摘要:

AbstractIt has recently been discovered that the stratum corneum and superficial living epidermis of mammalian skin are organized into neat vertical columns of interdigitating cells. The mechanism for this organization has not yet been determined. This study shows that the stacked organization is not unique to the epidermis but also occurs in cork cambium and the pith of woody plant stems. The structural and spatial organization of the stacked cells in these tissues were compared and found to approximate closely the shape of Kelvin's minimum‐surface polygon, the tetrakaidecahedron. Paper models of flattened tetrakaidecahedra were constructed and found to stack in columns of interdigitating units which are consistent with all of the structural details seen in stacked cells observed under the light and the scanning electron microscopes. Indeed, only polygons of this type are capable of aggregating without interstices in the manner of the stacked cells. A study of stacked arrays of these models has revealed a mechanism by which the epidermis might become organized in columns of stacked and interdigitating cells. The proposed mechanism assumes that cells within an array seek the smallest possible surface‐to‐volume ratio and, under appropriate conditions, form stacked tetrakaideca

ISSN:0002-9106    

DOI:10.1002/aja.1001450102

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe microvascular anatomy of the human epididymal duct system from rete testis to vas deferens was studied using microangiography and histology. Various segments of the duct system show significant differences in the density and arrangement of the small blood vessels. The rete testis is poorly vascularized while the first lobulated segment of the epididymis, which is formed by the efferent ducts is provided with a dense subepithelial capillary bed. The more distal segments of the epididymis have less dense capillarization surrounding the epididymal duct. In the vas deferens the blood vessels form a double capillary network. The outer capillary network surrounds the smooth muscle layers and the inner is located immediately beneath the duct epithelium. The organization of blood capillaries in the human epididymis and the differences seen in different portions of the excurrent duct system follow basically the general pattern seen in some experimental animals.

ISSN:0002-9106    

DOI:10.1002/aja.1001450103

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe structure of the placental labyrinth, interlobular or “coarse” syncytium, visceral (splanchnopleuric) yolk sac, giant cells and subplacenta of the chinchilla was studied with the electron microscope. The fine structure of the interhemal membrane of the placental labyrinth was found to be hemomonochorial, consisting of a single layer of syncytial trophoblast. In this respect, the placental labyrinth was similar to that of another caviomorph rodent, the guinea pig. The labyrinthine trophoblast had pinocytotic vesicles as well as larger vacuoles and multivesicular bodies. The interlobular syncytium contained granular endoplasmic reticulum, and in one case from early in gestation there were intracisternal granules in the ER. The visceral endodermal cells of the inverted yolk sac placenta had a well‐developed system of apical vesicles and tubules as well as larger cytoplasmic vacuoles. Their appearance was similar to that of endodermal cells found in other rodents which are known to absorb proteins and other substances from the uterine lumen. Towards term the giant cells were often vacuolated and contained large deposits of glycogen as well as lipid droplets. The syncytial trophoblast of the subplacenta contained numerous moderately electron‐dense granules which may be secretory in function; cytotrophoblastic cells lacked these granules. The subplacental syncytium often surrounded spaces or lacunae which contained an electron‐dense granular

ISSN:0002-9106    

DOI:10.1002/aja.1001450104

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

年代:1976

数据来源: WILEY

摘要:

AbstractAn ultrastructural and cytochemical study of normal human mammary epithelial cells cultured from post‐weaning breast fluids is described. Cells were examined at the time of plating and at intervals up to 28 days in culture. Three different stages in the morphological differentiation of these cells in vitro were observed: (1) the first stage was the formation of a monolayer of single cells, which occurred between days 1 and 10 in culture. The cells in this stage were not interconnected by junctional complexes and lacked Mg++‐ dependent ATPase activity in the plasma membranes, but did contain a large quantity of lipid and exhibited some secretory characteristics. (2) The second stage, occurring at 10 to 16 days in culture, was characterized by the formation of junctional complexes, the appearance of Mg++‐dependent ATPase in the plasma membrane and a decrease in the number of dense bodies with peroxidase activity. (3) The third stage, occurring at 16 to 28 days in culture, was characterized by the formation of stratified layers of epithelial cells, which were inter‐connected by a large number of desmosomes with numerous pleomorphic microfilaments. The Mg++‐dependent ATPase activity in the plasma membrane was retained and the dense bodies with peroxidase activity were rarely observed at this stage. During the last seven days in culture, secondary lysosomes, autophagosomes and residual bodies were prominent in the cells of the stratified layer. After 28 days in culture, the cells began to round up and slough off the cult

ISSN:0002-9106    

DOI:10.1002/aja.1001450105

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

年代:1976

数据来源: WILEY

摘要:

AbstractDegeneration and early regeneration of olfactory epithelium from two strains of mice was studied at the light and electron microscopic levels from 12 hours to 3 days following nasal irrigation with 1% aqueous solution of zinc sulfate (ZnSO4) (a compound known to selectively damage olfactory epithelium). Distinct patterns of degeneration and stages of regeneration were evident following treatment. During the first 24 hours after treatment three progressive manifestations of the degenerative process were seen: (1) a relatively mild condition which was characterized by surface irregularities produced by cell protrusions, highly vacuolated cytoplasm, presence of large lysosome‐like bodies and prominent intercellular spaces, (2) a more severe condition in which large areas of the epithelium were detached from the basement membrane and cellular debris was present in the nasal chamber, and (3) a condition of total or near‐total denudation of the epithelium of olfactory mucosa. The basal lamina was continuous and intact in most regions and the integrity of the subjacent connective tissue was mostly well‐preserved. Nerve bundles of the fila olfactoria were noted in varying degrees of degeneration during the course of the experiment. The most advanced neural degeneration was seen 24 to 72 hours after treatment. Onset of regeneration was suggested by the appearance of a simple squamous layer of cells above the basement membrane 48 to 72 hours after treatment. In addition to the simple epithelium a stratified epithelium consisting of two to four cell layers was also observed at this time. Glandular cells, containing secretory granules identical to those in Bowman's glandular cells, were noted in an apparent process of migration from the lamina propria into the stratified epithelial layer. The last mentioned observation supports the proposition that new supportive epithelial cells originate from cells of Bowman's

ISSN:0002-9106    

DOI:10.1002/aja.1001450106

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

年代:1976

数据来源: WILEY

摘要:

AbstractRabbit spleens have been examined after perfusion fixation with and without prior washing with various fluids. The platelets were stored in the splenic sinuses and in the cord spaces as single platelets, or in loosley packed aggregates which appeared to be anchored to the endothelium by one or a few platelets. After washing prior to fixation most of the platelets disaggregated and regained their normal shape. Some platelets adhered to morphologically normal endothelium even after prolonged perfusion. Occasionally, platelets were observed inside splenic endothelial cells. Others were closely associated with macrophages, many of which also contained engulfed platelets.There was no morphological evidence of a particular platelet population being retained in the spleen after washing.In the sinuses special granule‐rich cytoplasmic structures were observed. They were interposed between ordinary endothelial cells and contained a large number of small lysosome‐like granules. Nuclei were never observed in these structures, probably because they consisted of pseudopod‐like protrusions. Their origin and function are discussed. They may represent actively phagocytizing ele

ISSN:0002-9106    

DOI:10.1002/aja.1001450107

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

年代:1976

数据来源: WILEY

摘要:

AbstractCycling rats were hysterectomized and/or unilaterally ovariectomized (ULO) on day 2 (metestrus). Collateral blood supply to the remaining ovary via the uterine artery was left intact or disrupted. Animals were killed in metestrus after one complete estrous cycle. Control rats were also killed at this time.Counts of tubal ova revealed that intact rats ovulated an average of 4.4 ± 0.4 eggs per ovary (N = 8). Following ULO, rats (N = 8) ovulated 9.6 ± 0.2 eggs. Ligation of the uterine artery decreased the number of eggs ovulated in ULO rats (N = 8) to 5.4 ± 1.1. Hysterectomized rats (N = 8) ovulated 4.8 ± 0.5 eggs per ovary. If the blood supply was disrupted, a reduction to 2.7 ± 0.2 eggs per ovary occurred (N = 8). Hysterectomized and ULO rats (N = 8) ovulated 10.3 ± 0.4 eggs from the remaining ovary but only 5.0 ± 1.0 eggs if the collateral blood supply of the uterine artery was not intact (N = 10).The results demonstrate that disruption of the vascular channels during the surgical procedures of hysterectomy and/or ULO results in a reduction of the expected ovulation

ISSN:0002-9106    

DOI:10.1002/aja.1001450108

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

年代:1976

数据来源: WILEY

摘要:

AbstractIn the monkey lung (Macacus nemestrina) canalization ofallbronchopulmonary segments begins simultaneously at the peripheral future‐alveolar‐duct portions of each segment and then continues progressively centralwards. Its simultaneous appearance in all segments of ahumanlung of the 17th postovulatory week (19th postmenstrual week) has now been confirmed (cf. Boyden, '74). The mode of canalization, as seen under the light microscope, is here demonstra

ISSN:0002-9106    

DOI:10.1002/aja.1001450109

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

年代:1976

数据来源: WILEY

摘要:

AbstractSynapses were counted in electron micrographs of the middle third of the molecular layer of the dentate gyrus of Fischer 344 rats, 3 months and 25 months of age. A 27% decrease in the number of synapses was found in senescent animals compared with young adults. This loss of synapses could not be correlated with changes in synaptic size, tissue volume or number of postsynaptic granule cells.

ISSN:0002-9106    

DOI:10.1002/aja.1001450110

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

年代:1976

数据来源: WILEY

摘要:

AbstractThe effects of pressure on the luminal surface of the rabbit aorta were investigated using the scanning electron microscope. The method followed was perfusion under hydrostatic pressure of a section of thoracic aorta, in vitro. The characteristic ridged pattern seen in sections fixed at zero hydrostatic pressure was to a large extent eliminated when fixation occurred at pressures equivalent to those experienced by the aorta at systole or diastole. This study suggests that the spiral ridged pattern is dependent upon the fixation pressure and may not be present in a normally functioning artery. Any attempts to characterize or interpret the appearance of the luminal arterial wall must take into account the effects of pressure.

ISSN:0002-9106    

DOI:10.1002/aja.1001450111

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

年代:1976

数据来源: WILEY