摘要:

AbstractZinc iodide‐osmium tetroxide (ZIO) is a nonspecific but selective impregnation method that visualizes a tubulo‐vesicular system in cells. The detailed structure and three‐dimensional distribution of this ZIO‐impregnated system was studied in the Tomes' process of secretory ameloblasts in the rat incisor. The ZIO‐impregnated system consisted of an extensive array of smooth membranebound thick and thin tubules and vesicles. The interconnected thick and thin tubules formed a complex “core network” in the central cytoplasm of Tomes' process that enmeshed and often surrounded individual secretory granules. From the core network, radial branches extended toward the smooth cell membrane of the interdigitating portion of Tomes' process. Although the core network and branches frequently appeared connected to the secretory granules and the cell membrane, stereo‐pair electron microscopy failed to show conclusive evidence of such continuity. However, many coated vesiclelike structures were attached to the core network and its branches. No special relationship was found between interrod and rod secretory sites and the tubulo‐vesicular network. In thick sections, the ZIO‐impregnated tubulo‐vesicular network occupied a considerable volume of cytoplasm. The vinblastine‐labile nature of this network as demonstrated previously (Nanci et al., 1987) indicated that the system undergoes rapid and extensive turnover. Considering the dynamic nature and sheer volume of the tubulo‐vesicular system, we propose that it be regarded

ISSN:0003-276X    

DOI:10.1002/ar.1092320302

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

年代:1992

数据来源: WILEY

摘要:

AbstractIn the current study, we determine the concentration of Dispase II, a neutral protease, and the incubation time necessary for isolation of embryonic avian epidermis. The epidermis can be isolated from the dermis consistently with or without the basal lamina. Because the action of Dispase II is selective and easily controlled, this study suggests that Dispase can serve as a powerful tool for studying epidermal‐extracellular matrix interactions. In further experiments we study the response of sheets of epidermis isolated with and without its basal lamina to extracellular matrix. When the epidermis is isolated without the basal lamina, the basal surface blebs and the actin in the basal cytoplasm are disrupted. Epidermis isolated without the basal lamina and cultured on extracellular matrix reorganizes the basal actin mat and retracts the blebs. However, epidermis isolated without the basal lamina and cultured in the absence of extracellular matrix continues to have blebs and a disorganized actin cortical mat. In contrast, the control epidermis isolated with the basal lamina retains a flat basal surface and organized actin cortical mat after culturing either with or without extracellular matrix. The extracellular matrix has been shown by many investigators to play an important role in cytoskeletal organization, metabolism, and differentiation. How the extracellular matrix interacts and influences these functions has not been completely elucidated. The ability to isolate tissue consistently with and without its basal lamina using Dispase II will facilitate addressing these and other epithelial cell biology question

ISSN:0003-276X    

DOI:10.1002/ar.1092320303

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

年代:1992

数据来源: WILEY

摘要:

AbstractAt the apex of the epithelial principal cells of the seminal vesicle, there appears to be two types of mature secretory granules, i. e., large and small. Both types of secretory granules showed an eccentric electron‐dense spherical body with one pole attached to the delimiting membrane. The remainder of the large granule surrounding the eccentric body showed a granulofilamentous texture, whereas that of the small granule was electron lucent. The formation of these two types of granules was traced back to the various elements of the Golgi stacks. In the case of the large granules, the earliest stage of segregation of the precursor of the eccentric dense body was observed in distensions of the cis‐element. Within distensions of all subjacent saccules, the dense bodies continued to be present but progressively increased in size while remaining attached to the saccular membrane. Following separation from the trans‐face of the stack, the large prosecretory granules continued to increase in size by fusing with each other. The very large prosecretory granules, as they migrated toward the cell apex to become mature secretory granules, reduced in size prior to exocytosis. The small granules formed exclusively on the trans‐aspect of the Golgi stacks and did not appear to fuse with each other. Observations on the formation of the large prosecretory granules within the Golgi apparatus and of the eccentric body in particular, which may be taken as a marker of the saccular membrane, were suggestive of a cis‐trans migration and renewal of Golgi

ISSN:0003-276X    

DOI:10.1002/ar.1092320304

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe generation of tension in granulation tissue undergoing contraction is believed to be a cell‐mediated event. In this study we used attached collagen lattices as a model system for studying the cellular mechanisms of tension generation by fibroblasts in an extracellular matrix. Fibroblasts in attached collagen lattices developed stress fibers, surface associated fibronectin fibrils, and a fibronexus‐like transmembrane association interconnecting the two structural components. Release of the attached collagen lattice from its points of attachment resulted in a rapid, symmetrical contraction of the collagen lattice. Rapid contraction occurred within the first 10 minutes after release of the lattice from the substratum, with greater than 70% of the contraction occurring within the first 2 minutes. Rapid contraction resulted in a shortening of the elongate fibroblasts and compaction of the stress fibers with their subsequent disappearance from the cell. Cytochalasin D treatment prior to release disrupted the actin cytoskeleton and completely inhibited rapid contraction. The removal of serum prior to release inhibited rapid contraction, while the re‐addition of serum restored rapid contraction. These results demonstrate that fibroblasts can develop tension in an attached collagen lattice and that upon release of tension the fibroblasts undergo contraction resulting in a rapid contraction of the collagen lattice. Fibroblast contraction is dependent upon an organized actin cytoskeleton and is promoted by the presence of

ISSN:0003-276X    

DOI:10.1002/ar.1092320305

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

年代:1992

数据来源: WILEY

摘要:

AbstractSatellite cell frequency was assessed in control and stretched anterior latissimus dorsi (ALD) muscles of adult quail. A weight equal to 10% of body mass was attached to one wing for time intervals ranging from 1–30 days. The contralateral ALD served as the intra‐animal control. Satellite cell frequency, expressed as a percentage of total myofiber nuclei within the basal lamina, was determined in eight control and stretched ALD muscles, that had been weighted for 5, 7, or 10 days. Satellite cell frequency was determined in 584 control and 473 stretched fibers and was not different in the control or stretched ALD muscles (15.6 ± 2.3%, 16.7 ± 6.1%, respectively). The number of myofiber nuclei (myonuclei and satellite cell nuclei) was examined in whole fiber segments from control and stretched ALD muscles of 27 adult quail. Nuclear frequency was determined in 500 control and 1,200 stretched fiber segments. Fiber volume was calculated from fiber length and diameter measurements. Nuclear number normalized to 10,000 μm3fiber volume was correlated to fiber cross‐sectional area (P<0.0001). Fibers with cross‐sectional areas less than 500 μm2had a greater nuclear to fiber volume ratio compared to fibers with areas greater than 500 μm2. The nuclear‐to‐cytoplasmic ratio was not constant in smaller fibers. Nuclear density decreased as fiber cross‐sectional area increased up to 500 μm2. Fibers with cross‐sectional areas greater than 500 μm2demonstrated a constant nuclear‐to‐cytoplasmic ratio. The results demonstrate that absolute nuclear number increased to maintain a constant nuclear‐to‐cytoplasmic ratio in the stretched hypertrophied fibers. Daughter cells originating from activated satellite cells may have contributed to the myonuclear population to maintain a constant nuclear‐to‐cytoplasmic ratio in the hyper

ISSN:0003-276X    

DOI:10.1002/ar.1092320306

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe articularis humeri (AH) muscle of the horse is a small muscle composed of histochemically identified type I and IIA extrafusal fibers and a large number of muscle spindles. A total of 150 complete spindles with both spindle poles available were examined in serial transverse sections. On the basis of myosin ATPase‐staining reactions after alkaline and acid preincubations, four types of intrafusal fibers, namely, bag1, bag2, “mixed” bag, and chain fibers, were identified.A high proportion of the spindle population (62.6%) consisted of multiple‐bag spindles containing three or more (up to six) bag fibers. Also one‐bag‐fiber spindles were observed. The one‐bag‐fiber spindles containing a bag2fiber could be traced into tandem linkages. “Mixed” bag intrafusal fibers, differing in their ATPase staining profile at the two poles, were found in spindles containing also at least one bag1and one bag2fiber. An unusually long extracapsular tract (up to 5,500 μm) of the bag intrafusal

ISSN:0003-276X    

DOI:10.1002/ar.1092320307

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe surface distribution of membrane‐associated dense plaques in intact quail gizzard smooth muscle cells was investigated by freeze‐fracture. Replicas of fractured smooth muscle cell plasma membrane showed caveola‐free regions with few intramembrane particles, interspersed with caveola‐populated areas with a higher intramembrane particle density. Electron microscopy of thin sections of quail gizzard smooth muscle revealed the regions free of caveolae to be occupied by membrane‐associated dense plaques; anchoring sites for the contractile filaments of the cell. Demarcation between the caveola‐populated and caveolafree regions on the relicated intramembrane surface was not clear and thus provided little information concerning the distribution of dense plaque sites. However, treatment of the smooth muscle tissue with the cholesterol‐binding agents filipin or tomatin prior to freeze‐fracture allowed the dense plaque sites to be easily observed as the sites remained free of the membrane deformations characteristic of these agents. The dense plaque sites consist of caveola‐free oval areas juxtaposed in regular bands that traverse the long axis of the cell. The dense plaque sites on the freeze‐fracture replica were confirmed by electron microscopy of thin sections of filipin‐treated quail gizzard smooth muscle cells, which showed the plasma membrane associated with the dense plaques to be unaffected by the actions of filipin, whereas that of the caveola‐populated region was severely deformed. The observations presented in this study provide evidence for a highly ordered distribution of dense plaques at the cell surface of intact quail gizzard smooth muscle cells and thus corroborate existing evidence for an organized substructure

ISSN:0003-276X    

DOI:10.1002/ar.1092320308

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe purpose of this study is to demonstrate the developmental changes of the experimental hydronephrotic kidney using immunohistochemical, histoplanimetrical, and Northern blot techniques. At 1 month after ligation of the ureter, a large number of renin‐positive cells were detected immunohistochemically even at a dilution of 1:10,000 in this hydronephrotic kidney; however, there were few renin‐positive cells in the non‐ligated side. At 6 months after ligation, no difference in reactivity for renin between ligated and non‐ligated kidneys was demonstrated. In the morphometrical analysis of the renin‐positive region, the numerical value of the ligated side was already increased at 2 weeks, reached the highest value at 1 month, and then decreased gradually to almost the same value as the control kidney by the end of the experiment. On the other hand, the value of the non‐ligated side decreased immediately after the unilateral ligation, increased later, and finally reached almost the same value as the control kidney. In the Northern blot analysis, the activity of renin mRNA in the ligated side at 1 month after ligation was markedly higher than that in the non‐ligated side. However, the difference between the ligated and the non‐ligated sides was not demonstrated at 6 months and the value came to be almost the same as in the non

ISSN:0003-276X    

DOI:10.1002/ar.1092320309

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe localization of sulfated glycoprotein‐1 (SGP‐1) in the extratesticular duct system was analyzed using an affinity purified antibody raised against the protein in conjunction with light (LM) and electron (EM) microscope immunocytochemistry. In the LM an intense immunoperoxidase reaction product was observed over the cytoplasm of Sertoli cells as well as over the tails of late spermatids. The rete epithelial cells and noncilliated cells of the efferent ducts also showed an intense uniform reaction over their entire cytoplasm. In the EM, immunogold labeling was noted over the entire endocytic apparatus of these cells including coated pits, endosomes, multivesicular bodies, and secondary lysosomes. Since there was no labeling of the luminal contents including sperm along the epididymis, it was concluded that the Sertoli‐derived SGP‐1 must dissociate from the sperm and be taken up by epithelial cells at the level of the rete testis and efferent ducts.In all regions of the epididymis, except the cauda, the principal cells showed, in the LM, an intense reaction over bodies of various shapes and sizes in their supranuclear region; this corresponded in the EM to a strong immunogold labeling of secondary lysosomes. No labeling was noted, however, over coated pits, endosomes, or pale multivesicular bodies, suggesting that SGP‐1 was not being endocytosed from the lumen. Similar observations were noted for the epithelial clear cells along the entire epididymis. In the cauda epididymidis, principal cells presented a weak immunolabeling of their secondary lysosomes.Northern blot analysis revealed a strong 2.6 Kb band corresponding to the mRNA of SGP‐1 in the efferent ducts and all regions of the epididymis with the exception of the cauda. Coincident with the mRNA expression of SGP‐1 it was found that small clusters of gold particles representing anti SGP‐1, presumably membrane bound, were associated with the Golgi apparatus as well as in close proximity to secondary lysosomes. There was, however, no evidence for the secretion of SGP‐1 into the lumen. These results suggest that SGP‐1 is synthesized by the epithelial cells of the male duct system and ferried by small vesicles derived from the Golgi apparatus to secondary lysosomes. Because SGP‐1 has recently been shown to have substantial sequence similarity to prosaposin, it may be speculated that SGP‐1 is instrumental in the degradation of membrane glycolipids present within secondary lysosomes of epithelial cells of the extr

ISSN:0003-276X    

DOI:10.1002/ar.1092320310

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe ductuli efferentes of Sprague‐Dawley rats were studied by microdissection and microscopic evaluation to document the presence of blindending tubules (ductuli aberrantes) and to describe morphological and ultrastructural differences between normally open ductules and blind‐ending tubules. The branching patterns of the ductuli efferentes varied considerably between animals. A majority of the animals studied had either six or seven ductuli connected to the rete testis, with some animals having as few as four or as many as eight. Pairs of ductules began merging in the conus vasculosa, ultimately forming a single terminal duct within the capsule of the initial segment epididymidis. In a majority of animals, the junctions were unequally matched and located at various positions within the conus. Blind‐ending tubules, found in 60% of the animals, were surrounded by thick connective tissue, and had a smaller diameter (78.7 ± 1.4 μm) than normal ductules in the conus vasculosa (119.5 ± 2.1 μm) or the terminus (102.2 ± 1.5 μm). The lumina of blind‐ending tubules were contracted and did not contain sperm. Nonciliated cells in the epithelium of blind‐ending tubules contained fewer PAS‐positive granules and electron‐dense bodies (lysosomes) than nonciliated cells in normal ductules. Consideration of these characteristics will prevent blind‐ending tubules from being mistaken for pathological changes

ISSN:0003-276X    

DOI:10.1002/ar.1092320311

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

年代:1992

数据来源: WILEY