Vitality of chondrocytes in the mandibular condyle as revealed by collagen formation. An autoradiographic study with 3H-proline

Histological and autoradiographic studies using ³H-proline indicate that cartilaginous tissue in the mandibular condyle maintains morphologic and metabolic characteristics of an embryonic type of tissue. Cartilage cells in the condyle lack the specific arrangement and cellular homogeneity characteristic of more differentiated endochondral growth sites. Through dedifferentiation many chondrocytes in the mandibular condyle appear to outlive the hypoxic conditions that are reported to prevail within the mineralizing zone. Chondrocytes in this zone reveal only a minimal amount of ³H-proline uptake in comparison with the cells in the chondroblastic and premineralizing zones. The dedifferentiated chondrocytes appear to redifferentiate into more specialized cells, possibly osteoprogenitor cells, as they reveal a significant increase in ³H-proline incorporation in the vicinity of the ossifying front. These observations on proline metabolism support the concept that calcification in the condylar cartilage is not necessarily accompanied by degeneration and death of the chondrocytes.     

Ultrastructural alteration of cartilaginous fibril arrangement in the rat mandibular condyle as revealed by high-resolution scanning electron microscopy.

Three-dimensional alteration of fibrillar matrix in the rat mandibular condylar cartilage was investigated with a high-resolution scanning electron microscope (SEM) and it was determined whether alterations correlate with developing occlusion and advancing age. Two important SEM techniques of DMSO freeze-cracking and treatment with trypsin and hyaluronidase were employed to remove interfibrillar proteoglycans and disclose fibril arrangement. Our SEM investigation demonstrated that collagen fibrils in the fibrous zone covering hyaline-cartilaginous area in the condyle are thicker (50 to 80 nm in diameter) than the fibrils (30 to 50 nm in diameter) that predominantly constituted an interterritorial fibrillar matrix (IFM) in the area. While the thick fibrils had a distinct striation of about 55 nm periodicity, the thin fibrils had no distinguishable striation. The thick fibrils having a periodic striation of about 60 nm was found along with the thin fibrils, also in the IFM in the aged rats and in the deep IFM, but were considerably less than the thin fibrils. The fibrils in the fibrous zone and IFM were disorderly arranged at 19-day-insemination age. In 1-week-old rats whose incisors erupted, the fibrils constituting the fibrous zone altered from disordered to ordered arrangement. The IFM in these rats took the form of a network. Incorporation of small fibrillar bundles into the fibrillar network was seen in 2-week-old rats whose upper and lower first molars erupted. In 8-week-old rats whose molars had erupted completely, the IFM completely occupied by regularly oriented fibrils appeared additionally.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cellular stages in cartilage formation as revealed by morphometry,radioautography and type II collagen immunostaining of the mandibular condyle from weanling rats

The role played by cell addition, cell enlargement, and matrix deposition in the endochondral growth of the condyle was assessed in weanling rats by four approaches making use of the light microscope: morphometry, ³H-thymidine radioautography, ³H-proline radioautography, and immunostaining for the cartilage-specific type II collagen. From the articular surface down, the condyle may be divided into five layers made up of cells embedded in a matrix: (1) the articular layer composed of static cells in a matrix rich in fibers presumed to be of type I collagen, (2) the polymorphic cell layer including the progenitor cells from which arise the cells undergoing endochondral changes, (3) the flattened cell layer in which cells produce a precartilagenous matrix devoid of type II collagen while undergoing differentiation in two stages: a “chondroblast” stage and a short “flattened chondrocyte” stage when Intracellular type II collagen elaboration begins, (4) the upper hypertrophic cell layer, in which cells are “typical chondrocytes” that enlarge at a rapid rate, actively produce type II collagen, and deposit it into a cartilagenous matrix, and (5) the lower hypertrophic cell layer, composed of chondrocytes at a stage of terminal enlargement while the cartilagenous matrix is adapting for mineralization. ³H-thymidine radioautographic results indicate that the turnover time of progenitor cells in the polymorphic cell layer is about 2.9 days. The time spent by cells at each stage of development is estimated to be 1.4 days as chondroblasts, 0.5 days as flattened chondrocytes, 2.3 days as the chondrocytes of the upper hypertrophic cell layer, and 1.1 days as those of the lower hypertrophic cell layer. Calculations referring to a 1 × 1-mm square-sided column extending from the articular surface to the zone of vascular invasion provide the daily rate of cell addition (0.0077 mm³), extracellular matrix deposition (0.0127 mm³), and cell enlargement (0.0302 mm³). Hence the respective contribution of the three factors to condyle growth is in a ratio of about 1:1.6:4. This result emphasizes the role played by cell enlargement in the overall growth of the condyle.     

The functional projections of the anterior ventralis nucleus, as revealed by autoradiography

The effect of stimulation of ventral anterior nuclei of the thalamus (VA) was studied in different areas of cat cortex (sensory, motor and association) with [3H]glycine autoradiography. One-hour VA stimulation resulted in the most intensive [3H]glycine incorporation in the second, third and fifth layers of the anterior suprasylvian gyrus and of the motor cortex. The labelling was less intensive in the sensory (auditory) and association (posterior middle suprasylvian association area) cortices, but the effect of VA stimulation reached these regions as well. The VA stimulation resulted in evoked potentials over the whole area examined, with highest amplitude and shortest latency in the anterior suprasylvian gyrus. It is suggested that the [3H]glycine autoradiography is suitable to study the functional projection of non-specific thalamocortical systems.     

Plate osteosynthesis of the mandibular condyle

The aim of this study is to evaluate and compare the biomechanical stability of various osteosynthesis materials for mandible condylar-process fractures. On 160 porcine mandibles, four different monocortical plating techniques (40 per group) were investigated. Condyles were fractured at a defined location from the incisure to the posterior border. After correct anatomical reduction the fractures were plated, using four different techniques. Osteosynthesis materials used were the delta plate, the trapezoid plate, the dynamic compression plate and double mini-plates. Each group was subjected to linear loading in lateral to medial, medial to lateral, anterior to posterior and posterior to anterior directions by a universal mechanical testing machine TIRAtest 2720. Yield load, yield displacement were measured for the different plates. Statistically significant differences were noted between the fixation groups in all four directions. Rigid internal fixation with double mini plates showed the best stability in all directions except posterior to anterior. In this direction, the delta-plate resisted the highest loads. In the three other directions, the delta plate was second best with data similar to double miniplates but lower in magnitude.     

Distribution of 35S-sulfate within the transseptal ligament of the mouse

The distribution of 35S-sulfate-labeled macromolecules was examined within three regions of the transseptal ligament: the 1) mesial, 2) middle and 3) distal thirds. Swiss mice, 6 weeks of age, were injected with 35S-sulfate and killed after 1, 6, and 12 hours and 1, 2, 3, 4, 5, and 7 days. Silver grains and cell nuclei were counted on autoradiographs which had been counterstained by the Van Gieson method, and mean counts were analyzed statistically. Analysis of variance revealed no significant differences in mean number of cell nuclei between regions throughout the course of the experiment. 35S-sulfate was rapidly incorporated into the transseptal ligament macromolecules. Grain counts were highest 6 hours after injections: counts were highest over the middle and lowest over the mesial thirds of the ligament. The rate of grain removal was significantly higher in the middle third compared to the mesial or distal thirds (P less than 0.001) and was significantly lower in the mesial third compared to the middle or distal thirds (P less than 0.001). The half-life of labeled macromolecules was significantly greater in the mesial and distal thirds than in the middle third (P less than 0.005). The data demonstrate significantly higher rates of turnover of 35S-sulfate-labeled macromolecules in the middle region of the transseptal ligament. Since cellular density was similar throughout the transseptal ligament, higher turnover rates of 35S-sulfate-labeled macromolecules probably indicate higher rates of cellular activity in this region, possibly a result of tissue remodeling coincident to stresses generated by occlusal forces and physiologic drift of the adjacent teeth.     

周期性张应力促进兔髁状突软骨细胞的增殖

背景：髁状突是下颌最重要的生长区之一,终生具有生长改建能力。在体内条件下,细胞力学的功能研究因其所处生理环境的复杂性、刺激因素传导的不定向性、实验条件的不易控制性而很难得到满意结果,应力刺激对髁状突软骨细胞的直接影响需要进一步行体外研究。 目的：观察周期性张应力对体外培养兔髁状突软骨细胞生长增殖的影响。 方法：体外分离培养及鉴定兔髁状突软骨细胞,在细胞培养至第3代时使用细胞加力装置对细胞施加强度为10%,频率为6循环/min的周期性张应力,作用时间分别为1,6,12和24 h,并设置未加力组作为对照。应用流式细胞仪检测细胞生长周期,应用MTT法分析细胞的增殖活性。 结果与结论：在周期性张应力下,髁状突软骨细胞流式细胞仪检测结果显示在加力6 h和12 h,加力组细胞生长周期开始有显著性变化,在24 h达到实验最大值,差异有显著性意义(P < 0.01)。MTT检测结果示细胞生长活跃,在6,12 h与对照组有明显变化,在24 h达到实验最大值,差异有显著性意义(P < 0.01)。提示周期性张应力可明显促进髁状突细胞增殖,在24 h内具有持续促进作用。 中国组织工程研究杂志出版内容重点：组织构建;骨细胞;软骨细胞;细胞培养;成纤维细胞;血管内皮细胞;骨质疏松;组织工程全文链接：     

Sulfation and transport of basement membrane proteoglycans,as visualized by 35S-sulfate radioautography in the endodermal cells of the rat parietal yolk sac

In the hope of clarifying the biogenesis of basement membrane proteoglycans, an injection of ³⁵S-sulfate was given to concepti of 12-day gestant Sherman rats. The parietal wall of the yolk sac (including endodermal cells and the associated basement membrane known as Reichert's membrane) was removed at times varying from 7 min to 24 hr after injection and processed for electron microscopic radioautography. Silver grains were counted over the organelles of endodermal cells as well as over Reichert's membrane. Between 7 min and 2 hr after ³⁵S-sulfate injection, radioactivity was observed in the endodermal cells, while from 4 to 24 hr it was mostly present in Reichert's membrane. Detailed distribution of the cellular radioactivity at 7 and 15 min showed about 20% in the rough endoplasmic reticulum (rER), 60% in the Golgi apparatus, and 8% in secretory granules. The radiactivity present in rER and Golgi apparatus decreased to low levels by 2--4 hr after injection. In secretory granules, radioactivity increased to reach a peak at 2 hr and then declined; moreover, only the granules associated with the trans Golgi face were radioactive at early time intervals, while those scattered through the cytoplasm and along the cell surface became radioactive at later times. Between 4 and 24 hr, radioactivity became negligible over all cell organelles, while it was collected in Reichert's membrane. Biochemical reports indicate that when ³⁵S-sulfate is added to organ cultures of Reichert's membrane and endodermal cells, about 90% of the incorporated which these proteoglycans acquire sulfate are likely to be those labeled at 7 min after ³⁵S-sulfate injection, that is, the Golgi apparatus and to a lesser extent the rER, whereas some labeling of the secretory granules located at the trans Golgi face is explained by rapid acquisition of sulfated proteoglycans from the Golgi apparatus. Label later appears in the secretory granules along the cell surface and, eventually, in Reichert's membrane. It is concluded that secretory granules transport newly formed proteoglycans from the Golgi apparatus to the outside for deposition into Reichert's membrane.     

Surgical anatomy of the preauricular anteroparotid approach for mandibular condyle surgery

Purpose

The different surgical approaches used to treat mandibular condyle fractures are carried out in the periparotid skin area and can lead to facial nerve injury. We conducted a preauricular and anteroparotid surgical approach. Our main aim was to show the anatomical relationship between this approach site and the facial nerve branches, and to define cutaneous landmarks to locate the extraparotid facial nerve branches.

Method

A 2-step dissection of 13 fresh human cadaver semi-heads was performed: a preauricular approach followed by a superficial parotidectomy to visualize the facial nerve. Its course and ramifications were studied and compared to cutaneous landmarks. The proximity of the facial nerve branches with the surgical approach site was observed.

Results

The approach allowed systematically visualising the zygomatic and/or buccal branches. No facial nerve branches were sectioned. In three cases (23 %), a nerve branch was visualized during the approach. The buccal and zygomatic branches were ramified in 77 % of cases.

Conclusions

During our preauricular anteroparotid approach, the buccal and zygomatic branches were visualized but none was sectioned. Most often the approach was carried out between these two branches (46 % of cases). Cutaneous landmarks used were reliable to define a safe and nerve-free area for dissection. The buccal and zygomatic branches are very interesting because their high number of ramifications and anastomoses could serve as nerve relays in case of surgical lesion.     

Down-regulation of thyrotropin-releasing hormone (TRH) receptors in spinal cord after transection as revealed by quantitative autoradiography

Summary The autoradiographic localization of thyrotropin-releasing hormone (TRH) receptors was investigated in the rat spinal cord after transection at the level of T8–T9. The discrete distribution of [³H]-MeTRH binding was measured with a computerized image analyzer at the cervical (C6–C7) and lumbar (L2–L3) level, one week and three weeks after injury. The TRH receptor density was expressed in fmol/mg protein. There was no significant change in the density of TRH receptors below the injury site. In the cervical region, TRH receptor concentration in the dorsal gray matter did not differ from normal controls; in contrast we found a time-dependent change in lamina 10 and in the ventral gray, with a significant decrease (25% and 19%, respectively) of TRH receptor binding sites one week after transection and a return to control levels by three weeks. From these data and the known increase of TRH immunoreactivity above a spinal injury, a down-regulation of spinal cord TRH receptors in response to elevated levels of TRH is suggested.     

下颌骨髁突支架的个体化设计与初步构建

Objective To explore the method of designing and manufacturing the mandibular condyle scaffold individually by rapid prototyping technologies and reverse engineering.Methods Cranial CT image data were processed in Mimics software for reconstruction of one side of ramus of mandible, and were inputted into Solidworks software to edit by the format of stl. A negative mold of the mandibular condyle scaffold was obtained. The mold was fabricated by resin materials utilizing rapid prototyping. Biomaterials were filled into the resin mold. When the materials were cured, we eliminated the resin mold and acquired a multi-pores three dimensional mandibular condyle scaffold model. The general morphology and microstructure of the scaffold model were observed by scanning electron microscopy (SEM). Results The mandibular condyle scaffold made of biomaterials was accordance with the one our computer designed. SEM observation revealed that the model was made of collagen in the cartilage-like layer and calcium phosphate cement/poly (lactic- co-glycolic acid) in the bone-like layer. Conclusion It is feasible to fabricate mandibular condyle scaffold individually by using reverse engineering and rapid prototyping technology.     

Architecture and mineralization of developing trabecular bone in the pig mandibular condyle

Architecture and mineralization are important determinants of trabecular bone quality. To date, no quantitative information is available on changes in trabecular bone architecture and mineralization of newly formed bone during development. Three-dimensional architecture and mineralization of the trabecular bone in the mandibular condyle from six pigs of different developmental ages were investigated with micro-CT. Anteriorly in the condyle, a more advanced state of remodeling was observed than posteriorly, where more active growth takes place. Posteriorly, the bone volume fraction increased with age (r=0.87; P<0.05) by an increase of trabecular thickness (r=0.88; P<0.05), while the number of trabeculae declined (r=-0.86; P<0.05). Anteriorly, despite an increase in trabecular thickness (r=0.97; P<0.001), there was no change in bone volume fraction due to a simultaneous decline in trabecular number (r=-0.84; P<0.05) and increase in trabecular separation (r=0.95; P<0.01). Posteriorly, rods were remodeled into plates as expressed by the structure model index (r=-0.97; P<0.001), whereas anteriorly, a plate-like structure was already present in early stages. The trabecular structure had a clear orientation throughout the developmental process. The global degree of mineralization increased both anteriorly (r=0.86; P<0.05) and posteriorly (r=0.89; P<0.05). We suggest that the degree of mineralization does not depend on the bone volume, but on the thickness of the trabeculae as the mineralized centers of trabeculae were getting larger and more highly mineralized with age compared to their appositional layers. This indicates that besides apposition of new bone material on the surface of trabeculae, the mineralized tissue in their centers still changes and matures.     

Further evidence for the partition of HLA-B14

The minimal sequential absorption of 12 HLA-B14 antisera with B14 positive cells provided 10 antisera that showed a high correlation (r values > 0.8) with the original B14.1 and B14.2 sera of Dewar et al. (1977). The subdivisions defined by the absorbed sera corresponded to the B14 subtype of their immunizing cell. The subtyping of 112 B14 positive individuals showed the frequency of B14.1 to be 33.04%. B14 heterozygous individuals always typed for one but never for both subdivisions. Analysis of a population of 2,044 showed B14.1 to be in linkage disequilibrium with Aw32 and B14.2 with Aw33, Aw30 and A3. It is concluded that B14.1 and B14.2 are distinct antigens which, in the population tested, comprise the entire specificity of HLA-B14.     

Influence of food consistency on growth and morphology of the mandibular condyle

The objective of this study was to determine if variation in the shape and mineralization of the mandibular condyle are the result of natural adaptation in response to different functional loading demands. Eight female Kuni Kuni piglets were randomly assigned to two groups of four, receiving either a soft or hard diet. Each animal was given three separate doses of vital stains intravenously at set time points during the study. At 8.5 months, animals were euthanized and temporomandibular joints (TMJs) were excised. Histological analysis was used to measure the amount of new bone deposition in the anterior, central, and posterior regions of the mandibular condyle. Backscatter electron (BSE) imaging was used as a semiquantitative estimate of bone mineralization in these two diet groups. Histology revealed that the degree of new bone deposition in the hard-diet group was significantly (n = 4, P < 0.001, paired t-test) higher than that of the soft-diet group. Also, the majority (87%) of animals fed a hard diet tended to show greater new bone deposition on the leftside in comparison to the right, indicating a chewing preference for the left side. In both groups, the degree of new bone deposition was significantly (P < 0.01) higher in the posterior area than in other regions. BSE imaging corroborated basic histology results, with significantly (P < 0.01) higher mineralization levels detected in the hard-diet group. These findings indicate that diet consistency has a small but significant effect on the rate of bone deposition in the mandibular condyle.