Evaluation of the radioimmunoassay (RIA) for detection of Ciguatoxin (CTX) in fish tissues

The results of the radioimmunoassay (RIA) procedure for the direct determination of ciguatoxin (CTX) in fish tissues are presented. The RIA procedure detected CTX in 93% of fish tissues obtained from clinically documented ciguatera cases. The immunoglobulin nature of the reactive serum factor in sheep immunized with CTX was ascertained by DEAE-cellulose chromatography and by the ability to distinguish toxic from nontoxic fish tissues. Furthermore, a longitudinal study with commercial Seriola dumerili proved the RIA procedure to be effective in protecting the consumer from ciguatera poisoning by eliminating the potentially hazardous fishes from the markets. It is suggested that the RIA procedure has potential use in surveying areas for fishery development and is of value in keeping potentially toxic large fish off the market.     

Organization of DNA sequences near the centromere of the Drosophila melanogaster Y chromosome

The structural analysis of a yeast artificial chromosome clone from Drosophila melanogaster enriched in dodecasatellite sequences has led us to find a new retrotransposon that we have called Circe. Moreover, this retrotransposon has allowed the isolation of a contig encompassing ∼200 kb near the centromere of the Y chromosome, providing an entry point into a region from which very little sequence information has been obtained to date. The molecular characterization of the contig has shown the presence of HeT-A telomeric retrotransposons close to the centromere of the Y chromosome, suggesting a telocentric origin for this submetacentric chromosome. Received: 19 November 1996 / Accepted: 30 May 1997     

A study of the conformational equilibrium of DL-oligophenylalanines in nonpolar solvents in the presence and absence of lipids by high-performance liquid chromatography

The usefulness of high-performance size-exclusion liquid chromatography (HPSEC) for the separation of dimeric and monomeric species of DL-alternating oligophenylalanines is demonstrated for the first time. The experimental data obtained as a function of time fit a simple dimer-monomer equilibrium in a nonpolar solvent such as tetrahydrofuran. A higher extent of monomerization and a decrease in the time required for reaching equilibrium were detected in the presence of either water or phosphatidylcholine. The analysis of the relative proportions of the two separated species under equilibrium conditions has allowed the influence of the oligopeptide chain length on the stability of dimeric species to be determined. The advantages of this methodology, in combination with spectroscopic techniques, in studies on autoassociating peptides are considered.     

Immunohistochemical modifications of "B cells" in experimentally-induced pancreatic cancer--correlation with serum insulin values

In pancreatic ductal adenocarcinoma induced in the Syrian hamster by N-nitrosobis (2-oxopropyl) amine (Bop) B cells persisted with focal dispersion in the tumor zone. The localization of these varied depending on whether the animals had initial or long standing tumors. In the animals with initial tumors, immunohistochemical techniques indicated the B cells formed part of the tumoral glands and/or were intimately related to the cells of the walls of the tumor glands or present in the stroma. Insulin values were high in these animals. In the longer-developed tumors, insulin levels tended to be lower and although B cells were seen forming part of the tumor glands, those in the tumoral stroma were predominant.     

Intramolecular electron transfer in diastereomeric naphthalene-amine dyads: a fluorescence and laser flash photolysis study.

Two dyads containing a naphthalene-like chromophore linked to a pyrrolidine-derived moiety, namely (S,S)- and (R,S)-NPX-PYR, have been synthesised by esterification of (S)- or (R)-naproxen (NPX) with (S)-N-methyl-2-pyrrolidinemethanol (PYR) and submitted to photophysical studies (steady-state and time-resolved fluorescence, as well as laser flash photolysis). The emission spectra of the dyads in acetonitrile were characterised by a typical band centred at 350 nm, identical to that of the reference compound (S)-NPX. However the intensities were clearly different, revealing a significant intramolecular quenching in the dyads, as well as a remarkable stereodifferentiation (factor of 1.6). Accordingly, the fluorescence lifetimes of the two dyads were different from each other and markedly shorter than that of (S)-NPX. The quenching mechanism is intramolecular electron transfer, that is thermodynamically favoured. Exciplex formation, that is nearly thermoneutral, does not compete efficiently. The electron transfer rate constants for (S,S)- and (R,S)-(NPX-PYR) were 1.8 x 10(8) and 2.8 x 10(8) s(-1), respectively. By contrast, no significant intramolecular quenching was observed for the excited triplet states (lambda(max)= 440 nm), generated by laser flash photolysis; this is in agreement with the fact that intramolecular electron transfer is thermodynamically disfavoured, due to the lower energy of excited triplets.     

Effects of Salinity on Chlorophyll Fluorescence and Photosynthesis of Barley (Hordeum Vulgare L.) Grown Under a Triple-Line-Source Sprinkler System in the Field

In flag leaves of four cultivars of barley (Hordeum vulgare L.) grown in the field under a triple-line-source sprinkler system, that produces a linear soil salinity gradient, a decrease in net carbon dioxide assimilation rate (P_N) and stomatal conductance for water vapour (gs) was found. These changes were related to salinity tolerance at moderate salinity. With increasing salinity, P_N was saturated at low irradiances and stomatal frequencies increased. A decrease in photosystem 2 (PS2) efficiency was not found in the field after dark adaptation even at high salinity. Salinity induced only small decreases in the actual PS2 efficiency at midday steady-state photosynthesis, indicating that the photosynthetic electron transport was little affected by salinity. Therefore, using PS2 efficiency estimates in attached leaves is probably not a useful tool to screen barley genotypes grown under saline conditions in the field for salinity tolerance. In contrast, excised flag leaves from high salinity plots, once in the laboratory, exhibited a decrease in the variable to maximum chlorophyll fluorescence ratio as compared to excised leaves from control plants. On the other hand, the PN rate might allow for a good discrimination between tolerant and non-tolerant cultivars. This revised version was published online in June 2006 with corrections to the Cover Date.     

Epoxidation of 6,7- and 10,11-oxidosqualenes by the squalene epoxidase present in rat liver microsomes

Incubation of 6,7-oxidosqualene (2) or 10,11-oxidosqualene (3) with rat liver microsomes led to the formation of mixtures of the corresponding dioxidosqualenes (4 and 5, or 6 and 7, respectively), resulting from the epoxidation of 2 and 3 at their terminal double bonds. The epoxidation requires the presence of both NADPH and FAD. In addition, the HPLC analysis of the Mosher esters resulting from the controlled hydrolysis of dioxide 5 to give the corresponding epoxydiols 9 followed by derivatization with (R)-MTPA, showed that the epoxidation had been stereoselective. These facts support the hypothesis that these dioxidosqualenes had been generated by the squalene epoxidase present in the incubation medium.     

Conformational species of gramicidin A in non-polar solvent. A kinetic and thermodynamic treatment in the absence and presence of phosphatidylcholine as studied by high-performance liquid chromatography

A kinetic and thermodynamic study has been carried out to characterize quantitatively the conformational equilibrium of gramicidin A (GA) in tetrahydrofuran at different peptide concentrations in the absence and presence of egg yolk phosphatidylcholine by using size-exclusion high-performance liquid chromatographic analysis. In the absence of lipid, the experimental data fit a simple dimer-monomer equilibrium, the rate and equilibrium constants for the dissociation process being (1.6 +/- 0.7) X 10(-7) s-1 and (8.5 +/- 0.3) X 10(-6) M, respectively. A higher extent of monomerization and a decrease in the time required for reaching equilibrium are detected in the presence of phospholipid, the kinetic and thermodynamic effects depending on both lipid and GA concentrations. In order to account for these observations a cyclic equilibrium mechanism is proposed which is analysed in terms of four conformational species, namely, free monomer, free dimer, lipid-bound monomer and lipid-bound dimer. The results obtained are discussed in relation to recent literature data on lipid-protein interactions.     

Large‐scale parentage analysis reveals reproductive patterns and heritability of spawn timing in a hatchery population of steelhead (Oncorhynchus mykiss)

Understanding life history traits is an important first step in formulating effective conservation and management strategies. The use of artificial propagation and supplementation as such a strategy can have numerous effects on the supplemented natural populations and minimizing life history divergence is crucial in minimizing these effects. Here, we use single nucleotide polymorphism (SNP) genotypes for large‐scale parentage analysis and pedigree reconstruction in a hatchery population of steelhead, the anadromous form of rainbow trout. Nearly complete sampling of the broodstock for several consecutive years in two hatchery programmes allowed inference about multiple aspects of life history. Reconstruction of cohort age distribution revealed a strong component of fish that spawn at 2 years of age, in contrast to programme goals and distinct from naturally spawning steelhead in the region, which raises a significant conservation concern. The first estimates of variance in family size for steelhead in this region can be used to calculate effective population size and probabilities of inbreeding, and estimation of iteroparity rate indicates that it is reduced by hatchery production. Finally, correlations between family members in the day of spawning revealed for the first time a strongly heritable component to this important life history trait in steelhead and demonstrated the potential for selection to alter life history traits rapidly in response to changes in environmental conditions. Taken together, these results demonstrate the extraordinary promise of SNP‐based pedigree reconstruction for providing biological inference in high‐fecundity organisms that is not easily achievable with traditional physical tags.