Comparative effects of trichothecene mycotoxins on bovine platelet function: Acetyl T-2 toxin,a more potent inhibitor than T-2 toxin

The effects of the trichothecene mycotoxins (acetyl T-2 toxin, T-2 toxin, HT-2 toxin, palmityl T-2 toxin, diacetoxyscirpenol (DAS), deoxynivalenol (DON), and T-2 tetraol) on bovine platelet function were examined in homologous plasma stimulated with platelet activating factor (PAF). The mycotoxins inhibited platelet function with the following order of potency: acetyl T-2 toxin > palmityl T-2 toxin = DAS > HT-2 toxin = T-2 toxin. While T-2 tetraol was completely ineffective as an inhibitor, DON exhibited minimal inhibitory activity at concentrations above 10×10^?4M. The stability of the platelet aggregates formed was significantly reduced in all mycotoxin treated platelets compared to that of the untreated PAF controls. It is suggested that the increased sensitivity of PAF stimulated bovine platelets to the more lipophilic mycotoxins may be related to their more efficient partitioning into the platelet membrane compared to the more hydrophilic compounds.     

Active and passive cation transport and L antigen hertogeneity in low potassium sheep red cells

Several lines of experimental evidence are presented suggesting that the L antigens in low potassium (LK) sheep red cells are associated with separate Na(+)K(+) pump flux is distinct from the action of anti-L(l) on K(+) leak flux, implying that K(+) leak transport sites may not be converted into active pumps by the L antiserum. Treatment of LK red cells with trypsin completely abolished both the stimulation of K(+) pump flux and the enhancement of the rate of ouabain binding brought about by anti- L. That this effect is due to a total destruction of the L(p) determinant associated with the LK pump was evident from the complete failure of anti-L(p) to bind to trypsinized LK red cells. The L(p) antigen can be effectively protected against the trypsin attack by prior incubation with anti-L, indicating that the sites for antibody binding and trypsin action may be closely adjacent at the structural level. Trypsin treatment, however, did not interfere with anti-L(l) reducing ouabain insensitive K(+) leak influx, nor did it prevent binding of anti-L(ly), the hemolytically active L antibody which is probably identical with anti-L(l). The functional independence of the L(p) and L(l) sites was documented by the observation that anti-L(l) still reduced K(+) leak influx in LK cells with experimentally induced high potassium concentrations, at which K(+) pump flux is fully suppressed, whether or not anti-L(p) was binding to the L(p) antigen associated with the LK pump.     

An evolutionary change in the muscle lineage of an anural ascidian embryo is restored by interspecific hybridization with a urodele ascidian

Anural ascidians do not develop into a conventional tailed larva with differentiated muscle cells, however, embryos of some anural ascidian species retain the ability to express acetylcholinesterase (AChE) in a vestigial muscle cell lineage. This study examines the number of AChE-positive cells that develop in the anural ascidian Molgula occulta relative to that in the closely related urodele (tailed) species, Molgula oculata. Histochemical assays showed that M. oculata embryos develop 36 to 38 AChE-positive cells, consistent with the number of tail muscle cells expressed in other urodele ascidians. In contrast, M. occulta embryos develop a mean of only 20 AChE-positive cells in their vestigial muscle lineage. Cleavage-arrested embryos of the anural species express AChE only in B-line blastomeres, showing that the vestigial muscle lineage cells are derived from the primary muscle lineage. Less than the expected number of AChE-positive B-line cells develop in cleavage-arrested anural embryos, however, implying that the allocation of primary muscle lineage cells is decreased. Eggs of the anural species can be fertilized with sperm of the urodele species resulting in the development of some larvae that contain a short tail and/or a brain melanocyte, specific features of urodele larvae. The typical urodele number of AChE-positive cells is restored in some of these hybrid embryos. Both primary and secondary muscle lineages are restored because cleavage-arrested hybrid embryos develop more AChE-positive cells in the B-line blastomeres and supernumerary AChE-positive cells in the A-line blastomeres. Hybrid embryos that develop the urodele complement of AChE-positive cells also form a tail and/or a brain melanocyte showing that restoration of muscle lineage cells is coupled to the development of other urodele features. AChE expression occurred in anural embryos with disorganized or dissociated blastomeres, indicating that AChE expression is determined autonomously. It is concluded that an evolutionary change in the allocation of larval muscle lineage cells occurs during development of the anural ascidian M. occulta which can be restored by interspecific hybridization with the urodele ascidian M. oculata.     

Multiple effects of temperature,photoperiod and food quality on the performance of a pine sawfly

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A revisited phylogeography of Nautilus pompilius

The cephalopod genus Nautilus is considered a “living fossil” with a contested number of extant and extinct species, and a benthic lifestyle that limits movement of animals between isolated seamounts and landmasses in the Indo‐Pacific. Nautiluses are fished for their shells, most heavily in the Philippines, and these fisheries have little monitoring or regulation. Here, we evaluate the hypothesis that multiple species of Nautilus (e.g., N. belauensis, N. repertus and N. stenomphalus) are in fact one species with a diverse phenotypic and geologic range. Using mitochondrial markers, we show that nautiluses from the Philippines, eastern Australia (Great Barrier Reef), Vanuatu, American Samoa, and Fiji fall into distinct geographical clades. For phylogenetic analysis of species complexes across the range of nautilus, we included sequences of Nautilus pompilius and other Nautilus species from GenBank from localities sampled in this study and others. We found that specimens from Western Australia cluster with samples from the Philippines, suggesting that interbreeding may be occurring between those locations, or that there is limited genetic drift due to large effective population sizes. Intriguingly, our data also show that nautilus identified in other studies as N. belauensis, N. stenomphalus, or N. repertus are likely N. pompilius displaying a diversity of morphological characters, suggesting that there is significant phenotypic plasticity within N. pompilius.     

Conservation of structure and function among tyrosine recombinases: homology-based modeling of the lambda integrase core-binding domain

Tyrosine recombinases participate in diverse biological processes by catalyzing recombination between specific DNA sites. Although a conserved protein fold has been described for the catalytic (CAT) domains of five recombinases, structural relationships between their core-binding (CB) domains remain unclear. Despite differences in the specificity and affinity of core-type DNA recognition, a conserved binding mechanism is suggested by the shared two-domain motif in crystal structure models of the recombinases Cre, XerD and Flp. We have found additional evidence for conservation of the CB domain fold. Comparison of XerD and Cre crystal structures showed that their CB domains are closely related; the three central α-helices of these domains are superposable to within 1.44 Å. A structure-based multiple sequence alignment containing 25 diverse CB domain sequences provided evidence for widespread conservation of both structural and functional elements in this fold. Based upon the Cre and XerD crystal structures, we employed homology modeling to construct a three-dimensional structure for the λ integrase CB domain. The model provides a conceptual framework within which many previously identified, functionally important amino acid residues were investigated. In addition, the model predicts new residues that may participate in core-type DNA binding or dimerization, thereby providing hypotheses for future genetic and biochemical experiments.     

Industrial microbiology of solar salt production

Solar salterns can be modeled as giant outdoor chemostats, much like a series of dams on a slow-moving river. Microorganisms and their products play an essential, but sometimes uncharacterized, role in salt production in these ponds, from seawater salinity up through NaCl saturation. They may physically affect the evaporation process and their by-products may chemically modify or bind with dissolved ions. Many solar salt facilities engage microbiologists to establish monitoring programs for analyses of nutrients, standing crop and associated biological variables in the ponds. Other solar salt companies engage microbiologists only when there are “crises” in the ponds that interfere with salt production. Journal of Industrial Microbiology & Biotechnology (2002) 28, 42–47 DOI: 10.1038/sj/jim/7000173 Received 20 May 2001/ Accepted in revised form 13 June 2001