Vasomotion has chloride-dependency in rat mesenteric small arteries

The possibility that Ca²⁺-activated Cl⁻ conductances (CaCCs) contribute to oscillations in vascular tone (vasomotion) is tested in isolated mesenteric small arteries from rats where cGMP independent (I _Cl(Ca)) and cGMP-dependent (I _Cl(Ca,cGMP)) chloride conductances are important. The effect of anion substitution and Cl⁻ channel blockers on noradrenaline (NA)-stimulated tension in isometrically mounted mesenteric arteries and for chloride conductance of smooth muscle cells isolated from these arteries were assessed electrophysiologically. Cl⁻ _o replacement with aspartate blocked vasomotion while 36mM SCN⁻ _o (substituted for Cl⁻) was sufficient to inhibit vasomotion. Oscillations in tone, membrane potential, and [Ca²⁺]_i disappeared with 36mM SCN⁻. DIDS and Zn²⁺ blocked I _Cl(Ca,cGMP) but not I _Cl(Ca). Vasomotion was not sensitive to DIDS and Zn²⁺, and DIDS and Zn²⁺ induce vasomotion in arteries without endothelium. The vasomotion in the presence of DIDS and Zn²⁺ was sensitive to 36mM SCN⁻ _o. The anion substitution data indicate that Cl⁻ is crucial for the V _m and [Ca²⁺]_i oscillations underlying vasomotion. The Cl⁻ channel blocker data are consistent with both CaCCs being important.     

Mathematical model of renal regulation of urea excretion

A mathematical model of transport processes in the ascending limbs (a.l.), collecting ducts (c.d.), and surrounding interstitium-capillary plexus (i.c.p.) of the renal medulla has been developed and applied to an investigation of mechanisms which may be involved in renal tubular regulation of urea excretion. Solute and water balance equations for perfectly-mixed compartments in series describe the transport processes in the a.l., c.d., and i.c.p. Solute species considered are urea, salt (NaCl), and an idealised ‘nonreabsorbable solute’ which accounts for miscellaneous substances accumulated in the c.d. The membrane transport equations used in the model describe solute movement by passive diffusion, solvent drag, and active transport; and water movement by osmosis. Model parameters are evaluated from published experimental data. Digital computer solutions of the model equations indicate that virtually all experimental observations pertaining to the regulation of urea excretion can be explained by an increase in the solvent drag of urea from the cortical and medullary c.d. Therefore, the need to postulate an active transport of urea from the c.d. to explain the regulation of urea excretion is obviated.     

用自适应血管边缘检测方法自动跟踪测量血管自律运动

为实现以视频速度实时测量，建立一条与血管轴向垂直且在血管径向覆盖血管边缘的测量线作为采样窗口。通过对该测量线光密度分布的分析得到一个可逐帧自适应光密度变化的动态阈值，根据血管边缘区域内光密度曲线的形态特征和管径动态变化的可能范围来判定微血管边缘。建立多项判定规则提高边缘测定的精度并跳过非边缘区以加快处理速度。为进一步提高这种边缘测定的可靠性，在原图像上叠加一个与被测血管边缘位置相一致的动态图形指示。实用结果发现：即使在微血管图像背景复杂和反差较弱的情况下，这种采用自适应阈值和多项判别规则的微血管边缘动态检测方法仍能完成对微血管自律运动的自动跟踪测量     

Vasomotion in the rat cerebral microcirculation recorded by laser-Doppler flowmetry

In the present study, changes in frequency and amplitude of the rhythmic variations (vasomotion) in blood flow in the intact cerebral circulation of the rat were investigated using laser-Doppler flowmetry (LDF) during stepwise decrease in mean arterial blood pressure (MABP) and hyper-and hypocapnia. Experiments were performed on 12 adult Sprague-Dawley rats of either sex, anaesthetized with α-chloralose. The rat's head was fixed on a stereotaxic frame and a small hole was made in the parietal bone but the dura and a thin inner bone layer were kept intact. The microvascular blood flow of the parietal cortex on the right or on both sides was continuously recorded by the laser-Doppler flowmeter (Periflux PF2B, Perimed, Stockholm, Sweden). The cerebral circulation of the rat exhibited vasomotion in control conditions with a frequency of 8–10 cycles per minute (cpm) and an amplitude of 5–10% of the cerebral blood flow (CBF). No significant changes in CBF could be detected when the MABP was above 60 mmHg, but it decreased significantly when MABP was reduced below 50 mmHg. However, during stepwise pressure reduction the vasomotion frequency decreased progressively while its amplitude showed a reversed U-shaped curve with a peak at 60–80 mmHg. During hypercapnia, the rhythmical oscillations showed a decrease in both frequency and amplitude, whereas during hypocapnia their frequency did not change but their amplitude increased. These results support the hypothesis that the vasomotion frequency might be dependent of the wall tension and cellular pH while its amplitude could be related to decreased tissue oxygenation.     

A test of the focusing hypothesis for category judgment: an explanation using the mental-box model

This paper presents a new model of category judgment. The model hypothesizes that, when more attention is focused on a category, the psychological range of the category gets narrower (category-focusing hypothesis). We explain this hypothesis by using the metaphor of a "mental-box" model: the more attention that is focused on a mental box (i.e., a category set), the smaller the size of the box becomes (i.e., a cardinal number of the category set). The hypothesis was tested in an experiment (N = 40), where the focus of attention on prescribed verbal categories was manipulated. The obtained data gave support to the hypothesis: category-focusing effects were found in three experimental tasks (regarding the category of "food", "height", and "income"). The validity of the hypothesis was discussed based on the results.     

川芎嗪对家兔肠系膜细动脉血管血管运动的抑制作用

在全身动脉血压控制下应用显微录像静画步进和二点光电法同步测定了川芎嗪对话体家兔肠系膜细动脉的内径、血流速度和血管运动的影响及其相互间的关系。结果发现川芎嗪有浓度依赖性的降压作用。给药后３０ｓ血压开始下降并持续１ｍｉｎ。８ｍｇ／ｋｇ比４ｍｇ／ｋｇ给药组降压作用大，２ｍｇ／ｋｇ组效果不明显。伴随血压下降８ｍｇ／ｋｇ给药组细动脉血流速度减慢，但内径无变化，４ｍｇ／ｋｇ和２ｍｇ／ｋｇ组效果不明显。又在活体显微镜下在３０～５０μｍ细动脉水平直接证明了川芎嗪有抑制局部投予去甲肾上腺素引起的血管运动的作用。并发现１６ｍｇ／ｋｇ比８ｍｇ／ｋｇ给药组抑制作用时间长。即使全身血压不变，细动脉血流也随血管运动周期变化，细动脉舒张血流量增加。将给去甲肾上腺素前与给川芎嗪后的内径对比变化不明显。提示ＴＭＰ的作用本质是抑制去甲肾上腺素引起的血管运动而不是扩张血管。     

Vasomotion in the rat cerebral microcirculation recorded by laser-Doppler flowmetry.

In the present study, changes in frequency and amplitude of the rhythmic variations (vasomotion) in blood flow in the intact cerebral circulation of the rat were investigated using laser-Doppler flowmetry (LDF) during stepwise decrease in mean arterial blood pressure (MABP) and hyper- and hypocapnia. Experiments were performed on 12 adult Sprague-Dawley rats of either sex, anesthetized with alpha-chloralose. The rat's head was fixed on a stereotaxic frame and a small hole was made in the parietal bone but the dura and a thin inner bone layer were kept intact. The microvascular blood flow of the parietal cortex on the right or on both sides was continuously recorded by the laser-Doppler flowmeter (Periflux PF2B, Perimed, Stockholm, Sweden). The cerebral circulation of the rat exhibited vasomotion in control conditions with a frequency of 8-10 cycles per minute (cpm) and an amplitude of 5-10% of the cerebral blood flow (CBF). No significant changes in CBF could be detected when the MABP was above 60 mmHg, but it decreased significantly when MABP was reduced below 50 mmHg. However, during stepwise pressure reduction the vasomotion frequency decreased progressively while its amplitude showed a reversed U-shaped curve with a peak at 60-80 mmHg. During hypercapnia, the rhythmical oscillations showed a decrease in both frequency and amplitude, whereas during hypocapnia their frequency did not change but their amplitude increased. These results support the hypothesis that the vasomotion frequency might be dependent of the wall tension and cellular pH while its amplitude could be related to decreased tissue oxygenation.     

A physiologic explanation for distal nerve slowing

Numerous studies have shown that peripheral nerves conduct slower distally than proximally. This slowing is gradual at first, and more pronounced approaching the distal end of the nerve. At first glance, distal slowing appears not to make physiologic sense, as it slows reaction time and coordination compared with a hypothetical nerve that does not slow distally. However, distal slowing decreases energy consumption, crucial in a high energy system. A previous study had shown that exponential slowing correlated well with experimental data, and resulted in significant energy savings. In this study, a series of equations was created to determine the degree of slowing to minimize both conduction time and velocity. The solution, Latency L = kd(.785) where k is a constant and d is the distance from the distal end of the nerve, correlates extremely closely with experimental data. This equation can be easily used to accurately predict normal latencies at different points along a nerve, and to detect subtle distal nerve pathology.     

Genetic variation in the urea cycle: a model resource for investigating key candidate genes for common diseases

The urea cycle is the primary means of nitrogen metabolism in humans and other ureotelic organisms. There are five key enzymes in the urea cycle: carbamoyl-phosphate synthetase 1 (CPS1), ornithine transcarbamylase (OTC), argininosuccinate synthetase (ASS1), argininosuccinate lyase (ASL), and arginase 1 (ARG1). Additionally, a sixth enzyme, N-acetylglutamate synthase (NAGS), is critical for urea cycle function, providing CPS1 with its necessary cofactor. Deficiencies in any of these enzymes result in elevated blood ammonia concentrations, which can have detrimental effects, including central nervous system dysfunction, brain damage, coma, and death. Functional variants, which confer susceptibility for disease or dysfunction, have been described for enzymes within the cycle; however, a comprehensive screen of all the urea cycle enzymes has not been performed. We examined the exons and intron/exon boundaries of the five key urea cycle enzymes, NAGS, and two solute carrier transporter genes (SLC25A13 and SLC25A15) for sequence alterations using single-stranded conformational polymorphism (SSCP) analysis and high-resolution melt profiling. SSCP was performed on a set of DNA from 47 unrelated North American individuals with a mixture of ethnic backgrounds. High-resolution melt profiling was performed on a nonoverlapping DNA set of either 47 or 100 unrelated individuals with a mixture of backgrounds. We identified 33 unarchived polymorphisms in this screen that potentially play a role in the variation observed in urea cycle function. Screening all the genes in the pathway provides a catalog of variants that can be used in investigating candidate diseases.     

自发性高血压大鼠肾脏和胰腺微循环血流灌注和自律运动变化

目的:观察自发性高血压大鼠(SHRs)肾脏和胰腺微循环血流灌注和自律运动变化。方法:市购8周龄SHRs(SHR组)和正常血压对照大鼠(WKY组)各6只,手术暴露肾脏和胰腺。采用双通道激光多普勒血流仪,多点观测其表面的微血流灌注和自律运动水平,并通过仪器自带分析软件的小波变换功能将微血流信号转换为二维频谱图和三维时频图像,比较两组大鼠肾脏、胰腺血流灌注水平、血流速度和血细胞浓度的变化特征及微血流灌注频谱中一氧化氮(NO)依赖与否的内皮细胞源频段幅值差异。结果:与WKY组相比,SHR组肾脏、胰腺微血流灌注水平均显著降低(P<0.05或P<0.01);同时呈现胰腺微血管自律运动节律紊乱。SHR组肾脏和胰腺微血管自律运动振幅和频率均显著降低(P<0.05或P<0.01)。SHR组肾脏和胰腺微血流灌注频谱中NO依赖与否的内皮细胞源频段振幅均显著低于WKY组(P<0.05或P<0.01)。结论:SHRs肾脏、胰腺微循环功能异常,表现为微血流灌注水平下降,微血管自律运动功能障碍。     

自发性高血压幼鼠淋巴微循环自律运动特征

目的:观察幼龄自发性高血压大鼠(SHR)发病早期淋巴微循环的自律运动特征。方法:手术暴露3周龄雄性SHR(SHR组,n=11)和Wistar大鼠(Wistar组,n=11)肠系膜集合淋巴管,采用活体显微录像设备连续视频录像,使用Vastrack自律运动跟踪技术对视频录像进行动态测量分析,比较两组大鼠肠系膜集合淋巴管自律运动收缩频率、相对振幅、收缩时长、舒缩时长、收缩振幅、舒张振幅、收缩速度、舒张速度、收缩/舒张时长比、收缩分数和收缩活力指数的差异。结果:SHR组大鼠淋巴微循环自律运动的相对振幅、收缩振幅、舒张振幅、收缩时长、舒张时长、收缩速度、舒张速度和收缩分数较Wistar组大鼠轻度降低,收缩频率、收缩/舒张时长比和收缩活力指数较Wistar组大鼠小幅上升,但差异均无统计学意义(P0.05)。结论:自发性高血压早期幼鼠集合淋巴管自律运动特征未见显著改变,提示其淋巴微循环尚未发生明显功能紊乱。     

麻醉对比格犬胃腧穴区真皮层微血管舒缩活动的影响

目的:观察丙泊酚-异氟烷静脉注射-吸入复合麻醉(静吸复合麻醉)和速眠新Ⅱ肌肉注射麻醉(肌注麻醉)对比格犬胃腧穴区真皮层微血管舒缩活动的影响。方法:6-12月龄比格犬10只,分为静吸复合麻醉组和肌注麻醉组,每组5只,以胃腧穴为监测穴位,分别于麻醉前和麻醉后用激光多普勒血流仪测定两组比格犬真皮微血管舒缩活动波形图,计算、分析麻醉前后其频率和振幅的变化。结果:麻醉前,静吸复合麻醉组和肌注麻醉组比格犬胃腧穴区真皮微血管舒缩振幅分别为28.53±1.35和28.39±2.50PU,频率分别为11.69±0.64和11.91±0.63次/min;麻醉后,静吸复合麻醉组振幅为30.90±3.12PU,频率为26.68±0.46次/min;肌注麻醉组振幅为30.30±2.21PU,频率为18.65±1.25次/min。麻醉后,两组比格犬胃腧穴区真皮微血管舒缩振幅与麻醉前比较,以及麻醉后两组间比较,差异均无统计学意义(P0.05);两组频率与麻醉前比较,差异均有统计学意义(P0.01),两组麻醉后频率差异亦有统计学意义(P0.01)。结论:丙泊酚-异氟烷静脉注射-雾化吸入复合麻醉和速眠新Ⅱ肌注麻醉均能显著提高比格犬胃腧穴区微血管舒缩频率,且前者作用强于后者。     

Hippocampal stimulation rebound effects in hamsters

Bar-pressing for solid food on a variable interval schedule was severely disrupted during and following electrical stimulation of the dorsolateral hippocampus in female hamsters, the disruption of bar-pressing for liquid food was substantially less. With experimenter delivered stimulation rebound eating of solid food and grooming were found to increase while time spent drinking liquid food did not. Other observations indicated that neither drinking water nor manipulating nest materials increased during or after hippocampal stimulation. Self-stimulation behavior was supported by dorsolateral hippocampal stimulation.