Vitamin d and stroke: promise for prevention and better outcome.

The role of vitamin D (VitD) has recently been expanded beyond bone homeostasis and regulation of calcium levels. VitD deficiency has been proposed as a new risk factor for cardiovascular disease, including stroke. Low 25(OH)VitD levels are very common among post-stroke patients, probably due to their limited mobility and decreased sunlight exposure along with a higher prevalence of malnutrition, and they have been associated with previous and incident cerebrovascular events. Contributing mechanisms have been linked to the association of VitD deficiency with the presence of hypertension, diabetes mellitus and atherosclerosis. Moreover, there is experimental evidence demonstrating that VitD exerts neuroprotective effects, such as stimulation of neurotrophic factors, quenching of oxidative hyperactivity and regulation of neuronal death, as well as antithrombotic properties. It is plausible that VitD supplementation could be a beneficial intervention for the prevention and/or treatment of cerebrovascular disease possibly by decreasing the aforementioned cerebrovascular risk factors and simultaneously by improving neurologic and cognitive functions, thereby reducing falls and fractures in post-stroke patients. However, study results are still conflicting and data from large, randomized clinical trials are needed to clarify these speculations.

rKv1.2 overexpression in the central medial thalamic area decreases caffeine-induced arousal.

The voltage-gated potassium channel Kv1.2 belongs to the shaker-related family and has recently been implicated in the control of sleep profile on the basis of clinical and experimental evidence in rodents. To further investigate whether increasing Kv1.2 activity would promote sleep occurrence in rats, we developed an adeno-associated viral vector that induces overexpression of rat Kv1.2 protein. The viral vector was first evaluated in vitro for its ability to overexpress rat Kv1.2 protein and to produce functional currents in infected U2OS cells. Next, the adeno-associated Kv1.2 vector was injected stereotaxically into the central medial thalamic area of rats and overexpression of Kv1.2 was showed by in situ hybridization, ex vivo electrophysiology and immunohistochemistry. Finally, the functional effect of Kv1.2 overexpression on sleep facilitation was investigated using telemetry system under normal conditions and following administration of the arousing agent caffeine, during the light phase. While no differences in sleep profile were observed between the control and the treated animals under normal conditions, a decrease in the pro-arousal effect of caffeine was seen only in the animals injected with the adeno-associated virus-Kv1.2 vector. Overall, our data further support a role of the Kv1.2 channel in the control of sleep profile, particularly under conditions of sleep disturbance.

Role of glutamate in neuron-glia metabolic coupling.

The coupling between synaptic activity and glucose utilization (neurometabolic coupling) is a central physiologic principle of brain function that has provided the basis for 2-deoxyglucose-based functional imaging with positron emission tomography. Approximately 10 y ago we provided experimental evidence that indicated a central role of glutamate signaling on astrocytes in neurometabolic coupling. The basic mechanism in neurometabolic coupling is the glutamate-stimulated aerobic glycolysis in astrocytes, such that the sodium-coupled reuptake of glutamate by astrocytes and the ensuing activation of the Na(+)-K(+) ATPase triggers glucose uptake and its glycolytic processing, which results in the release of lactate from astrocytes. Lactate can then contribute to the activity-dependent fueling of the neuronal energy demands associated with synaptic transmission. Analyses of this coupling have been extended in vivo and have defined the methods of coupling for inhibitory neurotransmission as well as its spatial extent in relation to the propagation of metabolic signals within the astrocytic syncytium. On the basis of a large body of experimental evidence, we proposed an operational model, "the astrocyte-neuron lactate shuttle." A series of results obtained by independent laboratories have provided further support for this model. This body of evidence provides a molecular and cellular basis for interpreting data that are obtained with functional brain imaging studies.

Molecular hydrogen diffusion in nanostructured amorphous silicon thin films

We study hydrogen stability and its evolution during thermal annealing in nanostructured amorphous silicon thin films. From the simultaneous measurement of heat and hydrogen desorption, we obtain the experimental evidence of molecular diffusion in these materials. In addition, we introduce a simple diffusion model which shows good agreement with the experimental data

Magnetism of isolated Mn12 single-molecule magnets detected by magnetic circular dichroism: Observation of spin tunneling with a magneto-optical technique

We report magnetic and magneto-optical measurements of two Mn12 single-molecule magnet derivatives isolated in organic glasses. Field-dependent magnetic circular dichroism (MCD) intensity curves (hysteresis cycles) are found to be essentially identical to superconducting quantum interference device magnetization results and provide experimental evidence for the potential of the optical technique for magnetic characterization. Optical observation of magnetic tunneling has been achieved by studying the decay of the MCD signal at weak applied magnetic field

The unsolved puzzle of neuropathogenesis in glutaric aciduria type I.

Glutaric aciduria type I (GA-I) is a cerebral organic aciduria caused by deficiency of glutaryl-Co-A dehydrogenase (GCDH). GCDH deficiency leads to accumulation of glutaric acid (GA) and 3-hydroxyglutaric acid (3-OHGA), two metabolites that are believed to be neurotoxic, in brain and body fluids. The disorder usually becomes clinically manifest during a catabolic state (e.g. intercurrent illness) with an acute encephalopathic crisis that results in striatal necrosis and in a permanent dystonic-dyskinetic movement disorder. The results of numerous in vitro and in vivo studies have pointed to three main mechanisms involved in the metabolite-mediated neuronal damage: excitotoxicity, impairment of energy metabolism and oxidative stress. There is evidence that during a metabolic crisis GA and its metabolites are produced endogenously in the CNS and accumulate because of limiting transport mechanisms across the blood-brain barrier. Despite extensive experimental work, the relative contribution of the proposed pathogenic mechanisms remains unclear and specific therapeutic approaches have yet to be developed. Here, we review the experimental evidence and try to delineate possible pathogenetic models and approaches for future studies.

Complete nucleotide sequence of Birmingham IncP alpha plasmids. Compilation and comparative analysis.

The IncP alpha promiscuous plasmid (R18, R68, RK2, RP1 and RP4) comprises 60,099 bp of nucleotide sequence, encoding at least 74 genes. About 40 kb of the genome, designated the IncP core and including all essential replication and transfer functions, can be aligned with equivalent sequences in the IncP beta plasmid R751. The compiled IncP alpha sequence revealed several previously unidentified reading frames that are potential genes. IncP alpha plasmids carry genetic information very efficiently: the coding sequences of the genes are closely packed but rarely overlap, and occupy almost 86% of the genome's nucleotide sequence. All of the 74 genes should be expressed, although there is as yet experimental evidence for expression of only 60 of them. Six examples of tandem-in-frame initiation sites specifying two gene products each are known. Two overlapping gene arrangements occupy different reading frames of the same region. Intergenic regions include most of the 25 promoters; transcripts are usually polycistronic. Translation of most of the open reading frames seems to be initiated independently, each from its own ribosomal binding and initiation site, although, a few cases of coupled translation have been reported. The most frequently used initiation codon is AUG but translation for a few open reading frames begins at GUG or UUG. The most common stop-codon is UGA followed by UAA and then UAG. Regulatory circuits are complex and largely dependent on two components of the central control operon. KorA and KorB are transcriptional repressors controlling at least seven operons. KorA and KorB act synergistically in several cases by recognizing and binding to conserved nucleotide sequences. Twelve KorB binding sites were found around the IncP alpha sequence and these are conserved in R751 (IncP beta) with respect to both sequence and location. Replication of IncP alpha plasmids requires oriV and the plasmid-encoded initiator protein TrfA in combination with the host-encoded replication machinery. Conjugative plasmid transfer depends on two separate regions occupying about half of the genome. The primary segregational stability system designated Par/Mrs consists of a putative site-specific recombinase, a possible partitioning apparatus and a post-segregational lethality mechanism, all encoded in two divergent operons. Proteins related to the products of F sop and P1 par partitioning genes are separately encoded in the central control operon.

A non-linear VAD for noisy environments

This paper deals with non-linear transformations for improving the performance of an entropy-based voice activity detector (VAD). The idea to use a non-linear transformation has already been applied in the field of speech linear prediction, or linear predictive coding (LPC), based on source separation techniques, where a score function is added to classical equations in order to take into account the true distribution of the signal. We explore the possibility of estimating the entropy of frames after calculating its score function, instead of using original frames. We observe that if the signal is clean, the estimated entropy is essentially the same; if the signal is noisy, however, the frames transformed using the score function may give entropy that is different in voiced frames as compared to nonvoiced ones. Experimental evidence is given to show that this fact enables voice activity detection under high noise, where the simple entropy method fails.

Magnetism of isolated Mn12 single-molecule magnets detected by magnetic circular dichroism: Observation of spin tunneling with a magneto-optical technique

We report magnetic and magneto-optical measurements of two Mn12 single-molecule magnet derivatives isolated in organic glasses. Field-dependent magnetic circular dichroism (MCD) intensity curves (hysteresis cycles) are found to be essentially identical to superconducting quantum interference device magnetization results and provide experimental evidence for the potential of the optical technique for magnetic characterization. Optical observation of magnetic tunneling has been achieved by studying the decay of the MCD signal at weak applied magnetic field

Biosynthesis of panaxynol and panaxydol in Panax ginseng

The natural formation of the bioactive C17-polyacetylenes (−)-(R)-panaxynol and panaxydol was analyzed by 13C-labeling experiments. For this purpose, plants of Panax ginseng were supplied with 13CO2 under field conditions or, alternatively, sterile root cultures of P. ginseng were supplemented with [U-13C6]glucose. The polyynes were isolated from the labeled roots or hairy root cultures, respectively, and analyzed by quantitative NMR spectroscopy. The same mixtures of eight doubly 13C-labeled isotopologues and one single labeled isotopologue were observed in the C17-polyacetylenes obtained from the two experiments. The polyketide-type labeling pattern is in line with the biosynthetic origin of the compounds via decarboxylation of fatty acids, probably of crepenynic acid. The 13C-study now provides experimental evidence for the biosynthesis of panaxynol and related polyacetylenes in P. ginseng under in planta conditions as well as in root cultures. The data also show that 13CO2 experiments under field conditions are useful to elucidate the biosynthetic pathways of metabolites, including those from roots.

A matter of time: delayed mate encounter postpones mating window initiation and reduces the strength of female choosiness

Reproductive success is determined by the presence and timing of encounter of mates. The latter depends on species-specific reproductive characteristics (e.g. initiation/duration of the mating window), season, and reproductive strategies (e.g. intensity of choosiness) that may potentially mitigate constraints imposed by mating windows. Despite their potentially crucial role for fitness and population dynamics, limited evidence exists about mating window initiation, duration and reproductive strategies. Here, we experimentally tested the mechanisms of initiation and the duration of the common lizard's Zootoca vivipara mating window, by manipulating the timing of mate encounter and analyzing its effect on (re-)mating probability. We furthermore tested treatment effects on female reproductive strategies, by measuring female choosiness. The timing of mate encounter and season did not significantly affect mating probability. However, a longer delay until mate encounter reduced female choosiness. Re-mating probability decreased with re-mating delay and was independent of mating delay. This indicates that mating window initiation depends on mate encounter, that its duration is fixed, and that plastic reproductive strategies exist. These findings contrast with previous beliefs and shows that mating windows per se may not necessarily constrain reproductive success, which is congruent with rapid range expansion and absence of positive density-effects on reproductive success (Allee effects). In summary, our results show that predicting the effect of mating windows on reproduction is complex and that experimental evidence is essential for evaluating their effect on reproduction and reproductive strategies, both being important determinants of population dynamics and the colonization of new habitats.

Connexins: key mediators of endocrine function.

The appearance of multicellular organisms imposed the development of several mechanisms for cell-to-cell communication, whereby different types of cells coordinate their function. Some of these mechanisms depend on the intercellular diffusion of signal molecules in the extracellular spaces, whereas others require cell-to-cell contact. Among the latter mechanisms, those provided by the proteins of the connexin family are widespread in most tissues. Connexin signaling is achieved via direct exchanges of cytosolic molecules between adjacent cells at gap junctions, for cell-to-cell coupling, and possibly also involves the formation of membrane "hemi-channels," for the extracellular release of cytosolic signals, direct interactions between connexins and other cell proteins, and coordinated influence on the expression of multiple genes. Connexin signaling appears to be an obligatory attribute of all multicellular exocrine and endocrine glands. Specifically, the experimental evidence we review here points to a direct participation of the Cx36 isoform in the function of the insulin-producing β-cells of the endocrine pancreas, and of the Cx40 isoform in the function of the renin-producing juxtaglomerular epithelioid cells of the kidney cortex.

The fetal hypothalamus has the potential to generate cells with a gonadotropin releasing hormone (GnRH) phenotype.

BACKGROUND: Neurospheres (NS) are colonies of neural stem and precursor cells capable of differentiating into the central nervous system (CNS) cell lineages upon appropriate culture conditions: neurons, and glial cells. NS were originally derived from the embryonic and adult mouse striatum subventricular zone. More recently, experimental evidence substantiated the isolation of NS from almost any region of the CNS, including the hypothalamus. METHODOLOGY/FINDINGS: Here we report a protocol that enables to generate large quantities of NS from both fetal and adult rat hypothalami. We found that either FGF-2 or EGF were capable of inducing NS formation from fetal hypothalamic cultures, but that only FGF-2 is effective in the adult cultures. The hypothalamic-derived NS are capable of differentiating into neurons and glial cells and most notably, as demonstrated by immunocytochemical detection with a specific anti-GnRH antibody, the fetal cultures contain cells that exhibit a GnRH phenotype upon differentiation. CONCLUSIONS/SIGNIFICANCE: This in vitro model should be useful to study the molecular mechanisms involved in GnRH neuronal differentiation.

Wood ants use resin to protect themselves against pathogens

Social life is generally associated with an increased exposure to pathogens and parasites, due to factors such as high population density, frequent physical contact and the use of perennial nest sites. However, sociality also permits the evolution of new collective behavioural defences. Wood ants, Formica paralugubris, commonly bring back pieces of solidified coniferous resin to their nest. Many birds and a few mammals also incorporate green plant material into their nests. Collecting plant material rich in volatile compounds might be an efficient way to fight bacteria and fungi. However, no study has demonstrated that this behaviour has a positive effect on survival. Here, we provide the first experimental evidence that animals using plant compounds with antibacterial and antifungal properties survive better when exposed to detrimental micro-organisms. The presence of resin strongly improves the survival of F. paralugubris adults and larvae exposed to the bacteria Pseudomonas fluorescens, and the survival of larvae exposed to the entomopathogenic fungus Metarhizium anisopliae. These results show that wood ants capitalize on the chemical defences which have evolved in plants to collectively protect themselves against pathogens.

Developmental critical period in genetic redox dysregulation: animal and human studies in schizophrenia

Converging evidence favors an abnormal susceptibility to oxidative stress in schizophrenia. Decreased levels of glutathione (GSH), the major cellular antioxidant and redox regulator, was observed in cerebrospinal-fluid and prefrontal cortex of patients. Importantly, abnormal GSH synthesis of genetic origin was observed: Two case-control studies showed an association with a GAG trinucleotide repeat (TNR) polymorphism in the GSH key synthesizing enzyme glutamate-cysteine-ligase (GCL) catalytic subunit (GCLC) gene. The most common TNR genotype 7/7 was more frequent in controls, whereas the rarest TNR genotype 8/8 was three times more frequent in patients. The disease associated genotypes (35% of patients) correlated with decreased GCLC protein, GCL activity and GSH content. Similar GSH system anomalies were observed in early psychosis patients. Such redox dysregulation combined with environmental stressors at specific developmental stages could underlie structural and functional connectivity anomalies. In pharmacological and knock-out (KO) models, GSH deficit induces anomalies analogous to those reported in patients. (a) morphology: spine density and GABA-parvalbumine immunoreactivity (PV-I) were decreased in anterior cingulate cortex. KO mice showed delayed cortical PV-I at PD10. This effect is exacerbated in mice with increased DA from PD5-10. KO mice exhibit cortical impairment in myelin and perineuronal net known to modulate PV connectivity. (b) physiology: In cultured neurons, NMDA response are depressed by D2 activation. In hippocampus, NMDA-dependent synaptic plasticity is impaired and kainate induced g-oscillations are reduced in parallel to PV-I. (c) cognition: low GSH models show increased sensitivity to stress, hyperactivity, abnormal object recognition, olfactory integration and social behavior. In a clinical study, GSH precursor N-acetyl cysteine (NAC) as add on therapy, improves the negative symptoms and decreases the side effects of antipsychotics. In an auditory oddball paradigm, NAC improves the mismatched negativity, an evoked potential related to pre-attention and to NMDA receptors function. In summary, clinical and experimental evidence converge to demonstrate that a genetically induced dysregulation of GSH synthesis combined with environmental insults in early development represent a major risk factor contributing to the development of schizophrenia