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141.
H Morita N Petersen LO Christensen T Sinkjaer J Nielsen 《Canadian Metallurgical Quarterly》1998,80(2):610-620
The sensitivity of soleus H-reflexes, T-reflexes, and short-latency stretch reflexes (M1) to presynaptic inhibition evoked by a weak tap applied to the biceps femoris tendon or stimulation of the common peroneal nerve (CPN) was compared in 17 healthy human subjects. The H-reflex was strongly depressed for a period lasting up to 300-400 ms (depression to 48 +/- 23%, mean +/- SD, of control at a conditioning test interval of 70 ms) by the biceps femoris tendon tap. In contrast, the short-latency soleus stretch reflex elicited by a quick passive dorsiflexion of the ankle joint was not depressed. The soleus T-reflex elicited by an Achilles tendon tap was only weakly depressed (92 +/- 8%). The H-reflex was also significantly more depressed than the T-reflex at long intervals (>15 ms) after stimulation of CPN (H-reflex 63 +/- 14%, T-reflex 91 +/- 13%; P < 0. 01). However, the short-latency (2 ms) disynaptic reciprocal Ia inhibition evoked by stimulation of CPN was equally strong for H- and T-reflexes (H-reflex 72 +/- 10%, T-reflex 67 +/- 13%; P = 0.07). Peaks in the poststimulus time histogram (PSTH) of the discharge probability of single soleus motor units (n = 53) elicited by an Achilles tendon tap had a longer duration than peaks evoked by electrical stimulation of the tibial nerve (on average 5.0 ms as compared with 2.7 ms). All parts of the electrically evoked peaks were depressed by the conditioning biceps femoris tendon tap (average depression to 55 +/- 27% of control; P < 0.001). A similar depression was observed for the initial 2 ms of the peaks evoked by the Achilles tendon tap (69 +/- 48%; P < 0.001), but the last 2 ms were not depressed. Conditioning stimulation of the CPN at long intervals (>15 ms) also depressed all parts of the electrically evoked PSTH peaks (n = 34; average 65%; P < 0.001) but had only a significant effect on the initial 2 ms of the peaks evoked by the Achilles tendon tap (85%; P < 0.001). We suggest that the different sensitivity of mechanically and electrically evoked reflexes to presynaptic inhibition is caused by a difference in the shape and composition of the excitatory postsynaptic potentials underlying the two reflexes. This difference may be explained by a different composition and/or temporal dispersion of the afferent volleys evoked by electrical and mechanical stimuli. We conclude that it is not straightforward to predict the modulation of stretch reflexes based on observations of H-reflex modulation. 相似文献
142.
B Petersen CJ Yee W Bowen R Zarnegar GK Michalopoulos 《Canadian Metallurgical Quarterly》1994,10(4):219-230
TGF-beta 1 is known as a potent inhibitor of proliferation of rat and human hepatocytes. In this study we show that the effects of TGF-beta 1 are quite different on mouse hepatocytes. In rat and human hepatocytes, TGF-beta 1 inhibited DNA synthesis and also inhibited the morphological changes induced by growth factors in rat and human hepatocytes. In contrast, addition of TGF-beta 1 to mouse hepatocytes resulted in pronounced alterations in morphology of these cells. These changes were similar to those induced by HGF and EGF. The induction of structural changes by TGF-beta 1 was noted only in mouse hepatocytes. Mouse hepatocytes were also much more resistant to the mito-inhibitory effect of TGF-beta 1. These findings suggest profound differences in hepatocyte growth regulation between these species and may relate to observed differences in susceptibility to carcinogenesis. 相似文献
143.
HJ de Haard B Kazemier A van der Bent P Oudshoorn P Boender B van Gemen JW Arends HR Hoogenboom 《Canadian Metallurgical Quarterly》1998,11(12):1267-1276
While studying the expression of single-chain antibodies (scFv) derived from several murine monoclonal antibodies, we found that residue 6 in Framework region 1 of the heavy chain variable domain plays a crucial role in antibody folding. Binding activity of three murine antibodies with a heavy chain variable region (VH) subgroup IIA was completely lost when at this position the wild-type residue glutamine (Q) was substituted by glutamate (E). Increased sensitivity towards trypsin digestion of soluble scFv suggested that the lack of binding activity was caused by incorrect folding of Q6E mutants. Grafting of the three additional class IA derived FR1 residues, based upon the comparison between both classes of VH sequences, on to the 'defect' subgroup IIA sequence, partially restored the antigen binding activity of the Q6E-containing scFv. Our results suggest that residue 6 of the heavy chain may be part of a folding nucleus, involving the first two beta-strands of Framework region 1. The evolutionary conservation of either glutamine or glutamate at position 6 in different antibody families may well indicate that within immunoglobulin VH domains, different family specific folding nuclei have evolved. 相似文献
144.
Provision of reliable, valid, and informative data to the public for evaluating the performance of health care services has been inconsistent at best and erroneous at worst. This article examines how private and governmental agencies are addressing this issue by concentrating on a well-defined set of performance indicators for several key diseases. In order to fully consider the implications of these developments for rehabilitation, the author discusses 4 topics: (a) how quality and safety concerns influence health care policy, (b) watershed events over the past half century that have contributed to a quality and safety dilemma in health care, (c) the difference between process and outcome indicators and implications for robust performance measurement, and (d) emerging coordination efforts by accreditation and regulatory agencies that will shape clinical service delivery in rehabilitation. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
145.
OV Gerasimenko JV Gerasimenko PV Belan OH Petersen 《Canadian Metallurgical Quarterly》1996,84(3):473-480
In pancreatic acinar cells low (physiological) agonist concentrations evoke cytosolic Ca2+ spikes specifically in the apical secretory pole that contains a high density of secretory (zymogen) granules (ZGs). Inositol 1,4,5-trisphosphate (IP3) is believed to release Ca2+ from the endoplasmic reticulum, but we have now tested whether the Ca(2+)-releasing messengers IP3 and cyclic ADP-ribose (cADPr) can liberate Ca2+ from AGs. In experiments on single isolated ZGs, we show using confocal microscopy that IP3 and cADPr evoke a marked decrease in the free intragranular Ca2+ concentration. Using a novel high resolution method, we have measured changes in the Ca2+ concentration in the vicinity of an isolated AG and show that IP3 and cADPr cause rapid Ca2+ release from the granule, explaining the agonist-evoked cytosolic Ca2+ rise in the secretory pole. 相似文献
146.
S. M. Myers G. A. Petersen D. M. Follstaedt T. J. Headley J. R. Michael C. H. Seager 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》1996,120(1-4):43-50
We have mechanistically and quantitatively characterized the binding of transition-metal impurities in Si to cavities formed by He implantation and to B---Si precipitates resulting from B implantation. Both sinks are inferred to act by the segregation of metal atoms to pre-existing low-energy sites, namely surface chemisorption sites in the case of cavities and bulk solution sites in the case of the B---Si phase. These gettering processes exhibit large binding energies, and they are predicted to remain active for arbitrarily small initial impurity concentrations as a result of the segregation mechanisms. Both appear promising for gettering in Si devices. 相似文献
147.
The temperature history for the BPI-W2 well in the oil-producing Suphan Buri Basin, central Thailand, has been investigated using different surface temperatures (Ts ). Two ID models using Ts values of 0°C and ∼22°C were able to fit the suppression-corrected vitrinite reflectance (VR) values and burial peak temperatures (Tpeak ) in the well. The geothermal gradient averaged over 3 km is ∼54°C/km for Ts = 0°C, whereas it is ∼42°C/km for Ts ∼22°C. Ts = 0°C is, however, considered to be unrealistic and the ∼54°C/km gradient is therefore too high. Similarly, a previously determined geothermal gradient of 62°C/km is considered to be an overestimate. The geothermal gradient of ∼42°C/km is plausible compared to other geothermal gradients onshore and offshore Thailand, although it is at the low end. This may be due to a too low suppression correction for the measured VR values. The obtained temperature history can be used to predict measured present-day temperatures of Ts ∼22°C and 77°C in the reservoir in the U Thong oilfield. The obtained temperature history associated with the geothermal gradient of ∼42°C/km seems realistic as it predicts that the onset of oil generation at 107°C will have post-dated reservoir and trap formation in Middle to Late Miocene times. 相似文献
148.
This paper considers the problem of robustly stabilizing an uncertain system via fixed-order output feedback control. This problem is considered by defining a notion of robust stabilizability with a quadratic storage function. This notion is closely related to the notion of quadratic stabilizability. The main result of the paper shows that if an uncertain system is robustly stabilizable with a quadratic storage function via a nonlinear time-varying controller, then it will also be robustly stabilizable with a quadratic storage function via a linear time-invariant controller of the same order 相似文献
149.
A 64-year-old male patient had two episodes of transient ischemic attack and a cerebral infarction. Cerebral angiography showed 50% stenosis at the junction of left internal carotid artery and 90% stenosis at left mid-cerebral artery (MCA). Coronary angiography showed two vessel disease with arteriosclerotic change and underwent coronary artery bypass grafting. To prevent intraoperative cerebral infarction, we used brain protect solution just before starting ECC, set perfusion flow around 3 l/min/m2, monitored the flow of left MCA using Transcranial Doppler (TCD) and the saturation of left internal jugular vein (SjO2) continuously. PaCO2 was controlled around 45 mmHg. TCD showed good pulsatile flow, and SjO2 was kept over 60%. The patient recovered consciousness 2 hours after operation in the intensive care unit without paresthesia. We thought the number of open-heart cases with cerebrovascular disease increased, and pulsatile low of ECC by intraaortic balloon pumping and the monitoring of SjO2 are useful for the cases. 相似文献
150.
Bent F. Sørensen Kenneth Jørgensen Torben K. Jacobsen Rasmus C. Østergaard 《International Journal of Fracture》2006,141(1-2):163-176
A double cantilever beam specimen loaded with uneven bending moments (DCB-UBM) is proposed for mixed mode fracture mechanics
characterisation of adhesive joints, laminates and multilayers. A linear elastic fracture mechanics analysis gives the energy
release rate and mode mixity analytically for both isotropic and orthotropic materials. By varying the ratio between the two
applied moments, the crack tip stress state can be varied from pure mode I to pure mode II for the same specimen geometry.
The specimen allows stable crack growth. A special test fixture is developed to create uneven bending moments. As a preliminary
example, the DCB-UBM specimen was used for characterising fracture of adhesive joints between two laminates of thermoset glass
fibre reinforced plastic. 相似文献