摘要:

AbstractIn adult Sertoli cells of most strains of mice, all the centromeric heterochromatin is condensed in two chromocenters, one on each side of a single, large nucleolus. In a random‐bred Swiss OF‐1 strain, however, the nucleus has a different structural organization. Part of the heterochromatin is seen as chromocenters in contact with the nucleolus; the rest of it is dispersed in granules of unequal size in the nucleoplasm. Such an unusual spatial arrangement of heterochromatin in interphase nucleus cannot be explained either by a difference in the nucleolar organizing regions or by a polymorphism of the C‐banding of metaphase chromo

ISSN:0003-276X    

DOI:10.1002/ar.1092050402

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe seminiferous epithelium in mature vasectomizedMacaca fasciculariswas examined quantitatively to assess spermatogenesis. Monkeys were bilaterally vasectomized and controls were bilaterally sham operated. At postoperative periods of 10 and 18 months, groups of monkeys were castrated and their testes prepared for morphologic analysis. Diameters were measured in 100 cross sections of seminiferous tubules from each animal. Numbers of spermatogonia (Ad and Ap), preleptotene spermatocytes, pachytene spermatocytes, and step 7 spermatids, relative to Sertoli cell nucleoli, were counted in stage VII tubules. Tubule diameter and germ cell numbers per Sertoli cell nucleoli were not altered by vasectomy. Our study demonstrates quantitatively that spermatogenesis in the monkey is not inhibited up to 18 months following vasectomy.

ISSN:0003-276X    

DOI:10.1002/ar.1092050403

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

年代:1983

数据来源: WILEY

摘要:

AbstractIntercellular junctions between Sertoli cells in the toad testis were studied by freeze‐fracture and electron‐opaque intercellular markers. These junctional specializations are characterized in thin sections by a series of focal fusions on the outer leaflets of both adjacent cell plasmalemmas, associated with bundles of fine filaments in the subjacent Sertoli cell cytoplasms. However, the wide subsurface cisterna of the endoplasmic reticulum, a component constantly associated with Sertoli cell junctions in mammals, is absent in the toad. The intravascularly injected lanthanum hydroxide, used as a tracer compound, gains access to the seminiferous tubules and surrounds spermatogonia and leptotene spermatocytes, but is persistently excluded from germ cells in later stages of development. This indicates that, as is the case in the mammalian testis, a permeability barrier to lanthanum is established which isolates all germ cells beyond leptotene spermatocytes.Freeze‐fracture reveals the characteristic occluding junctions between Sertoli cells, but a variation in their geometric patterns was clearly observed in different regions of the toad seminiferous epithelium. The membrane‐fractured faces of Sertoli cells embracing differentiating spermatids exhibit a deep junctional complex: up to 50 rows of particles between adjacent Sertoli cells separate these late germ cells from the periphery of the seminiferous tubules. Sertoli cells surrounding early germ cells generally exhibit, instead, a discontinuous, poorly developed network of interconnected rows of particles with few widely spaced strands. This seems to permit the percolation of the intercellular marker in areas of the seminiferous epithelium containing spermatogonia and leptotene sperma

ISSN:0003-276X    

DOI:10.1002/ar.1092050404

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

年代:1983

数据来源: WILEY

摘要:

AbstractPulmonary arteries were fixed by perfusion under constant pressure and filled with rubber. The hardened rubber cast delineated the arterial bed, permitting dissection of axial vessels and all branches. Each segment was prepared for scanning electron microscopy and transmission electron microscopy. Branches arising at acute angles from the axial artery and the first two generations of its branches, regardless of diameter, had the same concentric muscle layer structure as parent vessels. Endothelial cells of the parent vessel were oriented into the ostia of these branches. Branches that came off the axial vessel or its branches at right angles had spiral muscle bundles and led to nonmuscular precapillary vessels. Right angle branches also had similar wall structure regardless of diameter. Near the ostia of right angle branches, endothelial cells of the parent vessels did not show orientation of their long axis into the branch lumens. It was concluded that branch arteries arising at acute angles are conduits which carry blood to distant parts of the lung while right angle branches are a histologically different group which distribute the blood to local capillary beds.

ISSN:0003-276X    

DOI:10.1002/ar.1092050405

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

年代:1983

数据来源: WILEY

摘要:

AbstractDifferentiation of preodontoblasts to odontoblasts and preameloblasts to ameloblasts during development of the mouse mandibular incisor proceeds in a gradient from the area of the odontogenic organ, where undifferentiated ectomesenchymal and epithelial cells proliferate, toward the incisal tip where mature tooth tissues, dentin and enamel, are present. The freeze‐fracture technique has been used in the work presented here to study cell membrane ultrastructure of preodontoblasts and preameloblasts at several stages of differentiation. At early stages of differentiation, cuboidal preameloblasts are joined together distally by numerous gap junctions. Relatively fewer junctions occur elsewhere on the lateral plasma membranes, but gap junctions frequently occur proximally between preameloblasts and stratum intermedium cells. As differentiation proceeds and the cells become columnar, distal and proximal junctions persist. Tight junctions, however, were not observed at any of the stages studied. Intramembrane particle concentration of the lateral preameloblast plasmalemma appears to increase as differentiation proceeds. Odontoblasts are also joined distally by numerous gap junctions which persist through later stages of differentiation. Although odontoblast cell processes were observed to project toward the preameloblast layer, no clear points of cell to cell contact or defined intercellular junctions between the two cell types were observe

ISSN:0003-276X    

DOI:10.1002/ar.1092050406

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe number of nerve fibers entering a tooth gives an indication of the tooth's capacity to perform a sensory function. Nerve fiber development was quantitated from cross sections of the apical portions of 49 erupted human premolars at various stages of root development and in subjects up to 71 years of age. Neural development was incomplete in immature teeth, greatly variable in young mature teeth, and complete in older teeth. Myelinated axons changed in number but not in size during tooth development. There were significantly fewer myelinated axons in teeth with open and parallel apical foramina than in older teeth. Unmyelinated axons did not change significantly in number with development but fewer large axons were found in older teeth. The number of unmyelinated axons enclosed in a single boundary lamina tended to be lower in older teeth. As a physiologic correlate, threshold responses to electrical stimulation were also determined prior to premolar removal. Threshold stimulation decreased significantly with apical foramen maturation. A significant negative correlation was found between the threshold stimulus and the number of myelinated axons in fully developed teeth, but not in immature teeth.

ISSN:0003-276X    

DOI:10.1002/ar.1092050407

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

年代:1983

数据来源: WILEY

摘要:

AbstractThe effects of maternal dexamethasone (DEXA) administration during the last days of gestation on fetal adrenal growth and differentiation were studied. Timed pregnant rats were divided into three groups: (a) 21d DEXA‐3 received DEXA in drinking water (5 μg/ml) from days 18 to 21 of gestation; (b) 21d DEXA‐6 received the same dosage of DEXA from days 15 to 21 of gestation; and (c) 21d control received tap water throughout gestation. On gestation day 21, pregnant rats were decapitated and ble into heparinized tubes; their fetuses were excised, weighed, decapitated, and bled. Fetal adrenals were prepared for electron microscopy or weighed and frozen until assayed for corticosterone. Control adrenals were also collected on day 15 of gestation and processed for electron microscopy only. Fetal adrenals were fixed in 2.5% glutaraldehyde in 0.5 M cacodylate buffer, postfixed in 2% osmium tetroxide (OsO4), dehydrated, and embedded in Epon 812. Twenty‐one day (21d) fetal adrenal weights were 44% and 68% lower than control values for DEXA‐3 and ‐6, respectively. Fetal adrenal corticosterone levels were decreased by 70% and 89% for the respective groups. These observations correlated with ultrastructural findings of decreased mitochondrial number and size, altered orientation of the inner mitochondrial membrane, decreased lipid, and dilation of smooth endoplasmic reticulum (SER) in cortical fascicular cells of DEXA‐exposed fetuses. Ultrastructural changes in the 21d DEXA fetal adrenals resembled 15d day control fetal adrenals. The results suggest suppressed adrenocortical differentiation probably due to DEXA inhibition of the steroidogenic influence of the fetal pituitary on the developing adrenal gland in DEXA‐e

ISSN:0003-276X    

DOI:10.1002/ar.1092050408

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

年代:1983

数据来源: WILEY

摘要:

AbstractWe have used the autoradiographic method to locate trigeminal nerve endings in monkey teeth. The nerve endings were labeled in two adult femaleMacaca fascicularisby 20 hours of axonal transport of radioactive protein (3H‐L‐proline). We found a few labeled axons incontralateralmandibular central incisors and one mandibular canine. Inipsilateralteeth, numerous myelinated and unmyelinated axons were labeled; they formed a few terminal branches in the roots but primarily branched in the crown to form the peripheral plexus of Raschkow and to terminate as free endings in the odontoblast layer, predentin, and as far as 120 μm into dentinal tubules. Electron microscopic autoradiography showed that the radioactive axonally transported protein was confined to sensory axons and endings; odontoblasts and dentin matrix were not significantly labeled. Labeled free nerve endings were closely apposed to odontoblasts in dentin but did not form distinctive junctions with them.Nerve endings were most numerous in the regular tubular dentin of the crown adjacent to the tip of the pulp horn, occurring in at least half of the dentinal tubules there. Reparative dentin was poorly innervated, even near the tip of the crown, and it had a different tubular structure and adjacent pulpal structure from the innervated dentin. Radicular dentin was not innervated in most areas but did contain a few labeled axons where the predentin was wide and the odontoblasts were columnar, as at the buccal and lingual poles of some roots.Our results show that dentinal sensory nerve endings in primate teeth can be profuse, sparse, or absent depending on the location and structure of dentin and its adjacent pulp. When dentin was innervated, the tubules were straight and contained odontoblast processes, the predentin was wide, the odontoblast cell bodies were relatively columnar, and there was an adjacent cell‐free zone and pulpal nerve

ISSN:0003-276X    

DOI:10.1002/ar.1092050409

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

年代:1983

数据来源: WILEY

摘要:

AbstractA detailed, quantitative, three‐dimensional reconstruction of the adult rat lower incisor is presented. The mandibles of 12 male adult rats were dissected and radiographed. The outline of each incisor was traced and the center of the arc formed by the lower, or labial, border of the tooth was geometrically determined. The sector of the bone‐embedded part (mean length 20.70 ± 3.5 mm) of the tooth was divided into six equal segments by radii drawn through the arc center. The dividing radii were transposed onto the specimens and three consecutive 100‐μm transverse ground sections were cut from the incisal side of each segment, parallel to their bordering radii. The distance between each section and posterior wall of the alveolar socket was measured and the information stored in the computer. The outlines of all the dental structures were traced and fed into a computer with the aid of a sonic digitizer. The circumference of the tooth (5.91 ± 0.002), and the mesiolateral and labiolingual widths (1.36 ± 0.001 mm and 2.18 ± 0.01 mm, respectively) remained constant at all tooth levels. The decrease in width and cross‐sectional area of the pulp and the corresponding increase in dentin were represented by the best fitted second order polynomials. These changes were not uniform, being more pronounced in the proximal part of the tooth. The polynomials also served for calculation of the total volumes of pulp, dentin, and enamel (13.93 mm3, 18.05 mm3, and 4.43 mm3, respectively). The three‐dimensinal measurements included the periodontal ligament (PDL), which was significantly wider on the lateral side than on the mesial (0.16 ± 0.006 mm and 0.12 ± 0.004 mm, respectively). The volumes of the enamel‐bordering PDL and of the cementum‐bordering PDL were 7.77 mm3and 8.67 mm3, respectively. In the latter, the tooth‐related compartment constituted 42.7% of the total volume. The data presented can serve as a basis for future quantitative stud

ISSN:0003-276X    

DOI:10.1002/ar.1092050410

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

年代:1983

数据来源: WILEY

摘要:

AbstractSilver methods were successfully applied to semithin sections of Epon‐embedded material, in bronchial epithelium of the chicken lung, as well as in stomach and gut of the frog. Silver methods with some modifications characterize very well the cytoplasmic argyrophilic and argentaffin granules. They give good results in plastic‐embedded mater

ISSN:0003-276X    

DOI:10.1002/ar.1092050411

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

年代:1983

数据来源: WILEY