Properties of L1210 cells resistant to α-difluoromethylornithine

L1210 cells were selected for resistance to the ornithine decarboxylase (ODC) inhibitor, α-difluromethylornithine. When grown in the absence of the inhibitor, these cells possessed very high ornithine decarboxylase levels. These represented about 1 part in 300 of the soluble protein, which is several hundred times greater than the maximal value found in the original L1210 cells. The resistant cells contained at least 100-fold higher levels of ODC mRNA but the half-life of ODC (about 45 min) was not altered significantly. The resistant cells had much higher putrescine and cadaverine levels than control cells, but there was no significant difference in cellular spermidine or spermine content or in production of 5'-methylthioadenosine, which is a measure of polyamine synthesis. Addition of putrescine to the control or resistant cells had no effect on their content of spermidine and spermine but addition of decarboxylated S-adenosylmethionine increased the content of spermidine and spermine. These results indicate that ornithine decarboxylase is not the rate-limiting step in polyamine synthesis in these L1210 cells. The growth of the α -difluoromethylornithine-resistant L1210 cells was inhibited when their ability to synthesize spermidine and spermine was blocked by the addition of the S-adenosylmethionine decarboxylase inhibitor, 5'-deoxy-5'-[N-methyl-N-(3-hydrazinopropyl)]aminoadenosine. Treatment with this compound produced a reduction of more than 85% in the production of 5'-methylthioadenosine and led to a large increase in the content of putrescine and a substantial decline in the content of spermidine and spermine. These results indicate the potential value of S-adenosylmethionine decarboxylase inhibitors as therapeutic agents in conditions where ODC inhibitors are ineffective

Detecting the influence of initial pioneers on succession at deep-sea vents

© The Author(s), 2012. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in PLoS One 7 (2012): e50015, doi:10.1371/journal.pone.0050015.Deep-sea hydrothermal vents are subject to major disturbances that alter the physical and chemical environment and eradicate the resident faunal communities. Vent fields are isolated by uninhabitable deep seafloor, so recolonization via dispersal of planktonic larvae is critical for persistence of populations. We monitored colonization near 9°50′N on the East Pacific Rise following a catastrophic eruption in order to address questions of the relative contributions of pioneer colonists and environmental change to variation in species composition, and the role of pioneers at the disturbed site in altering community structure elsewhere in the region. Pioneer colonists included two gastropod species: Ctenopelta porifera, which was new to the vent field, and Lepetodrilus tevnianus, which had been rare before the eruption but persisted in high abundance afterward, delaying and possibly out-competing the ubiquitous pre-eruption congener L. elevatus. A decrease in abundance of C. porifera over time, and the arrival of later species, corresponded to a decrease in vent fluid flow and in the sulfide to temperature ratio. For some species these successional changes were likely due to habitat requirements, but other species persisted (L. tevnianus) or arrived (L. elevatus) in patterns unrelated to their habitat preferences. After two years, disturbed communities had started to resemble pre-eruption ones, but were lower in diversity. When compared to a prior (1991) eruption, the succession of foundation species (tubeworms and mussels) appeared to be delayed, even though habitat chemistry became similar to the pre-eruption state more quickly. Surprisingly, a nearby community that had not been disturbed by the eruption was invaded by the pioneers, possibly after they became established in the disturbed vents. These results indicate that the post-eruption arrival of species from remote locales had a strong and persistent effect on communities at both disturbed and undisturbed vents.The authors received funding from National Science Foundation grant OCE-0424953, WHOI Deep Ocean Exploration Institute, WHOI Summer Student Fellow program, Woods Hole Partnership in Education Program, IFREMER and CNRS, Fondation TOTAL Chair Extreme Marine Environment, Biodiversity and Global change

The GTPase-Activating Protein of Ras Suppresses Platelet-Derived

receptor signaling by silencing phospholipase suppresses platelet-derived growth factor beta The GTPase-activating protein of Ra

Sensory and Instrumental Texture Properties of Flaked and Formed Beef

Four experiments were conducted to assess the sensory textural properties, consumer acceptability and instrumental-sensory correlates of flaked and formed beef steaks. In Experiment 1, the effects of additions of NaCI, TPP and soy isolate on the texture of steaks were examined using a trained texture profile panel, and the texture of these steaks was compared to that of intact muscle (ribeye) steaks. Results showed large differences between the flaked and formed samples and the ribeye steak, as contrasted to small differences among the flaked and formed samples treated with different levels of NaCI, TPP and/or soy isolate. In Experiments 2 and 3 the effect of flake size on the texture of flaked and formed beef was examined . In Experiment 2, instrumental shear data and SEM data were col lected and compared to the sensory data. In Experiment 3, a comparison was made of the texture of these products to both ribeye steak and ground beef patties. Systematic differences in a variety of textural attributes were observed as a function of flake-size. In general, the smallest flake-size produced a texture most like ground beef, whereas certain intermediate and large flake sizes produced a texture most like whole muscle steak. Simple and multiple linear regression equations were established between sensory and shear stress measures on these steaks, and these data, combined with the SEM data, suggested that tenderization of these meats is attributable to mechanical disruption of the tissue and not to an enzymatic process. In Experiment 4, a consumer test was conducted to assess the effect of flake -size on the acceptability of flaked and formed steaks, and to assess consumer perception of the similarity of the texture of these products to other beef products. Although few significant differences in the acceptability of the flaked and formed products were observed, maximal acceptability ratings were found for the intermediate flake sizes. In addition, it was found that consumers do not associate the texture of flaked and formed steaks with any one of a variety of traditional beef products

Inosine Analogs as Anti-Leishmanial Agents

Several criteria were used to select a number of inosine analogs as potential growth inhibitors of the protozoan parasite Leishmania tropica . Of nine compounds tested, seven showed a high degree of selective toxicity towards L. tropica promastigotes as compared to mouse L1210 cells; these include analogs of formycin B, 7-substituted analogs of 7-deazainosine and analogs of inosine in which the sugar moiety has been modified to confer metabolic stability. The metabolism of 7-deazainosine in L. tropica promastigotes was shown to involve conversion to cytotoxic adenosine nucleotide analogs (tubercidin derivatives) that become incorporated into RNA. The results suggest several new classes of compounds which have potential as anti-leishmanial agents.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/41494/1/11095_2004_Article_307179.pd