摘要:

AbstractBackground: In the yeastSaccharomyces cerevisiae, the Golgi apparatus consists of discrete units distributed throughout the cytoplasm. When such units are examined in three dimensions, in relatively thick sections prepared for the electron microscope, they usually appear as small tubular networks with a stained material accumulating in dilations located at the junctions of membranous tubules. To see whether such tubular networks are observed in other yeast species, the three‐dimensional structure of organelles in eight additional yeast strains, endowed with diverse biological properties, are examined.Methods: Yeast strains were grown at 24°C in YPD medium (2% Bactopeptone, 1% Bactoyeast extract, and 2% glucose). Cells that were examined by electron microscopy came from exponentially growing cultures grown in a shaking water bath and maintained at a OD 600 (optical density at 600 nm) of 0.5. Cells were fixed in a fixative containing 2% glutaraldehyde in 0.1 M cacodylate buffer pH 7.4 and 0.8 M sorbitol. They were then treated for 15 min in 1% sodium metaperiodate and postfixed for 1 hr in potassium ferrocyanide‐osmic acid. They were preembedded in agarose prior to dehydration and finally embedded in Epon. In these conditions, the preservation of cell organelles was improved and the cytoplasmic retraction from the cell wall was minimized. Photographs of sections tilted at ± 15° from the 0° position of the goniometric stage were used to prepare stereopairs from which the three‐dimensional configuration of the organelles was visualized.Results: In all yeast strains, tubular networks appeared as separate elements or units dispersed throughout the cytoplasm. Each unit consisted of anastomosed membranous tubules. In some strains such asSaccharomyces cerevisiae, Zygosaccharomyces rouxii, or Saccharomyces pombe, such units appeared mainly as polygonal networks of intensely stained membranous tubules. Along these networks, distensions filled with stained material were similar in size to nearby secretory granules, suggesting that the latter formed by fragmentation of the tubular networks. InHansenula polymorpha, Pichia pastoris, andDebaryomyces hansenii, networks of anastomosed tubules were closely superposed to each other and formed parallel arrays reminiscent of the stacks of Golgi saccules seen in mammalian cells. However, in contrast to what is usually found in the latter, the layers making up the parallel arrays in yeasts, were clearly continuous to each other. In other strains, i.e.,Kluyveromyces lactis, Candida albicans, andCandida parapsilosis, the situation was intermediate and their cytoplasm contained only arrays of small size with two or at most three superposed layers of membranous tubules. Small vesicles in the 30–50 nm range were rarely encountered in most yeast strains.Conclusions: It is therefore concluded that tubular networks, presumably Golgi in nature, are present in all yeasts examined so far. Yet, in some strains, these tubular networks may be arranged in parallel arrays or stacks. © 1995 Wil

ISSN:0003-276X    

DOI:10.1002/ar.1092430302

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

年代:1995

数据来源: WILEY

摘要:

AbstractBackground and Methods: The association of masseter tendon type VI collagen with other extracellular matrix (ECM) components was examined from osseous attachment to myotendinous junction by immunohistochemistry and transmission electron microscopy with ATP treatment and enzyme digestion.Results: In the tendon proper, fibrocytes extended their processes among bundles of striated collagen fibrils and associated with adjacent cells through amorphous materials, thus forming a three‐dimensional network. The amorphous or filamentous material was observed around the fibrocyte cell body and along the cell processes, where the localization of type VI collagen was confirmed by immunohistochemistry using anti‐type VI collagen antibody. After treatment with 20 mM adenosine 5′‐triphosphate (ATP), 100 nm periodic fibrils, an aggregated form of type VI collagen, were formed in the place where amorphous or filamentous material was present before the treatment. In myotendinous junction, the ATP‐aggregated periodic fibrils were observed to associate with the external lamina of the muscle cells as well as among junctional tendon collagen fibrils. In the tendonbone boundary, ATP‐aggregated periodic fibrils were observed around fibrocartilage‐like cells in the uncalcifying area but not in the calcification front. Prolonged ATP treatment or hyaluronidase predigestion caused the formation of type VI collagen periodic fibrils in the area near the calcified matrix.Conclusions: The distribution of type VI collagen in mouse masseter tendon is different in different anatomical position. This may reflect the different functional demand for this collagen. © 1995 W

ISSN:0003-276X    

DOI:10.1002/ar.1092430303

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

年代:1995

数据来源: WILEY

摘要:

AbstractBackground: In general the ultrastructure of secretory cells can be modified under secretory stimulated and non‐stimulated conditions. The ultrastructure of the lingual salivary glands of hibernating salamanders in the natural environment was examined and compared to those of fasted and fed animals kept in the laboratory.Methods: Hibernating salamanders of the speciesHynobius tokyoensiswere collected from the natural environment during the winter breeding season and sacrificed for this study. One group was sacrificed immediately, another group was kept under fasted condition, and another group was regularly fed; both of the latter groups were kept at room temperature for 1 month and then sacrificed. The tongue was fixed for electron microscopy and processed by conventional methods, and semithin sections were histochemically examined for glycoconjugates.Results: The lingual salivary glands of this salamander species were composed of simple or often branched tubular glands opening onto the dorsal surface of the tongue. The secretory cells which composed their terminal portions were all columnar in morphology and histochemically mucous in nature. Under hibernation or prolonged fasting at room temperature, the mucous granules of these columnar secretory cells were decreased in number and the Golgi apparatus appeared inactive. A conspicuous structural peculiarity was multiple fingerprint‐like structures of the rough‐surfaced endoplasmic reticulum (RER). Most of these membranes were composed of stacks of tightly packed cisternae. Under regular feeding, the mucous granules were closely packed in the cytoplasm of the secretory cells and the basal necleus was slightly enlarged. The Golgi apparatus showed progressive activation with distended saccules. The unique membranous arrangement of the RER which was observed in the fasting animals was completely absent, and the cisternae were irregular in width with considerable variation of the intercisternal spaces.Conclusions: The tongue of the salamanderH. tokyoensishas numerous tubular salivary glands which are mucous in nature. The architecture of the organelles in the secretory cells is subject to modification in response to the cellular metabolism. © 1995 Wiley‐L

ISSN:0003-276X    

DOI:10.1002/ar.1092430304

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

年代:1995

数据来源: WILEY

摘要:

AbstractBackground: Hypolemmal nerve terminals, which are abundant in many types of salivary glands, are naked axons that have penetrated the basement membrane to take up a position between adjacent parenchymal cells. Although they may form vesicle‐filled varicosities, there usually are no obvious morphological indications as to which cell actually is being innervated.Methods: Specimens of over 200 species of bats were live‐trapped and their major salivary glands extirpated and prepared for electron microscopic examination.Results: In 13 species of bats out of the more than 200, mitochondria‐hypolemmal nerve terminal complexes were observed in different sites in different salivary glands. In these 13 species, mitochondria in epithelial cells that abut nerve varicosities are closely applied to the plasma membranes of their cells to follow the contours of these nerve elements. The complexes so formed often consist of a varicosity flanked by two mitochondria in separate cells. In intensely innervated glandular segments, mitochondria may be apposed not only to varicosities, but to the axonal portions of these nervous elements as well.Conclusions: The physiological significance of such complexes is unknown; it is conceivable that the mitochondria facilitate signal transmission or play a role in local calcium homeostasis related to nerve function. © 1995 Wiley‐L

ISSN:0003-276X    

DOI:10.1002/ar.1092430305

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

年代:1995

数据来源: WILEY

摘要:

AbstractBackground: Previous studies have shown that the trochlear notch is deeper than necessary for an exact fit with the humerus. However, humero‐ulnar joint space width and contact areas have so far not been quantified for variations in the load and angle of flexion.Methods: Six fresh cadaveric specimens were investigated at 30°, 60°, 90°, and 120° of flexion and at loads of 25 and 500 N, simulating resisted elbow extension. The joint space width and contact were determined, using polyether casting material.Results: At 25 N all joints made contact in the ventral and dorsal aspects of the articular surfaces, whereas in the depth of the trochlear notch the joint space was on average between 0.3 and 2.8 mm wide, with some variation between individuals. At 500 N the joint space width was considerably reduced and the contact areas expanded towards the depth of the notch. The size of the dorsal contact areas was significantly smaller at 30° and that of the ventral ones at 120°, their ventro‐dorsal ratio decreasing considerably from 30° to 120° (P<0.01).Conclusion: These results indicate that the size of the contact areas depends to a slight extent on the joint position, but that at all loads and flexion angles a bicentric contact and an important central joint space width emerge because of the concave incongruity of the joint, These data may be used for numerical calculations, analysing the effects of incongruity on the joint stress and on the functional adaptation of the subarticular tissues. © 1995 Wil

ISSN:0003-276X    

DOI:10.1002/ar.1092430306

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

年代:1995

数据来源: WILEY

摘要:

AbstractBackground: A deeper joint socket (concave incongruity) is found at most angles of flexion of the humero‐ulnar joint and maintained over a wide range of physiological loading. It is, however, unclear how far this incongruity affects the distribution of load and subchondral mineralization of this joint as compared with a congruous configuration.Methods: Two nonlinear, axisymmetrical finite element models with two cartilage layers were constructed, one congruous and one incongruous, with a joint space of realistic magnitude. The distribution of subchondral mineralization was determined by computed tomography osteoabsorptiometry in the same six specimens that were investigated in the first part of the study, and compared with the biomechanical data obtained there and the predictions of the models.Results: In the congruous case, the center of the socket is highly loaded, whereas the periphery does not experience mechanical stimulation. A central bone density maximum is predicted. With concave incongruity the position of the contact areas shifts from the joint margin towards the center as the load increases, and the peak stresses are considerably lower. A bicentric ventro‐dorsal distribution pattern of subchondral mineralization is predicted, and this is actually found in the six specimens.Conclusions: Concave incongruity is shown to determine load transmission and subchondral mineralization of the humero‐ulnar joint. It is suggested that this shape leads to a more even distribution of stress, provides intermittent stimulation of the cartilaginous tissue, and has beneficial effects on the metabolism, nutrition, and lubrication of the articular cartilage during cyclic loading. © 1995 Wiley‐L

ISSN:0003-276X    

DOI:10.1002/ar.1092430307

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

年代:1995

数据来源: WILEY

摘要:

AbstractBackground: There is little agreement as to the secretory process of renin granules in juxtaglomerular granular cells (JG cells) of kidneys, although a large number of studies of the regulation of renin secretion have been reported.Methods: The structural correlation between the stimuli and the secretory process was examined in mouse JG cells on renal cortical slice incubated with the beta‐adrenergic agonist, isoproterenol; the loop diuretic, furocemide; the Ca2+chelator, EGTA; and the actin filament‐disrupting agent, cytochalasin B.Results and Conclusions: Treatment with isoproterenol (10−5−10−3M) or furocemide (10−3M) in Ca2+‐containing medium did not significantly affect the ultrastructure of JG cells. In slices incubated with isoproterenol or furocemide in the Ca2+‐free medium, JG cells occasionally contained a few electron‐lucent granules at the cell periphery in addition to the electrondense mature granules observed in the control slices. On rare occasions, the JG cells displayed omega‐shaped cavities with electron‐lucent matrices, a feature similar to the contents of electron‐lucent granules. Cytochalasin B markedly promoted the effects of these stimulants in Ca2+‐free medium. These findings suggest the participation of actin filament disassembly in the exocytotic process of the mature granules in JG cell

ISSN:0003-276X    

DOI:10.1002/ar.1092430308

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

年代:1995

数据来源: WILEY

摘要:

AbstractBackground: Bovine oviduct epithelial cells are widely used in co‐culture experiments to improve early embryonic development and in vitro fertilization in embryo transfer programmes for domestic animals.Methods: The present study compares different methods for harvesting and culture of bovine oviduct epithelial cells in order to optimize handling. Bovine oviduct epithelial cells were mechanically or enzymatically isolated and cultured on glass, on permeable membranes, or in suspension. Growth of the cells and their state of differentiation was examined by means of classical staining methods, immunohistochemistry and electron microscopy.Results: Initial cell suspensions contained sheets of ciliated and nonciliated (secretory) cells; 24 h after seeding, free floating epithelial cells formed vesicles with cilia on their external surface. First adhesion of cells was seen 72 h after seeding. Later on, cells grew continuously and confluent monolayers were formed after 7 days. Results were identical after mechanical or enzymatical cell harvesting and were identical on both substrata tested, i.e., on glass and on permeable membranes. Light and electron microscopy proved the monolayers to resemble a polarized, simple, cuboidal to columnar epithelial membrane with intact junctional complexes and numerous apical microvilli. Their epithelial nature was established by immunostaining for cytokeratins. Cilia were missing and secretory granules were scarce. A layer of acidic glycoprotein material was demonstrated on the apical surface. Monolayers of bovine oviduct epithelial cells stored lipid droplets and large quantities of glycogen. About 50% of the seeded cells did not adhere but survived in the culture medium as free floating cells. These suspended cells maintained morphological criteria of differentiation (cilia and secretory granules) until day 12 of culture. Proliferation rates of cultivated cells were determined by counting mitoses and by immunostaining with MIB1 antibody. Results showed coincidence of rapid proliferation and morphological dedifferentiation of monolayers. Suspended cells, by contrast, did not proliferate but retained cellular differentiation under identical culture conditions.Conclusions: The results strongly suggest that monolayers of bovine oviduct epithelial cells will not fully substitute for original oviduct epithelium when used in co‐culture experiments after in vitro fertilization. © 1995 Wiley‐Lis

ISSN:0003-276X    

DOI:10.1002/ar.1092430309

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

年代:1995

数据来源: WILEY

摘要:

AbstractBackground: The bronchial circulation affects both pulmonary vascular and airway activity. Fundamental to understanding the role of the bronchial microcirculation in health and disease is understanding its anatomy. This study sought to identify specific structural elements that might contribute to the drop that occurs between the systemic blood pressure of the bronchial artery and the low pressure of the pulmonary bed into which the bronchial circulation flows and to better describe the connections of the bronchial and pulmonary circulations. METHODS: To do this, the lungs of five sheep were cast by injecting a resin through bronchial and pulmonary arteries. After taking samples for light microscopy, the tissue was digested and the casts were viewed with a scanning electron microscope. RESULTS: Casts of extrapulmonary bronchial arteries were structurally similar to other systemic arteries. Tortuous ones spiraled around bronchi and large blood vessels. Intrapulmonary bronchial arteries, about 100–300 μm in diameter, had sharp branching and deep focal constrictions with great rugosity that completely shut off the flow of the resin. These vessels correspond to theSperrarteriendescribed by von Hayek (and could cause the resistance associated with the pressure drop). Vasa vasorum ran in the walls of intrapulmonary pulmonary arteries for a variable distance before they entered the lumens of the pulmonary arteries. The smallest blood vessel found that was supplied with vasa vasorum was a bronchial artery 42 μm in diameter. Capillary‐like networks with large luminal diameters were found on the pleural surface. CONCLUSIONS: Scanning electron microscopy of microvasular casts provides a fresh description of the bronchial circulation, further delineates the communications of these two circulations, and may structurally account for some pressure drop between the bronchial and pulmonary circulations. © 1995 Wiley‐L

ISSN:0003-276X    

DOI:10.1002/ar.1092430310

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

年代:1995

数据来源: WILEY

摘要:

AbstractBackground: The leaflet tissue of the mouse atrioventricular (AV) valves contains a system of wavy collagen bundles that organize like tendons, orientate along lines of tension, and constitute an essential component of the valve tissue. The organization of these bundles is different in the two AV valves, reflecting differences in the anatomy of the entire valvular complex. Further insights into this kind of organization are needed to gain a complete understanding of the functional anatomy of the mouse AV valves.Methods: The endocardial covering of the mouse AV valves (from 21 days to 1 year of age) was eliminated by the sonication or the maceration method. This allowed us to study in situ the organization of the collagenous valve skeleton, as well as the structure of the myotendinous junction.Results: The leaflets of the two AV valves are formed by a fibrous layer (on the ventricular side) and a spongy layer (on the atrial side). The fibrosa is formed by undulating collagen bundles that organize and orientate differently on the right and left sides. The spongiosa is formed, on both sides, by a loose network of thin collagen fibers with no apparent orientation. Myocardial cells in the papillary muscles of the tricuspid valve are elongated and show cone‐shaped tips. Collagen fibers attach to the myocyte surface. Collagen struts and thin septa can also be recognized. On the other hand, the collagenous components of the mitral leaflets attach tangentially to the mitral papillary muscles. On the two sides, the myocytes appear to be ensheathed in a layer of collagenous tissue. The sheaths are formed by circularly arranged fibers and appear to be tightly interconnected.Conclusions: The differences in the collagenous organization between the two AV valves reflect differences in the gross anatomy of the valves. The attachment of collagen to the papillary myocytes in the tricuspid valve resembles that of a typical myotendinous junction. However, the collagenmuscle junction in the mitral valve is more similar to the structure of a pennate muscle.The collagen matrix of the heart has been divided into endomysial, perimysial, and epimysial components. The presence of sheaths housing individual myocytes and capillaries, struts, and thin septa, corresponds to the endomysium. The absence of perimysial septa, which aggregate myocytes into groups, is striking, but this may just be a species difference. The appropriateness of the term epimysium, as applied to the heart, is discussed. © 1995 Wiley‐Liss,

ISSN:0003-276X    

DOI:10.1002/ar.1092430311

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

年代:1995

数据来源: WILEY