摘要:

AbstractOvaries from 16‐day mouse fetuses were cultured as whole organs in a modified Eagle's medium for two through 45 days. In the course of the experiment a single layer of follicular cells resting on a basement membrane surrounded the majority of the surviving oocytes, resulting in unilaminar follicles. A small number lay in multilaminar follicles having two to three layers of follicular cells. No follicles with antra were seen regardless of the length of time in culture. Initiation of zona pellucida formation occurred after three days in culture. In general, the thickness of the zona pellucida was not as great as that around an oocyte of similar sizein vivo.Some of the large oocytes attained diameters of 68–73 μ, which is within the normal range for fully grown mouse oocytesin vivo.Only one oocyte in all the cultures examined had a first meiotic metaphase spindle. In many follicles the initial step in degeneration was the migration of macrophages into the follicular epithelium and their attachment to the zona pellucida. The follicular epithelium often was completely replaced by an enclosing layer of macrophages; the oocyte in some such instances still appeared normal. Subsequently, the germinal vesicle became pycnotic and the ooplasm, PAS‐positive. At the end of the degenerative process the zona pellucida appeared as an empty shell with macrophages attached to both its external and internal su

ISSN:0002-9106    

DOI:10.1002/aja.1001310402

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

年代:1971

数据来源: WILEY

摘要:

AbstractIn fetal testes of non‐inbred guinea pigs, virus‐like particles were seen in the primordial germ cells, but not in the somatic cells. Using the particles as a marker for the gonocytes it was possible to trace the phagocytosis of degenerating gonocytes by the Sertoli cells in the fetal tes

ISSN:0002-9106    

DOI:10.1002/aja.1001310403

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

年代:1971

数据来源: WILEY

摘要:

AbstractScanning electron micrographs demonstrate the presence of an indifferent fiber plexus as an integral part of periodontia in the rat, dog, armadillo and man. Individual fibers measure 1400 Å in diameter in scanning electron micrographs. The indifferent fibers course in every direction throughout the area between bone and cementum without particular orientation. They anastomose extensively with the principal fibers to form a continuous fibrous matrix. Anastomoses with principal fibers begin adjacent to bone or cementum and increase until the indifferent fiber plexus reaches maximum density a short distance from the mineralized matrix. At this point a principal fiber may lose its structural identity as it blends with the profusion of indifferent fibers. This phenomenon occurs in all species studied but is more evident in the relatively unstressed teeth of armadillos. In the dog, principal fibers may extend from cementum to bone as highly compact structures. Anastomoses between principal and indifferent fibers often occur via fibers of intermediate size. The latter fibers become more oriented as their fiber diameters increase. Gingival fibers of the rat, in contrast to principal fibers of the alveolodental ligament, rarely consist of compact fiber bundles. Instead, fibers of indifferent and intermediate size aggregate to form gingival cords in which component fibers are readily distinguishable

ISSN:0002-9106    

DOI:10.1002/aja.1001310404

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

年代:1971

数据来源: WILEY

摘要:

AbstractThe epithelium covering the surface of the tongue of the South American toadCalyptocephalella gayihas been analyzed using large electron microscope photo‐montages and has been compared with that covering the tongue of the frog,Rana pipiens. In both species four kinds of epithelia are similarly distributed over the surface, and relatively minor differences in the cytoplasm and intercellular relations have been identified. Stratified ciliated epithelium covers the ventral, nonpapillary surface. A simple columnar epithelium of mucous cells covers most of the irregular dorsal surface. A poorly stratified nonkeratinizing epithelium covers the apex of filiform papillae while stratified, columnar epithelium forms the thick epithelial disc of fungiform papillae. Emphasis is given to fungiform papillae as the basis for functional studies since they are the only structures receiving large numbers of nerve fibers. Sensory terminals do not appear to be acted on directly by chemicals since they are located near the base of the epithelium and since tight junctions unite cells at the outer surface. However, axons selectively contact the base of certain elongate cells which extend to the surface and are presumed to be receptor cells. It seems probable that recent intracellular potential changes, recorded from the toad tongue in response to chemical stimulation, originate from mucous cells. It is suggested that these potentials could affect the receptor cells if low resistance pathways are provided by tight junction

ISSN:0002-9106    

DOI:10.1002/aja.1001310405

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

年代:1971

数据来源: WILEY

摘要:

AbstractThe development of the structural pattern of the lower sacral and coccygeal segments of the spinal cord in human, rabbit and monkey embryos and fetuses has been studied. The changes observed in serial sections from above downward are outlined, beginning with typical sections through the lower sacral cord. Among the changes, other than diminution in size of the spinal cord and reduction in size of the lower spinal nerves, there is a gradual disappearance of the posterior funiculus. As this occurs the gray matter appears to spread dorsally and the central canal widens. The gray matter becomes reduced in size and the lateral funiculus extends farther dorsally. A little lower down, the gray matter of the alar plate is reduced further in size and there is corresponding enlargement of the central canal. This enlargement constitutes the terminal ventricle. The spinal cord rapidly becomes smaller as both the fibers and the gray matter are diminished. In some specimens, fibers decussate dorsal to the lower end of the terminal ventricle. Little remains of the lower end of the spinal cord except the ependymal wall of the central canal and the surrounding fiber bundles. The shape and size of the lower end of the central canal is subject to variations.In the lower part of the spinal cord a longitudinal bundle on each side is formed by fiber contributions from the anterior horn cells in the basal plates. This bundle contributes fibers to the fifth sacral and the first and second coccygeal nerves. It is designated the sacrococcygeal fasciculus.

ISSN:0002-9106    

DOI:10.1002/aja.1001310406

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

年代:1971

数据来源: WILEY

摘要:

AbstractSamples of dorsal skin were obtained from 18‐, 19‐ and 20‐day rat fetuses. Comparative developmental studies were carried out from a portion of the samples, while the remaining samples were cultured for four days in a medium containing tritiated thymidine and studied autoradiographically.At 18 days the epidermis contained a periderm, a stratum intermedium and a stratum basale. By 19 days the strata granulosum and spinosum had developed. At 20 days, a stratum corneum was present. Cultured samples of 18‐day fetal rat skin resembled those that developedin uterowith respect to time, whereas, the samples of 19‐ and 20‐day fetal rat skin developed a more extensive stratum corneum, fewer keratohyalin granules, and a more condensed stratum Malpighii.Autoradiographic studies were made to determine the time taken for cells to migrate from the stratum basale to the outermost layer of the stratum granulosum (transit time). A similar “transit time” was noted for the three fetal ages studied. The rates of cell migration varied. The results of this study suggest that the extent of cornification impedes cell migration by providing a physical resistance or barrier against the outward forces presumably exerted by the division

ISSN:0002-9106    

DOI:10.1002/aja.1001310407

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

年代:1971

数据来源: WILEY

摘要:

AbstractMorphological aspects of lipid absorption were compared in the jejunum, mid‐ and terminal ileum. Physiological fatty chyme was injected into ligated segments of each of the intestinal regions in fasting rats. Tissues were removed at intervals from 5 to 30 minutes and prepared for electron microscopy. The results show the morphological pattern of lipid accumulation to be similar in the jejunum and mid‐ileum. Both show evidence for considerable lipid absorption and transport. The terminal ileum, in contrast, displays an altered pattern of lipid distribution. Numerous lipid droplets begin to form at an early time period in the cytoplasmic matrix, as in the upper intestine. These droplets become larger and more numerous as absorption progresses. Lipid droplets in the endoplasmic reticulum and Golgi apparatus, however, are present in considerably reduced size and numbers through the entire absorptive period examined, as compared to the upper intestine. Few droplets are present in the lamina propria. Considerably less transport of absorbed lipid is indicated. This morphological pattern appears to correlate with a reduced synthesis of triglycerides in the terminal ileum. The evidence suggests that triglyceride synthesis and the formation of membrane‐bound droplets are related events as they normally occur in the upper small inte

ISSN:0002-9106    

DOI:10.1002/aja.1001310408

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

年代:1971

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001310401

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

年代:1971

数据来源: WILEY