Environmental enrichment modulates affiliative and aggressive social behaviour in the neuroligin-3 R451C mouse model of autism spectrum disorder.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterised by impairments in social communication and the presence of restrictive and repetitive behaviours. A mouse model expressing an autism-associated R451C mutation in the gene encoding the synaptic adhesion protein neuroligin-3 (NL3) has been extensively characterised and shows altered behaviour relevant to core traits observed in ASD. Reported impairments in social behaviours in NL3R451C mice however remain controversial due to inconsistent findings in various assays across different laboratories. Such inconsistencies could plausibly be explained by an increased susceptibility of the NL3R451C mouse social phenotype to environmental modulation. To address this, NL3R451C mice were housed in standard or enriched housing from 4 weeks of age prior to behavioural testing. Enrichment rearing enhanced direct interactions with the stranger mouse in all mice in the three-chamber social interaction test however, NL3R451C mice did not show impairment in social interaction in the three-chamber test, in contrast with previous reports. Environmental enrichment enhanced aggressive behaviour in all mice, and did not specifically alter the heightened aggressive phenotype previously described in NL3R451C mice. Specific genotype effects of enrichment included reduced anxiety-like behaviour in WT mice, and lower locomotor activity levels in NL3 mice. While genotype-specific effects of enrichment were not seen on social behaviour, the general increase in affiliative social interaction and aggression seen in all mice, indicates that these behaviours, are vulnerable to change based on housing condition. Mouse models expressing ASD-associated mutations have great utility in elucidating the neurobiology underling development of core traits and it is crucial that efforts are focussed on those models exhibiting robust phenotypes. In light of the findings in the present study, we suggest approaches to improve replicability and reproducibility in mouse models of ASD.

Leukonychia striae.

A 19-year-old keypuncher had leukonychia striae. The pattern of striae suggested that they occurred as a result of the mechanical stimulation of keypunching.

The potential of NO3--N utilization by a woody shrub species Lindera triloba: a cultivation test to estimate the saturation point of soil NO3--N for plants.

Responses of seedlings of a shrub species, Lindera triloba, grown in perlite culture medium, to nitrate (NO3--N) supply were investigated to estimate the saturating point of available NO3--N for plant utilization. NO3--N concentration and nitrate reductase activity (NRA) in leaves and roots were used as indicators of NO3--N uptake and assimilation by L. triloba. Root NRA increased with NO3--N supply when concentrations were low and reached a plateau at high NO3--N concentrations. On the other hand, root NO3--N concentration increased linearly with NO3--N supply; therefore, it is suggested that NO3--N uptake did not limit NO3--N assimilation by L. triloba. In contrast, leaf NRA and leaf NO3--N concentration were low and were not influenced by NO3--N supply. This may be caused by the lack of transport of NO3--N from roots to leaves. The NO3--N retained in perlite was compared with NO3--N pool sizes in soils from a forest where L. triloba occurs naturally to estimate the level of NO3--N availability to plants in the forest soil. The maximum NO3--N pool size in the forest soil was comparable to concentrations at which root NRA reached a plateau in perlite cultures. These results indicate that soil NO3--N availability is below the saturation point for NO3--N uptake by L. triloba, and it is the limiting factor of NO3--N utilization by L. triloba under field conditions in which this species naturally occurs.

Chicken erythrocyte pyrimidine 5'-nucleotidase: purification and characterization of the subclass I enzyme.

Nucleotidase activities resembling subclass I and subclass II of human pyrimidine 5'-nucleotidases (P5N) were detected in chicken red blood cells (RBCs). In chicken RBCs from untreated controls, the activity of the subclass II enzyme was about one third of that of subclass I enzyme, whereas that ratio was approximately 5:1 in rat or human RBCs. The subclass I activity in chicken RBCs was increased 5- to 6-fold upon erythropoietic induction by phenylhydrazine administration, but the subclass II activity did not increase under these conditions. The subclass I enzyme was purified to near homogeneity. Its molecular mass was about 35 kDa as estimated by gel filtration and SDS-polyacrylamide gel electrophoresis. Its N-terminal 12 amino acids, PEFQKKTVHIKD, were also determined. The catalytic properties of the subclass I enzyme were very similar to those of the human enzyme with regard to substrate (preferential hydrolysis of CMP, dCMP, UMP), Km values, optimum pH, and metal ion requirements. Antibodies against chicken P5N subclass I were raised in rats. The chicken P5N-I as well as the rat P5N-I proteins could be detected by antibodies in Western blot analyses, but not the P5N-II proteins. These findings indicate that P5N subclass I may have an important function in chicken erythropoiesis.