摘要:

AbstractIn the chicken Merkel corpuscles are located in the dermis and consist of specialized Merkel cells, discoid nerve endings and lamellar cells. Merkel cells contain characteristic membrane‐bound dense‐core granules and bundles of microfilaments. Asymmetric junctions, synapse like, with thickened membranes and clusters of dense‐core vesicles were observed between the Merkel cells and the nerve endings. The nerve ending is derived from myelinated nerves and sometimes contains clusters of clear vesicles. A laminar system formed by lamellar cells of the Schwann cell type encloses the Merkel cells and the nerve endings. So called “transitional” cells, showing some of the morphological features of both keratinocytes and Merkel cells, were observed in the basal layer of the epidermis. One was located partly in the epidermis and partly in the dermis. The structure of Merkel corpuscles is compared with that of Merkel cells in other tetrapods. The developmental significance of “transitional” cells and the origin of Merkel cells

ISSN:0002-9106    

DOI:10.1002/aja.1001510402

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe development of appendicular synovial joints of both legs was studied with histological and histochemical techniques in 43 rat embryos aged 12 to 21 days. From this and previous studies, it appears that joints develop by a sequence of cellular events leading to a full expression of the phenotypic characteristics. The classically described stages: cell condensation, three layered mesenchyme, vascular invasion and joint clefting, were chronologically recorded in all joints. The observations relevant to the intra‐articular structures, such as joint capsule, menisci and ligaments, were also presented. Previously unreported, cellular aspects were described during joint morphogenesis and their biological significance was discussed. Among these cellular aspects, of particular interest are: a. an early wave of cell necrosis occurring immediately after differentiation of the interzone. Disappearance of necrotic cells is thought to prevent chondrification of this tissue by clearing up the cells with chondroblastic potentialities; and b. a morphologically peculiar type of cells that differentiate alongside, and by the time of, clefting and seem to be related to this process. Thus, the joint clefting appears also to result from a cell‐tissue related phenomenon, acting in conjunction with the joint motion, the importance of which has been previously demonstra

ISSN:0002-9106    

DOI:10.1002/aja.1001510403

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

年代:1978

数据来源: WILEY

摘要:

AbstractPrevious studies by Kaissling et al. ('75) showed that superficial and midcortical glomeruli of the Psammomys kidney give rise to short nephrons which do not enter the inner medulla. The thin descending limbs (TDLs) of such short nephrons descend into the inner stripe of the outer medulla only within vascular bundles. The TDLs of long nephrons are excluded from these bundles.Transmission EM was used in the present study to examine the ultrastructure of short TDLs in relation to the arterial and venous vasa recta. In the interbundle region of the uppermost outer medulla, proximal tubules of short nephrons give rise to TDLs classified as havingType II(interbundle type) epithelium.Type IIis simplified toType I(bundle type) epithelium where the short TDL enters the vascular bundle. It persists throughout the vascular bundle and continues briefly into the interbundle region until its transition to the distal tubule.Type Iepithelium is extremely thin and simple. These cells are poorly inter‐digitated and have simple junctional complexes. An intimate association with the venous vasa recta is seen.Comparison of these data with other micropuncture studies shows that the 4‐fold concentration of urea in the distal nephron is probably correlated with the ultrastructural characteristics of short TDLs and their isolation within vascular bundles. This is augmented by the uptake of urinary urea from the pelvic extensions (Kaissling et al., '75).Thus, the loop of Henle of short nephrons must be regarded as an intrinsic part of the complex multiplier system of the Psammomys kid

ISSN:0002-9106    

DOI:10.1002/aja.1001510404

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

年代:1978

数据来源: WILEY

摘要:

AbstractLong nephrons are derived from juxtamedullary glomeruli. In their descent through the outer medulla toward the inner medulla, the thin descending limbs (TDLs) of long loops of Henle are consistently excluded from the vascular bundles and occupy the interbundle region. The outer medullary segment of long TDLs (Type IIepithelium) is elaborately developed with numerous cellular interdigitations. microvilli, and a cytoplasm well equipped with numerous organelles.The inner medullary segment of these long TDLs is characterized by yet another epithelium that is markedly reduced from itsType IIpredecessor and is designated asType IIIepithelium. It is a very low, flattened epithelium with few cytoplasmic details. In a cross section of the inner medullary TDL, theType IIIepithelium appears poorly interdigitated, with only two to four cell processes and their junctional complexes.Shortly before the bend of a long loop of Henle, the epithelium is again altered to one that is well‐interdigitated and better equipped with cytoplasmic organelles (Type IVepithelium). It persists through the actual bend of the loop and throughout the entire thin ascending limb (TAL), until the latter's transition to the distal tubule at the level of the inner/outer medullary border.We conclude that theType IIepithelium of the outer medullary segments of long TDLs in Psammomys is suitably constructed for involvement in energized transport of solutes. The possibility for a similar role in theType IVepithelium of the bends and TALs is not excluded by our data. However, theType IIIepithelium of the inner medullary segments of long TDLs is most suitably constructed for the concentration of its luminal fluids via water extraction. A comparison between these epithelial types and their permeabilities in various species is presente

ISSN:0002-9106    

DOI:10.1002/aja.1001510405

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

年代:1978

数据来源: WILEY

摘要:

AbstractNeonatal mice were treated with a single dose of triamcinolone hexacetonide, a long‐acting synthetic analogue of cortisol, and their mandibular condyles were studied ultrastructurally ten days thereafter. A pronounced decrease in the number and size of matrix granules (proteoglycans) was found in the cartilaginous matrix of triamcinolone‐treated condyles. In contrast, a marked increase concomitant with significant structural changes was noted in collagen fibrils. An obvious enhancement of collagen fibrillogenesis was noticed in the pre‐mineralizing extracellular matrix. Atypical, wider than normal, banded collagen fibrils were found to form dense meshworks which appeared to lack any specific orientation or organization. It is proposed that glucocorticoid hormones, given systemically to neonatal mice, interfere with regulatory mechanisms involved with the biosynthesis of cartilaginous matrical macromolecules, i.e., proteoglycans and collagen and thereby promote certain aging processes within active growth ce

ISSN:0002-9106    

DOI:10.1002/aja.1001510406

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

年代:1978

数据来源: WILEY

摘要:

AbstractNewborn to 9‐week‐old kittens were anesthetized and then sacrificed by inserting a scalpel into the thoracic cavity and severing the descending aorta. The cerebella were removed and processed according to Golgi‐Cox and rapid Golgi modifications. The results indicate that the dendritic processes of the granule cells undergo a marked postnatal maturation even though there is little postmigratory change in the size and shape of the cell body. A clubshaped swelling of the distal portions of the dendrites is observed by the end of the first week; this “claw” becomes multilobated by three weeks and displays elaborate digitiform projections by nine weeks. The sequence of postnatal development in the kitten appears to follow a time course similar to that observed in other species. A possible correlation between the postnatal development of the granule cell and the postnatal development of the spincocerebellar system is

ISSN:0002-9106    

DOI:10.1002/aja.1001510407

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe epidermal cells which migrate over the wound surface of the amputated limb of the adult newt were examined using the scanning electron microscope. Specimens were prepared routinely for scanning electron microscopy or were embedded in Epon 812 for light microscopic observations. A cuff of epidermal cells was seen at the edge of the wound, from which cells appeared to migrate over the wound surface. As early as five hours after transection of the limb, the basal layers of this cuff appeared to send out pseudopodial projections. These seemed to establish a physical contact with a fibrin‐like substratum, which apparently served as a means of support for the migrating cells. Subsequently, the epidermal cells became elongate and had the appearance of streaming toward the center of the wound. Between 10 and 13 hours post‐amputation, the cells in the central region of the stump were rounded up and some possessed microappendages resembling microplicae and microvilli. Throughout the entire period of wound coverage, the cells seemed to maintain contact with the fibrin network, which appeared to be the first structural element of wound architecture. As a result of these observations, the mechanism by which the epidermal cells migrate has been clarif

ISSN:0002-9106    

DOI:10.1002/aja.1001510408

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe topography and organization of cells lining the peritoneal surface of the diaphragm in normal and intraperitoneally injected mice have been studied by transmission and scanning electron microscopy and freeze‐fracture replication techniques. The mesothelial cells of the peritoneal surface of the diaphragm are organized into two discrete populations. A population of cuboidal cells are found in areas over the lymphatic lacuna (roof covering submesothelial lymphatic vessels) while the remaining areas (not covering lymphatic lacunae) of the diaphragm are lined by extremely flattened cells. The apical surfaces of both cuboidal and flattened mesothelial cells are covered with numerous microvilli. The lateral borders of the cuboidal cells are characterized by the presence of numerous filamentous processes which interlace with similar structures from adjacent cells to form intercellular gaps which overlie a thin layer of connective tissue. In addition to the intercellular gaps, special circular pores are found between the margins of several neighboring cells. The observations suggest that these circular pores are formed when cell margins of several lymphatic endothelial cells span the submesothelial connective tissue to form intercellular junctions with cell margins of several neighboring mesothelial cells lining the peritoneal surface of the diaphragm. The intimate intercellular contact between these two different cell types provides an open channel between the peritoneal cavity and the lumen of the diaphragmatic lymphatic vessels (lymphatic lacunae). It is suggested that these circular pores correspond to the “stomata” of von Reckling‐hausen. Intraperitoneally injected colloidal particles (biological carbon) and red blood cells are rapidly removed from the peritoneal cavity via the circular pores (s

ISSN:0002-9106    

DOI:10.1002/aja.1001510409

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

年代:1978

数据来源: WILEY

摘要:

AbstractGlucagon, insulin, somatostatin, and pancreatic polypeptide have been localized in the anolian pancreas using peroxidase‐antiperoxidase immunocytochemistry. The most abundant endocrine cell type contains glucagon. Insulin‐containing cells are the next most numerous. Somatostatin‐immunoreactive cells tend to be localized at the periphery of the islet cords. Pancreatic polypeptide‐containing cells are a minor endocrine component scattered throughout the exocrine pancreas and occasionally within the islet areas. No staining was observed after application of antigastri

ISSN:0002-9106    

DOI:10.1002/aja.1001510410

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe fine structure of the insemination‐induced flight muscle degeneration (histolysis) in the queen fire ant (Solenopsis spp.) has been investigated. Within 2 hours post‐insemination, degenerative changes are detectable in the most peripheral fasciculi of the fibrillar flight muscle. Histolysis proceeds internally with time. Myofibril (sarcomere) dissolution begins with myofilament breakdown and continues until only free Z‐line material remains. The latter subsequently disappears leaving, at the terminal stages, only nuclei, lamellar bodies (myelin figures), and tracheoles as residual myoid elements. Lysosomes and/or phagocytes do not appear to play a primary role in the initiation and continuance of this pr

ISSN:0002-9106    

DOI:10.1002/aja.1001510411

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

年代:1978

数据来源: WILEY