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PubMed2005

Bromate analysis in groundwater and wastewater samples.

Bromate (BrO(3)(-)) is a disinfection by-product formed during ozonation of potable water supplies containing bromide (Br(-)). Bromate has been classed by the World Health Organisation as a 'possible human carcinogen', leading to implementation of 10-25 microg L(-1)(as BrO(3)(-)) drinking water limits in legislative areas including the United States and European Union. Techniques have been developed for bromate analysis at and below regulatory limits, with Ion Chromatography (IC) coupled with conductivity detection (IC-CD), post-column reaction and ultra-violet (UV) detection (IC-PCR), or inductively coupled plasma-mass spectrometry detection (IC-ICPMS) in widespread use. The recent discovery of bromate groundwater contamination in a UK aquifer has led to a requirement for analysis of bromate in a groundwater matrix, for environmental monitoring and development of remediation strategies. The possibility of bromate-contaminated water discharge into sewage treatment processes, whether accidental or as a pump-and-treat strategy, also required bromate analysis of wastewater sources. This paper summarises techniques currently available for trace bromate analysis in potable water systems and details studies to identify a methodology for routine analysis of groundwater and wastewater samples. Strategies compared were high performance liquid chromatography (HPLC) with direct UV or PCR/UV detection, IC-CD, IC-PCR, and a simple spectrophotometric technique. IC-CD was the most cost-effective solution for simultaneous analysis of bromate and bromide within groundwater samples, having a 5 microg L(-1) detection limit of both anions with limited interference from closely-eluting species. Wastewater samples were successfully analysed for bromate only using HPLC with PCR/UV detection, with detection limits below 20 microg L(-1)(as BrO(3)(-)) and low interference. HPLC with direct UV detection was unsuitable for bromate analysis within the concentration range 50-5000 microg L(-1) which was required for this project, but column choice was shown to be a major factor in determining limits of detection. Spectrophotometry could not reproducibly determine bromate concentration, although the technique showed promise as a quick field method for high-level groundwater bromate analysis.

Bromates↗
PubMed1996

Unconstrained procedures for the estimation of positive definite covariance matrices using restricted maximum likelihood in multibreed populations.

Two unconstrained procedures to ensure that intrabreed and interbreed genetic and environmental covariance estimates for multibreed populations are computed within the permissible ranges were developed. These procedures were called Partial Scoring and Cholesky Maximization. The Partial Scoring procedure uses partial steps to keep estimates of covariance matrices positive definite at each expectation-maximization (EM) iteration, and the Cholesky Maximization procedure achieves the same goal by computing the elements of the Cholesky Decomposition of each intrabreed and interbreed genetic and environmental covariance matrix. Groups of small simulated data sets containing either direct genetic effects of two traits (90 bulls, 13,500 calves) or direct and maternal genetic effects for a single trait (135 bulls, 32,400 calves) were used to test the computational feasibility of these two procedures. The overall means (and ranges) of the numbers of expectation-maximization iterations, times to convergence, and accuracy of estimation were 10 (2 to 184), 26.2 min (4.1 to 773.2 min), and 40.1% (12.7 to 81.9%) for the Partial Scoring procedure and 7 (3 to 37), 16.7 min (9.5 to 64.6 min), and 37.8% (3.1 to 67.8%) for the Cholesky Maximization procedure. Although the overall accuracy of both procedures was similar, the Cholesky Maximization procedure should be preferred because it converged faster and its covariance estimates were less affected by the values of the covariance priors than those computed using the Partial Scoring strategy. Application to large unbalanced multibreed data sets will require an iterative version of these procedures.

Animals↗
PubMed1975

Population genetics of euphydryas butterflies. I Genetic variation and the neutrality hypothesis.

Twenty-one populations of the checkerspot butterfly, Euphydryas editha, and ten populations of Euphydryas chalcedona were sampled for genetic variation at eight polymorphic enzyme loci. Both species possessed loci that were highly variable from population to population and loci that were virtually identical across all populations sampled. Our data indicate that the neutrality hypothesis is untenable for the loci studied, and therefore selection is indicated as the major factor responsible for producing these patterns. Thorough ecological work allowed gene flow to be ruled out (in almost all instances) as a factor maintaining similar gene frequencies across populations. The Lewontin-Krakauer test indicated magnitudes of heterogeneity among standardized variances of gene frequencies inconsistent with the neutrality hypothesis. The question of whether or not to correct this statistic for sample size is discussed. Observed equitability of gene frequencies of multiple allelic loci was found to be greater than that predicted under the neutrality hypothesis. Genetic differentiation persisting through two generations was found between the one pair of populations known to exchange significant numbers of individuals per generation. Two matrices of genetic distance between populations, based on the eight loci sampled, were found to be significantly correlated with a matrix of environmental distance, based on measures of fourteen environmental parameters. Correlations between gene frequencies and environmental parameters, results of multiple regression analysis, and results of principle component analysis showed strong patterns of association and of "explained" variation. The correlation analyses suggest which factors might be further investigated as proximate selective agents.

Animals↗
PubMed2000

[Development of a ground-based experimental facility for space cultivation of higher plant].

A ground-based experimental facility was developed for conducting initial ground-based simulation study of Controlled Ecological Life Support System (CELSS). The facility is composed of a main chamber, O2 and CO2 composition control subsystems, plant cultivation subsystem and whole data management subsystem. The growth room, being composed of a inner wall of mirror-face stainless steel, holds a volume of 1.8 m3 and a growing area of 1.2 m2; electronic fluorescent lamps were used as lighting sources and polyvinyl formal was used for root matrixes; the environmental parameters of the growing room such as temperature, relative humidity, O2 concentration, CO2 concentration, lighting period and irradiance intensity and the nutrient parameters such as pH, electrical conductivity, dissolved oxygen concentration, liquid level of nutrient storage tank and flow rate of nutrient were all controlled automatically; all of the above-mentioned parameters can be inspected, collected, stored and printed regularly and dynamically. The results of a combined debugging and preliminary plant cultivation verified that the technical target of the facility had reached its initial design requirements, it can be used to conduct ground-based simulation studies of space cultivation of higher plants.

Air Conditioning↗
PubMedDate not supplied

Role of mast cells in dermatofibroma: recent viewpoints into the pathogenesis.

Mast cells are often discussed to play an important role in the tissue fibrotic process, because increased numbers of mast cells are found in the fibrous lesions. Recent evidence has revealed that mast cells are a rich source of cytokines or mediators, which are supposed to play a crucial role in altering the environmental extracellular matrix, leading to fibrosis. Dermatofibromas (DFs) are benign tumors histologically characterized by local fibroblast proliferation. It has been demonstrated that multiple DFs occur in patients with autoimmune diseases or under immunosuppressive therapy, implying that DFs are reactive tumors, rather than true neoplasms, at least in one aspect. Increased numbers of mast cells are also found in both solitary and multiple DFs, in particular in the layers between the DF lesion and the overlying epidermis. The presence of mast cells could be significant in the induction of several histopathologic changes, including acanthosis of the overlying epidermis, basal melanosis, and possibly mononuclear cell recruitment, in DF. Further elucidation of the role of mast cells may lend support to the understanding of the mechanism of DF.

Autoimmune Diseases↗
PubMed2006

Modulation of cell-fibronectin matrix interactions during tissue repair.

Environmental signals from the extracellular matrix (ECM) are transmitted by cell surface receptors that connect to the actin cytoskeleton and to multiple intracellular signaling pathways. To dissect how the ECM regulates cell functions, we are using a three-dimensional (3D) fibrin-fibronectin matrix, resembling the wound provisional matrix. Fibroblasts adhere to fibronectin in this matrix via concomitant engagement of alpha 5 beta 1 integrin receptors and syndecan-4, a transmembrane proteoglycan. An adhesive phenotype is developed with actin stress fibers and activation of focal adhesion kinase (FAK) and Rho GTPase. Lack of syndecan-4 engagement, as occurs in the presence of the ECM protein tenascin-C, promotes a motile phenotype; FAK and Rho signaling are downregulated and filopodia are extended. Fibronectin matrices have distinct effects on two other receptors: alpha 4 beta 1 and beta v beta 3 integrins. Although alpha 4 beta 1 does not naturally support strong cell interactions with a fibrin-fibronectin matrix, binding is dramatically enhanced by proteolytic cleavage of fibronectin. Conversely, activity of alpha v beta 3 is stimulated by multimeric fibronectin fibrils showing that the organization of fibronectin differentially affects integrin functions. Thus, deposition of additional ECM components, expression of co-receptors for ECM, cleavage of adhesive proteins, and the architecture of the ECM microenvironment are different mechanisms for modulating cell responses to fibronectin matrix.

Animals↗
PubMed2005

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry with a matrix of carbon nanotubes for the analysis of low-mass compounds in environmental samples.

The use of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) for environmental analysis has been mainlyfocused on qualitative analysis of high-mass molecules, such as toxins, humic acid, and microorganisms. Herein,we describe a novel MALDI-TOF-MS method with a matrix of oxidized carbon nanotubes for analysis of low-mass compounds in environmental samples. A number of chemicals in the environment were qualitatively analyzed by the present method, and it was found that most of them, especiallythe highly polar chemicals, were measurable with high sensitivity. With the intrinsic ability to measure high-mass chemicals, this method can compensate for the current shortage of methods for environmental analysis for the measurement of highly polar or high-mass chemicals. For sample analysis, arsenic speciation in Chinese traditional medicines was qualified and diphenylolpropane in water samples was quantified. With the relatively high tolerance of the method to interfering molecules, a simple pretreatment or even no pretreatment could be employed before MS detection. Furthermore, this method can be employed in a high-throughput format.

Arsenic↗
PubMed2001

LC-MS/MS signal suppression effects in the analysis of pesticides in complex environmental matrices.

The application of LC separation and mobile phase additives in addressing LC-MS/MS matrix signal suppression effects for the analysis of pesticides in a complex environmental matrix was investigated. It was shown that signal suppression is most significant for analytes eluting early in the LC-MS analysis. Introduction of different buffers (e.g. ammonium formate, ammonium hydroxide, formic acid) into the LC mobile phase was effective in improving signal correlation between the matrix and standard samples. The signal improvement is dependent on buffer concentration as well as LC separation of the matrix components. The application of LC separation alone was not effective in addressing suppression effects when characterizing complex matrix samples. Overloading of the LC column by matrix components was found to significantly contribute to analyte-matrix co-elution and suppression of signal. This signal suppression effect can be efficiently compensated by 2D LC (LC-LC) separation techniques. The effectiveness of buffers and LC separation in improving signal correlation between standard and matrix samples is discussed.

Buffers↗
PubMed2004

Effects of seeding procedures and water quality on recovery of Cryptosporidium oocysts from stream water by using U.S. Environmental Protection Agency Method 1623.

U.S. Environmental Protection Agency method 1623 is widely used to monitor source waters and drinking water supplies for Cryptosporidium oocysts. Matrix spikes, used to determine the effect of the environmental matrix on the method's recovery efficiency for the target organism, require the collection and analysis of two environmental samples, one for analysis of endemic oocysts and the other for analysis of recovery efficiency. A new product, ColorSeed, enables the analyst to determine recovery efficiency by using modified seeded oocysts that can be differentiated from endemic organisms in a single sample. Twenty-nine stream water samples and one untreated effluent sample from a cattle feedlot were collected in triplicate to compare modified seeding procedures to conventional seeding procedures that use viable, unmodified oocysts. Significant negative correlations were found between the average oocyst recovery and turbidity or suspended sediment; this was especially apparent in samples with turbidities greater than 100 nephelometric turbidity units and suspended sediment concentrations greater than 100 mg/liter. Cryptosporidium oocysts were found in 16.7% of the unseeded environmental samples, and concentrations, adjusted for recoveries, ranged from 4 to 80 oocysts per 10 liters. Determining recovery efficiency also provided data to calculate detection limits; these ranged from <2 to <215 oocysts per 10 liters. Recoveries of oocysts ranged from 2.0 to 61% for viable oocysts and from 3.0 to 59% for modified oocysts. The recoveries between the two seeding procedures were highly correlated (r = 0.802) and were not significantly different. Recoveries by using modified oocysts, therefore, were comparable to recoveries by using conventional seeding procedures.

Animals↗
PubMed2006

The mechanical behaviour of chondrocytes predicted with a micro-structural model of articular cartilage.

The integrity of articular cartilage depends on the proper functioning and mechanical stimulation of chondrocytes, the cells that synthesize extracellular matrix and maintain tissue health. The biosynthetic activity of chondrocytes is influenced by genetic factors, environmental influences, extracellular matrix composition, and mechanical factors. The mechanical environment of chondrocytes is believed to be an important determinant for joint health, and chondrocyte deformation in response to mechanical loading is speculated to be an important regulator of metabolic activity. In previous studies of chondrocyte deformation, articular cartilage was described as a biphasic material consisting of a homogeneous, isotropic, linearly elastic solid phase, and an inviscid fluid phase. However, articular cartilage is known to be anisotropic and inhomogeneous across its depth. Therefore, isotropic and homogeneous models cannot make appropriate predictions for tissue and cell stresses and strains. Here, we modelled articular cartilage as a transversely isotropic, inhomogeneous (TI) material in which the anisotropy and inhomogeneity arose naturally from the microstructure of the depth-dependent collagen fibril orientation and volumetric fraction, as well as the chondrocyte shape and volumetric fraction. The purpose of this study was to analyse the deformation behaviour of chondrocytes using the TI model of articular cartilage. In order to evaluate our model against experimental results, we simulated indentation and unconfined compression tests for nominal compressions of 15%. Chondrocyte deformations were analysed as a function of location within the tissue. The TI model predicted a non-uniform behaviour across tissue depth: in indentation testing, cell height decreased by 43% in the superficial zone and between 11 and 29% in the deep zone. In unconfined compression testing, cell height decreased by 32% in the superficial zone, 25% in the middle, and 18% in the deep zones. This predicted non-uniformity is in agreement with experimental studies. The novelty of this study is the use of a cartilage material model accounting for the intrinsic inhomogeneity and anisotropy of cartilage caused by its microstructure.

Animals↗
PubMed2000

Integrating the MAP kinase signal into the G1 phase cell cycle machinery.

Growth factors and the extracellular matrix provide the environmental cues that control the proliferation of most cell types. The binding of growth factors and matrix proteins to receptor tyrosine kinases and integrins, respectively, regulates several cytoplasmic signal transduction cascades, among which activation of the mitogen-activated protein kinase cascade, ras --> Raf --> MEK --> ERK, is perhaps the best characterized. Curiously, ERK activation has been associated with both stimulation and inhibition of cell proliferation. In this review, we summarize recent studies that connect ERK signaling to G1 phase cell cycle control and suggest that the cellular response to an ERK signal depends on both ERK signal intensity and duration. We also discuss studies showing that receptor tyrosine kinases and integrins differentially regulate the ERK signal in G1 phase.

Animals↗
PubMed2000

Effect of lead, cadmium and zinc on the activity of enamel matrix proteinases in vitro.

Environmental contamination with heavy metals leads to their uptake by the body. Dental tissues are known to harbor metals in concentrations related to the exposure at the time of dentin or enamel formation. Several enzymes involved in the metabolism of extracellular matrix components have been shown to be inhibited by excess metal ions. Enamel matrix proteinases seem to play a central role in the maturation of dental enamel, and inhibition of these enzymes by metals could interfere with amelogenesis. We have investigated the effect of lead, cadmium and zinc on the activity of enamel matrix proteinases using a colorimetric assay, casein and gelatin zymography, and an assay of enamel protein degradation in vitro. All three metals inhibited the proteolysis, as shown by the three methods employed, in concentrations as low as 110 microM. This study showed that contaminant metals can inhibit proteinolysis when a crude enamel extract containing enamel proteases is tested in vitro. Therefore, the presence of heavy metals in enamel matrix could interfere with amelogenesis due to alteration in normal proteolysis.

Amelogenesis↗
PubMed2006

Discrimination and characterization of environmental strains of Escherichia coli by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS).

A rapid and reliable bacterial source tracking (BST) method is essential to counter risks to human health posed by fecal contamination of surface waters. Genetic fingerprinting methods, such as repetitive sequence based-PCR (rep-PCR), have shown promise as BST tools but are time-consuming and labor-intensive. In this work, we investigate the ability of MALDI-TOF-MS to characterize and discriminate between closely related environmental strains of Escherichia coli and to classify them according to their respective sources. We compared the performance of a rapid MALDI-TOF-MS-based method to a commonly used rep-PCR-based method that employs the BOX-A1R primer. Among the criteria evaluated were repeatability and the ability of each method to group E. coli isolates according to their respective sources. Our data suggest that the MALDI-TOF-MS-based approach has a lower repeatability level compared to rep-PCR but offers an improved ability to correctly assign E. coli isolates to specific source groups. In addition, we have identified five biomarkers that appear conserved among avian species. We conclude that MALDI-TOF-MS may represent a promising, novel and rapid approach to addressing the problem of fecal contamination of surface waters and warrants further investigation.

Animals↗
PubMed2000

Fibronectin and its fragments increase with degeneration in the human intervertebral disc.

STUDY DESIGN: This laboratory-based experiment correlates fibronectin content of intervertebral disc with a morphologic grade of degeneration. OBJECTIVES: To correlate the fibronectin content of the anulus fibrosus and nucleus pulposus with a gross morphologic grade of disc degeneration, and to determine the molecular size of the extractable fibronectin. SUMMARY OF BACKGROUND DATA: Intervertebral disc degeneration increases with age and can lead to low back pain. Fibronectin helps to organize the extracellular matrix and provides environmental cues by interaction with cell surface integrins. In other tissues, its synthesis is elevated in response to injury. Fibronectin fragments can stimulate cells to produce metalloproteases and cytokines and inhibit matrix synthesis. METHODS: In this study, 17 anuli fibrosis and 18 nuclei pulposus from 11 spines were graded by Thompson's gross morphologic scale. Fibronectin was sequentially extracted with 4 mol/L guanidine hydrochloride and trypsin, and then quantitated by enzyme-linked immunoassay. The size of extractable fibronectin was determined by Western blot analyses. RESULTS: The fibronectin content of the disc increased with grade and was significantly elevated between Grades 3 and 4. The percentage of extractable fibronectin varied widely, but it was more extractable from the nucleus. In both the nucleus and anulus, 30% to 40% of the extractable fibronectin existed as fragments. Many of the fragments contained functional heparin or collagen-binding sites. CONCLUSIONS: Fibronectin is elevated in degenerated discs and frequently present as fragments. Elevated levels of fibronectin suggest that disc cells are responding to the altered environment. Fibronectin fragments resulting from normal or enhanced proteolytic activity could be a mechanism that induces the cell to degrade the matrix further.

Adolescent↗
PubMed2005

Extinction in relation to demographic and environmental stochasticity in age-structured models.

The demographic variance of an age-structured population is defined. This parameter is further split into components generated by demographic stochasticity in each vital rate. The applicability of these parameters are investigated by checking how an age-structured population process can be approximated by a diffusion with only three parameters. These are the deterministic growth rate computed from the expected projection matrix and the environmental and demographic variances. We also consider age-structured populations where the fecundity at any stage is either zero or one, and there is neither environmental stochasticity nor dependence between individual fecundity and survival. In this case the demographic variance is uniquely determined by the vital rates defining the projection matrix. The demographic variance for a long-lived bird species, the wandering albatross in the southwestern part of the Indian Ocean, is estimated. We also compute estimates of the age-specific contributions to the total demographic variance from survival, fecundity and the covariance between survival and fecundity.

Age Factors↗
PubMed1996

The Impact of Environmental Variation on Demographic Convergence of Leslie Matrix Population Models: An Assessment Using Lyapunov Characteristic Exponents

In a constant environment, the rate of convergence of a density-independent Leslie matrix model to stable age distribution is determined by the damping ratio (the ratio of the absolute magnitudes of the first and second eigenvalues of the projection matrix). In a stochastic environment, the difference between the first two Lyapunov exponents is known to be analogous to the logarithm of the damping ratio, but there has been no systematic investigation of the consequences of enviromnental variation on convergence rates. In this study, the Lyapunov spectrum has been calculated for a wide variety of density-independent projection matrices subject to random variations in vital rates. This allows the impact of these random variations on convergence rates to be assessed. For rapidly convergent life histories, stochastic variation leads to a decrease in convergence rate. For life histories which are slow to converge, stochastic variation speeds up convergence. These effects are, however, relatively minor, and the value of the damping ratio for the mean matrix is a good predictor of the damping ratio in a stochastic environment. Consequently, when only an approximate indication of convergence rates is needed, the damping ratio for the mean projection matrix gives a very good guide. Detailed calculations of the Lyapunov spectrum would only be necessary to make comparisons between similar life histories or if very precise information on convergence rates were needed.

Journal Article↗
PubMed2003

Matrix metalloproteinases and endometriosis.

Retrograde menstruation represents a plausible explanation for the development of most cases of endometriosis; nevertheless, additional factors must contribute to the development of disease in only 10 to 20% of women. The discriminating factor(s) in determining the development of active endometriosis probably involves a complex array of potentially interactive influences including steroid exposure, immunological disturbances, genetic predisposition, and, perhaps, environmental toxin exposure. Matrix metalloproteinases (MMPs), enzymes that mediate normal tissue turnover including endometrial breakdown at menstruation, appear to be involved in the invasive establishment of the disease. In addition, several MMPs appear to be inappropriately expressed in the endometrium of women with this disease in association with a reduced sensitivity to progesterone. Altered regulation of endometrial MMP expression in response to steroids may represent a mechanism linking the invasive potential of refluxed endometrium to the establishment of this disease only in certain women.

Animals↗