Influence of different wavelengths of light on photosynthesis and pigment constituents and absorption spectra of Gracilaria spp.

Three species of Graci/aria such as G.edulis, G. crassa and G. corticata were exposed to different broad band of lights. Red (> 600 nm), green (450-610 nm) and blue (390·570 nm) lights were provided to the plants kept in different growth chambers maintained with constant temperature of 28°C and photoperiod of 16:8 h light and dark period. The plants maintained under WL were considered as controL Photosynthetic activity and chlorophyll content were found to increase in all the species during 6th day of observation. Plants maintained GL exhibit higher cOIwentration of chlorophyll in G.edulis and G. corticata

Fatty acid profiles of marine red alga Gracilaria spp (Rhodophyta, Gigartinales)

Species of Graci/aria from Gulf of Mannar were analyzed for their fatty acid composition. The major fatty acids sllch as myristic acid, myristoleic acid. palmatic acid, paimiloleic acid, stearic acid, oleic acid and linoleic acid 'were ;nalyzcd by gas liquid chromatography. The qualitative and the quantitative di5tri bution of above fatty acids exhibited wide variation among the species of different habitat. The fatty acid content of the species collected from the same locality also showed quantitative variation depending on their distribution and the availability of light intensity to the particular specie

Effect of light intensity on the saturation of photosynthesis in Gracilana species (Rhodophyta)

Effect of light intensit}-on the saturated phtosynthcsis was studied in three different species of Graci/aria. Photosynthetic oxygen evolution reached saturation in the range of 15 to 30 ~ Elm1/sec. However, the saturation in G. crassa was observed at low intensity than G. edulis and G. corticota. The photosynthetic activity was found to be maximum in O. corticoiD. I~C02 uptake also showed maximum carbon fixed per unit fresh weight in G corlicala i.e., 21 .3 m mole I g. Fw I h as compared to 18.1 m mole I g. Fw I h in G. edulis and 17.9 m mole I g. Fw I h in G. corlicala

In vivo fluorescence kinetics of Gracilaria spp. subjected to different salinities

Gracilaria species were subjected to different salinities under laboratory conditions and changes in the photosynthetic oxygen evolution and fluorescence kinetics were followed. The plants which were subjected to more or less the normal salinity conditions exhibited low values of variable fluorescence and quantum yield. Prolonged treatment increased the quantum yield but the pigment content and the photosynthetic rate reduced significantly Among the two species tested, Gracilaria edulis was found to be very sensitive to low salinity (15 ppt) and G. crassa to higher salinity (45 ppt)

Determination of defense mechanism in ,i> Phaseolus trilobus Ait.seedlings treated under UV-B radiation

Field studies were conducted to determine the role of defense mechanism in various parameters associated with plant protection subjected to UV-B radiation in Phaseolus trilobus Ait. commonly used as green manure and fodder. Spectrophotometric analysis showed that UV-B radiation decreases the chlorophyll content and increased the amount of UV-B absorbing compounds such as anthocyanins and flavonoids. Other UV-induced alterations included reduction in fresh weight and leaf area. However, wrinkling of leaves and increased leaf thickness was observed in UV-B treated seedlings. The antioxidant enzymes were unaffected and showedenhanced activity, except catalase in UV-B treated seedlings. These results suggest that, in general, UV-B radiation caused oxidative damage. However, plants have evolved complex mechanisms to scavenge the activeoxygen species and thereby protect the cellular membrane, pigment and organelle

Effect of light intensity on leaf scorching in nursery seedlings of cardamom (Elettaria cardamomum Maton)

Studies on leaf scorching in nursery seedlings of cardamom (Elettaria cardamomum) grown at Thadiyankudisai (Tamil Nadu, India) indicated that total biomass, chlorophyll and protein contents, and photochemical activities were adversely affected in leaf scorched seedlings grown under full light (100% of total sunlight), when compared to healthy seedlings grown under medium light (45-55% of total sunlight). &nbsp

Transgenic neuronal overexpression reveals that stringently regulated p23 expression is critical for coordinated movement in mice

<p>Abstract</p> <p>Background</p> <p>p23 belongs to the highly conserved p24 family of type I transmembrane proteins, which participate in the bidirectional protein transport between the endoplasmic reticulum and Golgi apparatus. Mammalian p23 has been shown to interact with γ-secretase complex, and modulate secretory trafficking as well as intramembranous processing of amyloid precursor protein in cultured cells. Negative modulation of β-amyloid production by p23 in cultured cell lines suggested that elevation of p23 expression in neurons might mitigate cerebral amyloid burden.</p> <p>Results</p> <p>We generated several lines of transgenic mice expressing human p23 in neurons under the control of <it>Thy-1.2 </it>promoter. We found that even a 50% increase in p23 levels in the central nervous system of mice causes post-natal growth retardation, severe neurological problems characterized by tremors, seizure, ataxia, and uncoordinated movements, and premature death. The severity of the phenotype closely correlated with the level of p23 overexpression in multiple transgenic lines. While the number and general morphology of neurons in Hup23 mice appeared to be normal throughout the brain, abnormal non-Golgi p23 localization was observed in a subset of neurons with high transgene expression in brainstem. Moreover, detailed immunofluorescence analysis revealed marked proliferation of astrocytes, activation of microglia, and thinning of myelinated bundles in brainstem of Hup23 mice.</p> <p>Conclusions</p> <p>These results demonstrate that proper level of p23 expression is critical for neuronal function, and perturbing p23 function by overexpression initiates a cascade of cellular reactions in brainstem that leads to severe motor deficits and other neurological problems, which culminate in premature death. The neurological phenotype observed in Hup23 mice highlights significant adverse effects associated with manipulating neuronal expression of p23, a previously described negative modulator of γ-secretase activity and β-amyloid production. Moreover, our report has broader relevance to molecular mechanisms in several neurodegenerative diseases as it highlights the inherent vulnerability of the early secretory pathway mechanisms that ensure proteostasis in neurons.</p

Axonal BACE1 dynamics and targeting in hippocampal neurons: a role for Rab11 GTPase

BACKGROUND: BACE1 is one of the two enzymes that cleave amyloid precursor protein to generate Alzheimer's disease (AD) beta amyloid peptides. It is widely believed that BACE1 initiates APP processing in endosomes, and in the brain this cleavage is known to occur during axonal transport of APP. In addition, BACE1 accumulates in dystrophic neurites surrounding brain senile plaques in individuals with AD, suggesting that abnormal accumulation of BACE1 at presynaptic terminals contributes to pathogenesis in AD. However, only limited information is available on BACE1 axonal transport and targeting. RESULTS: By visualizing BACE1-YFP dynamics using live imaging, we demonstrate that BACE1 undergoes bi-directional transport in dynamic tubulo-vesicular carriers along axons in cultured hippocampal neurons and in acute hippocampal slices of transgenic mice. In addition, a subset of BACE1 is present in larger stationary structures, which are active presynaptic sites. In cultured neurons, BACE1-YFP is preferentially targeted to axons over time, consistent with predominant in vivo localization of BACE1 in presynaptic terminals. Confocal analysis and dual-color live imaging revealed a localization and dynamic transport of BACE1 along dendrites and axons in Rab11-positive recycling endosomes. Impairment of Rab11 function leads to a diminution of total and endocytosed BACE1 in axons, concomitant with an increase in the soma. Together, these results suggest that BACE1 is sorted to axons in endosomes in a Rab11-dependent manner. CONCLUSION: Our results reveal novel information on dynamic BACE1 transport in neurons, and demonstrate that Rab11-GTPase function is critical for axonal sorting of BACE1. Thus, we suggest that BACE1 transcytosis in endosomes contributes to presynaptic BACE1 localization