Microvertebrates preserved in mammal burrows from the Holocene of the Argentine Pampas: a taphonomic and paleoecological approach

Microvertebrates are a major component of many assemblages recovered from the Quaternary of the Argentine Pampas. The main goal of this paper is to analyse the taphonomic history of a Holocene microfossil bonebed, recovered from the infilling of a burrow. Evidences suggest the plains vizcacha Lagostomus maximus as the putative producer of the burrow. The assemblage includes individuals belonging to different taxa of mammals (marsupials and rodents) and reptiles (snakes). Taphonomic features suggest that the accumulation inside the burrow was related to flooding processes in the plain. The burrow was a natural trap that favoured the accumulation and preservation of remains corresponding to individuals from different sources. According to the taphonomic evidence, some individuals (Lagostomus maximus, Lestodelphys halli and Serpentes indet.) died inside the burrow, whereas others (Microcavia australis, Reithrodon auritus and Ctenomys sp.) died outside the burrow, and after a time of being exposed on the surface their remains were transported by surface run-offs into the burrow. The record of Lestodelphys halli and Serpentes indet. in the burrow produced by Lagostomus maximus could be related to a circumstantial use. Mammal burrows are a significant taphonomic mode for the late Cenozoic of the Argentine Pampas.     

RelB/p50 regulates TNF production in LPS-stimulated dendritic cells and macrophages

Dendritic cells (DCs) and macrophages are effective antigen-presenting cells, and DCs, once matured, have the ability to potently activate naïve T cells. While the canonical p65/p50 NF-κB pathway seems to have an important role during LPS-stimulation of these cells, the specific contribution of the non-canonical RelB/p50 subunits is not clear yet. We aimed to investigate the relevance of this pathway in DCs and macrophages by using replication-deficient adenoviruses overexpressing RelB and p50 subunits to test their effect on cytokine production. In both cells, after LPS treatment, overexpression of RelB and p50 inhibited the production of some pro-inflammatory cytokines e.g., TNF, but not of others e.g. IL6. Anti-inflammatory IL10 was not affected. Moreover, when overexpressing p50 alone, IL10 was increased in LPS-activated macrophages.We thus demonstrated that the dimer RelB/p50 rather than the p50/p50 complex inhibits TNF production in LPS-stimulated DCs and macrophages. This implies that the non-canonical RelB/p50 could modulate the canonical p65/p50 pathway.     

Monoclonal anti-CEA antibody: factors affecting localization in a preclinical study

131I-labelled anti-CEA monoclonal antibody was tested in an animal model to evaluate: influence of antibody type (whole versus F(ab')2 fragments), administration route (i.v. versus i.p.), dose of tracer (100 microCi versus 1000 microCi), growth site (s.c. versus i.p.) and size of tumor. Athymic mice bearing CEA-producing human colon carcinoma (HT-29) or human melanoma as an irrelevant tumor (MeWo) received tracer and immunoscintigraphy and the localization ratios (LR) were compared. In HT-29 bearing animals F(ab')2 fragments localized better than the whole antibody. The LR were higher after i.p. administration of the tracer, independently of the tumor characteristics or the injected dose. The highest values were achieved when the radioactivity remaining in the whole body was below 2% of the injected dose. The images were negative when the i.p. injected dose was low or tumor growth was i.p. but positive in the other conditions (i.v. administration, high tracer dose, s.c. tumor growth). In the animals bearing melanoma, images scored positive or negative when the tumor weight was respectively above or below 400 mg, but the LR were always low.     

Activation of phosphoinositide-specific phospholipase C of rat neutrophils by the chemotactic aldehydes 4-hydroxy-2,3-trans-nonenal and 4-hydroxy-2,3-trans-octenal

A comparison has been made between the effects of 4-hydroxy-2,3-trans-nonenal (HNE) and 4-hydroxy-2,3-trans-octenal (HOE), two lipid peroxidation products, on the basal and GTPgammaS-stimulated activities of phosphoinositide-specific phospholipase C (PL-C) of rat polymorphonuclear leukocytes. PL-C activity was determined in vitro by measuring the hydrolysis of [³H] phosphatidylinositol-4,5-bis-phosphate (PtdIns-P₂) added as exogenous substrate to neutrophil plasma membranes. PL-C was activated by concentrations of HNE ranging from 10^?8 to 10^?6 M both in the presence and in the absence of 2 × 10^?5 M GTPgammaS; HOE stimulated the enzymatic activity between 10^?11 and 10^?8 M ; maximal stimulation was given by 10^?11 M HOE plus GTPgammaS. The aldehyde concentrations able to accelerate PtdIns-P₂ breakdown displayed a good correspondence with those which have been reported to stimulate the oriented migration of rat neutrophils. Pretreatment of neutrophils with pertussis toxin prevented the stimulation of PL-C by 10^?11 M HOE and by HOE plus GTPgammaS. Our results suggest that the chemotactic action of HNE and HOE might depend on the activation of PL-C; furthermore a regulatory G protein appears to be involved in the acceleration of PtdIns-P₂ turnover by HOE.     

Reef fish community structure on coastal islands of the southeastern Brazil: the influence of exposure and benthic cover

Patterns of community structure in the marine environment are strongly influenced by population relationships to biotic and physical gradients. The aim of this work is to explore the relationships of tropical rocky reef fish assemblages to wave exposure and benthic coverage in a gradient of distance from the coast. The study was conducted on the Guarapari Islands, southeastern Brazilian coast. Fish were sampled by underwater visual census (166 transects) and benthic cover was estimated with quadrats (223 replicates). Two main kinds of habitats were found to be derived from the close interrelation between exposure and benthic coverage: (1) exposed areas subjected to major hydrodynamic forcing, and (2) sheltered or moderately exposed areas. The first group is associated with mid-water schooling species like planktivorous labrids and Chromis, piscivorous Caranx, as well as gregarious omnivores like Abudefduf and Diplodus. In terms of benthic composition, macroalgae and encrusting calcareous algae prevail in this high-energy habitat. The second group is characterized by site-attached and reef associated species like territorial pomacentrids, invertebrate feeders such as Halichoeres poeyi and Chaetodon striatus, and small cryptobenthic fishes (e.g. blenniids and labrisomids). Turf algae, zoanthids and massive corals dominate this environment. Environmental plasticity is also common with some genera showing high abundances in all habitats (e.g. Holocentrus, Haemulon, Acanthurus). Examples of the coupling of food availability and fish abundance were found. Planktivores, territorial herbivores, macroalgae browsers and spongivores were positively related with the abundance of their preferred food items along the exposure gradient. Within-family analyses of Pomacentridae and Labridae showed that niche partitioning is likely occurring and seems to be mediated by swimming ‘ability’ and associated feeding performance.     

Glyoxylic acid promotes poly(ADP-ribosyl)ation of nuclear proteins in K562 cells cultured at limiting dilution

Addition of glyoxylic acid to the culture medium allows survival and proliferation of K562 human erythroleukemic cells cultured at low population density in the absence of serum. Concomitantly, glyoxylic acid induces a remarkable increase in nuclear poly(ADP-ribose) content, as compared to control cells cultured without addition of glyoxylate. The latter effect is reversed by addition of micromolar concentrations of benzamide to the cultures. As glyoxylic acid is metabolized through NADH-dependent reduction to glycolic acid only, the observed effects on cell growth and on nuclear poly(ADP-ribose) content seem to be mediated by an increased cellular ability to oxidize NADH.