Department of Biological Sciences

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Start date: 1990End date: 1999

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    Inhibition of mitochondrial electron transport is the prime cause behind proline accumulation during mineral deficiency in Oryza sativa
    (Springer, 1993) Bhagavatula, Vani
    The concentration of proline in shoots of rice (Oryza sativa) seedlings raised in distilled water was about 3.3 times higher than in the seedlings raised in modified B5 medium. The shoots of seedlings raised in B5 medium which was depleted of calcium, iron, magnesium or potassium had a higher concentration of proline than those grown in standard B5 medium. The shoots of seedlings raised in distilled water with iron had a lower level of proline than those in distilled water. These results suggest that iron deficiency leads to high proline accumulation.
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    Effect of short-term heat treatment of rice seedlings on sensitivity of thylakoid membranes to photoinhibition
    (Springer, 1996) Bhagavatula, Vani
    The after-effects of 24 h high temperature (35 or 45 ~ treatment on the photochemical activities and photooxidative lipid peroxidation, subsequent to their irradiation were studied in 7-d-old etiolated rice (Oryza sativa) seedlings. Photosystem (PS) 1 and PS 2 mediated photoreactions of thylakoids isolated from the seedlings exposed to high temperature did not differ significantly from the thylakoids isolated from control seedlings (25 ~ Hence, all kinds of tested thylakoids were equally efficient in capturing and utilizing radiant energy. The high irradiance induced loss in PS 2 activity and lipid peroxidation measured in terms of malondialdehyde production was more rapid in thylakoids isolated from stressed seedlings as compared to that of control seedlings. Thus the thylakoids isolated from the stressed seedlings were more prone to photodamage than those from the control seedlings.
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    Alteration in NAD+/NADH ratio regulates salt stress induced proline accumulation in Vigna radiata.
    (NAS, 1996) Bhagavatula, Vani
    Five-day-old vigna radiata seedlings exposed to NaCI stress induced a significant enhancement in proline levels accompanied by reduction in growth
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    Structure-function correlation during the etioplast-chloroplast transition in cucumber cotyledonary leaves
    (IJPR, 1998) Bhagavatula, Vani
    We studied the development of chloroplasts from etioplasts in the cotyledonary leaves of 4-d-old dark-grown cucumber (Cucumis sativus) seedlings after irradiation (20 μmol m-2 s-1). Upon irradiation, the triggering of chlorophyll (Chl) synthesis and accumulation showed a relatively short lag phase. The irradiation of etiolated seedlings initiated the synthesis of apoproteins of pigment-protein complexes. While Chl-protein 2 (CP2) was detected at 6 h after irradiation, CP1 only after 29 h. The appearance and accumulation of some of the apoproteins were monitored by Western-blotting. LHC2 apoprotein was detected after a 6 h-irradiation. The amounts of D1 protein of photosystem (PS) 2 and PsaA/B protein of PS1 were quantitated by ELISA. Further, the thylakoid membrane function during this time period in terms of PS1- and PS2-mediated electron transfer activity and intersystem electron pool size were analyzed. While PS1 activity was detected after 4 h, PS2-mediated O2 evolution was detected only after a 17 h-irradiation. Fv/Fm value of Chl a fluorescence measurements indicated that the photochemical efficiency of these leaves reached its maximum after 29 h of irradiation. The intersystem pool size of cotyledonary leaves was equivalent to that of the control cotyledonary leaves grown for 25 h under continuous irradiation. Thus etioplasts develop into fully functional chloroplasts after approximately 25 h when 4 d-dark grown cucumber seedlings are continuously moderately irradiated. The development of photosynthetic electron transport chain seems to be limited in time at the level of PS2, possibly at the donor side.
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    Effect of elevated temperature on natural killer cell and antibody-dependent cellular eytoboxieity
    (HALOCYNTHIA ASSOCIATION, 1998) Dubey, Uma S.
    Several studies have shown a direct correlation between temperature and immune response. The effect of elevated temperature on cytotoxic effector functions is not well known. In the present study we have investigated the effect of elevated temperatures (38.5 and 40 °C) on cytotoxicity of lymphokine-activated killer cells (LAK), monocyte cytotoxicity, cytotoxic T lymphocytes (CTL) and tumor necrosis factor (TNF)-mediated cytotoxicity, and compared them with results at 37°C. LAK cell cytotoxicity was inhibited significantly at 40°C (p < 0.01) and there was no marked difference at 38.5°C (p = 0.17) as compared to 37 °C when natural killer (NK)-sensitive K562 cells were used as target. When NK-resistant Raji cells were used as a target, cytotoxicity was inhibited at 40°C (p = 0.33). Monocyte cytotoxicity was enhanced at 40°C (p= 0.19) as well as at 38.5°C (p = 0.38) as compared to 37°C but differences
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    Factors regulating copper uptake in a cyanobacterium
    (Springer, 1990) Verma, Sanjay Kumar
    Copper uptake in the diazotrophic cyanobacteriumNostoc calcicola was found to be typically biphasic, comprising rapid binding of the cations to the cell wall (during the first 10 min) followed by the subsequent metabolism-dependent intracellular uptake for at least 1 h, with a curvilinear kinetics saturating at 40 µM (Km 25.0 µM, Vmax 3.0 nmol Cu mg−1 protein min−1). The cellular Cu uptake was light- and ATP-dependent, and the addition of 3(3,4-dichlorophenyl)-1,1-dimethylurea or exogenous ATP proved that the energy to drive Cu transport was derived mainly through PS II reactions. The application of metabolic inhibitors and uncouplers like carbonylcyanidep-nitrofluoromethoxylphenyl hydrazone, N,N′-dicyclohexycarbodiimide, azide, and p-chloromercuribenzoate revealed that -SH group(s), proton gradient across the cell membrane, and ATP hydrolysis were involved in the transmembrane movement of Cu inN. calcicola. While monothiol (2-mercaptoethanol) caused a twofold reduction in Cu uptake rate, dithiol (dithiothreitol) contributed towards a further drop in the cation uptake rate.
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