Survey of Tall-Fescue Pasture: Correlation of Toxicity of Fusarium Isolates to Known Toxins

Several aspects of fescue foot in cattle suggest that this disease is caused by fungi growing on fescue grass. Certain fungi isolated from winter pasture yield toxins when grown on synthetic medium. Most of these toxin producers belong to the genus Fusarium. All but 1 of the 21 toxic and 7 questionably toxic Fusarium isolates produce either 4-acetamido-4-hydroxy-2-butenoic acid γ-lactone, or 4β, 15-diacetoxy-8α-(3-methylbutyryloxy)-12, 13-epoxytrichothec-9-en-3α-ol, or both.     

Changes in the sciatic nerve of the rabbit and its tissue constituents during development

Abstract— A segment, defined by gross anatomic boundaries, which comprises most of the sciatic nerve was dissected from rabbits aged from birth to 1 yr. The mean and standard deviation of the variance determined for the weights of pairs of nerve units removed from single animals of an age group did not exceed 2·7 per cent and 12·3 per cent respectively of the average weight of the two nerve units which were the values determined for a group of newborn animals. During the period from birth to one year of age, the weight and length of the nerve unit increased 47- and 6-fold respectively while the animal's weight increased 78-fold. Whereas the nerve unit length increased little after 8 weeks, its weight and that of the whole animal continued to increase up to 1 year. Estimations of nucleic acids in the nerve unit from adult animals gave values of 54 μg DNA-P and 25 μg RNA-P per g fresh weight. During the period birth to 1 yr the absolute amount of DNA in the nerve unit increased 11-fold, 71 per cent of this having occurred by 6 weeks of age. The absolute amount of RNA increased 11 -fold by 8 weeks of age and remained constant thereafter. During the period birth to 1 yr, the proportion of the nerve constituents accounted for by lipid-free solids remained constant at 10 per cent, while lipids increased from 5 to 18 per cent and tissue water declined from 84 to 71 per cent. Changes in some lipid classes were examined also. Increases of absolute content in the nerve unit over the first year and concentrations on a fresh weight basis attained in year-old animals were as follows: cholesterol, 132-fold and 86 mg/g; triglyceride 554-fold and 43·2 mg/g; total phospholipid, 85-fold and 61 mg/g; cerebroside 205-fold and 28 μmol/g; sulphatide, 154-fold and 10 μmol/g; monogalactosyl diglyceride, 31-fold and 0·6 μmol/g. The ratio cholesterol/phospholipid/galactolipid in whole nerve units from adult animals was 2·0/2·1/1·0 and the change in this ratio in the first year was compatible with enrichment of myelin in galactolipid during myelination. The ratio of cerebroside to sulphatide increased from 2·0 to 2·6 during this period. Increases in absolute content and concentrations attained for sialic acid-containing components representing cell surface constituents were as follows: ganglioside sialic acid, 33-fold, and 83 μg/g; glycoprotein sialic acid, 57-fold and 371 μg/g. The quantitative pattern of ganglioside fractions separated by thin-layer chromatography in one direction resembled that of whole brain and was the same at all ages studied. The changes reported reflect a composite picture of changes in a variety of cell membranes indicative of marked variation during development in quantity and composition of membranes.     

Contemporary pollen-mediated gene immigration reflects the historical isolation of a rare,animal-pollinated shrub in a fragmented landscape

Fragmentation is generally considered to have negative impacts on widespread outbreedersbut impacts on gene flow and diversity in patchy, naturally rare, self-compatible plantspecies remain unclear. We investigated diversity, gene flow and contemporarypollen-mediated gene immigration in the rare, narrowly distributed endemic shrubCalothamnus quadrifidus ssp. teretifolius. This taxon occurs in aninternationally recognized biodiversity hotspot subjected to recent human-inducedfragmentation and the condition of the remnants ranges from intact to highly degraded.Using microsatellites, we found that inbreeding, historically low gene flow andsignificant population differentiation have characterized the genetic system of C.quadrifidus ssp. teretifolius. Inbreeding arises from self-pollination, asmall amount of biparental inbreeding and significant correlation of outcross paternitybut fecundity was high suggesting populations might have purged their lethals. Paternityanalyses show that pollinators can move pollen over degraded and intact habitat butpopulations in both intact and degraded remnants had few pollen parents per seed parentand low pollen immigration. Genetic diversity did not differ significantly between intactand degraded remnants but there were signs of genetic bottlenecks and reduced diversity insome degraded remnants. Overall, our study suggests human-induced fragmentation has notsignificantly changed the mating system, or pollen immigration to, remnant populations andtherefore genetic connectivity need not be the highest conservation priority. Rather, forrare species adapted to higher levels of inbreeding, conservation efforts may be bestdirected to managing intact habitats and ecosystem processes.     

Gangliosides Inhibit Platelet-Derived Growth Factor-Stimulated Receptor Dimerization in Human Glioma U-1242MG and Swiss 3T3 Cells

Abstract: We previously showed that gangliosides inhibit DNA synthesis in Swiss 3T3 cells stimulated with platelet-derived growth factor (PDGF) in a dose-responsive manner. This correlated with the inhibitory effects of several gangliosides (except GM3) on tyrosine phosphorylation of the PDGF receptor (PDGFR). [³⁵S]Methionine-labeled Swiss 3T3 cells were incubated either with or without gangliosides and stimulated with PDGF, and proteins were cross-linked with bis(sulfosuccinimidyl) suberate. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that two protein bands (170 and 350 kDa) were specifically immunoprecipitated with an anti-PDGFR antibody. Using both Swiss 3T3 and human glioma U-1242MG cells, western blots with anti-PDGFR and anti-phosphotyrosine antibodies confirmed that these bands were the PDGFR monomer and dimer, respectively, and that phosphotyrosine was present in these bands only after cells were stimulated with PDGF. Of the gangliosides tested, GM1, GM2, GD1a, GD1b, GD3, and GT1b, but not GM3, inhibited the formation of the 350-kDa band. These results demonstrate that all gangliosides tested, except GM3, probably inhibit PDGF-mediated growth by preventing dimerization of PDGFR monomers. Loss of more complex gangliosides in human gliomas would permit unregulated activation of the PDGFR, contributing to uncontrolled growth stimulation. We propose that ganglioside inhibition of receptor dimerization is a novel mechanism for regulating and coordinating several trophic factor-mediated cell functions.     

High-throughput screening assay for sphingosine kinase inhibitors in whole blood using RapidFire® mass spectrometry

To facilitate discovery of compounds modulating sphingosine-1-phosphate (S1P) signaling, the authors used high-throughput mass spectrometry technology to measure S1P formation in human whole blood. Since blood contains endogenous sphingosine (SPH) and S1P, mass spectrometry was chosen to detect the conversion of an exogenously added 17-carbon-long variant of sphingosine, C17SPH, into C17S1P. The authors developed procedures to achieve homogeneous mixing of whole blood in 384-well plates and for a method requiring minimal manipulations to extract S1P from blood in 96- and 384-well plates prior to analyses using the RapidFire(?) mass spectrometry system.