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31.
Intraventricular infusion of rats with beta-amyloid for 14 days resulted in memory deficit in the water maze as well as decreases in choline acetyltransferase activities and somatostatin levels in the cerebral cortex and hippocampus. These changes were not altered by daily intraperitoneal injection of 20 mg/Kg melatonin. Orally administered Ginkgo biloba extract, however, partially reversed the memory deficit and the decrease in choline actyltransferase activities in the hippocampus. The latter treatment failed to reverse the decrease in somatostatin levels. The results indicate that orally administered Ginkgo biloba extract can protect the brain against beta-amyloid from changes leading to memory deficit through its effect on the cholinergic system. 相似文献
32.
The expansion of trinucleotide repeat sequences associated with hereditary neurological diseases is believed from earlier studies to be due to errors in DNA replication. However, more recent studies have indicated that recombination may play a significant role in triplet repeat expansion. CAG repeat tracts have been shown to induce double-strand breaks (DSBs) during meiosis in yeast, and DSB formation is dependent on the meiotic recombination machinery. The rate of meiotic instability is several fold higher than mitotic instability. To determine whether DSB repair is responsible for the high rate of repeat tract-length alterations, the frequencies of meiotic repeat-tract instability were compared in wild-type and spo11 mutant strains. In the spo11 background, the rate of meiotic repeat-tract instability remained at the mitotic level, suggesting that meiotic alterations of CAG repeat tracts in yeast occur by the recombination mechanism. Several of these meiotic tract-length alterations are due to DSB repair involving use of the sister chromatid as a template. 相似文献
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34.
Nag K Pao JS Harbottle RR Possmayer F Petersen NO Bagatolli LA 《Biophysical journal》2002,82(4):2041-2051
The physical properties of organized system (bilayers and monolayers at the air water interface) composed of bovine lipid extract surfactant (BLES) were studied using correlated experimental techniques. 6-Dodecanoyl-2-dimethylamino-naphthalene (LAURDAN)-labeled giant unilamelar vesicles (mean diameter approximately 30 microm) composed of BLES were observed at different temperatures using two-photon fluorescence microscopy. As the temperature was decreased, dark domains (gel-like) appeared at physiological temperature (37 degrees C) on the surface of BLES giant unilamelar vesicles. The LAURDAN two-photon fluorescent images show that the gel-like domains span the lipid bilayer. Quantitative analysis of the LAURDAN generalized polarization function suggests the presence of a gel/fluid phase coexistence between 37 degrees C to 20 degrees C with low compositional and energetic differences between the coexisting phases. Interestingly, the microscopic scenario of the phase coexistence observed below 20 degrees C shows different domain's shape compared with that observed between 37 degrees C to 20 degrees C, suggesting the coexistence of two ordered but differently organized lipid phases on the bilayer. Epifluorescence microscopy studies of BLES monomolecular films doped with small amounts of fluorescent lipids showed the appearance and growth of dark domains (liquid condensed) dispersed in a fluorescent phase (liquid expanded) with shapes and sizes similar to those observed in BLES giant unilamelar vesicles. Our study suggests that bovine surfactant lipids can organize into discrete phases in monolayers or bilayers with equivalent temperature dependencies and may occur at physiological temperatures and surface pressures equivalent to those at the lung interface. 相似文献
35.
Panda AK Hume A Nag K Harbottle RR Petersen NO 《Indian journal of biochemistry & biophysics》2003,40(2):114-121
Structures of the monolayer films of dipalmitoylphosphatidylcholine (DPPC) mixed with different amounts of cholesterol were studied at air-water interface using surface pressure-area measurements, epifluorescence microscopy and atomic force microscopy (AFM). Pure DPPC, cholesterol or DPPC-cholesterol mixtures were dissolved in organic solvents with a small amount of fluorescently labeled phospholipid probe (NBD-PC) and spread onto the air-water interface. Surface pressure-area isotherms and epifluorescence microscopy of such films at the air-water interface suggested that DPPC undergoes a gas to fluid to condensed phase transition, while cholesterol undergoes a gas to solid-like transition. A shift of the surface pressure-area curve to lower area per molecule was observed when cholesterol was mixed with DPPC. Epifluorescence microscopy showed the formation of spiral shaped domains for mixed monolayers. Increase in cholesterol content abolished domain characteristics possibly due to fluidizing property of cholesterol. AFM measurements of monolayers, transferred onto freshly cleaved mica by Langmuir-Blodgett technique, revealed the alterations caused by cholesterol on the gel and fluid domains of such films. AFM measurements re-established similar trend in domain characteristics as evidenced in epifluorescence microscopy. 相似文献
36.
Barthwal MK Srivastava N Nag D Seth PK Srimal RC Dikshit M 《Redox report : communications in free radical research》2000,5(2-3):75-80
Protective effects of NOS inhibitors and free radical scavengers in cerebral ischemia are well documented. The present study was undertaken to determine the possible effects of NOS inhibition on brain antioxidants. Levels of both enzymatic [glutathione peroxidase (GPx), catalase and superoxide dismutase (SOD)] and non-enzymatic [reduced glutathione (GSH)] antioxidants following nitric oxide synthase (NOS) inhibition by N(G)-nitro-L-arginine methyl ester (L-NAME), D-NAME or 7-nitroindazole (7-NI) have been investigated. NOS activity and antioxidant levels in the rat cerebellum and medulla were estimated 1 h after treatment with L-NAME (10, 30 and 100 mg/kg, i.p.), D-NAME (100 mg/kg, i.p.) or 7-NI (25 mg/kg, i.p.). L-NAME and 7-NI inhibited NOS activity in a dose-dependent manner. D-NAME also exhibited significant NOS inhibition. The activity of SOD and the GSH level remained unaltered following NOS inhibition. However, L-NAME and D-NAME at 100 mg/kg attenuated GPx activity in the cerebellum, though 7-NI had no effect. L-NAME inhibited catalase activity in medulla only at 30 mg/kg, but had no effect in cerebellum. However, 7-NI (25 mg/kg), D-NAME and L-NAME at 100 mg/kg did not affect catalase activity in the rat brain. Thus, NOS inhibition by the three agents did not have major effects on brain antioxidant levels. 相似文献
37.
Parameter determination and validation for a mechanistic model of the enzymatic saccharification of cellulose‐Iβ 下载免费PDF全文
Ambarish Nag Michael A. Sprague Andrew J. Griggs James J. Lischeske Jonathan J. Stickel Ashutosh Mittal Wei Wang David K. Johnson 《Biotechnology progress》2015,31(5):1237-1248
Cost‐effective production of fuels and chemicals from lignocellulosic biomass often involves enzymatic saccharification, which has been the subject of intense research and development. Recently, a mechanistic model for the enzymatic saccharification of cellulose has been developed that accounts for distribution of cellulose chain lengths, the accessibility of insoluble cellulose to enzymes, and the distinct modes of action of the component cellulases [Griggs et al. (2012) Biotechnol. Bioeng., 109(3):665–675; Griggs et al. (2012) Biotechnol. Bioeng., 109(3):676–685]. However, determining appropriate values for the adsorption, inhibition, and rate parameters required further experimental investigation. In this work, we performed several sets of experiments to aid in parameter estimation and to quantitatively validate the model. Cellulosic materials differing in degrees of polymerization and crystallinity (α‐cellulose‐Iβ and highly crystalline cellulose‐Iβ) were digested by component enzymes (EGI/CBHI/ ) and by mixtures of these enzymes. Based on information from the literature and the results from these experiments, a single set of model parameters was determined, and the model simulation results using this set of parameters were compared with the experimental data of total glucan conversion, chain‐length distribution, and crystallinity. Model simulations show significant agreement with the experimentally derived glucan conversion and chain‐length distribution curves and provide interesting insights into multiple complex and interacting physico‐chemical phenomena involved in enzymatic hydrolysis, including enzyme synergism, substrate accessibility, cellulose chain length distribution and crystallinity, and inhibition of cellulases by soluble sugars. © 2015 American Institute of Chemical Engineers Biotechnol. Prog., 31:1237–1248, 2015 相似文献
38.
Zebrafish can repair their injured brain and spinal cord after injury unlike adult mammalian central nervous system. Any injury to zebrafish spinal cord would lead to increased proliferation and neurogenesis. There are presences of proliferating progenitors from which both neuronal and glial loss can be reversed by appropriately generating new neurons and glia. We have demonstrated the presence of multiple progenitors, which are different types of proliferating populations like Sox2+ neural progenitor, A2B5+ astrocyte/ glial progenitor, NG2+ oligodendrocyte progenitor, radial glia and Schwann cell like progenitor. We analyzed the expression levels of two common markers of dedifferentiation like msx-b and vimentin during regeneration along with some of the pluripotency associated factors to explore the possible role of these two processes. Among the several key factors related to pluripotency, pou5f1 and sox2 are upregulated during regeneration and associated with activation of neural progenitor cells. Uncovering the molecular mechanism for endogenous regeneration of adult zebrafish spinal cord would give us more clues on important targets for future therapeutic approach in mammalian spinal cord repair and regeneration. 相似文献
39.
We describe the morphology of toe pads in the Himalayan tree frog Philautus annandalii. These are expanded tips of digits and show modifications of their ventral epidermis for adhesion. The outer cells of toe pad epidermis (TPE) bear surface microstructures (0.7 × 0.2 μm), which are keratinized. Their cytoplasm contains no organelles, but pleomorphic nuclei and mucous granules (0.4–0.5 μm) that glue the keratin filaments. In the intermediate cell layer of TPE, similar keratinized microstructures as in the outer cells are present, so that when the outer layer is shed, it is ready with features for adhesion. These cells contain more keratin than the outer cells. The basal cell layer contains thin keratin bundles and usual cell organelles. The dermis contains mucous‐secreting glands, whose ducts open in the outer epidermal cell layer in channels. The dorsal epidermal cells lack surface microstructures and keratin bundles. Ultrastructural features suggest that toe pads utilize the surface microstructures for adhesion aided by mucus, in which the intermediate cell layer seems to bear the shear stress generated during locomotion. Further, TPE can expand and fit into an increased contact area of the substrate. The long, surface microstructures may also help in mechanical interlocking with rough surfaces on plants. 相似文献
40.
Balázs Gulyás Damian Brockschnieder Sangram Nag Elena Pavlova Péter Kása Zsuzsa Beliczai Ádám Légrádi Károly Gulya Andrea Thiele Thomas Dyrks Christer Halldin 《Neurochemistry international》2010,56(6-7):789-798
Earlier post-mortem histological and autoradiographic studies have indicated a reduction of cell numbers in the locus coeruleus (LC) and a corresponding decrease in norepinephrine transporter (NET) in brains obtained from Alzheimer's disease (AD) patients as compared to age-matched healthy controls. In order to test the hypothesis that the regional decrease of NET is a disease specific biomarker in AD and as such, it can be used in PET imaging studies for diagnostic considerations, regional differences in the density of NET in various anatomical structures were measured in whole hemisphere human brain slices obtained from AD patients and age-matched control subjects in a series of autoradiographic experiments using the novel selective PET radioligand for NET (S,S)-[18F]FMeNER-D2. (S,S)-[18F]FMeNER-D2 appears to be a useful imaging biomarker for quantifying the density of NET in various brain structures, including the LC and the thalamus wherein the highest densities are found in physiological conditions. In AD significant decreases of NET densities can be demonstrated with the radioligand in both structures as compared to age-matched controls. The decreases in AD correlate with the progress of the disease as indicated by Braak grades. As the size of the LC is below the spatial resolution of the PET scanners, but the size of the thalamus can be detected with appropriate spatial accuracy in advanced scanners, the present findings confirm our earlier observations with PET that the in vivo imaging of NET with (S,S)-[18F]FMeNER-D2 in the thalamus is viable. Nevertheless, further studies are warranted to assess the usefulness of such an imaging approach for the early detection of changes in thalamic NET densities as a disease-specific biomarker and the possible use of (S,S)-[18F]FMeNER-D2 as a molecular imaging biomarker in AD. 相似文献