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991.
During the G1/S transition, p21 proteolysis is mediated by Skp2; however, p21 reaccumulates in G2 and is degraded again in prometaphase. How p21 degradation is controlled in mitosis remains unexplored. We found that Cdc20 (an activator of the ubiquitin ligase APC/C) binds p21 in cultured cells and identified a D box motif in p21 necessary for APC/C(Cdc20)-mediated ubiquitylation of p21. Overexpression of Cdc20 or Skp2 destabilized wild-type p21; however, only Skp2, but not Cdc20, was able to destabilize a p21(D box) mutant. Silencing of Cdc20 induced an accumulation of p21, increased the fraction of p21 bound to Cdk1, and inhibited Cdk1 activity in p21(+/+) prometaphase cells, but not in p21(-/-) cells. Thus, in prometaphase Cdc20 positively regulates Cdk1 by mediating the degradation of p21. We propose that the APC/C(Cdc20)-mediated degradation of p21 contributes to the full activation of Cdk1 necessary for mitotic events and prevents mitotic slippage during spindle checkpoint activation. 相似文献
992.
López-Martínez R Hernández-Hernández F Millán-Chiu BE Manzano-Gayosso P Méndez-Tovar LJ 《Revista iberoamericana de micología》2007,24(4):283-288
We present a study on the control and elimination of the fungi affecting the mummies specifically at the museum "El Carmen", in San Angel, Mexico City. Twelve analysed mummies presented an important deterioration attributed to colonizing fungi. The degree of fungal contamination and the efficacy of imazalil were evaluated. Two samplings were performed in order to isolate and identify the fungal genera, one for control and the other after the treatment. Isolation was done by the carpet-square technique and identification was performed by morphological features. Each sampling gave a total of 100 samples as follows: 17 from the air, 23 from the walls and 60 from the mummies. Samples were cultured on Sabouraud dextrose agar. From the first sampling a total of 649 colonies corresponding to 24 genera were obtained being the most frequent Penicillium, Cladophialophora and Aspergillus. From the second sampling, after the imazalil treatment, which was applied by means of lit candles containing the antifungal drug, 57 colonies were recovered, representing a 91.2% fungal reduction; 18 genera were eliminated. In spite of resistance showed by many Penicillium strains, the imazalil is an alternative drug for the control of fungal colonization on these studied materials. 相似文献
993.
Daniel Krewski Victoria Hogan Michelle C. Turner Patricia L. Zeman Ian McDowell Nancy Edwards 《人类与生态风险评估》2007,13(6):1288-1312
The traditional medical model of health and health policy development has focused on individuals and the role of medical care in preventing and treating disease and injury. Recent attention to health inequities and social determinants of health has raised the profile of population heath and evidence-based strategies for improving the health of whole populations. At the same time, risk science has emerged as an important new discipline for the assessment and management of risks to health. This article reviews historical developments in the fields of risk management and population health and proposes a joint population health risk management framework that integrates the key elements of both fields. Applying this integrated approach to managing population health risks will facilitate the development of evidence-based health policy. It will encourage a more systematic and comprehensive evaluation of population health issues and promote the use of a broader suite of interventions to reduce health risks and enhance population health status. 相似文献
994.
Cheng AC Coleman RG Smyth KT Cao Q Soulard P Caffrey DR Salzberg AC Huang ES 《Nature biotechnology》2007,25(1):71-75
Lead generation is a major hurdle in small-molecule drug discovery, with an estimated 60% of projects failing from lack of lead matter or difficulty in optimizing leads for drug-like properties. It would be valuable to identify these less-druggable targets before incurring substantial expenditure and effort. Here we show that a model-based approach using basic biophysical principles yields good prediction of druggability based solely on the crystal structure of the target binding site. We quantitatively estimate the maximal affinity achievable by a drug-like molecule, and we show that these calculated values correlate with drug discovery outcomes. We experimentally test two predictions using high-throughput screening of a diverse compound collection. The collective results highlight the utility of our approach as well as strategies for tackling difficult targets. 相似文献
995.
Schwenke DO Bolter CP Cragg PA 《Comparative biochemistry and physiology. Part A, Molecular & integrative physiology》2007,146(2):180-188
We have previously observed that the guinea-pig appears to have a relatively poor ventilatory (V (E)) response to hypoxia, compared to other mammals. Therefore, in this study, we questioned the ability of the carotid bodies (primary peripheral chemoreceptors) in the guinea-pig to detect hypoxia. The ventilatory responses to poikilocapnic hypoxia (8% O(2)), poikilooxic hypercapnia (8% CO(2)), hyperoxia (100% O(2)) and cyanide (NaCN - 200 mug/kg, i.v.) were assessed before and after carotid body denervation (CBD) in anaesthetized guinea-pigs. Although CBD attenuated the V (E) responses to hypercapnia and cyanide, it had no effect on normoxic breathing or the V (E) responses to hypoxia or hyperoxia. In a separate group of guinea-pigs, nerve activity was recorded from single or few-fibre preparations of the carotid sinus nerve (CSN). Basal chemoreceptor activity could not be detected from any of the nerve preparations. NaCN and hypercapnia consistently provoked an increase in neural activity. In contrast, hypoxia never clearly increased activity in any of the single or few-fibre preparations isolated from the CSN. In conclusion, although the carotid bodies of the guinea-pig, like those of other mammals, are able to detect hypercapnia and histotoxic hypoxia and elicit a reflex increase in V (E), they are essentially hypoxia-insensitive. The latter may explain, at least in part, the relatively poor V (E) response to hypoxia shown by the guinea-pig. 相似文献
996.
Corona-Rivera A Urbina-Cano P Bobadilla-Morales L Vargas-Lares Jde J Ramirez-Herrera MA Mendoza-Magaua ML Troyo-Sanroman R Diaz-Esquivel P Corona-Rivera JR 《Journal of applied genetics》2007,48(4):389-396
Curcumin is a phytochemical with antiinflammatory, antioxidant and anticarcinogenic activities. Apparently, curcumin is not genotoxic in vivo, but in vitro copper and curcumin interactions induce genetic damage. The aim of this study was to test if in vivo copper excess induces DNA damage measured by comet and micronucleus assays in the presence of curcumin. We tested 0.2% curcumin in Balb-C mice at normal (13 ppm) and high (65, 130 and 390 ppm) copper ion concentrations. The comet and micronucleus assays were performed 48 hr after chemical application. Comet tail length in animals treated with 0.2% curcumin was not significantly different from the control. Animals exposed to copper cations (up to 390 ppm) exhibited higher oxidative DNA damage. Curcumin reduced the DNA damage induced by 390 ppm copper. We observed statistically significant increase in damage in individuals exposed to 390 ppm copper versus the control or curcumin groups, which was lowered by the presence of curcumin. Qualitative data on comets evidenced that cells from individuals exposed to 390 ppm copper had longer tails (categories 3 and 4) than in 390 ppm copper + curcumin. A statistically significant increase in frequency of micronucleated erythrocytes (MNE/10000TE) was observed only in 390 ppm copper versus the control and curcumin alone. Also cytotoxicity measured as the frequency of polychromatic erythrocytes (PE/1000TE) was attributable to 390 ppm copper. The lowest cytotoxic effect observed was attributed to curcumin. In vivo exposure to 0.2% curcumin for 48 hr did not cause genomic damage, while 390 ppm copper was genotoxic, but DNA damage induced by 390 ppm copper was diminished by curcumin. Curcumin seems to exert a genoprotective effect against DNA damage induced by high concentrations of copper cations. The comet and micronucleus assays prove to be suitable tools to detect DNA damage by copper in the presence of curcumin. 相似文献
997.
Lima P Sidders B Morici L Reader R Senaratne R Casali N Riley LW 《Microbes and infection / Institut Pasteur》2007,9(11):1285-1290
Mycobacterium tuberculosis causes a variety of host clinical outcomes. We previously showed that M. tuberculosis disrupted in an operon called mce1 proliferates unchecked in BALB/c mouse lungs. The observed outcome could be attributed either to the mutant bacterial burden or to the host immunopathologic response. To differentiate these possibilities, we studied the outcomes of infection in a mouse strain (C57BL/6) less susceptible to M. tuberculosis than BALB/c. We found that the mutant infection reached a plateau in the lungs at a rate similar to that of the wild type. All mice infected with the mutant, but only half of the groups of mice infected with the wild type or complemented strain, died by 40 weeks (p<0.05). At 12-21 weeks of infection, histological examination of the lungs of mice infected with the mutant showed a diffuse pattern of lymphocyte infiltration, while that of mice infected with the other strains exhibited a nodular cellular infiltration pattern. Surprisingly, the number of bacilli recovered from the lungs was similar in all three groups. These observations suggest that rather than the bacterial burden, products of the mce1 operon may directly or indirectly modulate the host immune response that is protective to both the tubercle bacilli and the host. 相似文献
998.
Chávez J Segura P Vargas MH Arreola JL Flores-Soto E Montaño LM 《American journal of physiology. Lung cellular and molecular physiology》2007,292(4):L915-L923
Organophosphates induce bronchoobstruction in guinea pigs, and salbutamol only transiently reverses this effect, suggesting that it triggers additional obstructive mechanisms. To further explore this phenomenon, in vivo (barometric plethysmography) and in vitro (organ baths, including ACh and substance P concentration measurement by HPLC and immunoassay, respectively; intracellular Ca2+) measurement in single myocytes) experiments were performed. In in vivo experiments, parathion caused a progressive bronchoobstruction until a plateau was reached. Administration of salbutamol during this plateau decreased bronchoobstruction up to 22% in the first 5 min, but thereafter airway obstruction rose again as to reach the same intensity as before salbutamol. Aminophylline caused a sustained decrement (71%) of the parathion-induced bronchoobstruction. In in vitro studies, paraoxon produced a sustained contraction of tracheal rings, which was fully blocked by atropine but not by TTX, omega-conotoxin (CTX), or epithelium removal. During the paraoxon-induced contraction, salbutamol caused a temporary relaxation of approximately 50%, followed by a partial recontraction. This paradoxical recontraction was avoided by the M2- or neurokinin-1 (NK1)-receptor antagonists (methoctramine or AF-DX 116, and L-732138, respectively), accompanied by a long-lasting relaxation. Forskolin caused full relaxation of the paraoxon response. Substance P and, to a lesser extent, ACh released from tracheal rings during 60-min incubation with paraoxon or physostigmine, respectively, were significantly increased when salbutamol was administered in the second half of this period. In myocytes, paraoxon did not produce any change in the intracellular Ca2+ basal levels. Our results suggested that: 1) organophosphates caused smooth muscle contraction by accumulation of ACh released through a TTX- and CTX-resistant mechanism; 2) during such contraction, salbutamol relaxation is functionally antagonized by the stimulation of M2 receptors; and 3) after this transient salbutamol-induced relaxation, a paradoxical contraction ensues due to the subsequent release of substance P. 相似文献
999.
Radiolabeled somatostatin analogues have been successfully used for targeted radiotherapy and for imaging of somatostatin receptor (sst1-5)-positive tumors. Nevertheless, these analogues are subject to improving their tumor-to-nontarget ratio to enhance their diagnostic or therapeutic properties, preventing nephrotoxicity. In order to understand the influence of lipophilicity and charge on the pharmacokinetic profile of [1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA)]-somatostatin-based radioligands such as [DOTA,1-Nal3]-octreotide (DOTA-NOC), different spacers (X) based on 8-amino-3,6-dioxaoctanoic acid (PEG2), 15-amino-4,7,10,13-tetraoxapentadecanoic acid (PEG4), N-acetyl glucosamine (GlcNAc), triglycine, beta-alanine, aspartic acid, and lysine were introduced between the chelator DOTA and the peptide NOC. All DOTA-X-NOC conjugates were synthesized by Fmoc solid-phase synthesis. The partition coefficient (log D) at pH = 7.4 indicated that higher hydrophilicity than [111In-DOTA]-NOC was achieved with the introduction of the mentioned spacers, except with triglycine and beta-alanine. The high affinity of [InIII-DOTA]-NOC for human sst2 (hsst2) was preserved with the structural modifications, while an overall drop for hsst3 affinity was observed, except in the case of [InIII-DOTA]-beta-Ala-NOC. The new conjugates preserved the good affinity for hsst5, except for [InIII-DOTA]-Asn(GlcNAc)-NOC, which showed decreased affinity. A significant 1.2-fold improvement in the specific internalization rate in AR4-2J rat pancreatic tumor cells (sst2 receptor expression) at 4 h was achieved with the introduction of Asp as a spacer in the parent compound. In sst3-expressing HEK cells, the specific internalization rate at 4 h for [111In-DOTA]-NOC (13.1% +/- 0.3%) was maintained with [111In-DOTA]-beta-Ala-NOC (14.0% +/- 1.8%), but the remaining derivatives showed <2% specific internalization. Biodistribution studies were performed with Lewis rats bearing the AR4-2J rat pancreatic tumor. In comparison to [111In-DOTA]-NOC (2.96% +/- 0.48% IA/g), the specific uptake in the tumor at 4 h p.i. was significantly improved for the 111In-labeled sugar analogue (4.17% +/- 0.46% IA/g), which among all the new derivatives presented the best tumor-to-kidney ratio (1.9). 相似文献
1000.
Loiselle Bette A.; Ryder Thomas B.; Duraes Renata; Tori Wendy; Blake John G.; Parker Patricia G. 《Behavioral ecology》2007,18(2):287-291
In lek-mating systems, males aggregate at display arenas andfemales visit solely for the purpose of mating. This breedingsystem is characterized by high variance in male mating successwith one male often receiving most copulations. High reproductiveskew among males has led to question why males join leks whentheir chances of reproductive success are so low. Kin selectionhas been invoked as a mechanism to explain the evolution oflekking behavior, whereby nonreproducing but genetically relatedmales gain indirect inclusive-fitness benefits. Evidence forkin selection among lek-mating birds is, however, mixed. Here,we show that kin selection is unlikely to be an important explanationfor evolution of lekking behavior in manakins (Aves: Pipridae).We found that for 4 species chosen from several major cladeswithin Pipridae, males within leks were not significantly morerelated than expected from random assortment of males in thepopulation. This means that nonreproducing males do not gainindirect inclusive-fitness benefits by joining leks. This resultsuggests alternative mechanisms must be invoked to explain theevolution of lek-mating systems in manakins. 相似文献