摘要:

AbstractA three dimensional reconstruction of the epithelial tissue at the apical end of the lower rat incisor was made from serial 1 μm thick cross sections. This tissue formed an elongated structure, called the odontogenic organ, which was composed of a bulbous and a “U”‐shaped part. Both parts were joined to one another at the posterior aspect of the apical foramen. The bulbous part of the odontogenic organ was situated at the lingual side of the “U”‐shaped part and protruded anteriorly over the pulp. It was formed by cells of the outer dental epithelium and stellate reticulum whose organization suggested that the bulbous part was important in the production of cells for renewal of all the epithelia of the incisor. The “U”‐shaped part of the odontogenic organ was apparently derived from the bulbous part and delineated the pulp by forming the lateral, mesial and labial sidewalls around the apical foramen. It was composed of all the epithelial cell types recognizable as precursors to (a) cells of the enamel organ which form the enamel, and (b) Hertwig's epithelial root sheath, a part of the odontogenic organ which induces the formation of dentin on the lingual asp

ISSN:0002-9106    

DOI:10.1002/aja.1001420402

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

年代:1975

数据来源: WILEY

摘要:

AbstractThe epithelial tissue forming the posterior aspect of the apical foramen in the upper incisor of the rat was reconstructed from 1 μm thick serial cross sections. Like the lower incisor, this portion of the odontogenic organ in the upper incisor was composed of a bulbous and a “U”‐shaped part. However, the bulbous part was considerably blunter and the “U”‐shaped part much larger in circumference in comparison to the lower incisor. Although no differences were found between the upper and lower incisor regarding the contents and the basic organization of cells within each part of the odontogenic organ, specific differences were found within the bulbous part in the upper incisor. There was a more definitive boundary between the outer dental epithelium and stellate reticulum, a more intimate relationship of cell streams to the stellate reticulum, and a noticeable lack of swirling of cells as part of the streams. These features suggest that the activity inside the bulbous part is less intense in the upper incisor than it is in the lower incisor. In addition, the relationships between the bulbous part, the “U”‐shaped part and the root sheath part of the odontogenic organ and the enamel organ were described for

ISSN:0002-9106    

DOI:10.1002/aja.1001420403

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

年代:1975

数据来源: WILEY

摘要:

AbstractA single dose of 0.5 mCi radioiron (55Fe) was injected directly into the amniotic cavity of each of four pregnant monkeys near term. At 6 or 24 hours after55Fe administration, samples of fetal jejunum, ileum, blood, spleen, liver, lung and fetal membranes were taken for radioautography and scintillation counts. Counts were also made on corresponding maternal tissues.Intestinal radioiron levels and localization indicated that fetuses swallowed and absorbed55Fe within 6 to 24 hours after injection. Silver grains over the meconium bodies of fetal ileum suggested that intestinal epithelium retained at least some of the absorbed radioiron. However, elevated55Fe levels in fetal blood and hematopoietic organs indicated that transport of radioiron to the circulation had occurred, presumably through fetal intestine, extraembryonic membranes and/or fetal lungs. Transfer of55Fe across the placenta from fetus to mother occurred at a slow rate, i.e., samples of maternal organs obtained at 24 hours gave low counts.

ISSN:0002-9106    

DOI:10.1002/aja.1001420404

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

年代:1975

数据来源: WILEY

摘要:

AbstractA small number of epithelial cells which combine features of two cell types were observed in the descending colon and pyloric stomach of the mouse.In thedescending colon, where the base of the crypts is mainly composed of poorly differentiated “vacuolated” cells, a few of these cells contain, besides the characteristic “vacuoles,” mucous globules identical to those in mucous cells or, less frequently, dense granules such as are found in entero‐endocrine cells. Because there is evidence that the poorly differentiated vacuolated cells give rise to the other cells of the epithelium, those which also contain mucous globules or dense granules are likely to be differentiating into mucous cells or enteroendocrine cells respectively.In thepyloric stomach, where the glands are mainly composed of mucous cells, some of which are poorly differentiated, a few of the latter exhibit, besides the mucous globules, entero‐endocrine type granules or features of caveolated cells. It is likely that the poorly differentiated mucous cells give rise to the other gland cells; and, therefore, those mucus‐containing cells which also display dense granules or caveolated cell features are taken to be differentiating into entero‐endocrine or caveolated cells respectively.Most of the cells containing two kinds of secretory materials are believed to be stem cells which initially contain a few vacuoles (colon) or mucous globules (pylorus) but are differentiating into a cell containing a different type of secretion. Rare observations of two kinds of secretory materials in a mature cell suggest that the transitional period may be prolonged, perha

ISSN:0002-9106    

DOI:10.1002/aja.1001420405

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

年代:1975

数据来源: WILEY

摘要:

AbstractVirus‐like particles (80 mμ to 100 mμ in diameter) occur in the endoplasmic reticulum of germ cells in the ovaries of fetal guinea pigs, and are confined to this population of cells. Using these particles as a marker, the phagocytosis of degenerating germ cells by somatic cells in the cortex of the ovary was tra

ISSN:0002-9106    

DOI:10.1002/aja.1001420406

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

年代:1975

数据来源: WILEY

摘要:

AbstractIt has been suggested that PGCs are attracted to developing gonads by a chemotactic‐like agent secreted by the gonads and that this agent might be steroidal in nature. This study was undertaken to ascertain whether specific exogenous steroid hormones exert an influence on germ cell colonization of the gonads, by enhancing, inhibiting or otherwise interfering with it. Testosterone cypionate in cottonseed oil, crystalline testosterone propionate, estrone in aqueous suspension and crystalline estradiol‐17β were administered to chick embryos at 33 hours incubation. Normally developed embryos, those receiving cottonseed oil (vehicle for testosterone cypionate) and those receiving cholesterol served as controls. A decrease in the number of germ cells in the gonadal area at five days of incubation occurred in all groups receiving the androgens and estrogens. However, in only one group (that receiving testosterone cypionate) was this decrease found to be significant. The mean number of germ cells found in the cottonseed oil controls and the cholesterol controls closely paralleled that of the normally developed controls. Normal asymmetry in the distribution of the germ cells favoring the left side in the chick was not affected in any of the groups; however, the percentage distribution of the germ cells between the right and left gonads at this early stage appeared to be affe

ISSN:0002-9106    

DOI:10.1002/aja.1001420407

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

年代:1975

数据来源: WILEY

摘要:

AbstractA radioimmunoassay for glucagon was utilized to investigate early developmental aspects of glucagon synthesis and release in the chick embryo. Immunoreactive glucagon was detected in both the pancreas and blood plasma from the fifth embryonic day onwards. The present data show that the chick embryonic alpha cell has the potential for secretory activity very early in development, and suggest a developmental role for glucagon in hepatic glycogen metabolism.

ISSN:0002-9106    

DOI:10.1002/aja.1001420408

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

年代:1975

数据来源: WILEY

摘要:

AbstractAntiserum to chick skeletal muscle tropomyosin was used to localize tropomyosin in mouse embryo fibroblasts by the indirect fluorescein labeled antibody technique. Specific staining was observed in cytoplasmic fibers, which extended out into the cell processes. The staining pattern in these cells is similar to that previously described by others for actin. This observation suggests that in fibroblasts tropomyosin, like actin, is localized in fibers in the cytoplasm.

ISSN:0002-9106    

DOI:10.1002/aja.1001420409

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

年代:1975

数据来源: WILEY

摘要:

AbstractFresh pullet eggs (White Leghorn Strain) were incubated from 6–19 hours. Blastoderms were fixed in situ with aldehyde fixative, post‐osmicated in 2% OsO4, dehydrated in acetone, criticalpoint‐dried, mounted ventral side up, coated with palladium‐gold wire and observed in a Cambridge Stereoscan S4 scanning electron microscope.Large extracellular yolk granules had a smooth surface and appeared to break up into smaller particles. Similar particles have been observed intracellularly in transmission electron microscopy. Numerous microappendages, mostly ruffles, suggest phagocytosis as a method of absorption of yolk granules into the cells. Absorption of yolk by the cells of the blastoderm involves an initial break up of yolk granules followed by phago

ISSN:0002-9106    

DOI:10.1002/aja.1001420410

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

年代:1975

数据来源: WILEY

摘要:

AbstractElectron microscopic studies have revealed that cyclic AMP, like ACTH, induces structural differentiation of adult human adrenocortical cells cultured in vitro. These findings support the hypothesis that cyclic AMP can function as an intracellular mediator of the action of ACTH on the human adrenal gland.

ISSN:0002-9106    

DOI:10.1002/aja.1001420411

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

年代:1975

数据来源: WILEY