Brain-derived neurotrophic factor signaling is altered in the forebrain of Engrailed-2 knockout mice.

Engrailed-2 (En2), a homeodomain transcription factor involved in regionalization and patterning of the midbrain and hindbrain regions has been associated to autism spectrum disorders (ASDs). En2 knockout (En2(-/-)) mice show ASD-like features accompanied by a significant loss of GABAergic subpopulations in the hippocampus and neocortex. Brain-derived neurotrophic factor (BDNF) is a crucial factor for the postnatal development of forebrain GABAergic neurons, and altered GABA signaling has been hypothesized to underlie the symptoms of ASD. Here we sought to determine whether interneuron loss in the En2(-/-) forebrain might be related to altered expression of BDNF and its signaling receptors. We first evaluated the expression of different BDNF mRNA isoforms in the neocortex and hippocampus of wild-type (WT) and En2(-/-) mice. Quantitative RT-PCR showed a marked down-regulation of several splicing variants of BDNF mRNA in the neocortex but not hippocampus of adult En2(-/-) mice, as compared to WT controls. Accordingly, levels of mature BDNF protein were lower in the neocortex but not hippocampus of En2(-/-) mice, as compared to WT. Increased levels of phosphorylated TrkB and decreased levels of p75 receptor were also detected in the neocortex of mutant mice. Accordingly, the expression of low density lipoprotein receptor (LDLR) and RhoA, two genes regulated via p75 was significantly altered in forebrain areas of mutant mice. These data indicate that BDNF signaling alterations might be involved in the anatomical changes observed in the En2(-/-) forebrain and suggest a pathogenic role of altered BDNF signaling in this mouse model of ASD.

Epidemiology of Toxocara canis in the dog population from two areas of different socioeconomic status, Greater Buenos Aires, Argentina.

Toxocara canis infection in dogs is a public health problem in most countries, although it has been poorly documented in many of them. The main objective of the present work was to investigate the epidemiology of infection in the canine populations from two areas of Buenos Aires of different socioeconomic status and urban conditions: a middle-income neighbourhood (MIN) and a low-income neighbourhood (LIN). This study evaluated the prevalence of infection in dogs by parasitological and serological techniques in both areas, and described the relationship between the infection and different epidemiological variables for each neighbourhood. A cross-sectional study was carried out after a house-to-house census was completed. During August 1999, a sample of households was selected at random (nMIN=53 and nPA=52). In each house, one dog was randomly chosen for the collection of fresh faeces and blood. The dog owners were interviewed utilising a questionnaire about dogs on sex, recent anthelmintic treatment, degree of confinement, control by the dog's owner (whether the dog goes out of the house accompanied or not, leashed or unleashed), defecation site, defecation substratum and number of dogs in the house. The diagnostic techniques were concentration-sedimentation formalin/ether method and ELISA test. The parasitological prevalences in dogs were 9% (5/53) in MIN and 19% (10/52) in LIN, and serological prevalences were 22% (2/9) in MIN and 40% (15/37) in LIN. In MIN, the patent infection of males was significantly higher than that of females. In LIN, puppies less than 1 year old were the most prevalent age class. Our serological results showed that the positivity of adult dogs was more frequent in LIN than in MIN. The density of puppies with patent infection was seven times higher in LIN than in MIN, when combining coprological analysis and the estimated age structure obtained by the census.

Effects of black howler monkey (Alouatta caraya) seed ingestion on insect larvae.

Fig (Ficus monckii) and laurel (Ocotea puberula) seeds were obtained from Alouatta caraya feces (ingested seeds) and from trees (noningested) in northeastern Argentina. Seeds were examined to detect the presence (infested) or absence (noninfested) of larvae. Sixty percent (N = 315) of noningested fig seeds were galls with insect larvae inside, while 23% (N = 331) were encountered in the ingested group. Eighty-two percent (N = 28) of noningested laurel seeds were infested, and only 19% (N = 63) of ingested seeds were infested. According to the present data, the insects' larvae are digested by howlers intaking animal protein, but the laurel seeds were not destroyed.

Dietary variability in Cebus apella in extreme habitats: evidence for adaptability.

The dietary composition of Cebus apella in two subtropical forest environments of Argentina reflects the seasonal availability of potential food resources. In the marginal areas of the geographical distribution of this species, different resources are used during periods of scarcity. A greater tendency to use leaves in the diet is observed in the northwest (El Rey National Park), where there is greater seasonal variation of fruit availability. In El Rey, where there are few potential resources, the diet is dominated by a few resources, notably bromeliads. Where the resources are more abundant and the availability is more constant throughout the years (Baritú and Iguazú National Parks), the monkeys exhibit a feeding behavior similar to that seen in tropical areas. This ability of the genus Cebus to exploit resources not accessible to other primate species is one of the reasons for its wide geographical distribution and its widespread existence in ecosystems marginally used by primates.