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PubMed2006

Analysis of anatoxin-a in biological samples using liquid chromatography with fluorescence detection after solid phase extraction and solid phase microextraction.

Anatoxin-a is a naturally occurring, potent neurotoxin produced by some species of cyanobacteria in freshwaters. This toxin, which is a potential health hazard, especially to animals, has been determined in different biological matrices such as several cyanobacterial cultures and water samples and carps and mussels tissue using a sensitive High Performance Liquid Chromatography with Fluorescence detection method. Sonication was the technique selected for the extraction of intracellular anatoxin-a and solid phase extraction using weak cation exchange was used for the concentration and purification of the samples. 4-Fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) was used to convert anatoxin into a highly fluorescent derivative. Recovery experiments were performed for each type of matrix used in this work, and adequate values were obtained (71-87%). Limits of detection for anatoxin-a were estimated to be in the ng/L and ng/g level for water and cyanobacterial samples, respectively. The results obtained were also compared with those obtained after using solid phase microextraction, as an alternative for the extraction and purification of the samples. Advantages and disadvantages regarding to the efficiency for impurities removal, simplicity and rapidity and the potential for concentration enhancement of using both methodologies have been also discussed.

Chromatography, High Pressure Liquid↗
PubMed1996

Review of quantitative standards and guidelines for fungi in indoor air.

Existing quantitative standards/guidelines for fungi in indoor air issued by governmental agencies are based primarily on baseline data (rather than health effects data), and are either absolute (numerical) or relative (indoor/outdoor comparisons) or a combination of the two. The Russian Federation is the only governmental agency that has binding quantitative regulations for bioaerosols. Recommended guidelines have been proposed or sponsored by North American and European governmental agencies and private professional organizations. A considerable number of frequently cited guidelines have been proposed by individuals based either on baseline data or on personal experience. Quantitative standards/guidelines range from less than 100 CFU/m3 to greater than 1000 CFU/m3 (total fungi) as the upper limit for non-contaminated indoor environments. Major issues with existing quantitative standards and guidelines are the lack of connection to human dose/response data, reliance on short term grab samples analyzed only by culture, and the absence of standardized protocols for data collection, analysis, and interpretation. Urgent research needs include the study of human responses to specific fungal agents, development and widespread use of standard protocols using currently available sampling methodologies, and the development of long term, time-discriminating personal samplers that are inexpensive, easy to use, and amenable to straightforward, relevant analysis.

Air Microbiology↗
PubMed1999

Generalization of Metropolis and heat-bath sampling for Monte Carlo simulations.

For a wide class of applications of the Monte Carlo method, we describe a general sampling methodology that is guaranteed to converge to a specified equilibrium distribution function. The method is distinct from that of Metropolis in that it is sometimes possible to arrange for unconditional acceptance of trial moves. It involves sampling states in a local region of phase space with probability equal to, in the first approximation, the square root of the desired global probability density function. The validity of this choice is derived from the Chapman-Kolmogorov equation, and the utility of the method is illustrated by a prototypical numerical experiment.

Journal Article↗
PubMed2004

Phylogenetic comparative analysis of life-history variation among populations of the lizard Sceloporus undulatus: an example and prognosis.

Over the past 15 years, phylogenetic comparative methods (PCMs) have become standard in the study of life-history evolution. To date, most studies have focused on variation among species or higher taxonomic levels, generally revealing the presence of significant phylogenetic effects as well as residual variation potentially attributable to adaptive evolution. Recently, population-level phylogenetic hypotheses have become available for many species, making it possible to apply PCMs directly to the level at which experiments are typically used to test adaptive hypotheses. In this study, we present the results of PCMs applied to life-history variation among populations of the widespread and well-studied lizard Sceloporus undulatus. Using S. undulatus (which may represent four closely related species) as an example, we explore the benefits of using PCMs at the population level, as well as consider the importance of several thorny methodological problems including but not limited to nonindependence of populations, lack of sufficient variation in traits, and the typically small sample sizes dictated by the difficulty of collecting detailed demographic data. We show that phylogenetic effects on life-history variation among populations of S. undulatus appear to be unimportant, and that several classic trade-offs expected by theory and revealed by many interspecific comparisons are absent. Our results suggest that PCMs applied to variation in life-history traits below the species level may be of limited value, but more studies like ours are needed to draw a general conclusion. Finally, we discuss several outstanding problems that face studies seeking to apply PCMs below the species level.

Adaptation, Physiological↗
PubMed1995

AIDS knowledge, risk behaviors, and factors related to condom use among male commercial sex workers and male tourist clients in Bali, Indonesia.

OBJECTIVES: To describe the AIDS/sexually transmitted diseases (STD) knowledge and risk behaviors, and to determine factors related to condom use among male commercial sex workers (CSW) and male tourist clients in Bali, Indonesia. DESIGN: Individual survey interviews were conducted with a sample of 80 male CSW and 100 tourist clients in the Kuta area of Bali. METHODS: Survey interviews included detailed questions on AIDS/STD knowledge, sexual behavior, and psychosocial measures related to risk taking. RESULTS: Most of the male CSW had heard about AIDS and other STD, although some misconceptions about transmission and risks of different sexual practices remained. Both oral and anal intercourse with tourists were common and condom use was far from consistent. Factors related to condom use for anal intercourse with tourist clients were condom beliefs, self efficacy, susceptibility to STD infection, and STD knowledge. Tourist clients were mainly from Australia and Europe and many had paid for sex in other parts of Indonesia as well as in high prevalence countries. Knowledge of AIDS/STD was very good among the tourists and previous experience with STD was common. Factors related to condom use with male CSW were condom beliefs and self efficacy. CONCLUSION: There is a very active and mobile group of male CSW and tourist clients present in Bali. Interventions with these men are needed due to the low level of knowledge about AIDS among CSW, their experience with STD and STD symptoms, and their level of risky sexual behavior.

Acquired Immunodeficiency Syndrome↗
PubMed2005

A parametric transfer function methodology for analyzing reactive transport in nonuniform flow.

We analyze reactive transport during in-situ bioremediation in a nonuniform flow field, involving multiple extraction and injection wells, by the method of transfer functions. Gamma distributions are used as parametric models of the transfer functions. Apparent parameters of classical transport models may be estimated from those of the gamma distributions by matching temporal moments. We demonstrate the method by application to measured data taken at a field experiment on bioremediation conducted in a multiple-well system in Oak Ridge, TN. Breakthrough curves (BTCs) of a conservative tracer (bromide) and a reactive compound (ethanol) are measured at multi-level sampling (MLS) wells and in extraction wells. The BTCs of both compounds are jointly analyzed to estimate the first-order degradation rate of ethanol. To quantify the tracer loss, we compare the approaches of using a scaling factor and a first-order decay term. Results show that by including a scaling factor both gamma distributions and inverse-Gaussian distributions (transfer functions according to the advection-dispersion equation) are suitable to approximate the transfer functions and estimate the reactive rate coefficients for both MLS and extraction wells. However, using a first-order decay term for tracer loss fails to describe the BTCs at the extraction well, which is affected by the nonuniform distribution of travel paths.

Biodegradation, Environmental↗
PubMed1998

The ABC Schizophrenia Study: a preliminary overview of the results.

The ABC Schizophrenia Study, a large-scale epidemiological and neurobiological research project commenced in 1987, initially pursued two aims: (1) to elucidate the possible causes of the sex difference in age at first admission for schizophrenia and (2) to analyse the early course of the disorder from onset until first contact and its implications for further course and outcome. First, transnational case-register data (for Denmark and Germany) were compared, second, a population-based sample of first-episode cases of schizophrenia (n = 232) were selected and third, the results obtained were compared with data from the WHO Determinants of Outcome Study by using a systematic methodology. A consistent result was a 3-4 years higher age of onset for women by any definition of onset, which was not explainable by social variables, such as differences in the male-female societal roles. A sensitivity-reducing effect of oestrogen on central D2 receptors was identified as the underlying neurobiological mechanism in animal experiments. Applicability to humans with schizophrenia was established in a controlled clinical study. A comparison of familial and sporadic cases showed that in cases with a high genetic load, the sex difference in age of onset disappeared due to a clearly reduced age of onset in women, whereas in sporadic cases it increased. To analyse early course retrospectively, a semistructured interview, IRAOS, was developed. The early stages of the disorder were reconstructed in comparison with age- and sex-matched controls from the same population of origin. The initial signs consisted mainly of negative and affective symptoms, which accumulated exponentially until the first episode, as did the later emerging positive symptoms. Social disability appeared 2-4 years before first admission on average. In early-onset cases, social course and outcome, studied prospectively over 5 years, was determined by the level of social development at onset through social stagnation. In late-onset cases, decline from initially high social statuses occurred. Socially negative illness behaviour contributed to the poor social outcome of young men. Symptomatology and other proxy variables of the disorder showed stable courses and no sex differences. Further aspects tested were the sequence of onset and the influence of substance abuse on the course of schizophrenia, primary and secondary negative symptoms, structural models and symptom clusters from onset until 5 years after first admission.

Adolescent↗
PubMed2006

Low-level exertions of the neck musculature: a study of research methods.

Musculoskeletal neck discomfort is prevalent in many occupations and has been the focus of much research employing surface electromyography (sEMG). Significant differences in experimental methods among researchers make comparisons across studies difficult. The goal of the current research was to use empirical methods to answer specific methodological questions concerning use of sEMG in evaluation of the neck extensor system. This was accomplished in two studies. In Experiment 1, ultrasound technology was used to: (a) determine accessibility of m. splenius and semispinalis capitis with surface electrodes, (b) identify appropriate electrode locations for these muscles/muscle groups, and (c) illustrate potential benefits of using ultrasound in locating muscles/placing electrodes. Experiment 2 sought to assess effects of posture when normalizing sEMG data. Results from Experiment 1 showed no direct access to semispinalis capitis for surface electrodes; their activity can only be sampled as part of a group of muscles. In most subjects, m. splenius was found to be accessible to surface electrodes. Electrode placement recommendations are provided. Results of Experiment 2 showed significant differences in normalized EMG data between a posture-specific technique and a reference posture technique. Posture-specific normalization is recommended for accurately assessing the relative intensity of contractions of these muscles.

Electromyography↗
PubMed2001

Detecting and measuring senescence in wild birds: experience with long-lived seabirds.

This paper points out and discusses several practical and methodological problems that arise in attempts to detect and measure senescent declines in survival or breeding performance of wild animals, with specific emphasis on long-lived seabirds. Birds have no anatomical markers of age, so studies of age-related biology require marking individuals at the time of hatching and following them throughout their lives. Seabirds live longer than the working lifespan of biologists, and longer than the turnover times of study techniques or theories of senescence. Seabirds are exposed to changing environmental and demographic conditions and cannot be assumed to be in demographic equilibrium. Sample sizes of the oldest age-classes are always small, requiring either marking very large numbers of birds at hatching or continuing studies of old birds over many years. Incomplete sampling requires the use of mark-recapture models that have only been developed in the last 20years. Mortality selection resulting from demographic heterogeneity (selective survival of high-quality individuals) can offset or confound the effects of senescent changes within individuals. Many of these problems are amenable to solution and will be probably solved within a few years. In the meantime, this paper recommends that reviewers should be cautious about accepting published reports of senescent declines in natural populations.

Aging↗
PubMed1996

Application of the bootstrap to calibration experiments.

In calibration experiments, a number of samples of known concentration are used to establish the relationship between a measured response and sample concentration; this relationship is then used to estimate the unknown concentration of further samples from their measured responses. In addition to the estimates themselves, it is useful to have available some measure of their precision, usually given in the form of confidence limits. The standard method of inverting prediction limits is found to work well in simple situations, but in nonlinear multivariate calibration it becomes intractable. The bootstrap offers an alternative methodology, but in the calibration framework its application is not obvious. We describe some considerations in bootstrapping calibration data and compare our methods with a previous attempt and with the standard method in linear, nonlinear, and multivariate situations. The bootstrap is found to be a useful tool in those situations where the standard method is difficult to implement.

Calibration↗
PubMedDate not supplied

Enrichment of fetal nucleated red blood cells from the maternal circulation for prenatal diagnosis: experiences with triple density gradient and MACS based on more than 600 cases.

OBJECTIVE: We wanted to obtain statistically relevant data about the efficiency of our method for the isolation of fetal nucleated red blood cells (NRBCs) from the maternal circulation. METHODS: More than 600 samples were investigated using a triple density gradient followed by magnetic separation of anti-CD71-labeled cells, and yields and purities of recovered NRBCs were determined. RESULTS: The enrichment effectivity as well as the morphological condition of cells was reproducibly good, if blood samples were enriched within 48 h after sampling. The efficacy was independent of various methodological parameters and our technique was superior to other magnetic cell-sorting techniques. Mean yields and purities of NRBCs increased with increasing gestational age, ranging from 100 to 1,000 cells per 40-ml blood sample and from 0.1 to 1%, respectively, from the 6th week of gestation to term. In pregnancies with preeclampsia NRBCs were increased by a factor of 10. CONCLUSION: Our enrichment technique proved to be optimized with respect to various methodological parameters, which were compared in the present study, and it is efficient and reproducible for the enrichment of NRBCs from the maternal circulation in all three gestational trimesters.

Antigens, CD↗
PubMed2003

An intervention program to reduce dental avoidance behaviour among adolescents: a pilot study.

AIM: To develop and test the methodology of an intervention to reduce avoidance of dental care among adolescents, and to measure the respondents' beliefs regarding the intervention (credibility and cognitions). METHODS: Based on a group comparison design a sample of 18 year olds (n=50) with dental non-attendance behaviour was randomly selected to three experimental and one control group. Subjects were surveyed with one baseline questionnaire and one post-intervention questionnaire, to evaluate their beliefs regarding the program. Two different instruments were tested: 1) cards representing different statements related to previous dental experiences, possible reasons for attending (pros) and not attending (cons) dental appointments, and preferences for future treatment. Cards were selected based on individual priority; 2) a brief, structured telephone interview based on Motivational Interviewing. The instruments were tested separately (groups I and II) and in combination (group III). Subjects in the control group (group IV) were given conventional health education. RESULTS: Subjects in the experimental groups had significantly higher credibility scores to the statement "How much easier do you perceive dental treatment to be for you, based on this program", compared with the control group (p<0.05). They had also more positive beliefs to the statement "I think the interviewer liked to talk to me" (p<0.05) than controls. CONCLUSION: A questionnaire sent to non-attending adolescents followed by a brief telephone call based on Motivational Interviewing appears to be a credible intervention for adolescents avoiding dental care.

Adolescent↗
PubMed1993

DNA analysis of haemophilia A families from southern France. Experience of a hospital laboratory.

A sample of 101 individuals from 19 unrelated families from Southern France affected with haemophilia A was studied in our laboratory from 1990 to 1992. The aim of the analysis was to define the carrier status of women related to a haemophiliac, or to find an informative DNA marker for further prenatal diagnosis in obligate carriers. Three intragenic (BclT/intron 18, XbaI/intron 22, AlwNI/intron x7) and two extragenic polymorphisms (TaqI/St14, BglII/DX13) were used for this study. The tested population exhibited some original characteristics, including a lower rate of heterozygosity for the FVIII BclI polymorphism and a number of specificities for the St14 RFLP. We also compared the different methodologies available for each RFLP in a routine diagnostic service, and determined a strategy for linkage analysis in our population.

Adult↗
PubMed2003

HIV-1 Fitness and Replication Capacity: What Are They and Can They Help in Patient Management?

The natural history of HIV-1 infection is characterized by persistent viremia, progressive CD4 lymphopenia, and profound immune suppression resulting in opportunistic infections, neoplasms, and death. Introduction of combination antiretroviral therapy has been effective in suppressing HIV-1 replication, reversing immunodeficiency to a degree, reducing HIV-1-associated complications, and thereby prolonging life. One of the most vexing challenges of prolonged antiretroviral therapy is the development of drug resistance. Antiretroviral therapies fail in a substantial number of cases, often with emergence of HIV-1 variants encoding mutations that confer potent drug resistance to individual agents or entire drug classes. Resistance testing methods have been introduced to evaluate drug resistance, and several studies have reported clinical benefits of genotyping and phenotyping assays in clinical decision-making. However, the genetic variability of HIV-1 to develop resistance exceeds the antiretroviral armamentarium, and the number of patients with drug experience and resistance to all classes of antiretrovirals continues to grow. From a clinical standpoint, it would be useful to have a more comprehensive grasp of pathogenic determinants of HIV-1 in all patients. One proposed in vitro correlate of HIV-1 pathogenic potential is the replication capacity of HIV-1. New techniques to assess HIV-1 replication potential are in development, with a commercial assay now available to analyze clinical samples. In this review we explore the experimental basis for replication capacity measurements and potential clinical applications of this methodology.

Journal Article↗
PubMed2004

Bereaved parents' experience of research participation.

Despite the ethical codes guiding bereavement research, few studies have been conducted to evaluate the perceived stress experienced by the bereaved, and to explore which methodologies cause least distress. This article investigates how bereaved and traumatised populations experience research participation, and they voice their recommendations for future research. The data are from a nationwide three-phase study in Norway among parents who had lost their child by suicide, SIDS, and accidents between July 1, 1997 and December 31, 1998. Whereas the first phase reported quantitative results of perceived psychosocial health and focused on offered and ideal support (N=262), the second phase investigated the same issues through in-depth interviews of a sub sample (N=69). Phase three, reported here, included the responses of 64 parents to a short questionnaire evaluating research participation in the two previous phases. The results show that 100% of the parents experienced participation as "positive"/"very positive", and none regretted participating. They linked the positive experiences to being allowed to tell their complete story, the format of the interview, and a hope that they might help others. Apparently, processes of meaning reconstruction and increased awareness of the bereavement process were facilitated by the interviews. However, three-quarters of the interviewees reported that it was to a greater or lesser degree painful to talk about the traumatic loss. Regression analysis showed that being a woman and high levels of psychic distress were the most important predictors of a painful interview experience. In order to protect bereaved and vulnerable populations from harm, already existing ethical codes must be strictly applied, and the researchers must listen respectfully to recommendations from bereaved parents.

Accidents↗
PubMed1984

The syndrome concept: history and statistical operationalizations.

A historical analysis of the syndrome concept shows that this term has been used in many different ways, ranging from clinical experience to records of coinciding symptoms. However, there seems to be broad agreement on the use of the word 'syndrome' in daily practice. If empirical-mathematical methods are applied in syndrome detection, however, a precise operationalization of the syndrome concept is needed. Traditional procedures have often used models more dictated by methodological considerations than derived from the field of application, i.e. psychiatric syndromatology. An alternative approach, Boolean factor analysis, is presented in this paper. This relatively new method is illustrated by means of the analysis of a small artificial sample with a known structure. As a point of reference, traditional methods (factor analysis, cluster analysis, and multidimensional scaling) are also briefly discussed. It is demonstrated that they all share a deficiency of information about inter-group structure. In contrast, Boolean factor analysis uses a syndromic definition which builds on the basic notion of concurrent symptoms. Moreover, this approach can easily be understood by clinicians.

Computers↗
PubMed1981

Gas Chromatography-Mass Spectrometry of N- Heptafluorobutyryl Isobutyl Esters of Amino Acids in the Analysis of the Kinetics of [N]H(4) Assimilation in Lemna minor L.

Rapid, sensitive, and selective methods for the determination of the (15)N abundance of amino acids in isotopic tracer experiments with plant tissues are described and discussed. Methodology has been directly tested in an analysis of the kinetics of [(15)N]H(4) (+) assimilation in Lemna minor L. The techniques utilize gas chromatography-mass spectrometry selected ion monitoring of major fragments containing the N moiety of N-heptafluorobutyryl isobutyl esters of amino acids. The ratio of selected ion pairs at the characteristic retention time of each amino acid derivative can be used to calculate (15)N abundance with an accuracy of +/-1 atom% excess (15)N using samples containing as little as 30 picomoles of individual amino acids. Up to 11 individual amino acid derivatives can be selectively monitored in a single chromatogram of 30 minutes. It is suggested that these techniques will be useful in situations where the small quantities of N available for analysis have hitherto hindered the use of (15)N-labeled precursors.

Journal Article↗