Decreased GABA receptor in the cerebral cortex of epileptic rats: effect of Bacopa monnieri and Bacoside-A

Abstact

Background

Gamma amino butyric acid (GABA), the principal inhibitory neurotransmitter in the cerebral cortex, maintains the inhibitory tones that counter balances neuronal excitation. When this balance is perturbed, seizures may ensue.

Methods

In the present study, alterations of the general GABA, GABA_A and GABA_B receptors in the cerebral cortex of the epileptic rat and the therapeutic application of Bacopa monnieri were investigated.

Results

Scatchard analysis of [³H]GABA, [³H]bicuculline and [³H]baclofen in the cerebral cortex of the epileptic rat showed significant decrease in B_max (P < 0.001) compared to control. Real Time PCR amplification of GABA receptor subunits such as GABA_Aά1, GABA_Aγ, GABA_Aδ, GABA_B and GAD where down regulated (P < 0.001) in epileptic rats. GABA_Aά5 subunit and Cyclic AMP responsible element binding protein were up regulated. Confocal imaging study confirmed the decreased GABA receptors in epileptic rats. Epileptic rats have deficit in radial arm and Y maze performance.

Conclusions

Bacopa monnieri and Bacoside-A treatment reverses epilepsy associated changes to near control suggesting that decreased GABA receptors in the cerebral cortex have an important role in epileptic occurrence; Bacopa monnieri and Bacoside-A have therapeutic application in epilepsy management.     

Intermediate Monocytes but Not TIE2-Expressing Monocytes Are a Sensitive Diagnostic Indicator for Colorectal Cancer

We have conducted the first study to determine the diagnostic potential of the CD14++CD16+ intermediate monocytes as compared to the pro-angiogenic subset of CD14++CD16+TIE2+ TIE2-expressing monocytes (TEMs) in cancer. These monocyte populations were investigated by flow cytometry in healthy volunteers (N?=?32) and in colorectal carcinoma patients with localized (N?=?24) or metastatic (N?=?37) disease. We further determined blood levels of cytokines associated with monocyte regulation. The results revealed the intermediate monocyte subset to be significantly elevated in colorectal cancer patients and to show the highest frequencies in localized disease. Multivariate regression analysis identified intermediate monocytes as a significant independent variable in cancer prediction. With a cut-off value at 0.37% (intermediate monocytes of total leukocytes) the diagnostic sensitivity and specificity ranged at 69% and 81%, respectively. In contrast, TEM levels were elevated in localized cancer but did not differ significantly between groups and none of the cytokines correlated with monocyte subpopulations. Of interest, in vitro analyses supported the observation that intermediate monocytes were more potently induced by primary as opposed to metastatic cancer cells which may relate to the immunosuppressive milieu established in the advanced stage of metastatic disease. In conclusion, intermediate monocytes as compared to TIE2-expressing monocytes are a more sensitive diagnostic indicator of colorectal cancer.     

Effects of melengestrol acetate and P.G. 600 on fertility in Rambouillet ewes outside the natural breeding season

The effects of melengestrol acetate (MGA) and P.G. 600 on ewe fertility outside the natural breeding season were evaluated. Rambouillet ewes were assigned to one of four groups: (1) control (C; n=92); (2) PG600 (n=86); (3) MGA (n=99); and (4) MGA+PG600 (n=92). A pellet with or without MGA (0.3mg/ewe/d) was fed at 0.15kg/ewe/d for 7d. On the last day of pellet feeding, ewes were given either saline or 5mL of P.G. 600 i.m. (400IU equine chorionic gonadotropin (eCG) and 200IU human chorionic gonadotropin (hCG)). Ultrasonography was performed between Days 20 and 25 of gestation for ewes that were mated during the first 6 d of the breeding period from the MGA (n=15) and MGA+PG600 (n=8) groups, and the number of luteal structures and embryos were counted. During the first 6d of the breeding period, MGA increased (P<0.05) the percentage of ewes that mated and conceived when compared to C and PG600 (24.2% vs. 3.3% and 10.5%, respectively). Relative to MGA, the mean (+/-S.E.M.) number of luteal structures per ewe was enhanced (P<0.03) in MGA+PG600 (1.53+/-0.13 vs. 2.38+/-0.42, respectively), however as pregnancy progressed, the number of embryos (1.5+/-0.13 vs. 1.8+/-0.16, respectively) and lambs born (1.3+/-0.15 vs. 1.5+/-0.27, respectively) did not differ. Treatment with MGA reduced (P<0.01) the interval from ram introduction to lambing relative to groups that did not receive MGA (168+/-0.8d vs. 171+/-0.6d, respectively). In conclusion, treatment with MGA increased the percentage of ewes conceiving early in the breeding period. Although P.G. 600 increased the number of luteal structures present per ewe, it did not significantly enhance ewe prolificacy.     

Extracellular degradation of phenol by the cyanobacterium Synechococcus PCC 7002

Investigations of the unicellular marine cyanobacterium Synechococcus PCC 7002 revealed its ability to metabolize phenol under non-photosynthetic conditions up to 100 mg L^–1. Under continuous light, photoautotrophic growth was reduced only slightly in the presence of this phenol concentration, but no transformation was observed. However neither under photoautotrophic nor heterotrophic conditions were the cells able to use phenol for growth. During the degradation of phenol in the dark cis,cis-muconic acid was produced as the major product, which was identified by gas chromatography/mass spectrometry. This result was confirmed by an identical absorption spectrum and an identical retention time in high performance liquid chromatographic analysis with authentic muconic acid as standard. This provides the first record for an ortho-fission of a phenolic substance by cyanobacteria. Further investigations of the breakdown mechanism of phenol have shown that the transformation is an extracellular process inhibited by heat, proteases and metal ions and is probably catalyzed by a protein.     

Methylotrophic bacteria on the surfaces of field-grown sunflower plants: a biogeographic perspective

Plant-associated methylobacteria of the genus Methylobacterium colonize the foliage and roots of embryophytes, living on the volatile compound methanol emitted from the cells of their host organism. In this study we analyzed these surface-dwelling pink-pigmented epiphytes in three contrasting habitats of field-grown sunflower plants (Helianthus annuus). Using the methanol–ammonium salts agar surface impression method and a polymerase chain reaction (PCR)-based assay, we document the occurrence and characterize the composition of the methylobacteria in these epiphytic habitats. In both the sun-exposed phylloplane (yellow ligulate florets; green leaves) and the moist, dark rhizoplane pink-pigmented methylobacteria were detected that are assigned to the taxa M. mesophilicum, M. extorquens, M. radiotolerans and M. sp. (un-identifiable by our methods). Considerable differences in relative species compositions were found. These data are discussed with respect to a biogeographic model of the plant surface and microbial population dynamics on leaves. In addition, methylobacteria were analyzed by microscopic techniques. We document that in sedentary colonies extracellular polymers are secreted. However, flagella, which were observed in single cells maintained in liquid cultures, are absent in these bacterial aggregates.     

Persistent nuclear ribosomal DNA sequence polymorphism in the Amelanchier agamic complex (Rosaceae)

Individual plants of several Amelanchier taxa contain many polymorphic nucleotide sites in the internal transcribed spacers (ITS) of nuclear ribosomal DNA (nrDNA). This polymorphism is unusual because it is not recent in origin and thus has resisted homogenization by concerted evolution. Amelanchier ITS sequence polymorphism is hypothesized to be the result of gene flow between two major North American clades resolved by phylogenetic analysis of ITS sequences. Western North American species plus A. humilis and A. sanguinea of eastern North America form one clade (A), and the remaining eastern North American Amelanchier make up clade B. Five eastern North American taxa are polymorphic at many of the nucleotide sites where clades A and B have diverged and are thought to be of hybrid origin, with A. humilis or A. sanguinea as one parent and various members of clade B as the other parent. Morphological evidence suggests that A. humilis is one of the parents of one of the polymorphic taxa, a microspecies that we refer to informally as A. "erecta." Sequences of 21 cloned copies of the ITS1- 5.8S gene-ITS2 region from one A. "erecta" individual are identical to A. humilis sequence or to the clade B consensus sequence, or they are apparent recombinants of A. humilis and clade B ITS repeats. Amelanchier "erecta" and another polymorphic taxon are suspected to be relatively old because both grow several hundred kilometers beyond the range of one of their parents. ITS sequence polymorphisms have apparently persisted in these two taxa perhaps because of polyploidy and/or agamospermy (asexual seed production), which are prevalent in the genus.      

Canopy-scale δ13C of photosynthetic and respiratory CO2 fluxes: observations in forest biomes across the United States

The δ¹³C values of atmospheric carbon dioxide (CO₂) can be used to partition global patterns of CO₂ source/sink relationships among terrestrial and oceanic ecosystems using the inversion technique. This approach is very sensitive to estimates of photosynthetic ¹³C discrimination by terrestrial vegetation (Δ_A), and depends on δ¹³C values of respired CO₂ fluxes (δ¹³C_R). Here we show that by combining two independent data streams – the stable isotope ratios of atmospheric CO₂ and eddy‐covariance CO₂ flux measurements – canopy scale estimates of Δ_A can be successfully derived in terrestrial ecosystems. We also present the first weekly dataset of seasonal variations in δ¹³C_R from dominant forest ecosystems in the United States between 2001 and 2003. Our observations indicate considerable summer‐time variation in the weekly value of δ¹³C_R within coniferous forests (4.0‰ and 5.4‰ at Wind River Canopy Crane Research Facility and Howland Forest, respectively, between May and September). The monthly mean values of δ¹³C_R showed a smaller range (2–3‰), which appeared to significantly correlate with soil water availability. Values of δ¹³C_R were less variable during the growing season at the deciduous forest (Harvard Forest). We suggest that the negative correlation between δ¹³C_R and soil moisture content observed in the two coniferous forests should represent a general ecosystem response to the changes in the distribution of water resources because of climate change. Shifts in δ¹³C_R and Δ_A could be of sufficient magnitude globally to impact partitioning calculations of CO₂ sinks between oceanic and terrestrial compartments.     

Response of plant species richness and primary productivity in shrublands along a north–south gradient in Europe to seven years of experimental warming and drought: reductions in primary productivity in the heat and drought year of 2003

We used a nonintrusive field experiment carried out at six sites – Wales (UK), Denmark (DK), the Netherlands (NL), Hungary (HU), Sardinia (Italy – IT), and Catalonia (Spain – SP) – along a climatic and latitudinal gradient to examine the response of plant species richness and primary productivity to warming and drought in shrubland ecosystems. The warming treatment raised the plot daily temperature by ca. 1 °C, while the drought treatment led to a reduction in soil moisture at the peak of the growing season that ranged from 26% at the SP site to 82% in the NL site. During the 7 years the experiment lasted (1999–2005), we used the pin‐point method to measure the species composition of plant communities and plant biomass, litterfall, and shoot growth of the dominant plant species at each site. A significantly lower increase in the number of species pin‐pointed per transect was found in the drought plots at the SP site, where the plant community was still in a process of recovering from a forest fire in 1994. No changes in species richness were found at the other sites, which were at a more mature and stable state of succession and, thus less liable to recruitment of new species. The relationship between annual biomass accumulation and temperature of the growing season was positive at the coldest site and negative at the warmest site. The warming treatment tended to increase the aboveground net primary productivity (ANPP) at the northern sites. The relationship between annual biomass accumulation and soil moisture during the growing season was not significant at the wettest sites, but was positive at the driest sites. The drought treatment tended to reduce the ANPP in the NL, HU, IT, and SP sites. The responses to warming were very strongly related to the Gaussen aridity index (stronger responses the lower the aridity), whereas the responses to drought were not. Changes in the annual aboveground biomass accumulation, litterfall, and, thus, the ANPP, mirrored the interannual variation in climate conditions: the most outstanding change was a decrease in biomass accumulation and an increase in litterfall at most sites during the abnormally hot year of 2003. Species richness also tended to decrease in 2003 at all sites except the cold and wet UK site. Species‐specific responses to warming were found in shoot growth: at the SP site, Globularia alypum was not affected, while the other dominant species, Erica multiflora, grew 30% more; at the UK site, Calluna vulgaris tended to grow more in the warming plots, while Empetrum nigrum tended to grow less. Drought treatment decreased plant growth in several studied species, although there were some species such as Pinus halepensis at the SP site or C. vulgaris at the UK site that were not affected. The magnitude of responses to warming and drought thus depended greatly on the differences between sites, years, and species and these multiple plant responses may be expected to have consequences at ecosystem and community level. Decreases in biodiversity and the increase in E. multiflora growth at the SP site as a response to warming challenge the assumption that sensitivity to warming may be less well developed at more southerly latitudes; likewise, the fact that one of the studied shrublands presented negative ANPP as a response to the 2003 heat wave also challenges the hypothesis that future climate warming will lead to an enhancement of plant growth and carbon sequestration in temperate ecosystems. Extreme events may thus change the general trend of increased productivity in response to warming in the colder sites.