Tissue protection mediated by mitochondrial K+ channels

Two distinct K+ uniporters have been described in mitochondria, ATP-sensitive and Ca2+-activated. Both are capable of protecting tissues against ischemia and other forms of injury when active. These findings indicate a central role for mitochondrial K+ uptake in tissue protection. This review describes the characteristics of mitochondrial K+ uniport, physiological consequences of this transport, forms of tissue damage in which K+ channels are implicated and possible mechanisms through which protection occurs.     

Comparison of conventional PCR, quantitative PCR, bacteriological culture and the Warthin Starry technique to detect Leptospira spp. in kidney and liver samples from naturally infected sheep from Brazil

Leptospirosis is an infectious disease of worldwide importance. The development of diagnostic techniques allows sick animals to be identified, reservoirs to be eliminated and the disease prevented and controlled. The present study aimed to compare different techniques for diagnosing leptospirosis in sheep. Samples of kidney, liver and blood were collected from 465 animals that originated from a slaughterhouse. The sera were analyzed by the Microscopic Agglutination Test (MAT), and kidney and liver samples of seropositive animals were analyzed using four techniques: bacteriological culture, the Warthin Starry (WS) technique, conventional PCR (cPCR), and quantitative PCR (qPCR). With the MAT, 21 animals were positive (4.5%) to serovars Hardjo (n=12), Hebdomadis (n=5), Sentot (n=2), Wolfii (n=1) and Shermani (n=1). Titers were 100 (n=10), 200 (n=2), 400 (n=6) and 1600 (n=3). No animal was positive by bacteriological culture; four animals were positive by the WS technique in kidney samples; six animals were positive by cPCR in kidney samples; and 11 animals were positive by qPCR, eight of which in kidney samples and three in liver. The bacterial quantification revealed a median of 4.3 bacteria/μL in liver samples and 36.6 bacteria/μL in kidney samples. qPCR presented the highest sensitivity among the techniques, followed by cPCR, the WS technique and bacteriological culture. These results indicate that sheep can carry leptospires of the Sejroe serogroup, and demonstrate the efficiency of quantitative PCR to detect Leptospira spp. in tissue samples.     

Seropositivity for Coxiella burnetii in suspected patients with dengue in São Paulo state,Brazil

Q fever and brucellosis are zoonoses that cause fever and other systemic clinical signs in humans; their occurrences are neglected and the differential diagnosis for some diseases is disregarded. This study aimed to investigate the seropositivity for Coxiella burnetii and Brucella spp. antibodies in patients suspected of dengue from 38 municipalities in the state of São Paulo, Brazil. The samples (n = 604) were obtained by convenience from the Adolfo Lutz Institute serum bank. Sera were subjected to an indirect immunofluorescence assay (IFA) using in-house and commercial diagnostic protocols to evaluate C. burnetii positivity. For Brucella spp., sera were subjected to rapid plate serum agglutination with buffered acidified antigen (AAT), slow tube serum agglutination (SAL), and 2-mercaptoethanol (2-ME) techniques. Associations and statistical inferences of the results were performed by logistic regression according to the clinical and demographic variables collected from the patients. Statistical analyses were performed using Statistical Analysis Software (SAS) and associations were considered when p value was <0.05. In all, 129 patients showed positive results for Q fever, indicating a seropositivity of 21.4% (95% CI 18.15–24.85). Patients with 14–20 days of symptoms had 2.12 (95% CI 1.34–3.35) times more chances of being seropositive for Q fever than patients with 7–13 days, and patients with 21–27 days of fever had 2.62 (95% CI 1.27–5.41) times more chances of being seropositive for Q fever than patients with 7–13 days. For the other variables analyzed, there were no significant associations between the groups. No positivity for brucellosis was observed. This is the most comprehensive study of people seropositive for Q fever in São Paulo state and provides additional data for the medical community in Brazil. It is suggested that Q fever may be an important differential diagnosis of febrile illnesses in the region, demanding the government’s attention and investment in health.     

Modulation of Mouse Embryonic Stem Cell Proliferation and Neural Differentiation by the P2X7 Receptor

Background

Novel developmental functions have been attributed to the P2X7 receptor (P2X7R) including proliferation stimulation and neural differentiation. Mouse embryonic stem cells (ESC), induced with retinoic acid to neural differentiation, closely assemble processes occurring during neuroectodermal development of the early embryo.

Principal Findings

P2X7R expression together with the pluripotency marker Oct-4 was highest in undifferentiated ESC. In undifferentiated cells, the P2X7R agonist Bz-ATP accelerated cell cycle entry, which was blocked by the specific P2X7R inhibitor KN-62. ESC induced to neural differentiation with retinoic acid, reduced Oct-4 and P2X7R expression. P2X7R receptor-promoted intracellular calcium fluxes were obtained at lower Bz-ATP ligand concentrations in undifferentiated and in neural-differentiated cells compared to other studies. The presence of KN-62 led to increased number of cells expressing SSEA-1, Dcx and β3-tubulin, as well as the number of SSEA-1 and β3-tubulin-double-positive cells confirming that onset of neuroectodermal differentiation and neuronal fate determination depends on suppression of P2X7R activity. Moreover, an increase in the number of Ki-67 positive cells in conditions of P2X7R inhibition indicates rescue of progenitors into the cell cycle, augmenting the number of neuroblasts and consequently neurogenesis.

Conclusions

In embryonic cells, P2X7R expression and activity is upregulated, maintaining proliferation, while upon induction to neural differentiation P2X7 receptor expression and activity needs to be suppressed.     

Neuronal differentiation involves a shift from glucose oxidation to fermentation

Energy metabolism in the adult brain consumes large quantities of glucose, but little is known to date regarding how glucose metabolism changes during neuronal differentiation, a process that is highly demanding energetically. We studied changes in glucose metabolism during neuronal differentiation of P19 mouse embryonal carcinoma cells, E14Tg2A embryonic stem cells as well as during brain development of BLC57 mice. In all these models, we find that neurogenesis is accompanied by a shift from oxidative to fermentative glucose metabolism. This shift is accompanied by both a decrease in mitochondrial enzymatic activities and mitochondrial uncoupling. In keeping with this finding, we also observe that differentiation does not require oxidative metabolism, as indicated by experiments demonstrating that the process is preserved in cells treated with the ATP synthase inhibitor oligomycin. Overall, we provide evidence that neuronal differentiation involves a shift from oxidative to fermentative metabolism, and that oxidative phosphorylation is not essential for this process.