Mutagenicity of tetramic mycotoxin cyclopiazonic acid.

Cyclopiazonic acid was shown to be mutagenic to Salmonella typhimurium TA98 and TA100 in the presence of metabolic activation. The activity of cyclopiazonic acid in the presence of aflatoxin B1 was studied in complete factorial experiments with strain TA98. Both mycotoxins produced significant mutagenic activity and in combination. The activity in combination appeared to be additive rather than synergistic. The specific activity of cyclopiazonic acid was estimated to be approximately 140 revertants per mu mol in strain TA98.     

Regulation of maize catalase by changing rates of synthesis and degradation.

Rates of catalase synthesis and degradation were measured in the scutellum of the germinating maize seedling by the technique of Price, Sterling, Tarantola, Hartley & Rechcigl [J. Biol. Chem. (1963) 237, 3468-3475] by using the porphyrinogenic drug 2-allyl-2-isopropylacetamide to inhibit catalase synthesis. Results indicate that developmental changes in catalase activity are determined by changes in the rate of enzyme degradation as well as by changes in the rates of its synthesis.     

Functional activity in vivo of effector T cell populations. I. Antitumor activity exhibited by allogeneic mixed leukocyte culture cells

The in vivo activity of murine cytolytic T lymphocyte-containing effector cell populations generated in vitro was studied in a tumor allograft model system by monitoring the elimination of 131I-IUdR-labeled tumor cells with whole-body counting techniques. Mice were irradiated sublethally and 16 hr later 131I-labeled tumor cells were injected either subcutaneously or i.p. Simultaneously, graded doses of various effector cell populations were injected i.v. and the mice were counted daily to assess the potential elimination of the radiolabeled tumor cells. Thus, allogeneic 2 degrees mixed leukocyte culture cells were observed to eliminate allogeneic but not syngeneic tumor cells in a dose-dependent manner, with as few as 0.2 x 10(6) effector cells causing significant destruction of 2 x 10(6) allogeneic tumor cells. The protective effect of the mixed leukocyte culture cells was considerably reduced when Lyt-2+-bearing lymphocytes were eliminated by treatment with monoclonal antibody plus complement. In additional experiments, Lyt-2+ lymphocytes positively selected by enrichment on antibody-coated petri dishes gave efficient protection, in the absence of Lyt-2- cells. Surprisingly, when several different cloned, specific, long-term allogeneic cytolytic T cells lines were injected either i.p. of i.v., tumor cell destruction was observed only after i.p. injection.     

Bombesin production by human small cell carcinoma of the lung

A series of continuous cell lines of human small cell carcinoma of the lung (SCCL) have been evaluated for the production of bombesin (BN). In early established cultures BN was detected in the medium of 9 out of 11 cell lines and in 6 out of 7 cell homogenates examined. Levels in the medium were frequently higher in cultures of later passages compared to earlier passages of the same line and low levels developed in the two previously negative cell lines. Plasma concentrations were greater than 80 pmol/l in 2 out of 27 (7%) randomly selected patients with SCCL. A culture (DMS 406) established from the tumor of a patient with the highest plasma level (1240 pmol/l) was the highest producer in vitro. The results indicate that BN, which has been demonstrated immunocytochemically to be present in normal bronchial mucosal cells, is frequently produced by SCCL in vitro but elevated plasma levels are infrequently found in patients with this neoplasm.     

Genetic control and intracellular localization of glutamate oxaloacetic transaminase in maize

Glutamate oxaloacetic transaminase (L-aspertate: 2-oxoglutarate aminotransferase, E.C. 2.6.1.1; GOT) was found to occur in five distinct electrophoretic forms in different tissue extracts from a number of highly inbred strains of Zea mays L. No major qualitative differences were detected in the various tissues examined, and the isozyme patterns did not undergo changes during temporal development of any given inbred strain. Cell fractionation studies showed one isozyme to be associated with the mitochondria (mGOT), another to be exclusively associated with the soluble fraction (sGOT), and a third to be associated with the glyoxysomes (gGOT). The glyoxysomal form occurs as two electrophoretically distinct variants which exist in different inbred strains of maize. The gGOT variants are under the control of two codiminant alleles (Got1A and Got1B) at the Got1 locus (isozyme5, gGOT). The genetic data and gene dosage effects suggest that GOT in maize is functionally a dimer.     

A study on the minimum number of loci required for genetic evaluation using a finite locus model

For a finite locus model, Markov chain Monte Carlo (MCMC) methods can be used to estimate the conditional mean of genotypic values given phenotypes, which is also known as the best predictor (BP). When computationally feasible, this type of genetic prediction provides an elegant solution to the problem of genetic evaluation under non-additive inheritance, especially for crossbred data. Successful application of MCMC methods for genetic evaluation using finite locus models depends, among other factors, on the number of loci assumed in the model. The effect of the assumed number of loci on evaluations obtained by BP was investigated using data simulated with about 100 loci. For several small pedigrees, genetic evaluations obtained by best linear prediction (BLP) were compared to genetic evaluations obtained by BP. For BLP evaluation, used here as the standard of comparison, only the first and second moments of the joint distribution of the genotypic and phenotypic values must be known. These moments were calculated from the gene frequencies and genotypic effects used in the simulation model. BP evaluation requires the complete distribution to be known. For each model used for BP evaluation, the gene frequencies and genotypic effects, which completely specify the required distribution, were derived such that the genotypic mean, the additive variance, and the dominance variance were the same as in the simulation model. For lowly heritable traits, evaluations obtained by BP under models with up to three loci closely matched the evaluations obtained by BLP for both purebred and crossbred data. For highly heritable traits, models with up to six loci were needed to match the evaluations obtained by BLP.     

A focus on fixation

Three fixation issues related to immunostaining are discussed here: 1) Generally, a tissue block is fixed, then embedded and sectioned (pre-fixation). The type of fixative applied, crosslinking or coagulating, has an impact on selecting an epitope retrieval method. Individual antigens have a fixation–retrieval characteristic. 2) A long fixation time, especially with crosslinking fixatives, may compromise the result of immunostaining. This negative effect varies among different antigens and can be partially restored by applying a more sensitive/efficient detection system such as tyramide amplification. 3) Sections cut from a fresh frozen tissue block usually are acetone fixed (post-fixation). This was accepted as the “gold standard” for a long time. Post-fixation, however, may have serious consequences for preservation of small peptides leaking from the cut open cells, whereas this is not the case with pre-fixed intact cells. Consequently, the concept of an acetone post-fixed cryostat tissue section as “gold standard” no longer exists and a more appropriate use of the terms immunohistochemistry and immunocytochemistry therefore seems justified. For many antibodies, it is not known whether a formalin fixed, paraffin embedded tissue specimen is appropriate. Suggestions are made for creating a positive control cell block for testing such antibodies.     

Do habitat shifts drive diversification in teleost fishes? An example from the pufferfishes (Tetraodontidae)

Habitat shifts are implicated as the cause of many vertebrate radiations, yet relatively few empirical studies quantify patterns of diversification following colonization of new habitats in fishes. The pufferfishes (family Tetraodon‐tidae) occur in several habitats, including coral reefs and freshwater, which are thought to provide ecological opportunity for adaptive radiation, and thus provide a unique system for testing the hypothesis that shifts to new habitats alter diversification rates. To test this hypothesis, we sequenced eight genes for 96 species of pufferfishes and closely related porcupine fishes, and added 19 species from sequences available in GenBank. We time‐calibrated the molecular phylogeny using three fossils, and performed several comparative analyses to test whether colonization of novel habitats led to shifts in the rate of speciation and body size evolution, central predictions of clades experiencing ecological adaptive radiation. Colonization of freshwater is associated with lower rates of cladogenesis in pufferfishes, although these lineages also exhibit accelerated rates of body size evolution. Increased rates of cladogenesis are associated with transitions to coral reefs, but reef lineages surprisingly exhibit significantly lower rates of body size evolution. These results suggest that ecological opportunity afforded by novel habitats may be limited for pufferfishes due to competition with other species, constraints relating to pufferfish life history and trophic ecology, and other factors.     

Association between pygmy right whales (Caperea marginata) and areas of high marine productivity off Australia and New Zealand

Abstract

Opportunistic sightings and strandings of Caperea marginata (n=196) from the vicinity of Australia and New Zealand (1884 to early 2007) were used to relate geographic and temporal patterns to oceanographic and broad-scale climatic variability. Records were not uniformly distributed along the coast and more (69%) were from Australia than New Zealand. Seven coastal whale ‘hotspots’ were identified which accounted for 61% of records with locality data. Half of the hotspot records were from southeast (37) and northwest (20) Tasmania—others each had 9–15 events. Upwelling and/or high zooplankton abundance has been documented near all whale hotspots. Records of C. marginata occurred in all months, with 75% in spring and summer. Inter-annual variability showed broad agreement between increased whale records (usually in spring/summer) and strongly positive ‘Niño 3.4’ during 1980–1995 but not thereafter. Coastal upwelling and productivity increase during climatic phenomena such as El Niño and are likely to be quickly beneficial to plankton-feeding whales such as C. marginata.