ENOBIO - First tests of a dry electrophysiology electrode using carbon nanotubes

We describe the development and first tests of Enobio, a dry electrode sensor concept for biopotential applications. In the proposed electrodes, the tip of the electrode is covered with a forest of multi-walled CNTs that can be coated with Ag/AgCl to provide ionic-electronic transduction. The CNT brush-like structure is to penetrate the outer layers of the skin improving electrical contact as well as increae the contact surface area. In this paper, we report the results of the first tests of this concept -- immersion on saline solution and pig skin signal detection. These indicate performance on a par with state of the art research-oriented wet electrodes.Comment: Submitted and accepted at the 28th IEEE EMBS International Conference, New York City, August 31st-September 3rd, 2006. Figures updated with proper filtering and averagin

Successive Cambia: A Developmental Oddity or an Adaptive Structure?

BackgroundSecondary growth by successive cambia is a rare phenomenon in woody plant species. Only few plant species, within different phylogenetic clades, have secondary growth by more than one vascular cambium. Often, these successive cambia are organised concentrically. In the mangrove genus Avicennia however, the successive cambia seem to have a more complex organisation. This study aimed (i) at understanding the development of successive cambia by giving a three-dimensional description of the hydraulic architecture of Avicennia and (ii) at unveiling the possible adaptive nature of growth by successive cambia through a study of the ecological distribution of plant species with concentric internal phloem.ResultsAvicennia had a complex network of non-cylindrical wood patches, the complexity of which increased with more stressful ecological conditions. As internal phloem has been suggested to play a role in water storage and embolism repair, the spatial organisation of Avicennia wood could provide advantages in the ecologically stressful conditions species of this mangrove genus are growing in. Furthermore, we could observe that 84.9% of the woody shrub and tree species with concentric internal phloem occurred in either dry or saline environments strengthening the hypothesis that successive cambia provide the necessary advantages for survival in harsh environmental conditions.ConclusionsSuccessive cambia are an ecologically important characteristic, which seems strongly related with water-limited environments

Nephrin Is Expressed on the Surface of Insulin Vesicles and Facilitates Glucose-Stimulated Insulin Release

Nephrin, an immunoglobulin-like protein essential for the function of the glomerular podocyte and regulated in diabetic nephropathy, is also expressed in pancreatic beta-cells, where its function remains unknown. The aim of this study was to investigate whether diabetes modulates nephrin expression in human pancreatic islets and to explore the role of nephrin in beta-cell function. Nephrin expression in human pancreas and in MIN6 insulinoma cells was studied by Western blot, PCR, confocal microscopy, subcellular fractionation, and immunogold labeling. Islets from diabetic (n = 5) and nondiabetic (n = 7) patients were compared. Stable transfection and siRNA knockdown in MIN-6 cells/human islets were used to study nephrin function in vitro and in vivo after transplantation in diabetic immunodeficient mice. Live imaging of green fluorescent protein (GFP)-nephrin-transfected cells was used to study nephrin endocytosis. Nephrin was found at the plasma membrane and on insulin vesicles. Nephrin expression was decreased in islets from diabetic patients when compared with nondiabetic control subjects. Nephrin transfection in MIN-6 cells/pseudoislets resulted in higher glucose-stimulated insulin release in vitro and in vivo after transplantation into immunodeficient diabetic mice. Nephrin gene silencing abolished stimulated insulin release. Confocal imaging of GFP-nephrin-transfected cells revealed nephrin endocytosis upon glucose stimulation. Actin stabilization prevented nephrin trafficking as well as nephrin-positive effect on insulin release. Our data suggest that nephrin is an active component of insulin vesicle machinery that may affect vesicle-actin interaction and mobilization to the plasma membrane. Development of drugs targeting nephrin may represent a novel approach to treat diabetes

Plasticity of Adult Human Pancreatic Duct Cells by Neurogenin3-Mediated Reprogramming

AIMS/HYPOTHESIS: Duct cells isolated from adult human pancreas can be reprogrammed to express islet beta cell genes by adenoviral transduction of the developmental transcription factor neurogenin3 (Ngn3). In this study we aimed to fully characterize the extent of this reprogramming and intended to improve it. METHODS: The extent of the Ngn3-mediated duct-to-endocrine cell reprogramming was measured employing genome wide mRNA profiling. By modulation of the Delta-Notch signaling or addition of pancreatic endocrine transcription factors Myt1, MafA and Pdx1 we intended to improve the reprogramming. RESULTS: Ngn3 stimulates duct cells to express a focused set of genes that are characteristic for islet endocrine cells and/or neural tissues. This neuro-endocrine shift however, is incomplete with less than 10% of full duct-to-endocrine reprogramming achieved. Transduction of exogenous Ngn3 activates endogenous Ngn3 suggesting auto-activation of this gene. Furthermore, pancreatic endocrine reprogramming of human duct cells can be moderately enhanced by inhibition of Delta-Notch signaling as well as by co-expressing the transcription factor Myt1, but not MafA and Pdx1. CONCLUSIONS/INTERPRETATION: The results provide further insight into the plasticity of adult human duct cells and suggest measurable routes to enhance Ngn3-mediated in vitro reprogramming protocols for regenerative beta cell therapy in diabetes

Proinsulin Atypical Maturation and Disposal Induces Extensive Defects in Mouse Ins2+/Akita β-Cells

Because of its low relative folding rate and plentiful manufacture in β-cells, proinsulin maintains a homeostatic balance of natively and plentiful non-natively folded states (i.e., proinsulin homeostasis, PIHO) through the integration of maturation and disposal processes. PIHO is susceptible to genetic and environmental influences, and its disorder has been critically linked to defects in β-cells in diabetes. To explore this hypothesis, we performed polymerase chain reaction (PCR), metabolic-labeling, immunoblotting, and histological studies to clarify what defects result from primary disorder of PIHO in model Ins2+/Akita β-cells. We used T antigen-transformed Ins2+/Akita and control Ins2+/+ β-cells established from Akita and wild-type littermate mice. In Ins2+/Akita β-cells, we found no apparent defect at the transcriptional and translational levels to contribute to reduced cellular content of insulin and its precursor and secreted insulin. Glucose response remained normal in proinsulin biosynthesis but was impaired for insulin secretion. The size and number of mature insulin granules were reduced, but the size/number of endoplasmic reticulum, Golgi, mitochondrion, and lysosome organelles and vacuoles were expanded/increased. Moreover, cell death increased, and severe oxidative stress, which manifested as increased reactive oxygen species, thioredoxin-interacting protein, and protein tyrosine nitration, occurred in Ins2+/Akita β-cells and/or islets. These data show the first clear evidence that primary PIHO imbalance induces severe oxidative stress and impairs glucose-stimulated insulin release and β-cell survival as well as producing other toxic consequences. The defects disclosed/clarified in model Ins2+/Akita β-cells further support a role of the genetic and stress-susceptible PIHO disorder in β-cell failure and diabetes

Genetic Evidence Highlights Potential Impacts of By-Catch to Cetaceans

Incidental entanglement in fishing gear is arguably the most serious threat to many populations of small cetaceans, judging by the alarming number of captured animals. However, other aspects of this threat, such as the potential capture of mother-offspring pairs or reproductive pairs, could be equally or even more significant but have rarely been evaluated. Using a combination of demographic and genetic data we provide evidence that i) Franciscana dolphin pairs that are potentially reproductive and mother-offspring pairs form temporal bonds, and ii) are entangled simultaneously. Our results highlight potential demographic and genetic impacts of by-catch to cetacean populations: the joint entanglement of mother-offspring or reproductive pairs, compared to random individuals, might exacerbate the demographic consequences of by-catch, and the loss of groups of relatives means that significant components of genetic diversity could be lost together. Given the social nature of many odontocetes (toothed cetaceans), we suggest that these potential impacts could be rather general to the group and therefore by-catch could be more detrimental than previously considered

Female-Biased Dispersal and Gene Flow in a Behaviorally Monogamous Mammal, the Large Treeshrew (Tupaia tana)

Background: Female-biased dispersal (FBD) is predicted to occur in monogamous species due to local resource competition among females, but evidence for this association in mammals is scarce. The predicted relationship between FBD and monogamy may also be too simplistic, given that many pair-living mammals exhibit substantial extra-pair paternity. Methodology/Principal Findings: I examined whether dispersal and gene flow are female-biased in the large treeshrew (Tupaia tana) in Borneo, a behaviorally monogamous species with a genetic mating system characterized by high rates (50%) of extra-pair paternity. Genetic analyses provided evidence of FBD in this species. As predicted for FBD, I found lower mean values for the corrected assignment index for adult females than for males using seven microsatellite loci, indicating that female individuals were more likely to be immigrants. Adult female pairs were also less related than adult male pairs. Furthermore, comparison of Bayesian coalescent-based estimates of migration rates using maternally and bi-parentally inherited genetic markers suggested that gene flow is female-biased in T. tana. The effective number of migrants between populations estimated from mitochondrial DNA sequence was three times higher than the number estimated using autosomal microsatellites. Conclusions/Significance: These results provide the first evidence of FBD in a behaviorally monogamous species without mating fidelity. I argue that competition among females for feeding territories creates a sexual asymmetry in the costs an

Antioxidant effects of insulin-like growth factor-I (IGF-I) in rats with advanced liver cirrhosis

BACKGROUND: The exogenous administration of Insulin-like Growth Factor-I (IGF-I) induces hepatoprotective and antifibrogenic actions in experimental liver cirrhosis. To better understand the possible pathways behind the beneficial effect of IGF-I, the aim of this work was to investigate severe parameters involved in oxidative damage in hepatic tissue from cirrhotic animals treated with IGF-I (2 μg. 100 g(-1). day(-1)). Iron and copper play an important role in oxidative mechanisms, producing the deleterious hydroxyl radical (*OH) that peroxides lipid membranes and damages DNA. Myeloperoxidase (MPO) and nitric oxide (NO) are known sources of free radicals and induce reduction of ferritin-Fe(3+ )into free Fe(2+), contributing to oxidative damage. METHODS: Liver cirrhosis was induced by CCl(4 )inhalation in Wistar male rats for 30 weeks. Healthy controls were studied in parallel (n = 10). Fe and Cu were assessed by atomic absoption spectrometry and iron content was also evaluated by Perls' staining. MPO was measured by ELISA and transferrin and ferritin by immunoturbidimetry. iNOS expression was studied by immuno-histochemistry. RESULTS: Liver cirrhosis was histologically proven and ascites was observed in all cirrhotic rats. Compared to controls untreated cirrhotic rats showed increased hepatic levels of iron, ferritin, transferrin (p < 0.01), copper, MPO and iNOS expression (p < 0.01). However, IGF-treatment induced a significant reduction of all these parameters (p < 0.05). CONCLUSION: the hepatoprotective and antifibrogenic effects of IGF-I in cirrhosis are associated with a diminution of the hepatic contents of several factors all of them involved in oxidative damage