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81.
82.
A Roossien JR Brunsting A Nijmeijer J Zaagsma WG Zijlstra 《Canadian Metallurgical Quarterly》1997,33(2):392-399
OBJECTIVE: The vagal cardiac accelerator (VCA) system takes part in the nervous control of the heart rate. In the present study we tried to adduce evidence that vasoactive intestinal polypeptide (VIP) contributes to vagally induced cardioaccelerations. METHODS: The effect of VIP on heart rate and arterial blood pressure was investigated after unmasking the inherent VCA activity by blocking the sympathetic accelerator and vagal decelerator influences on heart rate in conscious dogs. RESULTS: Following intravenous administration of VIP (10 micrograms i.v.) the heart rate increased by 43.6 +/- 6.7 (28.1 +/- 4.7%), from 165.6 +/- 8.5 to 209.1 +/- 7.0 beats/min (P < 0.001) and the mean arterial blood pressure decreased by 47.5 +/- 3.2 (37.9 +/- 3.0%), from 126.6 +/- 2.6 to 79.1 +/- 4.9 mmHg (P < 0.001) (n = 11). After VCA activity was reflexly enhanced by alpha 1-adrenoceptor stimulation with methoxamine, VIP increased heart rate by 36.9 +/- 7.3 (21.5 +/- 4.6%), from 179.8 +/- 5.2 to 216.7 +/- 5.8 beats/min (P < 0.001) and decreased mean arterial pressure by 79.1 +/- 6.4 (46.7 +/- 3.5%), from 168.2 +/- 4.1 to 89.1 +/- 5.0 mmHg (P < 0.001). Hence, the VIP-induced tachycardia, expressed in relative values, shows a significant attenuation after the administration of methoxamine (P < 0.05). The increase in heart rate induced by VIP appeared to be inversely related to the prevailing VCA activity, both before (r = -0.744, P = 0.009) and after methoxamine (r = -0.689, P = 0.019). The VIP-induced tachycardia is certainly not reflexly induced by the fall in arterial pressure, because intracoronary administration of VIP (0.5 microgram i.c.) caused an appreciable increase in the heart rate by 63.7 +/- 13.0 (46.4 +/- 10.4%), from 143.0 +/- 8.1 to 208.7 +/- 12.0 beats/min (P < 0.005), whereas the mean arterial pressure only slightly changed (-7.7 +/- 2.0 mmHg) (P < 0.05) (n = 6). In addition, VIP (10 micrograms i.v.) also caused a tachycardia in vagotomized dogs with blocked beta-adrenergic and muscarinic receptors. The administration of the VIP antagonists [D-p-CI-Phe6, Leu17]-VIP (50-150 micrograms i.c.) and [Lys1, Pro2,5, Leu17]-VIP (20 micrograms i.c.) did not result in alterations in VCA activity nor did the VIP antagonists block the VCA reflex response to a rise in arterial pressure. However, none of the VIP antagonists reduced the VIP-induced tachycardia either. CONCLUSION: Vasoactive intestinal polypeptide is likely to play a part in the vagal cardiac accelerator system. However, conclusive evidence for its role as the terminal transmitter in the VCA pathway will have to wait for the availability of a specific cardiac VIP receptor antagonist. 相似文献
83.
YT Chen MJ Henk KJ Carney WD Wong DA Rothenberger T Zheng M Feygin RD Madoff 《Canadian Metallurgical Quarterly》1997,1(3):266-72; discussion 273
Risk of colorectal cancer recurrence has traditionally been determined by use of pathologic staging. However, it is apparent that subgroups of patients exist within tumor stages whose clinical behavior differs. This study was undertaken to identify tumor-associated factors that might be predictive of outcome in patients with intermediate stages who will benefit the most from postsurgical adjuvant therapy. Seventy patients with stage II and III colorectal cancer were assessed for DNA index, S-phase fraction, p53 expression, and Ki-67 index. Tumor recurrence was analyzed by means of nonparametric tests and Cox proportional hazard models incorporating standard clinical and pathologic criteria. Of the four prognostic markers evaluated, Ki-67 index was significantly associated with disease recurrence (P = 0.02), whereas DNA index, S-phase fraction, and p53 expression were not. After stratification by tumor stage, significant associations between Ki-67 index and disease recurrence were retained in stage II tumors (P = 0.01) but not in stage III tumors (P = 0.23). Cox proportional hazard regression analysis indicated that among stage II patients, those with a Ki-67 index >45% were associated with 6.5 times greater risk for disease recurrence than those with a Ki-67 index >/=45%. It was concluded that an elevated Ki- 67 index is associated with an increased risk of tumor recurrence in stage II colorectal cancer. 相似文献
84.
Natlia Moreno Xavier Querol Angel Lpez‐Soler Jos Manuel Andres Maria Janssen Henk Nugteren Mark Towler Kenneth Stanton 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2004,79(9):1009-1018
Zeolitic material is obtained from fly ash both by direct conversion of the ash or from SiO2 extracts obtained from fly ash. This study focuses on determining the suitability of a fly ash for SiO2 extraction and for zeolite synthesis by direct conversion. The SiO2 extraction experiments from different fly ashes show that the main parameters governing the SiO2 extraction are: (a) a high bulk SiO2 content (>52%, for obtaining an extraction yield of 100 g SiO2 kg?1) in the starting fly ash, (b) a high proportion (>55%) of the bulk SiO2 present in the degradable glass matrix and the highly soluble opaline fraction, and (c) a high bulk SiO2/Al2O3 ratio (>2.0) of the fly ash. The results from experiments of zeolite synthesis by direct conversion demonstrate that the most important criteria for the selection of a fly ash for this process are: (a) a high content of Al2O3 and SiO2(>65%) (b) a high glass content (>63%) and (c) relatively low SiO2/Al2O3 ratio (<2.0). Multivariate analysis confirms the importance of the above‐mentioned variables and shows some additional variables that have influence on ash behaviour under alkaline conditions. It quantifies the use of those variables for determining the suitability of ashes for SiO2 extraction and zeolite synthesis and is able to distinguish between the two. Copyright © 2004 Society of Chemical Industry 相似文献
85.
Van Leeuwen Thed N. Visser Martijn S. Moed Henk F. Nederhof Ton J. Van Raan Anthony F. J. 《Scientometrics》2003,57(2):257-280
Evaluation studies of scientific performance conducted during the past years more and more focus on the identification of
research of the 'highest quality', 'top' research, or 'scientific excellence'. This shift in focus has lead to the development
of new bibliometric methodologies and indicators. Technically, it meant a shift from bibliometric impact scores based on average values such as the average impact of all papers published by some unit to be evaluated towards indicators reflecting the topof the citation distribution, such as the number of 'highly cited' or 'top' articles. In this study we present a comparative
analysis of a number of standard and new indicators of research performance or 'scientific excellence', using techniques applied
in studies conducted by CWTS in recent years. It will be shown that each type of indicator reflects a particular dimension
of the general concept of research performance. Consequently, the application of one single indicator only may provide an
incomplete picture of a unit's performance. It is argued that one needs to combine the various types of indicators in order
to offer policy makers and evaluators valid and useful assessment tools.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
86.
Richard Le Heron Glen W. Atkinson Henry Teune Greg Mason Henk Voogd Brenda J. Moscove Patricia Gober Thomas A. Reiner Richard F. Curtis Stephen F. Seninger W. W. Hall Jr. John E. Keith M. Van Naelten R. W. Keyes John Huttman Robert B. Weeden Clarence G. Ray Steven E. Daniels F. Larry Leistritz Patrizia Spinetti Peter D. Beaulieu F. J. Potgieter David L. Barkley Charles A. Berry Jean E. Weber Wieslaw Rozlucki Jesse Burkhead John R. Ottensmann Noel D. Uri Erlet Cater J. Barry Riddell Ernesto Quintanilla John F. McDonald Jon R. Miller Stan Czamanski 《The Annals of Regional Science》1986,20(1):87-144
87.
By using the recently developed (differential) geometric approach to nonlinear systems, a feedback decomposition for nonlinear control systems is derived. 相似文献
88.
Samuelson Charles D.; Messick David M.; Rutte Christel; Wilke Henk 《Canadian Metallurgical Quarterly》1984,47(1):94
Administered a resource management task to 86 US and 97 Dutch undergraduates. Ss were divided into groups of 6 and instructed to harvest points from a regenerating resource pool. Their objective was to maximize individual harvests while maintaining the resource pool. The factorial design crossed 3 levels of resource use (overuse, underuse, and optimal use) with 2 levels of variance of others' purported harvests (low and high). Both variables were manipulated through false feedback to Ss regarding the pool size and the other Ss' harvests. The primary dependent measures were Ss' individual harvests and whether Ss voted for or against elimination of free access to the resource in favor of electing a leader who would make harvest decisions for the group. Results indicate that harvest size increased over time only in the under- and optimal-use conditions. As predicted, overuse Ss voted to give up free access to the resource and to elect a leader more frequently than Ss in the other conditions. Differences between American and Dutch Ss were found only for the variance manipulation. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
89.
Algorithms for calculating the emitter hole and electron currents in the case of an n+n? epitaxial emitter have been published by Yu [2] and Rofail et al. [3]. Both algorithms are restricted to a small ratio of hole to electron current whereas Yu's algorithm is further restricted by the assumption of a constant electric field in the epilayer.In the present paper an algorithm is presented in which both restrictions have been removed and which is valid from low through high injection. The assumption of quasineutrality in the epilayer, which is used in the present algorithm, is veryfied using Adlers criterium [4]. Calculation results are presented for a structure treated by Poorter [1] and a comparison is made with his results. 相似文献
90.
Henk F. J. Hendriks Pieter J. A. M. Brekelmans Rien Buytenhek Adriaan Brouwer A. Margreet de Leeuw Dick L. Knook 《Lipids》1987,22(4):266-273
The neutral lipid and phospholipid compositions of purified sinusoidal (fat-storing, endothelial and Kupffer) cells, parenchymal
cells and liver homogenates were determined by thin layer chromatography. In addition, the retinoid content of the same purified
cell populations was determined by high performance liquid chromatography. From each cell type, both a lipid droplet fraction
and a pellet fraction (containing the majority of the remaining cell organelles) were prepared by differential centrifugation.
Electron microscopic analysis showed that lipid droplets isolated from fat-storing cells were larger (up to 8 μm) than those
isolated from parenchymal cells (up to 2.5 μm). Moreover, the parenchymal lipid droplets seemed to be surrounded by a membranous
structure, while the fat-storing lipid droplets seemed not to be. Both fat-storing and parenchymal cells contained high concentrations
of neutral lipids, 57.9 μg and 71.0 μg/106 cells, respectively, while endothelial and Kupffer cells contained only 8.6 μg and 13.8 μg/106 cells of neutral lipids, respectively. Sixty-five percent of fat-storing cell lipid droplet fractions comprised esters of
retinol and cholesterol. This combined ester fraction contained mainly retinyl esters. In addition, considerable quantities
(20%) of triglycerides were present. Parenchymal cell lipid droplet fractions comprised triglycerides (62%) and cholesteryl
esters (up to 30%). The pellet fractions prepared from all four cell types consisted mainly of cholesterol (41–67%) and free
fatt acids (20–28%). The phospholipid content was much higher in parenchymal cells than in the sinusoidal liver cell types.
The relative proportions of the four major phospholipid classes were comparable in all liver cell types analyzed. It is concluded
that parenchymal cell lipid droplets comprised mainly triglycerides and cholesteryl esters, which is in agreement with the
function of parenchymal cells in lipid metabolism. Fat-storing cell lipid droplets consisted of retinyl esters and triglycerides,
which correlates well with their function in retionid storage and metabolism. 相似文献