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41.
Previous studies have shown that hypoglycemia may reduce counterregulatory responses to subsequent hypoglycemia in healthy subjects and in patients with diabetes. The effect of hypoglycemia on the hormonal response to a nonhypoglycemic stimulus is uncertain. To test the hypothesis that the cortisol response to corticotropin (ACTH) infusion is independent of antecedent hypoglycemia, 10 healthy subjects received a standard ACTH infusion (0.25 mg Cosyntropin [Organon, West Orange, NJ] intravenously over 240 minutes) at 8:00 AM on day 1 and day 3 and a hypoglycemic insulin clamp study (1 mU/kg/min) at 8:00 AM on day 2. During the hypoglycemic clamp, plasma glucose decreased from 5.0 mmol/L to 2.8 mmol/L for two periods of 120 minutes (mean glucose, 2.9 +/- 0.03 and 2.8 +/- 0.02 mmol/L, respectively) separated by a 60-minute interval of euglycemia (mean glucose, 4.7 +/- 0.01 mmol/L). Seven subjects also had paired control studies in random order during which a 330-minute euglycemic clamp (mean glucose, 5.0 +/- 0.11 mmol/L) instead of a hypoglycemic clamp was performed on day 2. Basal ACTH (4.6 +/- 0.7 v 2.6 +/- 0.4 pmol/L, P < .02) and basal cortisol (435 +/- 46 v 317 +/- 40 nmol/L, P < .02) both decreased from day 1 to day 3 following intervening hypoglycemia. In contrast, with intervening euglycemia, neither basal ACTH (5.9 +/- 1.5 v 4.5 +/- 1.0 pmol/L) nor basal cortisol (340 +/- 38 v 318 +/- 60 nmol/L) were reduced significantly on day 3 compared with day 1. Following interval hypoglycemia, the area under the curve (AUC) for the cortisol response to successive ACTH infusions was increased (4,734 +/- 428 nmol/L over 240 minutes [day 3] v 3,526 +/- 434 nmol/L over 240 minutes [day 1], P < .01). The maximum incremental cortisol response was also significantly increased (805 +/- 63 nmol/L (day 3) v 583 +/- 58 nmol/L (day 1), P < .05). In contrast, the AUC for the cortisol response to successive ACTH infusions with interval euglycemia (3,402 +/- 345 nmol/L over 240 minutes [day 3] v 3,709 +/- 391 nmol/L over 240 minutes [day 1] and the incremental cortisol response (702 +/- 62 nmol/L [day 3] v 592 +/- 85 nmol/L [day 1] were unchanged. Following exposure to intermittent hypoglycemia in healthy humans, fasting morning ACTH and cortisol levels are reduced and the incremental cortisol response to an infusion of ACTH is enhanced. The enhanced cortisol response to exogenous ACTH infusion after intervening hypoglycemia (but not intervening euglycemia) may reflect priming of the adrenal gland by endogenous ACTH produced during the hypoglycemia. These data suggest that adrenal function testing by exogenous ACTH administration is not impaired by prior exposure to hypoglycemia. Moreover, the reduced cortisol response to recurrent hypoglycemia in patients with well-controlled diabetes is not likely the result of impaired adrenal responsiveness. 相似文献
42.
SD Shiian SV Kha?dukov AL Pukhal''ski? AP Toptygina NV Bovin 《Canadian Metallurgical Quarterly》1996,41(2):24-29
The interaction of human peripheral blood leukocytes with alpha 1-acid glycoprotein (AGP), its glycoforms as well as neoglyco-conjugates representing carbohydrate chains of AGP or its fragments was studied by flow cytometry. It was shown that the main target cells for AGP as well as for conjugates of its carbohydrate chains with polyacrylamide (PAA) are monocytes and polymorphonuclear leukocytes but not lymphocytes. The interaction of AGP with monocytes and granulocytes are mediated by its carbohydrate chains: the binding of AGP with cells was inhibited by AGP, AGP oligosaccharides as well as conjugates of oligosaccharides and its fragments with PAA. The data obtained show the existence of monocyte (and granulocyte) receptors which interact with complex type sialooligosaccharides of AGP. 相似文献
43.
KW Mahaffey CB Granger R Collins CM O'Connor EM Ohman SD Bleich JJ Col RM Califf 《Canadian Metallurgical Quarterly》1996,77(8):551-556
Intravenous heparin is routinely given after thrombolytic therapy for patients with acute myocardial infarction in the United States and in some, but by no means all, other countries. Several trials have documented improved infarct-artery patency in patients treated with heparin; however, none was large enough individually to assess the effect of heparin on clinical outcomes. We performed a systematic overview of the 6 randomized controlled trials (1,735 patients) to summarize the available data concerning the risks and benefits of intravenous heparin versus no heparin after thrombolytic therapy. Mortality before hospital discharge was 5.1% for patients allocated to intravenous heparin compared with 5.6% for controls (relative risk reduction of 9%, odds ratio 0.91, 95% confidence interval 0.59 to 1.39). Similar rates of recurrent ischemia and reinfarction were observed among those allocated to heparin therapy or control. The rates of total stroke, intracranial hemorrhage, and severe bleeding were similar in patients allocated to heparin; however, the risk of any severity of bleeding was significantly higher (22.7% vs 16.2%; odds ratio 1.55, 95% confidence interval 1.21 to 1.98). There was no significant difference in the observed effects of heparin between patients receiving tissue-type plasminogen activator and those receiving streptokinase or anisoylated plasminogen streptokinase activator complex, or between patients who did and did not receive aspirin. The findings of this overview demonstrate that insufficient clinical outcome data are available to support or to refute the routine use of intravenous heparin therapy after thrombolysis. It is not known if these findings are due to lack of statistical power, inappropriate levels of anticoagulation, or lack of benefit of intravenous heparin. Large randomized studies of heparin (and of new antithrombotic regimens) are needed to establish the role of such therapy. 相似文献
44.
Pre-transplant nephrectomy was done in a 25-year-old man for calculous pyelonephritis using a retroperitoneal laparoscopic approach with a newly devised ligature applicator-dissector- kidney retractor. 相似文献
45.
Barbara M. Johnston Peter R. Johnston 《International journal for numerical methods in engineering》2003,56(4):589-607
Accurate numerical evaluation of integrals arising in the boundary element method is fundamental to achieving useful results via this solution technique. In this paper, a number of techniques are considered to evaluate the weakly singular integrals which arise in the solution of Laplace's equation in three dimensions and Poisson's equation in two dimensions. Both are two‐dimensional weakly singular integrals and are evaluated using (in a product fashion) methods which have recently been used for evaluating one‐dimensional weakly singular integrals arising in the boundary element method. The methods used are based on various polynomial transformations of conventional Gaussian quadrature points where the transformation polynomial has zero Jacobian at the singular point. Methods which split the region of integration into sub‐regions are considered as well as non‐splitting methods. In particular, the newly introduced and highly accurate generalized composite subtraction of singularity and non‐linear transformation approach (GSSNT) is applied to various two‐dimensional weakly singular integrals. A study of the different methods reveals complex relationships between transformation orders, position of the singular point, integration kernel and basis function. It is concluded that the GSSNT method gives the best overall results for the two‐dimensional weakly singular integrals studied. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
46.
Leung MK Such GK Johnston AP Biswas DP Zhu Z Yan Y Lutz JF Caruso F 《Small (Weinheim an der Bergstrasse, Germany)》2011,7(8):1075-1085
Nano-/micrometer-scaled films and capsules made of low-fouling materials such as poly(ethylene glycol) (PEG) are of interest for drug delivery and tissue engineering applications. Herein, the assembly and degradation of low-fouling, alkyne-functionalized PEG (PEG(Alk) ) multilayer films and capsules, which are prepared by combining layer-by-layer (LbL) assembly and click chemistry, are reported. A nonlinear, temperature-responsive PEG(Alk) is synthesized, and is then used to form hydrogen-bonded multilayers with poly(methacrylic acid) (PMA) at pH 5. The thermoresponsive behavior of PEG(Alk) is exploited to tailor film buildup by adjusting the assembly conditions. Using alkyne-azide click chemistry, PEG(Alk)/PMA multilayers are crosslinked with a bisazide linker that contains a disulfide bond, rendering these films and capsules redox-responsive. At pH 7, by disrupting the hydrogen bonding between the polymers, PEG(Alk) LbL films and PEG(Alk) -based capsules are obtained. These films exhibit specific deconstruction properties under simulated intracellular reducing conditions, but remain stable at physiological pH, suggesting potential applications in controlled drug release. The low-fouling properties of the PEG films are confirmed by incubation with human serum and a blood clot. Additionally, these capsules showed negligible toxicity to human cells. 相似文献
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Reactive Laser Ablation Synthesis of Nanosize Alumina Powder 总被引：1，自引：0，他引：1
Gregory P. Johnston Ross Muenchausen Douglas M. Smith William Fahrenholtz Steve Foltyn 《Journal of the American Ceramic Society》1992,75(12):3293-3298
An aluminum (Al) target was laser ablated in an oxygen (O2 ) atmosphere, producing nanosize alumina (Al2 O3 ) powder. The powder surface area decreased (and the particle size increased) with both increasing oxygen pressure and laser fluence. All powders produced had surface areas between 135 and 250 m2 /g, corresponding to primary particle sizes ranging from 7 to 3 nm in radius. Phase evolution with temperature was studied via X-ray diffraction. These powders showed a direct transformation from γ- to α-alumina at approximately 1200°C, bypassing other transition alumina phases, while still maintaining small particle size ( 30 nm). Despite the nanosize particles, green densities equal to 54% of the skeletal density (i.e., true density of the solid phase) were obtained by uniaxial pressing at 40 MPa. 相似文献