ben Functions with scamp during synaptic transmission and long-term memory formation in Drosophila.

Genetic screens for Drosophila mutants defective in pavlovian olfactory memory have provided unique insight into the molecular basis of memory storage. Occasionally, these singular genetic lesions have been assembled into meaningful molecular pathways and neural circuitries. For the most part, however, these genes and their expression patterns in the CNS remain fragmented, demanding new clues from continued mutant screens. From a behavioral screen for long-term memory (LTM) mutants, we have identified ben (CG32594), which encodes a novel protein. Mutations of ben specifically disrupt LTM, leaving earlier memory phases intact. The role of ben appears physiological rather than developmental, because acutely induced expression of a ben(+) transgene in adults rescues the mutant's LTM defect. More interestingly, induced expression of ben(+) specifically in mushroom bodies (MBs), but not in the ellipsoid body of the central complex, is sufficient to rescue the mutant LTM defect. This suggests a role for ben in the MB during olfactory memory formation. We also provide evidence that BEN interacts genetically in both synaptic transmission and LTM formation with SCAMP, a synaptic protein known to be involved in vesicle recycling.

Dye-Doped Electrically Smart Windows Based on Polymer-Stabilized Liquid Crystal.

Here we report the fabrication of dye-doped polymer-stabilized liquid crystals (PSLC)-based smart windows. The effect of dye doping on PSLC contrast was investigated. Non-dichroic dye tints the PSLC sample in both off- and on-state, which is not beneficial for increasing its off/on contrast. The sample doped with dichroic dye shows a slight color in the off-state and strong color in the on-state, resulting in an enhanced contrast, which attributed to orientation dependent absorption of dichroic dyes. Furthermore, we blended non-dichroic dye and dichroic dye who have complementary absorption together into PSLC mixture. The sample is almost colorless in the off-state due to the subtractive process, while colored in the on-state. The contrast is further enhanced. The results show that the proposed multi-dye-doped PSLC device has high visual contrast and fast response time, making it attractive for applications in light management and architectural aesthetics.

Receptor-like tyrosine phosphatase PTP10D is required for long-term memory in Drosophila.

Tyrosine phosphorylation mediates multiple signal transduction pathways that play key roles in developmental processes and behavioral plasticity. The level of tyrosine phosphorylation is regulated by protein tyrosine kinases and protein tyrosine phosphatases (PTPs). Extensive studies have investigated the roles of tyrosine kinases in memory formation. However, there were few studies on PTPs. To date, learning has been shown to be defective only for mouse knock-outs of PTPalpha, leukocyte common antigen-related, or PTPdelta. A major limitation of these studies arises from their inability to distinguish an acute (biochemical) impairment of memory formation from a more chronic abnormality in neurodevelopment. From a behavioral screen for defective long-term memory, we found chi mutants to disrupt expression of the PTP10D protein tyrosine phosphatase gene. We show that chi mutants are normal for learning, early memory, and anesthesia-resistant memory, whereas long-term memory specifically is abolished. Significantly, induction of a heat shock-PTP10D+ transgene before training fully rescues the memory defect of chi mutants, thereby demonstrating an acute role for PTP10D in behavioral plasticity. We show that PTP10D is widely expressed in the embryonic CNS and in the adult brain. Transgenic expression of upstream activating sequence-PTP10D+ in mushroom bodies is sufficient to rescue the memory defect of chi mutants. Our data clearly demonstrate that signaling through PTP10D in mushroom bodies is critical for the formation of long-term memory.

A role for presenilin in post-stress regulation: effects of presenilin mutations on Ca2+ currents in Drosophila.

It has been shown that presenilin is involved in maintaining Ca2+ homeostasis in neurons, including regulating endoplasmic reticulum (ER) Ca2+ storage. From studies of primary cultures and cell lines, however, its role in stress-induced responses is still controversial. In the present study we analyzed the effects of presenilin mutations on membrane currents and synaptic functions in response to stress using an in vivo preparation. We examined voltage-gated K+ and Ca2+ currents at the Drosophila larval neuromuscular junction (NMJ) with voltage-clamp recordings. Our data showed that both currents were generally unaffected by loss-of-function or Alzheimer's disease (AD) -associated presenilin mutations under normal or stress conditions induced by heat shock (HS) or ER stress. In larvae expressing the mutant presenilins, prolonged Ca2+ tail current, reflecting slower deactivation kinetics of Ca2+ channels, was observed 1 day after stress treatments were terminated. It was further demonstrated that the L-type Ca2+ channel was specifically affected under these conditions. Moreover, synaptic plasticity at the NMJ was reduced in larvae expressing the mutant presenilins. At the behavioral level, memory in adult flies was impaired in the presenilin mutants 1 day after HS. The results show that presenilin function is important during the poststress period and its impairment contributes to memory dysfunction observed during adaptation to normal conditions after stress. Our findings suggest a new stress-related mechanism by which presenilin may be implicated in the neuropathology of AD.

Frequency modulation of synchronized Ca(2+) spikes in cultured hippocampal networks through mTOR.

The atypical serine/threonine protein kinase, a mammalian target of rapamycin (mTOR), is believed to be essential to the regulation of cell growth and the functions of the central nervous system. By using calcium imaging and patch-clamping techniques to study the role of this signaling pathway in the activity of cultured hippocampal neurons, we found that rapamycin significantly reduces the spontaneous activities of network neurons as well as the efficacy of synaptic transmission through insulin-mTOR signaling pathway. Our study sheds light on understanding the role of mTOR signaling pathway in controlling the information processing of network neurons.

Deoxyschisandrin modulates synchronized Ca2+ oscillations and spontaneous synaptic transmission of cultured hippocampal neurons.

AIM: Deoxyschisandrin is one of the most effective composites of Schisandra chinensis, a famous Chinese medicine widely used as an antistress, anti-aging, and neurological performance-improving herb. In this study, we examined its specific mechanisms of action on cultured hippocampal neurons. METHODS: Hippocampal neurons, primarily cultured for 9-11 d in vitro, were used for this study. DS were dissolved in DMSO and applied to calcium imaging and whole-cell patch clamp. RESULTS: The application of 3 mg/L DS decreased the frequency of spontaneous and synchronous oscillations of intracellular Ca2+ to 72%+/-2% (mean+/-SEM), and the spontaneous inhibitory postsynaptic currents to 60%+/-3% (mean+/-SEM). The inhibitory concentration 50% (IC50) for the effect of DS on calcium oscillations was 3.8 mg/L. DS also depressed the high voltage-gated Ca2+ channel and the voltage-gated Na+ channel currents at the same time point. It had no effect, however, on voltage-gated K+ and spontaneous excitatory postsynaptic currents. CONCLUSION: DS inhibited the spontaneous and synchronous oscillations of intracellular Ca2+ through the depression of influx of extracellular calcium and the initiation of action potential. By repressing the spontaneous neurotransmitter release, DS modulated the neuronal network activities.

A new track for understanding the pathogenesis of multiple sclerosis: from the perspective of early developmental deficit caused by the potential 5-HT deficiency in individuals in high-latitude areas.

The association between the prevalence of multiple sclerosis (MS) and latitude gradient indicates the importance of environmental factors in MS susceptibility. Studies on immigrants have shown that the living environment in the first two decades of life determines MS risk, suggesting that early development may be critical for the occurrence of MS in adulthood. The level of 5-hydroxytryptamine (5-HT) in individuals living in high-latitude areas might be decreased because of limited levels of its metabolic precursor, the essential amino acid tryptophan, and superabundant levels of its metabolic product, melatonin, attributable to long duration of darkness in high-latitude areas. Considering the significant loss and damage of myelin observed in many psychiatric disorders with the etiology of 5-HT deficiency, we hypothesize that 5-HT deficiency due to superabundant synthesis of melatonin in individuals living in high-latitude areas may potentially cause the developmental myelin deficit early in life. This developmental deficit may play an important role in triggering MS in adulthood. This is the first proposal of the potential role of early development in the susceptibility to MS, and we suggest monitoring 5-HT levels in both patients with MS and in individuals with high environmental risk, especially children living in high-latitude areas. This will validate our hypothesis and contribute to designing specific preventive strategies that can be applied early in life.

Invivo insulin deficiency as a potential etiology for demyelinating disease.

Demyelinating disease is pathologically characterized by the death of mature oligodendrocytes that normally synthesize myelin to perform insulating functions. Moreover, demyelinating disease also results in the failure of remyelination process in which oligodendrocyte progenitor cells reactivate and differentiate into new oligodendrocytes. Thus, this disease reflects decreased nerve conduction velocity and eventually dysfunction of the nervous system. A notable fact in the clinic is that demyelination is one of the most common diabetes-induced complications, implying that demyelinating disease may be relevant to insulin deficiency in vivo. However, the explicit pathological relationship between demyelination and diabetes remains unclear. Mainstream theories posit that demyelinating disease is an autoimmune disease arising from abnormal immunological reactions, but this perspective is limited when applied to the clinic. Olig1 is a vital transcription factor involved in oligodendrogenesis and is essential for the survival and maturation of oligodendrocyte progenitor cells. Furthermore, Olig1 is required for the onset of remyelination in adults. In the present study, we serendipitously found by means of protein immunoblot that the expression of nuclear Olig1 was inhibited when mouse oligodendrocyte progenitor cells were cultured in the absence of insulin. Combining this finding with the clinical relevance of demyelination and diabetes, we hypothesize that in vivo insulin deficiency impairs the reactivation and differentiation of oligodendrocyte progenitor cells through downregulation of nuclear Olig1 expression and therefore hinders the remyelination, which is an important process required for functional recovery in demyelinating disease. This hypothesis implies that in vivo insulin deficiency may be a novel etiological cause of demyelinating disease and thus contribute to improved the clinical therapies for remyelination repair. We suggest that sustaining normal insulin levels and stable nuclear Olig1 expression in vivo can be new therapeutic targets for remyelination repair and diabetic neuropathy. In addition, with respect to the clinical transplantation of oligodendrocyte progenitor cells for remyelination repair, supplementing cell suspensions that are to be transplanted with appropriate doses of insulin potentially may facilitate adaptation of the transplanted progenitor cells to the heterogeneous and pathological environment in vivo and eventually improve the efficacy of the cellular transplantation.

Acute impairment of mitochondrial trafficking by beta-amyloid peptides in hippocampal neurons.

Defects in axonal transport are often associated with a wide variety of neurological diseases including Alzheimer's disease (AD). Beta-amyloid (Abeta) is a major component of neuritic plaques associated with pathological conditions of AD brains. Here, we report that a brief exposure of cultured hippocampal neurons to Abeta molecules resulted in rapid and severe impairment of mitochondrial transport without inducing apparent cell death and significant morphological changes. Such acute inhibition of mitochondrial transport was not associated with a disruption of mitochondria potential nor involved aberrant cytoskeletal changes. Abeta also did not elicit significant Ca2+ signaling to affect mitochondrial trafficking. However, stimulation of protein kinase A (PKA) by forskolin, cAMP analogs, or neuropeptides effectively alleviated the impairment. We also show that Abeta inhibited mitochondrial transport by acting through glycogen synthase kinase 3beta (GSK3beta). Given that mitochondria are crucial organelles for many cellular functions and survival, our findings thus identify an important acute action of Abeta molecules on nerve cells that could potentially contribute to various abnormalities of neuronal functions under AD conditions. Manipulation of GSK3beta and PKA activities may represent a key approach for preventing and alleviating Abeta cytotoxicity and AD pathological conditions.

Effects of insulin-like growth factor 1 on voltage-gated ion channels in cultured rat hippocampal neurons.

Insulin-like growth factor 1 (IGF-1) has important functions in the brain, including metabolic, neurotrophic, neuromodulatory, and neuroendocrine actions, and it is also prevents amyloid beta-induced death of hippocampal neurons. However, its functions on the voltage-gated ion channels in hippocampus remain uncertain. In the present study, we investigated the effects of IGF-1 on voltage-gated potassium, sodium, and calcium channels in the cultured rat hippocampal neurons using the whole-cell patch clamp recordings. Following incubation with different doses of IGF-1 for 24 h, a block of the peak transient A-type K+ currents amplitude (IC50: 4.425 ng/ml, Hill coefficient: 0.621) was observed. In addition, after the application of IGF-1, the amplitude of high-voltage activated Ca2+ currents significantly increased but activation kinetics did not significantly alter (V1/2: -33.45 +/- 1.32 mV, k = 6.16 +/- 1.05) compared to control conditions (V1/2: -33.19 +/- 2.28 mV, k = 7.26 +/- 1.71). However, the amplitude of Na+, K+, and low-voltage activated Ca2+ currents was not affected by the application of IGF-1. These data suggest that IGF-1 inhibits transient A-type K+ currents and enhances high-voltage-activated Ca2+ currents, but has no effects on Na+ and low-voltage-activated Ca2+ currents.

Frequency modulation of synchronized Ca2+ spikes in cultured hippocampal networks through G-protein-coupled receptors.

Synchronized spontaneous Ca2+ spikes in networked neurons represent periodic burst firing of action potentials, which are believed to play a major role in the development and plasticity of neuronal circuitry. How these network activities are shaped and modulated by extrinsic factors during development, however, remains to be studied. Here we report that synchronized Ca2+ spikes among cultured hippocampal neurons can be modulated by two small factors that act on G-protein-coupled receptors (GPCRs): the neuropeptide PACAP (pituitary adenylate cyclase-activating polypeptide) and the chemokine SDF-1 (stromal cell-derived factor-1). PACAP effectively increases the frequency of the synchronized Ca2+ spikes when applied acutely; the PACAP potentiation of Ca2+ spikes requires the activation of the PACAP-specific PAC1 GPCRs and is mediated by the activation of cAMP signaling pathway. SDF-1, on the other hand, significantly reduces the frequency of these Ca2+ spikes through the activation of its specific GPCR CXCR4; the inhibitory action of SDF-1 is mediated by the inhibition of cAMP pathway through the Gi component of GPCRs. Taken together, these results demonstrate that synchronized neuronal network activity can be effectively modulated by physiologically and developmentally relevant small factors that act on GPCRs to target the cAMP pathway. Such modulation of neuronal activity through GPCRs may represent a significant mechanism that underlies the neuronal plasticity during neural development and functioning.

A role of insulin-like growth factor 1 in beta amyloid-induced disinhibition of hippocampal neurons.

In the present study we investigated the effects of beta amyloid (Abeta) on inhibitory synaptic transmission in the cultured hippocampal neurons using whole-cell patch-clamp recordings and immunocytochemistry, and examined the role of insulin-like growth factor 1 (IGF-1). Incubation with 4 microM Abeta25-35 for 24 h significantly decreased the frequency of spontaneous inhibitory postsynaptic currents (sIPSCs), but had no effect on the mean amplitude. Pretreatment with 10 ng/ml IGF-1 for 24h prior to Abeta25-35 exposure blocked Abeta-induced disinhibition of hippocampal neurons. The frequency and mean amplitude of miniature IPSC (mIPSCs) were not significantly affected by Abeta. The rise and decay kinetics of sIPSCs and mIPSCs were similar for the control and Abeta25-35-treated hippocampal neurons. Immunocytochemistry showed no changes in the ratio of gamma-aminobutyric acid (GABA) positive cells subsequent to treatment with Abeta, or IGF-1. Together these data suggest that Abeta-induced the disinhibition in cultured hippocampal neurons, whereas IGF-1 could block this effect.

Survival and differentiation of dopaminergic neurons can be regulated by soluble factors from cortex in vitro.

The transplantation of dopaminergic (DA) neurons is used for treating Parkinson's disease. However, their actual application is restricted by a limited source of DA cells. Here we report that DA cells can be increased 5- to 10-fold in vitro by the soluble factors from cortex in early developmental stages, which is much more than any previously identified growth factors such as BDNF, GDNF and NT3. We also show that the effect of the soluble factors from cortex is stronger than those of midbrain at embryonic early developmental ages. In contrast, at middle ages the soluble factors from midbrain present a much stronger effect. These findings suggest that the development of DA cells may be regulated by growth factors in a complex spatial and temporal network.

Dopaminergic neuron differentiation of ventral mesencephalic progenitors regulated by developmental signals in vitro.

Extrinsic signals play an important role in the differentiation of neural progenitor cells, but little is known about the underlying mechanism. In order to investigate how extrinsic signals influence the fate switch of progenitors during development, we cultured ventral mesencephalic progenitors from E13 and E16 rats in the presence of soluble factors. Here we report that soluble factors in early developmental stages can induce the production of dopaminergic neurons. E16 may be an important developmental stage in which the responsiveness of the progenitors to the soluble factors is much more sensitive. Our results indicate that a combination of cell-intrinsic changes and extrinsic cues controls the competence of mesencephalic progenitors to produce dopaminergic neurons. Cell fate restriction may result from a series of extrinsic factors acting on a multipotent progenitor progressively.

Heparin regulates survival and differentiation of mesencephalic progenitors mediated via FGF2 in vitro.

Heparin plays an important role in the survival and differentiation of mesencephalic progenitors mediated by FGF-2 in vitro. If the heparin concentration is gradually increased, cell survival mediated by FGF-2 can be greatly enhanced, to a maximum concentration of 20 ng/ml FGF-2 from 5 microg/ml heparin. However, differentiation of FGF-2 responsive mesencephalic progenitors is inhibited by heparin. When cortical, mesencephalic and hippocampal astrocytes were primed with FGF-2 and heparin, the latter two astrocytes promoted the differentiation of TH-positive neurons from mesencephalic progenitors. RT-PCR analysis showed that FGFR1, FGFR2 and FGFR3 were expressed in the cortical astrocytes, but only FGFR1 and FGFR3 were expressed in the mesencephalic and hippocampal astrocytes.

Effect of new O-superfamily conotoxin SO3 on sodium and potassium currents of cultured hippocampal neurons.

The effects of a new O-superfamily conotoxin SO3 on sodium and potassium currents were examined in cultured rat hippocampal neurons using the whole-cell patch clamp technique. SO3 caused a concentration-dependent, rapidly developing and reversible inhibition of sodium currents (I(Na)). The IC(50) value for the blockage of I(Na) was calculated to be 0.49 and the Hill coefficient was 1.7. Using electrophysiological and pharmacological protocols, transient A-type potassium currents (I(A)) and delayed rectifiers potassium currents (I(K)) were isolated. SO3 caused a concentration-dependent, and reversible inhibition of I(K). The IC(50) value for the blockage of I(K) was calculated to be 1.6 and the Hill coefficient was 0.6, with no significant effect on I(A). These results indicate that SO3 can selectively inhibit neuronal sodium and potassium currents.

New insight from using spatiotemporal image correlation in prenatal screening of fetal conotruncal defects.

BACKGROUND: : To establish the reference range of the angle between ascending aorta and main pulmonary artery of fetus in the second and third trimester using spatiotemporal image correlation (STIC), and to investigate the value of this angle in prenatal screening of conotruncal defects (CTDs). MATERIALS AND METHODS: Volume images of 311 normal fetuses along with 20 fetuses with congenital heart diseases were recruited in this cross-sectional study. An offline analysis of acquired volume datasets was carried out with multiplanar mode. The angle between aorta and pulmonary artery was measured by navigating the pivot point and rotating axes and the reference range was established. The images of ascending aorta and main pulmonary artery in fetuses with congenital heart diseases were observed by rotating the axes within the normal angle reference range. RESULTS: THE ANGLE BETWEEN ASCENDING AORTA AND MAIN PULMONARY ARTERY OF THE NORMAL FETUS (RANGE: 59.1˚~97.0˚, mean ± SD: 78.0˚ ± 9.7˚) was negatively correlated with gestational age (r = -0.52; p<0.01). By rotating the normal angle range corresponding to gestational age, the fetuses with CTD could not display views of their left ventricular long axis and main pulmonary trunk correctly. CONCLUSION: The left ventricular long axis and main pulmonary trunk views can be displayed using STIC so that the echocardiographic protocol of the cardiovascular joint could be standardized. The reference range of the angle between ascending aorta and main pulmonary artery is clinically useful in prenatal screening of CTD and provides a reliable quantitative standard to estimate the spatial relationship of the large arteries of fetus.

TRPV1: a potential target for antiepileptogenesis.

Epilepsy is one of the most common diseases in neurology department. It is caused by many different kinds of perturbances of normal balance of excitation and inhibition within the central nervous system. Current clinical antiepileptic drugs (AEDs) targets include ion channels, neurotransmitter transporters and neurotransmitter metabolic enzymes. They could control about 70-80% of the patients' symptoms; 20-30% patients develop to be intractable epilepsy sufferers. Moreover, antiepileptic drugs could not prevent formation of foci and disease process, but only alleviate symptoms of seizures at risk of different adverse effects as the consequences of large doses. Recently, impressive data on the actions of transient receptor potential vanilloid receptor 1 (TRPV1) prove it to be an inspiring antiepileptogenic target. TRPV1 activation modulates activity-dependent synaptic efficacy: (i) facilitating long-term potentiation (LTP) and suppressing long-term depression (LTD) of hippocampal neurons (ii) selectively inhibiting excitatory synapses onto hippocampal interneurons, which is expected to increase the excitability of innervated pyramidal cells. Nerve growth factor (NGF) can acutely and chronically upregulates TRPV1 expression, suggesting that TRPV1 channels would play an important role in the course of NGF regulated epileptogenesis. Endocannabinoid anandamide (AEA) is one of the TRPV1 endogenous agonists. It has been proved that, in the course of epilepsy, AEA levels increases due to enhanced formation and both exogenously administered and endogenously produced AEA display proconvulsant activity. Moreover, TRPV1 activation triggers apoptotic neuronal death of rat cortical cultures, which may be responsible, at least in part, for the volume loss of neocortex in chronic epilepsy. Our hypothesis may broaden the drug screening and designing for clinical strategies for epilepsy treatment.

Calcium near the release site is essential for basal ACh release in Xenopus.

Extracellular calcium is essential for neurotransmitter release, but the detailed mechanism by which Ca2+ regulates basal synaptic release has not yet been fully explored. In this study, calcium imaging and the whole-cell patch-clamp technique were used to investigate the role of Ca2+ in basal acetylcholine (ACh) release in the Xenopus neuromuscular junction and in isolated myocytes exogenously loaded with ACh. Carried out in normal and Ca2+-free extracellular solution, the results indicate that Ca2+ near the release site is essential for basal neurotransmitter release.