A phylogenetic analysis of species in the Bufo crucifer group (Anura: Bufonidae), based on indolealkylamines and proteins from skin secretions

This research tested the utility of two classes of skin secretion compounds to the phylogeny of the Bufo crucifer group. Skin secretions from specimens of nine populations of B. crucifer group were obtained and submitted to qualitative analysis. We observed a clear difference in the composition of the skin secretion molecules obtained from the species of Bufo studied. Fifty-nine molecules, 16 indolealkylamines and 43 proteins, were used as characters, and 39 of these were parsimonious informative. The tree topology of the skin secretion combined data showed areas of congruence and conflict when compared to an mtDNA phylogeny of the B. crucifer group. We used the Templeton test to evaluate the heterogeneity between the skin secretion and mtDNA data. Although not recommended, we performed a combined analysis with the two partitions. The skin secretion characters from the species of Bufo studied have phylogenetic signal. These data are indicative, at least as a preliminary study, of the phylogenetic relationships among the B. crucifer group taxa.     

Liver Accumulation of Plasmodium chabaudi-Infected Red Blood Cells and Modulation of Regulatory T Cell and Dendritic Cell Responses

It is postulated that accumulation of malaria-infected Red Blood Cells (iRBCs) in the liver could be a parasitic escape mechanism against full destruction by the host immune system. Therefore, we evaluated the in vivo mechanism of this accumulation and its potential immunological consequences. A massive liver accumulation of P. c. chabaudi AS-iRBCs (Pc-iRBCs) was observed by intravital microscopy along with an over expression of ICAM-1 on day 7 of the infection, as measured by qRT-PCR. Phenotypic changes were also observed in regulatory T cells (Tregs) and dendritic cells (DCs) that were isolated from infected livers, which indicate a functional role for Tregs in the regulation of the liver inflammatory immune response. In fact, the suppressive function of liver-Tregs was in vitro tested, which demonstrated the capacity of these cells to suppress naive T cell activation to the same extent as that observed for spleen-Tregs. On the other hand, it is already known that CD4+ T cells isolated from spleens of protozoan parasite-infected mice are refractory to proliferate in vivo. In our experiments, we observed a similar lack of in vitro proliferative capacity in liver CD4+ T cells that were isolated on day 7 of infection. It is also known that nitric oxide and IL-10 are partially involved in acute phase immunosuppression; we found high expression levels of IL-10 and iNOS mRNA in day 7-infected livers, which indicates a possible role for these molecules in the observed immune suppression. Taken together, these results indicate that malaria parasite accumulation within the liver could be an escape mechanism to avoid sterile immunity sponsored by a tolerogenic environment.     

Generation of excited species catalyzed by horseradish peroxidase or hemin in the presence of reduced glutathione and H2O2

Horseradish peroxidase (HRP) (EC 1.11.1.7) catalyzes the oxidation of reduced glutathione. This reaction is accompanied by light emission, which is attributed to the generation of singlet oxygen. The chemiluminescence is directly related to thiyl radical formation, as deduced from the correlation between the time course of HRP-compound II formation and light emission in the presence of different amounts of H2O2. Superoxide dismutase has an inhibitory effect on the chemiluminescence without affecting the HRP-compound II formation. This indicates the direct involvement of superoxide radicals in the production of photoemissive species. Replacement of HRP by hemin is also accompanied by chemiluminescence.     

Screening of yeasts for production of xylitol fromd-xylose and some factors which affect xylitol yield inCandida guilliermondii

Summary The ability to convertd-xylose to xylitol was screened in 44 yeasts from five genera. All but two of the strains produced some xylitol with varying rates and yields. The best xylitol producers were localized largely in the speciesCandida guilliermondii andC. tropicalis. Factors affecting xylitol production by a selectedC. guilliermondii strain, FTI-20037, were investigated. The results showed that xylitol yield by this strain was affected by the nitrogen source. Yield was highest at 30–35°C, and could be increased with decreasing aeration rate. Using high cell density and a defined medium under aerobic conditions, xylitol yield byC. guilliermondii FTI-20037 from 104 g/ld-xylose was found to be 77.2 g/l. This represented a yield of 81% of the theoretical value, which was computed to be 0.9 mol xylitol per mold-xylose.Issued as NRCC publication No. 28798.     

Chemiluminescent oxidation of ribose catalyzed by horseradish peroxidase in presence of hydrogen peroxide

The reaction of ribose with horseradish peroxidase in the presence of H₂O₂ is accompanied by light emission. The detection of horseradish peroxidase Compound II (FeO²⁺) indicates that the enzyme participates in a normal peroxidatic cycle. Hydrogen peroxide converts horseradish peroxidase into Compound I (FeO³⁺) which in turn is converted into Compound II by abstracting a hydrogen atom from ribose forming a ribosyl radical. In aerated solutions oxygen rapidly adds to the ribosyl radical. Based on the spectral characteristics and the enhancement of the chemiluminescence by chlorophyll-a, xanthene dyes, D₂O and DABCO, it is suggested that the excited species, apparently triplet carbonyls and ¹O₂, are formed from the bimolecular decay of the peroxyl radicals via the Russell mechanism.     

Maintenance of Weight Loss: A Needs Assessment

This study identified facilitators and obstacles to maintenance of weight loss following a very-low-calorie-diet and behavior modification program. A survey was mailed to a random sample of 178 program completers and received a 61% response rate; the most frequent follow-up period was more than 2 years. Twenty-nine percent reported weighing the same (within 10 lbs) or less than the end of their participation in the treatment program (maintainers), while 71% reported their present weight was a mean of 65% higher than their initial weight loss (regainers). Maintainers were significantly more likely to report engaging in regular aerobic exercise, attending a maintenance support group, and confidence in their ability to manage their weight in the future, while regainers were more likely to report stress and motivation as frequent weight management obstacles. Respondents consistently identified the need for low/no cost ongoing support. Maintainers and relapsers reported similar challenges in managing their weight, yet with different results, suggesting the need to identify subgroups for which different post-treatment support options could be applied.     

Submaximal,aerobic exercise training exacerbates the cardiomyopathy of postweanling Cu-depleted rats

To determine the dual effect of exercise training and copper depletion on myocardial function and ultrastructure, postweanling rats were either trained or sedentary while fed copper-adequate or copper-deficient diets for 8 wk. Rats developed characteristic myocardial subcellular degeneration and increased cardiac mitochondrial volume density when copper depleted, despite lack of overt cardiac hypertrophy, hypertension, or anemia. Training combined with copper depletion induced mild left ventricular hypertrophy. Basal laminae appeared fractionated in areas at capillary-myocyte interface, with focal pericapillary and interstitial collagen accumulation, where-as overt fibrosis was absent or minimal. Electrocardiograms revealed increased QRS wave and QT duration and notching of QRS complex with copper depletion, consistent with intraventricular conductance disturbances. The oxidative capacity of soleus muscle increased with training in copper-adequate rats, but was reduced with progressive copper depletion. These data suggest that copper depletion and training are synergistic in effecting focal accumulation of collagen, with deleterious effect on exercise capacity.     

Ranking species based on sensitivity to perturbations under non-equilibrium community dynamics

Managing ecological communities requires fast detection of species that are sensitive to perturbations. Yet, the focus on recovery to equilibrium has prevented us from assessing species responses to perturbations when abundances fluctuate over time. Here, we introduce two data-driven approaches (expected sensitivity and eigenvector rankings) based on the time-varying Jacobian matrix to rank species over time according to their sensitivity to perturbations on abundances. Using several population dynamics models, we demonstrate that we can infer these rankings from time-series data to predict the order of species sensitivities. We find that the most sensitive species are not always the ones with the most rapidly changing or lowest abundance, which are typical criteria used to monitor populations. Finally, using two empirical time series, we show that sensitive species tend to be harder to forecast. Our results suggest that incorporating information on species interactions can improve how we manage communities out of equilibrium.