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排序方式: 共有2453条查询结果,搜索用时 15 毫秒
51.
Childhood moyamoya disease: hemodynamic MRI 总被引:2,自引:0,他引:2
A. A. Tzika Richard L. Robertson Patrick D. Barnes Sridhar Vajapeyam Patricia E. Burrows S. T. Treves R. Michael Scott 《Pediatric radiology》1997,27(9):727-735
Background. Childhood moyamoya disease is a rare progressive cerebrovascular disease. Objective. To evaluate cerebral hemodynamics using dynamic Gd-DTPA-enhanced imaging in children with moyamoya disease. Materials and
methods. Eight children (2–11 years of age) with the clinical and angiographic findings typical of moyamoya disease, before
and/or after surgical intervention (pial synangiosis), underwent conventional MR imaging (MRI) and hemodynamic MR imaging
(HMRI). HMRI used a spoiled gradient-echo with low flip angle (10 deg) and long TE (TR/TE = 24/15 ms) to minimize T 1 effects
and emphasize T 2* weighting. Raw and calculated hemodynamic images were reviewed. Three-dimensional time-of-flight MR angiography (MRA) and
perfusion brain single photon emission computed tomography (SPECT) were also performed. Results. Abnormal hemodynamic maps resulting from vascular stenosis or occlusion and basal collaterals were observed in six patient
studies. HMRI depicted perfusion dynamics of affected cerebrovascular territories, detected cortical perfusion deficits, and
complemented conventional MRI and MRA. HMRI findings were consistent with those of catheter angiography and perfusion SPECT.
Conclusion. Our preliminary experience suggests that HMRI may be of value in the preoperative and postoperative evaluation of surgical
interventions in moyamoya disease.
Received: 20 February 1996 Accepted: 4 February 1997 相似文献
52.
53.
BA Evans IA Hughes CL Bevan MN Patterson JW Gregory 《Archives of disease in childhood》1997,76(6):529-531
The androgen insensitivity syndrome is a heterogeneous disorder with a wide spectrum of phenotypic abnormalities, ranging from complete female to ambiguous forms that more closely resemble males. The primary abnormality is a defective androgen receptor protein due to a mutation of the androgen receptor gene. This prevents normal androgen action and thus leads to impaired virilisation. A point mutation of the androgen receptor gene affecting two siblings with partial androgen insensitivity syndrome is described. One had cliteromegaly and labial fusion and was raised as a girl, whereas the other sibling had micropenis and penoscrotal hypospadias and was raised as a boy. Both were shown to have the arginine 840 to cysteine mutation. The phenotypic variation in this family is thus dependent on factors other than abnormalities of the androgen receptor gene alone. 相似文献
54.
OBJECTIVE: Because survival from admission to discharge does not provide parents and physicians information about future life expectancy in the premature neonate, we characterized the actuarial survival, defined as the future life expectancy from a given postnatal age, in a large inborn population of premature infants < 30 weeks' gestation. STUDY DESIGN: We determined daily actuarial survival of 1925 inborn infants (23 to 29 weeks' gestation) admitted to the Baylor Affiliated Nurseries from July 1986 through December 1994, stratified by 100-g birth weight and by 1-week gestational-age intervals. RESULTS: In the 501- to 600-g birth weight stratum, actuarial survival improved from 31% at birth, to 61% on day of life 7, and then to 75% on day of life 28; in the 901- to 1000-g birth weight stratum, actuarial survival improved from 88%, to 94%, and then to 98% throughout the same times, respectively. Similar trends were obtained when data were stratified by gestational age. CONCLUSIONS: Survival in the smallest infants improves dramatically during the first few days of life, but there is a significant risk for late death in the smallest of these infants. 相似文献
55.
Antisense RNA-mediated reduction of p53 induces malignant phenotype in nontumorigenic rat urothelial cells 总被引:2,自引:1,他引:2
p53 mutation is commonly associated with high-grade, high-stage human
urothelial carcinomas. Recent studies suggest that p53 mutation in low-
grade, low-stage bladder carcinomas may be correlated with the progression
of the disease. In the present study, we used antisense RNA methodology in
vitro to evaluate the significance of the loss of p53 function at an early
stage of urinary bladder carcinogenesis. An immortalized nontumorigenic rat
urothelial cell line (MYP3) that strongly expresses wild-type (WT) p53 was
transfected with a plasmid (pcDL-SR alpha-296) containing a rat WT p53 cDNA
in antisense orientation. The transfection resulted in a significant
reduction in p53 mRNA expression and protein synthesis, in stimulation of
anchorage- dependent growth, and in acquisition of anchorage-independent
growth potential. Three such clones, when tested in athymic nude mice, all
formed muscle-invasive, high-grade transitional cell carcinomas at s.c.
injection sites. When cells were inoculated into an orthotopic site
(urinary bladder), one of two antisense transfectants tested formed bulky
tumors in the bladder in all seven nude mice and metastases to lungs in
three of the seven mice. Analysis of these cells revealed a decrease in the
expression of p21 (WAF1, sdi1, or CIP1) and retinoblastoma (Rb) gene
product. Phosphorylation of Rb protein was not inhibited when the cells
were starved. No significant difference was observed in the expression of
p16 protein. In cell cycle analysis, all antisense transfectants tested
escaped from G1 arrest by starvation. Furthermore, secretion of interleukin
(IL)-6 into culture medium was increased significantly. Treatment with
anti-IL-6 antibody suppressed anchorage-dependent growth. This study
directly demonstrates that the loss of p53 function at an early stage of
urothelial carcinogenesis may result in acquisition of a malignant
phenotype by regulating IL-6 production as well as cell cycle related
genes.
相似文献
56.
Xiaoying Yin Hong Zhang Francis Burrows Lin Zhang Carol G Shores 《Clinical cancer research》2005,11(10):3889-3896
Heat shock protein 90 (Hsp90) is a molecular chaperone that promotes the conformational maturation of numerous client proteins, many of which play critical roles in tumor cell growth and survival. The ansamycin-based Hsp90 inhibitor 17-allylamino-17-demethoxygeldanamycin (17-AAG) is currently in phase I/II clinical testing. However, 17-AAG is difficult to formulate and displays weak activity against some tumors. A novel dimeric ansamycin, EC5, was evaluated for antitumor activity in eight head and neck squamous cell carcinoma (HNSCC) cell lines. Both 17-AAG and EC5 inhibited tumor cell proliferation effectively, but EC5 was more potent, with IC(50) below 200 nmol/L in most cell lines tested, including several lines that were resistant to 17-AAG. The inability of 17-AAG to kill JHU12 cells was linked to a defect in retinoblastoma signaling and could be rescued by ectopic expression of p16(INK4a). EC5 induced G(1) growth arrest of tumor cells and apoptosis, with the degradation of client proteins including epidermal growth factor receptor, c-Raf-1, Akt, and Cdk4 and inhibition of Akt phosphorylation. In vivo, EC5 dramatically reduced the growth rate of established HNSCC xenografts in nude mice and decreased expression of epidermal growth factor receptor and Akt within the xenografts. These results suggest that this novel ansamycin-based Hsp90 inhibitor affects multiple pathways involved in tumor development and progression and may represent a new strategy for the treatment of HNSCC patients. 相似文献
57.
Vascular anomalies 总被引:9,自引:0,他引:9
58.
Adam S. Burrows Jeremiah P. Ostriker 《Proceedings of the National Academy of Sciences of the United States of America》2014,111(7):2409-2416
Using basic physical arguments, we derive by dimensional and physical analysis the characteristic masses and sizes of important objects in the universe in terms of just a few fundamental constants. This exercise illustrates the unifying power of physics and the profound connections between the small and the large in the cosmos we inhabit. We focus on the minimum and maximum masses of normal stars, the corresponding quantities for neutron stars, the maximum mass of a rocky planet, the maximum mass of a white dwarf, and the mass of a typical galaxy. To zeroth order, we show that all these masses can be expressed in terms of either the Planck mass or the Chandrasekar mass, in combination with various dimensionless quantities. With these examples, we expose the deep interrelationships imposed by nature between disparate realms of the universe and the amazing consequences of the unifying character of physical law. 相似文献
59.
60.