A Study of the Oscillatory Components of the Skin Microhemodynamics in Mice by Laser Doppler Flowmetry

A skin blood flow was studied by laser doppler flowmetry. Fourteen male BALB/c mice were used. The skin blood flow was registered in the left hind paw. To measure the skin microhemodynamics, we proposed a protocol of animal immobilization with two types of anesthesia, injection with zoletil and inhalation with nitrous oxide. The borders of low-frequency intervals of oscillations of the microhemodynamics in mice have been determined; they coincided with those for humans and rats that were determined earlier.     

Functional Evaluation of the Perivascular Innervation of the Skin of the Extremities Using Laser Doppler Flowmetry

Examination of 30 healthy subjects and 132 patients with hand denervation syndrome who were aged 16 to 30 years demonstrated that laser Doppler flowmetry is a highly effective approach to both qualitative and quantitative characterization of the nervous regulation of the microvasculature and the perivascular innervation of the skin. To study the sympathetic adrenergic perivascular innervation, it is expedient to evaluate the ratio between the neurogenic tone of afferent microvessels at rest and the decrease in microcirculation during the vasoconstrictive breath-holding test. The sensory peptidergic component of control is evaluated by electric stimulation of nociceptive afferent nerves, which causes antidromic vasodilation. The results of the study demonstrate the possibility of both concordant and discordant changes in sympathetic vascular regulation and isolated predominance of functional activity of the sympathetic or sensory peptidergic components of perivascular innervation.     

Multifractality in the peripheral cardiovascular system from pointwise holder exponents of laser Doppler flowmetry signals

We study the dynamics of skin laser Doppler flowmetry signals giving a peripheral view of the cardiovascular system. The analysis of Hölder exponents reveals that the experimental signals are weakly multifractal for young healthy subjects at rest. We implement the same analysis on data generated by a standard theoretical model of the cardiovascular system based on nonlinear coupled oscillators with linear couplings and fluctuations. We show that the theoretical model, although it captures basic features of the dynamics, is not complex enough to reflect the multifractal irregularities of microvascular mechanisms.In clinical and physiological investigations, the cardiovascular system dynamics can be considered from a central or from a peripheral point of view. Heart-beat interval sequences, reflecting a central view of the human cardiovascular system, have been analyzed and the results have shown that they display multifractal properties for healthy subjects (1). A peripheral view of the cardiovascular system dynamics is possible by studying microvascular blood flow signals given by the laser Doppler flowmetry technique (2). These signals have complex dynamics, with fractal structures and chaos (3,4). However, are these data, reflecting the underlying mechanisms acting at the microscopic level of the human physiology, as irregular as those giving a central view point of the system dynamics? Is a single fractal exponent sufficient to characterize them? Moreover, a set of nonlinear coupled oscillators has recently been proposed as a standard theoretical model of the cardiovascular system (5–8). Is the dynamics of the corresponding simulated data close to the one of real cardiovascular signals?Herein we report that skin laser Doppler flowmetry signals display multifractal properties on young healthy subjects at rest. By estimating Hölder exponents of signals recorded on the finger, we show that the dynamics of peripheral signals can be irregular, as central data are. We also conclude that the use of a standard theoretical model of the cardiovascular system, based on five nonlinear coupled oscillators with linear couplings and fluctuations, is not complex enough to model the multifractal properties of the cardiovascular system. To our knowledge, it is the first time that multifractality of experimental and simulated laser Doppler flowmetry signals is studied.The rapid changes in a time series are called singularities and a characterization of their strength is obtained with the Hölder exponents (9). When a broad range of exponents is found, signals are considered as multifractal. A narrow range implies monofractality. One of the most widely used monofractal signal models is the fractional Brownian motion. In opposition, multifractal signals are more complex and inhomogeneous. The multifractal formalism has been established to account for the statistical scaling properties of time series observed in various physical situations. A singularity spectrum D(h) of a signal is the function that gives, for a fixed h, the Hausdorff dimension of the set of points x where the Hölder exponent h(x) is equal to h. The Hölder exponent h(x₀) of a function f at the point x₀ is the highest h value so that f is Lipschitz at x₀. There exists a constant C and a polynomial P_n(x) of order n so that for all x in a neighborhood of x₀ we have (10,11)(1)The Hölder exponent measures the degree of irregularity of f at the point x₀.We analyze experimental skin laser Doppler flowmetry signals reflecting microvascular blood flow. The signals are recorded with a frequency sampling of 20 Hz on the finger of seven young healthy people between 20 and 35 years old (12). A laser Doppler flowmetry signal is shown in Fig. 1. For each recording, 15,601 pointwise Hölder exponents are taken into account. They are computed with a parametric generalized quadratic variation based estimation method (13). Open in a separate windowFIGURE 1Skin laser Doppler flowmetry signal recorded on a young healthy subject at rest.For the skin laser Doppler flowmetry signals, we find a minimum Hölder exponent of 0.56, a maximum of 0.71, a mean value of 0.63, and a standard deviation of 0.03 (average values over seven signals). The difference between the minimum and maximum Hölder exponents is therefore of 0.15. An example of Hölder exponent time series is shown in Fig. 2. To compare the results with known mono and multifractal data, we generate a fractional Brownian motion (monofractal signal) and a multifractional Brownian motion (multifractal signal) (14). For each data, 15,601 pointwise Hölder exponents are taken into account. Open in a separate windowFIGURE 2Hölder exponents for a skin laser Doppler flowmetry signal recorded on a young healthy subject at rest.

TABLE 1

Value for the minimum, maximum, range, mean, and standard deviation of the Hölder exponents computed for skin laser Doppler flowmetry (LDF) signals (average value computed over seven signals), for a monofractal signal (fBm), and for a multifractal signal (mBm)

Quantification of the Blood Platelet Reactivity in the ADP-Induced Model of Non-Lethal Pulmonary Thromboembolism in Mice with the Use of Laser Doppler Flowmetry

IntroductionThe paper describes an alternative method for quantification of in vivo ADP-induced thromboembolism. The aim of the studies was to develop a method of quantification which would not require either extravasation or labelling of platelets. Our proposed approach is based on the monitoring of changes of blood flow with the use of laser Doppler flowmetry.ResultsThe injection of ADP resulted in a dose-dependent reduction of the blood flow in the mesentery. These responses were fully attributable to blood platelet aggregation, as shown by the lack of the effect in platelet-depleted mice, and significantly reduced responses in mice pretreated with cangrelor and eptifibatide. No platelet aggregate formation in mesenteric vessels was revealed by intravital microscopy, while ex vivo imaging showed accumulation of fluorescent labelled platelets in the lung.ConclusionsInjection of ADP to the venous system results in the formation of platelet aggregates predominantly in the lung. This results in reversible blood flow cessation in peripheral blood vessels. The measurement of this blood flow cessation in the mesentery allows indirect measurement of ADP-induced pulmonary thromboembolism. We suggest that this approach can be useful for in vivo screening for antiplatelet drug candidates.     

稳恒流下腹主动脉旁瘤超声多普勒血流信号的仿真分析

腹主动脉旁瘤超声多普勒血流信号的仿真研究,可以为采用超声多普勒技术检测腹主动脉旁瘤的形成、生长过程和估计动脉旁瘤瘤体大小提供指导。先通过有限元数值计算方法得到稳恒流下腹主动脉旁瘤区域内的血液流场分布,然后采用余弦叠加的合成方法仿真出相应的超声多普勒血流信号,最后对仿真信号进行频谱分析,计算其平均频率,并研究它与腹主动脉旁瘤瘤体大小的关系。结果表明：当动脉旁瘤较小时,平均频率的幅度变化较小;当动脉旁瘤较大时,平均频率的幅度变化较大。因此,采用平均频率的幅度变化可以在一定程度上估计动脉旁瘤的瘤体大小。     

Evolution of the Cardiovascular System in Crustacea

An attempt is made to explain the evolution of different cardiovascularmorphologies of crustaceans on the basis of (1) changes in thedevelopment of the body plan of different species, (2) the adventin the malacostracans of segmental arteries that provided thecirculatory potential for growth in body size and speciation,(3) the need for more powerful hearts to propel blood throughlarger bodies, and (4) the embryological substrate that wouldallow for the development of regional specialization. Electrophysiologicalevidence supports the hypothesis that the archetypal crustaceanheart was myogenic, but in more advanced forms this pacemakingmechanism has become subservient to the neural drive from thecardiac ganglion. This transition may have been the result ofthe selective advantages to possessing a discrete cardiac ganglion,which itself was easily controlled by nervous inputs from theCNS and by circulating hormones.     

Octopamine Release from Centrifugal Fibers of the Limulus Peripheral Visual System

Abstract: Octopamine, a biogenic amine, is synthesized and stored within centrifugal (efferent) fibers that project from the brain to the lateral and ventral eyes of the horseshoe crab, Limulus polyphemus . The experiments described here show that depolarization of Limulus lateral and ventral eyes, produced by elevating the concentration of extracellular K⁺, causes the selective release of newly synthesized octopamine from centrifugal fibers in a manner that requires the influx of extracellular Ca²⁺. Conjugates of octopamine and tyramine that are also stored within centrifugal fibers are not released in response to K⁺-induced depolarization. These findings add further support to the hypothesis that octopamine is a neurotransmitter synthesized by and released from centrifugal fibers in Limulus eyes. This amine may be responsible for many of the alterations in lateral eye structure and function that are mediated by centrifugal inner-vation.     

Developmental Expression of the Myelin-Associated Glycoprotein in the Peripheral Nervous System Is Different from That in the Central Nervous System

We recently characterized two developmentally regulated myelin-associated glycoprotein (MAG) polypeptides synthesized by mouse brain mRNA in vitro. We now extended these studies to include the peripheral nervous system (PNS). Total cytoplasmic RNA was isolated from the sciatic nerves of 7-, 12-, and 17-day-old and adult rats and translated in vitro in a rabbit reticulocyte lysate system. In contrast to results in the CNS, it appears that only one MAG polypeptide, p67MAG, is synthesized by PNS mRNA at all ages. The implications of these findings are discussed with respect to recent observations concerning both the localization of MAG and the synthesis of MAG in the PNS of dysmyelinating mutant mice.     

Veratridine-Stimulated Release of Amine Conjugates from Centrifugal Fibers in the Limulus Peripheral Visual System

Centrifugal fibers that originate in the brain and project to the Limulus peripheral visual system synthesize and store octopamine and conjugates of octopamine and tyramine. In a previous study we showed that depolarization, induced by elevating extracellular K+, stimulated a preferential release of octopamine from these fibers. Here we show that veratridine-induced depolarization stimulates a rapid, transient release of octopamine and a delayed, sustained release of amine conjugates. Veratridine-stimulated release of both octopamine and amine conjugates depends on the influx of extracellular Ca2+ and is blocked by tetrodotoxin or the absence of extracellular Na+. The depolarization-stimulated release of amine conjugates raises the possibility that these molecules serve as intercellular messengers in the Limulus peripheral visual system.     

Mouse Forward Genetics in the Study of the Peripheral Nervous System and Human Peripheral Neuropathy

Forward genetics, the phenotype-driven approach to investigating gene identity and function, has a long history in mouse genetics. Random mutations in the mouse transcend bias about gene function and provide avenues towards unique discoveries. The study of the peripheral nervous system is no exception; from historical strains such as the trembler mouse, which led to the identification of PMP22 as a human disease gene causing multiple forms of peripheral neuropathy, to the more recent identification of the claw paw and sprawling mutations, forward genetics has long been a tool for probing the physiology, pathogenesis, and genetics of the PNS. Even as spontaneous and mutagenized mice continue to enable the identification of novel genes, provide allelic series for detailed functional studies, and generate models useful for clinical research, new methods, such as the piggyBac transposon, are being developed to further harness the power of forward genetics. Special issue article in honor of Dr. George DeVries.     

Laser Doppler velocimetry measurement in the model flow of a fish olfactory organ

The velocity field of the flow in the olfactory organ of a fish,exemplified by the swordtail Xiphophorus helleri, was investigatedby a three-component laser Doppler velocimetry (LDV) systemin a simulated stationary model flow at an enlarged scale, butconserving hydrodynamic similarity. Both the crossed beam andthe reference beam methods were applied to study the inflowphase. The complexity of the vector field is depicted in sectionalviews by isolines and arrow patterns. The power of the LDV techniqueand model simulation for such investigations is demonstrated.     

Evaluation of the Microcirculation in a Rabbit Hemorrhagic Shock Model Using Laser Doppler Imaging

The aim of this study is to evaluate the feasibility of Laser Doppler imaging (LDI) for noninvasive and dynamic assessment of hemorrhagic shock in a rabbit model. A rabbit model of hemorrhagic shock was generated and LDI of the microcirculation in the rabbit ears was performed before and at 0, 30, 60, and 90 min after hemorrhage. The CCD (Charge Coupled Device) image of the ears, the mean arterial pressure (MAP) and the heart rate (HR) were monitored. The mean LDI flux was calculated. The HR of rabbits was significantly (p < 0.05) elevated and the MAP was decreased after hemorrhage, compared to the pre-hemorrhage level. Within the initial 30 min after hemorrhage, the perfusion flux lineally dropped down. In contrast, the MAP values did not differ significantly between the time points of 0 and 30 after hemorrhage (p > 0.05). Both the flux numbers and the red-to-blue color changes on LDI imaging showed the reduction of the microcirculation. LDI imaging is a noninvasive and non-contact approach to evaluate the microcirculation and may offer benefits in the diagnosis and treatment of hemorrhage shock. Further studies are needed to confirm its effectiveness in clinical practice.     

Biochemical Demonstration of the Myelin-Associated Glycoprotein in the Peripheral Nervous System

Abstract: Recent immunocytochemical studies indicated that the myelin-associated glycoprotein (MAG) is localized in the periaxonal region of central nervous system (CNS) and peripheral nervous system (PNS) myelin sheaths but previous biochemical studies had not demonstrated the presence of MAG in peripheral nerve. The glycoproteins in rat sciatic nerves were heavily labeled by injection of [³H]fucose in order to re-examine whether MAG could be detected chemically in peripheral nerve. Myelin and a myelin-related fraction, WI, were isolated from the nerves. Labeled glycoproteins in the PNS fractions were extracted by the lithium diiodosalicylate (LIS)-phenol procedure, and the extracts were treated with antiserum prepared to CNS MAG in a double antibody precipitation. This resulted in the immune precipitation of a single [³H]fucose-labeled glycoprotein with electrophoretic mobility very similar to that of [¹⁴C]fucose-labeled MAG from rat brain. A sensitive peptide mapping procedure involving iodination with Bolton-Hunter reagent and autoradiography was used to compare the peptide maps generated by limited proteolysis from this PNS component and CNS MAG. The peptide maps produced by three distinct proteases were virtually identical for the two glycoproteins, showing that the PNS glycoprotein is MAG. The MAG in the PNS myelin and Wl fractions was also demonstrated by Coomassie blue and periodic acid-Schiff staining of gels on which the whole US-phenol extracts were electrophoresed, and densitometric scanning of the gels indicated that both fractions contained substantially less MAG than purified rat brain myelin. The presence of MAG in the periaxonal region of both peripheral and central myelin sheaths is consistent with a similar involvement of this glycoprotein in axon-sheath cell interactions in the PNS and CNS.     

The Next Generation in Laser Treatments and the Role of the GreenLight High-Performance System Laser

Lasers have evolved over the past decade, with technical refinements that have resulted in a procedure that can achieve transurethral-like results in a safe and efficacious manner. The physics and characteristics of the laser light, such as wavelength and power densities, influence efficiency of treatment and safety profiles of various laser techniques and systems. The currently commercially available 80-W potassium-titanyl-phosphate laser used for photoselective vaporization of the prostate gland in men with lower urinary tract symptoms and benign prostatic hyperplasia has been shown to be a safe and effective therapeutic alternative for a wide spectrum of prostate sizes and configurations. Refinements based on clinical experience as well as progress in available technologies have produced an advanced system with improvements in beam quality and an increase in power to provide an increase in vaporization efficiency and flexibility in technique. The refinements require adjustments to current technique. The advanced technological developments enhance the utility of this laser for application in benign prostatic hyperplasia and urology.