A systematic review of nitric oxide donors and L-arginine in experimental stroke; effects on infarct size and cerebral blood flow.

BACKGROUND: Nitric oxide (NO) is a candidate treatment for acute ischaemic stroke, however published studies in experimental stroke have given conflicting results. METHODS: We performed a systematic review of published controlled studies of L-arginine (the precursor for NO) and NO donors in experimental stroke. Data were analysed using the Cochrane Collaboration Review Manager software. Standardised mean difference (SMD) and 95% confidence intervals (95% CI) were calculated. RESULTS: Altogether, 25 studies(s) were identified. L-Arginine and NO donors reduced total cerebral infarct volume in permanent (SMD -1.21, 95% CI -1.69 to -0.73, p < 0.01, s = 10) and transient models of ischaemia (SMD -0.78, 95% CI -1.21 to -0.35, p < 0.01, s = 7). Drug administration increased cortical CBF in permanent (SMD +0.86, 95% CI 0.52-1.21, p < 0.01, s = 8) but not transient models (SMD +0.34, 95% CI -0.02 to 0.70, p = 0.07, s = 4). CONCLUSIONS: Administration of NO in experimental stroke reduces stroke lesion volume in permanent and transient models. This may be mediated, in part, by increased cerebral perfusion in permanent models. These data support clinical trials in stroke patients, although the presence of a narrow therapeutic time window may be a limiting factor.     

Importance of the degree of antigen polymerization by detoxification in modulating the immunogenicity of acellular pertussis vaccine

For the acellular pertussis vaccine with a high immunogenicity, the concentration, composition and characteristics of acellular pertussis antigens are the crucial points to be considered. Nevertheless, it has not been proved yet whether or not the polymerization degree, one of the characteristics of formalin-detoxified acellular pertussis antigens, has an influence on vaccine potency. Thus, in the present study, the correlations among detoxification conditions of acellular pertussis bulks, their polymerization degrees and their immunogenicities were examined. In addition, the relative importance of pertussis toxoid in vaccine immunogenicity was also investigated. Results show that a lower lysine concentration during detoxification induces highly-polymerized antigens, the immunogenicity has a great dependency on the polymerization degree of antigens, and also pertussis toxoid has a relatively stronger influence on the immunogenicity than other antigens. Accordingly, in the aspect of the potency of detoxified acellular pertussis vaccine, it can be demonstrated that the polymerization of antigens and its degree are the major factors affecting the immunogenicity along with a relatively high content of pertussis toxoid.     

Mort programmée des cellules germinales testiculaires: causes et mécanismes mis en jeu

Spermatogenesis results from a balance between proliferation and apoptosis. An alteration in this balance could lead to testicular diseases such as testicular tumour or infertility. Apoptosis seem to be important in regulating the processes of spermatogenesis since 60 to 75% of germ cells do not reach the spermatozoa stage. The various molecules of the apoptotic cascade have been detected in rodent or human germ cells, such as effector caspases and upstream proteins from cell death receptor or mitochondrial pathways. One or several different pathways may be involved in the germ cell apoptotic process triggered physiologically, by hormonal deprivation, or by chemical or physical inducers. Finally, caspases appear to play a role in various testicular diseases (particularly infertility).     

Invasion in space and time: non-native species richness and relative abundance respond to interannual variation in productivity and diversity

Ecologists have long sought to understand the relationships among species diversity, community productivity and invasion by non‐native species. Here, four long‐term observational datasets were analyzed using repeated measures statistics to determine how plant species richness and community resource capture (i.e. productivity) influenced invasion. Multiple factors influenced the results, including the metric used to quantify invasion, interannual variation and spatial scale. Native richness was positively correlated with non‐native richness, but was usually negatively correlated with non‐native abundance, and these patterns were stronger at the larger spatial scale. Logistic regressions indicated that the probability of invasion was reduced both within and following years with high productivity, except at the desert grassland site where high productivity was associated with increased invasion. Our analysis suggests that while non‐natives were most likely to establish in species rich communities, their success was diminished by high resource capture by the resident community.     

Dynamic management of genetic resources: maintenance of outcrossing in experimental metapopulations of a predominantly inbreeding species

Dynamic management of genetic resources inpredominantly inbreeding species requiresincreased levels of outcrossing to limit theloss of genetic variation due to smallereffective sizes and to favour the emergence ofnew genetic combinations. Here, we show thatoutcrossing rates can artificially bepermanently increased in experimental evolvingplant metapopulations, using Arabidopsisthaliana as a model. We introducedmale-sterility genes and used an adequatemanagement of the resulting female plants tomodify the outcrossing rates. As expected, theincrease in outcrossing resulted in lowerlevels of heterozygote deficiency (F _is) than observed in natural populationsof A. thaliana and therefore in themaintenance of potentially higher levels ofgenetic variation. An additional selectiveadvantage for females' offspring, due to theproduction of larger seeds by females and apossible heterosis effect, furthermore led tosmaller F _is than expected from therealized outcrossing rate. This selectiveadvantage also resulted in an increase infemale frequency, especially in metapopulationswith large population sizes, creating anon-causal negative correlation between femalefrequency and heterozygote deficiency.     

Hyperhydricity of Micropropagated Shoots: A Typically Stress-induced Change of Physiological State

Hyperhydricity of micropropagated shoots, formerly called vitrification, undoubtedly results from growth and culture conditions, subjectively reputated as stressing factors: wounding, infiltration of soft culture medium, generally of a high ionic strength, rich in nitrogen and in growth regulators in a special balance, in a humid and gaseous confined atmosphere. Stress is (objectively) defined as a disruption of homeostasis resulting from a constraint escaping the usual flexibility of metabolism. It induces another temporary (reversible) or definitive (irreversible) thermodynamic physiological state. The state-change concept developed by Strasser (1988) and Strasser and Tsimilli-Michael (2001) is applicable to the phenomenon of hyperhydricity. An appraisal of the redox capacities of hyperhydrated shoots together with a study of some enzymic activities that catalyse pentose phosphate and glycolytic pathways has indeed shown that such shoots have evolved towards a temporary state of lower differentiation or a juvenile state with a sufficient activity to survive and to defend themselves.     

Avian Risk Assessment: Effects of Perching Height and Detectability

We studied two components of predator risk assessment in birds. While many species are limited to seeking safety under cover or under ground, some birds can fly away from their predators and escape to trees. If birds in fact ‘feel’ safer (e.g. perceive less risk) in trees, we would expect them to tolerate closer approach by a potential terrestrial predator. Another component of safety is at which point the animal detects an approaching threat, which we expected to increase with eye size, assuming eye size is a surrogate for visual acuity. We used the distance birds moved away from an approaching human [flight initiation distance (FID)] as a metric to determine whether birds associated a lower risk of predation by being in trees, and we used the distance at which birds first displayed alert behaviors from an approaching human (alert distance) to determine if birds with larger eyes had higher detection distances. Although some species were affected by tree height, we found no clear pattern that birds assessed themselves to be at a lower risk of predation when they were ≥3 m above the ground compared with being <3 m above ground. In the 10 species for which height had any significant effect on FID, birds ≥3 m off the ground had greater FIDs in six species, but the remaining three species had the opposite response. While we found a significant positive relationship between eye size and alert distance in 23 species, the relationship was not present in a phylogenetic analysis using independent contrasts, which suggests that the apparent relationship was influenced strongly by the association between the studied species. Together, these results suggest that birds do not obviously associate being in a tree with safety, and that variations in visual acuity, per se, cannot be used as a general indicator of differences in alert distances, as previously suggested in the literature.     

Learning-induced modulation of oscillatory activities in the mammalian olfactory system: The role of the centrifugal fibres

In the mammalian olfactory system, oscillations related to odour representation have been described in field potential activities. Previous results showed that in olfactory bulb (OB) of awake rats engaged in an olfactory learning, odour presentation produced a decrease of oscillations in gamma frequency range (60-90 Hz) associated with a power increase in beta frequency range (15-40 Hz). This response pattern was strongly amplified in trained animals. The aim of this work was twofold: whether learning also induces similar changes in OB target structures and whether such OB response depends on its centrifugal inputs. Local field potentials (LFPs) were recorded through chronically implanted electrodes in the OB, piriform and enthorhinal cortices of freely moving rats performing an olfactory discrimination. Oscillatory activities characteristics (amplitude, frequency and time-course) were extracted in beta and gamma range by a wavelet analysis. First, we found that odour induced beta oscillatory activity was present not only in the OB, but also in the other olfactory structures. In each recording site, characteristics of the beta oscillatory responses were dependent of odour, structure and learning level. Unilateral section of the olfactory peduncle was made before training, and LFPs were symmetrically recorded in the two bulbs all along the acquisition of the learning task. Data showed that deprivation of centrifugal feedback led to an increase of spontaneous gamma activity. Moreover, under this condition olfactory learning was no longer associated with the typical large beta band. As a whole, learning modulation of the beta oscillatory response in olfactory structures may reflect activity of a distributed functional network involved in odour representation.     

Effect of Overexpression of Actinobacillus succinogenes Phosphoenolpyruvate Carboxykinase on Succinate Production in Escherichia coli

Succinate fermentation was investigated in Escherichia coli strains overexpressing Actinobacillus succinogenes phosphoenolpyruvate carboxykinase (PEPCK). In E. coli K-12, PEPCK overexpression had no effect on succinate fermentation. In contrast, in the phosphoenolpyruvate carboxylase mutant E. coli strain K-12 ppc::kan, PEPCK overexpression increased succinate production 6.5-fold.