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981.
Bortolozzi A Díaz-Mataix L Scorza MC Celada P Artigas F 《Journal of neurochemistry》2005,95(6):1597-1607
Atypical antipsychotics show preferential 5-HT 2A versus dopamine (DA) D2 receptor affinity. At clinical doses, they fully occupy cortical 5-HT2 receptors, which suggests a strong relationship with their therapeutic action. Half of the pyramidal neurones in the medial prefrontal cortex (mPFC) express 5-HT 2A receptors. Also, neurones excited through 5-HT 2A receptors project to the ventral tegmental area (VTA). We therefore hypothesized that prefrontal 5-HT 2A receptors can modulate DA transmission through excitatory mPFC-VTA inputs. In this study we used single unit recordings to examine the responses of DA neurones to local (in the mPFC) and systemic administration of the 5-HT 2A/2C agonist 1-[2,5-dimethoxy-4-iodophenyl-2-aminopropane] (DOI). Likewise, using microdialysis, we examined DA release in the mPFC and VTA (single/dual probe) in response to prefrontal and systemic drug administration. The local (in the mPFC) and systemic administration of DOI increased the firing rate and burst firing of DA neurones and DA release in the VTA and mPFC. The increase in VTA DA release was mimicked by the electrical stimulation of the mPFC. The effects of DOI were reversed by M100907 and ritanserin. These results indicate that the activity of VTA DA neurones is under the excitatory control of 5-HT 2A receptors in the mPFC. These observations may help in the understanding of the therapeutic action of atypical antipsychotics. 相似文献
982.
NMDA (N-methyl-D-aspartate) subtype of glutamate receptors are core components of dendritic spine postsynaptic densities (PSDs), in which they are anchored via their carboxy-terminal tails to cytoskeletal proteins. In this study, we examined the role of the neuronal intermediate filament protein, neurofilament-light (NF-L), also a component of the PSD, in the regulation of NMDA receptor (NMDAR) expression and function in a heterologous system. Coexpression of NF-L with NR1 or NR2B subunits of the NMDAR in HEK293 (human embryonic kidney 293) cells did not result in surface expression as measured by surface biotinylation and cell ELISAs, whereas the combined expression of the three elements resulted in a 20% increase in the surface abundance of NR1, along with a concomitant increase in NMDAR-mediated cytotoxicity. Investigating the origin of this increase, we found that the NR1 subunits are ubiquitinated in HEK293 cells, and that the coexpression of NF-L antagonizes this process. These results suggest a possible means of stabilization of NR1 via its association with NF-L. 相似文献
983.
Butovsky E Juknat A Goncharov I Elbaz J Eilam R Zangen A Vogel Z 《Journal of neurochemistry》2005,93(4):802-811
Cannabinoids are widely abused drugs. Here we show that chronic administration of Delta(9)-tetrahydrocannabinol (Delta(9)-THC), the active psychotropic agent in marijuana and hashish, at 1.5 mg per kg per day intraperitoneally for 7 days, increases the expression, at both mRNA and protein levels, of brain-derived neurotrophic factor (BDNF), in specific rat brain areas, notably in those involved in reward and addiction. Real-time PCR revealed a 10-fold up-regulation of BDNF mRNA in the nucleus accumbens (NAc) upon chronic Delta(9)-THC treatment, but there was no change at 3 or 24 h after a single injection. Smaller increases in mRNA levels were found in the ventral tegmental area (VTA), medial prefrontal cortex and paraventricular nucleus (PVN). Immunohistochemistry showed large increases in BDNF-stained cells in the NAc (5.5-fold), posterior VTA (4-fold) and PVN (1.7-fold), but no change was observed in the anterior VTA, hippocampus or dorsal striatum. Altogether, our study indicates that chronic exposure to Delta(9)-THC up-regulates BDNF in specific brain areas involved with reward, and provides evidence for different BDNF expression in the anterior and posterior VTA. Moreover, BDNF is known to modulate synaptic plasticity and adaptive processes underlying learning and memory, leading to long-term functional and structural modification of synaptic connections. We suggest that Delta(9)-THC up-regulation of BDNF expression has an important role in inducing the neuroadaptive processes taking place upon exposure to cannabinoids. 相似文献
984.
Response Surface Analysis of Solid State Growth of <Emphasis Type="Italic">Pleurotus ostreatus</Emphasis> Mycelia utilizing Whey Permeate 总被引:1,自引:0,他引:1
A novel approach to utilizing whey permeate, the cultivation of mycelia of the edible mushroom Pleurotus ostreatus, is introduced. Response surface analysis (RSA) was successfully applied to determine the combination of substrate concentration,
temperature and pH that would result in a maximal mycelial extension rate under solid state cultivation. The conditions to
maximize the mycelial extension rate were predicted to be 44 g lactose l−1, pH 6.0 and 24.2 °C. Subsequent verification of these levels agreed with model predictions. 相似文献
985.
Theaflavins were synthesized from tea polyphenols extracted from green tea using an immobilized polyphenol oxidase system. To optimize the production of theaflavins, response surface methodology was applied to determine the effects of five critical variables and their mutual interactions on theaflavin biosynthesis at five levels. A total of 52 individual experiments were performed and a statistical model predicted that the highest theaflavin concentration was 0.766mgml–1 at optimized conditions. Using these optimal parameters under experimental conditions in three independent replicates, the average value of the biosynthesized theaflavin concentration reached 0.75±0.017mgml–1 and matched the value predicted by the modelRevisions requested 03 November 2004; Revisions received 7 December 2004 相似文献
986.
Population density, one of the most fundamental demographic attributes, may vary systematically with spatial scale, but this
scale-sensitivity is incompletely understood. We used a novel approach—based on fully censused and mapped distributions of
eastern grey squirrel (Sciurus carolinensis) dreys, beaver (Castor canadensis) lodges, and moose (Alces alces)—to explore the scale-dependence of population density and its relationship to landscape features. We identified population
units at several scales, both objectively, using cluster analysis, and arbitrarily, using artificial bounds centred on high-abundance
sites. Densities declined with census area. For dreys, this relationship was stronger in objective versus arbitrary population
units. Drey density was inconsistently related to patch area, a relationship that was positive for all patches but negative
when non-occupied patches were excluded. Drey density was negatively related to the proportion of green-space and positively
related to the density of buildings or roads, relationships that were accentuated at coarser scales. Mean drey densities were
more sensitive to scale when calculated as organism-weighted versus area-weighted averages. Greater understanding of these
scaling effects is required to facilitate comparisons of population density across studies. 相似文献
987.
We studied leaf area and nitrogen dynamics in the canopy of stands of an annual herb Xanthium canadense, grown at a high (HN)- and a low-nitorgen (LN) availability. Standing leaf area increased continuously through the vegetative
growth period in the LN stand, or leveled off in the later stage in the HN stand. When scaled against standing leaf area,
both production and loss rates of leaf area increased but with different patterns: the production rate was retarded, while
the loss rate was accelerated, implying an upper limit of standing leaf area of the canopy. The rate of leaf-area production
was higher in the HN than in the LN stand, which was caused by the higher rate of leaf production per standing leaf area as
well as the greater standing leaf area in the HN stand. Although the rate of leaf-area loss was higher in the HN than in the
LN stand, it was not significantly different between the two stands when compared at a common standing leaf area, suggesting
involvement of light climate in determination of the leaf-loss rate. On the other hand, the rate of leaf-area loss was positively
correlated with nitrogen demand for leaf area development across the two stands, suggesting that leaf loss was caused by retranslocation
of nitrogen for construction of new leaves. A simple simulation model of leaf and nitrogen dynamics in the canopy showed that,
at steady state, where the rate of leaf-area loss becomes equal to the production rate, the standing leaf area was still greater
in the HN than in the LN stand. Similarly, when the uptake and loss of nitrogen are equilibrated, the standing nitrogen was
greater in the HN than in the LN stand. These results suggest that leaf-area production is strongly controlled by nitrogen
availability, while both nitrogen and light climate determine leaf-loss rates in the canopy. 相似文献
988.
Phosphorus nutrition-mediated effects of arbuscular mycorrhiza on leaf morphology and carbon allocation in perennial ryegrass 总被引:1,自引:0,他引:1
The aim of this work was to disentangle phosphorus status-dependent and -independent effects of arbuscular mycorrhizal fungus (AMF) on leaf morphology and carbon allocation in perennial ryegrass (Lolium perenne). To this end, we assessed the P-response function of morphological components in mycorrhizal and nonmycorrhizal plants of similar size. AMF (Glomus hoi) stimulated relative P-uptake rate, decreased leaf mass per area (LMA), and increased shoot mass ratio at low P supply. Lower LMA was caused by both decreased tissue density and thickness. Variation in tissue density was almost entirely caused by variations in soluble C, while that in thickness involved structural changes. All effects of AMF were indistinguishable from those mediated by increases in relative P-uptake rate through higher P-supply rates. Thus the relationships between relative P-uptake rate, leaf morphology and C allocation were identical in mycorrhizal and nonmycorrhizal plants. No evidence was found for AMF effects not mediated by changes in plant P status. 相似文献
989.
We investigated the effect of proximity to forest edge on plant community structure and ecosystem properties during succession, using field measurements of leaf area index (LAI), species composition, and soil carbon. Data were collected along four transects within a 14-year-old temperate successional field in north-central Virginia over the 2000 growing season. Additionally, the normalized difference vegetation index (NDVI) was calculated from LANDSAT 7 satellite data at a resolution of 30 m for the entire field. Results showed that relative frequencies of trees increased with proximity to forest edge suggesting a more advanced stage of succession in areas close to the adjacent secondary forest. Significant negative relationships were observed between distance from forest edge and both peak season LAI and NDVI. LAI and NDVI values within 60 m of the forest edge, however, were not significantly different from those values in the adjacent mature secondary forest, suggesting that some community level properties may take relatively short periods of time to reach undisturbed states. The presence of several key plant species, particularly Celastrus scandens (climbing bittersweet), exhibited a strong control on the spatial variability of LAI and potentially the aboveground net primary production. Soil carbon levels did not show a significant increase at sites close to the adjacent secondary forest (relative to an adjacent crop field), as seen with LAI and NDVI, suggesting no recovery of soil carbon in these systems after 14 years. This study points to the complexity of factors that influence spatial patterns of succession in old-fields and suggests that invasive species may play an important role in successional pathways and carbon cycling. 相似文献
990.
Earlier research has shown that exogenous gibberellic acid (GA3) application increases shoot growth, photosynthesis and soil nitrogen (N) utilisation in mustard (Brassica juncea L. Czern & Coss.). Mustard has a high sulfur (S) requirement. Its assimilatory pathway is well coordinated with N and dependent on photosynthesis. Thus, the higher photosynthate production and an efficient use of N with the use of GA3 could result in an increase in S-use efficiency of the crop. The research was, therefore, carried out to study the effects of 10~M GA3 spray on specific leaf area, plant dry mass, leaf carbon dioxide exchange rate (CER), plant growth rate (PGR), relative growth rate (RGR), net assimilation rate (NAR) and S-use efficiency (SUE) of mustard treated with 0, 100 or 200 mg S kg–1 soil levels. Plants treated with 100~mg S kg–1 soil and receiving GA3 treatment showed increased specific leaf area and dry mass accumulation compared to the control. At 0~mg S kg–1 soil, N and S concentrations were reduced. They increased with increasing S supply. GA3 application significantly increased N and S concentrations further. A two-fold increase in SUE in GA3-treated plants at 100~mg S kg–1 soil was noted in comparison to the control. SUE was not increased under excess S conditions beyond 100~mg S kg–1 soil. The increase in SUE was through increase in the growth, CER and use efficiency of N by the crop due to GA3 application. 相似文献