摘要:

AbstractNumerous optic nerve fibers persist for a period of up to 20 months following enucleation in reptiles, although it is unlikely that a significant number of efferent fibers are present. After varying survival periods, almost all nerve fibers display distinct morphological changes probably associated with degeneration, but most features previously associated with early stages of degeneration can be seen in long‐survival material except for the early and rapid loss of all non‐myelinated fibers and a honeycomb tubular degeneration associated with the inner and outer myelin layers. Distinct sequential stages of axon and myelin degeneration could not be ascertained despite the slow rate of degeneration in poikilotherms. The varieties of abnormal axon morphology are documented and considered in terms of current light microscopic staining meth

ISSN:0002-9106    

DOI:10.1002/aja.1001250302

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

年代:1969

数据来源: WILEY

摘要:

AbstractCalvariae of fetal mice were investigated with electron microscopy in order to demonstrate initial stages of immature, membrane bone calcification. As a consequence, nucleation sites for initial calcification of hydroxyapatite crystals in woven bone were found in extrusions from osteoblasts within the osteoid. Growth of the crystals epitaxially from these initial calcification loci into the surrounding collagen was spherulitic, forming discrete spheres referred to as “bone nodules”. These nodules, when coalesced, formed seams of bone. Decalcified, the organic substructure of the bone nodules was revealed. It contained a centrally disposed initial calcification locus, a peripheral zone of decomplexing collagen and an intermediate zone of altered collagen. Fully formed collagen fibrils remained interposed between most of the coalesced nodules. Polysaccharides were localized within the initial calcification locus and in the peripheral zone of the bone nodules where collagen was shown to be decomplex

ISSN:0002-9106    

DOI:10.1002/aja.1001250303

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

年代:1969

数据来源: WILEY

摘要:

AbstractThe distal small intestine of the albino rat has the capacity to absorb protein and particulate matter during the suckling period. Ultrastructural and cytochemical aspects of this absorptive phenomenon were examined in the ileum. Soon after the initial ingestion of milk, a large, yellow, smooth membrane‐limited, protein body appears in the immediate supranuclear region of ileal absorptive cells and, also, many small vacuoles and membrane‐limited droplets arise between this body and the microvilli. Exogenous protein enters an elaborate superficial tubular system and is segregated in membrane‐limited vacuoles and droplets and, then, appears in the supranuclear body. The body and adjacent membrane‐limited droplets are basophilic, periodic acid‐Schiff positive, and rich in hydrolytic enzymes (acid phosphatase, ATPase, thiamine pyrophosphatase, alkaline phosphatase, esterase). The results suggest the presence of a highly developed lysosomal system during the period of protein absorption. Additional cytological features of the absorptive cells are presented.Ileal absorptive cells are normally free of lipid droplets. When emulsified lipid is introduced into the neonatal ileum, it enters into the cytoplasmic smooth membrane system, including the supranuclear body, and later appeas in the lacteals. This suggests both that the uptake of material may be non‐selective and that similar intracellular pathways may be used in transporting protein and lipid through the

ISSN:0002-9106    

DOI:10.1002/aja.1001250304

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

年代:1969

数据来源: WILEY

摘要:

AbstractThe status of the palatal shelves of shelves of human fetuses (before, during and after palatal shelf elevation) was correlated with mouth opening reflexes recorded cinematographically by Doctor Davenport Hooker for many of the same fetuses. Some deductions and conclusions follow.Mouth opening reflexes begin before palatal shelf elevation and are a significant factor in tongue withdrawal from between the vertical shelves through traction resulting from mandibular depression. (2) The upward pull on the palatal shelves created by differences in pressure between the closed nasal area and the oral region when the tongue is withdrawn (epithelial plugs fill external nares completely) is an active force for palatal shelf elevation. (3) Palatal shelf movements are variable in character and closure sometimes results in the shelf borders enfolding each other. (4) On mouth closure, pressure on the shelves by the tongue and the amniotic fluid entering the mouth helps maintain shelf position before fusion. (5) Human palatal shelf elevation without shelf contact in the midline is not necessarily part of normal closure, but, especially if the shelves are far apart, a stage in cleft palate formation. (6) Increased mandibular growth follows rather than precedes tongue withdrawal. Other factors influencing closure are discussed.

ISSN:0002-9106    

DOI:10.1002/aja.1001250305

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

年代:1969

数据来源: WILEY

摘要:

AbstractIn human embryos and fetuses, a small bundle of nerve fibers from the anterior and posterior vagal trunks descends between the layers of the hepatogastric ligament. These fibers pass to the region of the junction of the umbilical vein with the ductus venosus. At this junction, there is a slight thickening of the muscular wall. Nerve fibers pass to this junction and the proximal portion of the umbilical vein.Fibers from the posterior vagal trunk follow the left gastric artery to the celiac plexus. Fibers from this plexus follow the hepatic artery into the lesser omentum and along the portal vein to the liver. Continuing along the left branch of the portal vein, fibers reach the proximal portion of the umbilical vein and its junction with the ductus venosus.Ganglion cells were observed along the course of vagus nerve fibers to the umbilical vein. In embryos these cells were observed on the lower end of the anterior vagal trunk near the attachment of the upper end of the lesser omentum to the lower end of the esophagus. In older fetuses they were found in a small ganglion in the connective tissue surrouding the distal end of the ductus venosus.

ISSN:0002-9106    

DOI:10.1002/aja.1001250306

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

年代:1969

数据来源: WILEY

摘要:

AbstractThe cytological changes accompanying the development of red blood cells of trout were studied. These changes appear to parallel closely those seen in the maturation of red blood cells of mammals. Immature erythrocytes of the trout contain mitochondria, Golgi complex, rough and smooth endoplasmic reticulum, centrioles, bundles of microtubules and numerous ribosomes in their cytoplasm. With progressive differentiation and maturation such cells appear to shrink in size, acquire a biconvex ellipsoid form, lose most of their cytoplasmic organelles and concomitantly increase their hemoglobin content. Mitochondrial degradation begins early in the process of maturation and usually consists of the following sequence of morphological changes within them: the appearance of small dense bodies, degeneration of the cristae and the formation of lamellar bodies. Degenerating mitochondria are often observed bulging from the surface of the cell, suggesting that they are in the process of being extruded from it. However, this observation does not preclude the possibility that mitochondria may also be disposed ofin situthrough the action of lysosomal enzymes. It is suggested that the disappearance of mitochondria and other cytoplasmic organelles contributes to the volumetric shrinkage which accompanies the maturation of trout red blood cells. The existence of an equatorially oriented “marginal band” of microtubules has been confirmed in this material in agreement with studies on other species. A band of microtubules was also observed in trout thrombocytes. It is concluded that the marginal band plays an important role in the maintenance of the flat ellipsoidal shape of these cells as has been suggested by other investigators studying other vertebrate fo

ISSN:0002-9106    

DOI:10.1002/aja.1001250307

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

年代:1969

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001250301

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

年代:1969

数据来源: WILEY