摘要:

AbstractThe morphogenesis of the outer human retina from 6.5 to 18 weeks of gestational age (16–156 mm) was studied by light and electron microscopy. During this period the retinal pigment epithelium changes from a pseudostratified columnar epithelium, with mitoses at its inner edge, to a single layer of cuboidal cells. Initially, mature pigment granules, premelanosomes, polysomes, rough endoplasmic reticulum and a Golgi complex occupy the epithelial cytoplasm. Lateral epithelial surfaces show infoldings and neighboring epithelial cells are bound at their inner borders by a junctional complex consisting of a zonula occludens and zonula adherens. Later, pigment epithelial development is marked by an increase in cytoplasmic organelle content and the appearance of slender processes at the inner epithelial border. Initially, the outer neural retina is formed by a uniform population of elongated cells containing oval nuclei with multiple nucleoli and, in the cytoplasm, mitochondria, polysomes and the Golgi complex. Cell division is common in the proliferative layer at the outer edge of the posterior neural retina until 120 mm crown‐rump length, and cell membrane junctions between outer neuroblasts remain intact during mitosis. Cilia project outwards from outer neuroblasts and invaginate the immediately adjacent pigment epithelium. At 120 mm crown‐rump length, differentiating rods, cones and Müller cell processes are distinguishable and developing ribbon synapses and surface contacts are present at the base of the cone prior to outer segment for

ISSN:0002-9106    

DOI:10.1002/aja.1001370402

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe purpose of this study was to experimentally and critically examine the possibility of vascular routes from the pineal gland to the brain in the laboratory rat. Vascular perfusions in the pineal region with India ink in heparinized saline were performed on animals of diverse ages (1 month to 2 years) during the early and middle parts of the daily period of light and immediately post‐mortem. Cleared specimens were studied both before and after serial sectioning for light microscopy. Pineal microvasculature was relatively resistant to retrograde perfusion from the adjacent venous sinuses. But the choroid plexus of the suprapineal recess commonly contained perfusate from these sinuses and the pineal gland.The results define the anatomical limits of possible pineal to brain blood flow, but do not of course provide any direct evidence that such flow exists in vivo. Nevertheless, the results from the perfusions lead to the conclusion thatifa direct and non‐systemic vascular path carries pineal hormone to brain, the path consists of the vena cerebri magna and the choroid plexus of the suprapineal recess. This concept assumes reversibility of direction of blood flow in these vessels, an observed physiological property of at least some intracranial veins in other spec

ISSN:0002-9106    

DOI:10.1002/aja.1001370403

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

年代:1973

数据来源: WILEY

摘要:

AbstractA systematic investigation of the effects of proteolytic enzymes, chelators and detergents on desmosomes originating in a variety of tissues was undertaken. Although junctions from different tissues are morphologically similar, we found great differences in their sensitivity to various reagents, indicating dissimilarities in biochemical composition.In general, desmosomes from stratified squamous and glandular epithelia were insensitive to ethylenediaminetetraacetic acid (EDTA), but readily dissociable with trypsin. Enzymatic digestion caused disruption of material within the junctional extracellular space, and dislocation of paired desmosomal plaques. In contrast, the extracellular components of desmosomes from simple columnar epithelia were usually EDTA‐sensitive but trypsin‐resistant. There were, however, exceptions to the general pattern. Desmosomes from rat pancreas were affected only by the detergent sodium desoxycholate (DOC). DOC also solubilized the intermediate dense line of desmosomes from the frog skin.We have divided desmosomes into two broad categories based upon the differential effects of these reagents. One group, sensitive to trypsin or DOC, may be functionally “stable” in maintaining cell‐to‐cell associations for long periods. Such junctions occur in stratified squamous and many glandular epithelia. Another group of desmosomes, affected by chelating agents, may be physiologically “labile” or plastic. These junctions, occurring in simple columnar epithelia such as the gut, may respond to physiological stimuli by opening or closing, thus allowing intercellular migration of cells and substances passing through the e

ISSN:0002-9106    

DOI:10.1002/aja.1001370404

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

年代:1973

数据来源: WILEY

摘要:

AbstractA study of the progestational evolution of the endometrium of the rabbit in pseudopregnancy suggests a division into the following phases: (1) priming phase (0–24 hours), in which no significant changes were observed except for leucocytic invasion of the epithelium, (2) proliferative phase (1–4 days), in which mitosis is active and the epithelium becomes pseudostratified and the glands proliferate, (3) phase of epithelial relayering and folding (4–6 days), in which the epithelium is single‐layered and there is evidence of secretory activity, (4) phase of cell fusion (6–8 days), in which the columnar cells fuse into multinucleated masses, and (5) maximally progestational phase (8–13 days), in which almost all the epithelial cells are multinucleated except for occasional ciliated cells, and, in some animals with evidence of the effects of high systemic levels of estrogen, extensive ciliation, especially antimesometrially. A final phase (6), not studied in detail, is a declining phase marked by degeneration and sloughing of the multinucleated epithelium and replacement with predominantly ciliated cells. Reconstruction of the minor mucosal folds, as distinct from the six or so major folds present in the non‐pregnant animal, shows that these are true elevations of the mucosa above the level of the mouths of the glands. The current concept of progestational changes in the endometrium of the rabbit as predominantly due to glandular proliferation is incorrect; this has important implications for analysis of the implant

ISSN:0002-9106    

DOI:10.1002/aja.1001370405

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

年代:1973

数据来源: WILEY

摘要:

AbstractThe effects of 6‐hydroxydopamine, an analog of dopamine which produces degeneration of peripheral adrenergic nerve terminals in adult animals, on adrenergic neurons in the sympathetic ganglia of newborn rabbits were studied with the electron microscope. Animals were treated with a 50 mg/kg dose of 6‐hydroxydopamine within six hours after birth and subsequently given daily doses until seven injections had been administered. The results of this study indicate that the adrenergic neurons underwent a “reaction” to 6‐hydroxydopamine which was first manifested by an increase in filaments and smooth membranous structures in the cell bodies. In the axons of these neurons a similar increase in filaments and membranous elements, as well as accumulations of dark‐core vesicles and mitchondria, were evident. Microtubules, although plentiful in normal cells and axons, were not conspicuous in these cells and axons. This initial reaction was later followed by degeneration of the cell bodies and axons and their eventual disappearance, leading to a reduction in cell population and size of the ganglia. It is suggested that the initial effect of 6‐hydroxydopamine on adrenergic neurons (in newborn animals) may be an interference with their axoplasmic transport mechanism which leads to cell degeneration and death. This study also has shown that some of the small “granule‐containing” cells in sympathetic ganglia may be sensitive to 6‐hydroxydopamine, at least in newborn rabbits, as is indicated

ISSN:0002-9106    

DOI:10.1002/aja.1001370406

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

年代:1973

数据来源: WILEY

摘要:

AbstractCycloheximide is a known inhibitor of cytoribosomal translation. Previously published results indicated that embryos cultured in cyclo‐heximide developed only to the midblastula stage. The current study involved injecting one μg of cycloheximide into each developing embryo of Rana pipiens. The three stages selected for the injection were the two‐cell, late four‐cell, and morula. The embryos stopped developing at the four‐cell, sixteen‐cell and midblastula stages, respectively. Control embryos injected at the same stages with Holtfreter's solution developed normally. The results would indicate that de novo protein synthesis is necessary, not just at the midblastula stage, but throughout the entire cleavage period. The results are discussed in light of previous inve

ISSN:0002-9106    

DOI:10.1002/aja.1001370407

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

年代:1973

数据来源: WILEY

摘要:

AbstractExtensive absorption of ferritin was demonstrated in the proximal and distal ileum of 8–12 day‐old rats. In some regions, ferritin droplets were distributed in the basal cytoplasm of the columnar epithelium and in the lamina propria one hour after feeding. Subsequently, iron‐positive material was localized adjacent to vessels of the lamina propria and in macrophages. Absorption of lesser quantities was demonstrated in the duo

ISSN:0002-9106    

DOI:10.1002/aja.1001370408

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

年代:1973

数据来源: WILEY

摘要:

AbstractDuring development of the secondary palate, mouth‐opening reflexes and swallowing movements have been observed previously. They have been assumed to be necessary in order to allow the descent of the tongue, thus enabling movement of the palatine shelves from a vertical position lateral to the tongue, to a horizontal position superior to the tongue. Interpretation of fixed, paraffin‐embedded sections, showing large spaces in the oral cavity, has added to the concept that the tongue descends into a space.Hexane‐quenched, cryostat‐cut, frozen sections of fetal mice heads show that no oral space exists at any time during elevation of the palatine shelves. Interpretation of static micrographs indicates that prior to shelf elevation the tongue is in contact with the nasal septum above and the vertical palatine shelves laterally. When the shelves elevate they seem to “flow” dorsally and interpose themselves between the tongue inferiorly and the nasal septum

ISSN:0002-9106    

DOI:10.1002/aja.1001370409

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

年代:1973

数据来源: WILEY

摘要:

AbstractYoung dogs were perfused with buffered aldehydes at fluid pressures approaching normal physiological values. Surface tissue from the temporal horns of the lateral ventricles were prepared for scanning electron microscopy, using postosmication, critical point drying and gold‐palladium coating.The ependymal surfaces are mostly ciliated but nonciliated areas occur along the medial walls. The latter areas are characterized by depressions, pores, fenestrations and a unique population of supraependymal cells. These polymorphic cells probably represent both conductive (neuronal) and supportive (neuroglial) elements. Adjacent to cilia‐free areas, transitional zones are observed. Here, a net‐like surface pattern consisting of smooth hexagonal cells is outlined by microvilli of varying lengths and isolated tufts of cilia are pr

ISSN:0002-9106    

DOI:10.1002/aja.1001370410

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

年代:1973

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001370401

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

年代:1973

数据来源: WILEY