Quantification of 3-dimensional structure and properties of flocculated natural suspended sediment.

Natural sediment flocs are fragile and highly heterogeneous aggregates of biogenic and minerogenic material typically with high porosity and low density. In aquatic environments dominated by fine, cohesive or mixed sediments they can dominate suspended sediment flux. Consequently, monitoring and modelling the behaviour, transport and distribution of flocs is very important for many aquatic industries, maintenance of waterways and conservation and management of aquatic waterbodies. Mathematical models that predict the behaviour of flocs rely on the accurate assessments of the size, shape, density, porosity and fractal dimension of flocs. These inherently 3-dimensional (3D) characteristics are typically derived from 2-dimensional (2D) data, largely due to the challenges associated with sampling, capturing, imaging and quantifying these fragile aggregates. We have developed new volumetric microscopy techniques which can quantify 3D internal and external structures and characteristics of sediment flocs. Here, these techniques were applied to quantify the 3D size (volume), shape and fractal dimension of natural and artificial sediment flocs and compare them to standard 2D approaches. Our study demonstrates that 2D approaches are under-estimating shape complexity and over-estimating the size and mass settling flux of flocs by up to two orders of magnitude, and the discrepancy between 2D and 3D is most marked for natural, organic rich macroflocs. Our study has significant implications for estimations of sediment flux at local to global scales within in aquatic environments. These new data and approaches offer the potential to improve the current parameterisation of sediment transport models and to improve the accuracy of current field-monitoring techniques.

Chondrocyte dedifferentiation increases cell stiffness by strengthening membrane-actin adhesion.

OBJECTIVE: Chondrocyte dedifferentiation is known to influence cell mechanics leading to alterations in cell function. This study examined the influence of chondrocyte dedifferentiation in monolayer on cell viscoelastic properties and associated changes in actin organisation, bleb formation and membrane-actin cortex interaction. METHOD: Micropipette aspiration was used to estimate the viscoelastic properties of freshly isolated articular chondrocytes and the same cells after passage in monolayer. Studies quantified the cell membrane-actin cortex adhesion by measuring the critical pressure required for membrane detachment and bleb formation. We then examined the expression of ezrin, radixin and moesin (ERM) proteins which are involved in linking the membrane and actin cortex and combined this with theoretical modelling of bleb dynamics. RESULTS: Dedifferentiated chondrocytes at passage 1 (P1) were found to be stiffer compared to freshly isolated chondrocytes (P0), with equilibrium modulus values of 0.40 and 0.16 kPa respectively. The critical pressure increased from 0.59 kPa at P0 to 0.74 kPa at P1. Dedifferentiated cells at P1 exhibited increased cortical F-actin organisation and increased expression of total and phosphorylated ERM proteins compared to cells at P0. Theoretical modelling confirmed the importance of membrane-actin cortex adhesion in regulating bleb formation and effective cellular elastic modulus. CONCLUSION: This study demonstrates that chondrocyte dedifferentiation in monolayer strengthens membrane-actin cortex adhesion associated with increased F-actin organisation and up-regulation of ERM protein expression. Thus dedifferentiated cells have reduced susceptibility to bleb formation which increases cell modulus and may also regulate other fundamental aspects of cell function such as mechanotransduction and migration.

Chlamydia trachomatis IgG3 seropositivity is associated with gastroschisis.

OBJECTIVE: To investigate the association between Chlamydia trachomatis (CT) infection seropositivity and gastroschisis. STUDY DESIGN: In this case-control study we enrolled pregnant women either prenatally diagnosed with gastroschisis (cases, n=33) or with a normal ultrasound (controls, n=66). Both groups attended the University of Utah's Maternal Fetal Medicine Diagnostic Center for their diagnostic ultrasound or because of a community obstetrician referral. Participants completed a structured interview on potential risk factors. Anti-CT immunoglobulin (IgG)1 and IgG3 were measured by a CT elementary body enzyme-linked immunosorbent assay. RESULT: Median age at sexual debut was lower and reported sexual partner number higher in cases compared with controls. Risk factors for gastroschisis included having ⩾ 3 sexual partners (odds ratio (OR)=3.3, 95% CI 1.2, 9.4), change in partner from the previous pregnancy (OR=3.6, 95% CI 0.9, 13.9) and anti-CT IgG3 seropositivity (age-adjusted OR=3.9, 95% CI: 1.1, 13.2). CONCLUSION: Anti-CT IgG3 seropositivity was associated with greater than a threefold risk for gastroschisis.

Prevalence of variants in methylenetetrahydrofolate reductase and the severity of pulmonary vascular disease.

Pulmonary hypertension is a serious disease associated with constriction, cellular proliferation, inflammation, and in situ thrombosis of the small vessels of the lung. Some studies suggest that homozygous 677TT variants and compound heterozygous 677CT/1298AC variants in methylenetetrahydrofolate reductase may increase the risk for systemic vascular disease. We sought to determine the prevalence of variants in methylenetetrahydrofolate reductase in patients with pulmonary hypertension, and whether homozygous or compound heterozygous variants are associated with an increased severity of disease. The medical records of patients with pulmonary hypertension were retrospectively reviewed to identify 105 patients who were evaluated for variants in methylenetetrahydrofolate reductase. The frequency of the minor allele 677C > T was 0.352 and the frequency of the minor allele 1298A > C was 0.295. The number of patients who were homozygous 677TT, homozygous 1298CC or compound heterozygous 677CT/1298AC was similar to the number of control patients with corresponding variants in a meta-analysis of studies. Patients with homozygous or compound heterozygous variants had a significantly higher ratio of pulmonary to systemic vascular resistance (0.75 ± 0.07 vs. 0.56 ± 0.04, p = 0.019) during baseline heart catheterization. Twenty-five of 61 patients without, and 28 of 44 patients with, homozygous or compound heterozygous variants had moderate to severe disease (p = 0.030). Variants in methylenetetrahydrofolate reductase are common in the general population and in patients with pulmonary hypertension. It is unlikely that these variants cause pulmonary vascular disease; however, they may influence the progression or severity of disease.

Barriers to prenatal detection of congenital heart disease: a population-based study.

OBJECTIVE: To evaluate the extent and determinants of missed prenatal detection of congenital heart disease (CHD) in a population-based setting. METHODS: This was a retrospective cohort study of cases with CHD, excluding minor defects, identified between 1997 and 2007 by a statewide surveillance program. We examined a comprehensive list of potential risk factors for which data were available in the surveillance database from abstracted medical charts. We analyzed the association of fetal, maternal and encounter factors with 1) whether a prenatal ultrasound was performed and 2) prenatal detection of CHD. RESULTS: CHD was detected prenatally in only 39% of 1474 cases, with no improvement in detection rate over the 10-year period. Among the 97% (n = 1431) of mothers who underwent one or more ultrasound examinations, 35% were interpreted as abnormal; fetal echocardiography was performed in 27% of the entire cohort. Maternal and encounter factors increasing the adjusted odds of prenatal detection included: family history of CHD (OR, 4.3 (95% CI, 1.9-9.9)), presence of extracardiac defects (OR, 2.7 (95% CI, 1.9-3.9)) and ultrasound location i.e. high risk clinic vs clinic (OR, 2.1 (95% CI, 1.3-3.1)). Defects that would be expected to have an abnormal outflow-tract view were missed more often (64%) than were those that would be expected to have an abnormal four-chamber view (42%). CONCLUSION: The majority of CHD cases over the 10-year study period were missed prenatally and detection rates did not increase materially during that time. The failure to detect CHD prenatally was related to encounter characteristics, specifically involving screening ultrasound examinations, which may be targeted for improvement.

Organic extract of tire debris causes localized damage in the plasma membrane of human lung epithelial cells.

The potential toxicity of tire debris organic extracts on human alveolar epithelial cells (A549) was investigated. We analysed time- and dose dependent modifications produced on plasma membrane molecular composition and on lipid microdomains expression (caveolae and lipid rafts) that represent specific signalling platforms. Cells were exposed to increasing organic extract concentrations (10, 60 and 75mug/ml) for 24, 48 and 72h. An up to three fold dose and time dependent increase in specific protein markers of lipid microdomains was found, suggesting a corresponding increase in signalling platforms. Since the total pool of these plasma membrane markers was unchanged, we supposed that these proteins were translocated within the plasma membrane as to assemble the newly formed lipid microdomains. Despite no major modifications in lipid bilayer composition, a time- and dose dependent toxic effect was documented at 48h of exposure by an increase of cells positive to Trypan Blue assay. After 48h a dose dependent increase in the cell medium of the cytosolic enzyme lactate dehydrogenase was also observed, indicating greater damage of the plasma membrane as prenecrotic sign. The overall ultrastructural morphology of the plasma membrane of treated cells was not greatly modified, suggesting that organic extracts from tire debris cause focalized discontinuities on cell surfaces.

Changes in the composition of detergent-resistant membrane domains of cultured neurons following protein kinase C activation.

Changes in the composition of cell fractions, and in particular of detergent-resistant membranes (DRM) isolated from cultured rat cerebellar granule cells, were taken as possible changes in lipid raft composition during a signal transduction event. After activation of protein kinase C (PKC) with phorbol esters (PMA) or glutamate, the content of PKC and of proteins highly enriched (GAP43, Fyn, and PrP(c)) or not (MARCKS) in DRM was followed. PKC activation strongly increased its association with membranes (from 2% to 75%), causing its enrichment within DRM; the substrate GAP43, enriched in DRM, remained membrane associated, but its proportion in DRM dramatically decreased (from about 40% to 2.5%), suggesting its shift from raft to nonraft membranes, possibly as a consequence of phosphorylation by PKC. The distribution of Fyn and PrP(c) (DRM-enriched) and of MARCKS (present mainly outside DRM) did not change. PKC activation was followed by an increase of GAP43 and MARCKS phosphorylation (about 7- and 8-fold, respectively). Noteworthy was that, after cell treatment with the lipid raft-disrupting drug methyl-beta-cyclodextrin, PKC activation occurred normally, followed by MARCKS phosphorylation, but GAP43 phosphorylation did not occur. Taken altogether, these data suggest that the integrity of lipid rafts is necessary for PKC to affect GAP43 and catalyze its phosphorylation.

Congenital heart defects, maternal febrile illness, and multivitamin use: a population-based study.

We assessed the relation between febrile illness during pregnancy and cardiac defects in the offspring in a population-based case-control study in metropolitan Atlanta. Case infants (905) with cardiac defects were actively ascertained from multiple sources. Control infants (3,029) were infants without birth defects who were selected from birth certificates by stratified random sampling. We compared those whose mothers reported febrile illness from 1 month before pregnancy through the third month of pregnancy with those whose mothers reported no illness during the same period. Febrile illness was positively associated with the occurrence of heart defects in the offspring (odds ratio [OR] = 1.8; 95% confidence interval = 1.4-2.4). When influenzalike illness was the reported febrile illness, the OR was 2.1 (95% confidence interval = 0.8-5.5). The association with febrile illness was strongest for tricuspid atresia (OR = 5.2), left obstructive defects (OR = 2.7), transposition of the great arteries (OR = 1.9), and ventricular septal defects (OR = 1.8). These ORs were generally lower among mothers who used multivitamins during the periconceptional period.

Vitamin A and cardiac outflow tract defects.

To assess the relationship between maternal intake of vitamin A and cardiac outflow tract defects, we examined data from a population-based case-control study among liveborn infants born from 1987 through 1989 to mothers residing in the Baltimore-Washington area. Case infants (126) had a nonsyndromic cardiac outflow tract defect. Control infants (679) did not have birth defects and were a stratified random sample of liveborn infants from the same area. The main exposure was average daily maternal intake of retinol and provitamin A carotenoids from foods and supplements during the year before conception. Compared with an average intake of less than 10,000 IU, retinol intake of 10,000 IU or more from supplements was associated with a ninefold increased risk for transposition of the great arteries (odds ratio = 9.2; 95% confidence interval = 4.0-21.2), but not for outflow tract defects with normally related arteries (odds ratio = 0.8; 95% confidence interval = 0.1-6.6). Similar intakes of carotenoids and dietary retinol were not associated with an increased risk for either type of outflow tract defect.

[Prevalence of methylenetetrahydrofolate reductase (MTHFR) gene polymorphism (C677T) in the Hungarian population]. / A metiléntetrahidrofolát-reduktáz (MTHFR) gén polimorfizmusának (C677T) magyarországi gyakorisága.

MTHFR encodes a critical enzyme in folate and homocysteine metabolism and the C677T allele of the MTHFR gene has some association with an increased risk for neural-tube defects and for adult cardiovascular diseases. As part of an international collaborative study the prevalence of C677T homozygous genotype was 11.1% while the frequency of C677T heterozygous condition was 45.2% in the Hungarian neonate sample. These findings underscore the clinical importance of the C677T variant in the Hungarian population and urge population-based prevention of conditions related to such gene.

Maternal prepregnancy weight and congenital heart defects in offspring.

To determine the relation between having an infant with a major heart defect and a mother's prepregnancy weight, we compared 1,049 Atlanta-area women who gave birth to liveborn or stillborn infants, each with a major heart defect, with 3,029 Atlanta-area women who gave birth to infants without birth defects. The infants of control women were randomly selected from birth certificates and were frequency-matched to the case group by race, birth hospital, and birth period from 1968 through 1980. After excluding diabetic mothers and adjusting for potential confounders, compared with average-weight women (body mass index 19.9--22.7), we found that underweight women (body mass index <16.5) were less likely to have a child with a major isolated heart defect [odds ratio (OR) = 0.64; 95% confidence interval (CI) = 0.43--0.97], whereas the OR was elevated among overweight or obese women (body mass index >26) (OR = 1.36; 95% CI = 0.95--1.93). Using average-weight women who did not take periconceptional multivitamins as the reference group, periconceptional multivitamin use was associated with a reduced OR for isolated heart defects among average-weight women (OR = 0.61, 95% CI = 0.36--0.99) and underweight women but not among overweight or obese women (OR = 1.69, 95% CI = 0.69--3.84).

Commentary: facing the challenge of gene-environment interaction: the two-by-four table and beyond.

As a result of the Human Genome Project, epidemiologists can study thousands of genes and their interaction with the environment. The challenge is how to best present and analyze such studies of multiple genetic and environmental factors. The authors suggest emphasizing the fundamental core of gene-environment interaction-the separate assessment of the effects of individual and joint risk factors. In the simple analysis of one genotype and an exposure (both dichotomous), such study can be summarized in a two-by-four table. The advantages of such a table for data presentation and analysis are many: The table displays the data efficiently and highlights sample size issues; it allows for evaluation of the independent and joint roles of genotype and exposure on disease risk; and it emphasizes effect estimation over model testing. Researchers can easily estimate relative risks and attributable fractions and test different models of interaction. The two-by-four table is a useful tool for presenting, analyzing, and synthesizing data on gene-environment interaction. To highlight the role of gene-environment interaction in disease causation, the authors propose that the two-by-four table is the fundamental unit of epidemiologic analysis.

Mortality associated with congenital heart defects in the United States: trends and racial disparities, 1979-1997.

BACKGROUND: Surgical series and some population-based studies have documented a decrease in mortality from heart defects. Recent population-based data for the United States are lacking, however. We examined population-based data for patterns, time trends, and racial differences of mortality from heart defects for the United States from 1979 through 1997. METHODS AND RESULTS: We examined the multiple-cause mortality files compiled by the National Center for Health Statistics of the CDC from all death certificates filed in the United STATES: From these data, we derived death rates (deaths per 100 000 population) by the decedent's age, race, year of death, and heart defect type. We also analyzed age at death as an indirect indicator of survival. From 1979 through 1997, mortality from heart defects (all ages) declined 39%, from 2.5 to 1.5 per 100 000 population; among infants, the decline was 39%, or 2.7% per year. In 1995 to 1997, heart defects contributed to 5822 deaths per year. Of these deaths, 51% were among infants and 7% among children 1 to 4 years old. Mortality was on average 19% higher among blacks than among whites; this gap does not appear to be closing. Age at death increased for most heart defects, although less among blacks than among whites. CONCLUSIONS: Mortality from heart defects is declining in the United States, although it remains a major cause of death in infancy and childhood. Age at death is increasing, suggesting that more affected persons are living to adolescence and adulthood. The racial discrepancies should be investigated to identify opportunities for prevention.

On the symmetry of limb deficiencies among children with multiple congenital anomalies.

In humans, unpaired organs are placed in a highly ordered pattern along the left-right axis. As indicated by animal studies, a cascade of signaling molecules establish left-right asymmetry in the developing embryo. Some of the same genes are involved also in limb patterning. To provide a better insight into the connection between these processes in humans, we analysed the symmetry of limb deficiencies among infants with multiple congenital anomalies. The study was based on data collected by the International Clearinghouse for Birth Defects Monitoring Systems (ICBDMS). Registries of the ICBDMS provided information on infants who, in addition to a limb deficiency, also had at least one major congenital anomaly in other organ systems. We reviewed 815 such cases of which 149 cases (18.3 %) were syndromic and 666 (81.7 %) were nonsyndromic. The comparisons were made within the associated limb deficiencies, considering the information on symmetry, using a comparison group with malformations associated not involved in the index association. Among the non-syndromic cases, the left-right distribution of limb deficiencies did not differ appreciably between limb deficiency subtypes (e.g., preaxial, transverse, longitudinal). The left-right distribution of limb anomalies did not differ among most types of non-limb anomalies, though a predominance of left-sided limb deficiencies was observed in the presence of severe genital defects - odds ratio [OR], 2.6; 95 % CI, 1.1-6.4). Limb deficiencies (LDs) were more often unilateral than bilateral when accompanied by gastroschisis (OR, 0.1) or axial skeletal defects (OR, 0.5). On the contrary, LDs were more often bilateral than unilateral when associated with cleft lip with or without cleft palate (OR, 3.9) or micrognathia (OR, 2.6). Specifically, we found an association between bilateral preaxial deficiencies and cleft lip, bilateral amelia with gastroschisis and urinary tract anomalies, and bilateral transverse deficiencies and gastroschisis and axial skeleton defects. Of 149 syndromic cases, 62 (41.6 %) were diagnosed as trisomy 18. Out of the 30 cases of trisomy 18 with known laterality, 20 cases were bilateral. In the remainder the right and left sides were equally affected. Also, in most cases (74.4 %) only the upper limbs were involved. In conclusion the left-right distribution of limb deficiencies among some non-limb anomalies may suggest a relationship between the development of the limb and the left-right axis of the embryo.

Racial and temporal variations in the prevalence of heart defects.

BACKGROUND: Documenting the prevalence and trends of congenital heart defects provides useful data for pediatric practice, health-care planning, and causal research. Yet, most population-based studies use data from the 1970s and 1980s. We sought to extend into more recent years the study of temporal and racial variations of heart defects occurrence in a well-defined population. METHODS: We used data from the Metropolitan Atlanta Congenital Defects Program, a population-based registry with active case ascertainment from multiple sources. Heart defects were identified among liveborn infants up to 1 year old, among stillborn infants, and among pregnancy terminations to mothers residing in metropolitan Atlanta. RESULTS: From 1968 through 1997, the registry ascertained 5813 major congenital heart defects among 937 195 infants, for a prevalence of 6.2 per 1000. The prevalence increased to 9.0 per 1000 births in 1995 through 1997. The prevalence of ventricular septal defects, tetralogy of Fallot, atrioventricular septal defects, and pulmonary stenosis increased, whereas that of transposition of the great arteries decreased. For some defects, prevalence and trends varied by race. CONCLUSIONS: The prevalence of congenital heart defects is increasing. Whereas most findings likely result from improved case ascertainment and reporting, others might be because of changes in the distribution of risk factors in the population. The basis of the racial variations is incompletely understood.

Infant mortality and congenital anomalies from 1950 to 1994: an international perspective.

STUDY OBJECTIVE: To provide an international perspective on the impact of congenital anomalies on infant mortality from 1950 to 1994. DESIGN: Population-based study based on data obtained from vital statistics reported to the World Health Organisation. SETTINGS: 36 countries from Europe, the Middle East, the Americas, Asia, and the South Pacific. RESULTS: On average, infant mortality declined 68.8 per cent from 1950 to 1994. In the countries studied, infant mortality attributable to congenital anomalies decreased by 33.4 per cent, although it recently increased in some countries in Central and Latin America and in Eastern Europe. Anomalies of the heart and of the central nervous system accounted for 48.9 per cent of infant deaths attributable to congenital anomalies. During 1990-1994, infant mortality attributable to congenital anomalies was inversely correlated to the per capita gross domestic product in the countries studied. At the same time, the proportion of infant deaths attributable to congenital malformations was directly correlated with the per capita gross domestic product. CONCLUSIONS: Congenital malformations account for an increasing proportion of infant deaths in both developed and developing countries. Infant mortality attributable to congenital anomalies is higher in poorer countries although as a proportion of infant deaths it is greater in wealthier countries. Conditions such as spina bifida, whose occurrence can be reduced through preventive strategies, still cause many infant deaths. The apparent increase of infant mortality because of congenital anomalies in some countries should be investigated to confirm the finding, find the causes, and provide prevention opportunities.

Limb defects associated with major congenital anomalies: clinical and epidemiological study from the International Clearinghouse for Birth Defects Monitoring Systems.

Although limb defects associated with other congenital anomalies are rarely studied, they may provide insights into limb development that may be useful for etiologic studies and public health monitoring. We pooled data from 11 birth defect registries that are part of the International Clearinghouse for Birth Defects Monitoring Systems. We identified 666 infants, born from 1983 through 1993, who had a non-syndromal limb defect plus at least one other major malformation (rate 12.9/100,000 population). We used observed/expected ratios and log-linear models to detect association patterns. We found that specific limb defects occurred with relatively distinct sets of malformations. Preaxial limb defects occurred more frequently with microtia, esophageal atresia, anorectal atresia, heart defects, unilateral kidney dysgenesis, and some axial skeleton defects; postaxial defects with hypospadias; transverse defects with craniofacial defects, micrognathia, ring constrictions, and muscular defects; intercalary defects with omphalocele; split hand/foot with encephalocele; and amelia with anorectal atresia, omphalocele, severe genitalia defects, unilateral kidney dysgenesis, gastroschisis, and ring constriction. Log-linear modeling identified higher order associations among some of these same malformations.

5,10-Methylenetetrahydrofolate reductase gene variants and congenital anomalies: a HuGE review.

The enzyme 5,10-methylenetetrahydrofolate reductase (MTHFR) is involved in folate metabolism. The MTHFR gene is located on chromosome 1 (1p36.3), and two common alleles, the C677T (thermolabile) allele and the A1298C allele, have been described. The population frequency of C677T homozygosity ranges from 1% or less among Blacks from Africa and the United States to 20% or more among Italians and US Hispanics. C677T homozygosity in infants is associated with a moderately increased risk for spina bifida (pooled odds ratio = 1.8; 95% confidence interval: 1.4, 2.2). Maternal C677T homozygosity also appears to be a moderate risk factor (pooled odds ratio = 2.0; 95% confidence interval: 1.5, 2.8). The A 1298C allele combined with the C677T allele also could be associated with an increased risk for spina bifida. Some data suggest that the risk for spina bifida associated with C677T homozygosity may depend on nutritional status (e.g., blood folate levels, intake of vitamins) or on the genotype of other folate-related genes (e.g., cystathionine-beta-synthase and methionine synthase reductase). Studies of the C677T allele in relation to oral clefts, Down syndrome, and fetal anticonvulsant syndrome either have yielded conflicting results or have not been yet replicated.