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61.
62.
Abstract: Production and metabolism of platelet-activating factor (PAF) in the fetal rat brain under normal and under ischemic stress conditions were examined. Endogenous PAF levels, determined by a bioassay using PAF-stimulated platelet release of [3H]serotonin, averaged 2.32 ± 2.14 pg/mg in control brains and was reduced to 1.10 ± 1.06 pg/mg after 20 min of maternal-fetal blood flow occlusion. [3H]PAF administered intracranially into the fetuses in utero was removed in a biphasic, time-dependent manner: a rapid component with an estimated elimination rate constant of 0.067 min?1 and t1/2 of 10 min and a slower component with an elimination rate of 0.017 min?1 and t1/2 of 41 min. In fetal brains subjected to ischemia a delayed elimination of [3H]PAF was noticed in the slow component (t1/2 = 59 min), indicating a possible difference between the clearance of exogenous and endogenous PAF. The disappearance of [3H]PAF was accompanied by an increase in the radioactivity associated with lyso-PAF that reached a plateau after 2.5 min, possibly indicating the degradation of the fast component. A steady increase in the alkyl-acyl-glycerophosphorylcholine radioactivity commenced after 5 min and continued up to 30 min. The endogenous production of PAF and the rapid degradation due to maternal-fetal blood flow occlusion indicate an additional target for therapeutic intervention in the pathology of intrauterine ischemia. Addition of the calcium ionophore A23187 stimulated in vitro formation of PAF and lyso-PAF from [3H]-choline-labeled fetal brain phospholipids, suggesting that intracellular calcium may play a major stimulatory role in PAF production. Degradation of polyphosphoinositides by a phospholipase C may constitute a major target for PAF generated either by decapitation or after blood flow occlusion, as evident from the protective effect of the in vivo administered BN52021 PAF antagonist. 相似文献
63.
The effect of amyloid (A), the major constituent of the Alzheimer's (AD) brain on lipid metabolism was investigated in cultured nerve cells and in a fetal rat brain model. Differentiated (NGF) and undifferentiated PC12 cells or primary cerebral cell cultures were incubated with [14C]acetate in the absence or presence of A1–40. Incorporation of label into lipid species was determined after lipid extraction and TLC separation. Phosphatidylcholine (PC) and phosphatidylserine (PS) synthesis was increased by A1–40, in a dose dependent manner, an effect which was more pronounced in differentiated PC12 cells. A significant proportion of radioactivity (5–6%) was released into the medium with a radioactivity distribution similar to that of the cellular lipids. Cholesterol and PC were the highest labeled medium lipids. Increasing A1–40 concentration up to 0.1 g/ml in cerebral cells but not in PC12 cells, caused a relative increase (1.5 fold) in release of PS, while that of PE decreased. Stimulation of PS release may possibly be associated with apoptotic cell death. A1–40 peptide (5 g) was administered intraperitonealy into rat fetuses (18 days gestation) along with [14C]acetate (2Ci/fetus). After 24 h, the maternal-fetal blood supply was occluded for 20 min (ischemia) followed by 15 min reperfusion. Fetuses were killed and liver and brain tissue subjected to lipid extraction and radioactivity determination after TLC. A1–40 peptide increased synthesis of different classes of lipids up to 20–40% in brain tissue compared to controls. Labeling of liver lipids was decreased by A1–40 by 20–30%. A general decrease in synthesis of lipids was observed after ischemia/reperfusion. Our data suggest that A1–40 peptide regulates normal lipid biosynthesis but under ischemia it compromises it. The latter finding may confirm the oxidative stress etiology in AD and suggests that A1–40 modulation of lipid metabolism may have Alzheimer's pathological relevance, particularly at high peptide concentrations. 相似文献
64.
Understanding animal movement and resource selection provides important information about the ecology of the animal, but an animal's movement and behavior are not typically constant in time. We present a velocity-based approach for modeling animal movement in space and time that allows for temporal heterogeneity in an animal's response to the environment, allows for temporal irregularity in telemetry data, and accounts for the uncertainty in the location information. Population-level inference on movement patterns and resource selection can then be made through cluster analysis of the parameters related to movement and behavior. We illustrate this approach through a study of northern fur seal (Callorhinus ursinus) movement in the Bering Sea, Alaska, USA. Results show sex differentiation, with female northern fur seals exhibiting stronger response to environmental variables. 相似文献
65.
TMPRSS2/ERG promotes epithelial to mesenchymal transition through the ZEB1/ZEB2 axis in a prostate cancer model 总被引:1,自引:0,他引:1
66.
Pete Smith Katherine Calvin Johnson Nkem Donovan Campbell Francesco Cherubini Giacomo Grassi Vladimir Korotkov Anh Le Hoang Shuaib Lwasa Pamela McElwee Ephraim Nkonya Nobuko Saigusa Jean‐Francois Soussana Miguel Angel Taboada Frances C. Manning Dorothy Nampanzira Cristina Arias‐Navarro Matteo Vizzarri Jo House Stephanie Roe Annette Cowie Mark Rounsevell Almut Arneth 《Global Change Biology》2020,26(3):1532-1575
There is a clear need for transformative change in the land management and food production sectors to address the global land challenges of climate change mitigation, climate change adaptation, combatting land degradation and desertification, and delivering food security (referred to hereafter as “land challenges”). We assess the potential for 40 practices to address these land challenges and find that: Nine options deliver medium to large benefits for all four land challenges. A further two options have no global estimates for adaptation, but have medium to large benefits for all other land challenges. Five options have large mitigation potential (>3 Gt CO2eq/year) without adverse impacts on the other land challenges. Five options have moderate mitigation potential, with no adverse impacts on the other land challenges. Sixteen practices have large adaptation potential (>25 million people benefit), without adverse side effects on other land challenges. Most practices can be applied without competing for available land. However, seven options could result in competition for land. A large number of practices do not require dedicated land, including several land management options, all value chain options, and all risk management options. Four options could greatly increase competition for land if applied at a large scale, though the impact is scale and context specific, highlighting the need for safeguards to ensure that expansion of land for mitigation does not impact natural systems and food security. A number of practices, such as increased food productivity, dietary change and reduced food loss and waste, can reduce demand for land conversion, thereby potentially freeing‐up land and creating opportunities for enhanced implementation of other practices, making them important components of portfolios of practices to address the combined land challenges. 相似文献
67.
The use of numerical simulation as a means to predict the outcome of transurethral microwave thermotherapy (TUMT) is set forth in detail. The simulation was carried out as a case study of a specific TUMT procedure. The selection of the case study was based on the availability of extensive medical records which documented an extraordinary application of TUMT. Predictions were made of the time-varying temperature patterns within the prostate, the bladder, the sphincter, the pelvic floor, and the fat and connective tissue which envelop these organs. These temperature patterns provided the basis of maps which highlighted those locations where necrosis occurred. An injury integral was used to predict the extent of the necrotic tissue produced by the therapy. It was found that, for the specific case being considered, necrosis occurred not only within the prostate but also extended to the neck of the bladder and to the fatty tissue. A special feature of the simulation was the accounting of the liquid-to-vapor phase change of the interstitial water. The vapor generated by the phase change is believed to significantly enlarge the region of necrosis. By the same token, the vapor pressure is expected to cause motion of the high-temperature liquid to deep-tissue regions. The damage predicted by the numerical simulation was compared, in detail, with post-operative medical examinations and found to be corroborated. 相似文献
68.
The effect of docosahexaenoic acid (DHA; 22:6 n–3) on Fe2+-mediated and/or H2O2-mediated oxidative stress (OS) was investigated in a PC12 pheochromocytoma cell line in the presence or absence of 50 ng/ml
nerve growth factor (NGF). DHA-supplemented cells showed enhanced Fe2+-induced cell damage as evident by increased lipid peroxides formation (10-fold) and reduced neutral red (NR) dye uptake in
a NGF-independent fashion. DHA caused a nearly 10-fold increase in free iron uptake in NGF-treated cells and doubled iron
uptake in nondifferentiated cells. DHA-enrichment induced an elevation in the transferrin receptor protein in the nondifferentiated
cells whereas NGF-treatment led to a substantial increase in the ubiquitous divalent metal ion transporter 1 (DMT-1) as detected
by mRNA levels using qRT-PCR. The mechanism of action of DHA to accelerate cell death may be associated with the externalization
of amino-phosphoglycerides (PG) species of which, increased ethanolamine plasmalogen levels, may be essential for cell rescue
as noted in NGF-treated PC12 cells.
Special issue dedicated to Dr. Moussa Youdim.
Equal scientific input of ES and AB. 相似文献
69.
Computational fluid dynamics techniques employing primarily steady Reynolds-Averaged Navier-Stokes (RANS) methodology have been recently used to characterize the transitional/turbulent flow field in human airways. The use of RANS implies that flow phenomena are averaged over time, the flow dynamics not being captured. Further, RANS uses two-equation turbulence models that are not adequate for predicting anisotropic flows, flows with high streamline curvature, or flows where separation occurs. A more accurate approach for such flow situations that occur in the human airway is Large Eddy Simulation (LES). The paper considers flow modeling in a pharyngeal airway model reconstructed from cross-sectional magnetic resonance scans of a patient with obstructive sleep apnea. The airway model is characterized by a maximum narrowing at the site of retropalatal pharynx. Two flow-modeling strategies are employed: steady RANS and the LES approach. In the RANS modeling framework both k-epsilon and k-omega turbulence models are used. The paper discusses the differences between the airflow characteristics obtained from the RANS and LES calculations. The largest discrepancies were found in the axial velocity distributions downstream of the minimum cross-sectional area. This region is characterized by flow separation and large radial velocity gradients across the developed shear layers. The largest difference in static pressure distributions on the airway walls was found between the LES and the k-epsilon data at the site of maximum narrowing in the retropalatal pharynx. 相似文献
70.
Jutta Ludwig-Müller Alexander Walz Janet P. Slovin Ephraim Epstein Jerry D. Cohen Weiqin Dong Christopher D. Town 《Journal of Plant Growth Regulation》2005,24(2):127-141
Overexpression of the IAGLU gene from maize (ZmIAAGLU) in Arabidopsis thaliana, under the control of the CaMV 35S promoter, inhibited root but not hypocotyl growth of seedlings in four different transgenic
lines. Although hypocotyl growth of seedlings and inflorescence growth of mature plants was not affected, the leaves of mature
plants were smaller and more curled as compared to wild-type and empty vector transformed plants. The rosette diameter in
transgenic lines with higher ZmIAGLU expression was also smaller compared to the wild type. Free indole-3-acetic acid (IAA) levels in the transgenic plants were
comparable to the wild type, even though a decrease in free IAA levels might be expected from overexpression of an IAA-conjugate–forming
enzyme. IAA-glucose levels, however, were increased in transgenic lines compared to the wild type, indicating that the ZmIAGLU gene product is active in these plants. In addition, three different 35SZmIAGLU lines showed less inhibition of root growth when cultivated on increasing concentrations of IAA but not indole-3-butyric
acid (IBA) and 2,4-dichlorophenoxyacetic acid (2,4-D). Feeding IAA to transgenic lines resulted in increased IAA-glucose synthesis,
whereas the levels of IAA-aspartate and IAA-glutamine formed were reduced compared to the wild type. Our results show that
IAA homeostasis can be altered by heterologous overexpression of a conjugate-forming gene from maize. 相似文献