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1.
Nicole LeBrasseur 《The Journal of cell biology》2003,162(6):958-959
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The characteristics of the inducible galactose transport system in bakers' yeast were studied in uridine diphosphate, galactose-1-phosphate uridylyl-transferaseless cells. Transferaseless cells transport galactose at the same initial rate as wild-type cells and accumulate a mixture of free galactose and galactose-1-phosphate. The addition of 14C-labeled galactose to cells preloaded with unlabeled galactose and galactose-1-phosphate results in a higher rate of labeling of the free-sugar pool than of the galactose-1-phosphate pool. These results support other evidence that galactose uptake in bakers' yeast is a carrier-mediated, facilitated diffusion and that phosphorylation is an intracellular event after uptake of the free sugar. 相似文献
3.
Thomas A. Worthington Shannon K. Brewer Nicole Farless Timothy B. Grabowski Mark S. Gregory 《PloS one》2014,9(5)
Habitat fragmentation and flow regulation are significant factors related to the decline and extinction of freshwater biota. Pelagic-broadcast spawning cyprinids require moving water and some length of unfragmented stream to complete their life cycle. However, it is unknown how discharge and habitat features interact at multiple spatial scales to alter the transport of semi-buoyant fish eggs. Our objective was to assess the relationship between downstream drift of semi-buoyant egg surrogates (gellan beads) and discharge and habitat complexity. We quantified transport time of a known quantity of beads using 2–3 sampling devices at each of seven locations on the North Canadian and Canadian rivers. Transport time was assessed based on median capture time (time at which 50% of beads were captured) and sampling period (time period when 2.5% and 97.5% of beads were captured). Habitat complexity was assessed by calculating width∶depth ratios at each site, and several habitat metrics determined using analyses of aerial photographs. Median time of egg capture was negatively correlated to site discharge. The temporal extent of the sampling period at each site was negatively correlated to both site discharge and habitat-patch dispersion. Our results highlight the role of discharge in driving transport times, but also indicate that higher dispersion of habitat patches relates to increased retention of beads within the river. These results could be used to target restoration activities or prioritize water use to create and maintain habitat complexity within large, fragmented river systems. 相似文献
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Shreaya Chakroborty Clark Briggs Megan B. Miller Ivan Goussakov Corinne Schneider Joyce Kim Jaime Wicks Jill C. Richardson Vincent Conklin Benjamin G. Cameransi Grace E. Stutzmann 《PloS one》2012,7(12)
Alzheimer’s disease (AD) is a devastating neurodegenerative condition with no known cure. While current therapies target late-stage amyloid formation and cholinergic tone, to date, these strategies have proven ineffective at preventing disease progression. The reasons for this may be varied, and could reflect late intervention, or, that earlier pathogenic mechanisms have been overlooked and permitted to accelerate the disease process. One such example would include synaptic pathology, the disease component strongly associated with cognitive impairment. Dysregulated Ca2+ homeostasis may be one of the critical factors driving synaptic dysfunction. One of the earliest pathophysiological indicators in mutant presenilin (PS) AD mice is increased intracellular Ca2+ signaling, predominantly through the ER-localized inositol triphosphate (IP3) and ryanodine receptors (RyR). In particular, the RyR-mediated Ca2+ upregulation within synaptic compartments is associated with altered synaptic homeostasis and network depression at early (presymptomatic) AD stages. Here, we offer an alternative approach to AD therapeutics by stabilizing early pathogenic mechanisms associated with synaptic abnormalities. We targeted the RyR as a means to prevent disease progression, and sub-chronically treated AD mouse models (4-weeks) with a novel formulation of the RyR inhibitor, dantrolene. Using 2-photon Ca2+ imaging and patch clamp recordings, we demonstrate that dantrolene treatment fully normalizes ER Ca2+ signaling within somatic and dendritic compartments in early and later-stage AD mice in hippocampal slices. Additionally, the elevated RyR2 levels in AD mice are restored to control levels with dantrolene treatment, as are synaptic transmission and synaptic plasticity. Aβ deposition within the cortex and hippocampus is also reduced in dantrolene-treated AD mice. In this study, we highlight the pivotal role of Ca2+ aberrations in AD, and propose a novel strategy to preserve synaptic function, and thereby cognitive function, in early AD patients. 相似文献
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Matthew E. Downs Amanda Buch Carlos Sierra Maria Eleni Karakatsani Shangshang Chen Elisa E. Konofagou Vincent P. Ferrera 《PloS one》2015,10(5)
Focused Ultrasound (FUS) coupled with intravenous administration of microbubbles (MB) is a non-invasive technique that has been shown to reliably open (increase the permeability of) the blood-brain barrier (BBB) in multiple in vivo models including non-human primates (NHP). This procedure has shown promise for clinical and basic science applications, yet the safety and potential neurological effects of long term application in NHP requires further investigation under parameters shown to be efficacious in that species (500kHz, 200–400 kPa, 4–5μm MB, 2 minute sonication). In this study, we repeatedly opened the BBB in the caudate and putamen regions of the basal ganglia of 4 NHP using FUS with systemically-administered MB over 4–20 months. We assessed the safety of the FUS with MB procedure using MRI to detect edema or hemorrhaging in the brain. Contrast enhanced T1-weighted MRI sequences showed a 98% success rate for openings in the targeted regions. T2-weighted and SWI sequences indicated a lack edema in the majority of the cases. We investigated potential neurological effects of the FUS with MB procedure through quantitative cognitive testing of’ visual, cognitive, motivational, and motor function using a random dot motion task with reward magnitude bias presented on a touchpanel display. Reaction times during the task significantly increased on the day of the FUS with MB procedure. This increase returned to baseline within 4–5 days after the procedure. Visual motion discrimination thresholds were unaffected. Our results indicate FUS with MB can be a safe method for repeated opening of the BBB at the basal ganglia in NHP for up to 20 months without any long-term negative physiological or neurological effects with the parameters used. 相似文献
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