Evaluation of time-to-pregnancy as a measure in environmental epidemiology

Since the late 80's, time to pregnancy has been used in environmental epidemiology to explore adverse effects of different exposures. The advantages of this measure and additional elements to be considered in the performance of this type of studies are reviewed. Study design includes the following steps: population selection, sample size, outcome measurement, statistical analyses and sources of bias. Guidelines were suggested for the properly development of this type of study.     

Evaluation of a method to measure long term cortisol levels

IntroductionElevated levels of cortisol are known to induce various symptoms and diseases, e.g. abdominal obesity, type 2 diabetes, osteoporosis and cardiovascular disease. Measuring serum, saliva and urine cortisol is limited to one time point. Measurement of cortisol in scalp hair is a recently developed method to measure long term cortisol levels. The aim of this study was to investigate whether hair cortisol is a feasible parameter to measure cortisol exposure.ExperimentalWe collected hair samples of 195 healthy individuals, 9 hypercortisolemic and one hypocortisolemic patient and measured hair cortisol levels. Cortisol was extracted from scalp hair using methanol and cortisol levels were measured using a salivary ELISA kit. Measurement of waist and hip circumferences and blood pressure was performed in 46 healthy subjects.ResultsWe found a positive correlation between hair cortisol and both waist circumference (r = 0.392, p = 0.007) and waist-to-hip ratio (WHR) (r = 0.425, p = 0.003). No correlations were found between hair cortisol levels and BMI, blood pressure or age. There was no decline in cortisol levels in six consecutive hair segments. Hair cortisol levels were elevated in patients with known hypercortisolism (p < 0.0001).ConclusionsHair cortisol was positively correlated with WHR, suggesting that hair cortisol reflects cortisol exposure at tissue level, which was also supported by elevated hair cortisol levels in hypercortisolemic patients and concordance between hair cortisol levels and clinical disease course. Cortisol levels in hair are slightly influenced by hair treatment but not by natural hair colour, use of hair products, gender or age.     

Evaluation of laser-Doppler flowmetry as a measure of tissue blood flow

In this study the technique of laser-Doppler flowmetry was evaluated for the measurement of tissue blood flow by comparing laser-Doppler flow (LDF) signal in the renal cortex, gracilis muscle, and cremaster muscle of anesthetized rats to whole-organ blood flow measured with an electromagnetic flowmeter or radioactive microspheres. In vitro, LDF signal was closely correlated (r = 0.99) to changes in erythrocyte velocity generated with a rotating wheel. Although individual LDF readings varied in situ, mean LDF signal calculated from multiple readings on the tissue surface were significantly correlated (r = 0.74-0.95) with tissue blood flows measured at various perfusion pressures. However, significant differences in the slope of the LDF signal vs. blood flow relationship were observed in different tissues and with different methods of measurement in the same tissue. This study indicates that mean laser-Doppler flow signal provides a good estimate of tissue blood flow, provided a sufficient number of points is scanned. However, there appears to be no universal calibration factor for the method.     

Evaluation of a forced oscillation method to measure thoracic gas volume

The purposeof this study was to test a plethysmographic method of measuringthoracic gas volume (TGV) that, contrary to the usual panting method,would not require any active cooperation from the subject. It is basedon the assumption that the out-of-phase component of airway impedancevaries linearly with frequency. By using that assumption, TGV may becomputed by combining measurements of total respiratory impedance (Zrs)and of the relationship between the plethysmographic signal (Vpl) andairway flow () during forcedoscillations at several frequencies. Zrs and Vpl/were measured at 10 noninteger multiple frequencies ranging from 4 to29 Hz in 15 subjects breathing gas in nearlyBTPS conditions. Forced oscillationmeasurements were immediately followed by determination of TGV by thestandard method. The data were analyzed on different frequency ranges,and the best agreement was seen in the 6- to 29-Hz range. Within thatrange, forced oscillation TGV and standard TGV differed little(3.92 ± 0.66 vs. 3.83 ± 0.73 liters,n = 77, P < 0.05) and were stronglycorrelated (r = 0.875); thedifferences were not correlated to the mean of the two estimates, andtheir SD was 0.35 liter. In seven subjects the differences weresignificantly different from zero, which may, in part, be due toimperfect gas conditioning. We conclude that the method is not highlyaccurate but could prove useful when, for lack of sufficientcooperation, the panting method cannot be used. The results of computersimulation, however, suggest that the method would be unreliable in thepresence of severe airway inhomogeneity or peripheral airwayobstruction.

     

Evaluation of a method to measure conjugal transfer of recombinant DNA in soil slurries

Release of recombinant microbes into the environment necessitates an evaluation of their ability to transfer genetic material. The present report evaluates a method to detect conjugal DNA plasmid transfer in soil slurries under various environmental conditions. DonorPseudomonas cepacia containing pR388::Tn1721 andP. cepacia recipient cultures were coincubated in soil slurries containing autoclaved or natural soil and treated with one or more of 14 experimental conditions. Conjugal mating frequency (transconjugants per initial donor) ranged from 4.8×10^–1 to 1.9×10^–7. Highest numbers of transconjugants, 1.5×10⁷ colony forming units/ml soil slurry, were observed following incubation at 35°C with an enriched nutrient supplement added to the soil. Low numbers of transconjugants, 10³ colony forming units/ml soil slurry, were observed when mating pairs were subjected to low nutrient or pH stress even though initial donor and recipient populations were maintained at high levels. This test system provides a simple way to estimate effects of changing environmental factors on plasmid transfer rates and on the survival of recombinant microorganisms. By use of soil collected from sites proposed to receive genetically engineered microorganisms, preliminary risk assessments can be obtained regarding the potential for gene transfer and microorganism survival with this soil slurry test system.     

Evaluation of gene-expression clustering via mutual information distance measure

Background  

The definition of a distance measure plays a key role in the evaluation of different clustering solutions of gene expression profiles. In this empirical study we compare different clustering solutions when using the Mutual Information (MI) measure versus the use of the well known Euclidean distance and Pearson correlation coefficient.     

Evaluation of 100% rapid rescreening of negative cervical smears as a quality assurance measure

OBJECTIVE: The objective of this study was to compare the performance of 100% rapid rescreening, 10% random rescreening and the review of smears selected on the basis of clinical criteria, as a method of internal quality control of cervical smears classified as negative during routine screening. METHODS: A total of 3149 smears were analysed, 173 of which were classified as positive and 2887 as negative, while 89 smears were considered unsatisfactory. The smears classified as negative were submitted to 100% rapid rescreening, 10% random rescreening, and rescreening based on clinical criteria. The rescreening stages were blinded and results were classified according to the Bethesda 2001 terminology. Six cytologists participated in this study, two of whom were responsible for routine screening while the other four alternated in carrying out rescreening so that no individual reviewed the same slide more than once. RESULTS: The 100% rapid rescreening method identified 92 suspect smears, of which 42 were considered positive at final diagnosis. Of the 289 smears submitted to the 10% rescreening method, four were considered abnormal but only one was confirmed positive in the final diagnosis. Of the 690 smears rescreened on the basis of clinical criteria, 10 were considered abnormal and eight received a positive final diagnosis. CONCLUSIONS: The 100% rapid rescreening method is more efficient at detecting false-negative results than 10% random rescreening or rescreening on the basis of clinical criteria, and is recommended as an internal quality control method.     

Evaluation of a fully automated method to measure the critical removal stress of adult barnacles

A computer-controlled force gauge designed to measure the adhesive strength of barnacles on test substrata is described. The instrument was evaluated with adult barnacles grown in situ on Silastic T2(R)-coated microscope slides and epoxy replicas adhered to the same substratum with synthetic adhesive. The force per unit area required to detach the barnacles (critical removal stress) using the new automated system was comparable to that obtained with ASTM D5618 (1994) (0.19 and 0.28 MPa compared with 0.18 and 0.27 MPa for two batches of barnacles). The automated method showed a faster rate of force development compared with the manual spring force gauge used for ASTM D5618 (1994). The new instrument was as accurate and precise at determining surface area as manual delineation used with ASTM D5618 (1994). The method provided significant advantages such as higher throughput speed, the ability to test smaller barnacles (which took less time to grow) and to control the force application angle and speed. The variability in measurements was lower than previously reported, suggesting an improved ability to compare the results obtained by different researchers.     

Evaluation of a fully automated method to measure the critical removal stress of adult barnacles

A computer-controlled force gauge designed to measure the adhesive strength of barnacles on test substrata is described. The instrument was evaluated with adult barnacles grown in situ on Silastic T2®-coated microscope slides and epoxy replicas adhered to the same substratum with synthetic adhesive. The force per unit area required to detach the barnacles (critical removal stress) using the new automated system was comparable to that obtained with ASTM D5618 (1994 ASTM D5618. 1994. Standard test method for measurement of barnacle adhesion strength in shear American Standard for Testing and Materials. Paint-Tests for formulated products and applied coatings 06.01 [Google Scholar]) (0.19 and 0.28 MPa compared with 0.18 and 0.27 MPa for two batches of barnacles). The automated method showed a faster rate of force development compared with the manual spring force gauge used for ASTM D5618 (1994 ASTM D5618. 1994. Standard test method for measurement of barnacle adhesion strength in shear American Standard for Testing and Materials. Paint-Tests for formulated products and applied coatings 06.01 [Google Scholar]). The new instrument was as accurate and precise at determining surface area as manual delineation used with ASTM D5618 (1994 ASTM D5618. 1994. Standard test method for measurement of barnacle adhesion strength in shear American Standard for Testing and Materials. Paint-Tests for formulated products and applied coatings 06.01 [Google Scholar]). The method provided significant advantages such as higher throughput speed, the ability to test smaller barnacles (which took less time to grow) and to control the force application angle and speed. The variability in measurements was lower than previously reported, suggesting an improved ability to compare the results obtained by different researchers.     

Evaluation of d2, a microsatellite measure of inbreeding and outbreeding, in wolves with a known pedigree

We have evaluated a microsatellite measure proposed as an indicator of inbreeding and outbreeding using a captive wolf population with known inbreeding levels and founder sources. The measure, which is based on the difference in the repeat number for microsatellite alleles within an individual, was not more predictive of the known inbreeding coefficient than microsatellite heterozygosity (it was actually less predictive). We also found no support that the measure was predictive of the level of outbreeding. However, we could not determine if the measure was predictive of very low levels of inbreeding due to matings between remote relatives. Overall, it appears that the usefulness of this measure to identify individuals on the inbred-outbred continuum beyond that of heterozygosity and identify biologically important associations with fitness-related traits may be limited. We suggest that the measure be examined theoretically to determine when (and how much) the predictive value of the measure is different from that of heterozygosity for inbreeding or outbreeding levels in a variety of different scenarios.     

Coastal eutrophication research: a new awareness

An analysis of the contents and conclusions of the papers contained in this issue (Hydrobiologia Volume xxx) suggests that a new vision is taking shape that may correspond to an emerging new paradigm in the way we understand and manage coastal eutrophication. This new paradigm emphasizes its global dimension and the connections with other global environmental pressures, and re-evaluates the targets of remedial actions and policies. Eutrophication research must evolve toward a more integrative, ecosystem perspective which requires that it be extended to include impacts beyond primary producers and to examine possible cascading effects and feedbacks involving other components of the ecosystem. A quantitative framework that incorporates the interacting top-down and bottom-up effects in eutrophication models must be urgently developed to guide diagnostics and establish targets to mitigate coastal eutrophication. The required macroscopic view must also be extended to the managerial and policy frameworks addressing eutrophication, through the development of policies that examine activities in the environment in an integrative, rather than sectorial, manner. Recent evidence of complex responses of coastal ecosystems to nutrient reduction requires that management targets, and the policies that support them, be reconsidered to recognize the complexities of the responses of coastal ecosystems to reduced nutrient inputs, including non-linear responses and associated thresholds. While a predictive framework for the complex trajectories of coastal ecosystems subject to changes in nutrient inputs is being developed, the assessment of managerial actions should be reconsidered to focus on the consideration of the status achieved as the outcome of nutrient reduction plans against that possibly derived from a ‘do nothing’ scenario. A proper assessment of eutrophication and the efforts to mitigate it also requires that eutrophication be considered as a component of global change, in addressing both its causes and its consequences, and that the feedbacks between other components of global change (e.g., climate change, overfishing, altered biogeochemical cycles, etc.) be explicitly considered in designing eutrophication research and in managing the problem. Guest editors: J. H. Andersen & D. J. Conley Eutrophication in Coastal Ecosystems: Selected papers from the Second International Symposium on Research and Management of Eutrophication in Coastal Ecosystems, 20–23 June 2006, Nyborg, Denmark     

Evaluation of some enzymatic methods to measure the bio-activity of aquatic environments

Methods have been evaluated and standardised to measure the phosphatase, saccharase, amylase and lipase enzymatic activities in aquatic environments. The analytical reproducibility, the ecological applicability and the etiology of these activities have been investigated. The usefulness of the various enzymatic assays for routine analyses and for fundamental research of aquatic environments is discussed.     

Endophenotypes as a measure of suicidality

Suicide is thought to result from the harmful interaction of multiple factors that have social, environmental, neurobiological, and genetic backgrounds. Recent studies have suggested that genetic predisposition to suicidal behavior may be independent of the risk of suicide associated to mental disorders, such as affective disorders, schizophrenia, or alcohol dependence. Given the suicidal behavior heterogeneity and its hereditary complexity, the need to find demonstrable intermediate phenotypes that may make it possible to establish links between genes and suicide behaviors (endophenotypes) seems to be necessary. The main objective of this review was to consider the candidate endophenotypes of suicidal behaviors. Due to the recent advances in neuroimaging, we also characterize brain regions implicated in vulnerability to suicide behavior that are influenced by gene polymorphisms associated with suicidal behavior.     

Evaluation of the electro-ultrafiltration technique (EUF) as a measure of the K supplying power of Quebec soils

The electro-ultrafiltration (EUF) method has been used to evaluate the short-term and long-term supplying power of soils for many essential plant nutrients. The objective of this study was to compare the capacity of EUF with other extraction techniques to predict the plant availability of soil K and K fertilizer responsiveness by 10 cuts of alfalfa (Medicago sativa L.) growing over a 366-day period. Increasingly higher average concentrations of soil K were extracted by EUF at 50 V and 20°C (29 mg kg^-1), EUF at 200 V and 20°C (48 mg kg^-1), 0.002 M SrCl₂ (55 mg kg^-1), EUF at 200 V and 80°C (85 mg kg^-1), 0.1 M HCl (105 mg kg^-1), Mehlich 3 (119 mg kg^-1), 1 M NH₄OAc (120 mg kg^-1) and boiling 1 M HNO₃ (601 mg kg^-1). The large content of vermiculitic minerals in the silt and clay fractions is responsible for EUF desorbing more K in 55 minutes than NH₄OAc in 29 out of 30 soils. The total amount of K desorbed by EUF at 80°C was as effective as Mehlich 3-extractable K in predicting K uptake for the first three cuts and was best among the extracting procedures after boiling 1 M HNO₃ in predicting the long-term K supply, the uptake of K from non-exchangeable sources and the relative yield of alfalfa over 10 cuts. The desorption of soil K with EUF provides a better evaluation of the K-supplying power of Quebec soils than the extractants currently used, especially on a long-term basis.Contribution no. 396.     

Spatial awareness

A new method of mapping marine environments and activities is hoped will help better resolve conflicting uses and conservation interests.