Targeted disruption of p53 attenuates doxorubicin-induced cardiac toxicity in mice

Use of the chemotherapeutic agent doxorubicin (Dox) is limited by dose-dependent cardiotoxic effects. The molecular mechanism underlying these toxicities are incompletely understood, but previous results have demonstrated that Dox induces p53 expression. Because p53 is an important regulator of the cell birth and death we hypothesized that targeted disruption of the p53 gene would attenuate Dox-induced cardiotoxicity. To test this, female 6–8 wk old C57BL wild-type (WT) or p53 knockout (p53 KO) mice were randomized to either saline or Dox 20 mg/kg via intraperitoneal injection. Animals were serially imaged with high-frequency (14 MHz) two-dimensional echocardiography. Measurements of left ventricle (LV) systolic function as assessed by fractional shortening (FS) demonstrated a decline in WT mice as early as 4 days after Dox injection and by 2 wk demonstrated a reduction of 31± 16% (P < 0.05) from the baseline. In contrast, in p53 KO mice, LV FS was unchanged over the 2 wk period following Dox injection. Apoptosis of cardiac myocytes as measured by the TUNEL and ligase reactions were significantly increased at 24 h after Dox treatment in WT mice but not in p53 KO mice. After Dox injection, levels of myocardial glutathione and Cu/Zn superoxide dismutase were preserved in p53 KO mice, but not in WT animals. These observations suggest that p53 mediated signals are likely to play a significant role in Dox-induced cardiac toxicity and that they may modulate Dox-induced oxidative stress.These two authors equally contributed to this study.     

Phylogeography and Pleistocene demographic history of the endangered marsh deer (Blastocerus dichotomus) from the Río de la Plata Basin

The marsh deer is the largest neotropical cervid with morphological and ecological adaptations to wetlands and riparian habitats. Historically, this now endangered species occupied habitats along the major river basins in South America, ranging from southern Amazonia into northern Argentina to the Paraná river delta. This particularly close association with wetlands makes marsh deer an excellent species for studying the effects of Pleistocene climatic changes on their demographic and phylogeographic patterns. We examined mitochondrial DNA variation in 127 marsh deer from 4 areas distributed throughout the Río de la Plata basin. We found 17 haplotypes in marsh deer from Brazil, Bolivia and Argentina that differed by 1–8 substitutions in a 601 bp fragment of mitochondrial control region sequence, and 486 bp of cytochrome b revealed only 3 variable sites that defined 4 haplotypes. Phylogeny and distribution of control region haplotypes suggest that populations close to the Pantanal area in central Brazil underwent a rapid population expansion and that this occurred approximately 28,000–25,000 years BP. Paleoclimatic data from this period suggests that there was a dramatic increase for precipitation in the medium latitudes in South America and these conditions may have fostered marsh deer’s population growth.     

A field model of learning: 1. Short-term memory in the crab Chasmagnathus granulatus

Learning and memory studies have been performed for more than two decades using the crab Chasmagnathus in our laboratory. Here, our research was aimed at disclosing some instances of learning in field conditions. Three experiments were performed non-simultaneously, all with a 22.5-min pre-training preceding the first visual-danger-stimulus, an opaque rectangle passing overhead. In Experiment 1, crabs received a single stimulus followed by 22.5-min testing without stimulation, where the re-emerging latency was considered the basic latency response. In Experiment 2, training consisted of 15 stimulus 3-min apart, followed by 22.5-min testing without stimulation. Throughout training crabs were underground but re-emerged at testing with latencies longer than the basic latency response. Both at pre-training and testing the usual strategy of exploring was the short-near excursions. In Experiment 3, training included three stimulus 22.5-min apart, followed by 22.5-min testing. Crabs left their burrows before the end of each inter-trial, showing a mean latency like the basic latency response, but a sensitization to the stimulus and a preponderance of the fast-far excursions over the usual slow-near. In brief: through 15-3 training, crabs learn that the stimulus is iteratively presented; through 3-22.5 training, crabs acquire sensitization to the stimulus and a different strategy of exploration.     

Signal transduction in receptor for advanced glycation end products (RAGE): solution structure of C-terminal rage (ctRAGE) and its binding to mDia1

The receptor for advanced glycation end products (RAGE) is a multiligand cell surface macromolecule that plays a central role in the etiology of diabetes complications, inflammation, and neurodegeneration. The cytoplasmic domain of RAGE (C-terminal RAGE; ctRAGE) is critical for RAGE-dependent signal transduction. As the most membrane-proximal event, mDia1 binds to ctRAGE, and it is essential for RAGE ligand-stimulated phosphorylation of AKT and cell proliferation/migration. We show that ctRAGE contains an unusual α-turn that mediates the mDia1-ctRAGE interaction and is required for RAGE-dependent signaling. The results establish a novel mechanism through which an extracellular signal initiated by RAGE ligands regulates RAGE signaling in a manner requiring mDia1.     

Haematological alterations in Rattus norvegicus (Wistar) experimentally infected with Echinostoma paraensei (Trematoda: Echinostomatidae)

Laboratory rats (Rattus norvegicus) were infected with Echinostoma paraensei (Trematoda: Echinostomatidae). The rodents received 150 metacercariae each and blood samples were collected weekly until the fifth week of infection. The blood samples were analyzed for determination of haematocrit, total red blood cells with their dimensions, haemoglobin and haematimetric index (mean corpuscular volume, MCV; mean corpuscular haemoglobin, MCH; and mean corpuscular haemoglobin concentration, MCHC) and platelets. Red blood cells, haematocrit and haemoglobin in the first week had significantly lower levels than those of uninfected (control) rats, suggesting the development of normocytic and normocromic anaemia with anisocytic alteration. The number of eosinophils did not increase significantly among the groups. We concluded that E. paraensei produces haematological alterations in R. norvegicus, causing regenerative anaemia. This system can therefore be a useful model to study the direct and indirect effects of gastrointestinal infections.