Background: Molecular theories of general anesthesia often are divided into two categories: (l) Anesthetics may bind specifically to proteins, such as ionic channels, and alter their function directly, and (2) anesthetics may alter the functions of integral membrane proteins indirectly through modification of the physical properties of the membrane. Recent studies have provided evidence that anesthetics can bind to proteins and modify their function directly, bringing into question the role of the membrane in anesthetic interactions. To reexamine the role of membrane lipids in anesthetic interactions, an experimental approach was used in which the membrane lipid composition could be systematically altered and the impact on anesthetic interactions with potential targets examined.
Methods: Sodium channels from human brain cortex were incorporated into planar lipid bilayers with increasing cholesterol content. The anesthetic suppression of these channels by pentobarbital was quantitatively examined by single channel measurements under voltage-clamp conditions.
Results: Changes in cholesterol content had no effect on measured channel properties in the absence of anesthetic. In the presence of pentobarbital, however, cholesterol inhibited anesthetic suppression of channel ionic currents, with 1.9% (weight/weight, corresponding to 3.5 mol%) cholesterol decreasing anesthetic suppression of sodium channels by half. 相似文献
With pulsed X-ray cinematography we have analysed the angular excursions of the distal hindlimb joints (proximal interphalangeal, PIP; metatarsophalangeal, MTP; ankle) in cats walking on a treadmill. These distal joints transmit the body weight and the dynamic forces onto the ground. We have included the knee and hip joints in the analysis to relate the angular excursions of the proximal and distal joints and to verify the data previously obtained with external markers on the kinematics of the proximal joints. At the beginning of the stance phase the PIP joints flexed rapidly, the MTP joints extended slowly and the ankle and knee yielded under body weight. Whereas the PIP joints maintained a rather constant angular position of −75° throughout the stance phase, extension continued in the MTP joints from −230° at touch-down to −270° at the end of the stance phase. Around 50 ms before lift-off the MTP joints flexed rapidly. Early (−30 ms) after lift-off this flexion changed into a slow extension. The PIP joints extended swiftly at the stance-swing transition and moderately at the end of the swing phase. During the middle part of the swing phase they flexed slowly. Small rotatory movements around the long axis of the foot took place in the last 100 ms of the swing phase. The results of this study on the distal joints are discussed in relation to the placing of the paw, to the translation of forward propulsion into a MTP movement and to the lifting of the paw (conventionally described as toe curling). They show a differentiated mechanical interaction between the different distal limb joints during these different phases, which must be known in detail to interpret the corresponding electromyographic data and to understand how the hip is moved forward over the MTP joints which serve as the final pivot during stance. 相似文献
Summary Fifty-eight consecutive patients with lumbosacral nerve root entrapment due to spinal stenosis were treated with modified microsurgical decompression. Only the clinically relevant sides and levels were decompressed while the spinous processes, the interspinous ligaments, the medial portion of ligamentum flavum and the functionally important parts of the facet joints were preserved. The reviewers rated recovery as good or excellent in 71% of patients while patient self-assessment indicated 76% good or excellent outcome. These data suggest that microsurgical decompression of spondyloarthritic changes can effectively relieve the signs and symptoms of nerve root compression and that with careful evaluation of all available data the number of nerve roots requiring decomperession is often fewer than what is suggested by diagnositic images alone. 相似文献
In a retrospective survey of patients taking medication for hyperlipidaemia, those taking niacin (nicotinic acid) were more likely (p < 0.05) to report sicca syndromes, blurred vision, eyelid oedema, and macular oedema compared with those who never took niacin. Additionally, 7% of those taking niacin discontinued the drug owing to adverse ocular side effects, while none of the other lipid lowering agents were found to cause these side effects (p = 0.016). Data from spontaneous reporting systems support a possible association of decreased vision, cystoid macular oedema, sicca-like symptoms, discoloration of the eyelids with or without periorbital or eyelid oedema, proptosis, loss of eyebrow or eyelashes, and superficial punctate keratitis with the use of niacin in high doses. Decreased vision may be marked, and if the drug is not discontinued, may progress to cystoid macular oedema. All ocular side effects listed above are reversible if the association with niacin is recognised and the drug is discontinued; both the incidence and severity of the ocular side effects seem to be dose dependent. 相似文献
The recently developed ELISA for the thrombin-antithrombin III complex (TAT) is a sensitive, specific, and simplified means of detecting intravascular coagulation. For further evaluation of the thrombogenicity of a polyamide (P) and a Hemophan (H) hollow-fibre dialyzer a cross-over study was done in ten stable patients on maintenance hemodialysis. At the same doses of heparin (mean bolus of 30 U/kg bw and maintenance doses of 86 U/kg bw), thrombin time and partial thromboplastin time were significantly lower using H. At the end of dialysis TAT was significantly higher in H (mean +/- SEM before HD 3.57 +/- .56, at 240 min 14.9 +/- 6.5 ng/ml, p less than 0.05, Wilcoxon-test) than in P (before HD 4.36 +/- .98, at 240 min 8.95 +/- 3.0 ng/ml, p less than 0.05 H 240 vs. P 240, Wilcoxon-test). Visible clotting was more pronounced in the H filter. Among other favourable features of blood compatibility the polyamide/polyvinylpyrrolidone copolymer with a hydrophilic/hydrophobic microdomain structure has less thrombogenicity. The modified cellulosic membrane H has advantages in complement activation and leukocyte depression, but thrombogenicity seems less favourable since the incorporated diethyl-amino-ethyl groups with their positive charge bind and inactivate negatively charged heparin. 相似文献
Although malignant fibrous histiocytoma (MFH) is the most common soft tissue sarcoma of adult life, it is fairly rare in the head and neck region (3-6%). Between 1983 and 1991 8 patients with MFH in the head and neck region have been observed and treated at the ENT-department of the University of Tübingen. 5 patients have been operated (laryngopharyngeal localization), 2 patients underwent irradiation (unresectable fast growing T4-tumors of the pharynx and thyroid) and one female patient refused further therapy after two resections elsewhere. Operated patients showed no evidence of disease 2-8 years after resection (all margins have been controlled histologically). Both irradiated patients died 4 respectively 2 months after full (70 Gy) and incomplete (17 Gy) radiotherapy without visible positive effects. Both patients developed pulmonary metastasis. Since MFH can grow in thin layers along musculaoponeurotic structures the exact size is not always demonstrable by ultrasound, CT or MR scans. Metastasis occur in up to 40%, preferentially in regionary lymph nodes, in lung, liver and skeletal system. These phenomenon requires a full pretherapeutic staging. Histologically MFH is sometimes hard to distinguish from other tumors as for example various sarcomas and pleomorphic carcinoma. Therefore, immunohistochemical (mesenchymal markers) and electron microscopical investigations are advised. Resection with exact histological controll of all margins is the therapy of choice. We experienced that laryngeal MFH (n = 3) can be resected without laryngectomy under certain circumstances. Although unsuccessfull in our two cases, according to the literature, radiotherapy should be administered in unresectable cases. Depending on localization and size of MFH long survival, in single cases healing, of this disease is possible by surgical treatment. 相似文献
In 41 patients with recurrent sustained ventricular tachycardia and/or ventricular fibrillation an integrated pacemaker-defibrillator-system (PCD, Medtronic, model 7216 A or 7217 B) was implanted. In 21 out of 24 (88%) patients a new transvenous implantation technique in combination with a subcutaneous patch electrode was used. The implanted devices comprise antibradycardiac pacemaker functions, two different forms of antitachycardiac pacemaker functions (ramp and burst pacing), and internal cardioversion or defibrillation capabilities. During a mean follow-up of 8 months 147 episodes of ventricular tachycardia were detected, 131 of them were terminated successfully by antitachycardiac pacing; in 13 episodes internal cardioversion was applied to revert ventricular tachycardia. Twenty-seven episodes of ventricular fibrillation or rapid ventricular tachycardia (greater than 200/min) were detected and successfully terminated by internal defibrillation. In six patients with intermittent rapid atrial fibrillation, change of antiarrhythmic therapy was required to avoid activation of the device. The new integrated pacemaker-defibrillator systems improve therapy in patients with life-threatening tachyarrhythmias by reducing the number of internal cardioversions/defibrillations; the non-thoracotomy approach reduces the post operative risk. 相似文献
Ethanol account for a significant fraction of the energy intake of persons consuming even moderate amounts of alcohol. A recent study has shown that although alcohol does not reveal itself as a layer floating at the top of a drink, metabolically it behaves more like oil than sugar. 相似文献