The attack on the World Trade Center (WTC) created an acute environmental disaster of enormous magnitude. This study characterizes the environmental exposures resulting from destruction of the WTC and assesses their effects on health. Methods include ambient air sampling; analyses of outdoor and indoor settled dust; high-altitude imaging and modeling of the atmospheric plume; inhalation studies of WTC dust in mice; and clinical examinations, community surveys, and prospective epidemiologic studies of exposed populations. WTC dust was found to consist predominantly (95%) of coarse particles and contained pulverized cement, glass fibers, asbestos, lead, polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and polychlorinated furans and dioxins. Airborne particulate levels were highest immediately after the attack and declined thereafter. Particulate levels decreased sharply with distance from the WTC. Dust pH was highly alkaline (pH 9.0-11.0). Mice exposed to WTC dust showed only moderate pulmonary inflammation but marked bronchial hyperreactivity. Evaluation of 10,116 firefighters showed exposure-related increases in cough and bronchial hyperreactivity. Evaluation of 183 cleanup workers showed new-onset cough (33%), wheeze (18%), and phlegm production (24%). Increased frequency of new-onset cough, wheeze, and shortness of breath were also observed in community residents. Follow-up of 182 pregnant women who were either inside or near the WTC on 11 September showed a 2-fold increase in small-for-gestational-age (SGA) infants. In summary, environmental exposures after the WTC disaster were associated with significant adverse effects on health. The high alkalinity of WTC dust produced bronchial hyperreactivity, persistent cough, and increased risk of asthma. Plausible causes of the observed increase in SGA infants include maternal exposures to PAH and particulates. Future risk of mesothelioma may be increased, particularly among workers and volunteers exposed occupationally to asbestos. Continuing follow-up of all exposed populations is required to document the long-term consequences of the disaster.
 Arsenic concentrations measured by graphite furnace atomic absorption range from < 5 to 900 mg/L in groundwater pumped from 6000 wells within a 25 km 2 area of Bangladesh. The proportion of wells that exceed the Bangladesh standard for drinking water of 50 mg/L arsenic increases with depth from 25% between 8 and 10 m to 75% between 15 and 30 m, then declines gradually to less than 10% at 90 m. Some villages within the study area do not have a single well that meets the standard, while others have wells that are nearly all acceptable. In contrast to the distribution of arsenic in the 8-30 m depth range which does not follow any obvious geological feature, the arsenic content of groundwater associated with relatively oxic Pleistocene sand deposits appears to be consistently low. The depth of drilling necessary to reach these low-As aquifers ranges from 30 to 120 m depth within the study area.
Abstract. The spatio-temporal distribution of vegetation is a fundamental component of the urban environment that can be quanti® ed using multispectral imagery. However, spectral heterogeneity at scales comparable to sensor resolution limits the utility of conventional hard classi® cation methods with multispectral re¯ectance data in urban areas. Spectral mixture models may provide a physically based solution to the problem of spectral heterogeneity. The objective of this study is to examine the applicability of linear spectral mixture models to the estimation of urban vegetation abundance using Landsat Thematic Mapper (TM) data. The inherent dimensionality of TM imagery of the New York City area suggests that urban re¯ectance measurements may be described by linear mixing between high albedo, low albedo and vegetative endmembers. A threecomponent linear mixing model provides stable, consistent estimates of vegetation fraction for both constrained and unconstrained inversions of three diVerent endmember ensembles. Quantitative validation using vegetation abundance measurements derived from high-resolution (2 m) aerial photography shows agreement to within fractional abundances of 0.1 for vegetation fractions greater than 0.2. In contrast to the Normalised DiVerence Vegetation Index (NDVI), vegetation fraction estimates provide a physically based measure of areal vegetation abundance that may be more easily translated to constraints on physical quantities such as vegetative biomass and evapotranspiration.
Vitamin A deficiency in the mouse results in an arrest in the progression of undifferentiated spermatogonia to differentiating spermatogonia. The supplement of retinol to vitamin-A-deficient mice reinitiates spermatogenesis in a synchronous manner throughout the testes. It is unclear whether the effects of retinoids are the result of a direct action on germ cells or are indirectly mediated through Sertoli cells. The expression of Stimulated by retinoic acid gene 8 (Stra8), which is required for spermatogenesis, is directly related to the availability of retinoic acid (RA). Analysis of gene expression by microarrays revealed moderate levels of Stra8 transcript in gonocytes and high levels in A and B spermatogonia. Stra8 mRNA levels were greatly reduced or absent in germ cells once they entered meiosis. This study examined the effect of retinoic acid on cultured neonatal testes and isolated gonocytes/spermatogonia in vitro. THY1(+) and KIT(+) germ cells were isolated by magnetic-activated cell sorting from the testes of mice of different ages. Isolated germ cells were cultured and treated with either vehicle (ethanol) or RA without feeder cells. We found that 1) Stra8 is predominantly expressed in premeiotic germ cells, 2) RA stimulates gonocyte DNA replication and differentiation in cultured neonatal testes, 3) in the absence of feeder cells, RA directly induces the transition of undifferentiated spermatogonia to differentiating spermatogonia by stimulating Stra8 and Kit gene expression, 4) RA dramatically stimulates Stra8 expression in undifferentiated spermatogonia but has a lesser impact in differentiating spermatogonia, 5) endogenous Stra8 gene expression is higher in differentiating spermatogonia than in undifferentiated spermatogonia and could mediate the RA effects on spermatogonial maturation, and 6) RA stimulates a group of genes involved in the metabolism, storage, transport, and signaling of retinoids.
The application of microarray technology to the study of mammalian organogenesis can provide greater insights into the steps necessary to elicit a functionally competent tissue. To this end, a temporal profile of gene expression was generated with the purpose of identifying changes in gene expression occurring within the developing male and female embryonic gonad. Gonad tissue was collected from mouse embryos at 11.5, 12.5, 14.5, 16.5, and 18.5 days postcoitum (dpc) and relative steady-state levels of mRNA were determined using the Affymetrix MGU74v2 microarray platform. Statistical analysis produced 3693 transcripts exhibiting differential expression during male and/or female gonad development. At 11.5 dpc, the gonad is morphologically indifferent, but at 12.5 dpc, transitions to a male or female phenotype are discernible by the appearance of testicular cords. A number of genes are expressed during this period and many share similar expression profiles in both sexes. As expected, the expression of two well-known sex determination genes, specifically Sry and Sox9, is unique to the testis. Beyond 12.5 dpc, differential gene expression becomes increasingly evident as the male and female tissue morphologically and physiologically diverges. This is evident by two unique waves of transcriptional activity occurring after 14.5 dpc in the male and female. With this study, a large number of transcripts comprising the murine transcriptome can be examined throughout male and female embryonic gonad development and allow for a more complete description of gonad differentiation and development.
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