摘要:

AbstractPenetration of macromolecules into living peripheral nerve was studiedin vivoandin vitrousing horse‐radish peroxidase. Peroxidase penetrates the epi‐ and perineurium and is sequestered in the Schwann cell body. It then is apparent in the incisures (clefts) of Schmidt‐Lanterman and the paranodal loops. After prolonged incubation the marker appears in the adaxonal Schwann cytoplasm and periaxonal space. It then is visualized inside the axon within vesicles and agranular endoplasmic reticulum both at the node and internodal regions. More rapid penetration occurs at the node of Ranvier than at the internodal r

ISSN:0002-9106    

DOI:10.1002/aja.1001360102

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

年代:1973

数据来源: WILEY

摘要:

AbstractIn unit lengths of longitudinally cut histological sections of the rat small intestine, the number of diazo‐positive argentaffin cells was determined along with the number of other epithelial cells. From these results, the frequency of argentaffin cells among the epithelial cells was calculated. The number, as well as the frequency, was maximal in the proximal duodenum and progressively decreased to a minimum in the mid‐intestine. Thereafter, it increased progressively caudally to reach a second maximum in the terminal ileum. The frequency in the terminal ileum was almost as high as in the proximal duodenum. When calculated for the duodenum of various age groups, it decreased from eight to two argentaffin cells per 1000 epithelial cells from newborn to adult ages respectively. It was calculated furthermore that the total number of diazo‐positive argentaffin cells in the rat small intestine should be around six million. Considering that the argentaffin cells are renewed about every four days (Ferreira and Leblond, ′71), about 1.5 million of them should be formed as well as exfoliated daily.The cells in the villi were stained more intensely than in the crypts, indicating that the argentaffin cells accumulate granules as they migrate from the crypts toward the villus tips, where indeed, intensely stained exfoliating argentaffin cells were occasionally observed. It is suggested that the exfoliation of argentaffin cells full of granules may be a mode of secretion for 5‐hydroxytryptamine into the intesti

ISSN:0002-9106    

DOI:10.1002/aja.1001360103

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

年代:1973

数据来源: WILEY

摘要:

AbstractTesticular differentiation, as evidenced by the appearance of a distinct tunica albuginea and formation of plate‐like aggregates of germ cells and mesenchymal cells, occurs at 16 days in the rabbit fetus. The germ cells at this stage of development are isolated large, round to oval cells that are easily distinguished from the smaller elongated mesenchymal elements surrounding them. The germ cell nuclei have a smooth spherical contour and a prominent eccentric nucleolus. Cytoplasmic organelles are sparse, consisting of scattered polyribosomes and spherical or ovoid mitochondria distributed singly in the cell. At 18 days, the cell groups form into distinct cords of germ cells and supporting cells, the earliest stage of seminiferous tubule formation. Between 22 and 25 days, proliferating germ cells show increasing condensation of nuclear chromatin and increased nucleolar complexity. The cytoplasm contains groups of mitochondria, dense polyribosomal complexes, lipid aggregates, scattered smooth vesicles and prominent Golgi complexes. Intercellular bridges appear between germ cells on day 22 and increase in number on succeeding days. During the last week of fetal development, germ cells become aligned in rows at the periphery of the primitive tubules. Their arrangement at this time resembles that of spermatogonia in the adult testis. However, the fetal “prespermatogonia” lack some of the characteristic ultrastructural features of adult spermato

ISSN:0002-9106    

DOI:10.1002/aja.1001360104

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

年代:1973

数据来源: WILEY

摘要:

AbstractAtrioventricular nodal tissue obtained from a two‐week‐old mouse heart was fixed in osmium tetroxide, embedded in Epon 812, and serially sectioned for electron microscopy. From the study of electron micrographic montages of the first 620 serial sections of the posterior‐inferior (tail) portion of the node, it was determined that many of the nodal cells are spindle‐shaped and each has a single, centrally‐placed, ellipsoidal nucleus. Other cells exhibit irregular surfaces with protrusions of variable dimensions and some are flattened. Most of the flattened cells are located in the peripheral borders of the posterior and lateral portions; irregularly‐shaped cells occupy deeper positions in the tail of the node. Two cells, which are different from all others, reside in the peripheral border of the medial portion. They are contiguous with one another and globular in shape, each containing a single, centrally‐placed, spherical nucleus. These two cells are sparsely endowed with myofilaments but contain many mitochondria. They may be pacemaker cells. Intercellular relationships among nodal cells exhibit a wide variety of complicated contact areas in addition to some rather simple contiguities of the lateral aspects of adjacent cells. No typical intercalated discs are present; however, junctional specializations between interdigitating protrusions of contiguous nodal cells do occur. Intimate contact between vesiculated nerve processes and nodal cells varies in extent from a profuse innervation in the posterior and lateral portions of the tail of the node to lack of contact with many of the cells in the medial and anterior portions. This pattern of innervation, in conjunction with the absence of maculae occludentes between cells of the posterior and lateral portions of the tail of the node but present between cells of the other portions, suggests that the medial and anterior areas are conductive and the posterior and lateral areas a

ISSN:0002-9106    

DOI:10.1002/aja.1001360105

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

年代:1973

数据来源: WILEY

摘要:

AbstractGross anatomic and radiologic studies of the blood supply to the human mandible of the full‐term fetus and newborn infant were performed on 22 specimens ranging from 320–538 mm crown‐heel length and 1,192–4,108 gm in weight. Ten specimens were injected with red‐lead and liquid soap to demonstrate the arteries radiographically. Twelve other specimens were injected with Castolite with a sprinkling of red‐lead and yellow dye. The best side of each specimen was studied by radiography and dissection. This study demonstrated: (1) a masseteric arterial plexus supplying the coronoid process and the lateral wall of the ramus with contributions from the facial, masseter, transverse facial and external carotid arteries or combinations thereof; (2) a mental arterial plexus anastomosing with the mental, submental and inferior labial arteries; (3) an inferior alveolar artery supplying most of the body of the mandible with a majority of its branches passing in an upward direction; and (4) periosteal vessels supplying the lower border of the mandible and receiving their blood supply from the blood vessels supplying the muscles attaching to these areas and the periosteum. Supplemental to the above findings were anastomoses between the submental, mylohyoid and sublingual arteries along the medial border of the mandible. Also a significant variation not previously recorded was noted in one specimen in which the sublingual artery originated from the facial artery rather than

ISSN:0002-9106    

DOI:10.1002/aja.1001360106

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

年代:1973

数据来源: WILEY

摘要:

AbstractChick embryos of the White Leghorn strain were incubated from one‐half to four days and sacrificed by immersionin toto. in Karnovsky's fixative. The cervical region of each embryo was excised and prepared for electron microscopy. Intercellular materials, which appear indistinguishable from the early connective tissue components of the embryonic tissue space, appear within dilated interstices of the notochordal epithelium beginning at approximately Hamburger‐Hamilton stage 14. At progressively older stages this intercellular material appears to organize and aggregate to form fibrils. By stage 22 widely expanded intercellular spaces contain boundary (basement) membrane material, amorphous substance and microfibrils of various sizes. Moreover, larger, more mature fibrils that exhibit collagen‐like periodic striations are present. The existence of connective tissue materials in cellular interstices deep within the central portion of the notochord strongly suggests that these substances are derived from notochordal epithelial cells. Furthermore, the similarity of the intercellular connective tissue components to those deposited on the notochordal surface suggests that these latter materials are likewise a secretory product of the notochord. The significance of the perinotochordal connective tissue (notochord sheath) with respect to the recent emphasis on the role of surface‐associated substances to cytodifferentiation is di

ISSN:0002-9106    

DOI:10.1002/aja.1001360107

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

年代:1973

数据来源: WILEY

摘要:

AbstractDirect observations of ciliary activity on the mucosal surface of mammalian oviducts have rarely been reported. Yet such studies might help to determine the relative value of ciliary action in gamete transport through the ducts. The purpose of this study was to examine the direction and rapidity of ciliary currents in the oviducts of two mammalian species, the rabbit and the pig. Fresh oviducts were slit open longitudinally and submerged in Hanks' balanced salt solution at 37°C. The movements of particulate matter, such as stained lycopodium spores and 15 μ microspherents, placed on the mucosal surface, were observed and recorded on film. In both species ciliary currents in the ampulla swept the particles toward the ampullar‐isthmic junction. In the isthmus of the pig oviduct the particulate matter was transported in the reverse direction, toward the ovary. The pro‐ovarian current could be demonstrated throughout the isthmus, beginning a few millimeters above the uterotubal junction. In the rabbit a similar current was detected, but it was not as extensive as in the pig. In the upper isthmus of the rabbit oviduct, particulate matter and rabbit eggs in the “mucin coat” merely rotated or “tumbled” on the surface with little movement in either direction. This is the first report of pro‐ovarian ciliary currents for any mammal, and we believe these to be important for sperm transport through the isthmus. The action of cilia during egg transpo

ISSN:0002-9106    

DOI:10.1002/aja.1001360108

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

年代:1973

数据来源: WILEY

摘要:

AbstractLight and electron microscopic studies have been made on young oocytes of the trout; i.e., during previtelline and early stages of vitellogenesis. Balbiani's basophilic body has been followed from its origin in the youngest oocyte to its disappearance at the beginning of vitellogenesis. It assumes the form of a duplex body composed of a non‐basophilic component (idiosome) and a highly basophilic portion, the pallial substance. Electron micrographs reveal the Balbiani body to be a dense, finely granular substance apparently unrelated to the Golgi apparatus or mitochondria. Its role in oogenesis is not clear, but probably constitutes an essential precursor substance (perhaps RNA) necessary for oocyte growth and vitellogenesis.At given periods in early oocyte growth, an extensively developed system of endoplasmic reticulum is formed and the cisternae contain numerous granules. These intracisternal granules probably represent precursor elements for a specialized type of yolk substance. The granules collect in dilated regions of the smooth‐surfaced cisternae where the latter undergo anastomosis. Here the granules undergo transformation into a finely granular particle. Older and more vitellogenetic oocytes have not been included in this st

ISSN:0002-9106    

DOI:10.1002/aja.1001360109

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

年代:1973

数据来源: WILEY

摘要:

AbstractCross sections of aldehyde‐perfused, Epon‐embedded cat and dog spinal cord examined with an electron microscope display numerous synaptic vesicles with electron‐opaque cores along the medial and lateral margins of the dorsal gray matter (laminae I, II, III). The cored vesicles, 750 – 1500 A in diameter are located in synaptic sacs and in small unmyelinated axons. They occur in small numbers throughout the apical gray matter but are much more numerous in a narrow band immediately adjacent to the white matter. Their numbers and location should be of value in studies on the nature and origin of this type of synaptic

ISSN:0002-9106    

DOI:10.1002/aja.1001360110

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

年代:1973

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001360101

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

年代:1973

数据来源: WILEY