci and lactobacilli.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

The concentration of IgD in blood sera of children suffering from dys- or hypogammaglobulinaemia of class A.

6580 children inhabitans of selected region of Lower Silesia and 475 children with recurrent respiratory tract infections as well as 65 children with chronic active hepatitis were tested. IgA level was determined in each case. In the cases where IgA was absent or a low level of this immunoglobulin was found (0.2 g/l) IgD concentration was determined. It was established that the frequency of dysgammaglobulinaemia of class A was 1/731 tested cases in the tested population and 1/119 cases in children with respiratory tract infections and 1/65 tested children with chronic active hepatitis. Hypogammaglobulinaemia of class A was found in 1/365 cases in the tested population and 1/20 cases in children with respiratory tract infections and 2/65 children with chronic aggressive hepatitis. In children with dysgammaglobulinaemia of class A lack of IgD in serum was found in 44% of the cases--however, in hypogammaglobulinaemia IgA lack of IgD in serum was found in 38% of the cases.

Adolescent↗
PubMed1979

Further studies on the compatibility between s. intercalatum from cameroun and zaïre and species of bulinus.

The results from the infection experiments with Schistosoma intercalatum from Cameroun and from Zaïre and the intermediate hosts, belonging to B. forskalii and B. globosus, could be divided into groups according to the degree of compatibility with the schistosomes. This was indicated by the total cercariae production per 100 exposed snails (TCP/100 exp. snails). B. forskalii from Kinshasa, Zaïre were the snails which were most compatible with S. intercalatum from Cameroun, and B. globosus populations tested were refractory. The TCP/100 exposed snails was about 300,000 for the populations of B. forskalii from Kinshasa compared with the low production for B. forskalii from Cameroun of 125,000. B. wrighti from South Arabia produced 155,000 cercariae per 100 exposed snails. B. cernicus from Mauritius could be separated into two types according to the compatibility with S. intercalatum from Cameroun, the TCP/100 exposed snails was 31,000 and 267,000, respectively. B. globosus from Kinshasa, Zaïre, was very compatible with S. intercalatum from Zaïre and the TCP/100 exposed snails was very high, and 300,000. An albino strain of B. globosus from Rhodesia was the most compatible snail having a TCP/100 exposed snails of 2.4 million cercariae. Other strains of B. globosus from Cameroun and Togo were refractory and less susceptible. It was also possible to infect B. africanus and the two tested populations from Kenya and Tanzania, producing 15,000 and 179,000 cercariae per 100 exposed snails, respectively.

Africa↗
PubMedDate not supplied

A unified approach to adjusting association tests for population admixture with arbitrary pedigree structure and arbitrary missing marker information.

A general approach to family-based examinations of association between marker alleles and traits is proposed. The approach is based on computing p values by comparing test statistics for association to their conditional distributions given the minimal sufficient statistic under the null hypothesis for the genetic model, sampling plan and population admixture. The approach can be applied with any test statistic, so any kind of phenotype and multi-allelic markers may be examined, and covariates may be included in analyses. By virtue of the conditioning, the approach results in correct type I error probabilities regardless of population admixture, the true genetic model and the sampling strategy. An algorithm for computing the conditional distributions is described, and the results of the algorithm for configurations of nuclear families are presented. The algorithm is applicable with all pedigree structures and all patterns of missing marker allele information.

Algorithms↗
PubMed2004

A novel Z-score-based method to analyze candidate genes for age-related hearing impairment.

OBJECTIVE: Approximately half of the variance of Age-Related Hearing Impairment (ARHI) is attributable to environmental risk factors, and the other half to genetic factors. None of these genes has ever been identified, but the genes involved in monogenic nonsyndromic hearing impairment are good candidates. Here we define and validate a quantitative trait value for ARHI, correcting for age and gender, to allow the genetic study of ARHI as a quantitative trait. DESIGN: Based on the ISO 7029 standard, we convert audiometric data into a Z-score, an age- and gender-independent value expressing to what extent a person is affected by ARHI. The validity of this approach is checked using a test population of randomly collected subjects. The power to evaluate the contribution of a candidate gene to ARHI is assessed using simulated populations. As an example, one ARHI candidate gene is analyzed. RESULTS: In our test population, Z-scores were normally distributed although the mean did not equal zero. Z-scores were independent of age, and there was no difference between men and women. Power studies using simulated populations indicated that to detect moderate genetic effects, sample sizes of at least 500 random subjects are necessary. CONCLUSION: The Z-score conversion appears to be a valid method to describe to what extent a subject is affected by ARHI, allowing to compare persons from different age and gender. This method can be the basis of future, powerful studies to identify ARHI genes.

Adult↗
PubMed1987

Specificity and sensitivity of objective diagnosis of gastroesophageal reflux disease.

To evaluate the diagnostic value of different tests for gastroesophageal reflux disease, a test population was constructed from 45 patients with symptoms of heartburn and regurgitation with or without esophagitis and 45 healthy subjects, who never experienced heartburn, regurgitation, or swallowing discomfort. The test population underwent esophagoscopy, standard acid reflux test, 24-hour pH monitoring, and manometry of the lower esophageal sphincter. Sensitivity, specificity, positive predictive value, negative predictive value, and the accuracy of the tests and test combinations were calculated. Esophagoscopy had a sensitivity of 62%, that is, only 62% of patients with the disease have evidence of mucosal damage on endoscopy. Manometric measurements of the lower esophageal sphincter had a sensitivity of 84%, a specificity of 89%, and an accuracy of 87%. Twenty-four hour esophageal pH monitoring had a sensitivity, specificity, and accuracy of 96%. The results show that 24-hour pH monitoring can detect gastroesophageal reflux disease with an accuracy of 96% by measuring an increase in esophageal acid exposure. Manometry of the lower esophageal sphincter can detect a mechanically deficient sphincter as a cause of the disease with an accuracy of 87%. The test combination of 24-hour monitoring and motility studies can select patients with an accuracy of 91% who have an increase in esophageal exposure to gastric juice because of a deficient cardia. Antireflux surgery is designed to reduce esophageal exposure to gastric juice in patients with a deficient sphincter by creating a mechanical antireflux mechanism at the cardia. Therefore it is necessary to determine the mechanical status of the sphincter with manometry before surgery in such patients. Thus the indications for antireflux surgery are (1) uncontrolled symptoms of increased esophageal exposure to gastric juice; (2) a documented increase in esophageal exposure to gastric juice by 24-hour pH monitoring; and (3) a mechanically defective sphincter on motility with a pressure of 6 mm Hg or less, an overall length of 2 cm or less, and an abdominal length of 1 cm or less.

Esophagoscopy↗
PubMed1989

Allergic contact dermatitis in children and young adults.

We evaluated the results of a 5-year period of epicutaneous testing in children and teenagers younger than 16 years of age. In an overall-tested population of 2671 persons, 67 were younger than 16 years. In 16 (23.8%) of these 67 children, a positive epicutaneous test was considered to be clinically relevant for the diagnosis allergic contact dermatitis. From the total of 44 positive tests, the most common allergen was nickel sulfate (18%), followed by balsam of Peru, Carba mix, colophony, and fragrance mix (6% each). As our test population consisted of only a few children, no conclusions were drawn in respect to children younger than 10 years. Despite our careful selection of children with allergic contact dermatitis, the prevalence of positive epicutaneous tests was no different than that reported for unselected populations of children.

Adolescent↗
PubMed2000

Human and murine CD4 T cell reactivity to a complex antigen: recognition of the synthetic random polypeptide glatiramer acetate.

The capacity of glatiramer acetate (GA), a random copolymer of alanine, lysine, glutamic acid, and tyrosine to stimulate primary in vitro human and murine T cell proliferation was examined. PBMCs isolated from healthy humans and relapsing remitting multiple sclerosis patients and spleen cells from inbred strains of mice, expressing different H-2 haplotypes, were used as sources of non-GA-primed lymphocytes. GA functioned as a universal Ag, inducing dose-dependent proliferation of all non-GA-primed human and murine T cell populations tested. Moreover, GA stimulated PBMCs derived ex vivo from human cord blood, strongly suggesting that GA can activate both naive and memory T cells. The human T cell proliferative responses to GA were HLA class II DR-restricted by virtue of the ability of anti-class II Ab to inhibit T cell proliferation, and the demonstration that individual GA specific human T cell clones were HLA class II DR-restricted by either restriction element but not both. Furthermore, GA-reactive T cells secreted Th0 cytokines and expressed a diverse repertoire of TCR. Limiting dilution analysis indicated that the T cell precursor frequency among the healthy human adults tested ranged from 1:5,000 to 1:125,000. Given that all of the T cell populations tested were isolated from non-GA-primed donors, it appears that virtually all humans and murine strains contain significant numbers of T cell populations cross-reactive with GA. These findings may explain the recent clinical finding that daily s.c. administration of GA ameliorates the progression of multiple sclerosis.

Adult↗
PubMed1979

[Genetic markers and disease susceptibility (author's transl)].

The HLA system includes several genes and each of them is polymorphic. Several associations between some HLA alleles and the susceptibility to various diseases are already described. Three kinds of associations are reported: [1] a constant association between an HLA allele and a disease whatever the tested population, [2] an association between the HLA allele and a disease varying according to the tested populations, [3] an association probably due to a mutation of metabolic gene closely linked to HLA. These three kinds of associations probably correspond to three different mechanisms.

Alleles↗
PubMed2004

A population-genetic test of founder effects and implications for Ashkenazi Jewish diseases.

A founder effect can account for the presence of an allele at an unusually high frequency in an isolated population if the allele is selectively neutral and if all copies are identical by descent with a copy that either was carried by a founder individual or arose by mutation later. Here, a statistical test of both aspects of the founder-effect hypothesis is developed. The test is performed by a modified version of a program that implements the Slatkin-Bertorelle test of neutrality. The test is applied to several disease-associated alleles found predominantly in Ashkenazi Jews. Despite considerable uncertainty about the demographic history of Ashkenazi Jews and their ancestors, available genetic data are consistent with a founder effect resulting from a severe bottleneck in population size between a.d. 1100 and a.d. 1400 and an earlier bottleneck in a.d. 75, at the beginning of the Jewish Diaspora. The relatively high frequency of alleles causing four different lysosomal storage disorders, including Tay-Sachs disease and Gaucher disease, can be accounted for if the disease-associated alleles are recessive in their effects on reproductive fitness.

Adenomatous Polyposis Coli↗
PubMed2002

Biomarkers in toxicology versus ecological risk assessment.

Toxicity testing of drugs, pesticides, and hazardous compounds has evolved into a battery of standardized tests conducted in a range of surrogate test organisms. The toxicity of these xenobiotics in terms of their LD(50) and LC(50) (Dose or concentration lethal to 50% of the test population), ED(50) and EC(50) (Dose or concentration producing a specified response in 50% of the test population), MATC (Maximum acceptable toxicant concentration), LOEL (Lowest observable effects level), LOEC (Lowest observable effects concentration), NOEL (No observable effects level) or NOEC (No observable effects concentration) is extrapolated to humans and wildlife. Historical failures in the risk assessment process have been largely due to over reliance on regulatory toxicology and an 'assembly line' mentality to toxicology. The importance of toxicokinetics, receptor studies and biomarkers are reviewed, firstly, with reference to toxicological incidences in drug development programmes, and secondly, with reference to improved environmental risk assessment of pesticides and other contaminants. Ecological risk assessments also require multidisciplinary skills to study the entry, distribution, and biological effect and fate of chemicals to fully characterise and understand the potential adverse implications of contamination. Optimum integration of chemical measurements and biomarker responses is a challenge that will lead to an improved understanding of adverse effects and their significance in both human and ecological risk assessment.

Animals↗