Insulin-like growth factor-I stimulates acromegaly-like specific mandibular enlargement in rats.

To help us investigate the time course of mandibular enlargement in acromegaly or acrogiantism to determine the most suitable period for occlusal treatment in this disease, our aim was to develop a rat model of acromegaly (acrogiantism). In this study, prominent mandibular enlargement was induced by continuous subcutaneous infusion of human recombinant insulin-like growth factor-I (IGF-I) (640 microg/day) in 10-week-old male rats for 4 weeks (n = 6); the control sham-operated group was injected with saline alone (n = 6). Circulating human IGF-I was clearly detectable in the IGF-I group during the four-week administration period, while endogenous rat IGF-I levels decreased. Total IGF-I (human + rat) increased significantly during administration, returning to control levels afterwards. The length of every bone examined (mandible, maxilla, and femur) showed a significant increase compared to control rats, especially the mandible. Although the mandible did not continue to grow after discontinuation of IGF-I administration, it did not return to control size, unlike the maxilla and femur, and disharmonious jaw size (between maxilla and mandible) persisted even after circulating IGF-I levels normalized. These findings in our rat model suggest that mandibular occlusal treatment should only be considered for acromegalic (acrogiantic) patients after serum IGF-I levels have normalized and bone growth has ceased.     

Morphological and histopathological changes in tongues of experimentally developed acromegaly-like rats.

An acromegaly-like rat model recently developed by exogenous administration of insulin-like growth factor I (IGF-I) was used to investigate morphological and histopathological tongue changes and clarify whether the changes were reversible. Human recombinant IGF-I (640 microg/day) was continuously subcutaneously infused into ten-week-old male rats for four weeks (IGF-I group; n = 6). Control sham-operated animals were injected saline alone (control group; n = 6). Rats were sacrificed immediately on ending administration at the age of fourteen weeks. Another 12 rats (6 from each group) were housed for an additional four weeks after administration ended. Total IGF-I (human + rat) increased significantly during administration, returning to control levels afterwards. Tongue weights significantly increased with histopathological changes present (increases in the muscle-bundle width, spaces between muscle-bundles and epithelium thickness) in the IGF-I group compared to control rats. Tongue size returned to control levels after discontinuation of IGF-I administration. These findings suggest that the characteristic tongue enlargement was developed experimentally in our acromegaly-like rat model, and that such morphological and histopathological tongue changes are reversible on normalization of circulating IGF-I levels.     

非诱导脂肪干细胞膜片复合PRF修复兔髁状突软骨缺损

目的:探索非诱导ADSCs膜片/PRF复合植入物修复兔子下颌骨髁状突软骨缺损的可行性及效果。方法:选取36只3月龄新西兰雄性大白兔,随机分为3个组即ADSCs膜片/PRF组、PRF组、空白对照组,在3%戊巴比妥钠麻醉下解剖暴露出髁状突关节面并用裂钻分别在双侧髁状突软骨面上制备一3 mm直径、3 mm深的髁突表面软骨缺损区,按实验设计每个分组分别填入相应的植入物。分别在术后4周、8周、12周处死相应时间点的动物采集髁突标本,标本进行大体及组织学检查比较。结果:术后12周时空白对照组的下颌髁状突软骨缺损未能修复,PRF组有少量不规则、不连续的软骨形成,ADSCs膜片/PRF组的修复效果较好,表面软骨接近正常纤维软骨,与周围软骨连续性较好。组织学染色也显示ADSCs膜片/PRF组优于PRF组和空白对照组。结论:证明了ADSCs膜片/PRF复合物修复髁状突软骨缺损的可行性。     

FGFR2功能增强对小鼠下颌骨髁突发育影响

成纤维细胞生长因子受体2(Fibroblast growth factor receptor, FGFR2)是参与调控骨骼发育的重要分子,在调控软骨内成骨过程中发挥着重要作用。为了探讨FGFR2功能增强对小鼠下颌骨髁突生长发育的影响,文章以FGFR2功能增强型点突变(Fgfr2^+/S252W)小鼠为研究对象,采用番红固绿染色研究Fgfr2^+/S252W小鼠下颌骨髁突不同生长发育阶段的组织形态;利用免疫细胞化学染色和实时荧光定量PCR方法检测X型胶原(Col X)在3周龄小鼠髁突肥大软骨细胞中的表达。结果显示,1周龄、3周龄和6周龄突变型小鼠下颌骨髁突的软骨细胞层宽度都比同窝野生型窄,钙化软骨细胞层退化时间早,骨小梁钙化绿染程度深;Col X在突变型小鼠下颌骨髁突的表达高于同窝野生型小鼠(P<0.001)。结果表明,FGFR2功能增强可导致小鼠下颌骨髁突软骨层组织形态异常,抑制髁突软骨内成骨,从而导致下颌骨髁突发育畸形。     

An in situ hybridization study of the insulin-like growth factor system in developing condylar cartilage of the fetal mouse mandible

The objective of this study was to investigate the involvement of the insulin-like growth factor (IGF) system in the developing mandibular condylar cartilage and temporomandibular joint (TMJ). Fetal mice at embryonic day (E) 13.0-18.5 were used for in situ hybridization studies using [35S]-labeled RNA probes for IGF-I, IGF-II, IGF-I receptor (-IR), and IGF binding proteins (-BPs). At E13.0, IGF-I and IGF-II mRNA were expressed in the mesenchyme around the mandibular bone, but IGF-IR mRNA was not expressed within the bone. At E14.0, IGF-I and IGF-II mRNA were expressed in the outer layer of the condylar anlage, and IGF-IR mRNA was first detected within the condylar anlage, suggesting that the presence of IGF-IR mRNA in an IGF-rich environment triggers the initial formation of the condylar cartilage. IGFBP-4 mRNA was expressed in the anlagen of the articular disc and lower joint cavity from E15.0 to 18.5. When the upper joint cavity was formed at E18.5, IGFBP-4 mRNA expression was reduced in the fibrous mesenchymal tissue facing the upper joint cavity. Enhanced IGFBP-2 mRNA expression was first recognized in the anlagen of both the articular disc and lower joint cavity at E16.0 and continued expression in these tissues as well as in the fibrous mesenchymal tissue facing the upper joint cavity was observed at E18.5. IGFBP-5 mRNA was continuously expressed in the outer layer of the perichondrium/fibrous cell layer in the developing mandibular condyle. These findings suggest that the IGF system is involved in the formation of the condylar cartilage as well as in the TMJ.     

A biomechanical analysis of mandibular scaling in old world monkeys

Scaling of mandibular dimensions in male Old World monkeys was investigated. Mandibular condyle length, width, and area were regressed separately against body mass and mandibular length for a total of 14 species of Cercopithecoids. Scaling of mandibular depth and width against both body mass and mandibular length were also investigated. When results of regression analysis using the two different independent variables (body mass and mandibular length) were compared, there were significant pattern differences in scaling of cercopithecines versus colobines. Compared to body mass, male cercopithecines had relatively large mandibles (length, width, and depth) and also relatively large condyles (length, width, and area). However, compared to mandibular length, cercopithecines had relatively transversely thin and shallow mandibles and relatively narrow condyles. It is shown that a “biomechanical” interpretation of mandibular scaling patterns against body mass in Old World monkeys demonstrates only that cercopithecines have prognathic faces, an already well-known and well-documented condition. When the biomechanical effects of prognathic faces are controlled for (by scaling against mandibular length), it is shown that cercopithecines possess special adaptations in condyle length while colobines possess special adaptations in condyle width and mandibular depth and width. These results clearly demonstrate the importance of selecting a relevant reference variable in scaling studies where biomechanical interpretations are attempted.     

In vivo effects of tunicamycin on chondrocytes of rat mandibular condyles as revealed by lectin cytochemistry

Summary The in vivo effects of tunicamycin on the glycosylation of proteoglycans and link protein in rat mandibular condylar chondrocytes were studied by ultrastructural lectin histochemistry. The binding of wheatgerm agglutinin was shown by using anti-lectin antibody followed by protein A-gold complex. In normal rats, wheat-germ agglutinin labeling was restricted to trans cisternae and vacuoles of the Golgi complex, whereas it was observed in neither the cis region of the Golgi complex nor in the rough endoplasmic reticulum. By 3 h after the drug administration, wheat-germ agglutinin binding sites on the disorganized Golgi vacuoles were dramatically reduced in number. At 6 h after the drug administration, the lectin binding sites on the Golgi vacuoles were restored. These results demonstrate that the in vivo use of tunicamycin in combination with histochemical analysis using lectin probes is of significant value for the study of protein glycosylation in chondrocytes of the rat mandibular condyle.     

Mandibular condylar growth alterations after unilateral partial facial paralysis: an experimental study in the rabbit.

In a previous study in the rabbit, the authors defined the macroscopic growth alterations after unilateral partial facial paralysis. Dry skull measurements revealed a reduced premaxillary, maxillary, mandibular, and anterior corpus length with a simultaneous increase in mandibular ramal height on the paralyzed side. The authors hypothesize that these mandibular growth alterations are, among others, caused by alterations in condylar growth activity and that an altered occlusal relationship may be involved in the adaptive condylar growth response after facial paralysis.A total of 84 New Zealand White rabbits were used for this study. The animals were randomly assigned to either a control group that was not operated on (n = 28), a group that underwent a sham-operation (n = 28), or an experimental group (n = 28). In the sham-operation group, the facial nerve was dissected as in the experimental group but was left intact. In the experimental group, a left-side partial facial paralysis involving the midfacial muscles was induced by an operation at the age of 12 days. After different follow-up time intervals of 3.5, 7, 14, 21, 28, 42, and 56 days, four control, four sham-operation, and four experimental animals (all randomly selected) were killed for histomorphometric measurements of the left control and sham condyles and the left-side and right-side experimental condyles.No significant differences between the control and sham-operation groups were found. The other results revealed that shortly after the paralysis in the experimental group, as compared with the controls, a decrease in condylar growth activity was seen before a catch-up increase in activity, as expressed by the time-sequenced decrease and increase in the height of the functional and hypertrophic chondroblast layer. The response on the right side was analogous, though less intense.It is suggested that the mandibular ramal growth alterations might be the result of a chain of adaptations involving the lateral pterygoid muscle and the condylar growth activity. The unilaterally restricted length increment of the maxillary snout, as a result of the loss of tensile forces caused by paralysis of the midfacial musculature, necessitated an adaptation in the position of the mandible to maintain a normal occlusal relationship. Subsequently, the function of muscles involved or influenced by an altered mandibular position, such as the lateral pterygoid muscle, were changed. These altered muscle activities induced condylar growth adaptations, which in turn explained the alterations in mandibular ramal growth.     

Changes in mechanical properties of bone within the mandibular condyle with age

The purpose of the study was to compare indentation modulus (IM) and hardness of condylar bone in young and adult dogs. In addition we desired to examine histologic sections for bone formation activity in the two groups. Mandibular condyles were obtained from adult (1- to 2-year-old) and young (approximately 5-m old) dogs. Two sections/condyle were obtained and one was processed for histomorphometry and the other for mechanical analyses. Indents were made on moist condylar trabecular bone to a depth of 500 nm at a loading rate of 10 nm/s using a custom-made hydration system to obtain IM and hardness. Histomorphometric analyses measured the bone volume/total volume (BV/TV%) and ratio of labeled to unlabeled bone within the condyle. Data were analyzed using a repeated-measures factorial analysis of variance and Tukey-Kramer method. Overall, the IM of the adult condyles (10.0+/-3.4 GPa, Mean+/-SD) were significantly (P<0.0001) higher than in young dogs (5.6+/-2.6 GPa). There was a greater bone mass in the young (60.2%) versus the adult condyles (42%). Also, significantly more labeled bone in the young (66.1%) condylar bone suggested higher bone forming activity than in adult condyles (27.5%). With age there is a change in mass and material properties in the trabecular bone of the mandibular condyle in dogs.     

Role of Articular Disc in Condylar Regeneration of the Mandible

The articular disc in the temporomandibular joint plays an important role in mandibular growth. Functional appliances induce regeneration of the condyle even after condylectomy. The aim of this study was to examine the role of the articular disc in regeneration of the condyle after unilateral condylectomy with use of a functional appliance in growing rats. Fifty growing rats were subjected to unilateral condylectomy and then half of them underwent discectomy. The functional appliance was applied to half of the rats in each group to induce regeneration of the condyle. Four and eight weeks later, morphometric and histologic analyses of the mandible were performed. Regeneration of the condyle was demonstrated in the two condylectomy groups. In the condylectomy+appliance group, the shape and cartilage of the condyle were equivalent to a normal condyle. However, regeneration of the condyle was not observed in the two discectomy groups even with the use of the functional appliance. The articular disc appears to be crucial in the regeneration of a damaged condyle, suggesting that defects or damage to the articular disc may influence mandibular growth and regeneration or repair of the condyle.     

Collagen I and II mRNA distribution in the rat temporomandibular joint region during growth

The distribution of type I and II collagen synthesis in the temporomandibular joint (TMJ) area of 1- to 28-day-old rats was studied after hybridization with probes to pro alpha1(I) and pro alpha1(II) collagen mRNA, and stain intensity through the various cartilaginous zones of the mandibular condyle and other areas of TMJ was assessed. The pro alpha(I) collagen mRNA was detected in the perichondrium/periosteum, in the fibrous and undifferentiated cell layers of the mandibular condyle, in the articular disc, and in all bone structures and muscles. The pro alpha1(II) collagen mRNA was found in the condylar cartilage and the articular fossa. Intensity in the condyle was highest in the chondroblastic layer and decreased towards the lower hypertrophic layer. In the condylar cartilage of the 21- to 28-day-old rats the chondroblastic cell zone was relatively narrow compared with the younger animals, whereas the reverse seems to be the case in the cartilage of the articular fossa. Changes in the pro alpha1(II) collagen mRNA were observed in the osseochondral junction area of the primary spongiosa, in that at the age of 5 days intense staining was found, whereas no staining was observed by 14 days. In the mineralizing zone, however, the majority of osteoblastic cells gave a positive signal with the pro alpha1(I) collagen probe. In conclusion, type II collagen synthesis of the mandibular condyle is restricted to its upper area. This differs from the long bone epiphyseal plate, where this type of collagen is produced virtually throughout the cartilage. Type II collagen synthesis of the fossal cartilage seems to increase as a function of age.     

Correction of unilateral coronal synostosis leads to resolution of mandibular asymmetry in rabbits

Mandibular dysmorphology in unilateral coronal synostosis has been recognized clinically. In patients with unilateral coronal synostosis, the chin point deviates away from the affected side. To investigate whether this mandibular asymmetry resolves after correction of unilateral coronal synostosis, familial nonsyndromic rabbits were used. Rabbits with unilateral coronal synostosis that underwent "correction" with resection of the affected suture were compared with "uncorrected" rabbits with unilateral coronal synostosis and normal, wild-type rabbits (n = 36; three equal groups of 12). Serial lateral cephalograms obtained at 10, 25, 42, and 84 days showed no asymmetries in wild-type rabbits and progressive asymmetries in the ramal height and mandibular length in uncorrected unilateral coronal synostosis rabbits. However, in corrected unilateral coronal synostosis rabbits, existing asymmetries at 10 and 25 days improved by 42 days and were not seen by maturity, at 84 days. In dry, mature, mandibular specimens, wild-type rabbits showed equal side-to-side measurements and uncorrected unilateral coronal synostosis rabbits showed the following on the affected side: longer ramal height (15 percent), shorter ramal width (13 percent), longer body height (10 percent), and shorter body width (13 percent). By contrast, the corrected unilateral coronal synostosis specimens showed no side-to-side differences in 10 of 11. There were no asymmetries in condylar shape or condylar volume in any of the three groups. Cranial base measurements showed asymmetries of the uncorrected unilateral coronal synostosis specimens that were consistent with an anteriorly positioned glenoid fossa on the affected side. However, only one of 11 corrected unilateral coronal synostosis specimens showed similar cranial base asymmetries. The data showed that mandibular asymmetries in nonsyndromic, familial rabbits with unilateral coronal synostosis are progressive with growth but improve after correction of synostosis.     

Load application induces changes in the expression levels of Sox-9, FGFR-3 and VEGF in condylar chondrocytes

Experimental and clinical observations have proven the modulatory effects of mechanical loading on the development and maintenance of cartilage architecture. Here we examined the involvement of Sox-9, FGFR-3 and VEGF (pivotal factors controlling cartilage development and growth) in the mechano-transduction pathway of mandibular condylar cartilage by changing the dynamics of the transmitted load via changes in food hardness. To this end, condyle cartilage tissue of rats fed with hard or soft food was analyzed immunohistochemically at various time points. Our findings demonstrate that different mechanical loading conditions in condylar chondrocytes trigger differentiation-/maturation-related processes by affecting the expression levels of these factors, ultimately influencing condylar cartilage growth.     

The significance of a differential distribution of alkaline phosphatase in the perichondrium of the mandibular condylar cartilage in the wistar albino rat

Summary The aim of the present investigation has been to further study an incidentally observed rare distribution of alkaline phosphatase in the covering of the mandibular condyle. It was felt that this phenomenon might be related to the necessary interaction between the bony and the cartilaginous condylar head during the transformative growth movements of the condylar process.The study has been based on histomorphological and histochemical observations on frontal and sagittal sections of mandibular condyles from rats between 10 and 21 days of age. As regards the bony condylar head which is oval with its long axis in the antero-posterior direction the observations showed that this structure during growth is transformed in a superior, posterior and medial direction. This involves differential resorption on the surfaces in the anterior part and differential apposition on the surfaces in the posterior part.As regards the cartilaginous condylar head, the observations showed that its shape in the frontal plane changes from triangular in the anterior part to rectangular in the posterior part. Alkaline phosphatase reaction in its perichondrium always reaches a higher level medially than laterally.General observations of perichondrial alkaline phosphatase reaction were applied to the distribution of the enzyme in the perichondrium of the mandibular condyle. These data suggest that as the condylar cartilage grows medially, it becomes narrower anteriorly and broader posteriorly.     

口腔内入路行髁突高位骨折复位固定的临床效果

目的：探讨采用口腔内入路手术复位固定方法治疗下颌骨髁突颈骨折患者的临床效果。方法：将我院收治的20例下颌骨髁突颈骨折患者均使用口腔内入路手术复位固定方法治疗,将患者的骨折片与升支后缘骨块进行手术复位固定,并于原手术切口行回植,重建患者的下颌关节。结果：治疗后咬合关系异常者1例,开口范围限制者0例,关节疼痛者1例,均少于治疗前均为20例;治疗后关节间隙缩小者1例,髁突骨折块形状异常者1例,均少于治疗前均为20例。治疗后髁突稳定者19例,多于治疗前的1例。结论：髁突骨折治疗手术各有优缺点,采用口腔内入路手术复位固定方法治疗髁突高位骨折患者,虽然手术操作难度大,但能较好地克服了术后患者外部皮肤瘢痕明显的问题,有利于保护患者面部神经,提高患者治疗质量水平,值得临床上推广与进一步研究。     

Factors influencing the anterior component of occlusal force

We hypothesized that the anterior component of occlusal force (ACF) generated by mandibular molars was a function of molar inclination, height of the transverse condylar axis above the occlusal plane, steepness of the occlusal plane, gape, molar root dimensions, interproximal tooth contact force when not biting, and bite force. Our research aim was to identify those biomechanical factors which determine ACF. Mandibular second molars were axially loaded with a 90 N force (10 mm second molar gape) in 15 subjects, and the resulting ACF was measured at the mandibular first molar-second premolar contact using a recording technique based on interproximal frictional forces. Morphologic measurements were obtained from lateral cephalometric radiographs of each subject and included: Frankfort mandibular plane angle, occlusal plane angle, angles formed by the longitudinal axis of the second molar and the occlusal and mandibular planes, perpendicular distance from the top of the condyle to the occlusal plane, and second molar root width and root length. For ten subjects, ACF resulting from axial loads of 50, 100, 150, and 200 N was measured. For ten subjects, ACF resulting from an axial load of 50 N and second molar gapes of 10 mm, 14 mm, 18 mm, and 22 mm were measured. ACF increased with increasing gape and increased proportionally to increasing bite force. Correlation and stepwise regression analyses revealed that ACF varies with interproximal tooth contact force when not biting (contact ‘tightness’) and molar root width (model R² = 0.71, p < 0.01). The hypothesis that ACF is a function of bite force, gape, molar root width, and interproximal contact tightness has been supported, and the hypothesis that ACF is a function of molar inclination, occlusal plane steepness, condylar axis height, and root length was rejected.     

Parathyroid hormone promotes cartilage healing after free reduction of mandibular condylar fractures by upregulating Sox9

After high fractures of the mandibular condyle, the insufficient blood supply to the condyle often leads to poor bone and cartilage repair ability and poor clinical outcome. Parathyroid hormone (PTH) can promote the bone formation and mineralization of mandibular fracture, but its effects on cartilage healing after the free reduction and internal fixation of high fractures of the mandibular condyle are unknown. In this study, a rabbit model of free reduction and internal fixation of high fractures of the mandibular condyle was established, and the effects and mechanisms of PTH on condylar cartilage healing were explored. Forty-eight specific-pathogen-free (SPF) grade rabbits were randomly divided into two groups. In the experimental group, PTH was injected subcutaneously at 20 µg/kg (PTH (1–34)) every other day, and in the control group, PTH was replaced with 1 ml saline. The healing cartilages were assessed at postoperative days 7, 14, 21, and 28. Observation of gross specimens, hematoxylin eosin staining and Safranin O/fast green staining found that every-other-day subcutaneous injection of PTH at 20 µg/kg promoted healing of condylar cartilage and subchondral osteogenesis in the fracture site. Immunohistochemistry and polymerase chain reaction showed that PTH significantly upregulated the chondrogenic genes Sox9 and Col2a1 in the cartilage fracture site within 7–21 postoperative days in the experimental group than those in the control group, while it downregulated the cartilage inflammation gene matrix metalloproteinase-13 and chondrocyte terminal differentiation gene ColX. In summary, exogenous PTH can stimulate the formation of cartilage matrix by triggering Sox9 expression at the early stage of cartilage healing, and it provides a potential therapeutic protocol for high fractures of the mandibular condyle.     

Bilan scintigraphique osseux d’une hypercondylie unilatérale

A 10-year-old girl with unilateral condylar hyperplasia was referred to our department for a bone scan. We describe the role of the bone scan in this condition. Unilateral condylar hyperplasia is a rare disease of the mandibular condyle cartilage growth leading to facial deformity. Bone scan demonstrates the active or inactive nature of condylar hyperplasia and orients therapy. A planar bone scan completed by single-photon emission computed tomography (SPECT) combined with CT was performed. Increased uptake of the left mandibular condyle, particularly well demonstrated on SPECT images, was seen. This was confirmed by relative quantification and helped decision making to surgical treatment.     

Size and shape of the mandibular condyle in primates

The relationships between the size of the articular surface of the mandibular condyle and masticatory muscle size, tooth size, diet, and biomechanical variables associated with mastication were studied by taking 12 measurements on skulls of 253 adult female anthropoid primates, including three to ten specimens from each of 32 species. In regressions of condylar length, width, or area against body weight, logarithmic transformations substantially improve the fit of the equations compared with untransformed data. There is a strong relationship between condylar measurements and body weight, with all correlations being .94 or higher. The slopes of the allometric regressions of length, width, and area of the condylar head indicate slight positive allometry with body size. Folivorous primates have smaller condyles than frugivorous primates, and colobines have smaller condyles than cebids, cercopithecines, or hominoids. When colobines are eliminated, the differences between frugivores and folivores are not significant. However, the two species with the relatively largest condyles are Pongo pygmaeus and Cercocebus torquatus, suggesting that there may be a relationship between unusually large condylar dimensions and the ability to crack hard nuts between the teeth. Cranial features having strong positive correlations with condylar dimensions include facial prognathism, maxillary incisor size, maxillary postcanine area, mandibular ramus breadth, and temporal fossa area. These data are interpreted as indicating that relatively large condyles are associated with relatively large masticatory muscles, relatively inefficient mandibular biomechanics, and a large dentition. These relationships support the growing evidence that the temporomandibular joint is a stress-bearing joint in normal function.     

短尾猴下颌骨的性二型

对30个成年短尾猴下颌骨的8个有关变量作了性二型研究。单因子分析说明,8个变量均达到了显著差异水平。判别分析得到的第一判别式为:D=-11.013+1.151下颌骨髁长+0.269下颌骨髁宽。当D=-1.271±0.182时,标本为雌性;当D=0.973±0.290时为雄性。雄性下颌骨髁比雌性更长和更宽,且变化较为稳定,可作为种内性别间的鉴别特征。雄性比雌性具有较大咀嚼阻力臂(下颌长),但其他阻力臂则比雌性相对较短。与一些灵长类相同变量的比较说明,短尾猴下颌骨结构与猕猴较为接近,与长尾叶猴则相差甚远。这可反映它们食性和行为方面的亲疏关系。