摘要:

AbstractA detailed redescription of the mechanically interacting structural elements of the lingual apparatus of the domestic chicken,Gallus gallus, revealed the functional and constructional role of organized connective tissue (i.e., ligaments and fasciae) as structural elements that ensure the proper biomechanical interactions among the various structures within the lingual apparatus (e.g., cartilaginous and bony skeletal elements, muscles, salivary glands, epithelial structures). Fasciae, together with extrinsic muscles, also connect the lingual apparatus to the other components of the feeding apparatus, such as the skull, jaw apparatus, and larynx. For example, the hyoid apparatus is attached to the skull by a sheath‐like fascia (F. vaginalis), the internal structure of which is described here for the first time. Thus, the hyoid suspension in birds differs fundamentally from that in mammals.This study is the first to examine all biomechanically functioning structural elements that are part of the galliform lingual apparatus in a systematic and comprehensive manner. It also provides a set of novel characters that may be useful for future comparative studies in evolutionary and functional morpholog

ISSN:0002-9106    

DOI:10.1002/aja.1001860302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe lengths of several neck muscles and tendons and the length, width, and height of the cervical vertebrae and some additional distances were measured in the chicken in six post‐hatching ontogenetic stages and adults. Each vertebra is characterized by a unique combination of growth rates. All increase most in length. Cranial and caudal width as well as height decreases relative to length during ontogeny. When the long dorsal neck muscles are assumed to provide the support for the weight of the head and half of the weight of the neck, the neck system evidently develops according to McMahon's elastic similarity theory. The assumption is justified also because the weights of head and neck together appeared to scale as predicted by elastic similarity. Short neck muscles show negative and tendons positive allometric growth, and long neck muscles grow isometrically relative to neck length. This growth pattern of the muscles and tendons is a direct consequence of the geometric relations of the different growth rates of the vertebra

ISSN:0002-9106    

DOI:10.1002/aja.1001860303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractAll‐trans‐retinoic acid induced 2 types of disorganized neuroepithelium, localized and continuous, in the exencephaly of 9‐day‐old mouse embryos exposed to 60 or 40 mg/kg for 27 to 30 hr in utero. The localized effect appeared as a protuberance in the wall of the telencephalon and thick neural folds in the mesencephalon with the discontinuity of the apical terminal sheet. The continuous disorganization was seen from the olfactory placode to the myelencephalon with rosettes of cells and many dense bodies in the neuroepithelium. Ultrastructurally, cells in the localized disorganizations showed swelling of Golgi complexes, coated vesicles, and rough endoplasmic reticulum resulting in degeneration. The continuous disorganizations consisted of undifferentiated homogeneous cells in which the nuclei exhibited expansion of nucleolar granular portions and coagulated heterochromatin, and cytoplasm showed monosomal dispersion. In both types of disorganized neuroepithelium, junctional complexes were seen focally at the apical side or apical processes of the rosette, with few or no microfilament bundles. A layer of microfilaments at the base of the neuroepithelial cells in controls, just above the basal lamina, was not present in the monosome dispersed cytoplasm. In the neuroepithelium of controls, one phagosome was seen in the perinuclear region in 0.8% of the cells examined, whereas in the experimental neuroepithelium 2 or more phagosomes were seen in a cell, and phagocytosis occurred by pseudopods. These findings suggest that all‐trans‐retinoic acid induces not only cytotoxicity but also dedifferentiation in the neuroepithelial cells leading to more cell death, which activates the phagocytosis. These lesions in the neuroepithelium may be a cause of

ISSN:0002-9106    

DOI:10.1002/aja.1001860304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractRecent studies have indicated that pulmonary intravascular macrophages (PIMs) are a resident cell population which in structure and function resemble mature macrophages of the mononuclear phagocyte system (MPS) in various domestic species, particularly the ruminants. The ultrastructural features of PIMs of the goat and calf lungs were studied by using vascular perfusion and direct airway instillation of fixatives. Staining with tannic acid as a component of paraformaldehyde‐glutaraldehyde‐based fixative revealed the presence of an electron‐dense coat on the surface of the cell membrane of the PIMs. The surface coat disappeared after heparin infusion and after enzymatic digestion with lipolytic lipase, suggesting that the surface coat was predominantly lipoprotein in nature. The lipoprotein coat was organized in the form of a linear chain of spherical globules with a consistent periodicity created by the intervening translucent space between individual globules. The surface coat was separated from the outer‐leaflet of the cell membrane by an empty space measuring 35–39 nm in width. PIMs possessed a significant number of coated pits and coated vesicles, the cell organelles of receptor‐mediated endocytosis of lipoproteins. In concurrence with the coated pits and vesicles, microtubules, multivesicular bodies, and lipoprotein‐positive vesicles were also observed. It is conceivable that PIMs are involved in lipid metabolism and are the major source of vasoactive substances, which significantly influence both the dynamics of pulmonary circulation and the surfactant turnover of the

ISSN:0002-9106    

DOI:10.1002/aja.1001860305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractPosthatching differentiation of arteriovenous anastomoses (AVAs) and the effect of heat exposure (38°C) and cold acclimation (2–3°C) on AVA density were studied in naked skin areas (eyelids, comb, wattles) of chickens. The AVAs were identifiable in the newly hatched chick, but they were extremely simple. The number of cell layers in the wall of the AVAs increased from two at hatching to four to five in the 5‐month‐old chickens. The density of the AVAs increased significantly during posthatching maturation. Cold acclimation of the chickens increased the density of AVAs by a factor of 2.1–3.2. Daily heat exposure also increased the density of AVAs significantly in the eyelids but had no effect in the other skin areas. Heat and cold had only minor effect on the vascularity of the skin; the only significant change recorded was a slight increase in the number of blood vessels in the wattles of the cold‐acclimat

ISSN:0002-9106    

DOI:10.1002/aja.1001860306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe present study compares the morphology of the nasal conchae and the relative development (i.e., surface area and neurosensory cell number) of the olfactory epithelium between four species of shrews occupying different ecotopes (Blarina brevicauda, Sorex cinereus, S. fumeus, S. palustris). The number of olfactory cells was corrected for split cell error. Data were analyzed by using size indices based on the allometric method. The convoluted shape of the maxilloturbinal inBlarina, with large respiratory epithelial surface area, could not be related with certainty to the subterranean ecotope. From the comparison between Soricinae and Crocidurinae, one major difference concerned the shape and attachment of ectoturbinal 3.Differences in the relative development of the olfactory organ are discussed with regard to differences in the use of chemical signals. The semi‐fossorialB. brevicauda, with the more developed olfactory organ, is reported to possess more scent‐glands and to manifest active scent‐marking behaviors and fecal deposits associated with territoriality. The two terrestrial species,S. cinereusandS. fumeus, have olfactory epithelia showing an intermediate development. Published accounts of fewer scent‐glands and a lack of active scent‐marking behavior indicate a lesser use of olfactory communication in these two species where mutual avoidance seems the rule. Indication of an even more reduced use of olfactory signals in social interactions by the semiaquaticS. palustrisis suggested by its least‐developed olfactory epithelium. The comparison between Soricinae and Crocidurinae supports a relationship between the development of the olfactory organ and the relative use of olfactory communication known to occur in social i

ISSN:0002-9106    

DOI:10.1002/aja.1001860307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractA component of the basal plate which has a plywood‐like organization similar to that of the elasmoid scales of teleosts is described in the scales ofPolypterus senegalusfor the first time. The origin and development of this structure is studied in young (50–117 mm, standard length) and adult (225 and 240 mm) specimens using light and electron microscopy. In 50 mm fish, the scales are imbricated and composed mainly of a succession of orthogonal collagen layers forming a plywood‐like structure, the isopedin. The outer surface of the scale is ornamented locally by irregular patches of collagenous material. The layers are not mineralized, whereas the superficial patches are well calcified. The isopedin thickens until it has 12–15 layers and then stops growing (88 mm fish). It mineralizes irregularly from its upper part, and two vascular regions, surrounded by woven‐fibered osseous material, form on the outer and deeper surfaces of the isopedin. These regions thicken while the vascular canals close by centripetal deposition of parallel‐fibered osseous tissue. The outer region is the superficial part of the mature scale (called here osteodentin), which is covered by the ganoine deposited by the epidermal cells. The deeper part constitutes the definitive basal plate, composed of parallel‐fibered osseous tissue. The results show (1) that the young ganoid scales ofPolypterus senegalushave a structure similar to that of typical elasmoid scales; and (2) that the isopedin structure does not change during ontogeny and so represents a permanent record of the first ontogenetic stages. The phylogenetic implication of these results is that the elasmoid scales of teleosts arose by a process of p

ISSN:0002-9106    

DOI:10.1002/aja.1001860308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001860301

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY