• Volume 82, Issue 2

      August 1975,   pages  41-76

    • Mechanism of yolk formation in the oocytes ofTriturus pyrrhogaster

      N H Gopal Dutt Sakae Inoue

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      The process of yolk formation in the oocytes of the Japanese newt,Triturus pyrrhogaster is described. Ultrastructural evidence reveals that the yolk protein which is synthesised elsewhere is taken into the oocyte through micropinocytosis in the form of yolk precursor bodies. These bodies later grow into yolk plates of definite structure under the influence of mitochondria.

    • Histochemical study of shoot-root apices inPanicum miliaceum Linn. seedlings

      C K Rudramuniyappa M G Panchaksharappa

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      The histochemical nature of shoot and root apices inPanicum miliaceum L. seedlings was studied using light microscopic histochemical procedures on tissue-sections. The substances localized are: RNA, proteins, polysaccharides and reducing sugars.

      The shoot apex generally shows uniform distribution of starch grains in all the zones, the presence of which is noticed more in the subtending area of the shoot apex. RNA is abundant in the flank zones, comparatively low in the corpus region and very low in the subtending area of the shoot apex. Proteins and reducing sugars are rich in all the zones of the apex. Present observation confirms that the shoot apex ofPanicum is quite active metabolically.

      In the root apex, the so-called quiescent centre lacks starch, which is present in the cortex and mature root-cap cells. RNA and proteins are low in the quiescent zone, but high in the root-cap initials, procambial strands and cortex. Reducing sugars are rich in the root apex, but low or negligible in mature root-cap cells and in subtending regions of the root. Based on the present study, the quiescent zone could be identified inPanicum root.

    • An analysis of shear fractures

      K V Suryanarayana

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      The megascopically isotropic granites of Tirupati have several sets of joints of which the two joint sets of N 64° W and N 70° E trends have a prominent development. Their axis of intersection is vertical. The angle between the two is 46°. The E-W direction bisects this dihedralangle, and it is, therefore, interpreted that the compressive force has acted in the E-W direction. Petrofabric analysis of the granites reveals the presence of another set of conjugate shear, statistical in nature, making a dihedral angle of 60°, and with the axis of intersection horizontal oriented in a N-S direction. This dihedral angle is bisected by the same E-W directed compressive force. Conclusion is drawn that both the megascopic conjugate shear intersecting in a vertical axis and the potential shear joints intersecting in a horizontal axis are developed by a compressive force acting in the E-W direction.

    • Effect of herbicides on the carbohydrate and nitrogen contents of nutgrass (Cyperus rotundus L.)

      L P Misra L D Kapoor R S Choudhri

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      The effect of four herbicides on the starch and nitrogen contents of the tubers, dry matter production, carbohydrate, amide, amino, ammonium and nitrate nitrogen contents of the foliage of nutgrass (Cyperus rotundus L.) under pot culture conditions was studied. The starch content of the tubers of nutgrass depleted maximum by the Embutox-plus and Tok E-25 when applied as foliar spray and soil placement, respectively. The foliar application of Embutox-plus and Tok E-25 appeared to have maximum reduction in the carbohydrate and different nitrogen contents in the foliage of nutgrass as compared with other herbicides used. Severe reduction in the amide and amino nitrogen was observed as against ammonium or nitrate nitrogen content on the application of herbicides.

    • Effect of magnesium deficiency on oxidative phosphorylation, mitochondrial swelling and protein synthesis in weanling rats

      Shanta Sharma nee Amarlal

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      1. Hypomagnesemia was induced in weanling rats by feeding a magnesium-low diet. During a 78 day regimen on this diet, the animals showed retarded growth rate and low concentrations of magnesium in liver, kidney, skeletal muscle and heart but not in brain. When animals fed with the magnesium-low diet were returned to the control diet for 18 days, the Mg content of serum, heart, liver and kidney increased appreciably. The Mg content of skeletal muscle did not increase on supplementation.

      2. Marked inhibition of P:O ratios was noticed in mitochondria prepared from magnesium deficient rats. P:O ratios were resorted to normal by supplementation with Mg.

      3. Hypomagnesemia produced as above also led to depletion of tissue proteins and mitochondrial proteins. On injecting valine-1-14C such animals incorporatedin vivo significantly less of radioactivity into tissue and mitochondrial proteins. This defect was also partially corrected on returning the animals to the control diet.

      4. Mitochondrial fractions prepored from tissues of weanling rats receiving the magnesium-low diet for 60 days showed increased swelling as evidenced by their differential response to calcium pentachlorophenol, phloridzin, orp-chloromercuri benzoate as compared to mitochondria prepared from tissues of control animals.

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