Determination of the bioaccessibility of chromium in Glasgow soil and the implications for human health risk assessment

The Unified Bioaccessibility Method (UBM), which simulates the fluids of the human gastrointestinal tract, was used to assess the oral bioaccessibility of Cr in 27 Glasgow soils. These included several contaminated with Cr(VI), the most toxic form of Cr, from the past disposal of chromite ore processing residue (COPR). The extraction was employed in conjunction with the subsequent determination of the bioaccessible Cr by ICP-OES and Cr(VI) by the diphenylcarbazide complexation colorimetric procedure. In addition, Cr(III)-containing species were determined by (i) HPLC-ICP-MS and (ii) ICP-OES analysis of gel electrophoretically separated components of colloidal and dissolved fractions from centrifugal ultrafiltration of extracts. Similar analytical procedures were applied to the determination of Cr and its species in extracts of the < 10 μm fraction of soils subjected to a simulated lung fluid test to assess the inhalation bioaccessibility of Cr.The oral bioaccessibility of Cr was typically greater by a factor of 1.5 in the ‘stomach’ (pH ~ 1.2) compared with the ‘stomach + intestine’ (pH ~ 6.3) simulation. On average, excluding two COPR-contaminated soil samples, the oral bioaccessibility (‘stomach’) was 5% of total soil Cr and, overall, similar to the soil Cr(VI) concentration. Chromium(VI) was not detected in the extracts, a consequence of pH- and soil organic matter-mediated reduction in the ‘stomach’ to Cr(III)-containing species, identified as predominantly Cr(III)-humic complexes. Insertion of oral bioaccessible fraction data into the SNIFFER human health risk assessment model identified site-specific assessment criteria (for residential land without plant uptake) that were exceeded by the soil total Cr (3680 mg kg^-1) and Cr(VI) (1485 mg kg^-1) concentration at only the most COPR-Cr(VI)-contaminated location. However, the presence of measurable Cr(VI) in the < 10 μm fraction of the two most highly Cr(VI)-contaminated soils demonstrated that inhalation of Cr(VI)-containing dust remains the most potentially harmful exposure route.     

Historical accumulation rates of mercury in four Scottish ombrotrophic peat bogs over the past 2000 years

The historical accumulation rates of mercury resulting from atmospheric deposition to four Scottish ombrotrophic peat bogs, Turclossie Moss (northeast Scotland), Flanders Moss (west-central), Red Moss of Balerno (east-central) and Carsegowan Moss (southwest), were determined via analysis of ²¹⁰Pb- and ¹⁴C-dated cores up to 2000 years old. Average pre-industrial rates of mercury accumulation of 4.5 and 3.7 μg m^− 2 y^− 1 were obtained for Flanders Moss (A.D. 1-1800) and Red Moss of Balerno (A.D. 800-1800), respectively. Thereafter, mercury accumulation rates increased to typical maximum values of 51, 61, 77 and 85 μg m^− 2 y^− 1, recorded at different times possibly reflecting local/regional influences during the first 70 years of the 20th century, at the four sites (TM, FM, RM, CM), before declining to a mean value of 27 ± 15 μg m^− 2 y^− 1 during the late 1990s/early 2000s. Comparison of such trends for mercury with those for lead and arsenic in the cores and also with direct data for the declining UK emissions of these three elements since 1970 suggested that a substantial proportion of the mercury deposited at these sites over the past few decades originated from outwith the UK, with contributions to wet and dry deposition arising from long-range transport of mercury released by sources such as combustion of coal. Confidence in the chronological reliability of these core-derived trends in absolute and relative accumulation of mercury, at least since the 19th century, was provided by the excellent agreement between the corresponding detailed and characteristic temporal trends in the ²⁰⁶Pb/²⁰⁷Pb isotopic ratio of lead in the ²¹⁰Pb-dated Turclossie Moss core and those in archival Scottish Sphagnum moss samples of known date of collection. The possibility of some longer-term loss of volatile mercury released from diagenetically altered older peat cannot, however, be excluded by the findings of this study.     

Two modes of transvection: enhancer action in trans and bypass of a chromatin insulator in cis

Ed Lewis introduced the term "transvection" in 1954 to describe mechanisms that can cause the expression of a gene to be sensitive to the proximity of its homologue. Transvection since has been reported at an increasing number of loci in Drosophila, where homologous chromosomes are paired in somatic tissues, as well as at loci in other organisms. At the Drosophila yellow gene, transvection can explain intragenic complementation involving the yellow2 allele (y2). Here, transvection was proposed to occur by enhancers of one allele acting in trans on the promoter of a paired homologue. In this report, we describe two yellow alleles that strengthen this model and reveal an unexpected, second mechanism for transvection. Data suggest that, in addition to enhancer action in trans, transvection can occur by enhancer bypass of a chromatin insulator in cis. We propose that bypass results from the topology of paired genes. Finally, transvection at yellow can occur in genotypes not involving y2, implying that it is a feature of yellow itself and not an attribute of one particular allele.     

Elevated-temperature deformation properties of a HfC modified Ti-48Al-2Mn-2Nb matrix particulate composite

Rapid solidification techniques in combination with HIPing have been used to produce Ti-48Al-2Mn-2Nb and a Ti-48Al-2Mn-2Nb+15 wt% HfC composite. While the composite does contain several second phases within the + ₂ matrix, none was identified to be HfC. The elevated-temperature properties were determined by constant velocity compression and constant load tensile testing in air between 1000 and 1173 K. Such testing indicated that the elevated temperature strengths of the HfC-modified aluminide was superior to those of the unreinforced matrix with the best 1100 K temperature slow strain rate properties for both materials being achieved after high-temperature annealing prior to testing. Examination of the microstructures after deformation in combination with the measured stress exponents and activation energies suggest that creep resistance of the HfC-modified form is due to solid-solution strengthening from carbon and hafnium rather than the presence of second phases.     

Dinor-oxo-phytodienoic acid: a new hexadecanoid signal in the jasmonate family

Jasmonic acid and its precursors are potent regulatory molecules in plants. We devised a method for the simultaneous extraction of these compounds from plant leaves to quantitate changes in the levels of jasmonate family members during health and on wounding. During our study, we identified a novel 16-carbon cyclopentenoic acid in leaf extracts from Arabidopsis and potato. The new compound, a member of the jasmonate family of signals, was named dinor-oxo-phytodienoic acid. Dinor-oxo-phytodienoic acid was not detected in the Arabidopsis mutant fad5, which is incapable of synthesizing 7Z,10Z, 13Z-hexadecatrienoic acid (16:3), suggesting that the metabolite is derived directly from plastid 16:3 rather than by beta-oxidation of the 18-carbon 12-oxo-phytodienoic acid. Simultaneous quantitation of jasmonate family members in healthy leaves of Arabidopsis and potato suggest that different plant species have different relative levels of jasmonic acid, oxo-phytodienoic acid, and dinor-oxo-phytodienoic acid. We term these profiles "oxylipin signatures." Dinor-oxo-phytodienoic acid levels increased dramatically in Arabidopsis and potato leaves on wounding, suggesting roles in wound signaling. Treatment of Arabidopsis with micromolar levels of dinor-oxo-phytodienoic acid increased the ability of leaf extracts to transform linoleic acid into the alpha-ketol 13-hydroxy-12-oxo-9(Z) octadecenoic acid indicating that the compound can regulate part of its own biosynthetic pathway. Tightly regulated changes in the relative levels of biologically active jasmonates may permit sensitive control over metabolic, developmental, and defensive processes in plants.     

Experimental study of the possible implications of some apoptosis mechanisms in the pathogenesis of HIV infection. 1. In vitro apoptotic death of peripheral blood lymphocytes

The human immunodeficiency virus (HIV) infection produces a gradual depletion of T-helper CD4+ lymphocytes as, surprisingly, a consequence of apoptosis of the uninfected lymphocytes. We suggested that this is the result of the action exerted by HIV inductors of apoptosis (for example, gp 120) in the absence of viral apoptosis suppressor, which confers protection to the infected cell. We intended to demonstrate this hypothesis within the framework of a complex study regarding the apoptosis mechanisms in HIV infection. We started this study by setting up an apoptosis model on HIV-negative peripheral blood lymphocytes (PBLs)* cultivated in vitro in the presence of dexamethasone (Dex). In this work we characterize this model morphologically and biochemically. Three unreported morphological changes observed by us--namely: I) fringing of nucleus with advancement of fringes up to the plasma membrane; II) segmentation and peripheral migration of condensed chromatin through a rotation movement; III) "flowering of the cell" consisting in the radial separation of the lymphocyte into centrally united "petals" with the tendency to form apically multiple apoptotic bodies--completed the classical morphology of the apoptosis phenomenon. The apoptotic death was confirmed by the oligonucleosomal (multiples of 200 bp) and mononucleosomal fragmentation of DNA isolated from lymphocytes.     

Evaluation of red light camera enforcement in Oxnard, California

Red light cameras are increasingly being used to supplement police efforts to enforce against noncompliance with traffic signals--a substantial contributing factor in urban motor vehicle crashes. Camera enforcement is intended to modify driver behavior through both general deterrence and punishment of individual violators. A before/after quasi-experimental design with controls was employed to evaluate the influence of a red light camera enforcement program on red light violation rates in the city of Oxnard, CA. A total of 14 intersections (nine camera sites, three non-camera sites, and two control sites) were studied. Overall, the red light violation rate was reduced approximately 42% several months after the enforcement program began. Increases in driver compliance with red lights were not limited to the camera-equipped intersections but spilled over to nonequipped intersections as well. Results of public opinion surveys conducted approximately 6 weeks before, 6 weeks after, and 6 months after the camera enforcement program began indicated that nearly 80% of Oxnard residents support using red light cameras as a supplement to police efforts to enforce traffic signal laws.     

Isotopic characterisation of the historical lead deposition record at Glensaugh, an organic-rich, upland catchment in rural N.E. Scotland

As part of a wider investigation of the biogeochemistry and fate of Pb deposited from the atmosphere at Glensaugh, a rural upland catchment in N.E. Scotland, the concentration and isotopic composition of Pb were determined in four thinly sectioned monolith cores (25 cm) of peat collected at altitudes of 426--434 m from different faces of Thorter Hill and in a series of 21 10-cm unsectioned cores of peat and organic-rich soil along a transect from near the top (434 m) to the bottom (224 m) of the catchment. Depth profiles of Pb concentration and (206)Pb/(207)Pb ratio were similar for the longer cores. Subsurface Pb maxima (238--489 mg kg(-1)) typically occurred below (206)Pb/(207)Pb minima (1.123-1.134). One core was (210)Pb-dated and had a fairly constant (206)Pb/(207)Pb value of 1.170 from mid-19th century to ca. 1930, followed by a decline (attributable to the increasing influence of Australian Pb of much lower (206)Pb/(207)Pb ratio) to 1.134 by the early 1990s, and then a rapid increase to 1.160 by 2002, after the phased withdrawal of leaded petrol. The fluxes of Pb increased from 15 mg m(-2) year(-1) in the late 19th century to a peak of 60 mg m(-2) year(-1) ca. 1960, before declining steadily to 3.6 mg m(-2) year(-1) by the beginning of the 21st century. Some 40% of the anthropogenic Pb in the core had been deposited prior to 1900. The mean anthropogenic Pb inventory of the four longer cores was 7.4+/-1.5 g m(-2), of which approximately 70% occurred in the top 10 cm, in good agreement with the inventories of the shorter cores collected above 400 m. These inventories are higher than those of the industrial central belt of Scotland, probably because of enhanced deposition at altitude. This is consistent with the derived average (210)Pb flux of 198+/-11 Bq m(-2) year(-1), which is twice that of typical UK (210)Pb deposition and the rainfall for the site. The past deposition of Pb at Glensaugh, including that from sources (e.g., smelting, coal combustion) other than leaded petrol, has clearly been considerable. Even since the introduction of leaded petrol ca. 1930, car-exhaust emissions may have accounted for no more than 35% of the Pb deposited.