In vivo photoacoustic time-of-flight velocity measurement of single cells and nanoparticles.

Optical techniques for in vivo measurement of blood flow velocity are not quite applicable for determination of velocity of individual cells or nanoparticles. Here, we describe a photoacoustic time-of-flight method to measure the velocity of individual absorbing objects by using single and multiple laser beams. Its capability was demonstrated in vitro on blood vessel phantom and in vivo on an animal (mouse) model for estimating velocity of gold nanorods, melanin nanoparticles, erythrocytes, leukocytes, and circulating tumor cells in the broad range of flow velocity from 0.1 mm/s to 14 cm/s. Object velocity can be used to identify single cells circulating at different velocities or cell aggregates and to determine a cell's location in a vessel cross-section.

Optical monitoring of microlymphatic disturbances during experimental lymphedema.

BACKGROUND: Rat mesentery has been widely used to study microvascular functions. The goal of this work is to extend this animal model to monitor blood and lymph microvessel function during lymphedema. METHODS AND RESULTS: Lymphedema is created by microsurgical removal of regional lymph nodes (lymphadenectomy) or ligation of the collecting vein. Water volume in mesenteric tissue, microvessel diameters, phasic contraction, valve function, lymph flow velocity, and cell migration were analyzed during lymphedema development. Dynamic observation of water amount after lymphadenectomy revealed increasing edema from 30 min to 1 week; greatest degree of edema at one week, and gradual decrease in edema from 1 to 11 weeks. These effects were accompanied by acute constriction of lymph vessels and slowing of lymph flow velocity, switching to dilation and appearance of new blood capillaries at week 1, progressing to dilation and degenerative changes of the microlymphatic wall at week 4, and, finally, leading to lymphatic fibrosis and lymphangiogenesis at week 11. Acute venous insufficiency (30 min after vein ligation) led to significant edema, decreasing blood flow velocity to stasis, and output of erythrocytes from venules to interstitium, with further movement to microlymphatics and regional lymph nodes. CONCLUSIONS: Rat mesentery as an animal model in combination with an advanced optical imaging system is valuable in studying microlymphatic disturbances in mesentery during the development of experimental lymphedema from latent period to chronic stages, including monitoring of individual cell dislocation with high resolution optical imaging.

[Nitric oxide in the lymphatic microvessel regulation]. / Uchastie oksida azota v reguliatsii funktsii limfaticheskikh mikrososudov.

Topical application of sodium nitroprusside on rat mesentery has a marked influence on lymph microvessels function. The drug causes a dilation of majority of lymphangions and decrease of the pacemaker activity of the vessel wall structures and valves. These changes do not lead to lymph stasis, and lymph flow velocity does not reduce. The non-selective inhibitor of NO synthase (N-nitro-L-arginine) intensifies vasomotions of lymph microvessels, modulates phasic contractile activity and increases lymph flow velocity. There is a time dependent dynamic of changes in action of N-nitro-L-arginine. During inhibition of endogenous NO synthesis the responses of lymph microvessels on sodium nitroprusside application are modified: the constriction of majority lymphangions and activation of valve work are observed.

Experimental evaluation on the transmission optical microscopy for the diagnosis of lymphedema.

The mechanisms of disturbance of lymph microcirculation during development postmastectomy lymphedema (PML) are little known. The study of these mechanisms on human subjects has many difficulties: time of clinical onset of PML is indefinite and unpredictable and the methods for imaging of microlymphatics are limited. The advantages of the optical methods, especially, light microscopy are the high quality of lymphocytes dynamic imaging, possibility of the determination of absolute lymph flow velocity in a wide range, capability for simultaneous registration of blood microvessel function around lymphatics. The experimental lymphedema is created on rat mesentery by ligation of the collecting vein. It was found that after such ligation edema was clearly developed, and microcirculation was significantly disturbed including reduction of lymph flow velocity, constriction of lymphatics, inhibition of phasic activity on the background of pathological increasing of blood vessels permeability and stasis of blood flow.

Changes in lymph microcirculation during pathological stress.

Stress caused by immobilization and acoustic stimulation produces considerable changes in lymph microcirculation. These changes manifested in dilation of microvessels, enhanced phasic contractile activity and its abnormal pattern, accelerated lymph flow, and recruitment of new lymphangions in drainage functions.

[Functional organization of lymphatic microvessels of the rat mesentery]. / Funltsional'naia organizatsiia limfaticheskikh mikrososudov bryzheiki krysy.

Lymph flow as measured with biomicroscopic and speckle-interferometrical techniques was very unstable and its rate did not depend on lymphangion diameter in the rat mesentery. A correlation was found between amount of cells in the lymph flow and other indices of lymphangion functions. All microvessels with phasic contractions and/or working valve were revealed as having a lymph flow. The phasic activity and the valve work correlated with each other. The higher the amplitude and frequency of the phasic activity and the longer the contraction cycle, the higher was the rate of the valve work.