Axonal regeneration and neuroinflammation: roles for the translocator protein 18 kDa

After a traumatic injury of the nervous system or in the course of a neurodegenerative disease, the speed of axonal regeneration and the control of the inflammatory response are fundamental parameters of functional recovery. Spontaneous regeneration takes place in the peripheral nervous system, although the process is slow and often incomplete. There is currently no efficient treatment for enhancing axonal regeneration, including elongation speed and functional reinnervation. Ligands of the translocator protein 18 kDa (TSPO) are currently under investigation as therapeutic means for promoting neuroprotection, accelerating axonal regeneration and modulating inflammation. The mechanisms of action of TSPO ligands involve the regulation of mitochondrial activity and the stimulation of steroid biosynthesis. In the peripheral nervous system, TSPO expression is strongly up-regulated after injury, primarily in Schwann cells and macrophages, but also in neurones. Its levels return to low control values when nerve regeneration is completed, strongly supporting an important role in regenerative processes. We have demonstrated a role for the benzoxazine etifoxine in promoting axonal regeneration in the lesioned rat sciatic nerve, either after freeze-injury or complete transection. Etifoxine is already clinically approved for the treatment of anxiety disorders (Stresam(®) , Biocodex, Gentilly, France). Daily treatment with etifoxine resulted in a two-fold acceleration in axonal regeneration, as well as in a marked improvement of both the speed and quality of functional recovery. The neuroregenerative effects of etifoxine are likely to be mediated by TSPO, and they may involve an increased synthesis of pregnenolone and its metabolites, such as progesterone. After freeze-injury of the sciatic nerve, administration of etifoxine also strongly reduced the number of activated macrophages and decreased the production of the inflammatory cytokines tumour necrosis factor-α and interleukin-1β. Thus, this drug offers promise for the treatment of peripheral nerve injuries and axonal neuropathies. It may also be used as a lead compound in the development of new TSPO-based neuroprotective approaches.

The metabolic activity of gut microbiota in obese children is increased compared with normal-weight children and exhibits more exhaustive substrate utilization

Objective:

The gut microbiota contribute otherwise impossible metabolic functions to the human host. Shifts in the relative proportions of gut microbial communities in adults have been correlated with intestinal disease and have been associated with obesity. The aim of this study was to elucidate differences in gut microbial compositions and metabolite concentrations of obese versus normal-weight children.

Materials and methods:

Fecal samples were obtained from obese (n=15; mean body mass index (BMI) s.d. score=1.95) and normal-weight (n=15; BMI s.d. score=−0.14) Swiss children aged 8–14 years. Composition and diversity of gut microbiota were analyzed by qPCR and temperature gradient gel electrophoresis (TGGE).

Results:

No significant quantitative differences in gut microbiota communities of obese and normal-weight children were identified. Microbial community profiling by TGGE revealed a high degree of both intra- and intergroup variation. Intergroup comparison of TGGE profiles failed to identify any distinct populations exclusive to either obese or normal-weight children. High-pressure liquid chromatography analysis identified significantly higher (P<0.05) concentrations of short-chain fatty acids (SCFA) butyrate and propionate in obese versus normal-weight children. Significantly lower concentrations of intermediate metabolites were detected in obese children, suggesting exhaustive substrate utilization by obese gut microbiota.

Conclusions:

Our results indicate that a dysbiosis may be involved in the etiology of childhood obesity. In turn, aberrant and overactive metabolic activity within the intestine could dictate survival or loss of individual microbial communities, leading to the altered population ratios previously identified in adult obesity.

Monitoring of nosocomial invasive aspergillosis and early evidence of an outbreak using cumulative sum tests (CUSUM)

In order to provide a statistically based evaluation of the incidence of invasive aspergillosis (IA) over time, we applied the cumulative sums (CUSUM) methodology, which was developed for quality control and has already been applied for the surveillance of hospital-acquired infections. Cases of IA were recorded during a 5-year period. Incidence rates of cases assumed to be hospital-acquired, i.e. nosocomial IA (NIA), were analysed using CUSUM tests. Relationships between NIA, fungal contamination and construction or renovation work were tested using time-series methods. Between January 2002 and December 2006, 81 cases of NIA were recorded. CUSUM analysis of NIA incidence showed no significant deviation from the expected monthly number of cases until August 2005, and then the CUSUM crossed the decision limit, i.e. identified a significant increase in NIA as compared with the reference period (January 2002 to December 2004). Up to April 2006, the learning-curve CUSUM stayed over its limit, supporting an ongoing outbreak involving 24 patients, and then it significantly decreased in May 2006. Follow-up after May 2006 indicated no out-of-control situation, supporting a return to the baseline situation. In haematology wards, significant links were found between NIA incidence and fungal contamination of several sites at each ward (mainly unprotected common sites). An environmental source of contamination could be suspected, but no significant relationship was found between NIA incidence and ongoing construction or renovation. In conclusion, the CUSUM test proved to be well suited for real-time monitoring of NIA and for early identification and follow-up of an outbreak.

The invasion route for an insect pest species: the tobacco aphid in the New World

Biological invasions are rapid evolutionary events in which populations are usually subject to a founder event during introduction followed by rapid adaptation to the new environment. Molecular tools and Bayesian approaches have shown their utility in exploring different evolutionary scenarios regarding the invasion routes of introduced species. We examined the situation for the tobacco aphid, Myzus persicae nicotianae, a recently introduced aphid species in Chile. Using seven microsatellite loci and approximate Bayesian computation, we studied populations of the tobacco aphid sampled from several American and European countries, identifying the most likely source populations and tracking the route of introduction to Chile. Our population genetic data are consistent with available historical information, pointing to an introduction route of the tobacco aphid from Europe and/or from other putative populations (e.g. Asia) with subsequent introduction through North America to South America. Evidence of multiple introductions to North America from different genetic pools, with successive loss of genetic diversity from Europe towards North America and a strong bottleneck during the southward introduction to South America, was also found. Additionally, we examined the special case of a widespread multilocus genotype that was found in all American countries examined. This case provides further evidence for the existence of highly successful genotypes or 'superclones' in asexually reproducing organisms.