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排序方式: 共有345条查询结果,搜索用时 15 毫秒
151.
JV Pincheira IH Lopez GO Tapia MH Navarrete CC Oyarzun 《Canadian Metallurgical Quarterly》1995,28(4):267-275
In the present study two cytogenetic parameters were used to evaluate the DNA damage induced by low doses (1 up to 40 rad) of X-ray irradiation in G0 human lymphocytes. These parameters were the frequency of chromosomal lesions in G2 and the length of this cell cycle phase. The frequency of chromosomal lesions in G2 was determined by scoring the number of chromosomal aberrations in G0 irradiated lymphocytes post treated with two inhibitors of G2 repair mechanisms: caffeine and 3-aminobenzamide. A dose-dependent increase in chromosomal aberrations yield was detected in G0 lymphocytes X-ray irradiated with or without post treatment with these two DNA repair inhibitors during G2. Nevertheless, the dose response in this latter condition was higher than the one detected in control cells, indicating that the increase of irradiation dose in G0 lymphocytes produces an increment in the number of DNA lesions arriving to be repaired in G2. The analysis of the dose-response relationships for G2 length showed an statistically significant X-ray dose-dependent increase (G2 delay) from 2.5 up to 40 rad and a positive correlation between G2 delay and the frequency of chromosomal lesions in G2. These results suggest that the DNA lesions induced by low doses of X-irradiation in G0 lymphocytes may be higher than that detected by the standard method (control conditions) and may be responsible for an increase in G2 length. We propose, therefore, that an analysis of these two cytogenetic parameters can improve the evaluation of the DNA damage induced by low doses of X-rays irradiation in G0 cells. 相似文献
152.
The potentiometric anion selectivity of polymer membrane-based electrodes formulated with a palladium organophosphine complex (benzylbis(triphenylphosphine)palladium(II) chloride) as the membrane active component is examined. The electrode is shown to exhibit a non-Hofmeister selectivity pattern with a significantly enhanced response toward nitrite over the concentration range of 10 microM-10 mM (log-linear range) and a detection limit 5.0 microM. The effect of lipophilic anionic (tetraphenylborate derivatives) and cationic (tetraalkylammonium) site additives within the membrane on the anion selectivity is examined in detail. Addition of both cationic and anionic sites is shown to improve potentiometric anion selectivity, suggesting that the palladium complex may operate simultaneously as a neutral and charged carrier-type ionophore within the polymer membrane phase. Using optimal membrane formulations (with added 20-30 mol % cationic sites), the sensors prepared with the palladium complex do not exhibit proton/hydroxide response in the range of pH 3.5-12, a potential advantage over previously reported nitrite electrodes prepared with Co(III) corrins and porphyrin complexes. 相似文献
153.
AG Bostom RY Gohh MY Tsai BJ Hopkins-Garcia MR Nadeau LA Bianchi PF Jacques IH Rosenberg J Selhub 《Canadian Metallurgical Quarterly》1997,17(10):1894-1900
Hyperhomocysteinemia, either fasting or after methionine loading, may contribute to the increased incidence of cardiovascular disease events experienced by renal transplant recipients. Limited data are available on fasting homocysteine (Hcy) levels, and none on postmethionine-loading Hcy levels, in these patients. We assessed the prevalence and potential determinants of fasting and postmethionine-loading hyperhomocysteinemia in 29 stable renal transplant recipients and 58 age- and sex-matched, population-based controls free of renal disease with serum creatinine levels of 1.5 mg/dL or less. Total (t) plasma Hcy was determined fasting and 2 hours after methionine loading, along with fasting determinations of the B-vitamin cofactors/substrates for Hcy metabolism, ie, pyridoxal 5'-phosphate, B-12, and folate and serum creatinine. Geometric mean fasting (18.1 versus 9.8 microM, P < .001) and postmethionine-loading increase (22.0 versus 15.2, P = .001) in tHcy levels were significantly greater in the renal transplant recipients, as were the prevalence odds (with 95% confidence intervals) for fasting [14.8 (3.4-64.7)], postmethionine loading [6.9 (1.5-32.8)], combined fasting and postmethionine-loading [18.0 (2.3-142.1)] hyperhomocysteinemia, and inadequate circulating folate [4.2 (1.1-16.5)] or pyridoxal 5'-phosphate [3.2 (0.9-11.0) status. Correlation analyses suggested important potential relationships between creatinine and both fasting (+0.64, P < .001) and postmethionine-load increase (+0.38, P = .045) in tHcy, folate and fasting (-0.41, P = .025) tHcy, and pyridoxal 5'-phosphate and postmethionine-loading increase (-0.33, P = .091) in tHcy. We conclude that there is an excess prevalence of fasting and postmethionine-loading hyperhomocysteinemia in stable renal transplant recipients. Renal function is related to both fasting and postmethionine loading-hyperhomocysteinemia, inadequate folate status is associated with fasting hyperhomocysteinemia, and inadequate vitamin B-6 status may be related to postmethionine-loading hyperhomocysteinemia in this patient population. 相似文献
154.
JJ Dias IH Thomas AC Lamont BS Mody JR Thompson 《Canadian Metallurgical Quarterly》1993,75(3):479-482
Ultrasound scans were made of the hips of 209 neonates born consecutively over a two-week period. Of the 418 scans, 62 images were selected at random and 25 of these were duplicated to give a total of 87 scans. These static images were then presented to five experienced observers who each made nine different assessments and measurements. Interobserver and intraboserver agreement was calculated and expressed as kappa values. Our results showed poor reliability on both counts. 相似文献
155.
M Dewerchin AM Vandamme P Holvoet F De Cock G Lemmens HR Lijnen JM Stassen D Collen 《Canadian Metallurgical Quarterly》1992,68(2):170-179
A recombinant chimeric plasminogen activator consisting of a humanized monoclonal antibody specific for cross-linked human fibrin (MA-15C5Hu) and a 32 kDa single-chain urokinase-type plasminogen activator (scu-PA-32k) comprising amino acids Leu144-Leu411, MA-15C5Hu/scu-PA-32k, was previously found to have a 12-fold higher fibrinolytic potency than recombinant scu-PA-32k towards a human plasma clot in a human plasma milieu in vitro (Vandamme et al., Eur J Biochem 1992; 205: 139-46). Therefore, the thrombolytic and pharmacokinetic properties of MA-15C5Hu/scu-PA-32k were compared with those of recombinant single-chain urokinase-type plasminogen activator (scu-PA) in 3 different venous thrombosis models in vivo. In hamsters with a pulmonary embolus consisting of a human plasma clot, the thrombolytic potency (% lysis per dose in mg/kg administered) of MA-15C5Hu/scu-PA-32k was 23-fold higher than that of scu-PA (p less than 0.0005). In rabbits with a jugular vein clot prepared from human plasma, the thrombolytic potency of MA-15C5Hu/scu-PA-32k was 11-fold higher than that of scu-PA (p = 0.012). In baboons with an autologous whole blood clot in the femoral vein, the chimera had a 5-fold higher thrombolytic potency than scu-PA. In all three animal species, the clearance of the chimera was 10- to 27-fold reduced as compared to scu-PA. The specific thrombolytic activity (% lysis per micrograms/ml steady-state plasma u-PA antigen) was increased up to 7-fold with MA-15C5Hu/scu-PA-32k as compared with scu-PA, which is indicative of targeting of the chimera to the clot. No fibrinogen breakdown or alpha 2-antiplasmin depletion was observed during thrombolysis with the chimera. Thus, MA-15C5Hu/scu-PA-32k constitutes a recombinant chimeric plasminogen activator with a significantly enhanced thrombolytic potency in 3 different animal models of venous thrombosis. 相似文献
156.
IH Burnley 《Canadian Metallurgical Quarterly》1995,41(5):687-698
Analysis of suicide mortality in New South Wales, Australia is undertaken with reference to marital status and occupational status between 1986-89/90 and with reference to the principal means of committing suicide. Not currently married male manual workers were particularly at risk although marital status variations were significant with both genders and at different ages. Between 1985-91 male suicide mortality rates were significantly higher in inland non-metropolitan regions, especially among younger men, and were higher in inner areas of metropolitan Sydney. While there were no significant variations by marital status in the means of committing suicide there were variations between genders, and there were regional and social class variations in the use of guns with males. The use of guns was a factor in the elevated suicide mortality levels among inland rural youth and men, and among farmers and transport workers while the use of poisons was also significant with these occupational groups. The use of poisons was greater among persons committing suicide in the areas of elevated mortality in inner Sydney and the use of guns much lower. 相似文献
157.
Michielsen K Jacobs J Lemmens K Nens J Zoetelief J Faulkner K Bosmans H 《Radiation protection dosimetry》2008,129(1-3):199-203
For the dose study, a semi-automated method of data collection is used in this study. The participating centres were asked to fill out a spreadsheet with all necessary data and return it. For direct digital (DR) systems, the relevant data available in the DICOM header were used. All data is automatically added to a database and processed. The data were used to calculate the mean glandular dose for every image and for different thicknesses of polymethyl methacrylate phantoms using available conversion factors. Second-degree polynomials were fitted to the patient dose data and a reference dose curve was constructed for a range of thicknesses instead of a dose reference level at a single point. The dose reference curve rises from 1.57 mGy for a thickness of 30 mm to 2.50 mGy for 55 mm and 3.83 mGy for 75 mm. The results show centres that exceed this curve lie only in the lower or higher range of thicknesses and would remain undetected using a dose reference value in a single point. This gives better information to radiographers on where there is room for improvement of the dose levels in their system. 相似文献
158.
159.
Inside Cover: Modulation of Ultrafast Conformational Dynamics in Allosteric Interaction of Gal Repressor Protein with Different Operator DNA Sequences (ChemBioChem 7/2016)
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160.
Modulation of Ultrafast Conformational Dynamics in Allosteric Interaction of Gal Repressor Protein with Different Operator DNA Sequences
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Susobhan Choudhury Gitashri Naiya Priya Singh Prof. Peter Lemmens Prof. Siddhartha Roy Prof. Samir Kumar Pal 《Chembiochem : a European journal of chemical biology》2016,17(7):605-613
Although all forms of dynamical behaviour of a protein under allosteric interaction with effectors are predicted, little evidence of ultrafast dynamics in the interaction has been reported. Here, we demonstrate the efficacy of a combined approach involving picosecond‐resolved FRET and polarisation‐gated fluorescence for the exploration of ultrafast dynamics in the allosteric interaction of the Gal repressor (GalR) protein dimer with DNA operator sequences OE and OI. FRET from the single tryptophan residue to a covalently attached probe IAEDANS at a cysteine residue in the C‐terminal domain of GalR shows structural perturbation and conformational dynamics during allosteric interaction. Polarisation‐gated fluorescence spectroscopy of IAEDANS and another probe (FITC) covalently attached to the operator directly revealed the essential dynamics for cooperativity in the protein–protein interaction. The ultrafast resonance energy transfer from IAEDANS in the protein to FITC also revealed different dynamic flexibility in the allosteric interaction. An attempt was made to correlate the dynamic changes in the protein dimers with OE and OI with the consequent protein–protein interaction (tetramerisation) to form a DNA loop encompassing the promoter segment. 相似文献