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排序方式: 共有435条查询结果,搜索用时 78 毫秒
1.
Jeffrey Buenaflor Parker Sommerville Hang Qian Christine Luscombe 《Macromolecular chemistry and physics.》2020,221(2)
A comparative study involving bimetallic nickel catalysts designed from disubstituted N,N,N′,N′‐tetra(diphenylphosphanylmethyl)benzene diamine bridging ligands is reported. Catalyst behavior is explored in the Kumada catalyst‐transfer polymerization (KCTP) using poly(3‐hexylthiophene) (P3HT) as the model system. The success of a controlled polymerization is monitored by analyzing monomer conversion, degree of polymerization, end‐group identity, and molecular weight distribution. The characterization of P3HT obtained from KCTP initiated with the bimetallic catalysts shows chain‐growth behavior; however, the presence of Br/Br end‐groups and broader molecular weight distribution reveals a reduced controlled polymerization compared to the commonly employed Ni(dppp)Cl2. The observed increase in intermolecular chain transfer and termination processes in KCTP initiation with the bimetallic catalysts can be attributed to a weaker Ni(0)‐π‐aryl complex interaction, which is caused by increased steric crowding of the coordination sphere. 相似文献
2.
A study of some variables in a tetrazolium dye (MTT) based assay for cell growth and chemosensitivity 总被引:24,自引:0,他引:24
We have studied various factors involved in the optimal use of a tetrazolium (MTT) based colorimetric assay for cell growth and chemosensitivity. The assay is dependent on the ability of viable cells to metabolise a water-soluble tetrazolium salt into a water-insoluble formazan product. We have found that DMSO is the best solvent for dissolving the formazan product, especially where a significant amount of residual medium is left in the wells of the microtitre tray used for the assay. A reaction occurs between medium and a solution of MTT formazan in DMSO which changes the shape of the absorbance spectrum of the solution. The resulting optical density is not however greatly dependent upon the volume of added medium in the range 1-10 microliters. Between 10 and 40 microliters of added medium results in a gradually lower optical density than that produced by the smaller volumes. Above 40 microliters, the optical density increases again due to turbidity as protein precipitation occurs. When cells are incubated with MTT, the resulting optical density of the formazan product is dependent upon both the concentration of MTT and the incubation time. The optical density is stable for several hours after solution of the formazan in DMSO. A linear relationship is seen between optical density and cell number for incubation times of 2, 4, 6 or 24 h with 20 microliters of MTT (5 mg ml-1) added to 200 microliters medium. We have adopted 4 h as the standard incubation time for the assay. Only a small amount of MTT formazan product can be detected in the growth medium of wells in which cells have been exposed to MTT. Comparative chemosensitivity data for EMT6 mouse tumour cells show good agreement between results obtained using the MTT assay and results based on total cell count after a fixed period of growth. 相似文献
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BACKGROUND: Chronic renal failure (CRF) is associated with an atherogenic
lipid profile and an increased risk of ischaemic cardiovascular disease.
The associated hyperlipidaemia is reportedly ameliorated by erythropoietin
(Epo) therapy. According to a recent report, rats studied 3 weeks after 5/6
nephrectomy and fed a high- protein diet exhibited increased activities of
hepatic HMG-CoA reductase (HMG-CoAR) and cholesterol 7 alpha-hydroxylase
(Ch-7 alpha- H), despite normal corresponding mRNA values. DESIGN AND
METHODS: This study was designed to examine the effects of naturally
progressing CRF of longer duration as well as those of Epo therapy on gene
expressions of the key factors involved in hepatic cholesterol metabolism,
i.e., LDL receptor (LDLR), HMG-CoAR, and Ch-7 alpha-H. Sprague-Dawley rats
were randomized to the CRF group (5/6 nephrectomy), Epo-treated CRF group
(given Epo 150 U/kg/twice weekly) and sham-operated, placebo- treated
normal controls. They were allowed free access to regular rat chow and
studied 6 weeks after surgery. Liver mRNAs and protein mass or activities
of the above factors were studied. RESULTS: Plasma cholesterol
concentration was significantly increased in the CRF group (P < 0.001)
and was modestly lowered (P < 0.05) by Epo therapy. However, microsomal
cholesterol concentration and LDLR, HMG-CoAR, and Ch-7 alpha-H mRNA as well
as HMG-CoAR activity, and Ch-7 alpha-H and LDLR protein mass measurements
were virtually identical in the three groups. Thus, hepatic LDLR, HMG-CoAR,
and Ch-7 alpha-H mRNA and protein measurements in rats with CRF were
similar to those of the normal control group representing an inappropriate
response to the associated hypercholesterolemia. Epo therapy led to partial
amelioration of CRF- associated hypercholesterolaemia with no discernible
effect on hepatic tissue expression of the above factors.
相似文献
5.
Aditya Kapoor John C. Luscombe A. D. Reading 《European journal of orthopaedic surgery & traumatology : orthopedie traumatologie》2007,17(4):381-383
Deep infections do occur during hip resurfacing despite all precautions. We present the method and use of the acetabular bone stock preserving Explant system in the removal of infected well-fixed cementless acetabular components and the technique of using an antibiotic impregnated cement spacer to provide a functional joint, enabling the patient to mobilise with minimal discomfort between two staged revision procedures. 相似文献
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8.
Diana Cardenas MD PhD Gustavo Díaz RD MSc Jessika Cadavid ND MSC Fernando Lipovestky MD Marisa Canicoba RD Paola Sánchez MD Ludwig Álvarez ND Yan Duarte MD José Guillermo Gutiérrez Reyes MD Gilda Miranda de Noyola RD Claudia Maza RD Sergio Santana Porbén MD Charles Elleri Bermúdez MD Yawelida García RN Isabel Calvo RD Humberto Arenas MD 《JPEN. Journal of parenteral and enteral nutrition》2022,46(1):229-237
9.
A Treatment IND (TIND) is a mechanism available to the Food and Drug Administration (FDA) in the United States by which promising new drugs can be provided to patients with life-threatening illnesses. In many instances, the illness is life-threatening but of relatively low incidence, making the demand for the new treatment limited. However, if the disease is more prevalent and incidence is increasing, the demand for access to an experimental therapy may be substantially greater. Novel approaches and technologies would help manage recruitment of physicians, enrollment of patients and retrieval and timely analysis of data. Such was the case in the TIND for tacrine hydrochloride (Cognex), a cholinesterase inhibitor which was under development for the treatment of patients with Alzheimer's Disease (AD). There were an estimated 4 million prevalent cases of AD in the US for which no approved therapeutic option was available at the time this TIND was initiated. We anticipated that there could be a large demand by both physicians and patients to enroll in the TIND. Therefore, to meet this demand, various mechanisms were employed to allow rapid enrollment and drug shipments to the patient. In addition, physicians who participated in the TIND were able to use a telephone touch-tone data entry system for reporting data and ordering new supplies of tacrine for their patients. Serious adverse events were reported directly to trained operators and summarized on a weekly basis for reporting to the FDA. At the time the programme was terminated, nearly 2000 physicians had enrolled to participate in the TIND and nearly 10,000 patients had received tacrine under the programme. The methods employed in this study to collect clinic visit and safety data met both regulatory and good clinical practice guidelines. In summary, a large volume of data was handled rapidly and efficiently in this programme. 相似文献
10.
Abstract: Haemoptysis in otherwise healthy children is an uncommon event. Two cases of massive haemoptysis, subsequently requiring lobectomy, are discussed. In each case, foreign vegetable matter was identified despite previously normal bronchoscopy and minimal changes on chest radiograph. 相似文献