摘要:

AbstractNormal and abnormal development of movement in the rat were studied by investigating the growth and organization of the motor‐sensory cortexcorticospinal tract system (MSC‐CST) and the functional and morphologic effects of ablating the MSC or quadrants of it at different ages. Major growth of the MSC outflow, the CST, in the brain stem and rostral cord occurred in the second and third weeks postnatally, coinciding approximately with the normal mid‐third week transition from infantile to mature locomotion. Ablation of the MSC at birth revealed that while the MSC‐CST was not essential for ordinary locomotion on flat terrain, its presence hastened normal development of this kind of movement, and that it was absolutely essential for locomotion on difficult terrain. The MSC quadrants showed quite different, and in some domains mutually exclusive, CST projection patterns to forebrain, diencephalon, brain stem, and spinal destinations (determined by Fink‐Heimer‐Nauta fiber degeneration studies). Ablation of some quadrants produced distinctive syndromes of disordered movement: the posterolateral quadrant related to active grasping in positioning limbs, while the posteromedial quadrant related to tactile motorsensory positioning of limbs. Thus in addition to the classic somatotopic organization of the MSC, there was another kind of organization into regions concerned with components of integrated movement of a number of parts of the body. Several forms of aberrant circuitry developed after MSC ablations in infants, but their possible roles in functional adaptation remain to be

ISSN:0002-9106    

DOI:10.1002/aja.1001430102

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

年代:1975

数据来源: WILEY

摘要:

AbstractDeveloping lymph nodes from 30 human fetuses with crownrump lengths (CRL) of 38 mm (8.7 wk) to 245 mm (26 wk) were studied by light and electron microscopy. Blood vessels that appear to be postcapillary venules (PCV) are present in nodes of 47 mm CRL and older fetuses. These venules first appear in nodes when the nodal population of lymphocytes is sparse. In these early nodes PCV are distributed randomly and consist of a low endothelium, underlying basal lamina and incomplete pericyte sheath. Early nodal PCV are distinguished from other nodal blood vessels by the presence of lymphocyte diapedesis and several luminal lymphocytes.In the late stages of nodal development PCV are the more common noncapillary blood vessel and appear in the parenchyma near the periphery of the node. Late nodal PCV are generally characterized by a cuboidal endothelium that is rich in Golgi apparatus, lysosomes and Weibel‐Palade bodies. The lumen and wall of late nodal PCV contain lymphocytes.The relationship between the development of the parenchyma of fetal nodes and the appearance and activity of PCV, the passage of lymphocytes through the PCV wall and the fine structure of developing PCV are described. It is suggested that the lymphocytes that first appear in developing nodes, and the majority of the lymphocytes found in late nodes, migrate to the node via the blood vascular system and enter the nodal parenchyma by passing across PCV endotheliu

ISSN:0002-9106    

DOI:10.1002/aja.1001430103

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe pathway of migration of lymphocytes across the walls of the postcapillary venules was studied in lymph nodes of rats. By means of serial sections, it was determined that lymphocytes enter the venule wall through the endothelial cells and not through the intercellular spaces. After the endothelial cell has been penetrated, the lymphocytes enter the intercellular spaces, from where they gain access to the lymphatic parenchyma. It cannot be excluded, however, that in some instances the path of migration of a lymphocyte is entirely through an endothelial cell from lumen to subendothelial space. While perforating an endothelial cell, a migrating lymphocyte may be in simultaneous contact with the vascular lumen, the intercellular space, and the subendothelial tissue.

ISSN:0002-9106    

DOI:10.1002/aja.1001430104

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe nephron of the euryhaline freshwater salmonids is composed of the renal corpuscle and the renal tubules. Throughout much of the renal corpuscle, only the lamina densa separates the fenestrated processes of the endothelial cells from the foot processes of the visceral epithelium. The renal tubule consists of five distinct segments. The neck segment is short and intermittently ciliated; it lacks the mucous cells which appear in the neck segment of some teleosts. The proximal segment bears a dense brush border and is both structurally and functionally divisible into a first and a second segment. The first portion is typified by the presence of short apical tubules, variously sized apical vacuoles, and numerous lysosomes. The second proximal segment is distinguished by the abundance and distribution of mitochondria throughout the cytoplasm. Infoldings of the basilar plasmalemma are especially prominent in this region. A ciliated intermediate segment intervenes briefly between the proximal and distal portions of the tubule. The distal segment consists of cuboidal cells which bear scattered, short microvilli, small vesicles and multivesicular bodies.Renal tissue from several species of trout was examined in order to establish the basis for a common pattern of histological and ultrastructural characteristics within the familySalmonidae. In all species examined, renal structure was very similar and could readily be compared with that previously described in other freshwater and marine species.

ISSN:0002-9106    

DOI:10.1002/aja.1001430105

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

年代:1975

数据来源: WILEY

摘要:

AbstractUteri taken from 25 bitches at various times during the early stages of pregnancy were studied cytologically to determine how the implantation chamber developed and how fetal‐maternal relations were established. On day 13 after the end of estrus, knobs of trophoblastic syncytium formed and became wedged between cells of the uterine luminal epithelium. The syncytium quickly spread along the uterine lumen and into the mouths of the glands, dislodging and surrounding maternal cells. As invasion continued trophoblastic villi, consisting of cores of cytotrophoblast covered by a continuous layer of syncytium, penetrated deeper into the endometrium. The syncytium spread to surround maternal vessels and decidual cells. By day 26 the trophoblast had extended down to the large lacunae. Here syncytial trophoblast covering tips of the villi degenerated, leaving cytotrophoblast exposed to the necrotic zone. These cells possessed characteristics of absorbing cells. Hematomas were formed by focal necrosis of fetal and endometrial tissue at the poles of the implantation sites. Large pools of extravasated blood accumulated and red blood cells were phagocytized by surrounding trophoblastic cells.Therefore, the endotheliochorial relationship in the canine placenta appeared to be established by syncytial trophoblast invading a cellular endometrium. In the necrotic zone and hematomas, cellular trophoblast may have lost its syncytial covering, but elsewhere maternal vessels and decidual cells in the placenta were in direct contact only with syncytial trophoblas

ISSN:0002-9106    

DOI:10.1002/aja.1001430106

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

年代:1975

数据来源: WILEY

摘要:

AbstractEndothelial and connective tissue cells of the choroid plexus have been studied by the freeze‐etching technique. The endothelial cells of pre‐ and postcapillary segments are coupled by a complex junctional system consisting of a combination of tight and gap junctions. Connective tissue cells revealed the same intercellular contacts. Furthermore two different types of gap junctions occurring in membranes of the connective tissue cells are descri

ISSN:0002-9106    

DOI:10.1002/aja.1001430107

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

年代:1975

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001430101

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

年代:1975

数据来源: WILEY