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131.
T Azuma W Witke TP Stossel JH Hartwig DJ Kwiatkowski 《Canadian Metallurgical Quarterly》1998,17(5):1362-1370
Rac, a member of the rho family of GTPases, when activated transmits signals leading to actin-based membrane ruffling in fibroblasts. Compared with wild-type fibroblasts, gelsolin null (Gsn-) dermal fibroblasts have a markedly reduced ruffling response to serum or EGF stimulation, which signal through rac. Bradykinin-induced filopodial formation, attributable to activation of cdc42, is similar in both cell types. Wild-type fibroblasts exhibit typical lamellipodial extension during translational locomotion, whereas Gsn- cells move 50% slower using structures resembling filopodia. Multiple Gsn- tissues as well as Gsn- fibroblasts overexpress rac, but not cdc42 or rho, 5-fold. Re-expression of gelsolin in Gsn- fibroblasts by stable transfection or adenovirus reverts the ruffling response, translational motility and rac expression to normal. Rac migrates to the cell membrane following EGF stimulation in both cell types. Gelsolin is an essential effector of rac-mediated actin dynamics, acting downstream of rac recruitment to the membrane. 相似文献
132.
We investigated the behavior of the antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APx), in potato tubers during storage at low temperature. SOD activity increased temporarily within 3 weeks and was higher at 1 degree C than at 20 degrees C. APx activity also increased more at low (1 degree C) than at higher temperatures (5 and 20 degrees C). The contents of ascorbic acid (AsA), which is the substrate of APx, decreased immediately within 3 weeks and then gradually decreased until 15 weeks. The activity of CAT, the other enzyme which can scavenge hydrogen peroxide, decreased once in the first six weeks and thereafter increased to 15 weeks. Thus, the enhancement of the active oxygen-scavenging system that was induced by low temperature in potato tubers could result not only in a decrease of AsA but also in combined increases in APx and CAT activity whose manners were different. 相似文献
133.
We report a family in which three siblings developed dementia between the ages of 40 and 70 years. Two of the siblings developed symptoms of depression, abnormal behavior, and an inability to function, progressing to severe dementia. The third sibling had a severe dementia, the clinical details of which are not available. In the two deceased siblings neuropathologic examinations demonstrated severe demyelination, axon loss, and gliosis in cerebral white matter. Cerebellar and brainstem white matter were unaffected. Cerebral gray matter was negligibly affected. The disorder, histopathologically classified as a pigmented orthochromatic leukodystrophy, is extremely rare. Its etiology is unknown, but the pathology and familial occurrence imply that it represents a genetic defect in a function localized in the cerebral white matter. 相似文献
134.
OBJECTIVE: To examine the utility of single breath CO2 analysis as a noninvasive measure of cardiac output. SETTING: An animal laboratory in a university-affiliated medical center. DESIGN: A prospective, animal cohort study comparing 21 parameters derived from single breath CO2 analysis with cardiac output determined by an ultrasonic flow probe. SUBJECTS: Six healthy adult sheep. METHODS: The single breath CO2 analysis station consists of a mainstream capnometer, a variable orifice pneumotachometer, a signal processor, and computer software with capability for both on- and off-line data analysis. Twenty-one derived components of the CO2 expirogram were evaluated as predictors of cardiac output. Cardiac output was manipulated by successive injections of a hydraulic constrictor placed around the inferior vena cava. MEASUREMENTS AND MAIN RESULTS: Thirty-four measurements of cardiac output were available for comparison with derived variables from the CO2 expirogram. Stepwise linear regression identified two variables that were most predictive of cardiac output: a) the angle between the slope lines for phase II and III of the CO2 expirogram divided by the volume of CO2 per breath (angle/mL CO2); and b) the slope of phase II. The multivariate equation was highly statistically significant and explained 94% of the variance (adjusted r2 = .94, p < .0001). The bias and precision of the calculated cardiac output were .00 and .23, respectively. The mean percent difference for the cardiac output estimate derived from the single breath CO2 analysis station was 0.36%. CONCLUSIONS: Our data indicate that analysis of the CO2 expirogram can yield accurate information about the cardiovascular system. Specifically, two variables derived from a plot of expired CO2 concentration vs. expired volume predict changes in cardiac output in healthy adult sheep with an adjusted coefficient of determination of .94. Prospective application of this technology in the setting of lung injury and rapidly changing physiology will be essential in determining the clinical usefulness of the technique. 相似文献
135.
136.
GZ Markarian JH Lee DJ Stein SC Hong 《Canadian Metallurgical Quarterly》1996,38(3):542-50; discussion 551
The treatment of cerebral ischemia remains a formidable challenge in neuroscience today. Mild hypothermia has been shown to be an effective neuroprotective agent. Despite the great volume of published research, the therapeutic window of mild hypothermia has not been precisely elucidated. Using a model of reversible focal cerebral ischemia in the rat, this study was undertaken to define the optimal duration of hypothermic application and the maximal postischemic delay in hypothermic application before which optimal therapeutic effect is noted. Focal ischemia was induced by temporary occlusion of the middle cerebral artery and both carotid arteries in Sprague-Dawley rats for a period of 3 hours. In the first study, mild hypothermia (32-33 degrees C) was induced at the onset of ischemia in four groups of rats for varying lengths of time ranging from 1 to 4 hours. The animals were killed after 3 days, and their brains were sliced and stained. Infarcted volume was measured using a computerized image analyzer. The infarct volumes were 211 +/- 4.5, 214.2 +/- 8.0, 199.5 +/- 5.3, 171.3 +/- 9.1, and 169.8 +/- 6.5 mm3 (mean +/- standard error of the mean, n = 6 per group) for the control, 1-hour, 2-hour, 3-hour, and 4-hour groups, respectively. On the basis of the results from the above study, a 3-hour duration of hypothermia was then applied to animals at 0, 15, 30, or 45 minutes after the ischemic onset. The volumes of infarction for these four respective groups were: 171.3 +/- 9.1, 173 +/- 5.7, 179.3 +/- 5.2, and 206.2 +/- 8.4 mm3 (mean +/- standard error of the mean, n = 6 per group). These results demonstrated that optimal duration of mild hypothermia was at least 3 hours (P < 0.001) when applied within the first 30 minutes after the onset of ischemia (P < 0.001). 相似文献
137.
GP Xue JS Johnson DJ Smyth LM Dierens X Wang GD Simpson KS Gobius JH Aylward 《Canadian Metallurgical Quarterly》1996,45(1-2):120-126
Temperature-regulated expression of recombinant proteins in the tac promoter (Ptac) system was investigated. Expression levels of fungal xylanase and cellulase from N. patriciarum in E. coli strains containing the natural lacI gene under the control of the Ptac markedly increased with increasing cultivation temperature in the absence of a chemical inducer. The specific activities (units per milligram protein of crude enzyme) of the fungal xylanase and cellulase produced from recombinant E. coli strain pop2136 grown at 42 degrees C were about 4.5 times higher than those of the cells grown at 23 degrees C and were even slightly higher when compared with cells grown in the presence of the inducer isopropyl beta-D-thiogalactopyranoside. The xylanase expression level in the temperature-regulated Ptac system was about 35% of total cellular protein. However, this system can not be applied to E. coli strains containing lacIq, which confers over production of the lac repressor, for high-level expression of recombinant proteins. In comparison with the lambda PL system, the Ptac-based xylanase plasmid in E. coli pop2136 gave a considerably higher specific activity of the xylanase than did the best lambda PL-based construct using the same thermal induction procedure. The high-level expression of the xylanase using the temperature-regulated Ptac system was also obtained in 10-litre fermentation studies using a fed-batch process. These results unambiguously demonstrated that the temperature-modulated Ptac system can be used for overproduction of some non-toxic recombinant proteins. 相似文献
138.
M Fein JH Peters P Chandrasoma AP Ireland S Oberg MP Ritter CG Bremner JA Hagen TR DeMeester 《Canadian Metallurgical Quarterly》1998,2(3):260-268
Central nervous system (CNS) disease is a major feature of simian immunodeficiency virus (SIV) infection of macaques. To define the spectrum of CNS lesions in SIV-infected macaques and the potential associations with viral strain and disease course, we performed a retrospective analysis of necropsies on 124 macaques with SIV-induced AIDS. Histologic evidence of CNS disease was observed in 71 (57.3%) of the 124 animals. SIV encephalitis was the most common CNS lesion occurring in 43.7% (31/71) of the animals with CNS disease and 25% of all animals. The incidence of SIVE correlated significantly with shortened survival (P=0.0207). In addition, SIVE was seen in 42.9% (15/35) of rapid progressors (animals that died within 200 days) compared to only 18% (16/89) of normal progressors (animals that lived longer than 200 days) (P=0.011). Animals with SIVE had higher viral loads in peripheral blood than those that did not, but this difference did not reach statistical significance. Similarly, while animals infected with uncloned SIVmac251 had a higher incidence of SIVE (27.5%; 14/51) than animals infected with molecularly cloned SIVmac239 and its T-cell tropic derivatives (18.5%; 10/54) this difference was not statistically significant. In this study rapid disease progression and SIVE were highly correlated making separation of viral determinants of virulence from those of neurovirulence difficult. 相似文献
139.
140.