• N Singh

      Articles written in Journal of Biosciences

    • Scanning electron microscopic study of the olfactory epithelium of four coldwater hillstream teleosts from Garhwal hills (India)

      N Singh

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      This contribution deals with the scanning electron microscopic surface structure of olfactory epithelium in four hillstream teleosts from the glacialfed river Alaknanda in Garhwal Himalaya (UP, India). The closely related species—Schizothorax plagiostomus, Schizothorax richardsonii (both bottom dweller, bottom feeder, herbiomnivorous) andSchizothoraichthys progastus (column dweller, column feeder, carniomnivorous) reveal the predominance of different types of olfactory receptor cell types separately in their respective olfactory epithelium while the distinctly related speciesCrossocheilus latius latius with similar nature as first two (i.e. bottom dweller, bottom feeder, herbiomnivorous) displays the presence of more microvillous cells in the olfactory epithelium. Possibly, the occurrence of particular receptor cells in a fish species is related to the ecological and feeding behaviours with distinct mechanism of olfaction.

    • Fine structure of olfactory epithelium inSchizothoraichthys progastus McClelland andSchizothorax richardsonii Gray (Cyprinidae: Teleostei) from Garhwal Himalaya (India)

      N Singh K C Bhatt Mukesh K Bahuguna Dharmendra Kumar

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      The olfactory epithelium of two closely related species of snowtrout—Schizothoraichthys progastus McClelland andSchizothorax richardsonii Gray (Subfamily: Schizothoracinae. family-Cyprinidae, Teleostei), from a perennial glacier-fed river Mandakini of Garhwal hills was studied by employing transmission electron microscopic method The olfactory lamella comprises two epithelia—anterior and posterior, with a stroma sandwiched in between. Both are strartified. The anterior one is thicker than posterior. InSchizothoraichithys progastus, the sensory part of epithelium has two types of receptor cells—ciliated receptor cells and rod cells whilst inSchizothorax richardsonii, there arc three types of receptor cells—ciliated receptor cells, microvillous receptor cells and rod cells in addition to sustentacular cells, basal cells and mucous cells. While inhabiting similar hillstream habitat, the differential ecological niches, feeding habits etc., account for the presence of different receptor cell types in these species, It implies the possible diversification at cellular and physiological levels so as to minimize the competition by using varied olfactory cues.

    • Assessment of lexical semantic judgment abilities in alcohol-dependent subjects: An fMRI study

      D Bagga N Singh S Modi P Kumar D Bhattacharya M L Garg S Khushu

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      Neuropsychological studies have shown that alcohol dependence is associated with neurocognitive deficits in tasks requiring memory, perceptual motor skills, abstraction and problem solving, whereas language skills are relatively spared in alcoholics despite structural abnormalities in the language-related brain regions. To investigate the preserved mechanisms of language processing in alcohol-dependents, functional brain imaging was undertaken in healthy controls (𝑛=18) and alcohol-dependents (𝑛=16) while completing a lexical semantic judgment task in a 3 T MR scanner. Behavioural data indicated that alcohol-dependents took more time than controls for performing the task but there was no significant difference in their response accuracy. fMRI data analysis revealed that while performing the task, the alcoholics showed enhanced activations in left supramarginal gyrus, precuneus bilaterally, left angular gyrus, and left middle temporal gyrus as compared to control subjects. The extensive activations observed in alcoholics as compared to controls suggest that alcoholics recruit additional brain areas to meet the behavioural demands for equivalent task performance. The results are consistent with previous fMRI studies suggesting compensatory mechanisms for the execution of task for showing an equivalent performance or decreased neural efficiency of relevant brain networks. However, on direct comparison of the two groups, the results did not survive correction for multiple comparisons; therefore, the present findings need further exploration.

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