Dietary and aqueous exposure of finfish to organochlorine compounds: A case study

The level of organochlorine compounds was determined in whole capelin, Mallotus villosus, and compared to concentrations determined in tissues of yellowtail flounder, Pseudopleuronectes ferruginea, that fed on capelin for 2 years while maintained in tanks. Capelin represent part of the diet of offshore yellowtail flounder, however, they come to the beaches to spawn and were collected inshore for the feeding experiment. Therefore, inshore-offshore capelin concentrations were compared to investigate differences, while variables such as fish weight and lipid content were examined to give a better view of the range of contaminants concentrations in capelin. During two years, weekly exposure of flounder was to 148 L of water, as opposed to a dietary intake of 1 g of capelin. Although the level of contaminants was only measured in capelin, it can be estimated for the water, using results obtained on the level of contaminants in sediments obtained in a different study. According to our calculations, levels of contaminants were three to 20 times higher from the aqueous compared to the dietary uptake of inshore flounder, increasing with lower hydrophobicity. Exposure was from less than 10 to up to 100 times lower in expected and/or published results for offshore food and water, respectively. This comparison suggests a major influence of inshore waters on the bioaccumulation of contaminants in some inshore marine species, although the effect of altering the diet of captive finfish can not be disregarded.

A missense mutation in the human connexin50 gene (GJA8) underlies autosomal dominant "zonular pulverulent" cataract, on chromosome 1q

CZP1, a locus for autosomal dominant "zonular pulverulent" cataract, previously had been linked with the Duffy blood-group-antigen locus on chromosome 1q. Here we report genetic refinement of the CZP1 locus and show that the underlying mutation is present in GJA8, the gene for connexin50. To map the CZP1 locus we performed linkage analysis using microsatellite markers on two distantly related branches of the original Ev. pedigree, which now spans eight generations. Significantly positive two-point LOD score (Z) values were obtained for markers D1S2669 (maximum Z [Zmax] = 4.52; maximum recombination frequency [thetamax] = 0) and D1S514 (Zmax = 4.48; thetamax = 0). Multipoint analysis gave Zmax = 5.22 (thetamax = 0) at marker D1S2669. Haplotyping indicated that CZP1 probably lies in the genetic interval D1S2746-(20.6 cM)-D1S2771. Sequence analysis of the entire protein-coding region of the GJA8 gene from the pedigree detected a C-->T transition in codon 88, which introduced a novel MnlI restriction-enzyme site that also cosegregated with the cataract. This missense mutation is predicted to result in the nonconservative substitution of serine for a phylogenetically conserved proline (P88S). These studies provide the first direct evidence that GJA8 plays a vital role in the maintenance of human lens transparency and identify the genetic defect believed to underlie the first inherited disease to be linked to a human autosome.

The non-structural polyprotein 3ABC of foot-and-mouth disease virus as a diagnostic antigen in ELISA to differentiate infected from vaccinated cattle

A diagnostic assay to differentiate antibodies induced by foot-and-mouth disease virus (FMDV) infection from those induced by vaccination was developed. The test is an indirect-trapping ELISA which uses a monoclonal antibody to trap the non-structural 3ABC-FMDV polypeptide expressed in E. coli. Experimental and field sera from naive, vaccinated and infected cattle were examined. Using the established threshold of 0.20 optical density units, the sensitivity of the assay was 100%, as all the experimental post-infection sera (n degree = 137) gave values greater than this threshold, irrespective of the FMDV serotype used for the infection. In contrast, more than 99% of sera from vaccinated animals were negative (225 out of 228 primo-vaccinates and 159 out of 159 multi-vaccinates). A high degree of specificity was also confirmed by the finding that 99.5% (442 out of 444) of sera from naive animals gave negative results. Serum conversion against 3ABC was first detected 8 days post-infection and demonstrable levels of 3ABC specific antibodies were detectable at least 1 year post-infection. The described 3ABC-ELISA is safe, cheap and also easy to perform in large scale serological surveys. The high specificity and sensitivity makes this test an ideal tool for FMD eradication campaigns and control programs.

Methylmercury decreases IL-1beta immunoreactivity in the nervous system of the developing frog Xenopus laevis

In aquatic ecosystems, mercury can become methylated and act as a potent environmental toxin, producing developmental and neurotoxic effects in a variety of species, including frogs. Molecular indicators provide a means of assessing exposure to methylmercury and for understanding how it and other environmental toxins alter cellular function. Molecules such as growth or survival factors, and cytokines are good candidates for molecular indicators of exposure and/or damage because they are intimately related to cell and molecular processes that underlie normal growth and function. The cytokine, IL-1beta, was measured in whole frog embryos using Western blot methods and in specific structures using immunocytochemistry after exposure to 0, 10, 25, 50 and 100 parts per billion (ppb) methylmercury chloride (mmc). We observed no significant changes in total IL-1beta in whole embryo extracts. However, statistically significant decreases in IL-1beta were observed in the Vth cranial ganglion and myotomal blocks of Xenopus laevis embryos exposed to concentrations greater than or equal to 50 ppb mmc. In addition, increased mortality and alterations in gross morphology and behavior were altered by these same concentrations of mmc. Thus, frog embryos are highly susceptible to low levels of mmc contamination, and IL-1beta is an indicator of mmc exposure in the nervous system.

A novel and simple model of the uptake of organic chemicals by vegetation from air and soil

A novel and simple three-compartment fugacity model has been developed to predict the kinetics and equilibria of the uptake of organic chemicals in herbaceous agricultural plants at various times, including the time of harvest using only readily available input data. The chemical concentration in each of the three plant compartments leaf, stem which includes fruits and seeds, and root) is expressed as a function of both time and chemical concentrations in soil and air. The model was developed using the fugacity concept; however, the final expressions are presented in terms of concentrations in soil and air, equilibrium partition coefficients and a set of transport and transformation half-lives. An illustrative application of the model is presented which describes the uptake of bromacil by a soybean plant under hydroponic conditions. The model, which is believed to give acceptably accurate prediction of the distribution of chemicals among plant tissues, air and soil, may be used for the assessment of exposure to, and risk from contaminants consumed either directly from vegetation or indirectly in natural and agricultural food chains.

A new locus for dominant "zonular pulverulent" cataract, on chromosome 13

Inherited cataract is a clinically and genetically heterogeneous disease that most often presents as a congenital autosomal dominant trait. Here we report the linkage of a new locus for dominant "zonular pulverulent" cataract (CZP) to chromosome 13. To map the CZP locus we performed molecular-genetic linkage analysis using microsatellite markers in a five-generation English pedigree. After exclusion of eight known loci and several candidate genes for autosomal dominant cataract, we obtained significantly positive LOD scores (Z) for markers D13S175 (maximum Z [Zmax] = 4.06; maximum recombination frequency [theta max] = 0) and D13S1236 (Zmax = 5.75, theta max = 0). Multipoint analysis gave Zmax = 6.62 (theta max = 0) at marker D13S175. Haplotype data indicated that CZP probably lies in the centromeric region of chromosome 13, provocatively close to the gene for lens connexin46.

Peer reviewed: tracking the distribution of persistent organic pollutants

Control strategies for these contaminants will require a better understanding of how they move around the globe.

pKI values of prazosin and idazoxan for receptors stimulated by neuronally released transmitter in the epididymal portion of rat isolated vas deferens

1. A new method has been used to measure pKI values of prazosin and idazoxan against neuronally-released transmitter in the epididymal portion of the rat isolated vas deferens. The most reproducible results were obtained with a prolonged antagonist equilibration time (1 h). 2. Under these conditions the pKI of prazosin was practically unaffected by addition of alpha, beta-methylene-adenosine-5'-triphosphate (10 microM) to desensitize purinoceptors. Addition of desmethylimipramine (DMI) (0.3 microM) produced a small, but statistically non-significant, reduction. 3. The same method has been used to measure the pKI of prazosin against exogenous noradrenaline. In the latter case addition of DMI (0.3 microM) and corticosterone (30 microM) together produced a statistically significant reduction in the apparent pKI of prazosin. 4. The new method for estimating pKI values shows that DMI itself acts either pseudo-irreversibly or non-competitively and may be reducing the apparent pKI of prazosin. 5. The pKI values obtained for prazosin and idazoxan against neuronally-released transmitter are in good agreement with those obtained by other workers for the actions of these drugs on alpha-adrenoceptors.

A new method for estimating dissociation constants of competitive and non-competitive antagonists with no prior knowledge of agonist concentrations

1. A method is presented which enables the dissociation constant (KI) of a competitive, pseudo-irreversible or non-competitive antagonist-receptor complex to be estimated without knowledge of agonist concentrations. 2. The technique has been tested using sets of concentration-response data which simulated these various types of antagonism. 3. The points for each set of simulated data could be plotted both as agonist concentration-response curves at fixed antagonist concentrations and vice versa, producing paired data sets. 4. pKI-values were estimated from such paired data sets using appropriate graphical and computer curve-fitting methods. 5. For competitive antagonism, for each paired data set the computer curve-fitting techniques gave the same value for pKI, assuming drug-receptor interaction to be 1:1 and agonist concentrations to be known. 6. When agonist concentrations were assumed unknown, pKIS could not be estimated by the conventional method (using agonist dose-ratios) but could still be obtained (for competitive, pseudo-irreversible and non-competitive antagonism) by the new method. 7. This new method should be especially useful for measuring dissociation constants of antagonists against neuronally- or ionophoretically-released agonists. It may also be useful when agonist is applied exogenously, especially if suitable drugs are not available to block agonist uptake and/or metabolism.

Cyclin A-mediated inhibition of intra-Golgi transport requires p34cdc2

An in vitro assay was used to study the role of p34cdc2 in cyclin A-mediated vesicular transport inhibition. It was shown that the S-phase kinase p33cdk2 reduced the effect of cyclin A on transport assays performed with sHeLa cytosol, even though histone kinase was strongly activated. Also, transport with FT210 cytosol (which is temperature-sensitive for p34cdc2) was inhibited by cyclin A only at the permissive temperature. However, the phosphatase inhibitor microcystin inhibited transport without any requirement for p34cdc2 activity. These results show that transport is inhibited by cyclin A via p34cdc2, and also by another kinase, possibly downstream of p34cdc2.

Residue-based interpretation of toxicity and bioconcentration QSARs from aquatic bioassays: polar narcotic organics

Bioconcentration and toxicity estimation for a group of substituted phenols often categorized as "polar narcotics" can be confounded by pH-dependent ionization. Two methods of correction for ionization were applied to toxicity data obtained by U.S. EPA-Duluth for fathead minnows exposed to 30 different phenols in 37 bioassays. Toxicity QSARs with corrected data were substantially different from those obtained with raw toxicity data. When ionization-corrected toxicity data were used in the critical body residue (CBR) estimation process previously successful with neutral narcotic organics, several categories of CBR, apparently related to different modes of toxic action, resulted. Published data on lethal CBR for substituted phenols were in general agreement, although such information is limited. Elimination half-life rate constants, estimated from nonlinear curve fitting to time-toxicity information, were relatively constant for the Duluth bioassay data, averaging 0.3 days. Half-life information for small aquatic organisms, both from toxicity- and bioconcentration-based tests in the literature, was in a similar range. Much of the relatively high variability encountered experimental data for substituted phenols may in large part be due to differences in metabolic degradation between chemicals and species.

Inhibition of intra-Golgi transport in vitro by mitotic kinase

It has previously been shown that exocytic and endocytic membrane traffic are inhibited in mitotic mammalian cells. Here we have used a cell-free intra-Golgi transport assay supplemented with heterologous cytosols to mimic this effect in vitro. Cytosols with high histone kinase activity, made either from mitotic cells or by cyclin A treatment of interphase cells, inhibited intra-Golgi transport by up to 75%. Inhibition of transport was reversed by the kinase inhibitor staurosporine or by reduction in ATP levels leading to inactivation of histone kinase. The data indicate that cell cycle control of intra-Golgi transport is due to a reversible modification of cytosol, and this assay system may be used to study the molecular mechanism of mitotic transport inhibition in mammalian cells.

The membrane spanning domain of beta-1,4-galactosyltransferase specifies trans Golgi localization

Chimeric cDNAs were constructed so as to generate hybrid proteins in which different parts of the N-terminal domain of the human invariant chain were replaced by equivalent sequences from the trans Golgi resident enzyme, beta-1,4-galactosyltransferase. The cytoplasmic and membrane spanning domains of galactosyltransferase were found to be sufficient to retain all of the hybrid invariant chain in trans Golgi cisternae as judged by indirect immunofluorescence, treatment with brefeldin A and immuno-electron microscopy. As few as ten amino acids corresponding to the lumenal half of the membrane spanning domain of the Golgi enzyme sufficed to localize most of the hybrid invariant chain to the trans cisternae. A cytoplasmic domain was necessary for complete retention as assessed by flow cytofluorometry but could be provided either by galactosyltransferase or by invariant chain. This suggests that the cytoplasmic domain plays a role accessory to the membrane spanning domain, the latter mediating compartmental specificity.

Analysis of the binding of fluorescent ligands to soluble proteins. Use of simultaneous non-linear least squares regression to obtain estimates of binding parameters

The binding of three fluorescent ligands (warfarin, dansylsarcosine and 1-anilino-8-naphthalene sulphonate) to human albumin was analysed using simultaneous non-linear least squares regression analysis. Both mock and actual fluorescence data were examined and the results indicated that reliable estimates of the binding parameters as well as the molar fluorescence of bound ligand could be obtained. The advantage of this method of analysis is that it makes full use of all the experimental data and it eliminates the need for the graphical procedures usually employed to estimate the molar fluorescence of bound ligand and its binding constants. This type of analysis can be extended to other systems where some physical property of the bound ligand varies with increasing protein concentration.

Separation of the Baragwanath craniopagus twins

A case of craniopagus twins is presented. Large contralateral flaps were used to cover the bony defect and exposed brain. Details of the planning and problems are discussed.