摘要:

AbstractThe distribution of calcium was determined in the vas deferens of the guinea pig using45Ca electron microscopic autoradiography of rapidly frozen, freeze‐dried, and embedded tissue. A selective accumulation of calcium at the plasma membrane and SR was observed in vas deferens that had been incubated in45Ca for 65–85 min prior to rapid freezing. Rinsing the tissue in nonradioactive calcium for 6 min prior to rapid freezing significantly altered the distribution of calcium among the plasma membrane, mitochondria, and cytoplasmic matrix. The influence of species on the observed distribution of calcium was also examined. The distribution of calcium in the guinea pig was deferens was not significantly different from that in the rabbit vas deferens when the tissues were prepared under identical conditi

ISSN:0003-276X    

DOI:10.1002/ar.1092170402

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

年代:1987

数据来源: WILEY

摘要:

AbstractArchitectural arrangement, ultrastructure, and selected histochemical properties of the newt (Notophthalmus viridescens) liver were examined. Although hematopoietic tissue (1–4 cells thick) invested the liver, direct vascular communication between this tissue and hepatic parenchyma was not observed. The liver was intensely positive when stained with Oil‐red‐O and periodic acid‐Schiff reagent and connective tissue was limited to large vascular channels and the capsule. A distinctive polarity was observed in the hepatic vascular system when lobes were viewed in cross section. Dorsally, portal venules accompanied arterioles and branches of the biliary system, while tributaries of hepatic veins were observed ventrally. Following perfusion fixation, hepatocytes appeared as sheets of cells 1–5 cells thick; however, lobules as defined in adult mammalian liver were absent. Hepatocytes contained abundant smooth endoplasmic reticulum, mitochondria, electron‐dense lysosomes, patches of granular endoplasmic reticulum, and lipid droplets. Continuous endothelial cells lined sinusoids and exhibited fenestrae organized into structures similar to sieve plates observed in mammalian liver. Variable numbers of melanin‐containing macrophages and subendothelial macrophages were observed; however, Kupffer cells and lipid containing perisinusoidal fat‐storing cells were not seen. Patterns of reaction product for glucose‐6‐phosphatase (G‐6‐Pase), glucose‐6‐phosphate dehydrogenase (G‐6‐PDH), and succinic dehydrogenase (SDH) were localized in the newt liver. All enzymes exhibited a uniform distribution pattern; however, small punctate regions of intensely positive G‐6‐PDH cells were noted within hepatic parenchyma. Cells comprising the hematopoietic tissue were intensely positive for G‐

ISSN:0003-276X    

DOI:10.1002/ar.1092170403

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

年代:1987

数据来源: WILEY

摘要:

AbstractIn the remodeling interdental septum of the mouse, four types of Sharpey's fibers were observed. Classification of these fiber types was based on characteristics of their termination within the septum in relation to the resorption‐related reversal line separating old and new bone. “Severed fibers” were located only within old bone and terminated at the reversal line. “Arborized fibers” were located only within new bone and terminated therein. “Adhesive fibers” were located within new bone and terminated within a heavy band of granular material at the reversal line. “Continuous fibers” had components within old and new bone. These components were connected across the reversal line by nonstriated fibrils. Adhesive fibers were the least numerous type; severed and arborized fibers were observed at nearly equal frequency. Continuous fibers were the most numerous type, their numbers being significantly greater than any of the other types (P<.001). Mean numbers of continuous fibers were greater than the mean total of the three other fiber types (P<.001). Mean numbers of severed, adhesive, and arborized fibers were not statistically different. The study suggested that continuous fibers could be transalveolar—that is, ones which pass through the septum without interruption joining fibers of the adjacent periodontal ligament. Maintenance of their spatial continuity appeared to require a connecting protein to orient new unit collagen fibrils to old ones in areas of reversal. Thus, transalveolar fiber bundles could be characterized as being composed of old and new segments joined by a connecting protein. As their unit collagen fibrils did not cross resorption‐related reversal lines these fibers were spatially continuous but tem

ISSN:0003-276X    

DOI:10.1002/ar.1092170404

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe purpose of this work was to study the human fetal esophagus maintained in organ culture. Esophageal explants from 8 fetuses aged from 12 to 16 weeks of gestation were cultured up to 21 days at 37°C in Leibovitz L‐15 serum‐free medium. Between 12 and 16 weeks of gestation, the esophagus has a stratified columnar ciliated epithelium, and glycogen aggregates are present in all cell layers. This morphology remains the same up to 5 days in culture. After 7 to 9 days, a vacuolization in the upper half layer occurs, leading to a lifting off of the ciliated layer and a flattening of the subjacent cells. After 15 days of culture, the esophageal epithelium is stratified squamous and the cells are exfoliated at the surface of the explants. Glycogen aggregates are still present in all layers. Islets of ciliated cells resting on the basal cell layers develop within the squamous epithelium. With the extension of the culture period up to 21 days, the general morphology of the epithelium does not change. The ultrastructural features of the newly formed squamous epithelium, with its basal lamina, are similar to that reported for human adult esophageal epithelium. During the course of the culture, the DNA synthesis continues as determined by autoradiography. It is concluded that it is possible to maintain viable human fetal esophagus in organ culture and that an accelerated maturation takes place leading to the formation of the adult esophageal epithe

ISSN:0003-276X    

DOI:10.1002/ar.1092170405

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

年代:1987

数据来源: WILEY

摘要:

AbstractEndothelial plasmalemmal vesicles were examined in serial sections and in deep‐etch replicas of rapid‐frozen rat muscle capillary endothelium. Numerous fused vesicles were observed in both preparations. The morphology of the vesicles in rapid‐frozen capillaries differed from that in the chemically fixed ones; rapid‐frozen vesicles were spherical rather than ovoid, and the necks of caveolae and the connecting portion of fused vesicles were wider than those of chemically fixed ones. In the serial sections, true free vesicles were rarely identified (1.6%). In the deep‐etch replicas, some of the cytoplasmic surface of vesicles had a mulberrylike appearance and intracytoplasmic fine fibrils appeared to connect the vesicles either to other vesicles or to the plasmalemma proper. Two transendothelial channels were found among 250 capillary profiles. Almost all endothelial “vesicles” proved to be invaginations of the surface membrane, and chemical fixatives did not seem to induce any substantial membrane fusion. These observations suggest that transendothelial transport of large macromolecules across continuous capillary endothelium is carried out mainly by diffusion through transendothe

ISSN:0003-276X    

DOI:10.1002/ar.1092170406

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

年代:1987

数据来源: WILEY

摘要:

AbstractIn rat embryos, acetylcholinesterase (AChE, EC 3.1.1.7) activity is present in a continuous sleeve of mycocytes that extends from the myocardium that is adjacent to the atrioventricular endocardial cushions via the ventricular trabeculae to the outflow tract. No activity is found in the atrial roof, in the ventricular walls and in the interventricular septum except for its subendocardial surface. AChE‐positive cells are first identified in 11‐day rat embryos, while the prototypical distribution is best demonstrable in 13‐day embryos. Part of the AChE‐positive cell system is identifiable as a precursor of the adult conduction system by topographical criteria in 16‐day fetuses and by morphological criteria in 20‐day fetuses. At birth (2 days later), AChE activity has disappeared from the cardiac myocytes except for a ring of tissue at the atrial side of the atrioventricular junction. These findings suggest that the embryonic heart can be divided into an upstream mycardium that has no AChE activity and a downstream myocardium that is characterized by the presence of AChE. Furthermore they suggest that an acetylcholine‐dependent mechanism may be responsible for the retardation of the depolarization wave in the downstream parts of the heart. Finally they show that the adult conduction system is formed by a transdifferentiation of part of a far more extensive embryonic pre

ISSN:0003-276X    

DOI:10.1002/ar.1092170407

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe anterior pituitary glands of 31‐day‐old male rats were autotransplanted under renal capsule. At the 3rd and 5th day after transplantation, the autografts were observed by electron microscopy and by immunohistochemistry using antiserum against S‐100 protein, which serves as marker of folliculo‐stellate (FS) cells.On the 3rd day, a large part of the graft was replaced with loose connective tissue in which the FS cells were remarkable in number. The FS cells encircled a small number of granular cells and formed cyst‐ or ductule‐like structures with neighboring FS cells. Together, FS cells and the encircled granular cells formed a basement membrane surrounding the entire ductule. Throughout the regenerating gland, many such ductules were found. On the 5th day, both granular cells and FS cells increased in number.The above observations suggest that FS cells may play an important role in the restoration of degenerated pituitary glandular tissues during the early stage of the tran

ISSN:0003-276X    

DOI:10.1002/ar.1092170408

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe early embryonic heart is composed of two cylindrical epithelial layers, an inner endothelium and an outer myocardium. The cardiac jelly (CJ), an acellular accumulation of extracellular matrix (ECM), fills the space between the two epithelia. During development of the heart, a portion of the endothelial cells of the atrioventricular (AV) region differentiate into mesenchyme cells in a temporally and spacially specific manner. Although contiguous with those in the AV region, endothelial cells lining the ventricle never form mesenchyme in situ. At present, the mechanisms controlling the biphasic differentiation of the endothelium and the subsequent migration of cardiac mesenchymal cells are poorly understood.Although the CJ lies between two epithelial and is spatially equivalent to a basement membrane (BM), it has not traditionally been considered to be organized into a BM‐like structure. The potential significance of this observation to developmental biology lies in the possibility that BM or their individual componetns (i.e.), fibronectin (FN), laminin (LM), type IV collagen, and heparin sulfate proteoglycan (HSPG) may function as the regulatory site of epithelial differentiation and morphogenesis.A cryofixation technique was developed in order to determine the in situ immunohistochemical distribution of the BM components in the CJ. Results indicated that the CJ exists as the fusion between a larger myocardially derived BM having a lamina densa and an extended reticular lamina and an attenuated, endothelial‐associated BM composed only of a lamina densa. Except for FN, the individual BM components were not all present during early stages, but instead appeared in a sequential manner, suggesting that all components of an adult‐type BM are not required to initiate the assembly of a structural and functional BM during development. In the AV canal and outflow tract (OT), FN appeared as a progressively expanding gradient of material with the greates density nearer the myoca

ISSN:0003-276X    

DOI:10.1002/ar.1092170409

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe morphology of the parotid gland in adult mice is mouse strain‐specific. C57BL/6 and C3H/He strains of mouse are representatives of two types of the morphology identified previously. The postnatal development of such morphologic differences was investigated by sialography of excised glands of these strains of mouse. It was observed that the mouse strain‐dependent morphological characteristics were already present at birth, except for the branching pattern of the peripheral duct system, which became differentiated at 3 weeks of age. These results indicate that the C3H/He mouse‐specific branching pattern of the peripheral ducts reflects the profile of matured secretory units and ducts, and that the C57BL/6 mouse‐specific pattern resembles that of an immature C3H/H

ISSN:0003-276X    

DOI:10.1002/ar.1092170410

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

年代:1987

数据来源: WILEY

摘要:

AbstractIn an attempt to clarify the relationship between the presence of retinal cell death and the invagination of the optic vesicle, we have tested the occurrence and cytological characteristics of the retinal necrotic areas in the embryonic chicken after the administration in ovo of papaverine. Papaverine, a Ca2+antagonist, was found to prevent the invagination of the optic vesicle. All embryonic retinae presented two distinct necrotic areas. However, these areas of cell death appeared abnormally located in the experimental, uninvaginated retina. One area was located at the transition between the retinal disc and the ventral wall of the optic vesicle; a second area was located in the dorsal wall of the optic vesicle, close to the optic stalk. We suggest that these necrotic areas represent the normal necrotic areas, should the invagination of the retinal disc have taken place. Retinal cell death appears to beprogrammed; it occurs whether the retinal disc invaginates or not. Cell death appears, in this experimental model, as a natural marker giving evidence that the embryonic retinal cells move from the optic stalk into the invagination retinal disc during normal eye cup formation.In addition to the uninvaginated optic vesicle the lens placode failed to invaginate in 45% of the cases, forming a lens vesicle in 55% of the remaining cases. This suggests that the two processes of invaginate in 45% of the cases, forming a lens vesicle in 55% of the remaining cases. This suggests that the two processes of invagination are governed by a different set of factors.

ISSN:0003-276X    

DOI:10.1002/ar.1092170411

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

年代:1987

数据来源: WILEY