The inhibitory action of exo- and endocannabinoids on [³H]GABA release are mediated by both CB₁and CB₂receptors in the mouse hippocampus

Exogenous and endogenous cannabinoids play an important role in modulating the release of neurotransmitters in hippocampal excitatory and inhibitory networks, thus having profound effect on higher cognitive and emotional functions such as learning and memory. In this study we have studied the effect of cannabinoid agonists on the potassium depolarization-evoked [(3)H]GABA release from hippocampal synaptosomes in the wild-type (WT) and cannabinoid 1 receptor (CB(1)R)-null mutant mice. All tested cannabinoid agonists (WIN55,212-2, CP55,940, HU-210, 2-arachidonoyl-glycerol, 2-AG; delta-9-tetra-hydrocannabinol, THC) inhibited [(3)H]GABA release in WT mice with the following rank order of agonist potency: HU-210>CP55,490>WIN55,212-2>2-AG>THC. By contrast, 2-AG and THC displayed the greatest efficacy eliciting almost complete inhibition of evoked [(3)H]GABA efflux, whereas the maximal inhibition obtained by HU-210, CP55,490, and WIN55,212-2 were less, eliciting not more than 40% inhibition. The inhibitory effect of WIN55,212-2, THC and 2-AG on evoked [(3)H]GABA efflux was antagonized by the CB(1) receptor inverse agonist AM251 (0.5 μM) in the WT mice. In the CB(1)R knockout mice the inhibitory effects of all three agonists were attenuated. In these mice, AM251 did not antagonize, but further reduced the [(3)H]GABA release in the presence of the synthetic agonist WIN55,212-2. By contrast, the concentration-dependent inhibitory effects of THC and 2-AG were partially antagonized by AM251 in the absence of CB(1) receptors. Finally, the inhibition of evoked [(3)H]GABA efflux by THC and 2-AG was also partially attenuated by AM630 (1 μM), the CB(2) receptor-selective antagonist, both in WT and CB(1) knockout mice. Our data prove the involvement of CB(1) receptors in the effect of exo- and endocannabinoids on GABA efflux from hippocampal nerve terminals. In addition, in the effect of the exocannabinoid THC and the endocannabinoid 2-AG, non-CB(1), probably CB(2)-like receptors are also involved.     

Fruit fly behavior in response to chemosensory signals

An important question in contemporary sensory neuroscience is how animals perceive their environment and make appropriate behavioral choices based on chemical perceptions. The fruit fly Drosophila melanogaster exhibits robust tastant and odor-evoked behaviors. Understanding how the gustatory and olfactory systems support the perception of these contact and volatile chemicals and translate them into appropriate attraction or avoidance behaviors has made an unprecedented contribution to our knowledge of the organization of chemosensory systems. In this review, I begin by describing the receptors and signaling mechanisms of the Drosophila gustatory and olfactory systems and then highlight their involvement in the control of simple and complex behaviors. The topics addressed include feeding behavior, learning and memory, navigation behavior, neuropeptide modulation of chemosensory behavior, and I conclude with a discussion of recent work that provides insight into pheromone signaling pathways.     

Genetic polymorphisms in the DNA repair gene XRCC1 and susceptibility to glioma in a Han population in northeastern China: A case–control study

Background

Several single nucleotide polymorphisms (SNPs) in the X-ray cross-complementing group 1 (XRCC1) gene have been shown to influence DNA repair and to modify cancer susceptibility. To investigate the role of these loci further, we examined the association of three XRCC1 polymorphisms with the risk of gliomas in a Han population in northeastern China.

Methods

Using a PCR–RFLP method, XRCC1 Arg194Trp, Arg280His and Arg399Gln were genotyped in 624 glioma patients and 580 healthy controls.

Results

Significant differences in the distribution of the Arg399Gln allele were detected between glioma patients and healthy controls by a logistic regression analysis (OR = 1.35, 95%CI 1.17–1.68, P = 0.001). Our data also revealed that the Arg399Gln variant (allele A) carriers had an increased glioma risk compared to the wild-type (allele G) homozygous carriers (OR = 1.40, 95%CI 1.12–1.76, P = 0.003).

Conclusions

These results suggest that the XRCC1 Arg399Gln might influence the risk of developing glioma in a Han population in northeastern Chinese.     

Differential leaf expansion can enable hydraulic acclimation to sun and shade

Although leaf size is one of the most responsive plant traits to environmental change, the functional benefits of large versus small leaves remain unclear. We hypothesized that modification of leaf size within species resulting from differences in irradiance can allow leaves to acclimate to different photosynthetic or evaporative conditions while maintaining an efficient balance between hydraulic supply (vein density) and evaporative demand. To test this, we compared the function and anatomy of leaf hydraulic systems in the leaves of a woody angiosperm (Toona ciliata M. Roem.) grown under high and low irradiance in controlled conditions. Our results confirm that in this species, differential leaf expansion regulates the density of veins and stomata such that leaf hydraulic conductance and stomatal conductance remain proportional. A broader sample of field-grown tree species suggested that differences in leaf venation and stomatal traits induced by sun and shade were not regulated by leaf size in all cases. Our results, however, suggest that leaf size plasticity can provide an efficient way for plants to acclimate hydraulic and stomatal conductances to the contrasting evaporative conditions of sun and shade.     

Impaired hepatic function and central dopaminergic denervation in a rodent model of Parkinson's disease: A self-perpetuating crosstalk?

In Parkinson's disease (PD), aside from the central lesion, involvement of visceral organs has been proposed as part of the complex clinical picture of the disease. The issue is still poorly understood and relatively unexplored. In this study we used a classic rodent model of nigrostriatal degeneration, induced by the intrastriatal injection of 6-hydroxydopamine (6-OHDA), to investigate whether and how a PD-like central dopaminergic denervation may influence hepatic functions. Rats received an intrastriatal injection of 6-OHDA or saline (sham), and blood, cerebrospinal fluid, liver and brain samples were obtained for up to 8 weeks after surgery. Specimens were analyzed for changes in cytokine and thyroid hormone levels, as well as liver mitochondrial alterations. Hepatic mitochondria isolated from animals bearing extended nigrostriatal lesion displayed increased ROS production, while membrane potential (ΔΨ) and ATP production were significantly decreased. Reduced ATP production correlated with nigral neuronal loss. Thyroid hormone levels were significantly increased in serum of PD rats compared to sham animals while steady expression of selected cytokines was detected in all groups. Hepatic enzyme functions were comparable in all animals. Our study indicates for the first time that in a rodent model of PD, hepatic mitochondria dysfunctions arise as a consequence of nigrostriatal degeneration, and that thyroid hormone represents a key interface in this CNS-liver interaction. Liver plays a fundamental detoxifying function and a better understanding of PD-related hepatic mitochondrial alterations, which might further promote neurodegeneration, may represent an important step for the development of novel therapeutic strategies.     

Detection and identification of ‘Candidatus Phytoplasma asteris’ in Brassica rapa subsp. pekinensis in Poland

Severe growth abnormalities, including leaf yellowing, sprout proliferation and flower virescence and phyllody, were found on Brassica rapa subsp. pekinensis plants in Poland. The presence of phytoplasma in naturally infected plants was demonstrated by polymerase chain reaction assay employing phytoplasma universal P1/P7 followed by R16F2n/R16R2 primer pairs. The detected phytoplasma was identified using restriction fragment length polymorphism analysis (RFLP) of the 16S rRNA gene fragment with AluI, HhaI, MseI and RsaI endonucleases. After enzymatic digestion, all tested samples showed restriction pattern similar to that of ‘Candidatus phytoplasma asteris’. Nested PCR‐amplified products, obtained with primers R16F2n/R16R2, were sequenced. Sequences of the 16S rDNA gene fragment of analysed phytoplasma isolates were nearly identical. They revealed high nucleotide sequence identity (>98%) with corresponding sequences of other phytoplasma isolates from subgroup 16SrI‐B, and they were classified as members of ‘Candidatus phytoplasma asteris’. This is the first report of the natural occurrence of phytoplasma‐associated disease in plants of Chinese cabbage.     

Virus–vector Relationships,Host Range,Detection and Sequence Comparison of Chilli leaf curl virus Associated with an Epidemic of Leaf Curl Disease of Chilli in Jodhpur,India

An epidemic of chilli leaf curl disease was recorded in 2004 in Jodhpur, a major chilli‐growing area in Rajasthan, India. Several isolates were efficiently transmitted by the whitefly (Bemisia tabaci), all of which induced severe leaf curl symptoms in chilli. A single whitefly was capable of transmitting the virus, and eight or more whiteflies per plant resulted in 100% transmission. The minimum acquisition access period (AAP) and inoculation access period (IAP) were 180 and 60 min, respectively. The virus persisted in whiteflies for up to 5 days postacquisition. Of 25 species tested, the virus infected only five (Capsicum annuum, Carica papaya, Solanum lycopersicum, Nicotiana tabacum and N. benthamiana). The virus was identified as Chilli leaf curl virus (ChiLCV), which shared the closest sequence identity (96.1%) with an isolate of ChiLCV from potato in Pakistan and showed sequence diversity up to 12.3% among the ChiLCV isolates reported from India and Pakistan. A betasatellite was identified, which resembled most closely (97.3%) that of Tomato leaf curl Bangladesh betasatellite previously reported from chilli and tomato leaf curl in India. The betasatellite was very different from that reported from chilli leaf curl in Pakistan, indicating that different betasatellites are associated with chilli leaf curl in India and Pakistan. We describe here for the first time the virus–vector relationships and host range of ChiLCV.     

Isolation,cloning, and overexpression of vip3Aa gene isolated from a local Bacillus thuringiensis

Vegetative insecticidal protein (Vip) is a newly discovered family of toxin protein isolated from Bacillus thuringiensis (Bt). An 88.5-kDa Vip3Aa protein was secreted by a local strain of the bacterium during the vegetative growth phase. The full length of the coding region ‘2.3 kbp’ of the vip3Aa gene was isolated from plasmid DNA, cloned in pGEM-T vector and finally cloned in pQE-30 expression vector. Nucleotide sequence revealed 98% homology with that of the previously isolated genes. Expression of the vip3Aa in Escherichia coli was carried out and the expressed protein was detected in the concentrated supernatant, not in the pellet. This indicated that vip3Aa is secreted into the culture medium. Expressed protein was purified, blotted, and assayed against the cotton leaf worm Spodoptera littoralis. The LC₅₀ was found to be 142.4 µ/mL while the LC₅₀ was 90 ppm for the wild strain. These results suggest the use of either the isolated Bt strains or the expressed vip3Aa in an integrated pest management program against lepidopteran insect pests.