摘要:

AbstractStructures superficially resembling dictyosomes were present in guinea pig primary spermatocytes and in spermatids in late stages of development. The dictyosome‐like structures (DLS) were composed of 2 to 17 saccules. Each saccule averaged about 20 nm in thickness (membranes plus lumen) and 400 nm in diameter and was separated from adjacent saccules in a stack by an intersaccular space of about 12 nm. Single saccules separated from the DLS were also present. Tubules up to 60 nm in diameter were continuous with the edges of the saccules and sometimes extended for several micrometers into the cytoplasm. The membranes of the tubules appeared similar to the saccule membranes. Some DLS saccules and tubules had coated vesicles attached to them.A distinguishing feature of DLS was the presence of microtubule‐like structures, about 10 nm in diameter, that bridged the inter‐saccular spaces. Some of these bridging structures appeared continuous through one or more saccules. The bridging structures were often arranged in linear arrays or in clusters of three to four.The membranes of the DLS appeared tripartite but stained differently from the membranes of the endoplasmic reticulum or Golgi apparatus. The inner (luminal) leaflet of the tripartite membrane usually appeared discontinuous or globular after fixation in glutaraldehyde‐osmium tetroxide. The DLS could be distinguished from all other cellular components and may represent a new organelle unique to spermato

ISSN:0002-9106    

DOI:10.1002/aja.1001500302

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe purpose of this investigation was: (a) to study the developmental relationships of the temporal muscle and the coronoid process during the critical initial stages of morphogenesis and (b) to correlate the developmental stages of the muscle and the bone with data describing the functioning of the muscles of mastication in utero.The heads of 41 human embryos and fetuses, 6 to 11 weeks, estimated fertilization age, were sectioned and examined under light microscopy. The findings are described in terms of six successive stages, each characterized by a major developmental change occurring during that stage.The data indicate that the temporal and masseter muscle anlagen begin to develop prior to the skeleton to which they ultimately become attached. The coronoid process differentiates subsequently as a discrete entity within the mass of the temporal muscle anlage at an estimated fertilization age of 7 to 7.5 weeks (23–24 mm CRL). At approximately eight weeks of age, the coronoid process unites with the main portion of the mandibular ramus. The findings here presented do not support the conclusion that the coronoid process is self‐differentiating as Washburn (′47) contended. Instead, the development of this feature of the human mandible represents a response that follows the differentiation of the temporal muscle. This conclusion is consistent with the observations drawn from a number of investigations concerning structural and functional development of the

ISSN:0002-9106    

DOI:10.1002/aja.1001500303

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe morphology of the ependymal surface of the rabbit third ventricle was studied following intraventricular injections of an ovulatory dose of synthetic LH‐RH. Identically treated rabbits that received injections of saline, only, served as controls. Animals from both groups were killed 5 minutes and 15 minutes after the injections. The ependyma of the dorsolateral ventricular wall and transitional zone maintained a constant appearance from animal to animal regardless of treatment or time of autopsy. The uniformly non‐ciliated ependyma of the ventrolateral wall and floor (infundibular and mammillary recesses) of the ventricle, however, not only exhibited an appearance quite distinct from either the dorsolateral wall or transitional zone, but also exhibited a transient responsiveness to LH‐RH treatment. In the controls, most ependymal cells of this region bulged conspicuously into the ventricle. Numerous pleomorphic knob‐ of bleb‐like protrusions and occasional microvilli characterized their apical membranes. In contrast, marked changes were seen in the character of the ependymal surface of animals killed five minutes following LH‐RH administration. These changes, which principally took the form of numerous irregular microvillous eruptions of the apical membrane, pervaded the rostrocaudal extent of the infundibular and mammillary recesses. Equivalent regions of the ependymal surface in animals killed 15 minutes after LH‐RH administration, however, were similar to those of the controls. These transient morphological changes observed in the ependymal surface of the ventrolateral wall and floor of the ventricle five minutes after LH‐RH injection may reflect structural modifications associated with absorption of the hormone across the ependyma

ISSN:0002-9106    

DOI:10.1002/aja.1001500304

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

年代:1977

数据来源: WILEY

摘要:

AbstractElectrotonic spread of applied potentials was observed between longitudinal and circular muscle layers of the small intestine with no rectification. Nexal junctions were demonstrated between muscle fibers of each layer. Connective tissue cells bridged between the two muscle layers. These showed structural characteristics of fibrocytes and of interstitial cells. Some nexuses were seen between connective tissue cells and between these cells and muscle fibers of each layer but in most junctions the membranes were 10–18 nm apart. Since connective tissue can serve for electrical conduction between cultured heart cells and since electrical properties of intestinal muscle permit transmission with low degrees of coupling, it is suggested that interstitial cells and fibrocytes may electrically couple longitudinal and circular muscle layers of cat intestin

ISSN:0002-9106    

DOI:10.1002/aja.1001500305

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

年代:1977

数据来源: WILEY

摘要:

AbstractD‐tubocurarine was injected into the air sac of 8‐day chick embryos to prevent movement of the digits of the hind limb. The embryos were paralyzed from the tenth to the eighteenth day, when the experiment was terminated. The immobilization of the flexor digitorum profundus tendons in the tarsus resulted in a loss of specialized structures around and on this tendon, as determined by light and electron microscopy. Specialized areas observed in the normal chick (synovial cavity, fibrocartilaginous area, and elastic vinculum) failed to form, as a result of the paralysis of the digit.Several authors have shown previously that movement is a requirement for the molding and maintenance of joint cavities in vivo, in ovo and in vitro (see text for references). We have shown that movement of the tendon is required to produce a functional tendon apparatus in the embryo and predict that movement is also required for regeneration after inj

ISSN:0002-9106    

DOI:10.1002/aja.1001500306

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe nasal region of 12‐day‐old mouse embryos was examined with the electron microscope to determine whether a surface coat and membrane specializations are involved in epithelial fusion between the medial and lateral nasal swellings. Ruthenium red was used to examine the distribution of the surface coat.Prior to contact, a surface coat is always present over the epithelial linings of the nasal swellings in the region of presumptive fusion, and it is often heavier in the fusing than in the non‐fusing regions. At the point of initial contact, the coat is present as a thin film between touching superficial cells, suggesting that it may mediate epithelial contact.The initial contact between the cells of the medial and lateral nasal swellings is made by short projections from one superficial cell to the surface of an opposing superficial cell. These points of contact then broaden into larger areas until the entire free membranes of opposing superficial cells meet. The contacting membranes, which are separated by a distance of approximately 6–10 nm and show an increased electron‐density, probably provide a firm adhesion between the nasal

ISSN:0002-9106    

DOI:10.1002/aja.1001500307

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

年代:1977

数据来源: WILEY

摘要:

AbstractThe nasal fin is an epithelial seam that develops by fusion between the epithelial linings of the medial and lateral nasal swellings. Shortly after its formation the nasal fin regresses and is replaced by mesenchyme, with exception of its most posterior portion which remains as the bucconasal membrane. Since the regression of the nasal fin plays an important role in the formation of the upper lip and primary palate, the breakdown of the fin was examined with the electron microscope in 12‐day‐old mouse embryos.Shortly before the epithelial linings of the opposing nasal swellings make contact, cell degeneration characterized by condensation and fragmentation occurs in the epithelial linings of the prospective fusion areas. Apparently direct contact between the nasal swellings is not necessary to cause cell death.After fusion has established the nasal fin, epithelial cells continue to degenerate by condensation and fragmentation. Cell degeneration, however, can not account for complete regression of the fin, since many morphologically healthy epithelial cells are always present. Since no indication was found that the surviving epithelial cells transform into mesenchymal cells, it is suggested that they are incorporated into the adjacent epithelial linings of the expanding primitive nasal and oral cavities.The extracellular dense bodies that result from degenerating cells are engulfed by neighboring epithelial cells, in which they form phagocytic vacuoles. Some of these epithelial cells containing numerous cytoplasmic vacuoles appear to transform into large round macrophages.When the acid phosphatase procedure was applied, many heterophagic vacuoles contained a black precipitate, indicating that, after being phagocytosed, the dense fragments are digested by lysosomal enzymes. A similar black precipitate appeared over autophagic vacuo

ISSN:0002-9106    

DOI:10.1002/aja.1001500308

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

年代:1977

数据来源: WILEY

摘要:

AbstractTechniques of quantitative stereology have been utilized to determine the relative volume occupied by the Sertoli cells and germ cells in two particular stages (I and VII) of the cycle of the seminiferous epithelium. Sertoli cell volume ranged from 24% in stage I of the cycle to 32% in stage VII. Early germ cells occupied 3.4% in stage I (spermatogonia) and 8.7% in stage VII (spermatogonia and preleptotene spermatocytes). Pachytene spermatocytes occupied 15% (stage I) and 24% (stage VII) of the total volume of the seminiferous epithelium. In stage I the two generations of spermatids comprised 58% of the total epithelium by volume, whereas in stage VII, after spermiation, the acrosome phase spermatids occupied 35% of the total seminiferous epithelial volume.

ISSN:0002-9106    

DOI:10.1002/aja.1001500309

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

年代:1977

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001500301

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

年代:1977

数据来源: WILEY