A new approach for assessing early osteoarthritis in the rat.

Several animal models have been developed to investigate osteoarthritis and potential disease-modifying therapeutics. However, early disease data from these models are limited by the resolution of current imaging modalities. In this in-vitro study, an optical coherence tomography (OCT) system with an axial resolution of 15 micro m was used to track sequential changes in osteoarthritic rat knees. Osteoarthritis was induced via transection of the medial collateral ligament and an artificial full thickness meniscal tear. Imaging occurred at one, two, and three weeks after surgery. OCT successfully detected early signs of osteoarthritic change, including alteration of the cartilage surface and disruption of the bone-cartilage interface. This study demonstrates that OCT, along with the induction of mechanical injury, provides an excellent model for monitoring the sequential changes of osteoarthritis.

New technology for assessing microstructural components of tendons and ligaments.

This study investigated the ability of optical coherence tomography (OCT), a recently developed technology with micron-scale resolution, to assess the microstructure of tendons and ligaments. In vitro structural- and polarization-sensitive OCT was performed on human ACL, Achilles tendon, and biceps tendon (obtained postmortem). Histology was performed on all imaged samples and compared to the corresponding OCT data. OCT images correlated well with histology. Most importantly, through polarization-sensitive OCT, the collagen in normal tissue was easily distinguished from the surrounding, supportive tissue due to the birefringent properties of organized collagen. Since the integrity of collagen is an important indicator of structural stability and pathologic state, the ability of OCT to assess collagen could be a powerful diagnostic tool in assessing tendon and ligament properties.

Real-time optical coherence tomography for minimally invasive imaging of prostate ablation.

OBJECTIVE: Numerous ablation techniques have been developed to alleviate urethral obstruction and improve urodynamics in benign prostatic hyperplasia. Most techniques, however, rely on visual observation of surface changes for ablation end points. The feasibility of using real-time optical coherence tomography (OCT) for minimally invasive imaging to guide and monitor prostate resection is demonstrated with representative techniques of laser and radiofrequency ablation. Empiric comparisons of ablation dynamics are made, and the use of OCT as a high-resolution, subsurface modality for image guidance is evaluated. MATERIALS AND METHODS: Optical coherence tomography is a high-resolution, high-speed near-infrared imaging technique analogous to ultrasound imaging, except that reflections of light are detected rather than sound. High-speed OCT is used to image the dynamic process of laser and radiofrequency ablation of in vitro human prostate tissue. OCT images of ablation sites are compared with corresponding histology. RESULTS: Based on comparisons between OCT images and corresponding histology, OCT imaged transurethral prostate tissue morphology, including urethral sinuses and submucosal glands. Real-time OCT imaging provided rapid feedback and control of ablation dynamics. The compact and portable OCT technology is amenable to minimally invasive beam-delivery devices. CONCLUSIONS: Optical coherence tomography offers a minimally invasive means of assessing transurethral prostate morphology. Real-time OCT has the potential to provide image guidance of prostate resection for many of the existing surgical treatments directed at alleviating urethral obstruction associated with benign prostatic hyperplasia.

High-resolution optical coherence tomography-guided laser ablation of surgical tissue.

BACKGROUND: Optical coherence tomography (OCT) is a compact high-speed imaging technology which uses infrared light to acquire cross-sectional images of tissue on the micrometer scale. Because OCT images are based on the optical backscattering properties of tissue, changes in tissue optical properties due to surgical laser ablation should be detectable using this technique. In this work, we examine the feasibility of using real-time OCT imaging to guide the placement and observe the dynamics of surgical laser ablation in a variety of tissue types. MATERIALS AND METHODS: More than 65 sites on five ex vivo rat organ tissue types were imaged at eight frames per second before, during, and after laser ablation. Ablation was performed with a coincident continuous wave argon laser operating at 514-nm wavelength and varying exposure powers and durations. Following imaging, tissue registration was achieved using microinjections of dye followed by routine histologic processing to confirm the morphology of the ablation site. RESULTS: High-speed OCT imaging at eight frames per second permitted rapid tissue orientation and guided ablation in numerous organ specimens. Acquisition rates were fast enough to capture dynamic changes in optical backscatter which corresponded to thermal tissue damage during laser ablation. CONCLUSIONS: The ability of high-resolution high-speed OCT to guide laser ablation and image the dynamic changes suggests a role in image-guided surgical procedures, such as the ablation of neoplasms. Future in vivo studies are necessary to demonstrate performance intraoperatively.

High resolution imaging of normal and osteoarthritic cartilage with optical coherence tomography.

OBJECTIVE: We describe optical coherence tomography (OCT), a high resolution micron scale imaging technology, for assessment of osteoarthritic articular cartilage microstructure. OCT is analogous to ultrasound, measuring the intensity of backreflected infrared light rather than acoustical waves. METHODS: OCT imaging was performed on over 100 sites on 20 normal and osteoarthritic cartilage specimens in vitro. RESULTS: Microstructures that were identified included fibrillations, fibrosis, cartilage thickness, and new bone growth at resolutions between 5 and 15 microm. In addition, the polarization sensitivity of imaging suggested a diagnostic role of polarization spectroscopy. CONCLUSION: OCT represents an attractive new technology for intraarticular imaging due to its high resolution (greater than any available clinical technology), ability to be integrated into small arthroscopes, compact portable design, and relatively low cost.

High resolution imaging of transitional cell carcinoma with optical coherence tomography: feasibility for the evaluation of bladder pathology.

Significant challenges regarding patient morbidity and mortality remain in the management of transitional cell carcinoma (TCC). Among the most important of these challenges is the inability to identify early neoplastic changes and to assess the degree of tumour invasion into the bladder wall in vivo. Optical coherence tomography (OCT) has been recently developed to provide in situ, high resolution, catheter/endoscope based imaging. This study explored the feasibility of OCT for the evaluation of bladder pathology. Both in vitro and in vivo studies were performed. In vitro imaging of pathological human bladder was performed and compared with normal specimens and histopathology. In vivo imaging of normal rabbit bladder was also performed with our current catheter/endoscope based systems. In the in vitro studies, OCT was able to delineate normal microstructure of the bladder, such as the mucosa, submucosa and muscularis layers. This was in contrast to specimens of invasive carcinoma, where a disruption of the normal bladder wall architecture was seen. The in vivo experiment demonstrated current limitations of the catheter/endoscope based systems and provided valuable information for developing an improved system for bladder imaging. The ability of OCT to delineate microstructure of the bladder wall suggests feasibility for endoscopic based imaging. In particular, there is a potential role envisioned for OCT in the management of TCC, identifying pre-malignant states and the depth of tumour invasion.

Influence of androgen on the GnRH-stimulated secretion and biosynthesis of gonadotropins in the pituitary of juvenile female bullfrogs, Rana catesbeiana.

The influence of androgen on pituitary sensitivity to gonadotropin-releasing hormone (GnRH) was investigated in juvenile female bullfrogs. Newly metamorphosed bullfrogs were treated in vivo for 7 days or their pituitaries were treated in vitro for 24 hr with 5 alpha-dihydrotestosterone (DHT). Pituitary sensitivity to GnRH was assessed by incubating glands with 100 ng/ml GnRH. The secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) was quantified by separate radioimmunoassays. Gth biosynthesis was quantified using immunoprecipitation to measure the incorporation of [35S]methionine. Prior exposure to DHT, in vitro or in vivo, significantly elevated the GnRH-induced secretion of LH and FSH. However, DHT had a differential influence on the two gonadotropins; both the basal and the GnRH-induced secretion of LH was enhanced, whereas only the GnRH-induced secretion of FSH was elevated. DHT did not significantly alter Gth biosynthesis. Treating older frogs (5 months postmetamorphic) in vivo with DHT (for 7 days) combined with a GnRH agonist (GnRHa) for 3 days enhanced the GnRH-stimulated Gth biosynthesis compared to treatment with either DHT or GnRHa alone. Therefore, while DHT may act on the pituitary to enhance gonadotropin secretion in response to GnRH, this action does not result in a concomitant increase in Gth biosynthesis. Juvenile female bullfrogs may require an increase in both GnRH and DHT in order to stimulate Gth biosynthesis.

Further studies on the influence of GnRH on the biosynthesis of gonadotropins in female frogs (Rana pipiens).

To further investigate the action of gonadotropin-releasing hormone (GnRH) on pituitaries of female frogs (Rana pipiens), gonadotropin (Gth) secretion and synthesis was measured following either the in vivo or in vitro exposure to GnRH. Treating frogs with a GnRH-agonist (GnRHa) in vivo for either 2 or 5 days led to an elevation in plasma Gth compared to that of saline-injected controls. In general, the pattern of Gth secretion in vitro paralleled changes observed in their plasma levels. GnRHa-treated frogs also had depressed pituitary content of Gth as compared to controls. Pituitaries from frogs treated with GnRHa for 5 days had higher levels of Gth synthesis than those of controls; however Gth synthesis in females treated with GnRHa for only 2 days was not elevated. After 30 hr of continuous exposure to 100 ng/ml GnRH in vitro, glands from females secreted markedly higher levels of LN and FSH than glands not exposed to the secretagogue. The levels of LH and FSH contained within pituitaries exposed to GnRH were significantly less than those of control glands. Prolonged exposure to GnRH elevated both the secretion of radiolabeled Gth as well as increased the total synthesis of Gth (compared to those of controls). These results indicate that GnRH can stimulate the biosynthesis of Gth in pituitaries of female frogs; however these results differ from those previously obtained with males. It appears that female glands require a much longer duration of GnRH stimulation than males before Gth synthesis is elevated.

In vitro exposure of frog (Rana pipiens) pituitaries to gonadotropin-releasing hormone results in a persistent stimulation of gonadotropin biosynthesis.

To further investigate the action of gonadotropin-releasing hormone (GnRH) on gonadotropin (Gth) secretion and synthesis, pituitaries from frogs, Rana pipiens, were incubated in the presence or absence of 100 ng/ml GnRH for 12 h. GnRH was then removed from the medium and glands were labeled with 35S-methionine either 12, 24, or 36 h after the conclusion of GnRH exposure. Immunoassayable LH and FSH (iLH and iFSH; both labeled and nonlabeled hormone) were determined by separate radioimmunoassays. Newly synthesized (radiolabeled) Gth was quantified by immunoprecipitation. When GnRH was present in the medium, it stimulated the secretion of both iLH and iFSH (compared to unexposed glands). Following withdrawal of the secretagogue, iLH and iFSH secretion diminished until they returned to control levels (within ca. 12 h). Previous exposure to GnRH enhanced the biosynthesis of Gth; this elevation was detectable up to 36 h after removal of the secretagogue. The magnitude of the elevation in Gth synthesis did not diminish with time, as secretion had, but remained constant. Gth synthesis was comparable in glands that had been exposed to GnRH 12 h and those exposed to the secretagogue 36 h prior. Thus, the GnRH-induced elevation in Gth secretion and synthesis can be dissociated; the elevation in synthesis is more chronic than the elevation in secretion.

Time-dependent changes in gonadotropin synthesis following gonadectomy in the frog, Rana pipiens.

Anterior pituitary glands from frogs gonadectomized (gonadx) for various periods (0-90 days) were labeled in vitro with 35S-methionine. Shortly (7-10 days) after gonadx, plasma levels and the in vitro basal pituitary secretion of LH and FSH are elevated compared to values in sham-operated frogs. However, LH and FSH become dissociated in long-term (over 40 days) gonadx frogs; FSH remains elevated while LH returns to sham levels. Gth (gonadotropin: LH and FSH) synthesis shows a similar pattern. Gth synthesis becomes elevated after gonadx, but returns to sham levels after 80 days. In short-term (15 days) gonadx females, LH and FSH each comprise approximately the same percentage of counts immunoprecipitated. In contrast, in long-term (90 days) gonadx females, nearly 100% of Gth synthesis can be accounted for solely by FSH; LH synthesis is barely or not detectable. Although the elevated in vitro secretion rate of LH and FSH following gonadx diminishes within 24 h in culture, Gth synthesis remains elevated. This study demonstrates that although the pattern of Gth secretion and synthesis generally parallel each other following gonadx, these two cellular processes can be dissociated from one another. Furthermore, it appears that in frogs, not only the secretion, but also the synthesis, of LH and FSH may be under independent regulation.

Relation of plasma thyroxine binding to thyroidal activity and determination of thyroxine binding proteins in a turtle, Pseudemys scripta.

The ability of plasma to bind thyroxine (T4) was examined in the turtle, Pseudemys scripta, in relation to variations in thyroidal state associated with age, sex, environment, and surgical and chemical manipulations. Relative plasma binding activity was assessed by use of binding to [125I]T4 on minicolumns of Sephadex G-25 (fine). Hypothyroidism induced by surgical thyroidectomy (Tx) or goitrogen (Methimazole) treatment resulted in a marked depression of plasma binding (50- to 100-fold) in juveniles, and T4 treatment restored binding after 4-6 weeks in long-term Tx animals and increased levels in intact animals. Among intact turtles or those made slightly hypothyroid by partial thyroidectomy, binding was consistently correlated with plasma T4. For example, juvenile turtles kept under continuous light and constant temperature (28 degrees) for 4.5 months showed a pronounced depression of plasma T4 (2.6 +/- 1.1 ng/ml) and binding capacity compared to animals raised under variable conditions (T4 = 69.6 +/- 22 ng/ml) for the last 2 months. Plasma T3 was less than 1 ng/ml in all cases. Binding levels in adult turtles were similar to juveniles, but females had significantly higher binding levels than males which paralleled differences in their plasma T4 (137 +/- 17.4 vs 83.9 +/- 13.8 ng/ml). These variations in binding were independent of total plasma protein and albumin. Plasma T4 binding measured on Sephadex G-25 was reversible and reduced by addition of exogenous T4. The affinity for T3 was 10- to 100-fold less than for T4. When plasma preincubated with [125I]T4 was electrophoresed on polyacrylamide slab gels (7% nonreducing) only a small percentage of radiolabel was associated with albumin and the majority with a slower migrating protein(s). Addition of unlabeled T4 displaced binding from the slower migrating region to the albumin and dye front (unbound). In contrast, plasma from Tx turtles showed only minimal binding and radiolabel was associated primarily with the albumin fraction. Elution of proteins from gels confirmed that only the slower migrating components bound T4 when tested on Sephadex G-25, and Tx animals lacked this binding component. The protein(s) responsible for most of the T4 binding appears to exist in low concentration. Limited comparative studies with human blood showed a similar binding activity on Sephadex G-25, but electrophoretic mobilities of binding proteins were distinct from those in the turtle. Evidence suggests that this binding protein is not prealbumin.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of gonadotropin-releasing hormone on gonadotropin biosynthesis in pituitaries of the frog, Rana pipiens.

Previous studies indicated that the chronic elevation in LH and FSH secretion from frog pituitaries stimulated with GnRH is dependent upon continued protein synthesis. To determine if GnRH is able to stimulate the de novo synthesis of gonadotropins (Gth: FSH and LH), anterior pituitaries from frogs were incubated in vitro with 35S-methionine in the presence or absence of 100 ng/ml GnRH. Glands stimulated with GnRH secreted elevated levels of FSH and LH, including higher amounts of newly synthesized Gth. Continual exposure to GnRH for 8 h did not affect the pituitary content of either immunoassayable Gth (labeled + unlabeled) or newly synthesized Gth. However, GnRH stimulation did increase the total amount (secreted + pituitary) of newly synthesized Gth. GnRH did not stimulate Gth synthesis in females. The temporal pattern of GnRH-stimulated secretion of newly synthesized Gth from male pituitaries was also determined. A lag period of 60-90 min occurred prior to appreciable secretion of radiolabeled Gth. Secretion of radiolabeled hormone then increased and reached a plateau before decreasing. After 6 h of stimulation, approximately 30% of the radiolabeled Gth still remained within the pituitary. These results are the first direct evidence that GnRH can stimulate the biosynthesis of Gth in a nonmammalian species.