The Arp2/3 complex mediates actin polymerization induced by the small GTP-binding protein Cdc42

The small GTP-binding protein Cdc42 is thought to induce filopodium formation by regulating actin polymerization at the cell cortex. Although several Cdc42-binding proteins have been identified and some of them have been implicated in filopodium formation, the precise role of Cdc42 in modulating actin polymerization has not been defined. To understand the biochemical pathways that link Cdc42 to the actin cytoskeleton, we have reconstituted Cdc42-induced actin polymerization in Xenopus egg extracts. Using this cell-free system, we have developed a rapid and specific assay that has allowed us to fractionate the extract and isolate factors involved in this activity. We report here that at least two biochemically distinct components are required, based on their chromatographic behavior and affinity for Cdc42. One component is purified to homogeneity and is identified as the Arp2/3 complex, a protein complex that has been shown to nucleate actin polymerization. However, the purified complex alone is not sufficient to mediate the activity; a second component that binds Cdc42 directly and mediates the interaction between Cdc42 and the complex also is required. These results establish an important link between a signaling molecule, Cdc42, and a complex that can directly modulate actin networks in vitro. We propose that activation of the Arp2/3 complex by Cdc42 and other signaling molecules plays a central role in stimulating actin polymerization at the cell surface.     

Pre and Post-stroke Use of Statins Improves Stroke Outcome

Introduction:

Although there is sufficient evidence that HMG CoA Reductase Inhibitors reduce stroke recurrence in patients with or ischemic heart disease, it remains unclear whether they also improve outcomes given before or after stroke onset and whether such an effect is more robust with pre-stroke or post-stroke use of statins.

Materials and Methods:

We carried out a retrospective analysis of a large University Health Consortium Database. Patients with statin use before or after stroke onset were included in the analysis. Twenty patients discontinued statins after stroke onset. The outcome measures were discharge home or long-term care facility and/or death within 45 days.

Results:

Patients with prior statin use were more likely to be discharged home (1.67, CI 1.12-2.49), as were post stroke statin patients who had a more robust effect OR 2.63, CI 1.61-4.53).

Conclusions:

Patients started on statins after stroke were more likely to be discharged home versus patients already on statins before stroke onset. However, both groups were also more likely to be discharged home than those patients not on statins.     

The safety,efficacy, and cost-effectiveness of intraoperative cell salvage in metastatic spine tumor surgery

Background Context

Metastatic spine tumor surgery (MSTS) is associated with substantial blood loss, therefore leading to high morbidity and mortality. Although intraoperative cell salvage with leukocyte depletion filter (IOCS-LDF) has been studied as an effective means of reducing blood loss in other surgical settings, including the spine, no study has yet analyzed the efficacy of reinfusion of salvaged blood in reducing the need for allogenic blood transfusion in patients who have had surgery for MSTS.

Interval based fuzzy systems for identification of important genes from microarray gene expression data: Application to carcinogenic development

In the present article, we develop two interval based fuzzy systems for identification of some possible genes mediating the carcinogenic development in various tissues. The methodology involves dimensionality reduction, classifying the genes through incorporation of the notion of linguistic fuzzy sets low, medium and high, and finally selection of some possible genes mediating a particular disease, obtained by a rule generation/grouping technique. The effectiveness of the proposed methodology, is demonstrated using five microarray gene expression datasets dealing with human lung, colon, sarcoma, breast cancer and leukemia. Moreover, the superior capability of the methodology in selecting important genes, over five other existing gene selection methods, viz., Significance Analysis of Microarrays (SAM), Signal-to-Noise Ratio (SNR), Neighborhood analysis (NA), Bayesian Regularization (BR) and Data-adaptive (DA) is demonstrated, in terms of the enrichment of each GO category of the important genes based on P-values. The results are appropriately validated by earlier investigations, gene expression profiles and t-test. The proposed methodology has been able to select genes that are more biologically significant in mediating the development of a disease than those obtained by the others.     

Heavy and light cigarette smokers have similar dysfunction of endothelial vasoregulatory activity: an in vivo and in vitro correlation

OBJECTIVES: The goal of this study was to investigate the dose-dependent effects of active cigarette smoking on endothelial nitric oxide (NO) and endothelin-1 (ET-1) biosynthesis. BACKGROUND: Limited studies have suggested that active cigarette smoking may be associated with a dose-dependent reduction of endothelium-dependent vasodilation (EDV). The underlying biochemical changes that cause this dose-specific effect, such as changes in the endothelial NO biosynthetic pathway and ET-1 production, have not been examined. METHODS: Flow- and nitroglycerin-mediated reactivity of the brachial artery were measured in eight nonsmokers, seven light smokers (< or =1 pack/week) and eight heavy smokers (> or =1 pack/day), and their sera were added to confluent ( approximately 85%) monolayers of human umbilical endothelial cells (HUVECs) for 12 h. Basal and substance P-stimulated NO and basal ET-1 production were measured. The HUVECs used for measuring basal NO production were lysed, and both endothelial NO synthase (eNOS) protein expression and eNOS activity were determined. RESULTS: Serum cotinine level and pack-years of smoking were significantly lower in light smokers compared with heavy smokers (p < 0.006 and p < 0.004, respectively). There were no significant differences between heavy smokers and light smokers in EDV (p = 0.52), basal- (p = 0.70) and stimulated-NO production (p = 0.95), eNOS protein (p = 0.40) and eNOS activity (p = 0.63). Compared with nonsmokers, all the parameters were significantly altered in both of the smokers' groups. No differences were found in nitroglycerin-mediated vasodilation and in vitro ET-1 production among the three groups. CONCLUSIONS: These results indicate light smoking may have similar detrimental effects on EDV and NO biosynthetic pathway as does heavy smoking. These data may have important implications concerning the amount of active cigarette exposure that imparts cardiovascular risk.     

Anti-metastatic vaccination of tumor-bearing mice with il-2-gene-inserted tumor cells

IL-2 gene was introduced through retroviral vectors into the highly malignant and poorly immunogenic 3LL-D122 clone. Both high and low D122-11-2 secretors showed elimination of tumorigenicity in syngeneic immune-competent mice; however, in nude mice only the high IL-2 secretor showed reduced tumorigenicity as compared with parental D 122 cells. Also, following intravenous inoculation, only the high IL-2 secretor showed reduced generation of metastases, whereas the low IL-2 secretors were as highly metastatic as parental cells. These results seem to indicate that low levels of IL-2 secreted by tumor cells are sufficient to activate T cells, while higher levels are needed in order to activate non-T-cell effectors. D122-IL-2 secretors induced high levels of anti-tumor CTL, while their sensitivity to the lytic activity of these CTL was similar to the sensitivity of D122 cells, thus indicating that the elevation of immunogenicity of IL-2 secretors was essentially due to the secreted IL-2. In accordance with CTL induction, pre-immunization with IL-2 secretors protected mice against subsequent challenge of parental cells. Moreover, immunization in an “immunotherapy protocol” i.e., vaccination of mice carrying an established tumor of parental D122 cells with inactivated D122-IL-2 infectants, almost completely eliminated the generation of lung metastases by D122 cells, thus providing a rationale for the use of IL-2 gene transferred tumor cells as a modality for treatment of metastasis.