Brent Bell

High resolution imaging of epithelial injury in the sheep cervicovaginal tract: a promising model for testing safety of candidate microbicides.

Background: Access to readily available large animal models and sensitive noninvasive techniques that can be used for the evaluation of microbicide-induced changes in tissue could significantly facilitate preclinical evaluations of microbicide safety. The sheep cervicovaginal tract, with stratified squamous epithelium similar to humans, holds promise as a large animal model used before nonhuman primates. In addition, optical coherence tomography (OCT) could enable high resolution visualization of tissue morphology and noninvasive assessment of microbicide-induced epithelial injury. Methods: We evaluated the dose response of sheep cervicovaginal tract to benzalkonium chloride (BZK). Twenty sheep received treatment with phosphate-buffered saline or BZK solution (2%, 0.2%, or 0.02%). Pre- and posttreatment colposcopy and OCT images were collected and graded based on World Health Organization criteria and a previously reported scoring system, respectively. Biopsies were collected and the degree of epithelial injury and its thickness was assessed based on histology and OCT. Results: The sheep cervicovagina exhibited anatomic and microscopic features similar to the human. Extensive loss of the epithelium was noted on colposcopy and OCT after application of 2% BZK. Colposcopy detected findings in half of sheep and OCT in all sheep treated with 0.2% BZK. OCT detected differences in the 0.02% BZK-treated group compared with controls, whereas colposcopy failed to detect any changes. Conclusions: The sheep cervicovagina is similar to humans, and exhibits dose dependent epithelial changes after BZK treatment. These findings suggest that the sheep model and OCT may become valuable tools for the safety evaluation of candidate microbicides, and warrant continued development.

Optoacoustic imaging of the prostate: development toward image-guided biopsy.

Optoacoustic (OA) tomography has demonstrated utility in identifying blood-rich malignancies in breast tissue. We describe the development and characterization of a laser OA imaging system for the prostate (LOIS-P). The system consists of a fiber-coupled Q-switched laser operating at 757 nm, a commercial 128-channel ultrasonic probe, a digital signal processor, and software that uses the filtered radial back-projection algorithm for image reconstruction. The system is used to reconstruct OA images of a blood-rich lesion induced in vivo in a canine prostate. OA images obtained in vivo are compared to images acquired using ultrasound, the current gold standard for guiding biopsy of the prostate. Although key structural features such as the urethra could be identified with both imaging techniques, a bloody lesion representing a highly vascularized tumor could only be clearly identified in OA images. The advantages and limitations of both forward and backward illumination modes are also evaluated by collecting OA images of phantoms simulating blood vessels within tissue. System resolution is estimated to be 0.2 mm in the radial direction of the acoustic array. The minimum detectable pressure signal is 1.83 Pa. Our results encourage further development toward a dual-modality OA/ultrasonic system for prostate imaging and image-guided biopsy.

In vivo multimodal nonlinear optical imaging of mucosal tissue

We present a multimodal nonlinear imaging approach to elucidate microstructures and spectroscopic features of oral mucosa and submucosa in vivo. The hamster buccal pouch was imaged using 3-D high resolution multiphoton and second harmonic generation microscopy. The multimodal imaging approach enables colocalization and differentiation of prominent known spectroscopic and structural features such as keratin, epithelial cells, and submucosal collagen at various depths in tissue. Visualization of cellular morphology and epithelial thickness are in excellent agreement with histological observations. These results suggest that multimodal nonlinear optical microscopy can be an effective tool for studying the physiology and pathology of mucosal tissue.

Estradiol Improves Genital Herpes Vaccine Efficacy in Mice

Herpes Simplex Virus type 2 causes genital herpes but is frequently transmitted asymptomatically; therefore, a prophylactic vaccine is desirable. A candidate vaccine in clinical trials has only shown efficacy in preventing disease in women. Using this subunit vaccine candidate, we were able to demonstrate infection prophylaxis, improved disease prevention and modulated antibody production by complimenting vaccination with estradiol in our murine model. Findings of estradiol-enhanced vaccine efficacy are the first of their kind using a vaccine of this type and have potential clinical relevance to the development of other vaccines and our understanding of gender differences in vaccine efficacy.

Noninvasive detection and staging of oral cancer in vivo with confocal optoacoustic tomography

Confocal opto-acoustic transducer (COAT) was developed and applied for detection of early stages of squamous cell carcinoma in hamster model of oral cancer. COAT is a novel imaging modality with optical and acoustic lens utilized for detecting in-depth opto-acoustic front surface transducer is an improved lateral resolution of 60-micrometers . The bandwidth of the confocal opto-acoustic transducer is more than 100 MHz. Therefore, in-depth axial resolution defined by the laser pulse duration and detection system equals 15-micrometers . Imaging was performed at the wavelength of the Nd:YAG laser second harmonic, which provided sufficient depth of monitoring and significant tissue contrast. Correlation of the opto- acoustic images with H and E histology sections in control animals and in animals treated with carcinogenic agent, DMBA, confirmed previous findings that early cancer lesions invisible by the naked eye may be detected with the opto- acoustic tomography. Compact design of COAT allows, in principle, application of the opto-acoustic imaging in any organ of the human digestive system.

Detection of Pathological Zinc Accumulation In Neurons: Methods for Autopsy, Biopsy, and Cultured Tissue:

It has been repeatedly shown that synaptically released zinc contributes to excitotoxic neuronal injury in ischemia, epilepsy, and mechanical head trauma. Such zinc-induced injury leaves an unmistakable “footprint” in the injured neurons, allowing an easy and unambiguous postmortem diagnosis. This footprint is the presence of weakly bound, histochemically reactive zinc in the cytoplasm of the perikaryon and proximal dendrites. Such staining appears to be a necessary and sufficient marker for zinc-induced neuronal injury. Here we show how to prepare and stain tissue from biopsy, autopsy, or experimental animal sources for maximal contrast and visibility of zinc-injured neurons.

Application of optical coherence tomography for monitoring changes in cervicovaginal epithelial morphology in macaques: potential for assessment of microbicide safety.

Objectives: Safety is a primary concern in the development of topical microbicides. Optical coherence tomography (OCT), a high-resolution, in-depth cross-sectional imaging modality, was utilized in conjunction with colposcopy to assess induced cervicovaginal epithelial changes that may predict product safety. Study Design: OCT and colposcopic images of macaque vaginal and cervical tissues were obtained in excised tissue and in vivo under various conditions, including mechanical injury and nonoxynol-9 treatment. Results: A scoring system was developed to categorize and quantify the OCT images based on morphologic features that indicate the presence or absence of an intact epithelial layer and inflammation. Using 3 categories (normal, mild to moderately abnormal, and severely abnormal), differences between healthy and injured tissue were apparent on OCT images. Normal images (category 1) had a bilayered structure representative of the epithelium and submucosa. Mild to moderately abnormal images (category 2) had areas of normal and abnormal epithelium. Severely abnormal images (category 3) had complete loss of the epithelium and/or inflammation, with loss of the bilayered structure on OCT. Conclusions: OCT is a noninvasive imaging modality complementary to colposcopy. It distinguished between normal and abnormal (or injured) tissue and thus holds promise for safety evaluations of candidate microbicides and other vaginal products.

Laser assisted soldering: Microdroplet accumulation with a microjet device

We investigated the feasibility of a microjet to dispense protein solder for laser assisted soldering.

Optoacoustic images of early cancer in forward and backward modes

Optoacoustic tomography combines advantages of pronounced optical contrast between different tissues and high resolution of ultrawide-band ultrasound imaging. Laser pulses may be effectively used to produce acoustic sources in tissue with enhanced optical absorption. Ultrasonic waves can propagate in biological tissue with minimal distortion and deliver diagnostic information to the surface of tissue, where they may be detected with temporal resolution by piezoelectric transducers. Current status of the optoacoustic tomography applied in early detection of cancerous lesions in the breast (utilizing forward mode) and in oral cavity (utilizing backward mode) is reviewed.

Tubal sterilization by means of endoluminal coagulation: an in vivo study in rabbits.

This study was conducted to investigate the effectiveness and safety of endoluminal tubal coagulation in obliterating the tubal lumen in rabbits. Forty female rabbits were subjected to laparotomy and hysterotomy. Endoluminal tubal coagulation was induced over a length of 3 cm in the proximal, extramural fallopian tube by using a heated stainless steel cannula or a cylindrical diffusing tip emitting argon laser radiation for one to 5 minutes. Tubal patency was evaluated by observing patterns of injected methylene blue and/or breeding success rates. Postoperative recovery was uneventful in all animals. A negative methylene blue test indicated occlusion in 51 of 52 tubes (tubal occlusion rate 98.1%), and a contraception rate of 100% in all 17 uteri in which the tube had been treated. The described endoluminal tubal coagulation method proved suitable for safe and effective sterilization in rabbits and has potential as a new transcervical tubal sterilization method for humans.