贵州疣螈骨骼系统的研究

本文运用硬骨-软骨双染色技术对贵州疣螈（Tylototriton kweichowensis）的骨骼系统做了较全面的观察研究，包括头骨、脊柱和前后肢带骨，并对各骨块的形状、位置以及与邻近骨块的关系都作了详细的描述。最后，将贵州疣螈与东方蝾螈、有斑肥螈的骨骼系统进行了比较，为揭示蝾螈科属间演化关系提供一定的依据。     

Elastic properties of the red blood cell membrane that determine echinocyte deformability

The natural biconcave shape of red blood cells (RBC) may be altered by injury or environmental conditions into a spiculated form (echinocyte). An analysis is presented of the effect of such a transformation on the resistance of RBC to entry into capillary sized cylindrical tubes. The analysis accounts for the elasticity of the membrane skeleton in dilation and shear, and the local and nonlocal resistance of the bilayer to bending, the latter corresponding to different area strains in the two leaflets of the bilayer. The shape transformation is assumed to be driven by the equilibrium area difference (A₀, the difference between the equilibrium areas of the bilayer leaflets), which also affects the energy of deformation. The cell shape is approximated by a parametric model. Shape parameters, skeleton shear deformation, and the skeleton density of deformed membrane relative to the skeleton density of undeformed membrane are obtained by minimization of the corresponding thermodynamic potential. Experimentally, A₀ is modified and the corresponding discocyte–echinocyte shape transition obtained by high-pressure aspiration into a narrow pipette, and the deformability of the resulting echinocyte is examined by whole cell aspiration into a larger pipette. We conclude that the deformability of the echinocyte can be accounted for by the mechanical behavior of the normal RBC membrane, where the equilibrium area difference A₀ is modified.     

SMA-1 spectrin has essential roles in epithelial cell sheet morphogenesis in C. elegans

During Caenorhabditis elegans development, the embryo acquires its vermiform shape due to changes in the shape of epithelial cells, a process that requires an apically localized actin cytoskeleton. We show that SMA-1, an ortholog of beta(H)-spectrin required for normal morphogenesis, localizes to the apical membrane of epithelial cells when these cells are rapidly elongating. In spc-1 alpha-spectrin mutants, SMA-1 localizes to the apical membrane but its organization is altered, consistent with the hypothesis these proteins act together to form an apically localized spectrin-based membrane skeleton (SBMS). SMA-1 is required to maintain the association between actin and the apical membrane; sma-1 mutant embryos fail to elongate because actin, which provides the driving force for cell shape change, dissociates from the apical membrane skeleton during morphogenesis. Analysis of sma-1 expression constructs and mutant strains indicates SMA-1 maintains the association between actin and the apical membrane via interactions at its N-terminus and this activity is independent of alpha-spectrin. SMA-1 also preserves dynamic changes in the organization of the apical membrane skeleton. Taken together, our results show the SMA-1 SBMS plays a dynamic role in converting changes in actin organization into changes in epithelial cell shape during C. elegans embryogenesis.     

Vertical mammaplasty

Current criticisms regarding vertical mammaplasty include problems with poor immediate postoperative appearance, nipple-areola complex malposition, and excessive lower pole length. These problems can be avoided by proper patient selection, by utilizing correct concepts of skin design, and by observing correct glandular resection and closure concepts. Vertical mammaplasty also can result in other problems, such as hypertrophic circumareolar scars and lower pole deformities, including notching, boxy shape, infra-areolar depression, and flatness. These problems are also largely avoidable by using correct technique. Several basic concepts described previously have not proven necessary to achieve good results. Abandoning some of these principles has contributed to the ability to establish an aesthetically ideal breast shape intraoperatively as well as to a decrease in morbidity. This includes eliminating liposuction as a major integral component of the procedure, eliminating suturing the gland to the pectoralis muscle, not undermining the lower pole skin, and avoiding overly wide skin resection and tight wound closure that produces significant lower pole distortion in the early postoperative period. An important concept that has proven reliable is to use a "closed" design that does not predetermine the areolar opening whenever circumstances permit. When this is not possible, a modification that utilizes the smallest possible circumference as an open design is better than a large "mosque." These alternatives allow greater flexibility in determining final nipple position and also reduce the risk of hypertrophic circumareolar scars. Important glandular resection concepts include creating pillars that are attached to both the skin and the chest wall; making them of adequate dimension to avoid postoperative lower pole shape problems, such as flattening; resecting closer to the skin lateral to the pillars to avoid a boxy breast shape; and using a drain both to assist in accurately determining the endpoint of resection and to avoid postoperative seromas. Key closure concepts include approximation of the superior surfaces of the pillars at their base to maintain vertical height and thereby prevent lower pole flattening; approximation of the inferior surfaces of the pillars to the base of the breast to prevent notching; and proper management of the vertical incision by restricting the purse-string suture effect to only the inferior portion of the incision, where there may be skin excess present. Inclusion of these concepts leads to predictable and improved aesthetic results in vertical mammaplasty. This allows full realization of the purported advantages of vertical mammaplasty and allows this method to be utilized with a level of confidence similar to that seen with inverted-T techniques.     

Postrhinoplasty "red nose": differential diagnosis and treatment by laser

Prior to anticipated nasal surgery, the nasal and facial skin should be examined for any vascular lesions. The skin type should be ascertained. A history of any prior nasal surgery, particularly on the nasal dorsum, should be noted. If rosacea is a clinical possibility, a trial of 1.5 to 2.0 gm q.d. of tetracycline for 6 to 8 weeks is warranted. If, after rhinoplasty, a diffuse "redness" on the nasal dorsum results and one can exclude other diagnoses, then argon laser therapy should be considered. A 3-mm punch biopsy should be obtained to see whether superficial ectatic vessels are present, a finding that would be indicative of a good result from laser therapy.     

Computer simulation of the hydrostatic skeleton. The physical equivalent, mathematics and application to worm-like forms

The functional principles of a hydrostatic skeleton were combined to obtain a physical model which includes geometry, number and length-tension relationships of the elastic elements in the body wall, internal volume and internal pressure. The model skeleton with pre-set internal volume assumes a certain shape and develops a specific internal pressure in order to minimize the potential energy stored in the elastic elements. This shape is calculated as equilibrium state by using finite element methods and optimization techniques. This model is flexible enough to accommodate different geometries and length-tension-relationships of the elastic elements. Presently, the model is implemented with linear length-tension relationships and certain geometrical restrictions, such as uniform width over the entire animal, and rectangular cross sections; the general case is outlined. First simulations with the "unit-worm" yield stable solutions, i.e. stable shapes for all combinations of parameters tested so far. They define the conditions for bringing all muscles to an optimal operating point. We detected a pressure maximum with increasing volume, assessed the contribution of circular muscles to bending, and determined the shapes of animals with different muscle activations in each body half (Chapman-matrix). We summarize our results by the volume rule and stabilization rule, two simple concepts which predict changes in shape as the result of muscle activation.     

Toward refinement in rhinoplasty

Three interrelated principles can help to achieve nasal refinement: creation of nasal planes, attention to lateral light reflexes, and maintenance of skin sleeve size. These principles are detailed and illustrated in primary and secondary rhinoplasty patients.     

A basis of echinocytosis and stomatocytosis in the disc-sphere transformations of the erythrocyte

A mechanism of erythrocyte shape control has been previously hypothesized in which Band 3, the anion exchange protein, controls the shape. In essence, the mechanism hypothesizes that the membrane skeleton is used to generate different shapes and the alternate influx and efflux of anions mediated by Band 3, which recruit Band 3 to an inward-facing and an outward-facing conformation, contract and relax the skeleton by folding and unfolding spectrin. Spectrin is bound to Band 3 by the intermediary of ankyrin. The mechanism is shown to be consistent with rapid shape deformations of the erythrocyte in blood circulation. We have examined whether the mechanism could provide a basis of echinocytosis and stomatocytosis in disc-sphere transformations of the erythrocyte induced by a wide variety of agents. These agents were classified into four groups: lipids of the bilayer, Donnan equilibrium modifiers, Band 3 anion transport inhibitors and integral membrane protein modifiers. Evidence is presented that the lipids play a secondary function in the control of the erythrocyte shape, as indicated by the mechanism. Two possible functions of the lipids are suggested with respect to the mechanism. Without exception, echinocytogenic and stomatocytogenic Donnan equilibrium modifiers decrease and increase the equilibrium ratio of chloride (Cl-(i)/Cl-(o)), respectively, as predicted by the mechanism. Echinocytosis produced by competitive anion transport inhibitors slowly transported inward by Band 3 and by affinity labels of Band 3 is compatible with the mechanism. Evidence is presented which indicates that echinocytosis and stomatocytosis induced by amphiphilic drugs and detergents occur by inhibition of the Band 3 anion transport. Finally, echinocytosis and stomatocytosis induced by non-covalent and covalent modifiers of integral membrane proteins such as agglutinins and digestive enzymes are consistent with the mechanism.     

An alternate strategy for reducing the large nasal base

The position of the dorsum directly influences the apparent size of the nasal base: the higher the bridge, the smaller the nasal base seems. This powerful optical illusion provides the surgeon with an alternate strategy for creating harmony in the nose with a low, straight dorsum and a disproportionately large nasal base. Instead of reducing the lower nose, the surgeon can augment the upper nose (and make whatever nasal base changes are independently necessary). This alternate strategy limits the amount of nasal skeletal reduction necessary, thereby limiting the potential for postoperative change and soft-tissue distortion and directly increasing the surgeon's control over the result.     

Management of the bulbous nose

"Bulbous nose" is a term patients often use to describe a "ball" on the end of their nose. This ball can be caused by the abnormal anatomy of alar cartilage or by the overlying soft-tissue coverage. The purpose of this article is to analyze the different causes of bulbous noses and their treatment options. An analysis was done based on four decades of experience and long-term follow-up. We included 10 patients for our discussion. The relationship of the tip to the vault must be analyzed, because it can create optical illusions. For instance, a low bridge makes the tip appear larger; therefore, a bulbous nose may be relative. Similarly, excessive narrowing of the nasal base by alar wedges makes the tip appear wider. Intrinsic causes of a bulbous nose include skin, subcutaneous tissue (including the nasal superficial musculoaponeurotic system, ligaments, and fat), and the shape and direction of the individual crus. Nasal skin varies as to volume and ability to contract; therefore, the shape, direction, or divergence of the individual crura cannot undergo unlimited modifications. There are several surgical possibilities for a given problem. Making the diagnosis of the underlying abnormal anatomy is the most important step; then the most appropriate operation can be selected. Struts, sutures, resection, dome division, and/or dorsal augmentation are all viable options for the management of the bulbous nose.     

A model of spectrin as a concertina in the erythrocyte membrane skeleton

To maintain its distinctive biconcave shape, the erythrocyte has a skeleton composed largely of the protein spectrin, which associates closely and exclusively with the cell membrane. Although the membrane skeleton forms through specific protein-protein interactions of defined stoichiometry, it has a flexible structure and organization due to the unusual molecular properties of spectrin. Here we describe these properties and propose a model to account for the extensibility of spectrin and for its organization in the skeleton.     

The behavior of the human erythrocyte as an imperfect osmometer: a hypothesis

The human erythrocyte does not behave as a perfect osmometer that is its volume does not change as predicted with the change of the tonicity of the medium, as if there was a fraction of the cell water not participating in the osmotic exchange. A mechanism of control of the erythrocyte shape has been previously proposed in which Band 3 (AE1), the protein anion exchanger of Cl(-) and HCO(3)(-), plays a central role. Specifically, decrease and increase of the ratio of its outward-facing conformation and inward-facing conformation (Band 3(o)/Band 3(i)) contract and relax the membrane skeleton, thus favoring echinocytosis and stomatocytosis, respectively. The equilibrium Band 3(o)/Band 3(i) ratio is determined by the Donnan equilibrium ratio of anions and protons, increasing with it (r=Cl(i)(-)/Cl(o)(-)=HCO 3(i)(-)/HCO 3(o)(-)=H(o)(+)/H(i)(+)). The Donnan ratio is influenced by the erythrocyte transport and metabolic activities. The volume change of the human erythrocyte alters the skeleton conformation as it is accompanied by a change of the membrane curvature. Thus, the mechanism could be a hypothesis for explaining the behavior of the human erythrocyte as an imperfect osmometer since the Donnan ratio controls the Band 3(o)/Band 3(i) ratio which controls the volume by a control of the degree of contraction or relaxation of the skeleton. Predictions made by the hypothesis on the Ponder's coefficient R' values in the presence of sucrose or Band 3 substrates slowly transported as well as on the participation of Band 3 in the osmotic hemolysis appear to be corroborated by previous observations. If the hypothesis was valid, it would follow that there is a pressure gradient across the erythrocyte membrane. The equilibrium volume is antagonistically determined by the Donnan ratio per se and Band 3. Band 3, rather than the ratio of surface-to-volume, primarily controls the osmotic hemolysis.     

Native ultrastructure of the red cell cytoskeleton by cryo-electron tomography

Erythrocytes possess a spectrin-based cytoskeleton that provides elasticity and mechanical stability necessary to survive the shear forces within the microvasculature. The architecture of this membrane skeleton and the nature of its intermolecular contacts determine the mechanical properties of the skeleton and confer the characteristic biconcave shape of red cells. We have used cryo-electron tomography to evaluate the three-dimensional topology in intact, unexpanded membrane skeletons from mouse erythrocytes frozen in physiological buffer. The tomograms reveal a complex network of spectrin filaments converging at actin-based nodes and a gradual decrease in both the density and the thickness of the network from the center to the edge of the cell. The average contour length of spectrin filaments connecting junctional complexes is 46 ± 15 nm, indicating that the spectrin heterotetramer in the native membrane skeleton is a fraction of its fully extended length (∼190 nm). Higher-order oligomers of spectrin were prevalent, with hexamers and octamers seen between virtually every junctional complex in the network. Based on comparisons with expanded skeletons, we propose that the oligomeric state of spectrin is in a dynamic equilibrium that facilitates remodeling of the network as the cell changes shape in response to shear stress.     

Anatomic variations of the nasolabial fold.

The nasolabial fold varies considerably from person to person. Three main groups may be distinguished: convex, concave, and straight. It is the muscles of smiling that are directly responsible for the shape and depth of the fold, and in their absence of function, as in facial palsy, the nasolabial fold disappears. Cadavers were selected in accordance with the nasolabial fold they presented and were dissected to analyze the difference in underlying anatomy between one fold shape in one cadaver and another fold shape in another. The study demonstrates that the nasolabial fold is the result of a conflict between soft and dynamic tissues of the middle face or an interaction between the skin and fat envelope on one side and the underlying muscles on the other. The greater this conflict, the more excess there is of cheek skin and the more pronounced a nasolabial fold. The mechanism that creates the nasolabial fold and the anatomy of the fold are described in this paper.     

Anatomic reconstruction of the nasal tip cartilages in secondary and reconstructive rhinoplasty

Most techniques for secondary rhinoplasty assume that useful residual remnants of the tip cartilages remain, but frequently the alar cartilages are missing--unilaterally, bilaterally, completely, or incompletely--with loss of the lateral crura, middle crura, and parts of the medial crura. In such severe cases, excision of scar tissue and the residual alar remnants and their replacement with nonanatomic tip grafts have been recommended. Multiple solid, bruised, or crushed cartilage fragments are positioned in a closed pocket or solid shield-shaped grafts are fixed with sutures during an open rhinoplasty. These onlay filler grafts only increase tip projection and definition. Associated tip abnormalities (alar rim notching, columellar retraction, nostril distortion) are not addressed. Problems with graft visibility, an unnatural appearance, or malposition have been noted. Fortunately, techniques useful in reconstructive rhinoplasty can be applied to severe cosmetic secondary deformities. Anatomic cartilage replacements similar in shape, bulk, and position to normal alar cartilages can be fashioned from septal, ear, and rib cartilage, fixed to the residual medial crura and/or a columellar strut, and bent backward to restore the normal skeletal framework of the tip. During an open rhinoplasty, a fabricated and rigid framework is designed to replace the missing medial, middle, or lateral crus of one or both alar cartilages. The entire alar tripod is recreated. These anatomic alar cartilage reconstructive grafts create tip definition and projection, fill the lobule and restore the expected lateral convexity, position the columella and establish columellar length, secure and position the alar rim, and brace the external valve against collapse, support the vestibular lining, and restore a nostril shape. The anatomic form and function of the nasal tip is restored. This technique is recommended when alar cartilages are significantly destroyed or absent in secondary or reconstructive rhinoplasty and the alar remnants are insufficient for repair. Anatomically designed alar cartilage replacements allow an aesthetically structured skeleton to contour the overlying skin envelope. Problems with displacement are minimized by graft fixation. Graft visibility is used to the surgeon's advantage. A rigidly supported framework with a nasal shape can mold a covering forehead flap or the scarred tip skin of a secondary rhinoplasty and create a result that may approach normal. Anatomic alar cartilage reconstructions were used in eight reconstructive and eight secondary rhinoplasties in the last 5 years. Their use in the repair of postrhinoplasty deformities is emphasized.     

Periosteal and endosteal control of bone remodeling under torsional loading.

The shape changes that occur in the mid-diaphysis of a long bone due to adaptive remodeling induced by increasing or decreasing the axial and/or torsional loading of the bone are investigated using a simple model. In this model the mid-diaphysis of a long bone is represented as a hollow thick-walled right-circular cylinder, and different optimal strategies for bone remodeling are considered. It is shown that if such a thick-walled right-circular cylinder capable of surface remodeling is subjected to an axial compressive load and a twisting torque, then the remodeling patterns depend on whether the periosteal surface or the endosteal surface controls the limits of the remodeling process. It is shown that the effect of increasing the torque is always opposite to the effect of increasing the compressive load. Thus, similar remodeling patterns are obtained by increasing one type of loading and decreasing the other. Aside from the restriction of idealized cylindrical geometry, the only assumptions made are that the bone tissue is linearly elastic and that there exists a finite range of remodeling equilibrium stresses. Only those loading situations which maintain the bone in remodeling equilibrium are considered in this work. It follows that the results presented are independent of the specific type of rule governing the temporal evolution of the bone shape, since any such rule applies only in situations where there is active remodeling and, hence, no remodeling equilibrium.     

Functional reconstruction of maxilla with free latissimus dorsi-scapular osteomusculocutaneous flap

Restoration of oral and nasal function together with facial appearance is still challenging in maxillary reconstruction. Use of a composite flap transfer merely to fill the defect results in unsatisfactory functional and aesthetic outcomes. The authors present a reconstructive procedure for complex maxillary defects using the latissimus dorsi-scapular rib osteomusculocutaneous flap. Some modifications for the reconstruction of the nasal cavity and the hard palate contributed to excellent postoperative functions. Five cases of extended maxillary defect were reconstructed using a novel procedure between February of 1997 and October of 2000. The hard palate was reconstructed with a vascularized scapular angle. The infraorbital rim was reconstructed with a vascularized rib if it was required. A prop bone graft, replacing the zygomatic buttress, was added between the infraorbital rim and the hard palate. The latissimus dorsi muscle flap, which was supported by a skeletal framework and obliterated the remaining cavities around the bone grafts, was left exposed into the nasal cavity, and an 8-French (no. 10) nasal airway tube was placed as a stent in the nasal meatus for 3 weeks after surgery. A skin graft was applied on the scapular angle to reconstruct the oral side of the hard palate. If required, facial skin defect was repaired with a latissimus dorsi musculocutaneous flap or scapular flap. No major complications at the recipient or the donor sites occurred postoperatively in any of the five cases. In cases in which the eyeballs were preserved, almost normal facial appearance was obtained and an orbital extirpation case showed an acceptable postoperative appearance. All five patients returned to an unrestricted diet and their speech was assessed as normal by a speech test. Nasal breathing through the re-epithelialized meatus was possible in all cases. The reconstructed nasal cavity was maintained for more than 6 months in all cases and for more than 2 years in one early case. Rhinometry demonstrated normal function, and histologic findings of the re-epithelialized mucosa over the muscle flap in the nasal cavity revealed a nearly normal architecture. This technique simplifies the reconstructive procedure of massive maxillary defects, including those in the lateral wall of the nasal cavity. It also improves the postoperative oral and nasal functions of the patients.     

Sleeve Muscle Actuator: Concept and Prototype Demonstration

This paper presents the concept and prototype demonstration results of a new sleeve muscle actuator, which provides a significantly improved performance through a fundamental structural change to the traditional pneumatic muscle. Specifically, the sleeve muscle incorporates a cylindrical insert to the center of the pneumatic muscle, and thus eliminates the central portion of the internal volume. Through the analysis of the actuation mechanism, it is shown that the sleeve muscle is able to provide a consistent increase of force capacity over the entire range of motion. Furthermore, the sleeve muscle provides a significant energy saving effect, as a result of the reduced internal volume as well as the enhance force capacity. To demonstrate this new concept, a sleeve muscle prototype was designed and fabricated. Experiments conducted on the prototype verified the improvement in the force capacity and demonstrated a significant energy saving effect (20%–37%). Finally, as the future work on this new concept, the paper presents a new robotic elbow design actuated with the proposed sleeve muscle. This unique design is expected to provide a highly compact and powerful actuation approach for robotic systems.     

A polarised population of dynamic microtubules mediates homeostatic length control in animal cells

Because physical form and function are intimately linked, mechanisms that maintain cell shape and size within strict limits are likely to be important for a wide variety of biological processes. However, while intrinsic controls have been found to contribute to the relatively well-defined shape of bacteria and yeast cells, the extent to which individual cells from a multicellular animal control their plastic form remains unclear. Here, using micropatterned lines to limit cell extension to one dimension, we show that cells spread to a characteristic steady-state length that is independent of cell size, pattern width, and cortical actin. Instead, homeostatic length control on lines depends on a population of dynamic microtubules that lead during cell extension, and that are aligned along the long cell axis as the result of interactions of microtubule plus ends with the lateral cell cortex. Similarly, during the development of the zebrafish neural tube, elongated neuroepithelial cells maintain a relatively well-defined length that is independent of cell size but dependent upon oriented microtubules. A simple, quantitative model of cellular extension driven by microtubules recapitulates cell elongation on lines, the steady-state distribution of microtubules, and cell length homeostasis, and predicts the effects of microtubule inhibitors on cell length. Together this experimental and theoretical analysis suggests that microtubule dynamics impose unexpected limits on cell geometry that enable cells to regulate their length. Since cells are the building blocks and architects of tissue morphogenesis, such intrinsically defined limits may be important for development and homeostasis in multicellular organisms.     

Cranial airways and the integration between the inner and outer facial skeleton in humans

The cranial airways are in the center of the human face. Therefore variation in the size and shape of these central craniofacial structures could have important consequences for the surrounding midfacial morphology during development and evolution. Yet such interactions are unclear because one school of thought, based on experimental and developmental evidence, suggests a relative independence (modularity) of these two facial compartments, whereas another one assumes tight morphological integration. This study uses geometric morphometrics of modern humans (N = 263) and 40 three‐dimensional‐landmarks of the skeletal nasopharynx and nasal cavity and outer midfacial skeleton to analyze these questions in terms of modularity. The sizes of all facial compartments were all strongly correlated. Shape integration was high between the cranial airways and the outer midfacial skeleton and between the latter and the anterior airway openings (skeletal regions close to and including piriform aperture). However, no shape integration was detected between outer midface and posterior airway openings (nasopharynx and choanae). Similarly, no integration was detected between posterior and anterior airway openings. This may reflect functional modularization of nasal cavity compartments related to respiratory physiology and differential developmental interactions with the face. Airway size likely relates to the energetics of the organism, whereas airways shape might be more indicative of respiratory physiology and climate. Although this hypothesis should be addressed in future steps, here we suggest that selection on morphofunctional characteristics of the cranial airways could have cascading effects for the variation, development, and evolution of the human face. Am J Phys Anthropol 152:287–293, 2013. © 2013 Wiley Periodicals, Inc.