Wave velocities in articular cartilage measured by micro-Brillouin scattering technique

Micro-Brillouin scattering was used to measure gigahertz ultrasonic wave velocities in the articular cartilage of a bovine femur. Velocities propagating parallel to the surface of the subchondral bone were 3.36-3.83 × 10³m/s in a dry cartilage sample. Anisotropy measurements were also performed in a 10-μm-diameter local area of the cartilage matrix. A weak velocity anisotropy reflected characteristics of the layers. The velocity also depended on the water content. In the middle layer, the velocity in the dry sample was 3.58 × 10³m/s, whereas that for a fully wet sample was 2.04 × 10³m/s.

Dependence of optical attenuation coefficient and mechanical tension of irradiated human cartilage measured by optical coherence tomography

As banked human tissues are not widely available, the development of new non-destructive and contactless techniques to evaluate the quality of allografts before distribution for transplantation is very important. Also, tissues will be processed accordingly to standard procedures and to minimize disease transmission most tissue banks will include a decontamination or sterilization step such as ionizing radiation. In this work, we present a new method to evaluate the internal structure of frozen or glycerol-processed human cartilages, submitted to various dosis of irradiation, using the total optical attenuation coefficient retrieved from optical coherence tomography (OCT) images. Our results show a close relationship between tensile properties and the total optical attenuation coefficient of cartilages. Therefore, OCT associated with the total optical attenuation coefficient open a new window to evaluate quantitatively biological changes in processed tissues.

[Forensic medical implications of histomorphological changes in the bone and cartilage tissues under effect of radiation]

The objective of the present work was to study roentgenological, microscopic, and histomorphological changes in the bone and cartilage tissues under effect of different doses of gamma-ray radiation from Gammatron-2 (GUT Co 400) and betatron bremsstrahlung radiation (25 MeV). The total radiation dose varied from 9.6 Gy to 120 Gy per unit area during 5-8 weeks. The study included 210 patients at the age from 7 to 82 years (97 men and 113 women). Histomorphological studies were carried out using samples of bone and cartilage tissues taken from different body regions immediately after irradiation and throughout the follow-up period of up to 4 years 6 months. Control samples were the unexposed bone and cartilage tissues from the same subjects (n = 14). The tissues were stained either with eosin and hematoxylin or by Van Gieson's and Mallory's methods. Gomori's nonspecific staining was used to detect acid and alkaline phosphatase activities. Moreover, argyrophilic substance was identified in the cartilaginous tissue. Best's carmine was used for glycogen staining and Weigert's stain for elastic fibers. Metachromasia was revealed by toluidine blue staining and fat by the sudan III staining technique. In addition, the ultrastructure of cartilaginous tissue was investigated. Taken together, these methods made it possible to identify the signs of radiation-induced damage to the bone and cartilage tissues in conjunction with complications that are likely to develop at different periods after irradiation including such ones as spontaneous fractures, deforming arthrosis and radiation-induced tumours.

Survival of chondrocytes in rabbit septal cartilage after electromechanical reshaping

Electromechanical reshaping (EMR) has been recently described as an alternative method for reshaping facial cartilage without the need for incisions or sutures. This study focuses on determining the short- and long-term viability of chondrocytes following EMR in cartilage grafts maintained in tissue culture. Flat rabbit nasal septal cartilage specimens were bent into semi-cylindrical shapes by an aluminum jig while a constant electric voltage was applied across the concave and convex surfaces. After EMR, specimens were maintained in culture media for 64 days. Over this time period, specimens were serially biopsied and then stained with a fluorescent live–dead assay system and imaged using laser scanning confocal microscopy. In addition, the fraction of viable chondrocytes was measured, correlated with voltage, voltage application time, electric field configuration, and examined serially. The fraction of viable chondrocytes decreased with voltage and application time. High local electric field intensity and proximity to the positive electrode also focally reduced chondrocyte viability. The density of viable chondrocytes decreased over time and reached a steady state after 2–4 weeks. Viable cells were concentrated within the central region of the specimen. Approximately 20% of original chondrocytes remained viable after reshaping with optimal voltage and application time parameters and compared favorably with conventional surgical shape change techniques such as morselization.

Bone and cartilage turnover markers, bone mineral density, and radiographic damage in men with ankylosing spondylitis

PURPOSE

To determine the levels of bone and cartilage turnover markers in men with ankylosing spondylitis (AS) and to investigate their associations with disease activity, bone mineral density, and radiographic damage of the spine.

PATIENTS AND METHODS

This cross-sectional study enrolled 35 men with newly diagnosed AS. The bone mineral densities (BMD) of their lumbar spines and proximal femurs, Bath AS Disease Activity Index (BASDAI), and Bath AS Radiographic Index (BASRI) were evaluated. Urinary C-terminal telopeptide fragments of type I collagen (CTX-I) and type II collagen (CTX-II) levels were determined by enzyme-linked immunosorbent assay, and serum levels of bone-specific alkaline phosphatase (BALP) and osteocalcin were determined by an enzyme immunoassay. Levels of biochemical markers were compared with those of 70 age-matched healthy men.

RESULTS

Patients with AS had significantly higher mean urinary CTX-I and CTX-II levels than control subjects (p<0.05). Elevated urinary CTX-I levels correlated well with BASDAI, femoral BMD, and femoral T score (p<0.05), and elevated urinary CTX-II levels correlated well with spinal BASRI (p<0.05) in patients with AS. Mean serum BALP and osteocalcin levels did not differ between patients and controls and did not show any significant correlations with BMD, BASDAI, or BASRI in men with AS.

CONCLUSIONS

Elevated CTX-I reflects disease activity and loss of femoral BMD while elevated CTX-II levels correlate well with radiographic damage of the spine, suggesting the usefulness of these markers for monitoring disease activity, loss of BMD, and radiographic damage in men with AS.

Irradiated homograft cartilage in laryngotracheal reconstruction--a preliminary experience

OBJECTIVE

To determine the suitability of irradiated homograft cartilage in pediatric laryngotracheal reconstruction (LTR).

METHODS

Retrospective case series at a tertiary care children's hospital. Pediatric patients with subglottic stenosis who had LTRs performed using irradiated homograft costal cartilage. Data was collected on postoperative complications, findings at subsequent endoscopic examinations and final outcome.

RESULTS

Minor degrees of graft resorption were observed that did not affect eventual decannulation.

CONCLUSION

Irradiated homograft costal cartilage can serve as a successful alternative to the traditional autologous costal cartilage in lower grades of laryngotracheal stenosis.

Analysis of Nd:YAG laser-mediated thermal damage in rabbit nasal septal cartilage

BACKGROUND AND OBJECTIVES

Laser cartilage reshaping (LCR) involves the use of photo-thermal heating to reshape cartilage. Its clinical relevance depends on the ability to minimize thermal injury in irradiated regions. The present study seeks to understand the safety of LCR by determining shape change and resultant tissue viability as a function of laser dosimetry.

STUDY DESIGN/MATERIALS AND METHODS

Rabbit nasal septal cartilage were irradiated using a Nd:YAG laser (lambda = 1.32 microm, 5.4 mm spot diameter) with different exposure times of 4, 6, 8, 10, 12, and 16 seconds and powers of 4, 6, and 8 W. Temperature on the cartilage surface in the laser-irradiated region was collected using infrared thermography, this data was then used to predict tissue damage via a rate process model. A Live/Dead viability assay combined with fluorescent confocal microscopy was used to measure the amount of thermal damage generated in the irradiated specimens.

RESULTS

Considerable thermal injury occurred at and below the laser-reshaping parameters that produced clinically relevant shape change using the present Nd:YAG laser. Confocal microscopy identified dead cells spanning the entire cross-sectional thickness of the cartilage specimen (about 500 microm thick) at laser power density and exposure times above 4 W and 6 seconds; damage increased with time and irradiance. The damage predictions made by the rate process model compared favorably with measured data.

CONCLUSIONS

These results demonstrate that significant thermal damage is concurrent with clinically relevant shape change. This contradicts previous notions that there is a privileged laser dosimetry parameter where clinically relevant shape change and tissue viability coexist.

The biologic effects and the therapeutic mechanism of action of electric and electromagnetic field stimulation on bone and cartilage: new findings and a review of earlier work

BACKGROUND

Muscle, ligament, bone, cartilage, blood, and adult stem-cell production all respond to electric and electromagnetic fields, and these biophysical field agents can be applied in therapeutic contexts. Postulated mechanisms at the cellular, subcellular, and molecular level are discussed. Electric and electromagnetic field stimulation enhance the repair of bone through the mediation of three areas at the cellular level: (1) the complex interplay of the physical environment; (2) growth factors; and (3) the signal transduction cascade. Studies of electric and electromagnetic fields suggest that an intermediary mechanism of action may be an increase in morphogenetic bone proteins, transforming growth factor-beta, and the insulin-like growth factor II, which results in an increase of the extracellular matrix of cartilage and bone. Investigations have begun to clarify how cells respond to biophysical stimuli by means of transmembrane signaling and gene expression for structural and signaling proteins.

METHODS

Review of meta-analysis trials of electrical stimulation of all types.

CONCLUSIONS

Further research in the form of methodologically sound, randomized, controlled studies are needed. Inter alia, resolutions are needed for the significant disparities between clinical targets, types of electrical stimulation, and clinical outcomes.

Evaluation of photothermal effects in cartilage using FT-IR spectroscopy

Photothermal effects after laser irradiation of cartilage are investigated using an infrared focal plane array (IR-FPA) camera and a Fourier transform infrared (FT-IR) spectrometer. The IR-FPA camera records radiometric temperature profile, while the local laser heating is applied to the sample; whereas the FT-IR spectrometer analyzes absorption peaks of cartilage constituents. As the major effect of photothermal heating in cartilage is water evaporation, spectral changes because of dehydration between control and laser-irradiated cartilage are recorded by FT-IR spectrometer measurements. Additionally, another interest was the observation of the spectral changes from macromolecules such as collagen and proteoglycans because of phase transformation and/or conformational changes after laser irradiation. The methodology may be useful for quantitative investigation of the relationship between the clinically important phenomenon of accelerated stress relaxation and the kinetics of macromolecular denaturation.

Preconditioning of mesenchymal stem cells with low-intensity ultrasound for cartilage formation in vivo

The purpose of this study was to evaluate the benefits of in vitro preconditioning of mesenchymal stem cells (MSCs) using low-intensity ultrasound (US) in the induction of chondrogenic differentiation of MSCs in vivo. After rabbit bone marrow-derived MSCs were seeded onto a polyglycolic acid (PGA) scaffold, the PGA-MSCs constructs were divided into 4 subgroups: untreated control, low-intensity US group, transforming growth factor-beta [TGF]-treated group and low-intensity US/TGF group. The chondrocyte-seeded PGA construct served as a positive control. For 1 week before implantation, the low-intensity US groups were subjected to ultrasound treatment for 20 min daily at an intensity of 200 mW/cm(2). The TGF groups were treated with 10 ng/mL TGF-beta1. The cells were then implanted into the nude mouse subcutaneously. Retrieved 1, 2, 4, and 6 weeks after implantation, each construct underwent gross examination, histology, biochemical assays, mechanical testing, and reverse transcriptase polymerase chain reaction (RT-PCR). Substantial size reduction and blood invasion were found much earlier in the groups that did not undergo low-intensity US than in those that did. Safranin O/Fast green staining revealed that the chondrogenic differentiation of MSCs was more widespread throughout the constructs in the low-intensity US groups. In the biochemical and mechanical analyses, the low-intensity US and low-intensity US/TGF groups were significantly better in forming hyaline cartilage-like tissue by 4 weeks than the non-low-intensity US groups. Presented by von Kossa staining, the development of osteogenic phenotypes was highly suppressed until 4 weeks in the low-intensity US groups, along with compressive strength comparable to the positive control. In the RT-PCR analysis before implantation, the messenger RNA levels of Sox-9, aggrecan, and tissue inhibitors of metalloproteinase-2 were higher in the low-intensity US groups, while those of type I and type X collagens and matrix metalloproteinase-13 were higher in the non-low-intensity US groups. Blood invasion into the constructs was also considerably hindered in the low-intensity US groups. These results strongly indicate that low-intensity US preconditioning in vitro could be an effective cue to upregulate chondrogenic differentiation of MSCs in vivo.

[The study of apoptosis factors released from laser injured cartilage inducing apoptosis of chondrocyte]

OBJECTIVE

To explore the role of pro-apoptotic signals following tissue injury and how these may promote a progression of further cell death.

METHODS

Laser treated porcine articular cartilage disks were maintained in culture media. The collected media at various time periods (3, 6, 9, 12, 24 and 48 h), was called treated conditioned media (TCM). Non-laser treated cartilage disks were used to create control conditioned media (CCM). Each disk was subsequently maintained for 28 days and used in confocal microscopic assessment to document the progression of the damaged area. Isolated porcine chondrocytes were cultured in monolayer, and were exposed to TCM, CCM or normal culture medium (NM). As a positive inducer of apoptosis, the monolayer cells were exposed to UV radiation for 10 min and cultured in NM. Following 24 h exposure, the cells were harvested and stained with the appropriate combination of fluorescent dyes and processed via flow cytometry.

RESULTS

All cultured cells exposed to TCM displayed a caspase-3 positive subpopulation, a loss of CMXRos, and with a reduced or lost NO signal. CCM exposure signals were comparable to the NM treatments with all having retained CMXRos, NO and without evidence of caspase-3 activity. UV treatment also induced a reduction in NO, but both CMXRos and caspase-3 positive, representing an earlier stage of apoptosis and suggesting that the mode of cell death via UV and TCM exposure are via different processes. The investigation of a dose (100%, 50%, 25% and 12.5%) and time (0.5, 1, 3, 9, 12 h) response to TCM exhibited that all treatments observed an increase in caspase-3 positive cells and a reduction in NO and CMXRos.

CONCLUSION

The usefulness of FCM can be used in the study of cell viability and apoptosis. Such a system may be useful in the study of mechanisms of disease such as osteoarthritis, thus may be of practical use for the pharmaceutical industry for screening associated drugs.

Expression of MMP-13 in osteoblast cells and rat tibia after exposure to gamma rays or accelerated carbon ions

In past research, we found that carbon ion irradiation increased bone volume in rats, and a significant amount of cartilage remained inside the carbon ion-irradiated trabeculae. The amounts of matrix metalloproteinase 13 (MMP-13) mRNA in osteoblast-like MC3T3-E1 cells tended to decrease after carbon ion irradiation. The level of MMP-13 mRNA in non-irradiated cells was stable during the experimental period, but in gamma ray-irradiated cells it tended to increase. When localization of MMP-13 in locally irradiated experimental rats was investigated, it was found in the marginal trabeculae in both non-irradiated and gamma ray-irradiated animals. MMP-13 was detected in osteoid and neogenetic bone in the trabeculae surface. The trabeculae in carbon ion-irradiated bone remained cartilaginous. Carbon ion-irradiated rats exhibited weak expression of MMP-13 around the cartilage inside the trabeculae. We conclude that carbon ion irradiation reduced expression of MMP-13, thus suppressing both chondrocyte maturation and cartilage resorption. Increases in hyperplasia of the bone trabeculae and of bone volume were caused by ongoing bone addition and calcification in the absence of sufficient cartilage resorption.

Effects of radiation therapy on chondrocytes in vitro

The negative irradiation complications of growth loss leading to limb length asymmetry and pathological fracture incurred following radiation therapy in pediatric patients has led to a renewed interest in understanding the specific effects of irradiation on the growth plate and the surrounding bone. In the present report, we examined the radiation therapy effects on primary rat growth cartilage chondrocytes in order to determine the chondrocyte radiosensitivity relative to other bone cell constituents and tumor cells, the postirradiation temporal progression of radiation-induced alterations in chondrocyte function, and the time course for the functional restoration of chondrocyte pathways that drive the eventual recovery in growth function. We employed an in vitro primary rat costochondral growth cartilage cell culture model system to evaluate the radiation therapy effects on proliferative chondrocytes using serial radiation doses (0-20 Gy) that are well within the clinically relevant range. Following irradiation, all of the following occurred in a dose-dependent manner: proliferation decreased, cytotoxicity increased, several markers of apoptosis increased, markers of radiation-induced cellular differentiation increased, and cell synthetic activity was disturbed. Alterations in proliferation, cell death, and induction of apoptosis are likely due to a transient radiation-induced derangement of the parathyroid hormone-related protein-Indian hedgehog proliferation-maturation pathway. Alterations in cellular differentiation and cell synthetic activity are novel observations for chondrocytes. Further, these results correspond very well to our previous work in an in vivo Sprague-Dawley rat model, making this model particularly relevant to researching the radiation therapy effects on longitudinal growth.

The effect of irradiation and hyperbaric oxygenation (HBO) on extracellular matrix of the condylar cartilage after mandibular distraction osteogenesis in the rabbit

The effects of irradiation and hyperbaric oxygenation (HBO) on the extracellular matrix of condylar cartilage after mandibular distraction were evaluated. Unilateral distraction was performed on 19 rabbits. Five study groups were included: control, low- and high-dose irradiation, and low- and high-dose irradiation groups with HBO. Additionally, four temporomandibular joints (TMJ) were used as control material. The high-dose irradiated animals were given in the TMJ 22.4 Gy/4 fractions irradiation (equivalent to 50 Gy/25 fractions). Low-dose irradiation group received a 2.2 Gy dosage. Two groups were also given preoperatively HBO 18 x 2.5ATA x 90 min. After a two-week distraction period (14 mm lengthening) and four-week consolidation period the TMJs were removed. Proteoglycan (PG) distribution of the extracellular matrix was evaluated using safranin O staining and collagen I and II using immunohistochemistry. The organization of fibrillar network was studied by polarized light microscopy. On the operated side of the control group and on the unoperated side in all, except for high-dose irradiated group, PG distribution and fibrillar network were normal appearing. In the irradiated groups, with or without HBO, the cartilaginous layer was partially or totally devoid of PG and the network structure was severely damaged. In conclusion, irradiation in conjunction with the pressure applied by distraction causes severe damage to extracellular matrix of condylar cartilage.

The effect of cartilage and bone density of mushroom-shaped, photooxidized, osteochondral transplants: an experimental study on graft performance in sheep using transplants originating from different species

BACKGROUND

Differences in overall performance of osteochondral photooxidized grafts were studied in accordance of their species origin and a new, more rigorous cleansing procedure using alcohol during preparation.

METHODS

Photooxidized mushroom-shaped grafts of bovine, ovine, human and equine origin were implanted in the femoral condyles of 32 sheep (condyles: n = 64). No viable chondrocytes were present at the time of implantation. Grafts were evaluated at 6 months using plastic embedded sections of non-decalcified bone and cartilage specimens. Graft incorporation, the formation of cyst-like lesions at the base of the cartilage junction as well as cartilage morphology was studied qualitatively, semi-quantitatively using a score system and quantitatively by performing histomorphometrical measurements of percentage of bone and fibrous tissue of the original defects. For statistical analysis a factorial analysis of variance (ANOVA- test) was applied.

RESULTS

Differences of graft performance were found according to species origin and cleansing process during graft preparation. According to the score system cartilage surface integrity was best for equine grafts, as well as dislocation or mechanical stability. The equine grafts showed the highest percentage for bone and lowest for fibrous tissue, resp. cystic lesions. The new, more rigorous cleansing process decreased cartilage persistence and overall graft performance.

CONCLUSION

Performance of grafts from equine origin was better compared to bovine, ovine and human grafts. The exact reason for this difference was not proven in the current study, but could be related to differences in density of cartilage and subchondral bone between species.

Immunologic testing of xeno-derived osteochondral grafts using peripheral blood mononuclear cells from healthy human donors

Background

One means of treating osteoarthritis is with autologous or allogeneic osteochondral grafts. The purpose of this study was to evaluate the innate immunological response in humans toward xeno-derived osteochondral grafts that have been partially or entirely treated by the photooxidation process.

Methods

The antigens tested included bovine, porcine, ovine and equine osteochondral samples that have been treated in successive steps of photooxidation. ELISPOT assays were used to evaluate the production of IL-1, IL-4, IL-6, IL-10, IL-12 and TNF-α by human monocytes in response to the antigens.

Results

Results indicated vigorous production of IL-1, IL-6, IL-10 and TNF-α in response to untreated bovine, porcine and equine specimens. This indicates that these samples are perceived as foreign, or stimulatory, by the human monocytes. There was no induction of IL-4 or IL-12, which is required for Th2 and Th1 immunity, respectively. In contrast, the processed bovine, porcine and equine samples did not induce significant activation of cells of the innate immune system. This occurred after the first step in processing (after cleaning in increasing strengths of ethanol). This suggests that the processing steps dramatically, if not completely, negated the immunostimulatory properties of the test sample. The results for the ovine samples indicate a reverse response.

Conclusion

The findings of the study suggest that photooxidized bovine, porcine or equine samples have the potential to be used as an osteochondral graft. Although the first step in processing reduced the immunological response, photooxidation is still necessary to retain the structure and mechanical integrity of the cartilage, which would allow for immediate joint resurfacing.

Soft Tissue Response of the Larynx to Silicone, Gore-Tex, and Irradiated Cartilage Implants

OBJECTIVE

The aim of the study is to compare the efficiency of three different materials (Silicone, Gore-Tex, and irradiated cartilage) used in medialization laryngoplasty. Local tissue reaction to implants in laryngeal skeleton has been examined for this purpose.

STUDY DESIGN AND METHODS

In this prospective study, New Zealand rabbits were used. Different materials have been implanted in the paraglottic space of both sides of the larynx to enable a better comparison of the different materials used. Limited medialization was applied. Special care has been taken not to narrow the airway and cause breathing problems. The reaction of the tissue in this region against the materials used has been studied. Each material was implanted 14 times in total. The rabbits were killed 6 months after the implementation to study their larynx. For each material, the fibrous capsule formation, histiocyte infiltration, foreign body giant cell infiltration, eosinophil infiltration, neutrophil infiltration, and lymphoplasmacytic infiltration levels were investigated histologically.

RESULTS

Best fibrous capsule formation has been observed around silicone. Allergic reactions and inflammatory responses were minimal for this material. Fibrous capsule formation was more limited with Gore-Tex. Some degree of chronic inflammatory response (in few cases) has been observed against this material. Severe allergic response was observed against irradiated cartilage, and the implant material was resorbed completely in most cases.

CONCLUSION

According to histopathologic results of this study (tissue compatibility of three materials), silicone is the most suited material among the study materials for medialization. Gore-Tex can also be used for this purpose. Irradiated cartilage, on the other hand, appears not to be a suitable material for medialization laryngoplasty.

Depth-resolved phase retardation measurements for laser-assisted non-ablative cartilage reshaping

Since polarization-sensitive optical coherence tomography (PS-OCT) is emerging as a new technique for determining phase retardation in biological materials, we measured phase retardation changes in cartilage during local laser heating for application to laser-assisted cartilage reshaping. Thermally-induced changes in phase retardation of nasal septal cartilage following Nd:YAG laser irradiation were investigated using a PS-OCT system. A PS-OCT system and infrared imaging radiometer were used to record, respectively, depth-resolved images of the Stokes parameters of light backscattered from ex vivo porcine nasal septal cartilage and radiometric temperature changes following laser irradiation. PS-OCT images of cartilage were recorded before (control), during and after laser irradiation. From the measured Stokes parameters (I, Q, U and V), an estimate of the relative phase retardation between two orthogonal polarizations was computed to determine birefringence in cartilage. Phase retardation images of light backscattered from cartilage show significant changes in retardation following laser irradiation. To investigate the origin of retardation changes in response to local heat generation, we differentiated two possible mechanisms: dehydration and thermal denaturation. PS-OCT images of cartilage were recorded after dehydration in glycerol and thermal denaturation in heated physiological saline. In our experiments, observed retardation changes in cartilage are primarily due to dehydration. Since dehydration is a principal source for retardation changes in cartilage over the range of heating profiles investigated, our studies suggest that the use of PS-OCT as a feedback control methodology for non-ablative cartilage reshaping requires further investigation.

Irradiated homograft rib cartilage in facial reconstruction

OBJECTIVE

To evaluate long-term structural, functional, and cosmetic results as well as resorption with the use of irradiated homologous rib cartilage grafts (IHRGs).

DESIGN

Cases in which IHRGs were used were reviewed for a long-term follow-up study for nasal and auricular reconstruction, dating back 18 years. A retrospective medical chart review was conducted in the cases in which the patients had returned for clinical examination with photographic documentation.

RESULTS

A total of 118 patients who had undergone nasal reconstruction with a mean follow-up of 36 months were identified from our database. There were 12 patients who had undergone auricular reconstruction, with a mean follow-up of 82 months. Resorption with compromise in cosmesis was noted in 11% (11/102) of the grafts used in nasal reconstruction but in 71% (5/7) of those used in auricular reconstruction. Minor resorption without change in form or function was found in 29% (30/102) of the cases. Loss of support, which was related more to graft displacement rather than resorption, was identified in 19% (21/109) of the cases, and loss of support affecting cosmesis was observed in 8% (9/109) of the cases. Maintenance of form and function appeared to be unrelated to the amount of resorption noted for the nasal grafts but was significant for the auricular grafts (P < .01).

CONCLUSIONS

The longevity of IHRGs has been favorable for functional, structural, and cosmetic nasal reconstruction, with low levels of resorption identified clinically. The use of IHRGs was associated with an unacceptable rate of graft failure in auricular reconstruction; therefore, they are no longer selected for use in such cases.

Dose response of the AIA rabbit stifle joint to boron neutron capture synovectomy

This study assessed the treatment with boron neutron capture synovectomy of synovitis in the antigen-induced arthritis (AIA) model. A boron compound, potassium dodecahydrododeca-borate (K(2)B(12)H(12)), was injected into stifle joints of 24 AIA and 12 normal rabbits and activated by neutron bombardment of the joint to achieve doses from 800 to 81,000 RBE-cGy. Synovial ablation in the AIA joint was accomplished at doses of 6,000 to 7,000 RBE-cGy with no adverse effects to skin or extracapsular tissues.

Ultrasound Enhances Transforming Growth Factor β-Mediated Chondrocyte Differentiation of Human Mesenchymal Stem Cells

In clinical studies and animal models, low-intensity ultrasound (US) promotes fracture repair and increases mechanical strength. US also promotes cartilage healing by increasing glycosaminoglycan synthesis of chondrocytes. As mesenchymal stem cells (MSCs) have the ability to differentiate into chondrocytes, US may promote their differentiation. Here, we evaluated the effects of US on the differentiation of MSCs toward chondrocytes and cartilage matrix formation. When human MSCs cultured in pellets were treated with transforming growth factor beta (TGF-beta, 10 ng/mL), they differentiated into chondrocytes as assessed by alcian blue staining and immunostaining for aggrecan, but nontreated cell pellets did not. Furthermore, when low-intensity US was applied for 20 min every day to the TGF-beta-treated cell pellets, chondrocyte differentiation was enhanced. Biochemically, aggrecan deposition was increased by 2.9- and 8.7-fold by treatment with TGF-beta alone, and with both TGF-beta and US, respectively. In contrast, cell proliferation and total protein amount appeared unaffected by these treatments. These results indicate that low-intensity US enhances TGF-beta-mediated chondrocyte differentiation of MSCs in pellet culture and that application of US may facilitate larger preparations of chondrocytes and the formation of mature cartilage tissue.

Measurement of the elastic modulus of porcine septal cartilage specimens following Nd: YAG laser treatment

Laser cartilage reshaping is a temperature-dependent process that results in stress relaxation with subsequent formation of a new and stable specimen geometry. The objective of this study was to quantitatively measure changes in the elastic moduli of porcine cartilage following laser heating. The elastic modulus of porcine nasal septal cartilage specimen (25 x 5 x 2 mm) was measured before and after Nd: YAG laser (lambda=1.32 Irvinem, 21.22 W/cm2) irradiation and following rehydration in saline solution. Specimens were secured in a single beam cantilever configuration and displaced using a calibrated thin beam load cell attached to a motorised micropositioner. Elastic modulus was calculated using elastic beam theory. Measurements were recorded before and immediately after laser heating, and following rehydration in saline solution (40 minutes, 25 degrees C). Specimens heated in saline (100 degrees C and then re-hydrated) were used as controls to determine the effect of total thermal denaturation. The calculated moduli before and after irradiation were 4.86 +/- .145 MPa and 1.166 +/- .055 MPa respectively. Following rehydration in saline, the modulus returned to near-baseline values (5.119 +/- .163 MPa). In contrast, elasticity remained lower in specimens boiled and re-hydrated (3.25 +/- .130 MPa). These findings suggest that cartilage matrix does not undergo complete thermal denaturation during laser reshaping, given the return in tissue properties with rehydration.

Reconstruction with irradiated homograft costal cartilage

The authors present their experience with 51 patients who underwent 55 reconstructive and cosmetic operative procedures with irradiated homograft costal cartilage, who were studied between August of 1988 and June of 2001. The procedures included 52 rhinoplasties and three penile implantations among a total of 130 grafts. Follow-up ranged from 7 months to 12 years. There were two immediate graft exposure complications. Late complications included displacement of the graft in two patients, fracture of the graft in one patient, and partial resorption in one patient at 6 months postoperatively. The experience is described and the literature is reviewed.

Temperature alterations of infrared light absorption by cartilage and cornea under free-electron laser radiation

Like pure water, the water incorporated into cartilage and cornea tissue shows a pronounced dependence of the absorption coefficient on temperature. Alteration of the temperature by radiation with an IR free-electron laser was studied by use of a pulsed photothermal radiometric technique. A computation algorithm was modified to take into account the real IR absorption spectra of the tissue and the spectral sensitivity of the IR detector used. The absorption coefficients for several wavelengths within the 2.9- and 6.1-microm water absorption bands have been determined for various laser pulse energies. It is shown that the absorption coefficient for cartilage decreases at temperatures higher than 50 degrees C owing to thermal alterations of water-water and water-biopolymer interactions.

[Effect of infrared laser radiation on sorption of dry cartilage and connective tissue preparations]

Cartilaginous and connective tissues were exposed to a moderate-intensity IR laser treatment with IR radiometric temperature control. The isotherms of water sorption by dry preparations of intact and laser-treated tissues were obtained and calculated in terms of well known models. It was shown that the sorption capacity of a monolayer of tissues decreases with increasing temperature during laser treatment. Changes in the supramolecular structure of the extracellular matrix of tissues (loss of regularity) upon IR laser exposure are discussed.

Bone tissue ablation with sub-microS pulses of a Q-switch CO(2) laser: histological examination of thermal side effects

. The goal of this study is an in vitro evaluation of thermal side-effects by the application of short sub- micro s CO(2) laser pulses in combination with an air-water spray on different types of bone tissue. A mechanically Q-switched CO(2) laser delivered 300 ns pulses at 9.6 micro m wavelength, which were focused down to a spot size of 440 micro m on the tissue (a corresponding energy density of 9 J/cm(2)). Bone samples (blocks from pig femur, rib, or cartilage) were moved through the beam repeatedly until 1-5 mm deep cuts were produced. An air driven water spray was applied to prevent the tissue dehydration. Subsequent visual and histological examinations revealed no carbonisation, melting traces or fissuring of the tissue. An extremely narrow, 2-6 micro m thick thermally altered layer was observed at the cut border in compacta and cartilage. No accumulation of the thermal damage occurred with increasing cut depth. Laser incisions in trabecular tissue were accompanied with a 100-200 micro m thick zone of thermal necrosis in bone marrow. The difference from compacta and cartilage can be explained considering the particular character of the spreading of the ablation products in the trabecular meshwork. Minor thermal side effects make the Q-switched and probably other short pulsed CO(2) laser systems interesting for hard tissue surgery.

Time-resolved, light scattering measurements of cartilage and cornea denaturation due to free electron laser radiation

Light scattering is used to monitor the dynamics and energy thresholds of laser-induced structural alterations in biopolymers due to irradiation by a free electron laser (FEL) in the infrared (IR) wavelength range 2.2 to 8.5 microm. Attenuated total reflectance (ATR) Fourier-transform IR (FTIR) spectroscopy is used to examine infrared tissue absorption spectra before and after irradiation. Light scattering by bovine and porcine cartilage and cornea samples is measured in real time during FEL irradiation using a 650-nm diode laser and a diode photoarray with time resolution of 10 ms. The data on the time dependence of light scattering in the tissue are modeled to estimate the approximate values of kinetic parameters for denaturation as functions of laser wavelength and radiant exposure. We found that the denaturation threshold is slightly lower for cornea than for cartilage, and both depend on laser wavelength. An inverse correlation between denaturation thresholds and the absorption spectrum of the tissue is observed for many wavelengths; however, for wavelengths near 3 and 6 microm, the denaturation threshold does not exhibit the inverse correlation, instead being governed by heating kinetics of tissue. It is shown that light scattering is useful for measuring the denaturation thresholds and dynamics for different biotissues, except where the initial absorptivity is very high.

Rate process analysis of thermal damage in cartilage

Cartilage laser thermoforming (CLT) is a new surgical procedure that allows in situ treatment of deformities in the head and neck with less morbidity than traditional approaches. While some animal and human studies have shown promising results, the clinical feasibility of CLT depends on preservation of chondrocyte viability, which has not been extensively studied. The present paper characterizes cellular damage due to heat in rabbit nasal cartilage. Damage was modelled as a first orderrate process for which two experimentally derived coefficients, A = 1.2 x 10(70) s(-1) and Ea = 4.5 x 10(5) J mole(-1), were determined by quantifying the decrease in concentration of healthy chondrocytes in tissue samples as a function of exposure time to constant-temperature water baths. After immersion, chondrocytes were enzymatically isolated from the matrix and stained with a two-component fluorescent dye. The dye binds nuclear DNA differentially depending upon chondrocyte viability. A flow cytometer was used to detect differential cell fluorescence to determine the percentage of live and dead cells in each sample. As a result, a damage kinetic model was obtained that can be used to predict the onset, extent and severity of cellular injury to thermal exposure.

Speckle-contrast monitoring of tissue thermal modification

Measurements of the contrast value of time-averaged speckle-modulated images of cartilage tissue are used to study tissue thermal modification in the case of laser-light treatment. This modification is related to thermally induced internal stress relaxation in the matrix of the treated tissue. The specific feature of the evolution of time-averaged speckle contrast with a change in the current temperature of modified collagen tissue is the typical looplike form of the contrast-temperature dependencies associated with irreversible changes in tissue structure and correlated with changes in the tissue diffuse transmittance and the tissue internal stress mentioned by other researchers.

Immediate reconstruction of extruded alloplastic nasal implants with irradiated homograft costal cartilage

OBJECTIVE

To describe a novel surgical protocol for the management of patients presenting with extruded nasal implants.

STUDY DESIGN

Retrospective chart review.

METHODS

Analysis of consecutive patients presenting with extruded nasal implants from 1986 to 2000. Patients were selected from a large database of revision rhinoplasty cases. Inclusion criteria were: 1) at least one previous rhinoplasty procedure, 2) an extruded nasal implant that was documented preoperatively, 3) immediate reconstruction that was carried out with irradiated homograft costal cartilage (IHCC), and 4) at least 1 year of follow-up recorded, including standard postoperative rhinoplasty photographs. A total of 18 patients met the inclusion criteria and form the basis of this study. Data gathered from the charts included date of surgery, last date of follow-up, location of implant extrusion, alloplastic material, specific use of IHCC for reconstruction, percent of clinical IHCC resorption at last follow-up, and presence of warping of the IHCC.

RESULTS

All 18 patients were satisfied with the cosmetic outcomes of their nasal reconstructions. The most common extruded alloplast was Silastic, followed by Gore-Tex (W.L. Gore & Associates, Inc., Flagstaff, AZ). There were no cases of extrusion or infection of the IHCC implant subsequent to immediate reconstruction of the extruded alloplast. Clinical resorption of the IHCC was minimal, with a mean follow-up of 26 months. Only one patient had a complication, warpage, resulting in removal of the IHCC. In that patient, the IHCC still had carving markings on the implant after 2 years in vivo.

CONCLUSIONS

In this series of patients, a novel surgical protocol was used. The extruded implant was removed and immediate reconstruction with irradiated rib cartilage was done. All patients were evaluated for postoperative infection, graft extrusion, and satisfaction with cosmetic result. There was one major complication in this series of 18 patients, warping of the IHCC, which necessitated removal and replacement. This approach appears to be a reasonable method for reconstruction of extruded nasal alloplasts.

Upregulation of basal TGFbeta1 levels by EMF coincident with chondrogenesis--implications for skeletal repair and tissue engineering

Members of the TGFbeta/BMP gene family regulate cartilage and bone development. These genes are re-expressed in bone repair and are thought to mediate chondro- and osteoprogenitor cell differentiation. These observations have led to a therapeutic strategy of introducing these growth factors into experimental cartilage and bone defects. Therapeutic efficacy, however, has been limited by diffusion or inactivation of these growth factors from the desired site and by the inability to deliver sustained concentrations of growth factors. This study demonstrates an increase in basal TGFbeta mRNA and protein levels in association with chondrogenic differentiation in endochondral ossification. mRNA is increased by 158%; protein by 23%, and cells immunopositive for TGFbeta by 343% at maximal TGFbeta expression. Importantly, the pattern of TGFbeta expression is preserved throughout the developmental sequence. Our data suggest that the exposure to a specific electromagnetic field (EMF) enhances, but does not disorganize, chondrogenesis and endochondral calcification as well as the normal physiologic expression of TGFbeta. The ability to increase TGFbeta at a moderately low dose for sustained periods of time without disorganizing its physiology suggests the ability to establish temporal concentration gradients of growth factors for the purpose of stimulating skeletal repair.

[Cartilage cell stimulation with low-power laser: experimental assessment]

The aim of this study was to verify the effects of laser therapy performed with Ga-Al-As diode laser (780 nm, 2500 mW) on cartilage cells in vitro. The cartilage sample used for biostimulation was taken from the knee of an adult patient. The cultures were divided into four groups: Groups I, II, III were subjected to biostimulation with different laser parameters; Group IV did not received any treatment. The laser biostimulation was conducted for five consecutive days. At the end of the treatment, cell count and MTT tests were performed to assess cell metabolism. The data showed good results in terms of cell viability in the groups treated with laser biostimulation compared to the untreated group. The results obtained with the use of this new low-power diode laser Ga-Al-As device in the biostimulation of the cartilage tissue, permits us to consider the use of this device clinically.

An ultrastructural study of osteoclasts and chondroclasts in poorly calcified mandible induced by high doses of strontium diet to fetal mice

A high dose strontium diet was fed to fetal mice from day 1 of gestation to birth in order to investigate the ultrastructural changes of osteoclasts/chondroclasts when associated with poorly calcified bone/cartilage. Calcification in the mandibular bone and condylar cartilage was extensively inhibited by this diet. Multinucleated osteoclasts and chondroclasts were observed on the mandibular alveolar bone and in the resorption area of the condylar cartilage, respectively. However, both cell types never formed ruffled borders and clear zones at the cell surfaces facing the matrices indicative of bone resorption, although they had well-developed organelles and vacuoles. Furthermore, they revealed signs of phagocytosis of the matrix vesicles. These results indicate that osteoclasts/chondroclasts can exhibit phagocytotic activity in response to requirements.

Calculation of electric fields induced in the human knee by a coil applicator

Calculations are presented of the induced electric fields and current densities in the cartilage of the knee produced by a coil applicator developed for applying pulsed magnetic fields to osteoarthritic knees. This applicator produces a sawtooth-like magnetic field waveform composed of a series of 260-micros pulses with a peak to peak magnitude of approximately 0.12 mT in the cartilage region. The simulations were performed using a recently developed 3 dimensional finite difference frequency domain technique for solving Maxwell's equations with an equivalent circuit model. The tissue model was obtained from the anatomically segmented human body model of Gandhi. The temporal peak electric field magnitude was found to be -153 mV/m, averaged within the medial cartilage of the knee for the typical dB/dt excitation levels of this coil. The technique can be extended to analyze other excitation waveforms and applicator designs.

Assessment of low-power laser biostimulation on chondral lesions: an "in vivo" experimental study

The purpose of this study was to evaluate whether intraoperative laser biostimulation can enhance healing of cartilaginous lesions of the knee. Surgery was performed on eighteen rabbits: a bilateral chondral lesion of 1.25 +/- 0.2 mm in length and 0.8 +/- 0.2 mm in width was created in the femoral medial condyle with a scalpel. The lesion in the left knee of each animal was treated intraoperatively using the diode Ga-Al-As 780nm. laser (300 Joules/cm2, 1 Watt, 300 Hertz, 10 minutes), while the right knee was left untreated, as control group. The animals were divided into three groups, A, B and C, according to the survival time after surgery, two, six and twelve weeks, respectively. The explants from the femoral condyles, both treated employing laser energy and left untreated, were examined histologically. Results showed a progressive filling with fibrous tissue of the cartilaginous lesion treated with laser irradiation, while no changes in the original lesion of the untreated group were observed at the end of the study. Maybe, in this experimental research, underexposure to laser irradiation was the cause for the absence of the necessary conditions for biostimulation.

The rate of warping in irradiated and nonirradiated homograft rib cartilage: a controlled comparison and clinical implications

Irradiated homograft costal cartilage reportedly warps less than autologous cartilage based on clinical observation; however, no controlled, experimental studies on the warping characteristics of irradiated homograft costal cartilage have been done. Fresh cadaver costal cartilage (ribs 5 through 8) was prepared and irradiated using a standardized technique. A specially designed cartilage-cutting device was used to cut the cartilage into a reproducible size. The irradiated (n = 23) and nonirradiated (n = 20) groups were incubated in vitro and assessed over a 4-week period. There was no significant difference in warping between the irradiated and nonirradiated groups (p = 0.1). The centrally cut pieces of cartilage in each group warped less than peripherally cut blocks in each group. Peripherally cut pieces of both the irradiated and nonirradiated groups warped at a faster rate compared with the nonirradiated groups. All cartilage exhibited continued warping over the 4-week study period. We concluded that there was no difference in warping characteristics between irradiated and nonirradiated homograft rib cartilage. Furthermore, unlike previous studies, cartilage grafts continued warping over time for at least 4 weeks, and this phenomenon may be extrapolated as a causative factor in delayed postoperative nasal deviation after rhinoplasty and nasal reconstruction where rib grafts are used.

Effects of ionizing radiation on cartilage: emphasis on effects on the extracellular matrix

In this report, we review data dealing with radiation effects on cartilage. More specifically, we emphasize on alterations caused in the extra-cellular cartilage matrix. Although radiation studies predominantly describe the effect on the structure of DNA and on the mitotic activity of cells, alterations caused by the effect on the non-mitotic activity can also be important. Cartilage, having an extracellular matrix composed of 2 major components, aggrecan and collagen, provides a good model to study this kind of radiation effects. The following topics concerning literature data are summarized: effects on the amount of matrix synthesized, effects on the activity of certain enzymes and effects on the structure and morphology of the matrix. Some new findings concerning the radiation effect on the size distribution of aggrecan-aggregate populations, de novo synthesized by chondrocyte cultures, either derived from calcifying or from non-calcifying cartilage, are given.

Electron beam-induced changes in vitreous sections of biological samples

Nonpretreated high pressure frozen samples of Zea mays, cartilage and human erythrocytes were cryosectioned and observed at 110K in a cryoelectron microscope. Changes induced by medium doses of electron irradiation (< 10 ke nm-2) are described. After some ke nm-2, the most conspicuous cutting artefacts are erased to a large extent and the visibility of the cell organelles is improved. The sections, compressed in the cutting direction by the sectioning process, shrink once more, in the same direction, when irradiated. This shrinkage depends on the section support and on how the section is adsorbed to it. Shrinkage is not uniform: it is most pronounced in mitochondria, condensed chromatin and nucleolus. This differential shrinkage improves the visibility of major structures on the section and, as a result, 'nicer' images are recorded. However, this apparent improvement is a beam-induced artefact that must be paired with a loss of high resolution information.

[Late effects of radiations on mature and growing bone]

The physiopathology of radiation-induced bone damage is no completely elucidated. Ionizing radiation may induce an inhibition or an impairment of growing bone. This fact is of particular importance in children, and represents one of the most important dose-limiting factors in the radiotherapeutic management of children with malignant diseases. Scoliosis, epiphyseal slippage, avascular necrosis, abnormalities of craniofacial growth may be observed after radiation. Child's age at the time of treatment, location of irradiated bone and irradiation characteristics may influence the radiation-related observed effects. In adults, pathological analysis of mature bone after ionizing radiation exposure are rare, suggesting that it is difficult to draw a clear feature of the action of radiation on the bone. Osteoporosis, medullary fibrosis and cytotoxicity on bone cells lead to fracture or necrosis. Various factors can influence bone tolerance to radiation such as bone involvement by tumor cells or infection, which is frequent is mandibulary osteoradionecrosis. Technical improvements in radiation techniques have also decreased radio-induced bone complications: the volume, fractionation and total dose are essential to consider. The absence of a consistent radiation-induced late effects evaluation scale has hampered efforts to analyze the influence of various therapeutic maneuvers and the comparison of results from different reported series. The currently proposed evaluation scale may help harmonizing the classification of radiation-induced bone late effects.

Irradiated rib cartilage graft for reconstruction of the tympanic membrane: preliminary results

OBJECTIVE

To evaluate the advantages, disadvantages, safety, and results in reconstruction of the tympanic membrane using irradiated rib cartilage.

STUDY DESIGN

Retrospective chart review.

SETTING

A tertiary referral center.

PATIENTS

All patients who had > or =6 months follow-up who underwent tympanoplasty or tympanomastoidectomy using irradiated rib cartilage graft at our institution from January 1, 1993 to December 31, 1996.

INTERVENTION

Tympanoplasty or tympanomastoidectomy using homologous irradiated rib cartilage as graft material.

MAIN OUTCOME MEASURES

Postoperative speech reception thresholds, speech discrimination scores, and air-bone gap were compared with preoperative levels. Complications directly related to irradiated rib cartilage tympanoplasty were sought.

RESULTS

Speech reception threshold did not significantly change. Speech discrimination scores were stable or improved in all patients. Postoperative air-bone gap was < or =10 dB in 43.2% of patients and < or =20 dB in 70.3% of patients. There was a 16% complication rate regarding tympanoplasty in general. No complications unique to irradiated rib cartilage occurred.

CONCLUSION

Irradiated rib cartilage is an alternative tympanoplasty material that may save operating time, spares patients an added incision, provides results similar to other grafting material, and is safe.

Thermal and diffusion processes in laser-induced stress relaxation and reshaping of cartilage

The thermodynamic characteristics of the 'bound-to-free' phase transformation of water are studied by means of differential microcalorimetry and FTIR spectroscopy. This phase transition controls the stress relaxation and reshaping of cartilage which we have observed previously under moderate laser heating. It is shown that the FTIR spectrum of bound water in cartilage differs from that of free water in cartilage, and that both show differences to the FTIR spectrum of pure water. The proportion of bound water in cartilage is found to be of the order 4%. We have examined water liberation and absorption kinetics and found them to be controlled by diffusion through the tissue and also by the bound-to-free water transformation. The theoretical modelling and experimental data allowed calculation of diffusion coefficients and the activation energy for water transfer. The latter was found to be close to the heat of phase transformation of water. We have established that the drying and wetting processes in cartilage are reversible (fully or in a part, depending on the temperature of preliminary drying) and can be described by identical solutions of the diffusion problem, with coefficients of water diffusion being the same. The mechanism of water diffusion in cartilaginous tissue is also discussed.

[Skeletal changes induced by radiotherapy. A study of subjects with retinoblastoma. II]

The authors examine the dental and skeletal alterations consequent to the use of radiotherapy as the elective method of treating retinoblastoma, an endobulbar neuroectodermal tumour typical of early infancy. The authors revise the basic concepts of radiobiology and the modifications induced by radiation in developing tissues with reference to both alterations at a microscopic (histological) level and those at a macroscopic level, namely of a morphological and structural nature. In the first part of the study the authors examine the damage to dental structures relating to both developing tissues and damage to mature tissue. The second part of the paper analyses radiation damage on cartilage and bone tissues in the process of formation and the authors present their documentation in the form of iconographic and radiographic material together with an esthetic face analysis performed using Rickettz's method in three cases referred to their attention.

[Experimental study of biological tissue permeability to Nd-YAG laser irradiation with wave length 1.06 and 1.32 mm]

The author studied penetration of YAG-Nd laser radiation (1.06 and 1.32 mm) through some biological tissue. The least penetration of the laser rays occurred in the bone and cartilage tissue. Maximal difference in the penetration rate was recorded in more transparent for this radiation media - blood agar and nasal polyps. The above methodological approach and its results may be used for estimation of the energy needed for reaching different biotissue layers in remote and contact exposure to YAG-Nd laser.

Assessment of mucosal underdosing in larynx irradiation

PURPOSE

Mucosal underdosing as a result of electron disequilibrium at the air cavity may affect local recurrence rates for T1 and T2 larynx cancers. Secondary build-up properties of high-energy beams have been demonstrated in a slab phantom. It was the aim of this investigation to determine whether significant surface underdosing exists for the mucosa under clinical conditions.

METHODS AND MATERIALS

Measurements were made using a thermoluminescent dosimetry (TLD) extrapolation technique in an anatomic larynx phantom. The larynx phantom was constructed using tissue and cartilage equivalent material, based on patient cross-sectional anatomy. Three different thicknesses of LiF ribbons, 0.14, 0.39, and 0.89 mm, were placed reproducibly at 12 different positions at the anterior, posterior, and lateral walls on the endolarynx surface. Measured doses were plotted and an extrapolation was made back to the mucosal depth to obtain the dose received at each of the positions. Results were obtained for two different field configurations, opposed laterals and oblique fields, for 6-MV X rays and opposed lateral fields from a telecesium unit. In addition, the larynx surface doses of field sizes from 4 x 6 cm2 to 7 x 6 cm2 were investigated.

RESULTS

Surface underdosing was observed owing to the secondary build-up and build-down effect of the air cavity, and the dose measured for the three extrapolation TLDs at any position varied by up to 18%. An average variation of 6% was observed. The surface underdosing was most apparent for the 6-MV opposed lateral beam technique, where mucosa doses down to 76% of the prescribed dose were observed. Mucosal underdosing at the measurement positions was less marked with oblique techniques, telecesium treatment, and increasing field size.

CONCLUSION

Because of underdosing, some surface positions receive < 80% of the prescribed dose. This may contribute to the potential for higher recurrence rates observed with high-energy photons.

Effects of X irradiation on metabolism of proteoglycans

The effects of X irradiation on matrix formation by growth-plate and articular chondrocytes, as reflected by metabolism of proteoglycans and type II collagen, were examined in a rabbit chondrocyte culture system. Irradiation with 1 to 10 Gy selectively inhibited synthesis of proteoglycans (incorporation of [35S]sulfate) depending on the stage of differentiation of the irradiated cells; however, synthesis of type II collagen was not affected. Irradiation of an immature culture, in which chondrocytes had just reached confluence, suppressed incorporation of [35S]sulfate into the glycosaminoglycan, 10 Gy inducing approximately 45-50% inhibition. In contrast, the irradiation of mature cultures, in which chondrocytes had already secreted extensive cartilage matrix, did not affect the rate of synthesis of proteoglycans (incorporation of [35S]sulfate). We also found that here irradiation stimulated the degradation of proteoglycans, but with the effect differing in growth-plate chondrocytes and articular chondrocytes. In growth-plate chondrocytes, cleavage from a site close to the G1 globular domain induced by 10 Gy enhanced the release of 35S-labeled proteoglycans into the medium, whereas in articular chondrocytes, irradiation had only marginal effects on the release of 35S-labeled proteoglycans. Our results show that irradiation with 1-10 Gy impaired proteoglycan metabolism in cartilage, with differing effects according to the stage of cell differentiation and the type of chondrocyte.

[Possibilities of the use of surgical laser irradiation in spontaneous formation of cartilage tissue in ENT plastic surgery]

The experiments were made to study CO2-laser ability to promote spontaneous formation of nasal septum cartilage. Laser-induced changes in physical and histological characteristics of the cartilage tissue were followed up. Optimal regimens of radiation were selected which allowed to modify cartilage shape without impairment of its morphological and histological structure. In vivo tests were performed on rabbit auricular floor cartilage. The present shape of the cartilage remained stable. It is inferred that laser energy may be a promising tool in plastic ENT surgery.

The effects of irradiation dose on the stiffness of cartilage grafts

Various centers report irradiated cartilage graft absorption rates that differ quite widely. We postulated that a major factor governing this phenomenon might be irradiation dose. Irradiation produces collagen cross-binding and increased resistance to absorption of such material when implanted. Since cross-binding produces stiffening of collagen, cartilage grafts were exposed to increasing doses of irradiation and their elastic modulus was measured. The postulate was that increasing radiation doses will produce grafts of increasing stiffness. Sternal cartilage, harvested from horses, was cut into blocks of a standard size and irradiated to 4, 6, 8, and 10 megarads. The elastic modulus of each specimen and matched control were measured on an Instron flexural testing machine (Instron Corp, Canton, MA). Irradiation at all four doses reduced the elastic modulus of the cartilage grafts, with the lowest dose producing a reduction of 50% and the highest dose one of 90%. High-dose irradiation appears to lessen greatly the stiffness of cartilage grafts and may be responsible for increasing absorption of grafts in centers in which high doses are used.

Effects of UVC irradiation on cultured mouse embryonic limb bud cells

Effects of UVC irradiation (UVC) at a dose range from 0 to 30 J/m(2) were investigated on the cultured embryonic limb bud cells (LBC), isolated from fore- and hindlimbs of day 11 mouse embryos. Although dose-dependent inhibition was found for both cellular proliferation and chondrogenesis, the chondrogenic proteoglycan (PG) synthesis was more sensitive to UVC than cellular proliferation when compared at ID(50), the inhibitory dose that reduced assessment value by 50% of the control. No significant difference in induction and repair kinetics of UV-induced cyclobutane pyrimidine dimers (CPDs) and (6-4) photoproducts ((6-4)PPs) were found between LBC and NIH3T3 mouse cell line. The fluorescent light (FL) treatment of LBC pre or post UVC irradiation did not affect repair kinetics of CPDs and (6-4)PPs, cellular proliferation, formation of PG-producing nodule and the PG synthesis.