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81.
82.
Continuous intracameral infusions of a balanced salt solution (0.175 microliter min-1) have been reported to raise intraocular pressure (IOP) in anesthetized rats. Palm et al. (1995) previously reported that this effect was attenuated significantly by inclusion of arginine-vasopressin (AVP, 10 ng 0.175 microliter-1) in the infusate. This study used experimental and computer simulation methods to investigate factors underlying these changes in IOP. First, constant intracameral infusions of artificial cerebrospinal fluid (aCSF) at different fixed rates (0.049-0.35 microliter min-1) were used to estimate the outflow resistance. Secondly, IOP responses were measured during an 2 hr intracameral infusion of either aCSF or AVP that was the sum of a small constant component (0.05 microliter min-1) and a larger periodic component (0.25 microliter min-1, cycling for 4 min on, then 4 min off); the mean infusion rate was 0.175 microliter min-1. As shown previously for 0.175 microliter min-1 constant infusions, the periodic aCSF infusion induced a significant rise in IOP that was attenuated by AVP administration. Complex demodulation analysis and the estimated gain parameter of a second order transfer function fit to the periodic responses indicated that outflow resistance increased significantly during the infusions in both aCSF and AVP groups, but that the indices of resistance did not differ significantly between aCSF and AVP infused eyes. This finding implies that changes in outflow resistance do not explain the difference in IOP responses to intracameral aCSF and AVP. The two responses differed significantly, though, in damping factors, such that the aCSF responses were considerably more underdamped than the AVP responses. It is hypothesized that aCSF-induced increase in IOP reflects both (1) a small component reflecting increased outflow resistance and (2) a larger non-resistive component. Since the non-resistive component is insensitive to pretreatment with acetazolamide, it is suggested that the aCSF-induced elevation in IOP reflects primarily vascular perfusion changes that are reduced by local vasoconstrictor actions of AVP. The latter mechanism likely maintains vascular perfusion of the globe when intraocular hypertension develops. 相似文献
83.
长25-29井在完井阶段通井过程中发生粘附卡钻事故,在处理卡钻过程中又发生卡套铣筒、井漏、溢流等事故及复杂情况。通过对井下情况的认真分析,采取先堵漏后循环再解卡的处理方案,顺利地解除了该次卡钻事故,大大地减少了经济损失。 相似文献
84.
The behavioral disturbances of 16 nursing home patients with a history of sundowning behaviour and dementia were treated with light therapy instead of psychopharmacological medication. After the withdrawal of the before established medication a very individual, heterogenous deterioration of the symptoms was noted. A significant improvement of the behaviour was not found by light therapy in any patient. The problems in practical handling and possible consequences of further investigation are discussed. 相似文献
85.
1. Animal studies have shown that angiotensin II has a biphasic effect on urinary sodium excretion. To examine whether this is also true in man, we studied seven salt-replete male subjects in a single-blind placebo-controlled manner. 2. While undergoing maximum diuresis, subjects were infused with 0, 1, 2, 5 or 10 ng of angiotensin II min-1 kg-1 over 80 min. Subjects were studied while seated, and stood every 20 min for urine collection. 3. Angiotensin II produced a dose-dependent antidiuretic effect. The urine flow rate, in ml/min expressed as the change from baseline with increasing dose of angiotensin, was: +3.4 +/- 1.77, -1.26 +/- 0.49 (P < 0.05), -2.75 +/- 1.23 (P < 0.05), -4.21 +/- 0.82 (P < 0.05) and -6.51 +/- 1.07 (P < 0.01). 4. In contrast, the effect of angiotensin II on sodium excretion showed a flat dose-response curve beyond 5 ng min-1 kg-1. The urinary sodium excretion, in mumol/min expressed as the change from baseline with increasing dose of angiotensin, was: 9.5 +/- 21.2, -18.9 +/- 29.6, -37.0 +/- 11.6 (P < 0.05), -67.7 +/- 19.6 (P < 0.01) and -63.8 +/- 14.3 (P < 0.01). 5. The fractional distal reabsorption of sodium, determined by using the lithium clearance technique, showed a rise with all doses of angiotensin II used and reached statistical significance with the top two doses. 6. Unlike antidiuresis, antinatriuresis after graded doses of angiotensin II in human subjects showed a flat dose-response curve beyond 5 ng min-1 kg-1. Pressor doses of angiotensin II also have a significant effect on the distal tubule in promoting sodium reabsorption. 相似文献
86.
AD Rossi E Ahlbom SO Ogren P Nicotera S Ceccatelli 《Canadian Metallurgical Quarterly》1997,117(3):428-436
In the present study the neurotoxic effects of a low dosage (0.5 mg/kg per day) of methylmercury (MeHg) on the developing nervous system were investigated. Pregnant rats were treated with MeHg from day 7 of pregnancy to day 7 of lactation. Locomotor activity (locomotion, rearing, and motility) and spatial learning ability were tested in the offspring at 6 months of age. The expression of tyrosine hydroxylase (TH) was examined by immunohistochemistry and in situ hybridization. A significant decrease in spontaneous motility and rearing was observed only in the MeHg-treated male rats. After administration of a low dose of d-amphetamine (0.5 mg/kg) no differences could be observed between control and MeHg-treated male rats, suggesting that changes in dopaminergic transmission were involved. However, no change in TH messenger RNA expression was observed. No changes in spatial learning acquisition or memory were shown in MeHg-treated rats. Taken together, these findings show that during development a very low dosage of MeHg exerts neurotoxic effects detectable in adulthood, and that susceptibility is gender-dependent. 相似文献
87.
J Berciano J Figols A García E Calle I Illa M Lafarga MT Berciano 《Canadian Metallurgical Quarterly》1997,20(7):846-857
The pathological basis of nerve inexcitability in Guillain-Barré syndrome has not been established with certainty. We report the clinicopathological findings in a 67-year-old patient with fulminant Guillain-Barré syndrome who died 18 days after onset. Three serial electrophysiological studies revealed nerve inexcitability. Antibodies to Campylobacter jejuni were present but there was no antiganglioside reactivity. Spinal root sections revealed extensive and almost pure macrophage-associated demyelination with occasional presence of T lymphocytes and neutrophil leukocytes. Conversely, in femoral, median, and sural nerves the outstanding lesion was axonal degeneration, with some denuded axons remaining. Unmyelinated fibers, posterior root ganglia, and dorsal columns were preserved. Endoneurial postcapillary venules showed plump endothelial cells with loss of their tight junctions. We conclude that both primary demyelination and axonal degeneration secondary to inflammation account for nerve inexcitability. Our findings lend support to the hypothesis of increased endoneurial pressure as the cause of wallerian degeneration in nerve trunks. 相似文献
88.
J Salmon D Levêque JD Peter A Cavalier H Elkha?li Y Salmon G Kaltenbach H Monteil F Jehl 《Canadian Metallurgical Quarterly》1996,44(5):375-378
The purpose of this study was to examine the role of sleep problems in the etiology of nursing caries. Two-hundred mothers of children (104 with nursing caries and 96 caries free) from ages 2 to 4.5 years were surveyed to determine whether difficulty with child sleep and ensuing sleep-associated feeding might be related to the presence of nursing caries. Differences were noted between these two groups regarding: average number of nights the child slept through the night (P < 0.001); total hours of sleep per night (P < 0.05); frequency of night waking episodes (P < 0.01); feeding on demand upon waking (P < 0.01); using a bottle to assist with falling asleep at night (P < 0.001); and feeding in association with nap time (P < 0.001). Differences also were noted in regard to average age of weaning (P < 0.001). Our findings suggest that sleep problems among young children are a behavioral risk factor for night-time bottle use and early childhood caries. 相似文献
89.
90.
A. Ureña J. M. Gomez De Salazar J. Quiñones S. Merino J. Martin 《Journal of Materials Science》1996,31(3):807-817
Diffusion bonds have been produced between sheets of an Al-Li-Cu-Mg-Zr alloy using aluminium-4% copper vapour deposited metallic interlayers. Microstructural changes occurred both in the parent alloy and in the bond interface after diffusion bonding cycles and post-bonding heat treatments were analysed. Different metallographic techniques (light microscopy, scanning and transmission electron microscopy) have been used. Diffusion bonding trials were carried out using the same alloy (AA8090), both in non-superplastic (T6) and superplastic conditions. Differences in their behaviours in relation to diffusion bonding were observed. 相似文献