摘要:

AbstractThe fine structure of the capillaries of the pineal glands of the rat, mouse, chinchilla and ground squirrel were investigated. The pineal endothelial cells in the rat, mouse and ground squirrel were often composed of attenuated cytoplasmic portions which contained numerous fenestrations, in contrast to pineal capillaries in the chinchilla which were lined by thick non‐fenestrated endothelial cells. Marked morphological differences were also apparent in terms of the types of vesicles within the cytoplasm and abutting on the cell surface of pineal endothelial cells from the various specius investigated. The interendo‐thelial junctions exhibited remarkable species differences with the chinchilla pineal possessing typical tight endothelial junctions while those in the rat, mouse and ground squirrel lacked such endothelial cell associations. Generally, capillary lining cells in the chinchilla pineal resembled similar cells within the brain, while endothelial cells in pineal glands of rat, mouse and ground squirrel were more typical of those found in other endocrine organs. Species differences in the structure of the pineal capillaries may represent physiological differences as w

ISSN:0002-9106    

DOI:10.1002/aja.1001430302

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe morphogenesis of filiform papillae on rat tongue was investigated with the electron microscope. Tongue rudiments were first seen on the 12th day of gestation. At 15–17 days, dermal papillae had formed and were arranged in hexagonal array on the dorsal lingual surface. Capping each dermal papilla was a two‐layered epithelium that protruded slightly above the lingual surface, thus forming the early filiform papilla. In the next stage of development, at 18–19 days of gestation, the epithelium lining the papilla had differentiated into two cell populations, one producing hard keratin, the other producing soft keratin. Some of the keratinized epithelial cells assumed a position at an acute angle to the tongue surface and extended deep into the epithelium. In the next stage, 20–21 days, a cleft appeared within these angularly oriented cells. This resulted in the division of the epithelium into keratin‐lined individual filiform papillae. Finally, the individual papillae increased in size to the a

ISSN:0002-9106    

DOI:10.1002/aja.1001430303

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe development of the synovial sheathed flexor digital tendon in the chick was studied by light and electron microscopy in 12‐day embryos to 22‐day post‐hatched chickens. Areas of specialized connective tissue differentiation were identified in this complex structure consisting of a lubricated synovial sheath, elastic vincula and fibrocartilaginous adaptations on the surface of the tendon. The presence of some of these specialized adaptations may be related to tendon. The presence of some of these specialized adaptions may be related to the specific types of mechanical forces and stresses applied to the developing connective tissue system. This model system appears to be appropriate for the experimental study of tendon injuries related to thehuman

ISSN:0002-9106    

DOI:10.1002/aja.1001430304

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

年代:1975

数据来源: WILEY

摘要:

AbstractMorphogenesis of the labyrinthine part of the chorioallantoic placenta of the golden hamster between day 10 of gestation and term (day 16) was studied by light and electron microscopy. During this period the labyrinth increases greatly in both size and complexity. Trabeculae of the labyrinth, thin partitions composed of trophoblastic tissue and fetal capillaries which delimit the maternal blood spaces, apparently proliferate both by appositional and interstitial growth. From the time of its formation (day 9 of gestation) until term the labyrinth is hemotrichorial in organization (i.e. three layers of trophoblast separate maternal blood from fetal capillaries). Both the inner and intermediate layers of trophoblast (layers III and II, respectively) are syncytial. The outer trophoblastic layer (III), which is in direct contact with maternal blood, remains cellular, although many of its component cells grow to giant cell dimensions (“labyrinthine giant cells”). Between the tenth and fourteenth days of gestation the anatomical barrier to diffusion between maternal and fetal blood is progressively reduced. This is accomplished both by gradual attenuation of the trophoblastic layers and fetal capillary endothelium and by the formation of discontinuities (gaps) in layer I, and diaphragmed fenestrae in fetal capillary endothelium. The labyrinthine placental barrier is fully developed and probably attains maximal functional efficiency by the fourteenth day of gestation. Late in the fifteenth day of gestation, a few hours before parturition, distinct degenerative changes are apparent in the trophoblastic layers and fetal capillaries of the trabeculae. The factors responsible for initiating these degenerative changes and the onset of parturition are still controvers

ISSN:0002-9106    

DOI:10.1002/aja.1001430305

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

年代:1975

数据来源: WILEY

摘要:

AbstractFetal decapitationin uterohas enabled us to study the role of fetal pituitary hormones in the development of the fetal testis. Testes from males decapitated near 80 days of gestational life and later delivered at 150 days were smaller than normal and about one‐tenth the normal weight. The size of the seminiferous tubules was similar in both groups; however, the number of Leydig cells seemed reduced. In addition, the Leydig cells of the experimental group contained smaller mitochondria with reduced tubular cristae, fewer lipid droplets, and reduced agranular endoplasmic reticulum. Androgen production was inhibited. Measured by radioimmunoassay, the testosterone level in the umbilical vein was 329 ± 82 pg/ml in six decapitated fetuses, 412 ± 62 pg/ml in ten normal fetuses. The level in the umbilical artery was 328 ± 56 pg/ml in five decapitated fetuses, 658 ± 140 pg/ml in normal fetuses. These studies suggest that chronic deprivation of fetal pituitary hormones inhibits the growth and development of the testis in general and of the Leydig cells in parti

ISSN:0002-9106    

DOI:10.1002/aja.1001430306

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

年代:1975

数据来源: WILEY

摘要:

AbstractYoung adult rats were injected with parathyroid extract (PTE). Periodontal ligament (PDL) adjacent to a previously resorbing alveolar bone surface was divided into four zones numbered I to IV, from bone to cementum. Zones I and IV were within 25 mμ of the bone and cementum surfaces, respectively, while a line bisecting the center of the PDL separated Zones II and III. A net increase of about 16 total nuclei in all zones was observed during the first five hours after PTE administration. Since local mitosis accounted for no more than two nuclei, approximately 14 cells apparently migrated into the area. Over the first five hours Zones I and II combined showed a 21‐cell increase, being apparently the scle recipients of cells migrating into the field (14) plus approximately seven more from Zone III, which lost cells during the time period. The concurrent histological observation in Zone II, of increased intravascular monocytes and perivascular macrophages during the first five hours, suggests cells are migrating into Zone II via vascular channels. The data suggest two sources for increased PDL cellularity associated with stimulated osteoclast histogenesis: (1) local PDL cellular proliferation and (2) influx of migrating cells (probably through vascular channels) during first five hours after P

ISSN:0002-9106    

DOI:10.1002/aja.1001430307

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

年代:1975

数据来源: WILEY

摘要:

AbstractMouse photoreceptor cells exhibit local accumulations of osmium deposits after prolonged osmic staining at slightly elevated temperatures. Deposits were evident along the membranes of outer segment lamellae, Golgi cisternae and vesicles, nuclear envelopes, and synaptic vesicles. Other membranes within the photoreceptor cells were unreactive. No osmium reactivity was seen in other cells of the retina except for osmiophilic outer segment material which had been phagocytized by the pigment epithelium. In the outer segments, inner segments, and synaptic regions of the photoreceptor cells, the amount of osmium reactivity was increased by light stimulation and decreased following extended dark adaptation. The possible significance of the localized osmium reactivity is discussed.

ISSN:0002-9106    

DOI:10.1002/aja.1001430308

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe absence of the cranial three‐fifths of the vaginae of male mice carrying the gene, Testicular Feminization, provides strong support for the view that vaginal epithelium is of dual origin, the cranial three‐fifths being of Mullerian in origin and the caudal two‐fifths being derived from the urogenital

ISSN:0002-9106    

DOI:10.1002/aja.1001430309

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

年代:1975

数据来源: WILEY

摘要:

AbstractWhen the dorsal surface of the young chick embryo is examined by SEM, long threads are visible, each of which appears to connect pairs of cells; these cells may be separated from each other by several intervening cells. Many of the threads possess a bead‐like structure about half way along their length. When sections of the beads are examined by TEM they are found to resemble midbodies. Furthermore, the threads possess longitudinally arranged structures within them, which are probably the remnants of the microtubules which were part of a mitotic spindle. It is concluded that each bead is a midbody and that each beaded thread is the remains of a telophase bridge connecting two daughter cells which were incompletely separated after mitosis had taken place. The possible function of the beaded threads is considere

ISSN:0002-9106    

DOI:10.1002/aja.1001430310

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

年代:1975

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001430301

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

年代:1975

数据来源: WILEY