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排序方式: 共有479条查询结果,搜索用时 15 毫秒
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83.
A sensitive spectrophotometric micromethod was developed for estimation of ornithine decarboxylase (ODC) activity in animal tissues. Distinct increase in the enzymatic activity was found in regenerating and malignant liver tissues as well as in hepatomas G-27 and G-46 as compared with the corresponding tissues of control animals. The linear relationship between the optic density and content of dinitrophenyl putrescine was maintained over the range of 0 to 150 nmol per a sample. The ODC pH optimum was observed within the zone pH 6.4-6.8; it did not depend on the nature of the buffer, used for tissue homogenization. The recovery of putrescine added into the sample was equal to 102.97 +/- 2.22%. The method had an error less than 3%, its sensitivity was 0.1 nmol/sample and the reproducibility was about 100%. 相似文献
84.
Large dilators passed through the sphincter of Oddi do not prevent retained or recurrent common bile duct stones. Large dilators are more likely to cause postoperative pancreatitis than are small ones. Pancreatitis resulting from maximal dilation is more likely to be severe, and the patients are more likely to die from it. 相似文献
85.
AV Prokhorov DI Padgett DW Wetter TT Le HE Kitsman 《Canadian Metallurgical Quarterly》1998,115(6):59-63
To address ST use effectively, awareness needs to be raised regarding its harmful affects and addictive nature. Clinicians can and should take a leadership role in the control of ST by addressing ST use with patients. The recommendations provide clinicians with practical tools and strategies for intervention with ST users and potential users. Although many of these strategies require training and time, it should be emphasized that even minimal intervention can be effective in combating ST use. 相似文献
86.
Fusion proteins consisting of an Ig containing xenogenic constant regions and granulocyte-macrophage colony stimulating factor (Id-GM-CSF) are potent immunogens capable of inducing anti-idiotypic Abs after two immunizations, without the usual need for adjuvants or carrier proteins. In this study, we investigated the effects of hyperimmunization with Id-GM-CSF and found that it induces anti-GM-CSF Abs that could bind to GM-CSF and neutralize its bioactivity in vitro. However, no detrimental effects of the anti-GM-CSF activity were apparent on the general health of the animals or on their base line white blood cell counts. Mice with the anti-GM-CSF activity reconstituted their peripheral white blood cells with identical kinetics as control mice after high dose cyclophosphamide treatment, sublethal irradiation, or lethal irradiation followed by syngeneic bone marrow transplantation. Primary and secondary Ab responses to a variety of protein Ags, including an unrelated Ig Id, were not affected. However, the anti-Id response induced by an unrelated GM-CSF fusion protein that is dependent upon the GM-CSF bioactivity was impaired. To avoid any potential problems associated with inducing anti-GM-CSF Abs, we show that priming with the Id-GM-CSF protein and boosting with the Id protein alone were sufficient to induce comparable anti-Id titers without inducing anti-GM-CSF Abs. We conclude that although hyperimmunization of mice with the GM-CSF fusion protein induced neutralizing anti-GM-CSF Abs, this was of little consequence to the animals. Nevertheless, we have devised a strategy to overcome this potential limitation on the use of GM-CSF fusion proteins for immunization. 相似文献
87.
Human MDR 1 protein overexpression delays the apoptotic cascade in Chinese hamster ovary fibroblasts
LJ Robinson WK Roberts TT Ling D Lamming SS Sternberg PD Roepe 《Canadian Metallurgical Quarterly》1997,36(37):11169-11178
Several laboratories have reported that overexpression of the multidrug resistance (MDR) protein is associated with intracellular alkalinization, and several investigators have reported that cells induced to undergo programmed cell death (apoptosis) acidify quite significantly. Because it is difficult to fully explain the resistance to apoptosis-inducing chemotherapeutic drugs that is exhibited by MDR tumor cells solely via altered drug transport alone [Hoffman et al. (1996) J. Gen. Physiol. 108, 295-313], we have investigated whether overexpression of the hu MDR 1 protein alters progression of the apoptotic cascade. LR73 fibroblasts induced to undergo apoptosis either via treatment with the chemotherapeutic drug colchicine or by serum withdrawal exhibit cellular volume changes, intracellular acidification, nuclear condensation, and chromosomal digestion ("ladder formation"), characteristic of apoptosis, in a temporally well-defined pattern. However, multidrug resistant LR73/20E or LR73/27 hu MDR 1 transfectants recently created in our laboratory without selection on chemotherapeutic drug are significantly delayed in the onset of apoptosis as defined by the above criteria, regardless of whether apoptosis is induced by colchicine treatment or by serum withdrawal. Thus, the delay cannot simply be due to the well-known ability of MDR protein overexpression to lower chemotherapeutic drug accumulation in MDR cells. LR73/27V500 "selectants", exhibiting similar levels of MDR protein overexpression but higher multidrug resistance due to selection with the chemotherapeutic drug vincristine, exhibit a slightly longer delay in the progression of apoptosis. Normal apoptotic cascade kinetics are partially restored by pre-treatment of the MDR cells with the MDR protein inhibitor verapamil. Untransfected LR73 cells not expressing MDR protein but elevated in pHi via manipulation of CO2/HCO3- as described [Hoffman et al. (1996) J. Gen. Physiol. 108, 295-313] are inhibited in DNA ladder formation, similar to LR73/hu MDR 1 transfectants. These results uncover an additional mechanism whereby MDR protein overexpression may promote the survival of tumor cells and further support the notion that in some systems intracellular acidification may be either causal or permissive for proper progression of the apoptotic cascade. 相似文献
88.
A Berstad T Hauksen OH Gilja K Hveem KA Undeland I Wilhelmsen TT Haug 《Canadian Metallurgical Quarterly》1997,32(3):193-197
PURPOSE: We investigated the capabilities of chest radiography in the elderly considering that the examination must meet the main clinical indications of this population and that it is necessary in the elderly because the correct clinical assessment is often difficult or impossible. MATERIALS AND METHODS: We reviewed the chest radiographs of 756 consecutive elderly patients admitted to our hospital from September 1 to October 31, 1996. If possible, chest radiographs were performed with the AMBER technique (156 patients, 20.7%); 240 patients (31.7%) underwent conventional radiography and the others frontal projections only (360 patients, 47.6%). T-MAT G RA Kodak high contrast films with Kodak Lanex green transmitting intensifying screens were used in all cases. The AMBER examinations of 48/156 patients with hemodynamic clinical indications were repeated with conventional frontal projections. Radiographic reports were made separately by different radiologists who considered especially the diagnostic accuracy of every examination in determining the venous overload of pulmonary circulation. RESULTS: Hemodynamic studies are the most frequent clinical indication of chest radiography in elderly patients (228/756 patients in our series, 30.2%); moreover, even if careful cardiac and pulmonary circulation studies are very important in these patients, only 52.4% of all radiographs could be made in two orthogonal projections. The blurred appearance of vascular landmarks indicating increased extravascular fluid is better depicted by conventional radiography (59.7% of cases) than by AMBER (40.3%). CONCLUSIONS: We conclude that the reduced pulmonary contrast obtained with the so-called "hard X-ray" technique poorly depicts the blurred appearance of pulmonary vessels in pulmonary venous overload. Moreover, "hard X-ray" techniques can be only sporadically used because elderly patients are often in very critical conditions, which prevents this type of examination. 相似文献
89.
Batyrkhan Omarov Azhar Tursynova Octavian Postolache Khaled Gamry Aidar Batyrbekov Sapargali Aldeshov Zhanar Azhibekova Marat Nurtas Akbayan Aliyeva Kadrzhan Shiyapov 《计算机、材料和连续体(英文)》2022,71(3):4701-4717
The task of segmentation of brain regions affected by ischemic stroke is help to tackle important challenges of modern stroke imaging analysis. Unfortunately, at the moment, the models for solving this problem using machine learning methods are far from ideal. In this paper, we consider a modified 3D UNet architecture to improve the quality of stroke segmentation based on 3D computed tomography images. We use the ISLES 2018 (Ischemic Stroke Lesion Segmentation Challenge 2018) open dataset to train and test the proposed model. Interpretation of the obtained results, as well as the ideas for further experiments are included in the paper. Our evaluation is performed using the Dice or f1 score coefficient and the Jaccard index. Our architecture may simply be extended to ischemia segmentation and computed tomography image identification by selecting relevant hyperparameters. The Dice/f1 score similarity coefficient of our model shown 58% and results close to ground truth which is higher than the standard 3D UNet model, demonstrating that our model can accurately segment ischemic stroke. The modified 3D UNet model proposed by us uses an efficient averaging method inside a neural network. Since this set of ISLES is limited in number, using the data augmentation method and neural network regularization methods to prevent overfitting gave the best result. In addition, one of the advantages is the use of the Intersection over Union loss function, which is based on the assessment of the coincidence of the shapes of the recognized zones. 相似文献
90.
TT Horlocker RP Kufner AT Bishop PM Maxson DR Schroeder 《Canadian Metallurgical Quarterly》1999,88(2):382-387
We have identified the human papillomavirus (HPV) DNA replication initiation protein E1 as a tight-binding substrate of cyclin E/cyclin-dependent kinase (Cdk) complexes by using expression cloning. E1, a DNA helicase, collaborates with the HPV E2 protein in ori-dependent replication. E1 formed complexes with cyclin E in insect and mammalian cells, independent of Cdks and E2. Additional cyclins, including A-, B-, and F-type (but not D-type), interacted with the E1/E2 complex, and A- and E-type cyclin kinases were capable of phosphorylating E1 and E2 in vitro. Association with cyclins and efficient phosphorylation of E1 required the presence of a cyclin interaction motif (the RXL motif). E1 lacking the RXL motif displayed defects in E2-dependent HPV ori replication in vivo. Consistent with a role for Cdk-mediated phosphorylation in E1 function, an E1 protein lacking all four candidate Cdk phosphorylation sites still associated with E2 and cyclin E but was impaired in HPV replication in vitro and in vivo. Our data reveal a link between cyclin/Cdk function and activation of HPV DNA replication through targeting of Cdk complexes to the E1 replication-initiation protein and suggest a functional role for E1 phosphorylation by Cdks. The use of cyclin-binding RXL motifs is now emerging as a major mechanism by which cyclins are targeted to key substrates. 相似文献