All-solid-state dye-sensitized solar cells with high efficiency

Dye-sensitized solar cells based on titanium dioxide (TiO(2)) are promising low-cost alternatives to conventional solid-state photovoltaic devices based on materials such as Si, CdTe and CuIn(1-x)Ga(x)Se(2) (refs 1, 2). Despite offering relatively high conversion efficiencies for solar energy, typical dye-sensitized solar cells suffer from durability problems that result from their use of organic liquid electrolytes containing the iodide/tri-iodide redox couple, which causes serious problems such as electrode corrosion and electrolyte leakage. Replacements for iodine-based liquid electrolytes have been extensively studied, but the efficiencies of the resulting devices remain low. Here we show that the solution-processable p-type direct bandgap semiconductor CsSnI(3) can be used for hole conduction in lieu of a liquid electrolyte. The resulting solid-state dye-sensitized solar cells consist of CsSnI(2.95)F(0.05) doped with SnF(2), nanoporous TiO(2) and the dye N719, and show conversion efficiencies of up to 10.2 per cent (8.51 per cent with a mask). With a bandgap of 1.3 electronvolts, CsSnI(3) enhances visible light absorption on the red side of the spectrum to outperform the typical dye-sensitized solar cells in this spectral region.     

Oligodendroglia metabolically support axons and contribute to neurodegeneration

Oligodendroglia support axon survival and function through mechanisms independent of myelination, and their dysfunction leads to axon degeneration in several diseases. The cause of this degeneration has not been determined, but lack of energy metabolites such as glucose or lactate has been proposed. Lactate is transported exclusively by monocarboxylate transporters, and changes to these transporters alter lactate production and use. Here we show that the most abundant lactate transporter in the central nervous system, monocarboxylate transporter 1 (MCT1, also known as SLC16A1), is highly enriched within oligodendroglia and that disruption of this transporter produces axon damage and neuron loss in animal and cell culture models. In addition, this same transporter is reduced in patients with, and in mouse models of, amyotrophic lateral sclerosis, suggesting a role for oligodendroglial MCT1 in pathogenesis. The role of oligodendroglia in axon function and neuron survival has been elusive; this study defines a new fundamental mechanism by which oligodendroglia support neurons and axons.     

Phosphorylation of WAVE1 regulates actin polymerization and dendritic spine morphology

WAVE1--the Wiskott-Aldrich syndrome protein (WASP)--family verprolin homologous protein 1--is a key regulator of actin-dependent morphological processes in mammals, through its ability to activate the actin-related protein (Arp2/3) complex. Here we show that WAVE1 is phosphorylated at multiple sites by cyclin-dependent kinase 5 (Cdk5) both in vitro and in intact mouse neurons. Phosphorylation of WAVE1 by Cdk5 inhibits its ability to regulate Arp2/3 complex-dependent actin polymerization. Loss of WAVE1 function in vivo or in cultured neurons results in a decrease in mature dendritic spines. Expression of a dephosphorylation-mimic mutant of WAVE1 reverses this loss of WAVE1 function in spine morphology, but expression of a phosphorylation-mimic mutant does not. Cyclic AMP (cAMP) signalling reduces phosphorylation of the Cdk5 sites in WAVE1, and increases spine density in a WAVE1-dependent manner. Our data suggest that phosphorylation/dephosphorylation of WAVE1 in neurons has an important role in the formation of the filamentous actin cytoskeleton, and thus in the regulation of dendritic spine morphology.     

Pluripotency of spermatogonial stem cells from adult mouse testis

Embryonic germ cells as well as germline stem cells from neonatal mouse testis are pluripotent and have differentiation potential similar to embryonic stem cells, suggesting that the germline lineage may retain the ability to generate pluripotent cells. However, until now there has been no evidence for the pluripotency and plasticity of adult spermatogonial stem cells (SSCs), which are responsible for maintaining spermatogenesis throughout life in the male. Here we show the isolation of SSCs from adult mouse testis using genetic selection, with a success rate of 27%. These isolated SSCs respond to culture conditions and acquire embryonic stem cell properties. We name these cells multipotent adult germline stem cells (maGSCs). They are able to spontaneously differentiate into derivatives of the three embryonic germ layers in vitro and generate teratomas in immunodeficient mice. When injected into an early blastocyst, SSCs contribute to the development of various organs and show germline transmission. Thus, the capacity to form multipotent cells persists in adult mouse testis. Establishment of human maGSCs from testicular biopsies may allow individual cell-based therapy without the ethical and immunological problems associated with human embryonic stem cells. Furthermore, these cells may provide new opportunities to study genetic diseases in various cell lineages.     

Human T-cell lymphotropic virus type-I antibodies in Falashas and other ethnic groups in Israel

Epidemiological studies of the human T-cell leukaemia/lymphoma virus type I (HTLV-I), a type-C retrovirus of the human T-lymphotropic virus family, have used serological surveys to identify population subgroups possessing a high prevalence of naturally occurring HTLV-I-specific antibodies. Studies carried out to delineate the global distribution of the virus have demonstrated natural antibodies to HTLV-I in the serum of healthy donors from specific geographical areas, and have defined viral endemic areas in Japan, the Caribbean basin, Africa and the southeastern United States. Such studies have suggested that the prevalence of HTLV-I antibodies is directly correlated with age, is associated with the clinical syndrome of adult T-cell lymphoma, and is associated with transmission from mother to child. A separate subtype of the human retrovirus, HTLV-II (refs 21, 22), has also been identified. The population of Israel in part comprises groups of immigrants of various ethnic and geographical origins. Because of this, and the fact that Israel has a highly developed public health system, we surmised that the ethnic groups in Israel could be used in a seroepidemiological survey of HTLV infection. The serological survey reported here demonstrates a high prevalence of HTLV-I antibodies in new immigrants from Ethiopia. This previously ethnically and geographically isolated group, the 'Black Jews' or 'Falashas', from the Gondar region in the northern rural highlands of Ethiopia, has the highest endemic rate of HTLV-I yet reported outside Japan.     

Activation at M-phase of a protein kinase encoded by a starfish homologue of the cell cycle control gene cdc2+

In both starfish and amphibian oocytes, the activity of a major protein kinase which is independent of Ca2+ and cyclic nucleotides increases dramatically at meiotic and mitotic nuclear divisions. The in vivo substrates of this kinase are unknown, but phosphorylation of H1 histone can be used as an in vitro assay. We have purified this kinase from starfish oocytes. The major band in the most highly purified preparation contained a polypeptide of relative molecular mass (Mr) 34,000 (34K). This is the same size as the protein kinase encoded by cdc2+, which regulates entry into mitosis in fission yeast and is a component of MPF purified from Xenopus. Here, we show that antibodies against p34 recognize the starfish 34K protein and propose that entry into meiotic and mitotic nuclear divisions involves activation of the protein kinase encoded by a homologue of cdc2+. Given the wide occurrence of cdc2+ homologues from budding yeast to Xenopus and human cells, this activation may act as a common mechanism controlling entry into mitosis in eukaryotic cells.