Rare structural variants disrupt multiple genes in neurodevelopmental pathways in schizophrenia

Schizophrenia is a devastating neurodevelopmental disorder whose genetic influences remain elusive. We hypothesize that individually rare structural variants contribute to the illness. Microdeletions and microduplications >100 kilobases were identified by microarray comparative genomic hybridization of genomic DNA from 150 individuals with schizophrenia and 268 ancestry-matched controls. All variants were validated by high-resolution platforms. Novel deletions and duplications of genes were present in 5% of controls versus 15% of cases and 20% of young-onset cases, both highly significant differences. The association was independently replicated in patients with childhood-onset schizophrenia as compared with their parents. Mutations in cases disrupted genes disproportionately from signaling networks controlling neurodevelopment, including neuregulin and glutamate pathways. These results suggest that multiple, individually rare mutations altering genes in neurodevelopmental pathways contribute to schizophrenia.     

Bitterness and Toxicity in Wild Yam (<Emphasis Type="Italic">Dioscorea</Emphasis> spp.) Tubers of Nepal

Wild yams make a significant contribution to diets of tribal people in Nepal. However, these wild tubers are unpalatable, taste bitter, produce inflammation and show occasional toxicity. Four wild yam species, which are eaten after primary treatment by Nepali aborigines, were analyzed for bitter and toxic principles. Bitter components were identified as furanoid norditerpenes (diosbulbins A and B). Diosbulbins A and B were found in the range of 0.023–0.046 and 0.151–0.442 g kg⁻¹, respectively. Results demonstrated that diosbulbin B, with an average value of 0.314 g kg⁻¹, was the principal bitter compound as compared to diosbulbin A (0.037 g kg⁻¹). The toxic alkaloid, dioscorine and histamine (an allergen) were not detected in these tubers, whereas cyanogens (as HCN equivalent) content were found ranging from 3.2 to 6.0 ppm. Our results revealed that Nepali wild yam tubers are not toxic varieties, as they do not contain either toxic dioscorine or histamine and cyanogens contents were satisfactorily below the safety limits. The inflammation and occasional toxicity observed could possibly be due to the presence of high level of oxalate in these tubers. Domestic cooking methods were found to be very efficient in removing bitterness, thus making the bitter yams palatable.     

Human use of the sand dune ecosystem in the semiarid zone of the Rajasthan Desert,India

Sand dunes form one of the most fragile terrestrial ecosystems. in Rajasthan they have a diverse vegetation and are often utilized by considerable human and livestock populations. a thorough knowledge of the resource utilization by the human and animal populations is essential if the future potential of the ecosystem and its physical stability under changing environmental conditions are to be accurately assessed. This study examines the socio-economic aspect of land degradation at four sites in Churu and Jhunjhunu districts, northwest Rajasthan. an attempt is made to assess the socioeconomic factors leading to land degradation. Data on human use of the Rajasthan (Thar) Desert semiarid ecosystem were collected through individual interviews, group discussions and field measurements. the present exploitation of soil and vegetation resources, possible future biomass deficiency, its impact on sustainable development and role in land degradation are examined. The average number of people in each household in the study area, and the number of livestock each household maintains are too high to allow a satisfactory income to be sustained. the annual income of 50-90 per cent of households was less than 10 000 rupees ($US 1 = 17 rupees in 1987). Sale and consumption of milk, wool, surplus animals and wood provide livelihood, supplemented with income from wage labour. Rain-fed marginal land cultivation produces poor yields and the per capita production is too low to justify the huge soil erosion losses occurring. the number of goats, sheep and cattle owned by the inhabitants has increased tremendously in recent years. Stocking rates vary from 1.63 to 12.08 animals per hectare. the grazing pressure during the dry season, when forage availability decreases, reaches 34.9 animals per hectare. as a result of overgrazing, The land productivity has decreased considerably. the annual fodder deficit values in the study area are enormous. Demand for fuelwood at all the study sites is increasing, yet available forests have already largely been cut down. the distance travelled to collect fuelwood has been increasing, whereas the amount and quality of fuelwood is decreasing. Use of cattle dung to supplement fuelwood during the summer dry season and in drought periods has been decreasing due to low fodder availability and high livestock mortality. Human numbers are increasing, and livestock numbers are also multiplying (except in drought periods) and consequently the available resources are decreasing. Soil erosion and desertification will continue to increase during the next decade unless effective counter measures are undertaken.     

Impact of protection and free grazing on sand dune vegetation in the Rajasthan Desert,India

In the Thar (Rajasthan) Desert of India, sand dunes and sandy plains dominate the landscape. Livestock raising and marginal land cultivation are the main occupations. Owing to the high growth rates of human and livestock populations and a decrease in pasture area and its primary productivity, these lands bear acute grazing pressure. Average rainfall is low and vegetation growth is restricted to the short rainy season of two to four months duration. Often there are years of lower than normal rainfall. In these circumstances, fenced areas, established to stabilize formerly active sand dunes, are increasingly opened to grazing to prevent high stock mortality during droughts. This study was conducted in four fenced and one open site, representative of the region's different vegetation types and grazing pressures. The impact of 2 and 5 per cent free grazing pressure on protected sand dune vegetation density and cover was tested in the two fenced sites. The vegetation data for grazed sites are compared with those for the two ungrazed fenced (protected) and one unfenced (open) site subjected to unlimited grazing pressure throughout the year. The vegetation sampling was carried out by the qaudrat and line-transect method before and after grazing from November 1984 to October 1986. It shows a significant reduction in the density and cover of many palatable species and an increase of unpalatable plants. The effect of vegetation degradation is greater in the unfenced area. The low grazing pressure on the fenced sand dunes sites can still cause drastic changes in the vegetation density and cover. Protection resulted in reduced sand erosion and enhanced growth of palatable plants in the fenced sites under similar climatic and edaphic conditions to the unfenced sites. The grazing pressure in the unfenced areas remains high to extreme during the year, due to low land productivity and high feed demand. The regeneration rate is very slow under the constant (3rd to 5th degree) overgrazing. Low intensity grazing pressure on the fenced sites during droughts can cause heavy utilization and mortality of palatable vegetation.