Dynamic control of neuroexocytosis by phosphoinositides in health and disease.

Phosphoinositides are a group of phospholipids whose inositol headgroups can be phosphorylated at three distinct positions thereby generating seven different isotypes. The conversion between these lipid species depends on the activity of specific sets of phosphoinositide kinases and phosphatases whose targeting and activity is critical to establish the landscape of phosphoinositides on the cytosol-facing hemi-membrane of all organelles and plasmalemma. Phosphoinositides play pleiotropic roles ranging from signalling and membrane trafficking to modulation of ion channels and survival. In neurons and neurosecretory cells, whose main function is to communicate through the release of neurotransmitter, most of the work has focused on the role played by phosphatidylinositol (4,5) bisphosphate in controlling the mechanism underpinning neurotransmitter release through the fusion of secretory vesicles with the plasmalemma. Emerging evidence supports a multi-faceted regulation of neuroexocytosis by 3-phosphorylated phosphoinositides. In this review, we summarise the molecular mechanism by which these lipids control exocytosis and how minute changes in their metabolism can have devastating effects in the nervous system and lead to neurodegeneration.

Nogo A expression in the adult enteric nervous system.

Neuronal plasticity plays an important role in physiological and pathological processes within the gastrointestinal (GI) tract. Nogo A is a major contributor to the negative effect central nervous system (CNS) myelin has on neurite outgrowth after injury and may also play a role in maintaining synaptic connections in the healthy CNS. Nogo A is highly expressed during neuronal development but in the CNS declines postnatally concomitantly with a loss of regenerative potential while ganglia of the Peripheral Nervous System (PNS) retain Nogo A. The enteric nervous system shares a number of features in common with the CNS, thus the peripheral distribution of factors affecting plasticity is of interest. We have investigated the distribution of Nogo in the adult mammalian gastrointestinal tract. Nogo A mRNA and protein are detectable in the adult rat GI tract. Nogo A is expressed heterogeneously in enteric neurons throughout the GI tract though expression levels appear not to be correlated with neuronal sub-type. The pattern of expression is maintained in cultured myenteric plexus from the guinea-pig small intestine. As is seen in developing neurons of the CNS, enteric Nogo A is present in both neuronal cell bodies and axons. Our results point to a hitherto unsuspected role for Nogo A in enteric neuronal physiology.

Use of Spectral Radiance to Estimate In-Season Biomass and Grain Yield in Nitrogen- and Water-Stressed Corn.

Current technologies for measuring plant water status are limited, while recently remote sensing techniques for estimating N status have increased with limited research on the interaction between the two stresses. Because plant water status methods are time-consuming and require numerous observations to characterize a field, managers could benefit from remote sensing techniques to assist in irrigation and N management decisions. A 2-yr experiment was initiated to determine specific wavelengths and/or combinations of wavelengths indicative of water stress and N deficiencies, and to evaluate these wavelengths for estimating in-season biomass and corn (Zea mays L.) grain yield. The experiment was a split-plot design with three replications. The treatment structure had five N rates (0, 45, 90, 134, and 269 kg N ha(-1)) and three water treatments [dryland, 0.5 evapotranspiration (ET), and full ET]. Canopy spectral radiance measurements (350-2500 nm) were taken at various growth stages (V6-V7, V13-V16, and V14-R1). Specific wavelengths for estimating crop biomass, N concentration, grain yield, and chlorophyll meter readings changed with growth stage and sampling date. Changes in total N and biomass in the presence of a water stress were estimated using near-infrared (NIR) reflectance and the water absorption bands. Reflectance in the green and NIR regions were used to estimate total N and biomass without water stress. Reflectance at 510, 705, and 1135 nm were found for estimating chlorophyll meter readings regardless of year or sampling date.

Phosphoinositides as key regulators of synaptic function.

Phosphoinositides have recently emerged as key regulators of a variety of synaptic processes, including neurosecretory vesicle targeting, exo-endocytosis, and ion channel modulation. These pleiotropic activities derive from their ability to serve either as membrane targeting sites for cytosolic factors, as allosteric ligands, or as nucleation points for coat proteins and cytoskeletal elements. This versatility depends upon the existence of highly diversified enzymatic machinery for their synthesis and degradation, which governs, both temporally and spatially, their appearance in the microenvironment of the synapse.

Nuclear PtdIns(4,5)P2 assembles in a mitotically regulated particle involved in pre-mRNA splicing.

Phosphoinositide turnover regulates multiple cellular processes. Compared with their well-known cytosolic roles, limited information is available on the functions of nuclear phosphoinositides. Here, we show that phosphatidylinositol(4,5)-bisphosphate (PtdIns(4,5)P2) stably associates with electron-dense particles within the nucleus that resemble interchromatin granule clusters. These PtdIns(4,5)P2-containing structures have a distribution which is cell-cycle dependent and contain components of both the transcriptional and pre-mRNA processing machinery, including RNA polymerase II and the splicing factor SC-35. Immunodepletion and add-back experiments demonstrate that PtdIns(4,5)P2 and associated factors are necessary but not sufficient for pre-mRNA splicing in vitro, indicating a crucial role for PtdIns(4,5)P2-containing complexes in nuclear pre-mRNA processing.

Craving predicts use during treatment for methamphetamine dependence: a prospective, repeated-measures, within-subject analysis.

Clinical lore dictates that craving drives the compulsive use of drugs and alcohol - the core feature of substance dependence. Yet limited research has yielded mixed results, suggesting that craving is neither necessary nor sufficient for continued use or relapse to addictive substances. To investigate the role of craving in compulsive methamphetamine use, 31 men and women in treatment for methamphetamine dependence were asked to indicate, once each week for 12 weeks, the severity of craving that they had experienced during the previous 24 h, using a 100-mm visual analog scale. In a prospective, repeated-measures, within-subject analysis, craving intensity significantly predicted methamphetamine use in the week immediately following each craving report. Craving remained a highly significant predictor in multivariate models controlling for pharmacological intervention, and for methamphetamine use during the prior week. Craving scores that preceded use were 2.7 times higher than scores that preceded abstinence. Risk of subsequent use was 2.5 times greater for scores in the upper half of the scale relative to scores in the lower half. The results obtained demonstrate that, while craving alone may be neither necessary nor sufficient to explain substance addiction, when measured prospectively in a carefully-designed study craving emerges as a salient predictive factor in continued methamphetamine use for patients in treatment for methamphetamine dependence.

Abuse and therapeutic potential of gamma-hydroxybutyric acid.

Gamma-hydroxbutyric acid is a compound found in mammalian brain that is structurally related to the neurotransmitters gamma-aminobutyric acid and glutamic acid. Gamma-hydroxybutyric acid effects dopaminergic systems in the brain and may be a neurotransmitter. Gamma-hydroxybutyric acid was first reported as a drug of abuse in 1990 and continues to be abused by bodybuilders, participants of "rave" dance parties, and polydrug abusers. Physical dependence can develop after prolonged, high-dose use, and overdoses have been widely reported. Its use in sexual assaults as a "date rape" drug and availability on the internet have recently emerged. Gamma-hydroxybutyric acid has established efficacy as an anesthetic agent, and preliminary evidence supports its utility in the treatment of alcohol dependence, opiate dependence, and narcolepsy.

Functional characterisation of tetanus and botulinum neurotoxins binding domains.

Tetanus and botulinum neurotoxins constitute a family of bacterial protein toxins responsible for two deadly syndromes in humans (tetanus and botulism, respectively). They bind with high affinity to neurons wherein they cause a complete inhibition of evoked neurotransmitter release. Here we report on the cloning, expression and use of the recombinant fragments of the heavy chains of tetanus neurotoxin and botulinum neurotoxin serotypes A, B and E as tools to study the neurospecific binding of the holotoxins. We found that the recombinant 50 kDa carboxy-terminal domains of tetanus and botulinum neurotoxins alone are responsible for the specific binding and internalisation into spinal cord cells in culture. Moreover, we provide evidence that the recombinant fragments block the internalization of the parental holotoxins in a dose-dependent manner, as determined by following the neurotoxin-dependent cleavage of their targets VAMP/synaptobrevin and SNAP-25. In addition, the recombinant binding fragments cause a significant delay in the paralysis induced by the corresponding holotoxin on the mouse phrenic nerve-hemidiaphragm preparation. Taken together, these results show that the carboxy-terminal domain of tetanus and botulinum neurotoxins is necessary and sufficient for the binding and internalisation of these proteins in neurons and open the possibility to use them as tools for the functional characterisation of the intracellular transport of clostridial neurotoxins.

Calcium-dependent oligomerization of synaptotagmins I and II. Synaptotagmins I and II are localized on the same synaptic vesicle and heterodimerize in the presence of calcium.

Synaptotagmins constitute a large family of membrane proteins characterized by their distinct distributions and different biochemical features. Genetic evidence suggests that members of this protein family are likely to function as calcium sensors in calcium-regulated events in neurons, although the precise molecular mechanism remains ill defined. Here we demonstrate that different synaptotagmin isoforms (Syt I, II, and IV) are present in the same synaptic vesicle population from rat brain cortex. In addition, Syt I and II co-localize on the same small synaptic vesicle (SSV), and they heterodimerize in the presence of calcium with a concentration dependence resembling that of the starting phase of SSV exocytosis (EC50 = 6 +/- 4 microM). The association between Syt I and Syt II was demonstrated by immunoprecipitation of the native proteins and the recombinant cytoplasmic domains and by using fluorescence resonance energy transfer (FRET). Although a subpopulation of SSV containing Syt I and IV can be isolated, these two isoforms do not show a calcium-dependent interaction. These results suggest that the self-association of synaptotagmins with different calcium binding features may create a variety of calcium sensors characterized by distinct calcium sensitivities. This combinatorial hypothesis predicts that the probability of a single SSV exocytic event is determined, in addition to the gating properties of the presynaptic calcium channels, by the repertoire and relative abundance of distinct synaptotagmin isoforms present on the SSV surface.

Sex-role attitudes and clinical appraisal in psychiatry residents.

OBJECTIVE: To measure sex-role beliefs of psychiatry residents and to examine bias in clinical appraisal. METHOD: Residents (45 female, 51 male) evaluated 1 of 4 possible clinical case histories-a female or male patient with histrionic personality disorder (HPD) or antisocial personality disorder (APD)-and completed the Sex-Role Egalitarianism Scale (SRES). RESULTS: As predicted, female residents were more egalitarian than male residents (P < 0.03) according to the SRES. As expected, significantly more male than female patients received the diagnosis of APD (P < 0.00002). Although it was predicted that female patients would more often be given the HPD diagnosis than males, no significant gender differences were found. Sex of resident was not found to influence clinical behaviour significantly. CONCLUSIONS: These results highlight differential sex-role attitudes, as measured by the SRES, between female and male residents and suggest that residents' sex-role biases affect the diagnosis of APD. These results have implications for psychiatric assessment and treatment. Further understanding of these issues is critical to the development of educational tools to address sex biases in psychiatry.