Cycle number and waveform of fluid flow affect bovine articular chondrocytes

Many studies have shown that a loading-induced (bio)physical signal regulates chondrocyte behavior. In a recent study our group has demonstrated the shear stress level- and frequency-dependent effect of sinusoidal oscillatory fluid flow on bovine articular chondrocyte (BAC) cytosolic calcium concentration ([Ca(2+)](i)), neglecting the fact that chondrocytes are not likely to see these ideal waveform in vivo or in vitro. Furthermore, possible overload of articular cartilage or excessive shear stress in chondrocyte cultures are more likely to be of a short nature. Therefore, in this study we choose to investigate a saw-tooth waveform oscillating fluid flow at varying exposure times in comparison to the established sinusoidal oscillatory waveform. [Ca(2+)](i), as an early signaling molecule, was quantified using the fluorescent dye fura-2. BAC were exposed to 1 Hz sinusoidal or saw-tooth waveform oscillating fluid flow at 2.2 Pa flow rates in a parallel plate flow chamber for 8 different loading times. As little as 5 cycles of oscillatory fluid flow were sufficient to increase [Ca(2+)](i) significantly over baseline. The number of responding cells could not be increased any further after a sufficient number of cycles (11), regardless of the waveform. Furthermore, a saw-tooth waveform appeared to be more stimulatory than regular sinusoidal oscillating flow at higher cycle numbers. BAC appear to be able to respond to these biophysical stimuli in a differentiated manner. This ability might give every single chondrocyte the capability to maintain its territory autonomously, since chondrocytes distributed in articular cartilage without the possibility to interact, e.g., via cell processes.     

Natural Environmental Cues and Orcadian Rhythms of Behaviour—A Perspective

Natural environmental cycles are often extremely difficult to reproduce under laboratory conditions. Laboratory light-dark cycles differ from natural light-dark cycles in terms of intensity and spectral distribution, whilst simulated temperature cycles may differ from natural temperature cycles in waveform. The expression of a free-running rhythm depends upon the ‘level’ of constant conditions provided. Environmental cues affect the period, phasing, amplitude and activity-rest ratios of circadian rhythms and, if inappropriate, may result in aberrant behaviour patterns which are unlike those observed in nature.     

Natural Environmental Cues and Orcadian Rhythms of Behaviour—A Perspective

Natural environmental cycles are often extremely difficult to reproduce under laboratory conditions. Laboratory light-dark cycles differ from natural light-dark cycles in terms of intensity and spectral distribution, whilst simulated temperature cycles may differ from natural temperature cycles in waveform. The expression of a free-running rhythm depends upon the 'level' of constant conditions provided. Environmental cues affect the period, phasing, amplitude and activity-rest ratios of circadian rhythms and, if inappropriate, may result in aberrant behaviour patterns which are unlike those observed in nature.     

Mechanical stimulation induces pp125(FAK) and pp60(src) activity in an in vivo model of trabecular bone formation.

Utilizing an in vivo model of trabecular bone formation, we demonstrated the temporal and spatial activation of pp125(FAK) in response to specific mechanical load stimuli. Bone chambers equipped with hydraulic actuators were aseptically inserted into each proximal tibial metaphysis of adult, male dogs under general anesthesia. The load stimulus consisted of a trapezoidal waveform, with a maximum compressive load of 17.8 N, loading rate of 89 N/s, at 1 Hz frequency. One chamber was loaded for 2 (120 cycles), 15 (900 cycles), or 30 min (1,800 cycles), whereas the contralateral chamber served as unloaded control. Bone chambers were biopsied at postload time points of 0, 15, and 45 min. Load-induced activation of FAK was rapid, and the duration of activation was dependent on the number of applied load cycles. Mechanical stimulation increased the association of FAK with Src and the time course of complex formation paralleled the temporal activation of FAK. Evaluation of cryosections revealed prominent FAK immunoreactivity among marrow fibroblasts and stromal cells.     

Chronic clorgyline treatment of Syrian hamsters: an analysis of effects on the circadian pacemaker

Clorgyline, a type A monoamine oxidase inhibitor with antidepressant properties when administered to depressed patients, is often associated with disturbances of the human sleep-wake cycle. In order to assess its effects on the mammalian circadian system, this drug was administered chronically to Syrian hamsters. It was found to affect the hamster circadian system in four specific ways. Clorgyline increased the intrinsic period of wheel-running activity, altered the phase response curve to brief light pulses, altered the reduced waveform of running activity in animals maintained in light-dark cycles or constant darkness, and increased the activity-rest ratio in animals maintained in constant darkness. Our data support the interpretation that clorgyline exhibits direct or indirect input to the circadian pacemaker and alters the processing of photic information to the pacemaker.     

心衰患者动脉血气波浪式变化及其幅度降低的初步实验证据*

目的: 心力衰竭患者呼吸调控异常的机制众说纷纭,特别是动脉血气周期性波浪式变化信号的改变及其与心功能的关系尚缺乏直接的试验证据。本文依据心力衰竭患者动脉血气周期性波浪式变化信号的降低幅度,探讨心力衰竭导致呼吸调控异常的机制。方法: 选择5名心力衰竭患者,连续桡动脉逐搏取血,测定PaO₂,PaCO₂,pHa和SaO₂。选取2个典型呼吸周期,用于分析动脉血气的波浪式变化。比较患者相邻最高和最低值,以验证是否存在周期性波浪式信号变化。此外,将心力衰竭患者与心功能正常患者动脉血气周期性波浪式信号的变化幅度进行统计学t检验分析,比较有无差异。结果: 心力衰竭患者包括2例外科手术和3例ICU住院监护患者,4男1女,年龄(69±7)岁,身高(169±10)cm,体质量(75±19)kg,左心射血分数(LVEF)=(38±3)%。动脉血液充满肝素化细长塑化管需要17±2次心跳,即取血需要17±2次心跳,覆盖超过2个呼吸周期。心力衰竭患者PaO₂,PaCO₂,[H⁺]a和SaO₂均呈现明显的波浪式变化(P<0.05),幅度分别是(7.94±2.02)mmHg,(1.18±0.56)mmHg,(0.54±0.17)nmol/L和(0.21±0.07)%,分别是各自均值的(6.1±1.5)%,(3.2±1.5)%,(1.5±0.5)%和(0.2±0.1)%。与心功能正常患者比较,动脉血气波浪式变化幅度呈现明显降低趋势,但仅PaO₂和[H⁺]a有明显统计学差异(P<0.05)。结论: 采用连续逐搏动脉取血血气分析法证实,心力衰竭患者自主呼吸时动脉血气也有周期性波浪式变化信号,但其变化幅度较心功能正常患者明显降低。     

基于MIMIC数据库的多参数数据D/A回放系统

文中分析了MIMIC多参数智能监护数据库存储文件的识读方法,该数据库公开发表于PhysioNET,还研究及基于STM32和DAC8568的多参数数据D/A回放系统,包括系统硬件工作原理和系统软件工作原理。MIMIC多参数智能监护数据库的数据文件对于变异性较大的生理参数采用连续采样的方式,而对于相对稳定的生理参数采用周期采样的方式,因此,多参数数据各信号的抽样频率不同。系统首先通过VC++编程读取一个多抽样频率数据并在PC机上显示其波形,然后经过D/A硬件设备进行D/A转换后使用示波器输出其波形,实现输出的波形与原始的波形能同时回放。系统可作为模拟信号源,为远程多参数生理监护仪的研制奠定了基础。     

人体动脉血气信号波浪式变化及连续动脉逐搏取血血气分析方法的建立*

目的: 建立动脉逐搏取血血气分析法,在人体实验中验证呼吸调控核心信号——PaO₂,PaCO₂和[H⁺]a是受呼吸影响的周期性、波浪式变化信号,而不是传统理念上误认的稳定水平信号。方法: 选择心功能正常、Allen试验阴性需要监测动脉血流动力学变化的患者6例。在左侧桡动脉穿刺,连接肝素化塑化管（3 mm×1 000 mm）,注满血液并计数血液注满所需心跳次数。用止血钳将塑化管钳闭成与心跳次数相对应的分段后,迅速置于冰水中,立即进行血气分析。选取每位患者的2个典型波浪式周期,用于分析2对最高-最低和最低-最高共4个测定值,取平均值。对相邻最高和最低值作统计学配对t检验。结果: 血液注满塑化管需要16±2次心跳,均覆盖超过2个呼吸周期。每个呼吸周期是5±0.6次心跳。PaO₂、PaCO₂、[H⁺]a和SaO₂都呈现出明显的波浪式变化（相邻高点与低点比较,P<0.05）,PaO₂、PaCO₂、[H⁺]a和SaO₂的波浪幅度分别是（11.28±1.13）mmHg,（1.77±0.89）mmHg,（1.14±0.35）nmol/L和（0.52±0.44）%;波浪幅度分别是其平均值的（7.7±1.1）%,（5.1±2.5）%,（3.1±1.0）%和（0.5±0.4）%。结论: 动脉延长管连续取血,按心跳次数分隔血样,血气分析法简单易行,为验证动脉血气受呼吸影响的周期性波浪式信号提供了可靠证据。本方法为原创,技术操作层面仍需提高熟练程度,增加志愿者和试验样本的数量进一步探索此类信号的临床检测可靠性及其与临床疾病的关系。     

Topological remodeling of cultured endothelial cells by characterized cyclic strains

Evaluation of mechanical environment on cellular function is a major field of study in cellular engineering. Endothelial cells lining the entire vascular lumen are subjected to pulsatile blood pressure and flow. Mechanical stresses caused by such forces determine function of arteries and their remodeling. Critical values of mechanical stresses contribute to endothelial damage, plaque formation and atherosclerosis. A device to impose cyclic strain on cultured cells inside an incubator was designed and manufactured operating with different load amplitudes, frequencies, numbers of cycles and ratios of extension to relaxation. Endothelial cells cultured on collagen coated silicon scaffolds were subjected to cyclic loading. Effects of mechanical loading on cell morphology were quantified using image processing methods. Results showed change in cell orientation from a randomly oriented before the test up to 80 degrees alignment from load axis after loading. Endothelial cells were elongated with shape index reductions up to 47% after cyclic stretch. By increase of strain amplitude, loading frequency and number of cycles, significant decrease in shape index and significant increase in orientation angle were observed. Change of load waveform similar to arterial pulse pressure waveform resulted in alteration of cell alignment with 9.7% decrease in shape index, and 10.8% increase in orientation angle. Results of cyclic loading tests in a disturbed environment with elevated PH showed lack of remodeling. It was concluded that tensile loading of endothelial cells influences cell morphology and alignment, a mechanism for structural regulation, functional adaptation and remodeling. Disturbed environment results in endothelial dysfunction and injury.     

Multi-component based cross correlation beat detection in electrocardiogram analysis

Background  

The first stage in computerised processing of the electrocardiogram is beat detection. This involves identifying all cardiac cycles and locating the position of the beginning and end of each of the identifiable waveform components. The accuracy at which beat detection is performed has significant impact on the overall classification performance, hence efforts are still being made to improve this process.     

Method for predicting an EEG waveform as an aid to the accurate recording of evoked potentials

Evoked potentials are the brain's responses to incoming stimuli and are usually recorded under noisy circumstances. To improve the signal-to-noise ratio, signal averaging has been widely applied to the recorded data, but an improved method is required. A method of EEG waveform prediction for the accurate recording of evoked potentials is proposed, and an electroencephalographic waveform predicted by using an EEG model and a nonlinear exponentially weighted least squares method, subtracting the predicted EEG waveform from the raw data and extracting the evoked waveform. By the use of this method, we have successfully predicted the EEG waveform and detected the evoked potential with only a small number of averages.     

Segmentation of cardiac sound signals by removing murmurs using constrained tunable-Q wavelet transform

The automatic segmentation of cardiac sound signals into heart beat cycles is generally required for the diagnosis of heart valve disorders. In this paper, a new method for segmentation of the cardiac sound signals using tunable-Q wavelet transform (TQWT) has been presented. The murmurs from cardiac sound signals are removed by suitably constraining TQWT based decomposition and reconstruction. The Q-factor, redundancy parameter and number of stages of decomposition of the TQWT are adapted to the desired statistical properties of the murmur-free reconstructed cardiac sound signals. The envelope based on cardiac sound characteristic waveform (CSCW) is extracted after the removal of low energy components from the reconstructed cardiac sound signals. Then the heart beat cycles are derived from the original cardiac sound signals by mapping the required timing information of CSCW which is obtained using established methods. The experimental results are included in order to show the effectiveness of the proposed method for segmentation of cardiac sound signals in comparison with other existing methods for various clinical cases.     

Method for single-trial recordings of somatosensory evoked potentials

Evoked potentials (EPs) in response to stimuli are recorded from a human scalp contaminated with noise. To improve the signal-to-noise ratio, averaging methods have been widely used for the recorded data. However, when the waveforms of EP for each stimulus are not identical, the average waveform of the EP deteriorates. Variation of the EP waveform to each stimulus itself is important information for the EP. In this paper, a recording method for single somatosensory evoked potential (SEP) waveform is proposed, in which three kinds of band-pass filters were selectively used during three specific time sectors for each interstimulus interval. For the late section of the interval, an EEG waveform prediction method was applied to eliminate contaminated alpha rhythm components. By using the proposed method, we were successful in detecting the single SEP waveform.     

Photoperiodic modulation of circadian rhythms in the cricket Gryllus bimaculatus

The waveform and the free-running period of circadian rhythms in constant conditions are often modulated by preceding lighting conditions. We have examined the modulatory effect of variable length of light phase of a 24h light cycle on the ratio of activity (alpha) and rest phase (rho) as well as on the free-running period of the locomotor rhythm in the cricket Gryllus bimaculatus. When experienced the longer light phases, the alpha/rho-ratio was smaller and the free-running period was shorter. The magnitude of changes in alpha/rho-ratio was dependent on the number of cycles exposed, while the free-running period was changed by a single exposure, suggesting that there are separate regulatory mechanisms for the waveform and the free-running period. The neuronal activity of the optic lobe showed the alpha/rho-ratio changing with the preceding photoperiod. When different photoperiodic conditions were given to each of the two optic lobe pacemakers, the alpha/rho-ratio of a single pacemaker was rather intermediate between those of animals treated with either of the two conditions. These results suggest that the storage of the photoperiodic information occurs at least in part in the optic lobe pacemaker, and that the mutual interaction between the bilateral optic lobe pacemakers is involved in the photoperiodic modulation.     

Oscillatory enzyme reactions and Michaelis–Menten kinetics

Oscillations occur in a number of enzymatic systems as a result of feedback regulation. How Michaelis–Menten kinetics influences oscillatory behavior in enzyme systems is investigated in models for oscillations in the activity of phosphofructokinase (PFK) in glycolysis and of cyclin-dependent kinases in the cell cycle. The model for the PFK reaction is based on a product-activated allosteric enzyme reaction coupled to enzymatic degradation of the reaction product. The Michaelian nature of the product decay term markedly influences the period, amplitude and waveform of the oscillations. Likewise, a model for oscillations of Cdc2 kinase in embryonic cell cycles based on Michaelis–Menten phosphorylation–dephosphorylation kinetics shows that the occurrence and amplitude of the oscillations strongly depend on the ultrasensitivity of the enzymatic cascade that controls the activity of the cyclin-dependent kinase.     

Particle deposition in arteries ex vivo: effects of pressure,flow, and waveform

The goal of this study was to quantify the effect of hemodynamic pressure, flow and waveform perturbations on the deposition of protein-sized particles in porcine carotid arteries ex vivo. An ex vivo perfusion system was used to control the pressure and flow environment for excised arterial tissue. Confocal laser microscopy images revealed that 200 nm particles were deposited intimally and that more spheres were evident along vessels perfused under oscillatory waveform conditions than all others. Under all pressure, flow and waveform conditions, particles were excluded from the media and adventitia of the vessel wall. The steady flow data support the use of Darcy's Law with pressure-dependent hydraulic permeability to model arterial tissue.     

人体动脉血气波浪式变化特点的实验证据—同时间动、静脉血波浪式变化幅度的不同*

目的: 人动脉血来源是右心系统并在肺脏进行气体交换的静脉血,右心系统的静脉血是否存在波浪式信号目前尚没有证据支持,本研究旨在对比同时间动、静脉血中信号的连续变化特点。方法: 选择心功能正常,需要连续监测动脉血流动力学变化的患者6 例,4男2女,年龄（59.00±16.64） 岁,体质量（71.67±10.37）kg,左心射血分数（LVEF）（61.33±2.16)%。患者签署知情同意书后,选择心功能正常需要监测动、静脉血流动力学变化的患者6 例,连续同时桡动脉、颈内静脉逐搏取血,测定PaO₂。选取2个典型呼吸周期,用于分析同时段动、静脉血气的波浪式变化。分别比较患者血氧分压最高和最低值,以验证同时段动、静脉血气是否都存在周期性波浪式信号变化。此外,将患者动脉、静脉血气周期性波浪式信号的变化幅度进行统计学t 检验分析,比较有无差异。结果: 共6例患者,抽取动、静脉血液充满肝素化细长塑化管需要15~16次心跳,即取血需要15~16次心跳,全部覆盖超过2个呼吸周期。所有患者动脉血气中PaO₂均呈现明显的波浪式变化（P<0.05）,幅度是（9.96±5.18）mmHg,是均值的（8.09±2.43）%。患者静脉血气中PaO₂波动幅度并不明显,为（1.63±0.41）mmHg,是均值的（3.91±1.22）%,与动脉血气组相比有明显统计学差异（P<0.05）。结论: 采用同时连续逐搏动、静脉取血血气分析法证实,患者自主呼吸时动脉血气有明显的周期性波浪式变化信号,而静脉血气几乎没有周期性波浪式变化信号（很弱）,说明动脉血气波浪式信号主要是由于肺通气过程中吸气和呼气期产生肺泡中氧分压规律性上升和下降,通过离开肺毛细血管与肺泡氧气压力平衡的动脉化血液,经过左心室搏血进入动脉血管系统所致。     

Temperature sensitivity of the electric organ discharge waveform in Gymnotus carapo

At the southern boundary of gymnotiform distribution in America. water temperature changes seasonally, and may be an environmental cue for the onset of breeding. In this study, we aim to describe the role of temperature upon electric organ discharge waveform in Gymnotus carapo, order Gymnotiformes, family Gymnotidae, and to analyze its interactions with the effects of steroid hormones. The effects of water temperature within its natural range were explored using different protocols. All fish tested had temperature-sensitive electric organ discharge waveforms: the amplitude of the last head-negative component (V4) decreased as temperature increased. Rate increases elicited by electrical stimulation had similar but smaller effect on waveform. Temperature sensitivity is a peripheral phenomenon that depends on the conductivity of the aquatic media. We found hormonal-dependent changes in the electric organ discharge waveform not previously described in this species. The amplitude and duration of V4 increased after testosterone administration. Both testosterone treatment and acclimation by sustained temperature at 27-28 degrees C (environmental simulation of breeding conditions) induced a decrease in temperature sensitivity. As in the related species Brachyhypopomus pinnicaudatus, our data strongly suggest interactions between temperature sensitivity of the electric organ discharge waveform and sexual maturity that might be crucial for reproduction.     

应用EPG技术分析不同品种苜蓿对苜蓿斑蚜的抗性

【目的】明确苜蓿斑蚜Therioaphis trifolii对不同品种苜蓿Medicago sativa的取食行为,探明抗蚜因子和抗虫位点,筛选抗蚜苜蓿品种。【方法】利用刺吸电位技术(electrical penetration graph, EPG)记录苜蓿斑蚜成蚜在10个苜蓿品种上的取食行为,并基于聚类分析方法筛选合适的EPG参数进行抗蚜性评价。【结果】苜蓿斑蚜成蚜在取食苜蓿过程中呈现np波、pd波、A波、B波、C波、E波、F波和G波8种波形,其中E波、F波和G波的总时间在不同品种间表现出显著差异。在5 h测试期间,E波持续时间在敖汉上最长,金皇后和中苜3号上次之,草原2号和阿尔冈金上最短;F波总时间以准格尔、阿尔冈金和金皇后上最长,敖汉、德宝和草原2号上最短,说明前者具有较强的机械抗性而后者机械抗性较弱。以第1次刺探持续时间、总刺探时间、F波总时间、C波总时间、E波总时间作为聚类分析的指标,10个苜蓿品种被聚成3类：阿尔冈金、草原2号、WL168HQ、德宝、中苜2号和新牧2号为第Ⅰ类,金皇后、中苜3号和准格尔为第Ⅱ类,敖汉为第Ⅲ类。【结论】苜蓿斑蚜成蚜在不同苜蓿品种上的取食行为存在差异,草原2号、阿尔冈金和WL168HQ在叶表皮、叶肉和韧皮部层次对苜蓿斑蚜成蚜存在抗性,金皇后在叶表皮和叶肉部位表现出抗性;苜蓿斑蚜成蚜在敖汉上能够长时间刺吸取食,因此敖汉抗性最弱。本研究为深入探讨苜蓿抗虫机理和蚜虫综合治理提供了理论参考。