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131.
Diabetic retinopathy remains a major cause of loss of vision. The Diabetes Control and Complications Trial (DCCT) has implicated hyperglycaemia as a probable major direct causative factor in the pathogenesis of diabetic retinopathy. There are several plausible mechanisms by which high glucose concentrations could lead to the functional and later structural changes characterising diabetic retinopathy. These include increased activity of the aldose reductase pathway, increase de novo synthesis of diacylglycerol from glucose, causing protein kinase C activation, increased non-enzymatic glycation and increased oxidative damage. The demonstration of the potential roles of these pathways and the subsequent effects of growth factors in enhancing angiogenesis provide potential new approaches to the prevention and treatment of diabetic retinopathy. 相似文献
132.
High-resolution EEG mapping of cortical activation related to working memory: effects of task difficulty, type of processing, and practice 总被引:13,自引:7,他引:6
Changes in cortical activity during working memory tasks were examined with
electroencephalograms (EEGs) sampled from 115 channels and spatially
sharpened with magnetic resonance imaging (MRI)-based finite element
deblurring. Eight subjects performed tasks requiring comparison of each
stimulus to a preceding one on verbal or spatial attributes. A frontal
midline theta rhythm increased in magnitude with increased memory load.
Dipole models localized this signal to the region of the anterior cingulate
cortex. A slow (low-frequency), parietocentral, alpha signal decreased with
increased working memory load. These signals were insensitive to the type
of stimulus attribute being processed. A faster (higher-frequency),
occipitoparietal, alpha signal was relatively attenuated in the spatial
version of the task, especially over the posterior right hemisphere. Theta
and alpha signals increased, and overt performance improved, after practice
on the tasks. Increases in theta with both increased task difficulty and
with practice suggests that focusing attention required more effort after
an extended test session. Decreased alpha in the difficult tasks indicates
that this signal is inversely related to the amount of cortical resources
allocated to task performance. Practice-related increases in alpha suggest
that fewer cortical resources are required after skill development. These
results serve: (i) to dissociate the effects of task difficulty and
practice; (ii) to differentiate the involvement of posterior cortex in
spatial versus verbal tasks; (iii) to localize frontal midline theta to the
anteromedial cortex; and (iv) to demonstrate the feasibility of using
anatomical MRIs to remove the blurring effect of the skull and scalp from
the ongoing EEG. The results are discussed with respect to those obtained
in a prior study of transient evoked potentials during working memory.
相似文献
133.
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135.
Basilar venous plexus of the posterior fossa: a potential source of error in petrosal sinus sampling
Sampling of serum from the inferior petrosal sinus can provide important information about the source of elevated adrenocorticotropic hormone (ACTH) levels. This often leads to improved results of pituitary surgery for Cushing disease. The authors describe a successful catheterization technique and illustrate the venous anatomy of the inferior petrosal sinuses and basilar plexus. 相似文献
136.
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138.
VAN HENDE C. DEN; LlSTER D.; MUYLLE E. DR. VET.ME; OOMS L. DR.SC; OYAERT W. PROF.DR.VE 《British journal of anaesthesia》1976,48(9):821-829
Thirteen of 31 Belgian Landrace pigs developed malignant hyperthermia(MH) after breathing halothane. A short period of exercise 1h before the administration of the triggering agent increasedthe incidence of the syndrome to 100% in eight similar pigs.Clinical symptoms were more marked and developed more rapidlyin the exercised pigs. All the reacting pigs became typicallyacidotic, developed rigor and died. Serum Na+, K+, Ca2+, c.p.k.,l.d.h. and protein concentrations were increased to a variableextent during the reaction and there was an increase in p.c.v.also. No hyper-glycaemia was detected in pigs which were restedbefore receiving halothane. Four of the eight exercised pigsbecame markedly hyperglycaemic and plasma noradrenaline increasedto higher values. Phosphocreatine and ATP decreased to low valuesand lactate increased in the muscles of all pigs which reacted.At the time of death, muscle glycogen had decreased significantlyin the rested, but not in the exercised, MH pigs.
*Present address: ARC Meat Research Institute, Langford, BristolBS18 7DY. 相似文献
139.
JL Montastruc ME Llau O. Rascol and JM Senard 《Fundamental & clinical pharmacology》1994,8(4):293-306
Summary— The main clinical features, pathophysiology and underlying mechanisms of drug-induced parkinsonism are reviewed. The clinical manifestations of drug-induced parkinsonism are often indistinguishable from idiopathic Parkinson's disease. However, some subtle differences may exist: for example drug-induced parkinsonism is often associated with tardive dyskinesias, bilateral symptoms and the absence of resting tremor, etc. Besides toxins ( eg manganese, carbon monoxide or MPTP), many drugs are known to produce parkinsonism: dopamine blocking drugs (true neuroleptics used as antipsychotics: phenothiazines, butyrophenones, thioxanthenes but also sulpiride, "hidden" neuroleptics prescribed as anti-nausea or anti-vomiting drugs (such as metoclopramide and other benzamide derivatives), dopamine depleting drugs (reserpine, tetrabenazine), alpha-methyldopa, calcium channel blockers (flunarizine, cinnari-zine, etc). The putative role of other drugs ( eg fluoxetine, lithium, amiodarone) as well as the therapeutic management of this side effect are reviewed. 相似文献
140.
A 1-mm-thick, stationary, ultrahigh-strip-density, focused grid was evaluated with respect to patient radiation dose and mammographic image quality as it affected the resolution of microcalcifications and masses. Radiographic technique was varied to determine the most useful alteration to improve image quality with the grid. Results from 89 patients demonstrated that no improvement in diagnostic ability was found in women with fatty breasts. As breast density increased, the advantage of the grid technique became more apparent. Grid mammography also often solved the problem of questionable microcalcifications with improved visualization of their number and geometry. 相似文献