Membrane permeability changes duringRana oocyte maturation

A transition from an open system to a closed one must occur during the complex process of meiotic maturation of the amphibian oocyte. Membrane permeability to urea inRana oocytes following progesterone stimulation was determined, and the largest decrease was found to coincide with germinal vesicle breakdown. These findings suggest that the timing of the disappearance of membrane permeability correlates with developmental events that prepare the oocyte for a hostile environment.     

Development and field testing of a multi-antenna GPS system for deformation monitoring

GPS has become an important technology for monitoring deformations of structures and the crust of the Earth. A limiting factor for large-scale use of GPS in such applications is however its high hardware cost. For automatic monitoring of deformations, each point to be monitored needs equipped with a set of GPS instruments. This makes many applications such as routine monitoring of landslides too expensive in most cases. A multi-antenna GPS system has been developed and tested aiming at significantly reducing the cost of GPS when used for monitoring deformations of objects such as slopes. The system uses special hardware and software to allow one GPS receiver to be used with a number of GPS antennas. One set of such equipment can therefore be used to monitor a number of points. The system normally reduces the cost of GPS hardware by a number of folds. Besides, such a system design also eases the tasks of data communication, management and system control. This paper describes the design and system configurations of the multi-antenna GPS system that has been developed by the research team. The system consists of integrated hardware and software components for data acquisition, transmission, processing, analysis and visualization. Integration of the GPS system with conventional slope monitoring systems will also be discussed in brief.     

Hedgehog signaling in pancreas development and disease

Since its discovery, numerous studies have shown that the Hedgehog (Hh) signaling pathway plays an instrumental role during diverse processes of cell differentiation and organ development. More recently, it has become evident that Hh signaling is not restricted to developmental events, but retains some of its activity during adult life. In mature tissues, Hh signaling has been implicated in the maintenance of stem cell niches in the brain, renewal of the gut epithelium and differentiation of hematopoietic cells. In addition to the basal function in adult tissue, deregulated signaling has been implicated in a variety of cancers, including basal cell carcinoma, glioma and small cell lung cancer. Here, we will focus on the role of Hh signaling in pancreas development and pancreatic diseases, including diabetes mellitus, chronic pancreatitis and pancreatic cancer. Received 5 August 2005; received after revision 4 November 2005; accepted 22 November 2005     

SCF(FBW7) regulates cellular apoptosis by targeting MCL1 for ubiquitylation and destruction

The effective use of targeted therapy is highly dependent on the identification of responder patient populations. Loss of FBW7, which encodes a tumour-suppressor protein, is frequently found in various types of human cancer, including breast cancer, colon cancer and T-cell acute lymphoblastic leukaemia (T-ALL). In line with these genomic data, engineered deletion of Fbw7 in mouse T cells results in T-ALL, validating FBW7 as a T-ALL tumour suppressor. Determining the precise molecular mechanisms by which FBW7 exerts antitumour activity is an area of intensive investigation. These mechanisms are thought to relate in part to FBW7-mediated destruction of key proteins relevant to cancer, including Jun, Myc, cyclin E and notch 1 (ref. 9), all of which have oncoprotein activity and are overexpressed in various human cancers, including leukaemia. In addition to accelerating cell growth, overexpression of Jun, Myc or notch 1 can also induce programmed cell death. Thus, considerable uncertainty surrounds how FBW7-deficient cells evade cell death in the setting of upregulated Jun, Myc and/or notch 1. Here we show that the E3 ubiquitin ligase SCF(FBW7) (a SKP1-cullin-1-F-box complex that contains FBW7 as the F-box protein) governs cellular apoptosis by targeting MCL1, a pro-survival BCL2 family member, for ubiquitylation and destruction in a manner that depends on phosphorylation by glycogen synthase kinase 3. Human T-ALL cell lines showed a close relationship between FBW7 loss and MCL1 overexpression. Correspondingly, T-ALL cell lines with defective FBW7 are particularly sensitive to the multi-kinase inhibitor sorafenib but resistant to the BCL2 antagonist ABT-737. On the genetic level, FBW7 reconstitution or MCL1 depletion restores sensitivity to ABT-737, establishing MCL1 as a therapeutically relevant bypass survival mechanism that enables FBW7-deficient cells to evade apoptosis. Therefore, our work provides insight into the molecular mechanism of direct tumour suppression by FBW7 and has implications for the targeted treatment of patients with FBW7-deficient T-ALL.     

The ectodomain of Toll-like receptor 9 is cleaved to generate a functional receptor

Mammalian Toll-like receptors (TLRs) 3, 7, 8 and 9 initiate immune responses to infection by recognizing microbial nucleic acids; however, these responses come at the cost of potential autoimmunity owing to inappropriate recognition of self nucleic acids. The localization of TLR9 and TLR7 to intracellular compartments seems to have a role in facilitating responses to viral nucleic acids while maintaining tolerance to self nucleic acids, yet the cell biology regulating the transport and localization of these receptors remains poorly understood. Here we define the route by which TLR9 and TLR7 exit the endoplasmic reticulum and travel to endolysosomes in mouse macrophages and dendritic cells. The ectodomains of TLR9 and TLR7 are cleaved in the endolysosome, such that no full-length protein is detectable in the compartment where ligand is recognized. Notably, although both the full-length and cleaved forms of TLR9 are capable of binding ligand, only the processed form recruits MyD88 on activation, indicating that this truncated receptor, rather than the full-length form, is functional. Furthermore, conditions that prevent receptor proteolysis, including forced TLR9 surface localization, render the receptor non-functional. We propose that ectodomain cleavage represents a strategy to restrict receptor activation to endolysosomal compartments and prevent TLRs from responding to self nucleic acids.     

Cytokine signaling convergence regulates the microglial state transition in Alzheimer’s disease

Cellular and Molecular Life Sciences - Genetic analyses have revealed the pivotal contribution of microglial dysfunctions to the pathogenesis of Alzheimer’s disease (AD). Along AD...     

In vitro modulation of rat adipocyte ghost membrane fluidity by cholesterol oxysterols

The effects of cholesterol and cholesterol-derived oxysterols (cholestanone, cholestenone, coprostanone and epicoprostanol) on adipocyte ghost membrane fluidity were studied using a fluorescence depolarization method. The fluorescence anisotropy of the treated membranes was determined using 1,6-diphenyl-1,3,5-hexatriene (DPH) and 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene (TMA-DPH). Cholestanone and cholesterol decreased membranes fluidity at both the concentrations tested (10 & 50 M) while the rest of the sterols did not exert any significant effect on membrane fluidity. In the presence of epinephrine, cholestanone partitioned more towards the lipid core but cholesterol partitioning was not affected. The fusion activation energies (E) obtained for membranes preincubated with cholestanone (8.6 kcal/mol) and cholesterol (8.2 kcal/mol) were not significantly different from that of untreated membranes (8.3 kcal/mol). Membranes preincubated with cholestanone and cholesterol did not exhibit any change in lipid phase throughout the temperature range (10–45°C) tested. The sterols were found to inhibit fisetin-induced phospholipid methylation in isolated rat adipocytes in the rank order of cholesterol > epicoprostanol > cholestanone=cholestenone=coprostanone, while basal methylations was unaffected. When adipocytes were preincubated with the sterols before the addition of fisetin, cholestanone and cholestenone showed 74% and 66% inhibition of maximal methylation respectively. These results indicated that cholesterol oxysterols interact differently with rat adipocyte membranes, with cholestanone interacting more with phospholipids located at the inner lipid bilayer (e.g. phosphatidylethanolamine) while cholesterol interacts more with phosphatidylcholine located at the outer lipid bilayer. This differential interaction may cause selective changes in membrane fluidity at different depths of the bilayer and thus may modulate the activities of membrane-bound proteins such as enzymes and receptors.     

Comparison of methods for determining orthotropic axes in 3D femur remodeling

The density distribution and internal structure of trabecular bone are modulated by local mechanical environment. In this study, an orthotropic adaptation algorithm was applied to the 3D femur model to simulate the variations of stiffness and orientation of trabecular bone under multi-loading conditions. This algorithm includes the determination of orthotropic axes and the stiffness modification of trabecular bone. Three methods were used to determine the orthotropic axes, i.e. the maximal cycle method, the stress maximum method, and the composite method. We found that the composite method was better than the other two. Firstly, the characteristics of density distribution obtained by using the composite method agreed better with those in real proximal femur. Secondly, the material orientation aligned with the known trabeculaer pattern. Finally, the ratios of the longitudinal modulus to the transverse modulus were also shown to be realistic in three local regions of the proximal femur.     

Prediction of central nervous system embryonal tumour outcome based on gene expression.

Embryonal tumours of the central nervous system (CNS) represent a heterogeneous group of tumours about which little is known biologically, and whose diagnosis, on the basis of morphologic appearance alone, is controversial. Medulloblastomas, for example, are the most common malignant brain tumour of childhood, but their pathogenesis is unknown, their relationship to other embryonal CNS tumours is debated, and patients' response to therapy is difficult to predict. We approached these problems by developing a classification system based on DNA microarray gene expression data derived from 99 patient samples. Here we demonstrate that medulloblastomas are molecularly distinct from other brain tumours including primitive neuroectodermal tumours (PNETs), atypical teratoid/rhabdoid tumours (AT/RTs) and malignant gliomas. Previously unrecognized evidence supporting the derivation of medulloblastomas from cerebellar granule cells through activation of the Sonic Hedgehog (SHH) pathway was also revealed. We show further that the clinical outcome of children with medulloblastomas is highly predictable on the basis of the gene expression profiles of their tumours at diagnosis.