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排序方式: 共有661条查询结果,搜索用时 31 毫秒
31.
Bustamante JM Rivarola HW Fernández AR Enders JE Fretes R Palma JA Paglini-Oliva PA 《International journal for parasitology》2002,32(7):889-896
In two murine models we studied Trypanosoma cruzi reinfection in the acute and chronic phase of experimental Chagas' disease in order to elucidate the relevance of reinfections in determining the variability of cardiac symptoms and the irreversible cardiac damage. They were followed for 120 and 600 days post infection (p.i.) for the acute and chronic model, respectively. Reinfected mice reached higher parasitaemia levels than infected mice. The survival was 33 and 21% in the chronic phase for mice reinfected in the acute phase and 13% for mice reinfected in the chronic stage at the end of the experiments. Sixty-six percent of the infected group presented electrocardiographic abnormalities (heart frequency, prolonged PQ segment or QRS complex) in the chronic stage whereas 100% of the reinfected animals exhibited electric cardiac dysfunction since 90 and 390 days p.i. for the acute and chronic reinfected model, respectively (P<0.01). Heart histopathological studies showed fibrosis and necrosis areas and mononuclear infiltrates supporting the view that parasite persistence is a major factor in continuing the tissue inflammation. This work shows that T. cruzi reinfections could be related to the variability and severity of the clinical course of Chagas' disease and that parasite persistence is involved in exacerbation of the disease. 相似文献
32.
Adebodun F Scott CE Cunningham C Bustamante PM Bradshaw A Ping L Williams KR 《Cell biochemistry and function》2000,18(1):59-66
Elevated levels of intracellular Ca(II) are a prominent feature of apoptosis, a natural form of cell death involved in many physiological and pathological processes. Serine proteases play crucial roles in apoptosis and have been implicated in the genomic DNA degradation and the massive protein degradation that occur during apoptosis. In this study, the effects of the elevated level of Ca(II) on the activity and inhibition of serine proteases were examined by spectrophotometric methods. The effects of the elevated levels of Ca(II), Mg(II), K(I), and Na(I) on the activity and inactivation of three representative members of serine proteases were determined. The level of serine protease activity in CEM-C7-14 leukemic cells was also evaluated in the presence and absence of dexamethasone-induced apoptosis, and also in the presence of A23187, a Ca(II)-ionophore. Among the four metal-ions studied, only Ca(II) was found to significantly enhance the activity of mammalian serine proteases. Ca(II) was also found to significantly protect the enzymes from inhibition, while the other three metal-ions showed no significant effect on the inactivation of the enzymes. Compared to the control sample, the enzymic activity was found to be higher during apoptosis, and in the presence of the Ca(II)-ionophore. Results of this study indicate that Ca(II) can significantly enhance the catalytic efficiency of serine proteases during apoptosis. 相似文献
33.
The neutral theory of molecular evolution predicts that variation within species is inversely related to the strength of purifying selection, but the strength of purifying selection itself must be related to physical constraints imposed by protein folding and function. In this paper, we analyzed five enzymes for which polymorphic sequence variation within Escherichia coli and/or Salmonella enterica was available, along with a protein structure. Single and multivariate logistic regression models are presented that evaluate amino acid size, physicochemical properties, solvent accessibility, and secondary structure as predictors of polymorphism. A model that contains a positive coefficient of association between polymorphism and solvent accessibility and separate intercepts for each secondary-structure element is sufficient to explain the observed variation in polymorphism between sites. The model predicts an increase in the probability of amino acid polymorphism with increasing solvent accessibility for each protein regardless of physicochemical properties, secondary-structure element, or size of the amino acid. This result, when compared with the distribution of synonymous polymorphism, which shows no association with solvent accessibility, suggests a strong decrease in purifying selection with increasing solvent accessibility. 相似文献
34.
van Dijken JP Bauer J Brambilla L Duboc P Francois JM Gancedo C Giuseppin ML Heijnen JJ Hoare M Lange HC Madden EA Niederberger P Nielsen J Parrou JL Petit T Porro D Reuss M van Riel N Rizzi M Steensma HY Verrips CT Vindeløv J Pronk JT 《Enzyme and microbial technology》2000,26(9-10):706-714
To select a Saccharomyces cerevisiae reference strain amenable to experimental techniques used in (molecular) genetic, physiological and biochemical engineering research, a variety of properties were studied in four diploid, prototrophic laboratory strains. The following parameters were investigated: 1) maximum specific growth rate in shake-flask cultures; 2) biomass yields on glucose during growth on defined media in batch cultures and steady-state chemostat cultures under controlled conditions with respect to pH and dissolved oxygen concentration; 3) the critical specific growth rate above which aerobic fermentation becomes apparent in glucose-limited accelerostat cultures; 4) sporulation and mating efficiency; and 5) transformation efficiency via the lithium-acetate, bicine, and electroporation methods. On the basis of physiological as well as genetic properties, strains from the CEN.PK family were selected as a platform for cell-factory research on the stoichiometry and kinetics of growth and product formation. 相似文献
35.
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37.
José C. Aponte Abraham J. Vaisberg Denis Castillo German Gonzalez Yannick Estevez Jorge Arevalo Miguel Quiliano Mirko Zimic Manuela Verástegui Edith Málaga Robert H. Gilman Juan M. Bustamante Rick L. Tarleton Yuehong Wang Scott G. Franzblau Guido F. Pauli Michel Sauvain Gerald B. Hammond 《Bioorganic & medicinal chemistry》2010,18(8):2880-2886
The synthesis of 2-(5,6,7,8-tetrahydro[1]benzothieno[2,3-d]pyrimidin-4-yl)hydrazone-derivatives (BTPs) and their in vitro evaluation against Trypanosoma cruzi trypomastigotes, Mycobacterium tuberculosis, Leishmania amazonensis axenic amastigotes, and six human cancer cell lines is described. The in vivo activity of the most active and least toxic compounds against T. cruzi and L. amazonensis was also studied. BTPs constitute a new family of drug leads with potential activity against infectious diseases. Due to their drug-like properties, this series of compounds can potentially serve as templates for future drug-optimization and drug-development efforts for use as therapeutic agents in developing countries. 相似文献
38.
Viviana A. Cavieres Alexis González Vanessa C. Mu?oz Claudia P. Yefi Hianara A. Bustamante Rafael R. Barraza Cheril Tapia-Rojas Carola Otth María José Barrera Carlos González Gonzalo A. Mardones Nibaldo C. Inestrosa Patricia V. Burgos 《PloS one》2015,10(8)
Alzheimer''s disease (AD) is a neurodegenerative disorder characterized by the accumulation of amyloid-β (Aβ) peptide. We have previously shown that the compound tetrahydrohyperforin (IDN5706) prevents accumulation of Aβ species in an in vivo model of AD, however the mechanism that explains this reduction is not well understood. We show herein that IDN5706 decreases the levels of ER degradation enhancer, mannosidase alpha-like 1 (EDEM1), a key chaperone related to endoplasmic-reticulum-associated degradation (ERAD). Moreover, we observed that low levels of EDEM1 correlated with a strong activation of autophagy, suggesting a crosstalk between these two pathways. We observed that IDN5706 perturbs the glycosylation and proteolytic processing of the amyloid precursor protein (APP), resulting in the accumulation of immature APP (iAPP) in the endoplasmic reticulum. To investigate the contribution of autophagy, we tested the effect of IDN5706 in Atg5-depleted cells. We found that depletion of Atg5 enhanced the accumulation of iAPP in response to IDN5706 by slowing down its degradation. Our findings reveal that IDN5706 promotes degradation of iAPP via the activation of Atg5-dependent autophagy, shedding light on the mechanism that may contribute to the reduction of Aβ production in vivo. 相似文献
39.
Leonardo D. Bacigalupe Diego M. Bustamante Francisco Bozinovic Roberto F. Nespolo 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2010,180(2):293-299
A major goal of evolutionary physiology is to understand the intrinsic and the extrinsic factors that impose limitations on
an animal’s energy budget. Although natural selection acts upon organismal traits such as performance (e.g., burst, sustained
metabolic rates), from a mechanistic perspective, organismal performance results from the integrated functioning of different
levels of biological organization. Hence, a better understanding of whole-animal performance must necessarily incorporate
an explicit analysis of the integration between those different levels. Although this topic has been under intense scrutiny,
overall there have been very few consistent patterns. Here, we explore the phenotypic integration between organ masses and
the overall energy budget under routine capacities by statistically decomposing the covariance matrix (using path analysis
and canonical correlation analysis) between organ masses and thermoregulatory burst and sustained metabolisms in cold acclimated
individuals of Phyllotis darwini. Our results suggest that (a) central organs associated with the processing of food (cecum and liver), residuals (kidneys)
and pumping of O2 (heart) are tightly integrated to sustained expenditure and between themselves; (b) with the exception of the heart, central
energy supplying organs are weakly related to burst expenditures; (c) sustained and burst metabolisms refer to complete different
strategies and (d) basal metabolic rate is not related to any of the physiological or morphological traits considered in this
study. Overall, our results support the hypothesis of an economic phenotype: animals maintain their excess capacities to face
those critical extreme events, but their physiology and internal morphology are tightly integrated to function under routine
needs. 相似文献
40.
Julieta Pedrana Javier Bustamante Alejandro Travaini Alejandro Rodríguez 《Biodiversity and Conservation》2010,19(12):3499-3512
The Guanaco (Lama guanicoe) has suffered a progressive decline in numbers because of unregulated hunting and poaching by an assumed competition with
sheep. Inadequate livestock management, including keeping sheep numbers above carrying capacity, has led to a degradation
of the Patagonian steppe. Recently, interest has grown towards a reduction in sheep density and diversification of extractive
activities. Guanaco populations could be potentially amenable to a number of sustainable uses. Our aim was to investigate
the factors that determine guanaco distribution in southern Argentine Patagonia and to generate a predictive cartography at
the regional scale. We hypothesized that guanaco distribution could be determined by primary productivity, terrain ruggedness,
human disturbance and poaching, and competition with livestock. Guanaco surveys were performed from vehicles using a road
survey method. To analyze the relationship between guanaco occurrence and potential predictors we built Generalized Additive
Models (GAMs) using a binomial error and a logistic link. We found that guanaco occurrence increased in the less productive
and remote areas, far from cities and oil camps, and decreased in regions with high sheep density. These results suggest that
guanacos tend to occur where human pressure is lower. One way to promote guanaco conservation would be to highlight the economic
value of guanacos under the regulations imposed by a sustainable exploitation of their populations. The predictive models
developed here could be a useful tool for the implementation of conservation and management programs at the regional scale. 相似文献