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991.
One major obstacle to human space exploration is the possible limitations imposed by the adverse effects of long-term exposure to the space environment. Even before human space flight began, the potentially brief exposure of astronauts to the very intense random solar energetic particle events was of great concern. A new challenge appears in deep-space exploration from exposure to the low-intensity heavy-ion flux of the galactic cosmic rays since the missions are of long duration, and accumulated exposures can be high. Because cancer induction rates increase behind low to moderate thicknesses of aluminum shielding, according to available biological data on mammalian exposures to galactic cosmic ray-like ions, aluminum shield requirements for a Mars mission may be prohibitively expensive in terms of mission launch costs. Alternative materials for vehicle construction are under investigation to provide lightweight habitat structures with enhanced shielding properties. In the present paper, updated estimates for astronaut exposures on a Mars mission are presented and shielding properties of alternative materials are compared with aluminum. 相似文献
992.
A 28-year-old woman presented following a seizure. Physical and neurological examinations showed no significant abnormality except a drowsy mental state. Routine laboratory studies were normal. Emergency MR imaging showed a rounded, high signal intensity lesion with a focal eccentric heterogeneous signal focus in the right frontal lobe. The heterogeneous focus revealed an irregular low signal rim on T1- and T2-weighted images. Mild surrounding parenchymal oedema was noted. The eccentric focus showed some central enhancement. The diagnosis of cavernous vascular malformation with intracerebral haematoma was confirmed at surgery. The combination of typical MR imaging findings, with clinical and family histories consistent with cavernous angiomata provides sufficient conclusive evidence. 相似文献
993.
肾上腺素诱导兔血小板聚集的实践与理论探讨 总被引:1,自引:0,他引:1
目的创建以Adr诱导兔血小板聚集的方法,并对受体分子特性作初步探讨。方法以高K+缓冲液等取代兔PRP中血浆,以Adr诱导聚集,以Apyr证实结果。结果兔血小板悬浮于高K+缓冲液时Adr能单独诱导真正的聚集。结论由此推测血小板膜上α2肾上腺素受体分子可能为由两种亚单位组成:促聚亚单位和辅助亚单位。人辅助亚单位当Adr浓度高达聚集阈值以上时可被激活,与促聚亚单位结合为活性的二聚体,与Adr进一步结合发生聚集作用。兔辅助亚单位则还需要高K+方能被激活 相似文献
994.
As a 24--iner consisting of different proportions of two main subunit types, named L and H,ferritin is a protein involved in iron storage. Inmammalian tissues, ferritin exists in differentmolecular forms (isoferritins )LI,2]. Previous studies showed that the acidic isoform of ferritin existing in the placenta, fetal tissues and malignant tissues was abnormally increased in the sera of patients with malignancies as well as in pregnantwomen at risk of having small--for--gestational ageinfants[3… 相似文献
995.
Pulmonary tuberculosis in five young infants with nursery exposure: clinical, radiographic and CT findings 总被引:4,自引:0,他引:4
K.-I. Kim J. W. Lee Jae Hong Park Su Young Kim Hee Ju Park Phil Jo Choi Ki Nam Lee H. J. Kim Suk Hong Lee 《Pediatric radiology》1998,28(11):836-840
Clinical, radiographic (n = 5) and CT findings (n = 4) of five Korean infants ranging in age from 2 to 3 months with confirmed tuberculosis were retrospectively analysed.
All of the patients were symptomatic, anergic to tuberculin, and had a positive culture of Myobacterium tuberculosis in gastric aspirates. The probable source of infection was the hospital in which they were born. CT scans demonstrated hilar
and mediastinal lymph node enlargement with central low attenuation and peripheral enhancement in all cases. CT may be useful
in diagnosis by demonstrating characteristic adenopathy and disseminated disease in young infants.
Received: 2 September 1997 Accepted: 23 April 1998 相似文献
996.
Inhibition of growth and induction of apoptosis in human cancer cell lines by tea polyphenols 总被引:47,自引:7,他引:47
In order to study the biological activities of tea preparations and
purified tea polyphenols, their growth inhibitory effects were investigated
using four human cancer cell lines. Growth inhibition was measured by
[3H]thymidine incorporation after 48 h of treatment. The green tea
catechins (-)-epigallocatechin-3-gallate (EGCG) and (-)- epigallocatechin
(EGC) displayed strong growth inhibitory effects against lung tumor cell
lines H661 and H1299, with estimated IC50 values of 22 microM, but were
less effective against lung cancer cell line H441 and colon cancer cell
line HT-29 with IC50 values 2- to 3- fold higher.
(-)-Epicatechin-3-gallate, had lower activities, and (-)- epicatechin was
even less effective. Preparations of green tea polyphenols and theaflavins
had higher activities than extracts of green tea and decaffeinated green
tea. The results suggest that the growth inhibitory activity of tea
extracts is caused by the activities of different tea polyphenols. Exposure
of H661 cells to 30 microM EGCG, EGC or theaflavins for 24 h led to the
induction of apoptosis as determined by an annexin V apoptosis assay,
showing apoptosis indices of 23, 26 and 8%, respectively; with 100 microM
of these compounds, the apoptosis indices were 82, 76 and 78%,
respectively. Incubation of H661 cells with EGCG also induced a
dose-dependent formation of H2O2. Addition of H2O2 to H661 cells caused
apoptosis in a manner similar to that caused by EGCG. The EGCG-induced
apoptosis in H661 cells was completely inhibited by exogenously added
catalase (50 units/ml). These results suggest that tea polyphenol-induced
production of H2O2 may mediate apoptosis and that this may contribute to
the growth inhibitory activities of tea polyphenols in vitro.
相似文献
997.
998.
Objective: To study the pattern of lymphnode metastasis in carcinoma of esophagus. Methods: 200 cases of resected esophageal
cancer specimens were carefully examined pathologically. Lymphnode metastasis, its pathway and extent in relation to pathological
changes were analyzed. Results: Lymphnode metastasis was mainly regional and extended vertically in both directions. Leaping-over
metastasis was another feature. The deeper invasion by the tumor, the higher frequencies of metastasis development, and vice
versa. However, leaping-over metastasis was more likely to occur where tumor invasion was less severe. Conclusion: Owing to
the high frequency of lymphnode metastasis in the superior mediastinum and the widely spanned leaping-over metastasis, an
operative approach by three incisions through right thoracotomy with excision of the whole segment of esophagus and anastomosis
at cervical region was recommended, in order to dissect lymphnodes in the cervical, thoracic and abdominal regions and to
leave less or no metastatic lymphnodes behind. 相似文献
999.
Riley M. Gary I. Kim Norman N. Watson Vance E. Gobin Y. Pierre LeBel Carl P. Black Keith L. Bartus Raymond T. 《Journal of neuro-oncology》1998,36(2):167-178
RMP-7 is a bradykinin B2 receptor agonist shown to permeabilize the blood-brain barrier, especially that associated with brain tumors, when administered via both intracarotid and intravenous routes. Both routes of administration are currently being tested in human trials in combination with the chemotherapeutic agent carboplatin as therapy for gliomas. As an essential prerequisite to the initial intracarotid clinical trials, the potential neurotoxicity of intra-arterial administration of RMP-7 (at a high or low dose), alone and in combination with carboplatin, was assessed in anesthetized Red Duroc swine. Five treatment groups were evaluated with each pig receiving a series of alternating, intra-arterial infusions of RMP-7 (or saline) followed by carboplatin (or saline), as follows: (1) vehicle control: saline/saline; (2) carboplatin only control: saline/carboplatin (50 mg total); (3) RMP-7 only control: RMP-7 (750 ng/kg)/saline; (4) low dose combination: RMP-7 (75 ng/kg)/carboplatin (50 mg total); and (5) high dose combination: RMP-7 (750 ng/kg)/carboplatin (50 mg total). For each subject, one of the alternating dosing sequences (above) was repeated four times during a single dosing session which lasted approximately 40 minutes. Assessments during the in-life phase of the study in the pre- and post-treatment periods consisted of heart rate, arterial blood pressure (systolic, diastolic, and mean), blood gases, body weight, general clinical observations (including evaluation for neurological deficit) and clinical pathology (including a comprehensive battery of standard blood coagulation, hematological and serum chemistry tests). In addition, during the time of treatment, heart rate and arterial blood pressure were monitored. The animals were terminated two weeks after dosing and the brain and rete mirabile (distal to site of infusion) were evaluated for gross and histopathological abnormalities. The histopathology analysis included a reader-blinded analysis using low and high power light microscopic examination of both H&E and Kluver-Berrera stained sections through several key cortical and subcortical brain regions. Transient decreases in arterial blood pressure (mean of 10–25 mmHg) were observed in both groups receiving the high dose of RMP-7 (i.e., 750 ng/kg). No other side effects attributable to RMP-7 and/or carboplatin were observed, and clinical observations revealed no evidence of neurologic deficits. Post-mortem examination revealed no evidence of CNS or cerebral vascular pathology attributable to carboplatin and RMP-7. This study demonstrates that intracarotid administration of the maximum tolerated dose of RMP-7 (750 ng/kg) alone, or in combination with carboplatin (50 mg) is not accompanied by any serious adverse effect, apparent cerebrovascular abnormality or neuropathologic consequence and offers further evidence for the safety of this novel therapeutic approach for enhancing delivery of chemotherapeutics to brain tumors. 相似文献
1000.
A case report of radionuclide bone scan findings in a patient with peroneus brevis tendonitis is presented. Peroneal tendonopathy is a common cause of lateral ankle pain. Although magnetic resonance imaging (MRI) findings have been described in the literature, we know of no other detailed report of three-phase bone scan findings, which we believe can provide an alternate means to diagnose this condition. The positive findings consist of a curvilinear band of increased activity that corresponded to the anatomic position of the peroneus brevis tendon and was detected only on the first two phases of the study. 相似文献