Role of the wbt locus of Francisella tularensis in lipopolysaccharide O-antigen biogenesis and pathogenicity

Francisella tularensis is a highly infectious bacterial pathogen, responsible for the zoonotic disease tularemia. We screened a bank of transposon insertion mutants of F. tularensis subsp. holarctica LVS for colony morphology alterations and selected a mutant with a transposon insertion in wbtA, the first gene of the predicted lipopolysaccharide O-antigen gene cluster. Inactivation of wbtA led to the complete loss of O antigen, conferred serum sensitivity, impaired intracellular replication, and severely attenuated virulence in the mouse model. Notably, this mutant afforded protection against a challenge against virulent LVS.     

Expression of the Ku70 subunit (XRCC6) and protection from low dose ionizing radiation during zebrafish embryogenesis

The Ku70 protein, a product of the XRCC6 gene, is a component of the nonhomologous end-joining (NHEJ) pathway of DNA repair, which protects cells from the effects of radiation-induced DNA damage. Although the spatial expression of Ku70 during vertebrate embryogenesis has not been described, DNA repair proteins are generally considered to be "housekeeping" genes, which are required for radioprotection in all cells. Here, we report the cloning and characterization of the zebrafish Ku70 ortholog. In situ hybridization and RT-PCR analyses demonstrate that Ku70 mRNA is maternally provided and expressed uniformly among embryonic blastomeres. Later during embryogenesis, zygotically transcribed Ku70 mRNA specifically accumulates in neural tissue, including the retina and proliferative regions of the developing brain. In the absence of genotoxic stress, morpholino-mediated knockdown of Ku70 expression does not affect zebrafish embryogenesis. However, exposure of Ku70 morpholino-injected embryos to low doses of ionizing radiation leads to marked cell death throughout the developing brain, spinal cord, and tail. These results suggest that Ku70 protein plays a crucial role in protecting the developing nervous system from radiation-induced DNA damage during embryogenesis.     

Acute systemic inflammation induces central mitochondrial damage and mnesic deficit in adult Swiss mice

The aim of this study was to investigate how the brain is affected during systemic inflammation. For this purpose, Swiss mice were challenged with a single intraperitoneal dose of lipopolysaccharide (LPS; 250microg/mouse) to mimic aspects of systemic infection. Spatial learning in Y-maze test demonstrated a differential learning profile during the training test between control and LPS-treated mice, with an alteration in the latter group. We show that systemic LPS-induced inflammation and oxidative injury as assessed by reactive oxygen species (ROS) and nitrites/nitrates (NOx) production associated with reduced glutathione (GSH) depletion, cyclooxygenase-2 (COX-2) expression, and lipid peroxidation. LPS also induced a loss in mitochondrial integrity as shown by a significant decrease in membrane potential and impairment in mitochondrial redox activity. Thus, peripheral inflammation by producing brain inflammation and oxidative injury causes mnesic deficits. It remains to determine whether such events can induce neuronal dysfunction/degeneration and, with time, lead to cholinergic deficiency, amyloid deposits and cognitive impairments as they occur in Alzheimer's disease.     

Citicoline is not protective in experimental models of Huntington's disease

We have evaluated the neuroprotective effects of citicoline in relevant phenotypic models of Huntington's disease induced by either the mitochondrial inhibitor 3-nitropropionic acid or the N-methyl-d-aspartate agonist quinolinic acid, which, respectively, reproduce the metabolic defect or the excitotoxicity seen in the disease. We found that citicoline failed to reverse behavioural and histological alterations induced by both neurotoxins. In addition, citicoline did not reduce PC12 cell death induced by the expression of an N-terminal fragment of mutated Huntingtin. Altogether, our results suggest that citicoline is not a potential therapeutic agent for the treatment of Huntington's disease.     

The importance of controls in immunohistochemistry: how to validate an antibody, from research to diagnosis

The specificity of an immunohistochemical reaction is guaranteed by two sets of controls. Positive controls verify the specificity of the primary antibody and demonstrate that it binds only to the protein which was used as an immunogen. Negative controls ensure that the labelling technique is specific and that the primary antibody is responsible for generation of the immunostaining. In fact, the production of a labelling may also be related to cross reactivity or to non-specific physical or chemical interactions. This paper reviews the characteristics of various epitopes and antibodies, describes different strategies which prove the specificity of the immunohistochemical reaction in research or diagnostic pathology and point towards the essential information which should be reported in a paper.     

The excess in 2-5 mm follicles seen at ovarian ultrasonography is tightly associated to the follicular arrest of the polycystic ovary syndrome

BACKGROUND: We previously hypothesized that the excess of 2–5 mmfollicles seen at ovarian ultrasonography might be involvedin the follicular arrest (FA) of polycystic ovary syndrome (PCOS),independently from the main putative contributors of FA, namelyhyperandrogenism and hyperinsulinism. METHODS: A multivariate statistical analysis was applied retrospectivelyto clinical, biological and ultrasound data that were consecutivelycollected during 5 years in 457 patients with polycystic ovariesand in 188 age-matched non-hyperandrogenic and regularly cyclingcontrols without PCO at ultrasound. RESULTS: Stepwise discriminant analysis indicated that in PCOS the 2–5 mmfollicle number (FN) gave the strongest correlation to severityof the FA, followed by age and then by fasting insulin level.The other variables [waist circumference (WC), 6–9 mmFN, serum testosterone, FSH, LH and ovarian area] were rejectedby the analysis. Multiple linear regression indicated a significantand independent negative relationship between the 2–5and 6–9 mm FN in the PCOS (r = – 0.186, P <0.01) and control groups (r = – 0.281, P < 0.01). InPCOS only, the 6–9 mm FN was negatively and independentlyrelated to the WC (r = – 0.108, P < 0.05). CONCLUSIONS: The size of the 2–5 mm follicle pool is an independentand important contributor to the FA of PCOS. This result couldbe explained by an exaggerated physiological inhibitory effectfrom this pool on the terminal follicle growth. The metabolicderangement of PCOS that also contributes to the FA would actthrough a different mechanism.     

13q deletions in B-cell lymphoproliferative disorders: frequent association with translocation

The 13q14 deletion is the most frequent abnormality in chronic lymphocytic leukemias/small lymphocytic lymphomas, and this early rearrangement is observed from the start of the disease. The systematic use of a panel of interphase fluorescence in situ hybridization (FISH) may not reveal some probes (targeting chromosomes 11q, 13q, 17p, and chromosome 12) structural abnormalities. In this series, we analyzed metaphases by conventional cytogenetics, followed by interphase and metaphase fluorescence in situ hybridization. We were able to observe 17 cases of 13q translocations with deletions in eight of them. Three distinct regions were involved by translocations in association with or without deletions: a region centromeric to RB1 (13q11 approximately 13), a zone telomeric to D13D25 (13q21 approximately 31), and a 13q14 region deliniated by RB1 and D13S25. In this area, the deletion was variable: RB1 alone (one case), D13S319 approximately D13S25 (five cases), and from RB1 to D13S25 (two cases). The very high frequency of 13q14 loss suggests that these deletions are of pathogenetic importance, but, the importance of the translocations remains to be determined.     

Functions, dysfunctions and possible therapeutic relevance of adenosine A2A receptors in Huntington's disease

The aim of this review is to summarize and critically discuss the complex role played by adenosine A_2A receptors (A_2ARs) in Huntington's disease (HD). Since A_2ARs are mainly localized on the neurons, which degenerate early in HD, and given their ability to stimulate glutamate outflow and inflammatory gliosis, it was hypothesized that they could be involved in the pathogenesis of HD, and that A_2AR antagonists could be neuroprotective. This was further sustained by the demonstration that A_2ARs and underlying signaling systems undergo profound changes in cellular and animal models of HD. More recently, however, the equation A_2A receptor blockade = neuroprotection has appeared too simplistic. First, it is now definitely clear that, besides mediating ‘bad’ responses (for example, stimulation of glutamate outflow and excessive glial activation), A_2ARs also promote ‘good’ responses (such as trophic and antinflammatory effects). This implies that A_2AR blockade results either in pro-toxic or neuroprotective effects according to the mechanisms involved in a given experimental model. Second, since HD is a chronically progressive disease, the multiple mechanisms involving A_2ARs may play different relative roles along the degenerative process. Such different mechanisms can be influenced by A_2AR activation or blockade in different ways, even leading to opposite outcomes depending on the time of agonist/antagonist administration. The number, and the complexity, of the possible scenarios is further increased by the influence of mutant Huntingtin on both the expression and functions of A_2ARs, and by the strikingly different effects mediated by A_2ARs expressed by different cell populations within the brain.