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排序方式: 共有6930条查询结果,搜索用时 31 毫秒
61.
OBJECTIVE: To evaluate the influence of a brief period of sleep deprivation on cardiac autonomic controls during sleep in healthy infants. DESIGN: Twelve healthy infants with a median age of 8 weeks (range, 7 to 18 weeks) were recorded polygraphically during a morning and an afternoon nap in a sleep laboratory. They were sleep deprived for approximately 2 hours, either in the morning or in the afternoon, before being allowed to fall asleep. Six infants were sleep deprived before the morning nap, and 6 before the afternoon nap. During both naps, their sleep, breathing, and heart-rate characteristics were continuously recorded. Spectral analysis of heart rate was evaluated as a function of sleep stages. Two major peaks were recognizable: a low-frequency component related to sympathetic and parasympathetic activities and a high-frequency component reflecting parasympathetic tonus. The ratio of low-frequency to high-frequency powers was calculated as an index of sympathovagal interaction. RESULTS: When sleep deprived, the infants had an increase in basal heart rate during non-rapid eye movement sleep (P=.021). With sleep deprivation, the ratio of low-frequency to high-frequency powers increased in non-rapid eye movement sleep (P=.005). These findings were consistent with an increase in sympathetic tone. CONCLUSION: Infants exposed to short-term sleep deprivation manifest changes in cardiac autonomic controls during sleep. These findings could be relevant to mechanisms associated with the sudden infant death syndrome. 相似文献
62.
63.
Neurofibromatosis 2 (NF2) is an inherited cancer syndrome resulting from
mutations in the NF2 tumor suppressor gene. Analysis of NF2 mutations has
revealed some general genotype-phenotype correlations. Severe disease has
been associated with mutations that produce a premature termination while
more mild disease has been associated with missense mutations. Here, we
provide experimental proof for these genotype-phenotype correlations by
demonstrating that nonsense mutations fail to produce stable merlin protein
while missense mutations result in the generation of merlin proteins
defective in negative growth regulation. This inability to suppress cell
growth may result from defects in the function of merlin at several levels,
including failure to form an intramolecular complex. Based on these
findings, we propose a model for merlin growth suppression that provides a
framework for analyzing NF2 patient mutations and merlin function.
相似文献
64.
G. Brandenberger V. Candas M. Follenius J. M. Kahn 《European journal of applied physiology》1989,58(6):674-679
Summary This study examines the effect of the initial state of hydration on hormone responses to prolonged exercise in the heat. Five subjects at two initial hydration levels (hypohydrated and hyperhydrated) were exposed to a 36°C environment for 3 h of intermittent exercise. During exercise, the subjects were either fluid-deprived, or rehydrated with water or an isotonic electrolyte sucrose solution (ISO). Both the stress hormones, adrenocorticotropic hormone and cortisol, and the main fluid regulatory hormones, aldosterone, renin activity (PRA) and arginine vasopressin (AVP), were measured in blood samples taken every hour. Prior hyperhydration significantly reduced initial AVP, aldosterone and PRA levels. However, except for AVP, which responded to exercise significantly less in previously hyperhydrated subjects (p<0.05), the initial hydration state did not influence the subsequent vascular and hormonal responses when the subjects were fluid-deprived while exercising. Concurrent rehydration, either with water or with ISO, reduced or even abolished the hormonal responses. There were no significant differences according to the initial hydration state, except for PRA responses, which were significantly lower (p<0.01) in previously hyperhydrated subjects who also received water during exercise. These results indicate that prior hydration levels influence only slightly the hormonal responses to prolonged exercise in the heat. Progressive rehydration during exercise, especially when extra electrolytes are given, is more efficient in maintaining plasma volume and osmolarity and in reducing the hormonal responses. 相似文献
65.
JS Pooni Dr DWL Hukins PF Harris RC Hilton KE Davies 《Surgical and radiologic anatomy : SRA》1986,8(3):175-182
Posterior and anterior heights, cross-sectional area and shape were measured for all the intervertebral discs in four spines from elderly human cadavers. Disc height was a minimum at the T4-5 level; thoracic discs were less wedge-shaped than those in the cervical and lumbar regions. Cross-sectional area increased from the cranial to caudal extremity; at the L5-S1 level the nucleus pulposus occupied a high proportion of this area. Cervical discs tended to have an elliptical cross-sectional shape, thoracic discs were more circular and lumbar discs tended to have an elliptical cross-section which was flattened or re-entrant posteriorly. This shape distribution was quantified by defining a shape index which had a maximum value of 1 for a circular cross-section. Orientations of the reinforcing fibres in the outer lamellae of the anterior annulus fibrosus were measured from 27 discs by X-ray diffraction. For these measurements, C3-4, T7-8 and L2-3 were chosen as representative of cervical, thoracic and lumbar discs. The fibre tilt, with respect to the axis of the spine, was significantly less in the cervical discs (at 65 degrees) than in the thoracic and lumbar discs (about 70 degrees). These findings are interpreted in relation to differing functional requirements and possible mechanisms of failure in the cervical, thoracic and lumbar regions of the spine in the light of current knowledge on the biomechanics of the intervertebral disc. 相似文献
66.
Nabarra B Martinon C Godard C Vasseur F de Ribains G Miquerol L Kahn A Ezine S 《Developmental immunology》2002,9(4):223-231
Bone marrow progenitors migrate to the thymus, where they proliferate and differentiate into immunologically competent T cells. In this report we show that mice transgenic for SV40 T and t antigens under the control of the L-pyruvate kinase promoter develop, in a first step, thymic hyperplasia of both thymocytes and epithelial cells. Morphological studies (histology, immunohistolabeling and electron microscopy) revealed modifications of the thymic microenvironment and gradual expansion of medullary epithelial cells in 1 month-old mice, taking over the cortical region. Then, a thymic carcinoma develops. Two-color labeling of frozen sections identified the transgene in medullary epithelial cells. Flow cytometry analysis demonstrated a marked increase in mature CD4+ and CD8+ thymocytes in adult mice (39 +/- 10 x 10(6) in transgenic mice and 12 +/- 5 x 10(6) in age-matched controls). Furthermore, thymocyte export was disturbed. 相似文献
67.
Popiolek D Kahn E Markowitz J Daum F 《Archives of pathology & laboratory medicine》2000,124(8):1165-1167
BACKGROUND: Pancreatic acinar tissue (PAT) at the gastroesophageal junction (GEJ) has been reported in 3% of adults with Barrett esophagus (BE) and in 24% of healthy subjects. The pathogenesis of this ectopic tissue is controversial. Both an acquired metaplastic process in the setting of BE and a congenital abnormality have been suggested in adults. OBJECTIVE: To clarify the origin of PAT at the GEJ. METHODS: We reviewed material obtained from the GEJ in 69 children and young adults. Each specimen was evaluated by 3 levels stained with hematoxylin-eosin for the presence of PAT, BE, esophagitis, and gastritis. Selected cases were also examined with immunohistochemical stains for lipase, trypsin, and amylase. RESULTS: In 16% of the study population, PAT was present at the GEJ and was not associated with BE. The prevalence of esophagitis and/or gastritis did not vary significantly between patients with and without PAT. CONCLUSIONS: Our data suggest that PAT at the GEJ develops independently of inflammation and is, therefore, likely to be congenital. 相似文献
68.
Role of antibody to S100 protein in diagnostic pathology 总被引:1,自引:0,他引:1
69.
70.
Temporal factors influence recovery of function after embryonic brain tissue transplants in adult rats with frontal cortex lesions 总被引:2,自引:0,他引:2
Adult rats with lesions of the medial frontal cortex received implants of frontal cortex taken from embryos on the 19th day of gestation and placed directly into the zone of injury at 7, 14, 30, or 60 days after initial surgery. Another group was given bilateral frontal lesions, followed 20 days later by a second small lesion to enhance the release of putative neurotrophic factors. They then received transplants 7 days after this second operation. All rats began postoperative training on a spatial alternation learning task within 4 days after the implants of fetal tissue. The brain-damaged rats with transplants at 7 or 14 days after surgery significantly improved postoperative acquisition of spatial alternation. Transplants made 30 or 60 days postoperatively had no effect; these groups were as impaired as those with lesions alone. The animals given a second, "priming" lesion after a 20-day delay, followed by implants of fetal brain tissue, performed as poorly as the group with frontal cortex lesions alone. 相似文献