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排序方式: 共有272条查询结果,搜索用时 15 毫秒
71.
Morizono H; Listrom CD; Rajagopal BS; Aoyagi M; McCann MT; Allewell NM; Tuchman M 《Human molecular genetics》1997,6(6):963-968
Although many mutations in the ornithine transcarbamylase gene have been
correlated with 'late onset' of hyperammonemia in patients, the effects of
these mutations on enzyme function are largely unknown. Three recurrent
mutations (R40H, R277W and R277Q) found in patients with 'late onset'
disease were incorporated into 'mature' human ornithine transcarbamylase
cDNA and overexpressed in Escherichia coli. The three recombinant mutant
enzymes were purified to homogeneity on an affinity column and their
biochemical characteristics were compared to the wild type enzyme. The
R277W and R277Q mutants display markedly reduced affinity for L-ornithine,
loss of substrate inhibition, alkaline shift of pH optimum, and reduced
thermal stability compared to the wild type enzyme. These differences,
particularly the reduced affinity for L-ornithine, are sufficient to
account for their biochemical effects. In contrast, the 'mature' R40H
mutant was biochemically indistinguishable from the wild type enzyme in
vitro.
相似文献
72.
Background: The incidence of pseudoaneurysm has increased due to the large number of vascular procedures performed and the widespread use of anticoagulation therapy during procedures. Non-invasive methods for management of pseudoaneurysms comprise of ultrasound guided compression (USGC), thrombin therapy, arterial embolisation and endovascular stent graft insertion. We discuss our experience in the management of fourteen cases of pseudoaneurysms using non surgical techniques. 相似文献
73.
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75.
MR sialography. Work in progress 总被引:10,自引:0,他引:10
76.
Simulated pulmonary nodules: detection with dual-energy digital versus conventional radiography 总被引:9,自引:0,他引:9
Niklason LT; Hickey NM; Chakraborty DP; Sabbagh EA; Yester MV; Fraser RG; Barnes GT 《Radiology》1986,160(3):589-593
Performance of a prototype dual-energy digital chest radiography unit in detecting calcified and noncalcified simulated pulmonary nodules was compared with that of a highly optimized, conventional system. Nodules ranging in size (0.5, 1.0, and 1.6 cm), in number (five to 11), and in calcium content (0-25 mg) were superimposed over the lungs of a frozen, unembalmed, human chest phantom. For each technique, six observers examined 50 posteroanterior projections with different randomized nodule locations. Detection consisted of locating and assigning a level of confidence to each perceived nodular opacity. The resulting plots of the true-positive fraction versus the mean number of false-positive calls per projection indicate that for both calcified and noncalcified nodules, the digital unit performed significantly better (P less than .01). 相似文献
77.
C Rongen-Westerlaken E vd Born B Prahl-Andersen A v Teunenbroek P Manesse BJ Otten I vd Tweel AM Kuijpers-Jagtman HA Delemarre vd Waal NM Drayer JM Wit JL vd Brande 《Acta paediatrica (Oslo, Norway : 1992)》1993,82(4):364-368
A cephalometric study was performed in 19 patients with Turner's syndrome, aged 8.7–16.5 years. A lateral roentgencephalogram was taken before and after two years of treatment with biosynthetic growth hormone in a dose of 24 IU/m2 /week. During two years of growth hormone treatment, the mandibular length increased mainly due to vertical growth. The initially posteriorly rotated mandible showed an anterior rotation, although the normal position was not reached. The other linear measurements and angles did not change during treatment. No indications were found for an increase in the disproportionate growth or for excessive chin growth as a sign of acromegaly during growth hormone treatment. In conclusion, growth hormone treatment in patients with Turner's syndrome resulted in an increase in mandibular length, mainly due to vertical growth of the ramus and in the anterior rotation of the mandible. 相似文献
78.
Stark DD; Moseley ME; Bacon BR; Moss AA; Goldberg HI; Bass NM; James TL 《Radiology》1985,154(1):137-142
Experimental animals that had been given excess iron in their diet were studied by magnetic resonance (MR) imaging in vivo and by magnetic resonance (MR) spectroscopy in vitro. Hepatic iron overload in patients with transfusional iron excess was studied by MR imaging, and isolated iron protein fractions were studied in vitro by MR spectroscopy. The spin echo image intensity of livers with iron overload was decreased because of the extreme decreases in T2 compared with normal; T1 was decreased only moderately. The relaxation rates 1/T2 and 1/T1 both showed a linear relationship to hepatic iron levels. Ferritin solutions showed moderate decreases in T2 and mild decreases in T1. The T2 relaxivity of ferritin, which is due to the iron core rather than the apoferritin protein shell, does not appear sufficient to account for the extreme decrease in T2 observed in hepatic iron overload. Low molecular weight cytosol iron is present in lower concentrations than ferritin but potentially has much greater relaxivity and may contribute to the MR findings. These techniques may be useful in other studies of iron metabolism. 相似文献
79.
80.
Suzanne GM Stomp-van den Berg Mireille NM van Poppel Ingrid JM Hendriksen David J Bruinvels Kimi Uegaki Martine C de Bruijne Willem van Mechelen 《BMC public health》2007,7(1):43