Entrainment of neuronal oscillations as a mechanism of attentional selection

Whereas gamma-band neuronal oscillations clearly appear integral to visual attention, the role of lower-frequency oscillations is still being debated. Mounting evidence indicates that a key functional property of these oscillations is the rhythmic shifting of excitability in local neuronal ensembles. Here, we show that when attended stimuli are in a rhythmic stream, delta-band oscillations in the primary visual cortex entrain to the rhythm of the stream, resulting in increased response gain for task-relevant events and decreased reaction times. Because of hierarchical cross-frequency coupling, delta phase also determines momentary power in higher-frequency activity. These instrumental functions of low-frequency oscillations support a conceptual framework that integrates numerous earlier findings.     

Neuroscience. Boosting working memory

Working out which areas of the brain become activated during the formation of working (short-term) memory has been greatly helped by functional magnetic resonance imaging (fMRI). In a Perspective, Robbins et al. discuss new findings (Furey et al.) with fMRI that reveal how working memory is enhanced by the drug physostigmine, which increases cholinergic function in the brain.     

Traditional Crop Diversity and its Conservation on-Farm for Sustainable Agricultural Production in Kumaon Himalaya of Uttaranchal State: A Case Study

Farming communities in traditional agroecosystems have been playing an important role in conserving agricultural diversity. They are not only the custodians but also managers of the crop diversity and maintain the dynamic processes of crop evolution and adaptation, the key elements of sustainable agricultural productions. The Himalayan highlands are important centres of crop plant diversity due to high ecological heterogeneity and high local socio-cultural integrations. The crop genetic diversity of Kumaon Himalaya in Uttarachal State of India has been documented in the present study. Existing crop genetic diversity at inter- and intra-species level was assessed and factors for changes in crop compositions and farming systems during the recent past were studied. Farmer management of rice landrace populations were studied in greater detail. Various benefit enhancing options for farmers from local crop diversity were scrutinized based on farmer perceptions and priorities for efficient management of local crop diversity on-farm and its sustainable utilization for agricultural production.     

Development and validation of gene-based markers for shrunken2-Reference allele and their utilization in marker-assisted sweet corn (Zea mays Sachharata) breeding programme

The recessive shrunken2-Reference (sh2-Ref) allele is traditionally used in sweet corn cultivar development worldwide. However, non-availability of suitable gene-based marker(s) for sh2-Ref has considerably delayed its utilization in molecular breeding. Here, 7,320 bp sequence of Sh2 gene among five wild- and six sh2-Ref-based inbreds was analysed by employing 13 overlapping primers. SNP583 (A in wild and G in mutant) and SNP755 (T in wild and C in mutant) in 5’UTR, and SNP5112 (C in wild and T in mutant) in intron-12 clearly differentiated dominant (Sh2) and recessive (sh2-Ref) allele. These SNPs were used to develop four gene-based PCR markers. The newly developed markers were validated in six F₂ populations segregating for sh2-Ref allele, and 230 diverse inbreds of normal and sweet corn types. These markers were further used in genotyping of BC₁F₁ populations leading to successful selection of sh2-Ref allele in the marker-assisted breeding. Globally, this assumes great significance in molecular breeding of sweet corn.     

Antioxidant xanthones from the pericarp of Garcinia mangostana (Mangosteen)

As part of ongoing research on cancer chemopreventive agents from botanical dietary supplements, Garcinia mangostana L. (commonly known as mangosteen) was selected for detailed study. Repeated chromatography of a CH2Cl2-soluble extract of the pericarp led to the isolation of two new highly oxygenated prenylated xanthones, 8-hydroxycudraxanthone G (1) and mangostingone [7-methoxy-2-(3-methyl-2-butenyl)-8-(3-methyl-2-oxo-3-butenyl)-1,3,6-trihydroxyxanthone, 2], together with 12 known xanthones, cudraxanthone G (3), 8-deoxygartanin (4), garcimangosone B (5), garcinone D (6), garcinone E (7), gartanin (8), 1-isomangostin (9), alpha-mangostin (10), gamma-mangostin (11), mangostinone (12), smeathxanthone A (13), and tovophyllin A (14). The structures of compounds 1 and 2 were elucidated by spectroscopic data analysis. Except for compound 2, which was isolated as a minor component, the antioxidant activities of all isolates were determined using authentic and morpholinosydnonimine-derived peroxynitrite methods, and compounds 1, 8, 10, 11, and 13 were the most active. Alpha-mangostin (10) inhibited 7,12-dimethylbenz[alpha]anthracene-induced preneoplastic lesions in a mouse mammary organ culture assay with an IC50 of 1.0 microg/mL (2.44 microM).     

Enzymatic modification of a model homogalacturonan with the thermally tolerant pectin methylesterase from Citrus: 1. Nanostructural characterization, enzyme mode of action, and effect of pH

Methyl ester distribution in pectin homogalacturonan has a major influence on functionality. Enzymatic engineering of the pectin nanostructure for tailoring functionality can expand the role of pectin as a food-formulating agent and the use of in situ modification in prepared foods. We report on the mode of action of a unique citrus thermally tolerant pectin methylesterase (TT-PME) and the nanostructural modifications that it produces. The enzyme was used to produce a controlled demethylesterification series from a model homogalacturonan. Oligogalacturonides released from the resulting demethylesterified blocks introduced by TT-PME using a limited endopolygalacturonase digestion were separated and quantified by high-pressure anion-exchange chromatography (HPAEC) coupled to an evaporative light-scattering detector (ELSD). The results were consistent with the predictions of a numerical simulation, which assumed a multiple-attack mechanism and a degree of processivity ～10, at both pH 4.5 and 7.5. The average demethylesterified block size (0.6-2.8 nm) and number of average-sized blocks per molecule (0.8-1.9) differed, depending upon pH of the enzyme treatment. The mode of action of this enzyme and consequent nanostructural modifications of pectin differ from a previously characterized citrus salt-independent pectin methylesterase (SI-PME).     

Manganese status op Rajasthan soils

Because of its significant role in the enzymatic and physiological activities of the plant body, manganese has received the attention of several workers. Though manganese may be present in appreciably large quantities, its availability to plants is controlled by various soil properties, the dominant ones among them being pH, calcium carbonate, clay and organic matter present in the soil (BISWAS, (1), (2), LEEPER, (6)).     

Growth,yield and quality of ber (Zizyphus mauritiana Lamk.) as affected by soil salinity

In a long term experiment on salt tolerance, ber (Zizyphus mauritiana Lamk.) (cv. Umran) was grown in lysimeters artificially salinized with NaCl, CaCl², MgCl² and MgS0₂. No plants survived the highest salinity of 20 dSm-1 electrical conductivity. Pruning weight and tree canopy area were reduced significantly at 5 dSm^-1 but trunk diameter did not decrease until above 5 dSm^-1 soil ECe. The concentration of Na, Ca, Mg and Cl in leaf tissues increased substantially with increasing salinity whereas that of K decreased. Higher salinity reduced the yield and fruit set but had no adverse effect on fruit quality. The 50% yield decrement was found to be associated with a soil ECe value of 11.30 dSm“'.