Assessment of the risk posed by the antifouling booster biocides Irgarol 1051 and diuron to freshwater macrophytes.

Antifouling paints are used to reduce the attachment of living organisms to the submerged surfaces of ships, boats and aquatic structures, usually by the release of a biocide. Two 'booster' biocides in common use are the triazine herbicide Irgarol 1051 (N-2-methylthio-4-tert-butylamino-6-cyclopropylamino-s-triazine), and diuron (1-(3,4-dichlorophenyl)-3,3-dimethylurea), which are designed to inhibit algal photosynthesis. Previous research has been directed at the effects of these compounds in marine and estuarine environments. In 2001 we sampled the main rivers and shallow freshwater lakes (Broads) of East Anglia UK for Irgarol 1051, its metabolite GS26575 (2-methylamino-4-tert-butylamino-6-amino-s-triazine) and diuron in order to establish the baseline environmental concentrations of these compounds in freshwater systems of eastern UK and to investigate their possible effects on aquatic plants. Irgarol 1051, GS26575 and diuron were found in water samples collected from 21 locations. The highest concentrations were found in the Norfolk and Suffolk Broads in May. The rivers Great Ouse, Wissey, Bure and Yare also contained all three compounds, as did the Great Ouse Cut-off Channel. The toxicity of these biocides to three macrophyte species (Apium nodiflorum, Chara vulgaris, and Myriophyllum spicatum) was investigated. Deleterious effects on relative growth rate, the maximum quantum efficiency (Fv/Fm) of photosystem II and, for Apium, root mass production were found. C. vulgaris was generally most sensitive; growth, especially of roots, was strongly affected in A. nodiflorum; growth rate of M. spicatum was sensitive to diuron. No observed effect concentrations (NOEC) were interpolated using standard toxicological analysis. These were compared with measured environmental concentrations (MEC) to determine the ranges of risk quotients (MEC/NOEC). Both Irgarol 1051 and diuron represented significant risks to A. nodiflorum and C. vulgaris in this area.

Structure of the histone-core octamer in KCl/phosphate crystals at 2.15 A resolution.

The structure of the native chicken histone octamer, crystallized in 2 M KCl, 1.35 M potassium phosphate pH 6.9, has been refined at 2.15 A resolution to a final R factor of 21.4% and an R(free) of 25.2%. Unique crystal-packing interactions between histone-core octamers are strong and one of them (area 4000 A(2)) involves two chloride ions and direct interactions between six acidic amino-acid residues on one octamer and the equivalent number of basic residues on the next. These interactions are on the structured part of the octamer (not involving tails). Five phosphate ions, 23 chloride ions and 437 water molecules have been identified in the structure. The phosphate and some chloride ions bind to basic amino-acid residues that interact with DNA in the nucleosome. The binding of most of the anions and the packing interactions are unique to these crystals. In other respects, and including the positions of four chloride ions, the octamer structure is very close to that of octamers in nucleosome-core particle crystals, particularly with respect to 'docking' sequences of the histone H2As and H4s. These sequences together with the H2B-H4 four-helix bundles stabilize the histone structure in the nucleosome and prevent the dissociation of the (H2A-H2B) dimers from the (H3-H4)(2) tetramer. Possible reasons why this happens at high salt in the absence of DNA are given.

Purification of histone core octamers and 2.15 A X-ray analysis of crystals in KCl/phosphate.

Intact histone octamers, produced by a new method quickly and in bulk, were crystallized in KCl/phosphate, and the X-ray data were analysed to 2.15 A, confirming a P65 space group. This environment preserves the high-resolution structure of the octamers and will be useful for studying them with other functionally important molecules. The octamers form into left-handed superhelices hexagonally spaced by 158.65 A, having a pitch of 102.57 A with six octamers per turn. A dipotassium tetraiodo mercurate derivative had good phasing power and should prove valuable in refining the structure after molecular-replacement analysis with lower resolution coordinates; the heavy atom was isomorphously placed at a unique site between the two H3-cysteine residues in the octamer.

New crystals of the histone core octamer diffract to higher resolution, 2.65 A.

A new crystal form of the histone octamer, crystallized in 1.6 M KCl, 1.6 M phosphate, diffracts to appreciably better than 2.6 A resolution. The crystals have space group P6(1) or P6(5) and lattice parameters a = b = 158.29, c = 103.27 A, alpha = beta = 90, gamma = 120 degrees, with one molecule per asymmetric unit. The new crystals promise to yield more detail of the histone basic domains and a higher resolution structure for the histone octamer.

Occupational conditions and workers' sense of community: variations by gender and race.

The literature is reviewed to define a sense of community in the workplace and to identify factors that may foster it. A model is developed and estimated with survey data from a culturally diverse sample of men and women performing lower-level jobs at a medium-sized manufacturing firm. Results of regression analyses are reported that correct for sample selection bias resulting from the lower response rates of minority workers. Findings suggest that well-designed jobs and supportive workplace relationships and policies are important in explaining workers' sense of community, defined as workers' perceptions of mutual commitment between employee and employer. Informal sources of support play a larger role in explaining men's sense of community, while formal sources of support are more important in explaining women's sense of community. Findings further suggest that African American workers, especially women, have a difficult time experiencing a sense of community at work.

Neutron and x-ray scatter studies of the histone octamer and amino and carboxyl domain trimmed octamers.

The structure of the nucleosome has been under intense investigation using neutron crystallography, x-ray crystallography, and neutron solution scattering. However the dimension of the histone octamer inside the nucleosome is still a subject of controversy. The radius of gyration (Rg) of the octamer obtained from solution neutron scattering of core particles at 63% 2H2O, 37% 1H2O is 33 A, and x-ray crystallography study of isolated histone octamer gives a Rg of 32.5 A, while the reported values using x-ray crystallography of core particles from two individual studies are 29.7 and 30.4 A, respectively. We report here studies of isolated histone octamer and trypsin-limited digested octamer using both neutron solution scattering and small angle x-ray scattering. The Rg of the octamer obtained is 33 A, whereas that of the trimmed octamer is 29.8 A, similar to the structure obtained from the crystals of the core particles. The N-terminal domains of the core histones in the octamer have been shown by high resolution nuclear magnetic resonance (Schroth, G.P., Yau, P., Imai, B.S., Gatewood, J.M., and Bradbury, E.M. (1990) FEBS Lett. 268, 117-120) to be mobile and flexible; it is likely that these regions are disordered and "not seen" by x-ray crystallography.

The simultaneous presentation of retinopathy of prematurity and central serous chorioretinopathy.

A case report of central serous chorioretinopathy (CSC) and retinopathy of prematurity (ROP) in the same patient is presented. CSC is a disease of the outer retinal layers, specifically the retinal pigment epithelium, which results in serous detachment of the neurosensory retina. ROP is a disease of the anterior retinal layers, affecting the retinal vasculature. Ocular manifestations may range from the peripheral neovascularization observed in the milder states to retinal detachment and secondary angle closure glaucoma that is often found in the later stages. Therefore it would appear that there is no direct relationship between the presence of ROP and the presence of CSC in a patient who presented with complaints of a unilateral relative central scotoma. To our knowledge this represents a heretofore unreported association.

Effect of target size on anomalous sensory responses in the Bagolini striated lens test.

Different results obtained by different methods of retinal correspondence testing are generally accepted to be a sign of the depth of the anomalous sensory adaptation. The Bagolini striated lens test is considered a standard "natural" test to which others are compared. In this study, the Bagolini striated lens test was performed on 25 strabismic subjects using three target sizes in order to determine if target size might be a factor in response variability. Kappa Measure of Agreement, used to analyze the results statistically, showed a moderately high to high level of agreement among the three targets. This indicates that practitioners can feel confident of consistent test results on the striated lens test using any of the three readily available target sizes selected. A brief literature review has been provided as a guide to the theories of strabismus and correspondence and to emphasize the purpose of this research.

Cardiac myosin light and heavy chain isotypes in tetralogy of Fallot.

Myosin isotype composition was examined in ventricular infundibular muscle from 40 patients with tetralogy of Fallot, aged from 7 months to 38 years. Results were compared with normal samples of ventricular infundibulum from subjects in the same age range, from 18-20 week old fetuses to 6 month old neonates, and from 43-81 year old adults. Myosin light chain isotypes were examined by one dimensional and two dimensional gel electrophoresis and quantified densitometrically. Heavy chain isotypes were examined by electrophoresis of whole heavy chains and peptide mapping after limited proteolytic digestion with chymotrypsin. At mid-gestation in normal tissues, only ventricular light chain 2 was present but light chain 1 consisted almost equally of atrial and ventricular isotypes. Amounts of atrial light chain 1 declined towards birth and disappeared during the first year after birth, gradually being replaced by ventricular light chain 1. Relative amounts of total light chains 1 and 2 remained equal. In tetralogy of Fallot atrial light chain 1 expression did not cease neonatally with mean values of 11.8% of total light chain 1 present between 7 months and 2 years, decreasing to 1.7% at 6.5-12 years and then increasing again to 3.4% in adults. A value of 34% atrial light chain 1 was present in one subject. As in normal subjects, equimolar amounts of total light chains 1 and 2 were retained. No evidence of new light chain isotypes was found in tetralogy of Fallot. Heavy chain expression was constant in normal infundibulum with only beta-heavy chain (V3 isozyme) present in the fetus, neonate, and adult.(ABSTRACT TRUNCATED AT 250 WORDS)

Myosin transitions in the bovine and human heart. A developmental and anatomical study of heavy and light chain subunits in the atrium and ventricle.

Transitions in cardiac myosin isotypes occur in response to a variety of stimuli. These are well documented in small, but less so in larger, mammals where data on quantitative isotype composition of normal atria and ventricles are scarce. In this study, heavy and light chain isotypes were examined in fetal, neonatal, and adult bovine and human hearts. Defined anatomical areas of chambers were studied, and detailed mapping of isotypes was conducted on bovine atria. Heavy chain isotype quantification was carried out electrophoretically either after peptide mapping or by a new technique for separating whole cardiac alpha- and beta-heavy chains capable of detecting 5% of either isotope. Atrial and ventricular light chains were resolved electrophoretically, and all isotypes were quantified densitometrically. Beta-Heavy chain was almost exclusively expressed (greater than 95%) in the ventricles at all ages except in the bovine neonate. Ventricular light chains predominated in the adult ventricle, but atrial light chain 1 was present at mid-gestation. This was replaced by ventricular light chain 1 in the neonate with no transitions in light chain 2 isotypes. Transitions were more marked in the atria. Only alpha-heavy chains were detected at mid-gestation, but beta-heavy chain increased toward birth. After a decline in the neonatal period, beta-heavy chain levels usually increased in the adult. Atrial light chains were the main isotypes in the atria, but ventricular light chain 2 was the major adult bovine atrial isotype. Transitions in isotypes were significant at birth as in smaller mammals. No close relationship existed between heavy and light chain transitions. Significant anatomical variation in bovine atrial isotype expression was present, and may reflect functional demand in each area.