Voltage‐dependent κ‐opioid modulation of action potential waveform‐elicited calcium currents in neurohypophysial terminals

Release of neurotransmitter is activated by the influx of calcium. Inhibition of Ca²⁺ channels results in less calcium influx into the terminals and presumably a reduction in transmitter release. In the neurohypophysis (NH), Ca²⁺ channel kinetics, and the associated Ca²⁺ influx, is primarily controlled by membrane voltage and can be modulated, in a voltage‐dependent manner, by G‐protein subunits interacting with voltage‐gated calcium channels (VGCCs). In this series of experiments we test whether the κ‐ and µ‐opioid inhibition of Ca²⁺ currents in NH terminals is voltage‐dependent. Voltage‐dependent relief of G‐protein inhibition of VGCC can be achieved with either a depolarizing square pre‐pulse or by action potential waveforms. Both protocols were tested in the presence and absence of opioid agonists targeting the κ‐ and µ‐receptors in neurohypophysial terminals. The κ‐opioid VGCC inhibition is relieved by such pre‐pulses, suggesting that this receptor is involved in a voltage‐dependent membrane delimited pathway. In contrast, µ‐opioid inhibition of VGCC is not relieved by such pre‐pulses, indicating a voltage‐independent diffusible second‐messenger signaling pathway. Furthermore, relief of κ‐opioid inhibition during a physiologic action potential (AP) burst stimulation indicates the possibility of activity‐dependent modulation in vivo. Differences in the facilitation of Ca²⁺ channels due to specific G‐protein modulation during a burst of APs may contribute to the fine‐tuning of Ca²⁺‐dependent neuropeptide release in other CNS terminals, as well. J. Cell. Physiol. 225: 223–232, 2010. © 2010 Wiley‐Liss, Inc.     

CXCL10 is the key ligand for CXCR3 on CD8+ effector T cells involved in immune surveillance of the lymphocytic choriomeningitis virus-infected central nervous system

IFN-gamma-inducible protein 10/CXCL10 is a chemokine associated with type 1 T cell responses, regulating the migration of activated T cells through binding to the CXCR3 receptor. Expression of both CXCL10 and CXCR3 are observed during immunopathological diseases of the CNS, and this receptor/ligand pair is thought to play a central role in regulating T cell-mediated inflammation in this organ site. In this report, we investigated the role of CXCL10 in regulating CD8(+) T cell-mediated inflammation in the virus-infected brain. This was done through analysis of CXCL10-deficient mice infected intracerebrally with lymphocytic choriomeningitis virus, which in normal immunocompetent mice induces a fatal CD8(+) T cell-mediated meningoencephalitis. We found that a normal antiviral CD8(+) T cell response was generated in CXCL10-deficient mice, and that lack of CXCL10 had no influence on the accumulation of mononuclear cells in the cerebrospinal fluid. However, analysis of the susceptibility of CXCL10-deficient mice to lymphocytic choriomeningitis virus-induced meningitis revealed that these mice just like CXCR3-deficient mice were partially resistant to this disease, whereas wild-type mice invariably died. Furthermore, despite marked up-regulation of the two remaining CXCR3 ligands: CXCL9 and 11, we found a reduced accumulation of CD8(+) T cells in the brain parenchyma around the time point when wild-type mice succumb as a result of CD8(+) T cell-mediated inflammation. Thus, taken together these results indicate a central role for CXCL10 in regulating the accumulation of effector T cells at sites of CNS inflammation, with no apparent compensatory effect of other CXCR3 ligands.     

The population genetics of Quechuas, the largest native South American group: autosomal sequences, SNPs, and microsatellites evidence high level of diversity

Elucidating the pattern of genetic diversity for non-European populations is necessary to make the benefits of human genetics research available to individuals from these groups. In the era of large human genomic initiatives, Native American populations have been neglected, in particular, the Quechua, the largest South Amerindian group settled along the Andes. We characterized the genetic diversity of a Quechua population in a global setting, using autosomal noncoding sequences (nine unlinked loci for a total of 16 kb), 351 unlinked SNPs and 678 microsatellites and tested predictions of the model of the evolution of Native Americans proposed by (Tarazona-Santos et al.: Am J Hum Genet 68 (2001) 1485-1496). European admixture is <5% and African ancestry is barely detectable in the studied population. The largest genetic distances were between African versus Quechua or Melanesian populations, which is concordant with the African origin of modern humans and the fact that South America was the last part of the world to be peopled. The diversity in the Quechua population is comparable with that of Eurasian populations, and the allele frequency spectrum based on resequencing data does not reflect a reduction in the proportion of rare alleles. Thus, the Quechua population is a large reservoir of common and rare genetic variants of South Amerindians. These results are consistent with and complement our evolutionary model of South Amerindians (Tarazona-Santos et al.: Am J Hum Genet 68 (2001) 1485-1496), proposed based on Y-chromosome data, which predicts high genomic diversity due to the high level of gene flow between Andean populations and their long-term effective population size.     

Low sequencing efforts bias analyses of shared taxa in microbial communities

The potential for comparing microbial community population structures has been greatly enhanced by developments in next generation sequencing methods that can generate hundreds of thousands to millions of reads in a single run. Conversely, many microbial community comparisons have been published with no more than 1,000 sequences per sample. These studies have presented data on levels of shared operational taxonomic units (OTUs) between communities. Due to lack of coverage, that approach might compromise the conclusions about microbial diversity and the degree of difference between environments. In this study, we present data from recent studies that highlight this problem. Also, we analyzed datasets of 16 rRNA sequences with small and high sequence coverage from different environments to demonstrate that the level of sequencing effort used for analyzing microbial communities biases the results. We randomly sampled pyrosequencing-generated 16S rRNA gene libraries with increasing sequence effort. Sequences were used to calculate Good's coverage, the percentage of shared OTUs, and phylogenetic distance measures. Our data showed that simple counts of presence/absence of taxonomic unities do not reflect the real similarity in membership and structure of the bacterial communities and that community comparisons based on phylogenetic tests provide a way to test statistically significant differences between two or more environments without need an exhaustive sampling effort.     

Length–weight relationships of four freshwater ornamental fish species from the Brazilian Negro River basin

The present work reports the length–weight relationships (LWR) for four ornamental fish species from the middle Negro River basin, Amazonas, Brazil. The r² value ranged from 0.810 to 0.941 and values of b varied from 2.346 to 3.442. These results represent the first reference on LWR for all four species, based on FishBase.     

Fine-scale spatial genetic structure of Dalbergia nigra (Fabaceae), a threatened and endemic tree of the Brazilian Atlantic Forest

The Atlantic Forest is one of the most diverse ecosystems in the world and considered a hotspot of biodiversity conservation. Dalbergia nigra (Fabaceae) is a tree endemic to the Brazilian Atlantic Forest, and has become threatened due to overexploitation of its valuable timber. In the present study, we analyzed the genetic diversity and fine-scale spatial genetic structure of D. nigra in an area of primary forest of a large reserve. All adult individuals (N = 112) were sampled in a 9.3 ha plot, and genotyped for microsatellite loci. Our results indicated high diversity with a mean of 8.6 alleles per locus, and expected heterozygosity equal to 0.74. The co-ancestry coefficients were significant for distances among trees up to 80 m. The Sp value was equal to 0.017 and indirect estimates of gene dispersal distances ranged from 89 to 144 m. No strong evidence of bottleneck or effects of human-disturbance was found. This study highlights that long-term efforts to protect a large area of Atlantic Forest have been effective towards maintaining the genetic diversity of D. nigra. The results of this study are important towards providing a guide for seed collection for ex-situ conservation and reforestation programmes of this threatened species.