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51.
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We report a case of a small, isolated paraspinal arteriovenous fistula (AVF) that arose in an adult without obvious trauma. The fistula, despite its extraspinal location and small size, caused hypertension of the intrathecal venous system and produced symptoms that were similar to those of spinal dural AVF. Detecting such a small lesion is difficult, but contrast-enhanced MR imaging can prove helpful in this regard. 相似文献
53.
Richard W. Bowtell Andrew Peters Jonathan C. Sharp Peter Mansfield Edward W. Hsu Nanci Aiken Anthony Horsman Stephen J. Blackband 《Magnetic resonance in medicine》1995,33(6):790-794
NMR microimages of single neural cells were acquired at 500 MHz using a conventional spin echo pulse sequence and a line-narrowing sequence that eliminates susceptibility effects. The data show that any contribution to the measured T2 relaxation rate arising from diffusion in local field inhomogeneities using spin echo sequences at high fields and high spatial resolution is relatively small. We conclude that the measured T2 difference between the nucleus and cytoplasm in these cells represents primarily a true T2 relaxation effect arising from the interactions of water with macromolecules in the two compartments and does not result from microsusceptibility differences. These observations have implications regarding water compartmentation in single cells and the interpretation of the MR characteristics of tissues in vivo. 相似文献
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Metabolic clearance rate (MCR) and production rate (PR) of calcitriol is decreased in experimental renal failure. In this experiment, we studied uremia and secondary hyperparathyroidism as possible causes of the abnormal calcitriol metabolism. Normal rats were made uremic by infusing phosphorus-free urine for 24 hours. Both the MCR (0.22 +/- 0.01 ml/min/kg, N = 6 P less than 0.001) and the PR (16.6 +/- 1.97 ng/kg/day, P less than 0.01) of calcitriol were significantly suppressed in normal rats following urine infusion when compared to saline infused rats (MCR, 0.30 +/- 0.01; PR, 32.9 +/- 4.1, N = 6). Different levels of protein intake by rats with renal failure produced by subtotal nephrectomy also alter the PR but not the MCR of calcitriol. Thus, the synthesis of calcitriol was significantly lower in rats with renal failure fed a high protein (50% protein) diet (17.6 +/- 0.7 ng/kg/day, N = 8, P less than 0.001) than in rats with renal failure fed a normal protein (20% protein) diet (22.2 +/- 1.4, N = 7). Thyroparathyroidectomy (TPTX) did not alter the MCR of calcitriol in renal failure, even though parathyroid hormone, which may suppress the degradation enzyme, could be elevated in this model of renal failure. The MCR of TPTXed rats with renal failure (0.15 +/- 0.01 ml/min/kg, N = 7) remained lower than that of the TPTXed control rats (0.19 +/- 0.01, N = 7, P less than 0.001), and chronic infusion of PTH to TPTXed rats with renal failure did not change the MCR of calcitriol (0.15 +/- 0.01, vs. control, 0.24 +/- 0.01).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
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Deng-Shan Chen Ging-Ho Hsiue Chain-Shu Hsu 《Macromolecular chemistry and physics.》1992,193(6):1469-1479
Two kinds of side-chain liquid-crystalline (LC) polymers with different side-chain mesogenic end groups were synthesized. The laminated membrane was prepared by sandwiching the side-chain LC polymer between two porous polypropene (Celgard) films. Permeation properties for O2, N2, CO2 and CH4 through the laminated side-chain LC polymer-based membranes were measured using a gas-chromatographic method at several temperatures corresponding to the stability range of the different phases of the side-chain LC polymers. The gas permeation behaviour depends strongly on the state of the side-chain LC polymer. The activation energy for permeation depends on the state, too. The plot of separation factor P/P versus P exhibits an unusual behaviour. P/P increases with P when the temperature rises and the phase of the side-chain LC Polymer changes from the glassy state to the liquid-crystalline state. The magnitude of gas permeability coefficients for the laminated membranes is rather low compared to those of some common polymers. The low gas permeability seems to originate from the low gas solubility rather than from the low gas diffusivity in the laminated side-chain LC polymer membrane. 相似文献
59.
The biomechanical properties and histocompatibility of a glutaraldehyde-treated xenograft were examined after implanting it in 27 rabbits. This xenograft was used as an Achilles tendon substitute placed in vivo for 2 to 48 wk. The specimens were then subjected to mechanical strength testing using a specially constructed tensioning device. The contralateral Achilles tendon was used as the reference baseline. Mechanical testing showed that the strength of the implanted graft increased to 33.5% of the normal side at week 10 and to 79.5% at week 14. The host generated a fibrous cord around the xenograft, linking the two ends of the Achilles tendon. Light and electron microscopic examination showed fibroblastic infiltration of varying magnitude in all specimens but no statistical correlation between degree of infiltration and duration of implantation was found. Also, there was no histological evidence of immunological rejection within the 48 wk of study. 相似文献
60.
Coexpression of galanin and adrenocorticotropic hormone in human pituitary and pituitary adenomas. 下载免费PDF全文
D. W. Hsu S. C. Hooi E. T. Hedley-Whyte R. M. Strauss L. M. Kaplan 《The American journal of pathology》1991,138(4):897-909
Galanin is a neuropeptide that regulates the secretion of several pituitary hormones, including prolactin (PRL) and growth hormone (GH). Galaninlike immunoreactivity (Gal-IR) and galanin mRNA in the rat anterior pituitary is cell lineage specific, with predominant expression in lactotrophs and somatotrophs. The authors examined the cellular distribution of human Gal-IR in seven normal postmortem pituitaries and 62 pituitary tumors by immunoperoxidase staining. In contrast to the rat, Gal-IR in human anterior pituitaries was present in corticotrophs scattered throughout the gland, but not in lactotrophs, somatotrophs, thyrotrophs, or gonadotrophs. Distinct Gal-IR also was present in hyperplastic and neoplastic corticotrophs in 19 of 22 patients with Cushing's disease. In noncorticotroph cell tumors, unequivocal Gal-IR was present in 5 of 11 GH-secreting tumors associated with clinical acromegaly, 9 of 18 nonfunctioning pituitary adenomas, and 2 of 14 prolactinomas. Of these galanin-positive tumors, four of the five GH-secreting adenomas, six of the nine nonfunctioning adenomas, and both of the prolactinomas also contained adrenocorticotropic hormone immunoreactivity (ACTH-IR). Immunostaining and in situ hybridization on adjacent sections using an 35S-labeled probe complementary to human galanin mRNA demonstrated predominant galanin expression in normal corticotrophs. Immunoelectron microscopy confirmed the presence of Gal-IR in pituitary cells characteristic of corticotrophs in both normal and neoplastic pituitaries. Thus, as in the rat, galanin gene expression in the human pituitary is cell-type specific. Unlike the rat, however, human galanin gene expression is restricted to the corticotroph lineage. Studies of tumors confirmed the observed coexpression of galanin and adrenocorticotropic hormone. The divergent cell type specificity of galanin production in human and rat pituitaries reflects different patterns of gene activation in these two species. In addition, these results suggest that galanin in the human pituitary may participate locally in the regulation of the hypothalamic-pituitary-adrenal axis. 相似文献