摘要:

AbstractThe plasmalemmal relationship between metastases‐forming leukemia cells and myeloid sinus endothelium during the transmural passage of the leukemia cells has been studied in rat bone marrow. After the myeloid vascular system was freed from normal circulating blood cells, the bone marrow was perfused with a suspension of leukemia cells derived from an ascites tumor. The bone marrow was then fixed by perfusion with double aldehyde with and without the addition of tannic acid.Leukemia cells were seen adhering to the adluminal aspect of the sinus endothelium and in all stages of endothelial penetration. The penetration of the sinus wall was independent of endothelial junctions; i.e., the transmural passage into the myeloid parenchyma was transcellular. At these sites, there were restricted areas of close plasmalemmal appositions of the two cell types where the intraplasmalemmal space was reduced to 2.3 nm. This space was interrupted by electron densities of 5 nm diameter and spaced 9 nm center to center. These close plasmalemmal appositions extended over distances ranging from 150 nm to 200 nm. It is suggested on the basis of the structural similarity that these heptalaminar complexes of close plasmalemmal apposition represent the structural equivalent of gap junctions and may be sites of intercellular communication requisite for transmural passage.When tannic acid was added to the fixative, there were extended areas of apparent fusion of the plasmalemmas of the two cell types, at the sites both of adhesion and of endothelial penetration. This fusion was limited to the outer leaflets of the two plasmalemmas, resulting in a single pentalaminar complex. These pentalaminar complexes extended over decidedly longer distances than the presumed gap junctions seen in the non‐tannic‐acid‐fixed material. The tannic acid material did not show the heptalaminar gap junction type of plasmalemmal apposition. It is believed likely that the tannic‐acid‐induced pentalaminar complexes may incorporate the smaller heptalaminar ones. The factors underlying the plasmalemmal configurational differences between the tannic acid and non‐tannic‐acid material rema

ISSN:0002-9106    

DOI:10.1002/aja.1001860202

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

年代:1989

数据来源: WILEY

摘要:

AbstractNorepinephrine stimulates the growth in size of non‐dividing, neonatal cardiac muscle cells, and it can stimulate the growth in numbers of dividing hepatocytes and endothelial cells in culture. The objective of this study was to test the hypothesis that in dividing fetal cardiocytes, norepinephrine would stimulate growth in cell number rather than in cell size. Fourteen‐day fetal heart cells were placed in serum‐free or serum‐supplemented cultures in the presence or absence of norepinephrine (NE), NE plus propranolol, or isoproterenol for 4 days. Almost 90% of the cardiocytes in serum‐supplemented medium were in the cell cycle as determined by proliferating cell nuclear antigen (PCNA) antibody staining during this period. In addition, between days 2 and 4 of culture, 35% and 40% of these cardiocytes were labeled with3H‐thymidine. After 4 days the cardiocytes increased in cell number in the serum‐supplemented NE cultures as compared to serum‐free cultures. In contrast, there was no significant change in cardiocyte volume between any of the groups examined. It was concluded that in dividing muscle cell populations the effect of norepinephrine was to enhance cell proliferation rather than to stimulate cell

ISSN:0002-9106    

DOI:10.1002/aja.1001860203

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

年代:1989

数据来源: WILEY

摘要:

AbstractStudies were undertaken to describe the normal structure of the prairie dog gallbladder and adjacent cystic duct, and then to determine sequential changes that occurred as abnormalities in bile composition developed during high cholesterol feeding. Control animals were fed a diet with trace cholesterol, while experimental animals were fed a diet enriched with 1.2% cholesterol for 1, 2, 3, or 4 weeks. Light microscopy and scanning and transmission electron microscopy were used to characterize morphologic changes at each time interval. Biliary lipid composition was altered in all experimental groups, evidenced by significant decreases in bile‐acid‐to‐cholesterol ratios. Cholesterol crystals appeared in experimental bile at 1 and 2 weeks, while stones formed at 3 and 4 weeks. The cystic duct and neck of the gallbladder occasionally displayed goblet cells. Little mucus was demonstrable in principal cells of the gallbladder, but much more in those lining the cystic duct. After 2 weeks of lithogenic diet, there was an increase in mucus content and secretion from all areas, as well as an influx of polymorphonuclear and mononuclear leukocytes. Accumulation of plasma cells in the lamina propria was an especially prominent feature of experimental tissues. These results suggest that (1) there is regional heterogeneity in the mucus content of the gallbladder and cystic duct of the prairie dog, and (2) both regions respond to lithogenesis with mucus hypersecretion and acute and chronic inflammatory changes prior to the appearance of cholesterol galls

ISSN:0002-9106    

DOI:10.1002/aja.1001860204

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

年代:1989

数据来源: WILEY

摘要:

AbstractThe soleus muscles of fetal rats were examined by electron microscopy to determine whether the early differentiation of muscle spindles is dependent upon sensory innervation, motor innervation, or both. Simple unencapsulated afferent‐muscle contacts were observed on the primary myotubes at 17 and 18 days of gestation. Spindles, encapsulations of muscle fibers innervated by afferents, could be recognized early on day 18 of gestation. The full complement of spindles in the soleus muscle was present at day 19, in the region of the neuromuscular hilum. More afferents innervated spindles at days 18 and 19 of gestation than at subsequent developmental stages, or in adult rats; hence, competition for available myotubes may exist among afferents early in development. Some of the myotubes that gave rise to the first intrafusal (bag2) fiber had been innervated by skeletomotor (α) axons prior to their incorporation into spindles. However, encapsulated intrafusal fibers received no motor innervation until fusimotor (γ) axons innervated spindles 3 days after the arrival of afferents and formation of spindles, at day 20. The second (bag1) intrafusal fiber was already formed when γ axons arrived. Thus, the assembly of bag1and bag2intrafusal fibers occurs in the presence of sensory but not γ motor innervation. However, transient innervation of future bag2fibers by α axons suggests that both sensory and α motor neurons may influence the initial stages of bag2fiber assembly. The confinement of nascent spindles to a localized region of the developing muscle and the limited number of spindles in developing muscles in spite of an abundance of afferents raise the possibility that afferents interact with a special population of undifferentiated myotubes to form intrafusal

ISSN:0002-9106    

DOI:10.1002/aja.1001860205

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

年代:1989

数据来源: WILEY

摘要:

AbstractLight, scanning, and transmission electron microscopic observations related to morphological changes of the right atrium as well as the atrial endocardium during development (15th embryonic day and 1 day old) and aging (560 days old) in the Syrian hamster were described and correlated. From the fetus to the adult, the atrial endocardium differentiates in parallel with, or in response to, the subjacent proliferating myocytes in the atrial wall and the trabeculae. Simultaneously, the atrium compartmentalizes grossly into a main chamber and an appendicular region. There is a progressive differentiation from a rudimentary, open chamber with primitive mural ridges in the fetal atria to a distinct, separate, atrial main chamber and appendage with a dense network of trabeculae in the adult. The fetal and neonatal endocardial, endothelial cells are convex with a central nuclear bulging and attenuated cytoplasmic extensions; the adult endocardium shows a squamous endothelium. Two cell surface specializations were observed in all age groups: microvilli and blebs or cytoplasmic protrusions. The general atrial morphology and surface endocardial changes were correlated with growth and the role of the endocardial endothelium as a barrier which controls metabolic exchanges, including the transport of atrial natriuretic factor, between the myocytes and the blood. This endothelial function appears to be essential in the fetal and neonatal age groups since no blood vessels are detected in these groups.

ISSN:0002-9106    

DOI:10.1002/aja.1001860206

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

年代:1989

数据来源: WILEY

摘要:

AbstractThroughout the epithelial lining of the respiratory system is a class of cells with characteristics similar to Amine Precursor Uptake and Decarboxylation (APUD) polypeptide hormone‐producing cells. In the intrapulmonary airways, these small‐granule cells (SGCs) occur either singly or in organized clusters. Although no specific peptide has yet been identified, subclasses have been postulated based on granule geometry or light microscopic staining. The present study characterizes the architectonic and cellular organization of clustered SGCs in the adult Syrian golden hamster. Two morphologically distinct cells can be defined in such clusters, “light” and “dark.” This distinction was based primarily on differences in the electron density of the cytoplasmic matrix rather than on the remarkable variations in cellular organelles or dense‐core secretory vesicles. Both cell types were normal as judged by uniform spherical nuclei, chromatin organization, and distribution of cellular organelles. The “dark” cells, however, presented the profile of a cell actively involved in synthesis with a markedly dilated perinuclear cisterna and endoplasmic reticulum. Additionally, the “dark” cells contained membrane‐delimited structures containing concentric membranous whorls, clear vacuoles, and lipofuscin granules. Occasionally, cells were observed to contain features of both cell types, suggesting that they may represent a continuum of common cell lineage. Accordingly, in the absence of additional morphologic or biochemical data, the “light” and “dark” cells most probably correspond to different stages of functional activity or age‐related changes of a single type of cell. Unmyelinated nerve endings were occasionally interposed between cells, but synaptic specializations were not observed. Beneath the clusters, nerve fibers were also present, but they were never observed to penetrate the basal lamina or contact any of the SGCs. Of equal occurrence were elements of the vascular system and smooth muscle, suggesting that some SGCs in the adult hamster may function in a paracrine or endocrine manner. Such knowledge is essential to any study attempting to delineate the functional role or r

ISSN:0002-9106    

DOI:10.1002/aja.1001860207

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

年代:1989

数据来源: WILEY

摘要:

AbstractRecent evidence suggests that skeletal adaptation is organized by a functional unit that includes cells of diverse origin working in coordination. Genetic and metabolic factors control and regulate theprocessesof modeling and remodeling, only rarely acting on the isolated individual functions of specific cell lines. Errors in the genetic or metabolic regulation of the functional unit affect the entire process of skeletal adaptation rather than specific elements of it. Viewed in this way, some metabolic bone diseases can be understood as relatively simple errors in factors that control the coordinated activities of the entire functional unit. This paper reviews the modeling and remodeling processes and demonstrates how abnormal morphological characteristics of bone tissue can be viewed as products of specific errors in the adaptive process.

ISSN:0002-9106    

DOI:10.1002/aja.1001860208

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

年代:1989

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001860201

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

年代:1989

数据来源: WILEY