Measuring Absolute Blood Perfusion in Mice Using Dynamic Contrast-Enhanced Ultrasound

We investigated the feasibility of estimating absolute tissue blood perfusion using dynamic contrast-enhanced ultrasound (CEUS) imaging in mice. We developed a novel method of microbubble administration and a model-free approach to estimate absolute kidney perfusion, and explored the kidney as a reference organ to estimate absolute perfusion of a neuroblastoma tumor. We performed CEUS on the kidneys of CD1 nude mice using the VisualSonics VEVO 2100 imaging system. We estimated individual kidney blood perfusion using the burst–replenishment (BR) technique. We repeated the kidney imaging on the mice after a week. We performed CEUS imaging of a neuroblastoma mouse xenograft tumor along with its right kidney using two sets of microbubble administration parameters to estimate absolute tumor blood perfusion. We performed statistical tests at a significance level of 0.05. Our estimated absolute kidney perfusion (425 ± 123 mL/min/100 g) was within the range of previously reported values. There was no statistical difference between the estimated absolute kidney blood perfusions from the 2 wk of imaging (paired t-test, p = 0.09). We estimated the absolute blood perfusion in the neuroblastoma tumor to be 16.49 and 16.9 mL/min/100 g for the two sets of microbubble administration parameters (Wilcoxon rank-sum test, p = 0.6). We have established the kidney as a reliable reference organ in which to estimate absolute perfusion of other tissues. Using a neuroblastoma tumor, we have determined the feasibility of estimating absolute blood perfusion in tissues using contrast-enhanced ultrasound imaging.     

早期手术治疗胸腰椎爆裂性骨折

目的 :探讨早期手术对胸腰椎爆裂性骨折的治疗价值 ,以选择最佳手术时机。　方法 :采用后路间接椎管扩大、短节段椎弓根螺钉固定技术 ,对 6 7例胸腰椎爆裂性骨折患者进行手术治疗 ,依据手术时间随机分为早期和晚期手术治疗两组。　结果 :6 7例中无神经损伤 32例 ,椎管侵入 (37.16± 15 .15 ) % ;合并神经损伤 35例 ,椎管侵入(4 8.5 9± 16 .89) % ,两组差异显著 (P <0 .0 5 )。早期手术组 2 9例 ,晚期手术组 38例 ,术前侵入椎管比例分别为 (4 3.97± 12 .90 ) %、(4 1.5 2± 16 .15 ) % (P >0 .0 5 )。治疗后早期和晚期手术组侵入椎管比例分别为 (2 0 .6 9± 15 .93) %、(2 7.37± 12 .89) % ,早期组椎管矢状径平均改善 2 3.2 8% ,晚期组为 14.15 % (P <0 .0 5 )。　结论 :胸腰椎爆裂性骨折引起的椎管狭窄与神经损伤密切相关 ,从受伤到手术的时间间隔是影响椎管廓清的重要因素 ,早期手术能改善胸腰椎爆裂性骨折椎管狭窄程度。     

上腰椎爆裂型骨折外侧入路的手术方法

目的: 介绍上腰椎爆裂型骨折外侧入路的手术方法。方法: 沿骶棘肌外缘切口, 分离暴露L1、2、3横突, 切除横突、椎弓根、椎体后缘和突出的椎间盘, 减压硬膜管, 并同时作椎体间植骨骨水泥固定。结果: 50例患者均能达到脊髓前减压彻底和椎体间植骨融合稳定的目的。截瘫和下肢神经症状的恢复根据Frankel标准, 一般均能恢复 1~2个档次。结论: 上腰椎爆裂型骨折外侧入路的手术方法, 能达到脊髓前减压彻底和椎体间植骨融合稳定的目的。     

Movement-related phasic muscle activation

To test the hypothesis that phasic muscle activation is related to the acceleration-deceleration characteristics of the resulting movement, we examined the relation between the duration of the acceleratory phase of a variety of movement types and the duration of the phasic muscle activity producing the acceleration (the initial agonist burst, AG1). Movements of five types were studied: (1) step-tracking movements of different amplitudes (10–90 deg) and durations (200–800 ms), (2) movements of the same amplitude (40 deg) and duration (600 ms) varying only in their symmetry ratio (SR, ratio of acceleration to deceleration durations), (3) movements in which acceleration duration was changed while acceleration magnitude was held constant, (4) oscillatory movements of different frequencies and peak amplitudes, (5) step-tracking movements against different inertial loads. Subjects made movements about the elbow joint in the horizontal plane. Surface electromyographic (EMG) activity was recorded from the biceps and the lateral head of the triceps muscles. Under all movement conditions tested and with acceleration duration ranging from 100 to 500 ms, acceleration duration varied linearly with the duration of AG1. Correlation coefficients for the linear regression lines ranged from 0.8 to 0.99. The slope of the best fit linear regression lines ranged from 0.5 to 1.6 and tended to be higher for extensions than flexions. The variations in slope may arise from differing mechanical properties of the biceps and triceps muscles, as well as from active forces produced in the antagonist. AG1 duration was unchanged by inertial loading when subjects kept acceleration duration constant. If subjects responded to an increase in inertial load with an increase in acceleration duration, there was a corresponding increase in AG1 duration. The data demonstrate a general relation between one characteristic of muscle activation (AG1 duration) and the resulting movement. The linear form of the relation is invariant across movement amplitude (range 10–90 deg), speed, duration (range 200–800 ms) and temporal profile (SR range 0.3-2.7), and is also independent of movement type (step, oscillatory). Such a general and simple relation between EMG and movement suggests that, at least to a first approximation, the nervous system can rather simply determine the muscle activation patterns needed to produce movements with desired characteristics.     

Centaur/Plate System内固定治疗胸腰椎爆裂型骨折并截瘫

目的:探讨经前路减压,应用The Centaur/Plate System内固定治疗胸腰椎爆裂型骨折并截瘫的临床效果。方法:术前常见CT扫描,经胸膜外-腹膜后入路,对5例胸腰椎爆裂型骨折并截瘫患者进行前路彻底减压,取髂骨或/和肋骨行椎间植骨,应用The Centaur/Plate System进行复位、内固定术。结果:5例均获得8～10个月的随访,平均9个月,椎间植骨全部完全融合。融合时间为3～5个月,平均4个月。除1例患者Frankel分级达2级以上改善外,其余患者均获得行走功能,Frankel分级达E级。椎管狭窄面积术前平均为68.9％,术后椎管无狭窄。术前后凸成角15°～30°,平均20°,术后为0～6°。随访期间,无异常发现。结论:经前路减压直接彻底,为脊髓神经功能的恢复提供了最佳环境。The Centaur/Plate System为脊柱前路内固定系统。设计科学、合理,固定良好,能恢复脊柱的生理弯曲。工具使用简便,可靠。内固定材料为钛合金。生物相容性好,是治疗胸腰椎爆裂型骨折并截瘫的一种疗效可靠的方式。     

Effects of dizocilpine (MK-801) on rat midbrain dopamine cell activity: differential actions on firing pattern related to anatomical localization

Summary The effects of the non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist dizocilpine ((+)-MK-801) on the firing pattern of midbrain dopamine neurons were studied with single cell recording techniques in male albino rats anaesthetized with chloral hydrate. The extracellularly recorded electrical activity of single, identified dopamine neurons was studied with respect to firing rate, burst firing and regularity of firing. MK-801 (0.01–1.0 mg/kg IV) induced different effects in different subgroups of midbrain dopamine neurons. In the substantia nigra, firing rate was increased while the pattern was regularized and burst firing slightly increased. In the ventral tegmental area, firing rate and regularity of firing was also increased while effects on burst firing were bidirectional. Histological inspections revealed that neurons which responded with an increase in burst firing were mainly located in the nucleus paranigralis subdivision of the ventral tegmental area, while cells responding with a decrease were predominantly found in the nucleus parabrachialis pigmentosus subdivision. The effects of MK-801 were similar to previously described effects of phencyclidine, another non-competitive NMDA antagonist. The present effects of MK-801 might shed some light on the mechanisms involved in psychotic symptoms induced by phencyclidine and other non-competitive NMDA antagonists.     

Burst activity of identified tecto-reticulo-spinal neurons in the alert cat

Summary Activity of tecto-reticulo-spinal neurons (TRSN), identified electrophysiologically and/or by intra-axonal HRP injections, was studied in alert cats during presentation of moving visual stimuli. A majority of TRSNs showed complex visuomotor properties: directionally selective visual responses in the absence of motor counterparts of orienting, enhanced bursting when stimuli triggered saccades, and no activation for spontaneous saccades. Highest intraburst frequencies were observed during active orienting towards novel, interesting objects. The more vigorous bursts usually contained repetitive grouped discharges attaining instantaneous frequencies up to 700 imp/s but average firing rates remained in the range of 120–300 imp/s. Intra-axonal HRP injections confirmed terminations of TRSN collaterals in the premotor areas of the lower brain stem, including the abducens nucleus, but also disclosed differences in the details of collateralization between neurons showing different types of visuo-motor activity.     

Use of DRL in differentiating anxiolytic and neuroleptic properties of CNS drugs.

Presented in this paper are the effects of chlorpromazine, clozapine, d-amphetamine and diazepam on DRL behavior in rats. D-Amphetamine and diazepam, which showed similar effects on response errors, could be identified on the basis of burst responding and drug interaction. Clozapine, a new antipsychotic agent which does not cause extrapyramidal side effect in man affected DRL behavior in the same way as did chlorpromazine. Thus, DRL schedules are probably not useful in differentiating various neuroleptic agents.