摘要:

AbstractBlastomeres from eggs of the killifish,Fundulus, were mechanically dissociated and reaggregated by pelleting in a simple saline solution. Formation of gap and tight junctions was followed by electron microscopy of freeze‐ fracture replicas. Five to eight min after pelleting, neither new nor old junctions were observed. After 10–15 min, small gap junctions were found, but these were not associated with distinct formation plaques. Larger gap junctions were observed after 45 min, and the images were consistent with growth by accretion of intramembrane particles. In aggregates, after 20 min or more, tight junctions were much more commonly found than in intact blastulae, and it seemed likely that they were being formed by cells that were not doing so in the intact embryo. Initial stages consisted of short strands that appeared to grow in length. Also, more elaborate junctions were seen than occur in situ. Particle‐free membrane often occurred near incomplete junctions, and large junctions like those in situ separated particle‐rich from particle‐free membrane. In this system, the formation of both gap and tight junctions occurs with shorter latency, and is more precisely timed, than heretofore

ISSN:0002-9106    

DOI:10.1002/aja.1001580302

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

年代:1980

数据来源: WILEY

摘要:

AbstractGap junctions, related to projections of sensory cells into supporting cells, occur from supranuclear to basal levels on hair cells, in both saccular and utricular maculae of the lizard,Anolis carolinensis.The larger numbers of junctional projections observed at some levels may indicate a zonular distribution within the neuroepithelia, but only on supracalyceal parts of hair cells in the utricular striola was a series of gap junctions found to be closely associated with the reticular lamina. The dimensions of the junctions, as characterized by the distance between opposite extremities of the arciform membrane appositions, averaged 0.14, 0.19, and 0.28 μm, respectively, on non‐calyceal utricular and saccular hair cells, and calyceal cells of the utricular striola. A notable number of the junctional profiles were adjacent or contiguous to open, coated, putatively endocytotic vesicles. These findings are discussed in respect to phylogenetic, developmental, and functional consideratio

ISSN:0002-9106    

DOI:10.1002/aja.1001580303

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe present electron microscopic cytochemical investigation was undertaken to characterize the alterations in the Golgi apparatus and GERL of rat parotid acinar cells during ethionine intoxication and recovery. Although the Golgi apparatus and GERL were reduced in size, and some broadening of the Golgi saccules occurred as the result of ethionine treatment, the relative localization of thiamine pyrophosphatase (TPPase) activity in the Golgi saccules, and acid phosphatase activity (AcPase) in GERL, remained unchanged. Shortly after ethionine treatment was stopped, a dramatic redistribution of enzyme activities was noted. Within the first 24 hours of recovery, the Golgi apparatus began to enlarge, and the content of secretory granules increased. By day 3 of recovery, cisternae morphologically identifiable as GERL and forming secretory granules possessed TPPase activity, while AcPase activity was virtually undetectable. After seven days of recovery, the Golgi apparatus and GERL appeared both morphologically and cytochemically normal. The enzyme modulation observed during recovery may be correlated with increased secretory granule production. Furthermore, the presence of TPPase activity in GERL and forming secretory granules lends support to the suggestion that GERL may be derived from the trans Golgi saccule.

ISSN:0002-9106    

DOI:10.1002/aja.1001580304

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe cytodifferentiation of the intestinal Paneth cell was investigated in 2‐ to 50‐day‐old rats by evaluating the phenotypic expression of bacteriolytic lysozyme. Samples of duodenum, jejunum, and ileum were exposed to anti‐lysozyme antiserum and treated by the periodic‐acid Schiff (PAS) technique for the demonstration of carbohydrate moieties. The distribution of the Paneth cell population was then assessed.At days 3‐6, Paneth cells were present in ≤ 1% of intestinal crypts and exhibited (a) location in the bases of crypts, (b) apical granules positive for lysozyme, and (c) a slender truncated shape extending to the crypt lumen. By days 6‐8, Paneth cells had acquired their typical broad, truncated shape and prominent secretory apparatus. Between 1 and 7 weeks postpartum, the frequency of Paneth cellcontaining crypts in duodenum rose from 9% to 79%; in jejunum and ileum the frequency increased through the third week of life and stabilized at 77%–93% thereafter. At all ages, a rostro‐caudal gradient of crypts containing Paneth cells was observed, and greater numbers of paneth cells per crypt were seen caudally. In both suckling and weanling animals, two intermediate cell types were encountered. The first predominated at crypt bases through the fourth week of life and contained lysozyme‐positive supranuclear granules, concomitant with an apical aggregation of PAS‐positive material. The second type, identical to goblet cells in size and shape, predominated along the walls of intestinal crypts and at the bases of villi, and manifested both lysozyme‐positive granules and PAS‐positive mucigen droplets in the apical cytoplasm. This cell type appeared by day 12 and persisted through day 50.The results of this study provide further evidence that Paneth cells differentiate from a subpopulation of multipotent stem cells residing at crypt bases. The observation of Paneth cell‐goblet cell transitional forms supports the view that these two cell

ISSN:0002-9106    

DOI:10.1002/aja.1001580305

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

年代:1980

数据来源: WILEY

摘要:

AbstractParotid glands of rats were prepared for light and electron microscopy and for the histochemical demonstration of myofibrils and alkaline phosphatase (AkPase) activity. Through 18 days in utero, the epithelial cells of the developing gland remain relatively undifferentiated. At 20 days in utero, a few cells in the outer layer of the terminal buds and adjacent segments of ducts acquire a cilium, the initial indication that they are differentiating into myoepithelial cells (MEC). Up until the time of birth, the only additional characteristics of MEC that the outer cells develop are to flatten against the underlying cells, begin to send out processes, and produce a few dilated cisternae of rough endoplasmic reticulum. Myofibrils and AkPase activity are first detected at the light microscopic level at five days after birth, around both the developing acini and intercalated ducts. Progressive increases in AkPase activity and in the size and number of myofibrils continue until the acini and intercalated ducts are invested with well‐differentiated MEC at 15 days. Subsequently, as the acini undergo maturation during the weaning period (18‐25 days), the MEC cease to surround the acini and assume the adult pattern of investing only the intercalated ducts. The pattern of MEC differentiation in the parotid gland differs from those in the sublingual and submandibular glands of the rat in several important respects. They begin to differentiate last, yet mature almost as early as do the MEC of the sublingual gland; they begin to differentiate prior to, rather than simultaneously with, the secretory cells; and their distribution changes as the acinar cells become mat

ISSN:0002-9106    

DOI:10.1002/aja.1001580306

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

年代:1980

数据来源: WILEY

摘要:

AbstractTurnover of cells within the odontogenic organ was studied in three dimensions by preparing serial sections of incisors from young male rats killed at various times following a single intraperitoneal injection of 1 μCi/g body weight of3H‐thymidine. Radioautographs showed that at 1 hour after injection labeled cells were present in all cell layers throughout the entire depth of the odontogenic organ. They were encountered frequently within the inner dental epithelium and stratum intermedium but appeared less abundant within the stellate reticulum and outer dental epithelium. With time, the frequency of labeled cells in each layer declined progressively, and more rapidly at the anterior and labial side of the odontogenic organ than toward its posterior and lingual side. Hence labeled cells were observed over the longest time interval in regions where cell layers were in closest proximity to the opening of the apical foramen, that is, near the apical and cervical loops. By 32 days after injection, numerous labeled cells could still be identified within the outer dental epithelium and stellate reticulum near the apical loop (bulbous part of the odontogenic organ) and the outer dental epithelium near the cervical loops (“U”‐shaped part of the odontogenic organ). These findings support the hypothesis that cells originate within the bulbous part of the odontogenic organ and migrate anteriorly through the “U”‐shaped and root sheath parts of the odontogenic organ during renewal of the incisor. It appears that individual stem cell compartments may be maintained for surface (outer/inner dental epithelium) and intermediate layers (stellate reticulum/stratum intermedium) in the odontoge

ISSN:0002-9106    

DOI:10.1002/aja.1001580307

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe atrioventricular (AV) node and surrounding transitional zone in the ferret heart were examined with scanning electron microscopy. This permitted the direct visualization of the three‐dimensional cell shape, as well as intercellular relationships. Transitional cells were roughly cylindrical with extensively branching end processes. These cells were apposed to many adjacent transitional cells. The superficial AV nodal cells were smaller than transitional cells and were fusiform in shape. Most of the cell contacts between superficial AV nodal cells were between overlapping end processes, and there was very little branching of these cells. The deep AV nodal cells were similar to the superficial AV nodal cells, but were slightly larger and also had more cell contacts with adjacent cells. The possible significance of cell size and shape and intercellular relationships as they relate to atrioventricular impulse propagation and AV nodal delay are discusse

ISSN:0002-9106    

DOI:10.1002/aja.1001580308

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

年代:1980

数据来源: WILEY

摘要:

AbstractVolume densities of type‐I and type‐II alveloar cell cytoplasmic organelles were estimated by established stereologic procedures. The measurements were obtained from isolated‐perfused dog lungs after the onset of acute hydrostatic edema. The isolated lungs provided three successive lobar preparations: control, moderately edematous, and severely edematous. The type‐II cell lamellar body volume densities were decreased in both stages of edema. Volume density of the granular endoplasmic reticulum (including polyribosome clusters) was increased after progression to severely edematous conditions. Concomitant increases in vesicular volume densities were recorded in type‐I cells after both moderate and severe edema. In addition, the relative percentages of vesicles directly attached to the luminal and abluminal plasma membranes were increased in the edematous lungs. These marked ultrastructural changes in the alveolar epithelium are consistent with the interpretation that both the release of lamellar bodies from type‐II cells and the number of type‐I cell pinocytotic vesicles are increased in isolated dog lungs after produc

ISSN:0002-9106    

DOI:10.1002/aja.1001580309

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

年代:1980

数据来源: WILEY

摘要:

AbstractEffects of inhibition of protein synthesis by actinomycin D (ACT) on the acute stimulation of hepatic gluconeogenesis and glucose‐6‐phosphatase (G6Pase) by the glucocorticoid, dexamethasone (DEX), in adrenalectomized (ADX) rats, were investigated using both morphological and biochemical means. Examination of ultra‐thin sections of liver in the electron microscope revealed that ACT, administered alone or with DEX, resulted in a failure of hepatic glycogen accumulation to occur. Smooth endoplasmic reticulum (SER) appeared similar to that of the ADX‐untreated animals, with occasional suggestions of increased amounts of membrane in ACT‐treated animals. G6Pase activity in homogenates was increased, as was activation of the enzyme under all experimental conditions, when compared with ADX‐untreated controls. The DEX‐induced increase in G6Pase activity in SER failed to occur to any appreciable extent in ACT‐treated animals. Plasma glucose levels increased slightly when ACT and DEX were present simultaneously.It is suggested that ACT countered the inductive effects of DEX on hepatic glycogen synthesis, but only partially suppressed acute stimulation of gluconeogenesis. A possible superinduction of G6Pase enzyme synthesis through increased efficiency of translation of extant mRNA is discussed. It is proposed that ACT inhibited the formation of appropriate SER membranes and/or other components necessary for glycog

ISSN:0002-9106    

DOI:10.1002/aja.1001580310

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

年代:1980

数据来源: WILEY

摘要:

AbstractCartilage slices from normal rats, incubated at pH 4 for 3 to 7 hours, on a gelatin‐membrane substrate, digested the membrane, whereas cartilage from rats hypophysectomized for 21 days or more did not. Injection of 15 or 45 μg of bovine growth hormone into hypophysectomized rats restored the lytic activity of the cartilage. It is concluded that an acid proteinase is present in cartilage of normal rats, that is lost after hypophysectomy, and that the enzyme is restored by injection of growth hormo

ISSN:0002-9106    

DOI:10.1002/aja.1001580311

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

年代:1980

数据来源: WILEY