颈动脉内膜切除术的恰当应用

在颈动脉内膜切除术(CEA)首创的头30年里,一直没有明确的标准来确定哪些颈内动脉疾病患者适合这一手术.最近,从7项临床随机试验中得出了哪些有症状与无症状患者适合行CEA的结论.对于颈内动脉狭窄70%以上的患者,卒中的危险性最大,手术的益处也最大.在这些研究中,CEA对以下患者最有益半球短暂性脑缺血发作、颅内外联合病灶和无侧支循环且除此之外身体状况良好的老年患者.下列患者虽然能从手术中获益,但围手术期卒中和死亡的危险性较高广泛白质疏松、对侧颈内动脉闭塞和腔内有血栓者.狭窄50%～69%的患者较少获益,包括女性和仅有一过性单眼盲在内的一些患者行CEA甚至可能有害.腔隙性卒中和一侧颈内动脉接近闭塞的患者有手术指征,但益处不大;狭窄＜50%的患者不能从手术中获益.在最大的一项无症状患者随机试验中,围手术期卒中和死亡的危险性非常小(1.5%),但要在2年内防止1例卒中发生需要相当多的病例(83例)接受CEA治疗.以后的文献报道围手术期危险性较高(2.8%～5.6%).近一半无症状患者的卒中是心源性栓塞和小血管疾病所致.这些局限性抵消了任何潜在的益处.其他试验正在进行,并可能确认哪些无症状患者亚组可从手术中获益.同时,大多数无症状患者内科治疗效果也较好.     

Amnesic Concentrations of the Nonimmobilizer 1,2-Dichlorohexafluorocyclobutane (F6, 2N) and Isoflurane Alter Hippocampal θ Oscillations In Vivo

Background: Drug-induced temporary amnesia is one of the principal goals of general anesthesia. The nonimmobilizer 1,2-dichlorohexafluorocyclobutane (F6, also termed 2N) impairs hippocampus-dependent learning at relative, i.e., lipophilicity-corrected, concentrations similar to isoflurane. Hippocampal [theta] oscillations facilitate mnemonic processes in vivo and synaptic plasticity (a cellular model of memory) in vitro and are thought to represent a circuit level phenomenon that supports memory encoding. Therefore, the authors investigated the effects of F6 and isoflurane on [theta] oscillations (4-12 Hz).

Methods: Thirteen adult rats were implanted with multichannel depth electrodes to measure the microelectroencephalogram and were exposed to a range of concentrations of isoflurane and F6 spanning the concentrations that produce amnesia. Five of these animals also underwent control experiments without drug injection. The authors recorded the behavioral state and hippocampal field potentials. They confirmed the electrode location postmortem by histology.

Results: The tested concentrations for isoflurane and F6 ranged from 0.035% to 0.77% and from 0.5% to 3.6%, respectively. Isoflurane increased the fraction of time that the animals remained immobile, consistent with sedation, whereas F6 had the opposite effect. Electroencephalographic power in the [theta] band was less when the animals were immobile than when they explored their environment. F6 suppressed the power of oscillations in the [theta] band. Isoflurane slowed [theta] oscillations without reducing total power in the [theta] band.     

Singularities explained: Response to Klein.

Klein [Klein, A. S. (2006). Separating transducer nonlinearities and multiplicative noise in contrast discrimination. Vision Research, 46, 4279-4293] questions the existence of intrinsic singularities in two-alternative force-choice (2AFC) Signal Detection Theory (SDT) models, suggesting that the singularities found in Katkov et al. [Katkov, M., Tsodyks, M., & Sagi, D. (2006a). Singularities in the inverse modeling of 2AFC contrast discrimination data. Vision Research, 46, 259-266; Katkov, M., Tsodyks, M., & Sagi, D. (2006b). Analysis of two-alternative force-choice Signal Detection Theory model. Journal of Mathematical Psychology, 50, 411-420] are due to discarding higher order terms in the Taylor expansion of d' and/or limited to steep psychometric functions. Here we provide some simple intuitive examples that illustrate the results described in Katkov et al. (2006a, 2006b). We show, for the constant noise model, that singularities exist when exact values of d' are computed and that the singularities are not limited to steep psychometric functions. In these cases the disambiguation of the different models requires millions of trials.     

Depression, Night Terrors, and Insomnia Associated With Long-Term Intrathecal Clonidine Therapy

Abstract:   Intraspinal clonidine is an effective adjunct to intrathecal/epidural opioid administration. We report a case of neuropathic pain treated with intraspinal analgesics in which depression, insomnia, and night terrors developed in association with intraspinal clonidine.     

Multiple mechanisms govern the dynamics of depression at neocortical synapses of young rats

Synaptic transmission between pairs of excitatory neurones in layers V ( N = 38) or IV ( N = 6) of somatosensory cortex was examined in a parasagittal slice preparation obtained from young Wistar rats (14–18 days old). A combined experimental and theoretical approach reveals two characteristics of short-term synaptic depression. Firstly, as well as a release-dependent depression, there is a release-independent component that is evident in smaller postsynaptic responses even following failure to release transmitter. Secondly, recovery from depression is activity dependent and is faster at higher input frequencies. Frequency-dependent recovery is a Ca²⁺-dependent process and does not reflect an underlying augmentation. Frequency-dependent recovery and release-independent depression are correlated, such that at those connections with a large amount of release-independent depression, recovery from depression is faster. In addition, both are more pronounced in experiments performed at physiological temperatures. Simulations demonstrate that these homeostatic properties allow the transfer of rate information at all frequencies, essentially linearizing synaptic responses at high input frequencies.     

The Feasibility of Using Computrition Software for Nutrition Research—A Pilot Study

We evaluated the feasibility of using Computrition to design and implement a low vs. typical sodium meal plan intervention for older adults. Dietitians used Computrition to design a 7-day meal plan with three caloric levels (≤1750, 2000, ≥2250 kcals/day) and two sodium densities (low = 0.9 mg/kcal; n = 11 or typical = 2 mg/kcal; n = 9). Feasibility was determined by post-hoc definitions of effectiveness, sodium compliance, palatability of diet, sustainability, and safety. Given the low number of participants in one of the three calorie groups, the higher calorie groups were combined. Thus, comparisons are between low vs. typical meal plans at two calorie levels (≤1750 or ≥2000 kcals/day). Overall, regardless of the calorie group, the meal plans created with Computrition were effective in reaching the targeted sodium density and were safe for participants. Furthermore, individuals appeared to be equally compliant and reported similar palatability across meal plans. However, one of the three criteria for the sustainability definition was not met. In conclusion, we successfully used Computrition to design low and typical sodium meal plans that were effective, compliable, and safe. Future studies of older adults in similar settings should focus on improving the palatability of the meal plans and scaling this protocol to larger studies in older adults.     

考马斯亮蓝染色法检测人精子顶体反应的评价

为建立一种检测人精子顶体反应的简便实用的新技术，用３．５％高氯酸水溶液配制０．０５％考马斯亮蓝（Ｒ２５０）染色液浸染人精子３０ｍｉｎ，顶体完整者顶体区染成紫蓝色，顶体反应者则不染。对获能前后和钙离子载体Ａ２３１８７诱导顶体反应的精子进行染色并与经典的顶体反应检测技术ＰＳＡ法对照，两种方法检测顶体反应率无显著差异。方法学检验证明新技术结果可靠。本法操作简便、经济，普通显微镜即可检测，易于推广，克服了原有技术复杂昂贵的缺点，具有研究和临床诊断的良好价值。     

Angiographically defined collateral circulation and risk of stroke in patients with severe carotid artery stenosis. North American Symptomatic Carotid Endarterectomy Trial (NASCET) Group

BACKGROUND AND PURPOSE: Blood supply through collateral pathways improves regional cerebral blood flow and may protect against ischemic events. The effect of collaterals on the risk of stroke and transient ischemic attack (TIA), in the presence of angiographic severe internal carotid artery (ICA) stenosis, was assessed. METHODS: Angiographic collateral filling through anterior communicating and posterior communicating arteries and retrograde filling through ophthalmic arteries were determined in all patients at entry into the North American Symptomatic Carotid Endarterectomy Trial. Kaplan-Meier event-free survival analyses were performed on 339 medically treated and 342 surgically treated patients. RESULTS: The presence of collaterals supplying the symptomatic ICA increased with severity of stenosis. Two-year risk of hemispheric stroke in medically treated patients with severe ICA stenosis was reduced in the presence of collaterals: 27.8% to 11.3% (P=0.005). Similar reductions were observed for hemispheric TIA (36.1% versus 19.1%; P=0.008) and disabling or fatal strokes (13.3% versus 6.3%; P=0.11). For surgically treated patients, the perioperative risk of hemispheric stroke was 1.1% in the presence of collaterals versus 4. 9% when absent. The 2-year stroke risks for surgical patients with and without collaterals were 5.9% versus 8.4%, respectively. Neither comparison in the surgical group was statistically significant. The observed reductions were independent of the degree of ICA stenosis and other vascular risk factors. CONCLUSIONS: Collaterals are associated with a lower risk of hemispheric stroke and TIA, both long term and perioperatively. Angiographic identification of collaterals assists in identifying patients with severe ICA stenosis at lower risk of stroke and TIA.