Evaluation of the Performance of Information Theory-Based Methods and Cross-Correlation to Estimate the Functional Connectivity in Cortical Networks

Functional connectivity of in vitro neuronal networks was estimated by applying different statistical algorithms on data collected by Micro-Electrode Arrays (MEAs). First we tested these “connectivity methods” on neuronal network models at an increasing level of complexity and evaluated the performance in terms of ROC (Receiver Operating Characteristic) and PPC (Positive Precision Curve), a new defined complementary method specifically developed for functional links identification. Then, the algorithms better estimated the actual connectivity of the network models, were used to extract functional connectivity from cultured cortical networks coupled to MEAs. Among the proposed approaches, Transfer Entropy and Joint-Entropy showed the best results suggesting those methods as good candidates to extract functional links in actual neuronal networks from multi-site recordings.     

Causes of shear sensitivity of the toxic dinoflagellate Protoceratium reticulatum

Dinoflagellates have proven extremely difficult to culture because they are inhibited by low‐level shear forces. Specific growth rate of the toxic dinoflagellate Protoceratium reticulatum was greatly decreased compared with static control culture by intermittent exposure to a turbulent hydrodynamic environment with a bulk average shear rate that was as low as 0.3 s^?1. Hydrodynamic forces appeared to induce the production of reactive oxygen species (ROS) within the cells and this caused peroxidation of cellular lipids and ultimately cell damage. Exposure to damaging levels of shear rate correlated with the elevated level of lipoperoxides in the cells, but ROS levels measured directly by flow cytometry did not correlate with shear induced cell damage. This was apparently because the measured level of ROS could not distinguish between the ROS that are normally generated by photosynthesis and the additional ROS produced as a consequence of hydrodynamic shear forces. Continuously subjecting the cells to a bulk average shear rate value of about 0.3 s^?1 for 24‐h caused an elevation in the levels of chlorophyll a, peridinin and dinoxanthin, as the cells apparently attempted to counter the damaging effects of shear fields by producing pigments that are potential antioxidants. In static culture, limitation of carbon dioxide produced a small but measureable increase in ROS. The addition of ascorbic acid (0.1 mM) to the culture medium resulted in a significant protective effect on lipid peroxidation, allowing cells to grow under damaging levels of shear rates. This confirmed the use of antioxidant additives as an efficient strategy to counter the damaging effects of turbulence in photobioreactors where shear sensitive dinoflagellates are cultivated. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

Genetic demography of Antioquia (Colombia) and the Central Valley of Costa Rica

We report a comparative genetic characterization of two population isolates with parallel demographic histories: the Central Valley of Costa Rica (CVCR) and Antioquia (in northwest Colombia). The analysis of mtDNA, Y-chromosome and autosomal polymorphisms shows that Antioquia and the CVCR are genetically very similar, indicating that closely related parental populations founded these two isolates. In both populations, the male ancestry is predominantly European, whereas the female ancestry is mostly Amerind. In agreement with their isolation, the Amerindian mtDNA diversity of Antioquia and the CVCR is typical of ethnically-defined native populations and is markedly lower than in other Latin American populations. A comparison of linkage disequilibrium (LD) at 18 marker pairs in Antioquia and the CVCR shows that markers in LD in both populations are located at short genetic distances (相似文献   

Effects of pharmacological treatment and photoinactivation on the directional responses of an insect neuron

Soma-ipsilateral branches of the large segmental omega neuron of the phaneropterid bush cricket Ancistrura nigrovittata have smooth endings, which extend through most of the auditory neuropile. Correspondingly, it shows a broad frequency tuning. Large excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) are observed when recording from soma-ipsilateral branches. Stimulation from the soma-ipsilateral side leads to a strong excitation. Soma-contralateral branches have a strong, beaded appearance. IPSPs, which seem to be of soma-contralateral origin, can be recorded from these branches. Stimulation from the soma-contralateral side leads to a strong inhibition of the omega neuron. Soma-contralateral stimulation must be 30-40 dB more intense than soma-ipsilateral stimulation to evoke similar spike numbers in the omega neuron. The side-to-side difference is reduced to 10-15 dB after cutting the input from the soma-contralateral leg (tympanic nerve). The thresholds for eliciting IPSPs by soma-contralateral stimulation correspond roughly to excitatory thresholds of the mirror-image omega with the same stimuli. Pharmacological treatment with picrotoxin (PTX) or photoinactivation of the Lucifer Yellow filled mirror-image omega neuron reduces contralateral inhibition considerably and eliminates all visible IPSPs. Nevertheless, an additional contralateral inhibition survives both procedures and is only eliminated after cutting the soma-contralateral tympanic nerve. These results demonstrate that the mirror-image partners of the omega neuron mutually inhibit each other in bush crickets--as in crickets. This mutual inhibition is PTX-sensitive. At least one additional element exerts contralateral PTX-insensitive inhibition on the omega neuron.     

Trypanosoma cruzi (Kinetoplastida Trypanosomatidae): ecology of the transmission cycle in the wild environment of the Andean valley of Cochabamba, Bolivia

An active Trypanosoma cruzi transmission cycle maintained by wild rodents in the Andean valleys of Cochabamba Bolivia is described. Wild and domestic Triatoma infestans with 60% infection with T. cruzi were found and was evidenced in 47.5% (rodents) and 26.7% (marsupial) by parasitological and/or serologycal methods. Phyllotis ocilae and the marsupial species Thylamys elegans, are the most important reservoirs followed by Bolomys lactens and Akodon boliviensis. In spite of both genotypes (TCI and TCII) being prevalent in Bolivia, in our study area only T. cruzi I is being transmitted. Our data suggest that wild T. infestans and wild small mammals play an important role in the maintenance of the transmission cycle of T. cruzi. Furthermore, the finding of high prevalence of T. cruzi infection in wild T. infestans point to the risk of the dispersion of Chagas' disease.     

Redox state and carbonic anhydrase isozyme IX expression in human renal cell carcinoma: biochemical and morphological investigations

Clear renal cell carcinomas (RCC) frequently express carbonic anydrase IX (CA IX) because of non-functional mutation of von Hippel Lindau (VHL) tumor suppressor gene. CA IX is a tumor-associated transmembrane antigen, which catalyzes the extracellular, reversible hydration of carbon dioxide to bicarbonate and proton and thereby contributes to acidification of extracellular milieu. Extracellular acidic pH facilitates tumor growth and progression. CA IX expression is upregulated by Hypoxia Inducible Factor-1 (HIF-1), which is negatively controlled by oxygen via wild type VHL protein and is also regulated by the cell redox state. We investigated the immunohistochemical pattern of distribution of CA IX in a small series (14 cases) of RCCs. CA IX expression was matched with the redox state of RCC, stratifying our series in relation to clinical and histopathological parameters, such as Fuhrman grade, staging, proliferation markers expression, and particularly, the presence of necrosis. Our results show for the first time the existence of a perivascular pattern of CA IX distribution in RCC. We also found a significant relationship between CA IX expression and the presence of necrosis. Tumors with higher CA IX expression exhibited higher degree of necrosis (p < 0.05). Notably, an almost significant relationship between the redox state and CA IX expression was detected in RCC patients with 5 years disease-free survival, most of them showing organ-confined disease. Tumors with lower redox state showed an algebraically higher degree of CA IX expression. On the contrary, tumors with higher redox state exhibited an algebraically lower CA IX expression (p = 0.057). The observed relationship of CA IX expression and necrosis suggests a role for CA IX in RCC. Further investigations are necessary to further establish the role of the redox state in regulation of CA IX expression in RCC.     

Genetic association between bovine NOD2 polymorphisms and infection by Mycobacterium avium subsp. paratuberculosis in Holstein‐Friesian cattle

Nucleotide‐Binding Oligomerization Domain 2 (NOD2) has been reported to be a candidate gene for Mycobacterium avium subsp. paratuberculosis (MAP) infection in a Bos taurus × Bos indicus mixed breed based on a genetic association with the c.2197T>C single nucleotide polymorphism (SNP). Nevertheless, this SNP has also been reported to be monomorphic in the B. taurus species. In the present work, 18 SNPs spanning the bovine NOD2 gene have been analysed in a genetic association study of two independent populations of Holstein‐Friesian cattle. We found that the C allele of SNP c.*1908C>T, located in the 3′‐UTR region of the gene, is significantly more frequent in infected animals than in healthy ones, which supports the idea that the bovine NOD2 gene plays a role in susceptibility to MAP infection. However, in silico analyses of the NOD2 nucleotide sequence did not yield definitive data about a possible direct effect of SNP c.*1908C>T on susceptibility to infection and led us to consider its linkage disequilibrium with the causative variant. A more exhaustive genetic association study including all putative, functional SNPs from this gene and subsequent functional analyses needs to be conducted to achieve a more complete understanding of how different variants of NOD2 may affect susceptibility to MAP infection in cattle.     

The Genetic Factors Altered in Homozygous abo Stocks of DROSOPHILA MELANOGASTER

Females homozygous for the maternal-effect mutation abo (2-44.0) produce a large fraction of eggs which arrest during embryogenesis. Increasing doses of defined heterochromatic regions inherited by offspring of abo mothers from their fathers function zygotically to bring about a partial rescue of the abo-induced embryonic lethality. Another property of the abo mutation is that the severity of the maternal effect decreases when an abo stock is maintained in homozygous condition for a number of generations. Here, we show that the factors which change in homozygous abo stocks to result in the decrease in maternally induced embryonic lethality, act zygotically, dominantly and additively. More importantly, we show that the X and second chromosomes, but not the Y and third chromosomes, derived from homozygous abo stocks are, when inherited from males, more effective in promoting zygotic rescue of the abo-induced lethality than are the equivalent chromosomes derived from an abo stock maintained in heterozygous condition. The chromosomal locations of the factors maintained in the homozygous condition. The chromosomal locations of the factors altered in homozygous stock, as well as their behavior, strongly suggest that the same heterochromatic elements that are responsible for rescuing embryos from the abo-induced maternal effect are altered in homozygous abo flies in such a way that the maternal effect itself is less severe.     

Translation of Sindbis virus 26S mRNA does not require intact eukariotic initiation factor 4G

The infection of baby hamster kidney (BHK) cells by Sindbis virus gives rise to a drastic inhibition of cellular translation, while under these conditions the synthesis of viral structural proteins directed by the subgenomic 26S mRNA takes place efficiently. Here, the requirement for intact initiation factor eIF4G for the translation of this subgenomic mRNA has been examined. To this end, SV replicons that contain the protease of human immunodeficiency virus type 1 (HIV-1) or the poliovirus 2A(pro) replacing the sequences of SV glycoproteins have been constructed. BHK cells electroporated with the different RNAs synthesize protein C and the corresponding protease at late times. Notably, the proteolysis of eIF4G by both proteases has little effect on the translation of the 26S mRNA. In addition, recombinant viable SVs were engineered that encode HIV-1 PR or poliovirus 2A protease under the control of a duplicated late promoter. Viral protein synthesis at late times of infection by the recombinant viruses is slightly affected in BHK cells that contain proteolysed eIF4G. The translatability of SV genomic 49S mRNA was assayed in BHK cells infected with a recombinant virus that synthesizes luciferase and transfected with a replicon that expresses poliovirus 2Apro. Under conditions where eIF4G has been hydrolysed significantly the translation of genomic SV RNA was deeply inhibited. These findings indicate a different requirement for intact eIF4G in the translation of genomic and subgenomic SV mRNAs. Finally, the translation of the reporter gene that encodes green fluorescent protein, placed under the control of a second duplicate late promoter, is also resistant to the cleavage of eIF4G. In conclusion, despite the presence of a cap structure in the 5' end of the subgenomic SV mRNA, intact eIF4G is not necessary for its translation.     

The acute systemic toxicity of thallium in rats produces oxidative stress: attenuation by metallothionein and Prussian blue

BioMetals - Thallium (TI) is one of the most toxic heavy metals. Human exposure to Tl occurs through contaminated drinking water and from there to food, a threat to health. Recently, environmental...