Abstract-It has been proposed that adenosine is a metabolic signal that triggers activation of muscle afferents involved in the exercise pressor reflex. Furthermore, exogenous adenosine induces sympathetic activation that mimics the exercise pressor reflex, and blockade of adenosine receptors inhibits sympathetic activation induced by exercise. Thus, we hypothesize that adenosine is released locally by the muscle during exercise. We used microdialysis probes, placed in the flexor digitorium superficialis muscle, to estimate muscle interstitial adenosine levels in humans. We estimated resting in vivo muscle interstitial adenosine concentrations (0.292Ϯ0.058 mol/L, nϭ4) by perfusing increasing concentrations of adenosine to determine the gradient produced in the dialysate. Key Words: microdialysis Ⅲ adenosine Ⅲ muscle, skeletal Ⅲ exercise Ⅲ lactates M icrodialysis is a relatively new and minimally invasive technique that allows continuous sampling of extracellular substances of small molecular weight that will diffuse through the dialysis membrane. 1,2 It has been used to estimate interstitial concentrations of lactate, glucose, glutamate, norepinephrine, and adenosine, among others. 3 Over the last few years, the microdialysis technique has been introduced in human research, mostly to study skeletal muscle and subcutaneous metabolites. 4 We theorized that this technique would be particularly useful in the determination of extracellular concentrations of metabolites in which rapid cellular uptake and/or degradation constitutes a major limitation to their measurement by traditional techniques. Adenosine is one such metabolite.We have previously presented evidence supporting a role of adenosine in the triggering of the exercise pressor reflex, 5 the sympathetic activation resulting from isometric handgrip. We have found that exogenous adenosine induces sympathetic activation that mimics the exercise pressor reflex 6 and that blockade of adenosine receptors attenuates sympathetic activation induced by isometric exercise. 5 We postulate, therefore, that endogenous adenosine is released from skeletal muscle during ischemic exercise and activates muscle afferent fibers involved in the triggering of this reflex.It is difficult to test this hypothesis directly because of the challenges involved in measuring adenosine levels. Previous studies have used tissue biopsies to measure adenosine levels during ischemia. Whole tissue levels, however, do not discriminate between increases produced in the intracellular compartment or the interstitial space, the probable site of action. Attempts have also been made to measure adenosine levels in venous effluent. However, once outside the cell, adenosine is rapidly metabolized by adenosine deaminase and is reuptaken into cells via a very effective transporter. These processes explain the extremely short half-life of adenosine in human blood, reportedly Ͻ1 second. 7 Furthermore, the endothelium acts as an effective barrier to adenosine. 8 The microdialysis technique offers theoretical a...
High-grade serous carcinoma of the ovary is believed to originate in the fallopian tubes (FTs). A submillimeter diameter endoscope with advanced imaging capabilities may take advantage of the natural pathway of the female reproductive tract to image the FTs in a minimally invasive procedure for early detection of cancer. Our lab previously built a prototype benchtop FT endoscope with pseudowhite light imaging, multispectral fluorescence imaging and optical coherence tomography. This endoscope was approximately 0.9 mm in diameter, flexible and steerable in one direction. Several modifications have been made to create a falloposcope imaging system which is ready for clinical use. This new design includes a multilumen extrusion, a revised handle design, simplified lens design and redesigned subsystems resulting in improved mechanical characteristics, biocompatibility and portability while maintaining image quality. Additionally, these clinical endoscopes are single use, considerably less expensive and faster to build as compared to the prototype.
Microendoscopes are commonly used in small lumens in the body for which a focus near to the distal tip and ability to operate in an aqueous environment are paramount for navigation and disease detection. Commercially available distal optic systems below 1 mm in diameter are severely limited, and custom micro lenses are generally very expensive. Gradient index of refraction (GRIN) singlets are available in small diameters but have limited optical performance adjustability. Three-dimensional (3D)-printed monolithic optical systems are an emerging option that may be suitable for enabling high performance, close-focus imaging. In this manuscript, we compared the optical performance of three custom distal optic systems; a custom-pitch GRIN singlet, 3D-printed monolithic doublet, and 3D-printed monolithic triplet, with a nominal working distance (WD) of 1.5, 0.5, and 0.4 mm in 0.9% saline. These short WDs are ideal for microendoscopy in collapsed or flushed lumens such as pancreatic duct or fallopian tube. The GRIN singlet had performance limited only by the fiber bundle relay over 0.9-to 1.6-mm depth of field (DOF). The 3D-printed doublet was able to achieve a comparable DOF of 0.71 mm, whereas the 3D-printed triplet suffered the most limited DOF of 0.55 mm. 3D printing enables flexible design of monolithic multielement systems with aspheric surfaces of very short WDs and relative ease of integration.
For small, uncomplicated vesico-vaginal fistulas, a transvaginal approach has an equivalent success rate to that of other approaches with less invasiveness and faster recovery times. Therefore, it is reasonable to use a modified Latzko technique to help restore the quality of life to women affected by small, uncomplicated vesico-vaginal fistulas.
We present the design and feasibility testing of a multimodal co-registered endoscope based on a dual-path optical system integrated with a scanning piezo. This endoscope incorporates three different imaging modalities. A large field-of-view (FOV) reflectance imaging system enables visualization of objects several millimeters in front of the endoscope, while optical coherence microscopy (OCM) and multiphoton microscopy (MPM) are employed in contact with tissue to further analyze suspicious areas. The optical system allows multiple different imaging modalities by employing a dual optical path. One path features a low numerical aperture (NA) and wide FOV to allow reflectance imaging of distant objects. The other path features a high NA and short working distance to allow microscopy techniques such as OCM and MPM. Images of test targets were obtained with each imaging modality to verify and characterize the imaging capabilities of the endoscope. The reflectance modality was demonstrated with a 561 nm laser to allow high contrast with blood vessels. It achieved a lateral resolution of 24.8 μm at 5 mm and a working distance from 5 to 30 mm. OCM was performed with a 1300 nm super-luminescent diode since this wavelength experiences low relative scattering to allow for deeper tissue imaging. Measured OCM lateral and axial resolution was 4.0 and 14.2 μm, respectively. MPM was performed with a custom 1400 nm femtosecond fiber laser, a wavelength suitable for exciting multiple exogenous, and some endogenous fluorophores, as well as providing information on tissue composition through harmonic generation processes. A 4.0 × μm MPM lateral resolution was measured.
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