Impact of Injection-Based Delivery Parameters on Local Distribution Volume of Ethyl-Cellulose Ethanol Gel in Tissue and Tissue Mimicking Phantoms

OBJECTIVE

Local drug delivery aims to minimize systemic toxicity by preventing off-target effects; however, injection parameters influencing depot formation of injectable gels have yet to be thoroughly studied. We explored the effects of needle characteristics, injection depth, rate, volume, and polymer concentration on gel ethanol distribution in both tissue and phantoms.

METHODS

The polymer ethyl cellulose (EC) was added to ethanol to form an injectable gel to ablate cervical precancer and cancer. Tissue mimicking phantoms composed of 1% agarose dissolved in deionized water were used to establish overall trends between various injection parameters and the resulting gel distribution. Additional experiments were performed in excised swine cervices with a CT-imageable injectate formulation, which enabled visualization of the distribution without tissue sectioning.

RESULTS

Needle type and injection rate had minimal impact on gel distribution, while needle depths ≥13 mm yielded significantly larger distributions. Needle gauge and EC concentration impacted injection pressure with maximum gel distribution achieved when the pressure was 70-250 kPa. Injection volumes ≤3 mL of 6% EC-ethanol minimized fluid leakage away from the injection site. Results guided the development of a speculum-compatible hand-held injector to deliver gel ethanol into the cervix.

CONCLUSION

Needle depth, gauge, and polymer concentration are critical to consider when delivering injectable gels.

SIGNIFICANCE

This study addressed key questions related to the impact of injection-based parameters on gel distribution at a scale relevant to human applications including: 1) how best to deliver EC-ethanol into the cervix and 2) general insights about injection protocols relevant to the delivery of injectable gels in tissue.

In Vivo Evaluation of Safety and Efficacy of Ethyl Cellulose-Ethanol Tissue Ablation in a Swine Cervix Model

Current therapies for treating cervical dysplasia are often inaccessible in low and middle-income countries (LMICs), highlighting the need for novel low-cost therapies that can be delivered at the point of care. Ethanol ablation is a low-cost therapy designed to treat locoregional cancers, which we augmented into an ethyl cellulose (EC)-ethanol gel formulation to enhance its efficacy. Here, we evaluated whether EC-ethanol ablation is able to safely achieve an ablation zone comparable to thermocoagulation, a commonly used therapy for cervical dysplasia. The study was performed in 20 female Yorkshire pigs treated with either a single 500 µL injection of EC-ethanol into the 12 o'clock position of the cervix or a single application of thermocoagulation at 100 °C for 20 s. The average temperature, heart rate, respiratory rate, and blood oxygen remained within normal ranges throughout the EC-ethanol procedure and were similar to the thermocoagulation group. No major side effects were observed. The reproductive tracts were excised after 24 h to examine ablation zones. Comparable depths of necrosis were seen for EC-ethanol (18.6 ± 1.6 mm) and thermocoagulation (19.7 ± 4.1 mm). The volumes of necrosis induced by a single injection of EC-ethanol (626.2 ± 122.8 µL) were comparable to the necrotic volumes induced by thermocoagulation in the top half of the cervices (664.6 ± 168.5 µL). This suggests that two EC-ethanol injections could be performed (e.g., at the 12 and 6 o'clock positions) to achieve comparable total necrotic volumes to thermocoagulation and safely and effectively treat women with cervical dysplasia in LMICs. This is the first study to systematically evaluate EC-ethanol ablation in a large animal model and compare its safety and efficacy to thermocoagulation, a commonly used ablative therapy for cervical dysplasia.

Locoregional Thermal and Chemical Tumor Ablation: Review of Clinical Applications and Potential Opportunities for Use in Low- and Middle-Income Countries

This review highlights opportunities to develop accessible ablative therapies to reduce the cancer burden in LMICs.

KeyLoop retractor for global gasless laparoscopy: evaluation of safety and feasibility in a porcine model

BACKGROUND

Many surgeons in low- and middle-income countries have described performing surgery using gasless (lift) laparoscopy due to inaccessibility of carbon dioxide and reliable electricity, but the safety and feasibility of the technique has not been well documented. We describe preclinical testing of the in vivo safety and utility of KeyLoop, a laparoscopic retractor system to enable gasless laparoscopy.

METHODS

Experienced laparoscopic surgeons completed a series of four laparoscopic tasks in a porcine model: laparoscopic exposure, small bowel resection, intracorporeal suturing with knot tying, and cholecystectomy. For each participating surgeon, the four tasks were completed in a practice animal using KeyLoop. Surgeons then completed these tasks using standard-of-care (SOC) gas laparoscopy and KeyLoop in block randomized order to minimize learning curve effect. Vital signs, task completion time, blood loss and surgical complications were compared between SOC and KeyLoop using paired nonparametric tests. Surgeons completed a survey on use of KeyLoop compared to gas laparoscopy. Abdominal wall tissue was evaluated for injury by a blinded pathologist.

RESULTS

Five surgeons performed 60 tasks in 15 pigs. There were no significant differences in times to complete the tasks between KeyLoop and SOC. For all tasks, there was a learning curve with task completion times related to learning the porcine model. There were no significant differences in blood loss, vital signs or surgical complications between KeyLoop and SOC. Eleven surgeons from the United States and Singapore felt that KeyLoop could be used to safely perform several common surgical procedures. No abdominal wall tissue injury was observed for either KeyLoop or SOC.

CONCLUSIONS

Procedure times, blood loss, abdominal wall tissue injury and surgical complications were similar between KeyLoop and SOC gas laparoscopy for basic surgical procedures. This data supports KeyLoop as a useful tool to increase access to laparoscopy in low- and middle-income countries.

Crucial Business Model Elements for Medical Device Startup Companies in Emerging Markets

OBJECTIVES

Medical devices that suit the needs and challenges of low- and middle-income countries are desperately needed. To provide sustainable access to such devices, business approaches must be developed to meet the demands of individual economic, healthcare, and innovation ecosystems. Currently, there is a gap in the literature regarding business models for medical devices in low- and middle-income countries.

METHODS

A multimodal approach using literature review and key informant interviews was performed to determine critical components of business models for medical device organizations operating in LMICs, specifically focusing on models in emerging markets.

RESULTS

The search resulted in 4,674 articles, of which 31 were determined to be relevant and were reviewed. Additional sources included 1 government website, 5 nongovernmental organization websites, 2 private enterprises, and 6 publicly available, non-peer reviewed websites and 1 video. From these sources, four major criteria were found to be necessary for successful development of medical device business models in emerging markets: value proposition, partnerships, strategic pricing, and funding models.

CONCLUSIONS

Innovators must custom tailor their business model when implementing these elements to the regulatory, cultural, and economic landscapes of each setting. This will improve access to safer, affordable medical care and successfully bring innovative technologies to emerging markets.

Design and calibration of a Tonpilz transducer for low frequency medical ultrasound tomography

The design and performance of a transducer for low frequency ultrasound tomography is presented, motivated by recent research demonstrating that acoustic waves transmitting at frequencies between 10 kHz and 750 kHz penetrate the lungs and may be useful for thoracic imaging. An adaptation of the traditional Tonpilz design was developed, vibrational amplitude and electrical impedance were measured, and an optimal frequency was determined. The design is found to meet the desired mechanical, electrical, and safety specifications. Thus, it was considered a promising option for the target application of pulmonary imaging with ultrasound computed tomography between 50 and 200 kHz; highest efficiency achieved around 125 kHz and 156 kHz, and beam divergence of 40°.

Intratumoral Photosensitizer Delivery and Photodynamic Therapy

Photodynamic therapy (PDT) is a two-step procedure that involves the administration of special drugs, commonly called photosensitizers, followed by the application of certain wavelengths of light. The light activates these photosensitizers to produce reactive molecular species that induce cell death in tissues. There are numerous factors to consider when selecting the appropriate photosensitizer administration route, such as which part of the body is being targeted, the pharmacokinetics of photosensitizers, and the formulation of photosensitizers. While intravenous, topical, and oral administration of photosensitizers are widely used in preclinical and clinical applications of PDT, other administration routes, such as intraperitoneal, intra-arterial, and intratumoral injections, are gaining traction for their potential in treating advanced diseases and reducing off-target toxicities. With recent advances in targeted nanotechnology, biomaterials, and light delivery systems, the exciting possibilities of targeted photosensitizer delivery can be fully realized for preclinical and clinical applications. Further, in light of the growing burden of cancer mortality in low and middle-income countries and development of low-cost light sources and photosensitizers, PDT could be used to treat cancer patients in low-income settings. This short article introduces aspects of interfaces of intratumoral photosensitizer injections and nano-biomaterials for PDT applications in both high-income and low-income settings but does not present a comprehensive review due to space limitations.

Optimizing ethyl cellulose-ethanol delivery towards enabling ablation of cervical dysplasia

In low-income countries, up to 80% of women diagnosed with cervical dysplasia do not return for follow-up care, primarily due to treatment being inaccessible. Here, we describe development of a low-cost, portable treatment suitable for such settings. It is based on injection of ethyl cellulose (EC)-ethanol to ablate the transformation zone around the os, the site most impacted by dysplasia. EC is a polymer that sequesters the ethanol within a prescribed volume when injected into tissue, and this is modulated by the injected volume and delivery parameters (needle gauge, bevel orientation, insertion rate, depth, and infusion rate). Salient injection-based delivery parameters were varied in excised swine cervices. The resulting injection distribution volume was imaged with a wide-field fluorescence imaging device or computed tomography. A 27G needle and insertion rate of 10 mm/s achieved the desired insertion depth in tissue. Orienting the needle bevel towards the outer edge of the cervix and keeping infusion volumes ≤ 500 µL minimized leakage into off-target tissue. These results guided development of a custom hand-held injector, which was used to locate and ablate the upper quadrant of a swine cervix in vivo with no adverse events or changes in host temperature or heart rate. After 24 h, a distinct region of necrosis was detected that covered a majority (> 75%) of the upper quadrant of the cervix, indicating four injections could effectively cover the full cervix. The work here informs follow up large animal in vivo studies, e.g. in swine, to further assess safety and efficacy of EC-ethanol ablation in the cervix.

The Evolving Landscape of Medical Device Regulation in East, Central, and Southern Africa

Effective regulatory frameworks, harmonized to international standards, are critical to expanding access to quality medical devices in low- and middle-income countries. This review provides a summary of the state of medical device regulation in the 14 member countries of the College of Surgeons of East, Central, and Southern Africa (COSECSA) and South Africa. Countries were categorized according to level of regulatory establishment, which was found to be positively correlated to gross domestic product (GDP; rs=0.90) and years of freedom from colonization (rs=0.60), and less positively correlated to GDP per capita (rs=0.40). Although most countries mandate medical device regulation in national legislation, few employ all the guidelines set forth by the World Health Organization. A streamlined regulatory process across African nations would simplify this process for innovators seeking to bring medical devices to the African market, thereby increasing patient access to safe medical devices.

Polymer-assisted intratumoral delivery of ethanol: Preclinical investigation of safety and efficacy in a murine breast cancer model

Focal tumor ablation with ethanol could provide benefits in low-resource settings because of its low overall cost, minimal imaging technology requirements, and acceptable clinical outcomes. Unfortunately, ethanol ablation is not commonly utilized because of a lack of predictability of the ablation zone, caused by inefficient retention of ethanol at the injection site. To create a predictable zone of ablation, we have developed a polymer-assisted ablation method using ethyl cellulose (EC) mixed with ethanol. EC is ethanol-soluble and water-insoluble, allowing for EC-ethanol to be injected as a liquid and precipitate into a solid, occluding the leakage of ethanol upon contact with tissue. The aims of this study were to compare the 1) safety, 2) release kinetics, 3) spatial distribution, 4) necrotic volume, and 5) overall survival of EC-ethanol to conventional ethanol ablation in a murine breast tumor model. Non-target tissue damage was monitored through localized adverse events recording, ethanol release kinetics with Raman spectroscopy, injectate distribution with in vivo imaging, target-tissue necrosis with NADH-diaphorase staining, and overall survival by proxy of tumor growth. EC-ethanol exhibited decreased localized adverse events, a slowing of the release rate of ethanol, more compact injection zones, 5-fold increase in target-tissue necrosis, and longer overall survival rates compared to the same volume of pure ethanol. A single 150 μL dose of 6% EC-ethanol achieved a similar survival probability rates to six daily 50 μL doses of pure ethanol used to simulate a slow-release of ethanol over 6 days. Taken together, these results demonstrate that EC-ethanol is safer and more effective than ethanol alone for ablating tumors.

Laparoscopic experience and attitudes toward a low-cost laparoscopic system among surgeons in East, Central, and Southern Africa: a survey study

BACKGROUND

Laparoscopic surgery has become standard of care in high-income countries but is rarely accessible in low- and middle-income countries (LMICs). This study assessed experience with laparoscopy and attitudes toward a low-cost laparoscopic system among surgeons in sub-Saharan Africa.

METHODS

A survey assessing current laparoscopic practice and feedback on a low-cost laparoscopic system was administered to attendees of the College of Surgeons of East, Central, and Southern Africa (COSECSA) Scientific Conference between December 4 and December 6, 2019 in Kampala, Uganda.

RESULTS

Fifty-six surgeons from 14 countries participated. A majority were male (n = 46, 82%) general surgeons (n = 37, 66%) from tertiary/teaching hospitals (n = 36, 64%). For those with training in laparoscopy (n = 33, 59%), 22 (67%) reported less than 1 year of training and over half (n = 17, 52%) reported 1 month or less. Overall, a minority (n = 21, 38%) used laparoscopy in current practice, with 57% (n = 12) of those performing laparoscopy less than once per week. The most common laparoscopic surgeries performed were cholecystectomy (n = 15), diagnostic laparoscopy (n = 14), and appendectomy (n = 12). Few surgeons were performing more complex cases (n = 5). Barriers to laparoscopy included poor access to training equipment (n = 34, 61%), mentors (n = 33, 59%), laparoscopic equipment (n = 31, 55%), equipment maintenance (n = 25, 45%), access to consumable supplies (n = 21, 38%), and cost (n = 31, 55%). Fifty-two participants (93%) were interested in increasing their use of laparoscopy; the majority felt that a low-cost laparoscope (n = 52, 93%) and lift retractor for gasless laparoscopy (n = 46, 82%) would serve an unmet need in their practice.

CONCLUSIONS

While the use of laparoscopy is currently limited in COSECSA countries, there is a significant interest among surgeons to increase implementation. A low-cost, durable laparoscopic system was viewed as a potential solution to the current barriers and could improve implementation in LMICs.

The D-bar method for electrical impedance tomography-demystified

Electrical impedance tomography (EIT) is an imaging modality where a patient or object is probed using harmless electric currents. The currents are fed through electrodes placed on the surface of the target, and the data consists of voltages measured at the electrodes resulting from a linearly independent set of current injection patterns. EIT aims to recover the internal distribution of electrical conductivity inside the target. The inverse problem underlying the EIT image formation task is nonlinear and severely ill-posed, and hence sensitive to modeling errors and measurement noise. Therefore, the inversion process needs to be regularized. However, traditional variational regularization methods, based on optimization, often suffer from local minima because of nonlinearity. This is what makes regularized direct (non-iterative) methods attractive for EIT. The most developed direct EIT algorithm is the D-bar method, based on Complex Geometric Optics solutions and a nonlinear Fourier transform. Variants and recent developments of D-bar methods are reviewed, and their practical numerical implementation is explained.

Understanding Factors Governing Distribution Volume of Ethyl Cellulose-Ethanol to Optimize Ablative Therapy in the Liver

OBJECTIVE

Ethanol ablation, the injection of ethanol to induce necrosis, was originally used to treat hepatocellular carcinoma, with survival rates comparable to surgery. However, efficacy is limited due to leakage into surrounding tissue. To reduce leakage, we previously reported incorporating ethyl cellulose (EC) with ethanol as this mixture forms a gel when injected into tissue. To further develop EC-ethanol injection as an ablative therapy, the present study evaluates the extent to which salient injection parameters govern the injected fluid distribution.

METHODS

Utilizing ex vivo swine liver, injection parameters (infusion rate, EC%, infusion volume) were examined with fluorescein added to each solution. After injection, tissue samples were frozen, sectioned, and imaged.

RESULTS

While leakage was higher for ethanol and 3%EC-ethanol at a rate of 10 mL/hr compared to 1 mL/hr, leakage remained low for 6%EC-ethanol regardless of infusion rate. The impact of infusion volume and pressure were also investigated first in tissue-mimicking surrogates and then in tissue. Results indicated that there is a critical infusion pressure beyond which crack formation occurs leading to fluid leakage. At a rate of 10 mL/hr, a volume of 50 μL remained below the critical pressure.

CONCLUSIONS

Although increasing the infusion rate increases stress on the tissue and the risk of crack formation, injections of 6%EC-ethanol were localized regardless of infusion rate. To further limit leakage, multiple low-volume infusions may be employed.

SIGNIFICANCE

These results, and the experimental framework developed to obtain them, can inform optimizing EC-ethanol to treat a range of medical conditions.

Development of Algorithms for Automated Detection of Cervical Pre-Cancers With a Low-Cost, Point-of-Care, Pocket Colposcope

GOAL

In this paper, we propose methods for (1) automatic feature extraction and classification for acetic acid and Lugol's iodine cervigrams and (2) methods for combining features/diagnosis of different contrasts in cervigrams for improved performance.

METHODS

We developed algorithms to pre-process pathology-labeled cervigrams and extract simple but powerful color and textural-based features. The features were used to train a support vector machine model to classify cervigrams based on corresponding pathology for visual inspection with acetic acid, visual inspection with Lugol's iodine, and a combination of the two contrasts.

RESULTS

The proposed framework achieved a sensitivity, specificity, and accuracy of 81.3%, 78.6%, and 80.0%, respectively, when used to distinguish cervical intraepithelial neoplasia (CIN+) relative to normal and benign tissues. This is superior to the average values achieved by three expert physicians on the same data set for discriminating normal/benign cases from CIN+ (77% sensitivity, 51% specificity, and 63% accuracy).

CONCLUSION

The results suggest that utilizing simple color- and textural-based features from visual inspection with acetic acid and visual inspection with Lugol's iodine images may provide unbiased automation of cervigrams.

SIGNIFICANCE

This would enable automated, expert-level diagnosis of cervical pre-cancer at the point of care.

Portable Pocket colposcopy performs comparably to standard-of-care clinical colposcopy using acetic acid and Lugol's iodine as contrast mediators: an investigational study in Peru

OBJECTIVE

Our goal was to develop a tele-colposcopy platform for primary-care clinics to improve screening sensitivity and access. Specifically, we developed a low-cost, portable Pocket colposcope and evaluated its performance in a tertiary healthcare centre in Peru.

DESIGN AND SETTING

Images of the cervix were captured with a standard-of-care and Pocket colposcope at la Liga Contra el Cáncer in Lima, Peru.

POPULATION

Two hundred Peruvian women with abnormal cytology and/or human papillomavirus positivity were enrolled.

METHODS

Images were collected using acetic acid and Lugol's iodine as contrast agents. Biopsies were taken as per standard-of-care procedures.

MAIN OUTCOME MEASURES

After passing quality review, images from 129 women were sent to four physicians who provided a diagnosis for each image.

RESULTS

Physician interpretation of images from the two colposcopes agreed 83.1% of the time. The average sensitivity and specificity of physician interpretation compared with pathology was similar for the Pocket (sensitivity = 71.2%, specificity = 57.5%) and standard-of-care (sensitivity = 79.8%, specificity = 56.6%) colposcopes. When compared with a previous study where only acetic acid was applied to the cervix, results indicated that adding Lugol's iodine as a secondary contrast agent improved the percent agreement between colposcopes for all pathological categories by up to 8.9% and the sensitivity and specificity of physician interpretation compared with pathology by over 6.0 and 9.0%, respectively.

CONCLUSIONS

The Pocket colposcope performance was similar to that of a standard-of-care colposcope when used to identify precancerous and cancerous lesions using acetic acid and Lugol's iodine during colposcopy examinations in Peru.

TWEETABLE ABSTRACT

The Pocket colposcope performance was similar to that of a standard-of-care colposcope when identifying cervical lesions.

Robust computation in 2D absolute EIT (a-EIT) using D-bar methods with the 'exp' approximation

OBJECTIVE

Absolute images have important applications in medical electrical impedance tomography (EIT) imaging, but the traditional minimization and statistical based computations are very sensitive to modeling errors and noise. In this paper, it is demonstrated that D-bar reconstruction methods for absolute EIT are robust to such errors.

APPROACH

The effects of errors in domain shape and electrode placement on absolute images computed with 2D D-bar reconstruction algorithms are studied on experimental data.

MAIN RESULTS

It is demonstrated with tank data from several EIT systems that these methods are quite robust to such modeling errors, and furthermore the artefacts arising from such modeling errors are similar to those occurring in classic time-difference EIT imaging.

SIGNIFICANCE

This study is promising for clinical applications where absolute EIT images are desirable but previously thought impossible.

International Image Concordance Study to Compare a Point-of-Care Tampon Colposcope With a Standard-of-Care Colposcope

OBJECTIVE

Barriers to cervical cancer screening in low-resource settings include lack of accessible, high-quality services, high cost, and the need for multiple visits. To address these challenges, we developed a low-cost, intravaginal, optical cervical imaging device, the point-of-care tampon (POCkeT) colposcope and evaluated whether its performance is comparable with a standard-of-care colposcope.

MATERIALS AND METHODS

There were 2 protocols, which included 44 and 18 patients. For the first protocol, white-light cervical images were collected in vivo, blinded by device, and sent electronically to 8 physicians from high-, middle-, and low-income countries. For the second protocol, green-light images were also collected and sent electronically to the highest performing physician from the first protocol who has experience in both a high- and low-income country. For each image, physicians completed a survey assessing cervix characteristics and severity of precancerous lesions. Corresponding pathology was obtained for all image pairs.

RESULTS

For the first protocol, average percent agreement between devices was 70% across all physicians. The POCkeT and standard-of-care colposcope images had 37% and 51% agreement with pathology for high-grade squamous intraepithelial lesions (HSILs), respectively. Investigation of HSIL POCkeT images revealed decreased visibility of vascularization and lack of contrast in lesion margins. After changes were made for the second protocol, the 2 devices achieved similar agreement to pathology for HSIL lesions (55%).

CONCLUSIONS

Based on the exploratory study, physician interpretation of cervix images acquired using a portable, low-cost POCkeT colposcope was comparable to a standard-of-care colposcope.

Incorporating a Spatial Prior into Nonlinear D-Bar EIT Imaging for Complex Admittivities

Electrical Impedance Tomography (EIT) aims to recover the internal conductivity and permittivity distributions of a body from electrical measurements taken on electrodes on the surface of the body. The reconstruction task is a severely ill-posed nonlinear inverse problem that is highly sensitive to measurement noise and modeling errors. Regularized D-bar methods have shown great promise in producing noise-robust algorithms by employing a low-pass filtering of nonlinear (nonphysical) Fourier transform data specific to the EIT problem. Including prior data with the approximate locations of major organ boundaries in the scattering transform provides a means of extending the radius of the low-pass filter to include higher frequency components in the reconstruction, in particular, features that are known with high confidence. This information is additionally included in the system of D-bar equations with an independent regularization parameter from that of the extended scattering transform. In this paper, this approach is used in the 2-D D-bar method for admittivity (conductivity as well as permittivity) EIT imaging. Noise-robust reconstructions are presented for simulated EIT data on chest-shaped phantoms with a simulated pneumothorax and pleural effusion. No assumption of the pathology is used in the construction of the prior, yet the method still produces significant enhancements of the underlying pathology (pneumothorax or pleural effusion) even in the presence of strong noise.

Rapid staining and imaging of subnuclear features to differentiate between malignant and benign breast tissues at a point-of-care setting

PURPOSE

Histopathology is the clinical standard for tissue diagnosis; however, it requires tissue processing, laboratory personnel and infrastructure, and a highly trained pathologist to diagnose the tissue. Optical microscopy can provide real-time diagnosis, which could be used to inform the management of breast cancer. The goal of this work is to obtain images of tissue morphology through fluorescence microscopy and vital fluorescent stains and to develop a strategy to segment and quantify breast tissue features in order to enable automated tissue diagnosis.

METHODS

We combined acriflavine staining, fluorescence microscopy, and a technique called sparse component analysis to segment nuclei and nucleoli, which are collectively referred to as acriflavine positive features (APFs). A series of variables, which included the density, area fraction, diameter, and spacing of APFs, were quantified from images taken from clinical core needle breast biopsies and used to create a multivariate classification model. The model was developed using a training data set and validated using an independent testing data set.

RESULTS

The top performing classification model included the density and area fraction of smaller APFs (those less than 7 µm in diameter, which likely correspond to stained nucleoli).When applied to the independent testing set composed of 25 biopsy panels, the model achieved a sensitivity of 82 %, a specificity of 79 %, and an overall accuracy of 80 %.

CONCLUSIONS

These results indicate that our quantitative microscopy toolbox is a potentially viable approach for detecting the presence of malignancy in clinical core needle breast biopsies.

Structured Illumination Microscopy and a Quantitative Image Analysis for the Detection of Positive Margins in a Pre-Clinical Genetically Engineered Mouse Model of Sarcoma

Intraoperative assessment of surgical margins is critical to ensuring residual tumor does not remain in a patient. Previously, we developed a fluorescence structured illumination microscope (SIM) system with a single-shot field of view (FOV) of 2.1 × 1.6 mm (3.4 mm2) and sub-cellular resolution (4.4 μm). The goal of this study was to test the utility of this technology for the detection of residual disease in a genetically engineered mouse model of sarcoma. Primary soft tissue sarcomas were generated in the hindlimb and after the tumor was surgically removed, the relevant margin was stained with acridine orange (AO), a vital stain that brightly stains cell nuclei and fibrous tissues. The tissues were imaged with the SIM system with the primary goal of visualizing fluorescent features from tumor nuclei. Given the heterogeneity of the background tissue (presence of adipose tissue and muscle), an algorithm known as maximally stable extremal regions (MSER) was optimized and applied to the images to specifically segment nuclear features. A logistic regression model was used to classify a tissue site as positive or negative by calculating area fraction and shape of the segmented features that were present and the resulting receiver operator curve (ROC) was generated by varying the probability threshold. Based on the ROC curves, the model was able to classify tumor and normal tissue with 77% sensitivity and 81% specificity (Youden's index). For an unbiased measure of the model performance, it was applied to a separate validation dataset that resulted in 73% sensitivity and 80% specificity. When this approach was applied to representative whole margins, for a tumor probability threshold of 50%, only 1.2% of all regions from the negative margin exceeded this threshold, while over 14.8% of all regions from the positive margin exceeded this threshold.

A Fluorescence-Guided Laser Ablation System for Removal of Residual Cancer in a Mouse Model of Soft Tissue Sarcoma

The treatment of soft tissue sarcoma (STS) generally involves tumor excision with a wide margin. Although advances in fluorescence imaging make real-time detection of cancer possible, removal is limited by the precision of the human eye and hand. Here, we describe a novel pulsed Nd:YAG laser ablation system that, when used in conjunction with a previously described molecular imaging system, can identify and ablate cancer in vivo. Mice with primary STS were injected with the protease-activatable probe LUM015 to label tumors. Resected tissues from the mice were then imaged and treated with the laser using the paired fluorescence-imaging/ laser ablation device, generating ablation clefts with sub-millimeter precision and minimal underlying tissue damage. Laser ablation was guided by fluorescence to target tumor tissues, avoiding normal structures. The selective ablation of tumor implants in vivo improved recurrence-free survival after tumor resection in a cohort of 14 mice compared to 12 mice that received no ablative therapy. This prototype system has the potential to be modified so that it can be used during surgery to improve recurrence-free survival in patients with cancer.

Micro-anatomical quantitative optical imaging: toward automated assessment of breast tissues

INTRODUCTION

Pathologists currently diagnose breast lesions through histologic assessment, which requires fixation and tissue preparation. The diagnostic criteria used to classify breast lesions are qualitative and subjective, and inter-observer discordance has been shown to be a significant challenge in the diagnosis of selected breast lesions, particularly for borderline proliferative lesions. Thus, there is an opportunity to develop tools to rapidly visualize and quantitatively interpret breast tissue morphology for a variety of clinical applications.

METHODS

Toward this end, we acquired images of freshly excised breast tissue specimens from a total of 34 patients using confocal fluorescence microscopy and proflavine as a topical stain. We developed computerized algorithms to segment and quantify nuclear and ductal parameters that characterize breast architectural features. A total of 33 parameters were evaluated and used as input to develop a decision tree model to classify benign and malignant breast tissue. Benign features were classified in tissue specimens acquired from 30 patients and malignant features were classified in specimens from 22 patients.

RESULTS

The decision tree model that achieved the highest accuracy for distinguishing between benign and malignant breast features used the following parameters: standard deviation of inter-nuclear distance and number of duct lumens. The model achieved 81 % sensitivity and 93 % specificity, corresponding to an area under the curve of 0.93 and an overall accuracy of 90 %. The model classified IDC and DCIS with 92 % and 96 % accuracy, respectively. The cross-validated model achieved 75 % sensitivity and 93 % specificity and an overall accuracy of 88 %.

CONCLUSIONS

These results suggest that proflavine staining and confocal fluorescence microscopy combined with image analysis strategies to segment morphological features could potentially be used to quantitatively diagnose freshly obtained breast tissue at the point of care without the need for tissue preparation.

A quantitative microscopic approach to predict local recurrence based on in vivo intraoperative imaging of sarcoma tumor margins

The goal of resection of soft tissue sarcomas located in the extremity is to preserve limb function while completely excising the tumor with a margin of normal tissue. With surgery alone, one-third of patients with soft tissue sarcoma of the extremity will have local recurrence due to microscopic residual disease in the tumor bed. Currently, a limited number of intraoperative pathology-based techniques are used to assess margin status; however, few have been widely adopted due to sampling error and time constraints. To aid in intraoperative diagnosis, we developed a quantitative optical microscopy toolbox, which includes acriflavine staining, fluorescence microscopy, and analytic techniques called sparse component analysis and circle transform to yield quantitative diagnosis of tumor margins. A series of variables were quantified from images of resected primary sarcomas and used to optimize a multivariate model. The sensitivity and specificity for differentiating positive from negative ex vivo resected tumor margins was 82 and 75%. The utility of this approach was tested by imaging the in vivo tumor cavities from 34 mice after resection of a sarcoma with local recurrence as a bench mark. When applied prospectively to images from the tumor cavity, the sensitivity and specificity for differentiating local recurrence was 78 and 82%. For comparison, if pathology was used to predict local recurrence in this data set, it would achieve a sensitivity of 29% and a specificity of 71%. These results indicate a robust approach for detecting microscopic residual disease, which is an effective predictor of local recurrence.

Optimization of a widefield structured illumination microscope for non-destructive assessment and quantification of nuclear features in tumor margins of a primary mouse model of sarcoma

Cancer is associated with specific cellular morphological changes, such as increased nuclear size and crowding from rapidly proliferating cells. In situ tissue imaging using fluorescent stains may be useful for intraoperative detection of residual cancer in surgical tumor margins. We developed a widefield fluorescence structured illumination microscope (SIM) system with a single-shot FOV of 2.1×1.6 mm (3.4 mm²) and sub-cellular resolution (4.4 µm). The objectives of this work were to measure the relationship between illumination pattern frequency and optical sectioning strength and signal-to-noise ratio in turbid (i.e. thick) samples for selection of the optimum frequency, and to determine feasibility for detecting residual cancer on tumor resection margins, using a genetically engineered primary mouse model of sarcoma. The SIM system was tested in tissue mimicking solid phantoms with various scattering levels to determine impact of both turbidity and illumination frequency on two SIM metrics, optical section thickness and modulation depth. To demonstrate preclinical feasibility, ex vivo 50 µm frozen sections and fresh intact thick tissue samples excised from a primary mouse model of sarcoma were stained with acridine orange, which stains cell nuclei, skeletal muscle, and collagenous stroma. The cell nuclei were segmented using a high-pass filter algorithm, which allowed quantification of nuclear density. The results showed that the optimal illumination frequency was 31.7 µm⁻¹ used in conjunction with a 4×0.1 NA objective ( = 0.165). This yielded an optical section thickness of 128 µm and an 8.9×contrast enhancement over uniform illumination. We successfully demonstrated the ability to resolve cell nuclei in situ achieved via SIM, which allowed segmentation of nuclei from heterogeneous tissues in the presence of considerable background fluorescence. Specifically, we demonstrate that optical sectioning of fresh intact thick tissues performed equivalently in regards to nuclear density quantification, to physical frozen sectioning and standard microscopy.

Quantitative Segmentation of Fluorescence Microscopy Images of Heterogeneous Tissue: Application to the Detection of Residual Disease in Tumor Margins

Purpose

To develop a robust tool for quantitative in situ pathology that allows visualization of heterogeneous tissue morphology and segmentation and quantification of image features.

Materials and Methods

Tissue excised from a genetically engineered mouse model of sarcoma was imaged using a subcellular resolution microendoscope after topical application of a fluorescent anatomical contrast agent: acriflavine. An algorithm based on sparse component analysis (SCA) and the circle transform (CT) was developed for image segmentation and quantification of distinct tissue types. The accuracy of our approach was quantified through simulations of tumor and muscle images. Specifically, tumor, muscle, and tumor+muscle tissue images were simulated because these tissue types were most commonly observed in sarcoma margins. Simulations were based on tissue characteristics observed in pathology slides. The potential clinical utility of our approach was evaluated by imaging excised margins and the tumor bed in a cohort of mice after surgical resection of sarcoma.

Results

Simulation experiments revealed that SCA+CT achieved the lowest errors for larger nuclear sizes and for higher contrast ratios (nuclei intensity/background intensity). For imaging of tumor margins, SCA+CT effectively isolated nuclei from tumor, muscle, adipose, and tumor+muscle tissue types. Differences in density were correctly identified with SCA+CT in a cohort of ex vivo and in vivo images, thus illustrating the diagnostic potential of our approach.

Conclusion

The combination of a subcellular-resolution microendoscope, acriflavine staining, and SCA+CT can be used to accurately isolate nuclei and quantify their density in anatomical images of heterogeneous tissue.

A direct D-bar reconstruction algorithm for recovering a complex conductivity in 2-D

A direct reconstruction algorithm for complex conductivities in W^2,∞ (Ω), where Ω is a bounded, simply connected Lipschitz domain in ℝ², is presented. The framework is based on the uniqueness proof by Francini [Inverse Problems 20 2000], but equations relating the Dirichlet-to-Neumann to the scattering transform and the exponentially growing solutions are not present in that work, and are derived here. The algorithm constitutes the first D-bar method for the reconstruction of conductivities and permittivities in two dimensions. Reconstructions of numerically simulated chest phantoms with discontinuities at the organ boundaries are included.

Initial description of the human NLRP3 promoter

Mutations in NLRP3 (CIAS1) are identified in a continuum of related inflammatory disorders, known as cryopyrinopathies since NLRP3 codes for the protein cryopyrin. Approximately 40% of patients with classic presentation lack mutations in the coding region of NLRP3 suggesting heterogeneity or epigenetic factors. Cryopyrin is a key regulator of proinflammatory cytokine release. Therefore, variations in the NLRP3 promoter sequence may have effects on disease state in patients with cryopyrinopathies and other inflammatory diseases. In this report, we confirmed three 5'-untranslated region splice forms with two separate transcriptional start sites, and identified potential promoter regions and six new DNA promoter variants. One variant is unique to a mutation negative cryopyrinopathy patient and increases in vitro gene expression. Additional studies can now be performed to further characterize the NLRP3 promoter and sequence variants, which will lead to better understanding of the regulation of NLRP3 expression and its role in disease.

Reconstructions of conductive and insulating targets using the D-bar method on an elliptical domain

The D-bar algorithm based on A Nachman's 2D global uniqueness proof for the inverse conductivity problem (Nachman 1996 Ann. Math. 143 71-96) is implemented on an elliptical domain. The scattering transform is computed on an ellipse and the complete electrode model (CEM) for the forward problem is computed with the finite element method (FEM) in order to obtain static conductivity reconstructions of conductive and insulating targets in a saline-filled tank. It is demonstrated that the spatial artifacts in the image are significantly reduced when the domain is properly modeled in the reconstruction, as opposed to being modeled as a disk.

Imaging cardiac activity by the D-bar method for electrical impedance tomography

A practical D-bar algorithm for reconstructing conductivity changes from EIT data taken on electrodes in a 2D geometry is described. The algorithm is based on the global uniqueness proof of Nachman (1996 Ann. Math. 143 71-96) for the 2D inverse conductivity problem. Results are shown for reconstructions from data collected on electrodes placed around the circumference of a human chest to reconstruct a 2D cross-section of the torso. The images show changes in conductivity during a cardiac cycle.

Cross-species comparison of Drosophila male accessory gland protein genes

Drosophila melanogaster males transfer seminal fluid proteins along with sperm during mating. Among these proteins, ACPs (Accessory gland proteins) from the male's accessory gland induce behavioral, physiological, and life span reduction in mated females and mediate sperm storage and utilization. A previous evolutionary EST screen in D. simulans identified partial cDNAs for 57 new candidate ACPs. Here we report the annotation and confirmation of the corresponding Acp genes in D. melanogaster. Of 57 new candidate Acp genes previously reported in D. melanogaster, 34 conform to our more stringent criteria for encoding putative male accessory gland extracellular proteins, thus bringing the total number of ACPs identified to 52 (34 plus 18 previously identified). This comprehensive set of Acp genes allows us to dissect the patterns of evolutionary change in a suite of proteins from a single male-specific reproductive tissue. We used sequence-based analysis to examine codon bias, gene duplications, and levels of divergence (via dN/dS values and ortholog detection) of the 52 D. melanogaster ACPs in D. simulans, D. yakuba, and D. pseudoobscura. We show that 58% of the 52 D. melanogaster Acp genes are detectable in D. pseudoobscura. Sequence comparisons of ACPs shared and not shared between D. melanogaster and D. pseudoobscura show that there are separate classes undergoing distinctly dissimilar evolutionary dynamics.

Detection and mapping of quantitative trait loci that determine responsiveness of mice to nitrous oxide antinociception

Exposure to 70% N(2)O evokes a robust antinociceptive effect in C57BL/6 (B6) but not in DBA/2 (D2) inbred mice. This study was conducted to identify quantitative trait loci (QTL) in the mouse genome that might determine responsiveness to N(2)O. Offspring from the F(2) generation bred from B6 and D2 progenitors exhibited a broad range of responsiveness to N(2)O antinociception as determined by the acetic acid-induced abdominal constriction test. QTL analysis was then used to dissect this continuous trait distribution into component loci, and to map them to broad chromosomal regions. To this end, 24 spleens were collected from each of the following four groups: male and female F(2) mice responding to 70% N(2)O in oxygen with 100% response (high-responders); and male and female F(2) mice responding with 0% response (low-responders). Genomic DNA was extracted from the spleens and genotyped with simple sequence length polymorphism MapPairs markers. Findings were combined with findings from the earlier QTL analysis from BXD recombinant inbred mice [Brain Res 725 (1996) 23]. Combined results revealed two significant QTL that influence responsiveness to nitrous oxide on proximal chromosome 2 and distal chromosome 5, and one suggestive QTL on midchromosome 18. The chromosome 2 QTL was evident only in males. A significant interaction was found between a locus on chromosome 6 and another on chromosome 13 with a substantial effect on N(2)O antinociception.

Mutation of a new gene encoding a putative pyrin-like protein causes familial cold autoinflammatory syndrome and Muckle-Wells syndrome

Familial cold autoinflammatory syndrome (FCAS, MIM 120100), commonly known as familial cold urticaria (FCU), is an autosomal-dominant systemic inflammatory disease characterized by intermittent episodes of rash, arthralgia, fever and conjunctivitis after generalized exposure to cold. FCAS was previously mapped to a 10-cM region on chromosome 1q44 (refs. 5,6). Muckle-Wells syndrome (MWS; MIM 191900), which also maps to chromosome 1q44, is an autosomal-dominant periodic fever syndrome with a similar phenotype except that symptoms are not precipitated by cold exposure and that sensorineural hearing loss is frequently also present. To identify the genes for FCAS and MWS, we screened exons in the 1q44 region for mutations by direct sequencing of genomic DNA from affected individuals and controls. This resulted in the identification of four distinct mutations in a gene that segregated with the disorder in three families with FCAS and one family with MWS. This gene, called CIAS1, is expressed in peripheral blood leukocytes and encodes a protein with a pyrin domain, a nucleotide-binding site (NBS, NACHT subfamily) domain and a leucine-rich repeat (LRR) motif region, suggesting a role in the regulation of inflammation and apoptosis.

Mutation of a new gene encoding a putative pyrin-like protein causes familial cold autoinflammatory syndrome and Muckle-Wells syndrome

Familial cold autoinflammatory syndrome (FCAS, MIM 120100), commonly known as familial cold urticaria (FCU), is an autosomal-dominant systemic inflammatory disease characterized by intermittent episodes of rash, arthralgia, fever and conjunctivitis after generalized exposure to cold. FCAS was previously mapped to a 10-cM region on chromosome 1q44 (refs. 5,6). Muckle-Wells syndrome (MWS; MIM 191900), which also maps to chromosome 1q44, is an autosomal-dominant periodic fever syndrome with a similar phenotype except that symptoms are not precipitated by cold exposure and that sensorineural hearing loss is frequently also present. To identify the genes for FCAS and MWS, we screened exons in the 1q44 region for mutations by direct sequencing of genomic DNA from affected individuals and controls. This resulted in the identification of four distinct mutations in a gene that segregated with the disorder in three families with FCAS and one family with MWS. This gene, called CIAS1, is expressed in peripheral blood leukocytes and encodes a protein with a pyrin domain, a nucleotide-binding site (NBS, NACHT subfamily) domain and a leucine-rich repeat (LRR) motif region, suggesting a role in the regulation of inflammation and apoptosis.

Reconstruction of conductivity changes due to ventilation and perfusion from EIT data collected on a rectangular electrode array

In this paper we demonstrate that conductivity changes caused by ventilation and perfusion in a human subject can be reconstructed from electrical impedance tomography data collected on a rectangular array of electrodes placed on a subject's chest. Currents are applied on the electrodes and the resulting voltages on the electrodes are measured. A 3D reconstruction algorithm is used to reconstruct the conductivity distribution in the region beneath the array. Time traces of the reconstructed conductivity distribution demonstrate the detected changes in conductivity due to ventilation and perfusion.

Antagonism of nitrous oxide antinociception in mice by intrathecally administered antisera to endogenous opioid peptides

Previously it was demonstrated that nitrous oxide antinociception in the mouse abdominal constriction test is mediated by kappa-opioid receptors. Since nitrous oxide is thought to cause the neuronal release of endogenous opioid peptide to stimulate opioid receptors, this study was designed to identify the opioid peptides involved, especially in the spinal cord, by determining whether nitrous oxide antinociception can be differentially inhibited by intrathecally (i. t.) administered antisera to different opioid peptides. Male NIH Swiss mice were pretreated i.t. with rabbit antisera to opioid peptides then exposed 24 h later to one of three different concentrations of nitrous oxide in oxygen. Dose-response curves constructed from the data indicated that the antinociceptive effect of nitrous oxide was significantly antagonized by antisera to various dynorphins (DYNs) and methionine-enkephalin (ME), but not by antiserum to beta-endorphin (beta-EP). The AD(50) values for nitrous oxide antinociception were significantly elevated by antisera to DYNs and ME but not beta-EP. These findings of this study support the hypothesis that nitrous oxide antinociception in the mouse abdominal constriction test involves the neuronal release of DYN and ME in the spinal cord.

A reconstruction algorithm for electrical impedance tomography data collected on rectangular electrode arrays

A three-dimensional reconstruction algorithm in electrical impedance imaging is presented for determining the conductivity distribution beneath the surface of a medium, given surface voltage data measured on a rectangular array of electrodes. Such an electrode configuration may be desirable for using electrical impedence tomography to detect tumors in the human breast. The algorithm is based on linearizing the conductivity about a constant value. Here, we describe a simple implementation of the algorithm on a four-electrode--by-four-electrode array and the reconstructions obtained from numerical and experimental tank data. The results demonstrate significantly better spatial resolution in the plane of the electrodes than with respect to depth.

Returning to work through job accommodation: a case study

1. As more people live longer and more active lives the likelihood of experiencing a disability during one's career increases. Although the unemployment rate among people with disabilities is high, workers with disabilities are becoming more common. 2. Effective job accommodation costs only a small fraction of the hundreds of thousands of dollars that would otherwise be paid out in disability benefits and insurance premiums, or wasted in litigation. 3. Job accommodation planning should begin as early as possible in the disability process and include the active involvement of the individual with the disability and appropriate clinicians, as well as the supervisor and coworkers. 4. Successful accommodation is the result of teamwork, The occupational health professional is often the coordinator of a number of internal and external resources in the job accommodation process. Tools are available for sharing information among all those involved in the accommodation process, without compromise of confidential medical or business information.

Assistive technology and universal design in the workplace

The terms assistive technology and universal design challenge designers, engineers, and technologists to consider the broadest possible use for the things they create, to make assistive technology as useful to nondisabled persons as to those with disabilities, and to make the products and environments we design as usable as possible for everyone, regardless of age or ability.

Nitrous oxide antinociception in BXD recombinant inbred mouse strains and identification of quantitative trait loci

Among inbred mouse strains, DBA/2 mice are unique because of their poor responsiveness to nitrous oxide (N2O) antinociception. As a first step towards identifying candidate genes involved in determining antinociceptive responsiveness to N2O, male mice from the DBA/2 strain, the more responsive C57BL/6 strain, their B6D2F1 offspring, and 22 BXD recombinant inbred (RI) strains derived from DBA/2 and C57BL/6 mice were exposed to N2O and evaluated using the acetic acid abdominal constriction test. When exposed to 70% N2O, C57BL/6, DBA/2 and B6D2F1 mice exhibited antinociceptive responses of 78, 22 and 55%, respectively. The BXD RI strains demonstrated varying degrees of responsiveness to N2O. Cluster analysis revealed one cluster of 16 strains approximating the C57BL/6 progenitor (61.9-100% antinociceptive response to 70% N2O) and another of six strains around the DBA/2 progenitor (9.1-40% antinociceptive response to 70% N2O). The robust strain differences permitted screening the strain means with 1492 marker loci previously mapped in BXD RI strains. Using a QTL analysis specifically tailored to existing mouse RI strains, we found associations at the 0.01 level on seven chromosomes with the most promising marker loci being Il2ra, Hbb, Hmg1rs7 and Gsl5 on chromosomes 2, 7, 16 and 19, respectively (P < 0.002).

Method to derive ocean absorption coefficients from remote-sensing reflectance

A method to derive in-water absorption coefficients from total remote-sensing reflectance (ratio of the upwelling radiance to the downwelling irradiance above the surface) analytically is presented. For measurements made in the Gulf of Mexico and Monterey Bay, with concentrations of chlorophyll-a ranging from 0.07 to 50 mg/m(3), comparisons are made for the total absorption coefficients derived with the suggested method and those derived with diffuse attenuation coefficients. For these coastal to open-ocean waters, including regions of upwelling and the Loop Current, the results are as follows: at 440 nm the difference between the two methods is 13.0% (r(2) = 0.96) for total absorption coefficients ranging from 0.02 to 2.0 m(-1); at 488 nm the difference is 14.5% (r(2) = 0.97); and at 550 nm the difference is 13.6% (r(2) = 0.96). The results indicate that the method presented works very well for retrieval of in-water absorption coefficients exclusively from remotely measured signals, and that this method has a wide range of potential applications in oceanic remote sensing.

Involvement of nitric oxide in intracerebroventricular beta-endorphin-induced neuronal release of methionine-enkephalin

Previous work has suggested that the antinociceptive effect of nitrous oxide (N2O) in rats is mediated, at least in part, by beta-endorphin (beta-EP) and that centrally administered beta-EP stimulates release of methionine-enkephalin (ME) in the rat spinal cord. Since inhibition of central nitric oxide (NO) production has been found to suppress N2O antinociception, we examined the possible involvement of NO in the release of spinal cord ME by i.c.v. beta-EP. Urethane-anesthetized, male Sprague-Dawley rats were intrathecally (i.t.) perfused with artificial cerebrospinal fluid (aCSF) and fractions of perfusate were assayed for immunoreactive (i.r.) ME. The beta-EP-induced increase in ME concentration in the i.t. perfusate was significantly suppressed by perfusing the animal with aCSF containing 100 microM L-NG-nitro arginine (L-NOARG), an inhibitor of NO synthase (NOS). The further addition of 50 microM L-arginine (L-ARG), but not D-arginine (D-ARG), to the aCSF reversed the suppression of the ME change by L-NOARG. However, the potency of L-ARG decreased with increasing concentrations of L-ARG. On the other hand, increasing the concentration of L-NOARG in the aCSF to 250 microM failed to produce a greater suppression of the beta-EP-induced increase in ME. These findings suggest that NO may mediate the beta-EP-induced release of ME in the spinal cord and that interference with this mechanism might be an explanation for the antagonism of N2O antinociception in rats by NOS inhibitors.

Dose-dependent antagonism and potentiation of nitrous oxide antinociception by naloxone in mice

Administration of the anesthetic gas nitrous oxide (N2O) evoked a concentration-dependent antinociceptive effect in mice as assessed by the abdominal constriction test. Depending on the dose and route of pretreatment with the opioid receptor blocker naloxone, the N2O drug effect was either antagonized or potentiated. After s.c. pretreatment with milligram per kilogram doses of naloxone, dose-related antagonism occurred; picogram per kilogram doses potentiated N2O-induced antinociception. The i.c.v. pretreatment with microgram quantities of naloxone also antagonized N2O antinociception in a dose-related fashion; i.c.v. pretreatment with femtogram doses was without effect. On the other hand, intrathecal (i.t.) pretreatment with femtogram quantities of naloxone potentiated N2O antinociception; i.t. pretreatment with microgram quantities continued to antagonize the antinociceptive effect. The same pattern of interaction was observed in mice challenged with the kappa opioid analgesic drug trans (+- 3,4-dichlow-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl] benzeneacetamide methane sulfonate (U-50, 488H) after s.c., i.c.v. or i.t. pretreatments with high and low doses of naloxone. These results 1) demonstrate further similarities in the opioid receptor mediation of N2O and U-50, 488H antinociceptive effects and also 2) support the concept of high-affinity spinal opioid receptors, whose blockade by s.c.- or i.t.- but not i.c.v.-administered low-dose naloxone can potentiate the antinociceptive effects of both N2O and U-50,488H. These findings suggest that the antinociceptive effect of N2O might be modulated by a descending opioid system that inhibits analgesia.

Strain-dependent differences in responsiveness of mice to nitrous oxide (N2O) antinociception

N2O antinociception was assessed in eight inbred and two outbred mouse strains. Results indicated the following order of responsiveness among the 10 strains: A/J (most sensitive), C57BL/6ByJ, C57BL/6J, BALB/cByJ, C3H/HeJ, Swiss-Webster, CXBK/ByJ, ICR, CBA/J and DBA/2J (least sensitive). These results demonstrate significant strain-dependent differences in antinociceptive responsiveness to N2O. The weak antinociceptive response to N2O in the DBA/2J strain, which is sensitive to morphine and U-50, 488H, indicates some underlying neurobiological difference in the DBA/2J mouse that imparts resistance to N2O. The responsiveness of CXBK/ByJ mice to N2O indicates that mu-opioid receptors may not play an important role in N2O antinociception in mice.

Contrasting influences of 5-hydroxytryptamine receptors in nitrous oxide antinociception in mice

5-Hydroxytryptamine (5-HT) mechanisms may play a role in opioid-mediated antinociception. Since opioid mechanisms have been implicated in nitrous oxide antinociception, this study was conducted to determine the possible role of 5-HT receptors in nitrous oxide antinociception. Male Swiss Webster mice were pretreated with one of two 5-HT receptor blockers and then tested in the acetic acid abdominal constriction test for their antinociceptive response to nitrous oxide, the kappa-opioid agonist U-50,488H, or the mu-opioid agonist sufentanil. Results indicate that the 5-HT3 receptor blocker ICS-205,930 antagonized both nitrous oxide and U-50,488H effects but not that of sufentanil. Mianserin, a 5-HT1c/5-HT2 receptor blocker, effects but not that of sufentanil. Mianserin, a 5-HT1c/5-HT2 receptor blocker, potentiated effects of both nitrous oxide and U-50,488H but not that of sufentanil. These findings show similarities in nitrous oxide and U-50,488H antinociception and further support our hypothesis that nitrous oxide works through central kappa-opioid mechanisms in mice. The results also suggest different roles for 5-HT receptor subtypes in mediating or modulating the antinociceptive effect of nitrous oxide.

Nimbus-7 Coastal Zone Color Scanner: System Description and Initial Imagery

The Coastal Zone Color Scanner (CZCS) on Nimbus-7, launched in October 1978, is the only sensor in orbit that is specifically designed to study living marine resources. The initial imagery confirms that CZCS data can be processed to a level that reveals subtle variations in the concentration of phytoplankton pigments. This development has potential applications for the study of large-scale patchiness in phytoplankton distributions, the evolution of spring blooms, water mass boundaries, and mesoscale circulation patterns.

Phytoplankton Pigments from the Nimbus-7 Coastal Zone Color Scanner: Comparisons with Surface Measurements

The removal of atmospheric effects from Nimbus-7 Coastal Zone Color Scanner (CZCS) images reveals eddy-like ocean turbidity patterns not apparent in the original calibrated images. Comparisons of the phytoplankton pigment concentrations derived from the corrected CZCS radiances with surface measurements agree to within less than 0.5 log C, where C is the sum of the concentrations of chlorophyll a plus phaeopigments a (in milligrams per cubic meter).