ISSN:0002-9106    

DOI:10.1002/aja.1001580102

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

年代:1980

数据来源: WILEY

摘要:

AbstractSerum prolactin (PRL) levels display regular patterns throughout the 4‐day rat estrous cycle. A morphometric analysis of mammotropes (PRL‐secreting cells) in the anterior pituitary was performed in an effort to quantify some of the ultrastructural events occurring prior to and during the secretion of PRL throughout the estrous cycle. In this study, a systematic sampling protocol applicable to the rat adenohypophysis was developed, which took into account the lack of synchrony in estrous cycles among the animals, the heterogeneity of the gland, and the number of cells required to yield a representative sample. These techniques were used to determine the cell, nuclear, nucleolar, and cytosol volumes, which were correlated with the changing levels of serum estradiol and PRL and pituitary PRL.Estradiol concentrations rose during late diestrus‐1 and continued rising in a pulsatile manner, reaching maximal levels during proestrus. The elevations of estrogen were accompanied by increases in nucleolar and nuclear volumes. However, at early estrus and on the afternoon of diestrus‐2, times at which it has been reported that progesterone levels are elevated, there was a dampening effect and these volumes declined. During early diestrus‐2, when estradiol levels began to rise, there were increases in nucleolar, nuclear, cellular and cytosol volumes, as well as increases in pituitary PRL; but at late diestrus‐2 there was a marked increase in nuclear and nucleolar volumes which was not accompanied by increases in cellular and cytosol volumes. During proestrus, two peaks of serum PRL were found, at 6 pm and 12 m, which were concomitant with increased nucleolar, nuclear and cellular volumes. The 6‐pm proestrous peak of PRL was preceded by elevated pituitary PRL; however, the 12‐m proestrous peak occurred when the pituitary PRL was minimal, even though nuclear and cellular volumes were elevated. This suggests that the 6‐pm release of PRL was derived from previously synthesized and stored hormone, while the 12‐m peak was the result of the immediate release of PRL,

ISSN:0002-9106    

DOI:10.1002/aja.1001580103

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe organellar dynamics within mammotropes (prolactin secreting cells) of the anterior pituitary were examined using morphometry throughout the four‐day rat estrous cycle. Two predominant periods of maximal organellar activity were found. The first period, which occurred during proestrus, resulted in two peaks of serum PRL at 6 pm and 12 m proestrus, while the second occurred during middiestrus‐2 and resulted in an increase of pituitary PRL, but not a major serum PRL peak. The mitochondrial volume rose prior to that of other organelles during early proestrus, rising 110% from 4 am late diestrus‐2 to 6 pm proestrus. However, the number of mitochondria per cell remained constant throughout the cycle. The volumes of rough endoplasmic reticulum (RER) and Golgi complex reached maximal proportions at 8 pm and 12 m proestrus, respectively. The RER volume was 153% greater than at 4 am late diestrus‐2, while the Golgi complex had increased by 200%. We suggest that changes in the RER and Golgi complex volumes were the result of two processes: the synthesis of new membrane and the swelling of existing complexes. This study further substantiated that the serum peak of PRL at 6 pm proestrus is the result of stored mature granules being released, whereas the PRL peak at 12 m proestrus is due to the immediate release of hormone without any

ISSN:0002-9106    

DOI:10.1002/aja.1001580104

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe types of intercellular junctions present within caudal levels of the chick neural tube (i.e., future lower thoracic and lumbosacral regions of the spinal cord) were determined by freeze‐fracture of stage 14 to 16 embryos. Two levels of the developing neural tube were examined: the region of the neurulation overlap zone–consisting of primary neural tube dorsally and secondary neural tube ventrally–and the portion of the primary neural tube located just cranial to the overlapping region. Gap junctions were the most numerous type of intercellular junction present within the primary neural tube. These junctions were located primarily in juxtaluminal areas, near the apices of neuroepithelial cells, and sometimes also at the bases of these same cells. In addition, focal, poorly defined tight junctions occasionally occupied juxtaluminal regions of the primary neural tube. The medullary cord (i.e., the immediate precursor of the secondary neural tube) and secondary neural tube contained gap junctions exclusively. Gap junctions were first found in these areas at the lateral borders of the medullary cord, concomitant with formation of this structure, and then at the interface between the elongated, peripheral cells of the cord and the irregularly shaped and loosely arranged central cells of this structure. Finally, gap junctions were distributed radially around secondary lumina formed by cavitation. The precise spatial and temporal correlation between the appearance of gap junctions and the specific changes occurring in cellular morphology and arrangement during secondary neurulation strongly suggest that gap junctions may have a role in coordinating cellular activities during formation of both the medullary cord and the secondary neural

ISSN:0002-9106    

DOI:10.1002/aja.1001580105

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

年代:1980

数据来源: WILEY

摘要:

AbstractFormation of the future lumbosacral level of the spinal cord was studied in two‐day‐old chick embryos by light and electron (transmission and scanning) microscopy. A neurulation overlap zone occupied this level. The dorsal portion of the neural tube formed by bending of the neural plate and approximation and fusion of neural folds (i.e., by primary neurulation), and the ventral part formed during secondary neurulation by cavitation of an initially solid, compact mass of cells, the medullary cord, derived from the tail bud. Secondary neurulation involved four morphogenetic processes: (1) segregation of the cells of the prospective medullary cord from cells of adjacent regions, (2) formation of a precisely delimited medullary cord, (3) cavitation of the central portion of this cord, and (4) coalescence of all lumina into a single, central cavity. Cell segregation was associated with the formation of a layer of primarily extracellular materials between adjacent organ rudiments. The source and composition of these materials are unknown. Formation of the medullary cord entailed considerable elongation of the peripheral cells of this developing structure and the fabrication of small intercellular junctions, first at the basal (outer) ends of the elongating peripheral cells, and then at their apical (inner) ends. These events resulted in the formation of an outer pseudostratified layer of radially arranged, columnar cells, having characteristics similar to those of the neural plate, and an inner cluster of irregularly shaped and arranged cells. Cavitation always occurred first at the junction between these two cellular populations. The central cells of the medullary cord also eventually elongated, like the peripheral cells, and may have been intercalated into the lateral walls of the developing neural tube as lumina coales

ISSN:0002-9106    

DOI:10.1002/aja.1001580106

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe process of revascularization of free grafts of the extensor digitorum longus muscle in rats has been studied by gross, histological and electron microscopic methods. During the first day after transplantation the muscle is entirely avascular, and it consists of a thin peripheral zone of surviving muscle fibers and a large central area of ischemic muscle. The original blood vessels of the graft undergo a sequence of intrinsic and cell‐mediated destruction. Scattered sinusoidal vessels begin to grow into the graft starting on the second day, and ingrowing blood vessels progressively invade the deeper tissues of the graft. Most new vessels form in the connective tissues, but some vessels, especially larger ones, grow into persisting basal laminae from preexisting vessels and, occasionally, even into basal laminae from degenerated muscle fibers and nerves. The differentiation of new arterioles and venules in free muscle grafts is described. By the end of the first week, the entire graft is revascularized, and ultimately a fairly normal relationship between new capillaries and regenerating muscle fibers is established. In mature grafts, however, irregularities are sometimes found in the organization of smooth muscle cells associated with larger vessel

ISSN:0002-9106    

DOI:10.1002/aja.1001580107

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe ability of unsegmented paraxial mesoderm from Japanese quail embryos to form somites was studied by culturing pieces of embryos, containing the segmental plates, on an agar medium. In the first experiments, two explants were prepared from each donor embryo. Both explants contained a segmental plate and neural tube, but only one contained notochord. The explants containing notochord formed 11.4 ± 2.1 somites, while the explants without notochord formed 11.1 ± 1.3 somites. It was concluded that explants containing Japanese quail segmental plates readily form somites in culture and that the continued presence of the notochord is not required for these somites to form. In a second series of experiments, one explant from each donor embryo contained neural tube and notochord along with the segmental plate, while the corresponding explant did not contain axial structures. The results, which were similar to those obtained in the first experiments, indicated that neither neural tube nor notochord is required for somitogenesis in vitro. Additional experiments demonstrated that bilateral symmetry extends to the unsegmented somite mesoderm, where there was a strong tendency for each segmental plate of a given embryo to form the same number of somites. It was also shown that over a three‐fold range of segmental plate length, there was only a slight tendency for shorter segmental plates to make fewer somites. It was estimated that Japanese quail embryos having five to 21 pairs of somites have segmental plates that represent 11.3 ± 2.9 prospective somites

ISSN:0002-9106    

DOI:10.1002/aja.1001580108

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

年代:1980

数据来源: WILEY

摘要:

AbstractApplication of cytochemical methods for complex carbohydrates at the light and electron microscopic levels served further to differentiate secretory cells of the rat tracheobronchial surface epithelium into serous and mucous categories, and permitted subclassification of serous cells into four types and of mucous cells into three types. The granules in different serous cells and Clara cells varied in staining with the periodic acid‐thiocarbohydrazide‐silver proteinate (PA‐TCH‐SP) method, but generally lacked dialyzed iron (DI) affinity and apparently contained neutral glycoprotein. However, in some focal areas, serous and Clara cell granules showed a pattern of DI staining similar to the PA‐TCH‐SP reactivity. The PA‐TCH‐SP and DI methods stained granule glycoconjugate comparably in the three mucous cell types. The lack of high iron diamine (HID) affinity in these sites testified to carboxylated, periodate‐reactive mucosubstance, presumably sialylated glycoprotein. The luminal surface of the apical plasmalemma of all surface epithelial cells stained with DI but lacked HID affinity. The PA‐TCH‐SP technique stained the surface of the apical plasmalemma of mucous cells, serous cells, and Clara cells in decreasing order of intensity. Microvilli of ciliated cells were PA‐TCH‐SP‐positive, but cilia were unreactive and apparently contained a glycosaminoglycan rather than the presumed sialylated glycoprotein of the other surfaces. DI and PA‐TCH‐SP reactivity of the apical far exceeded that of the basolateral plasmalemma in all surface epithelial cells. Two strata, presumed to be the lamina lucida and the lamina diffusa of the basement membrane under all the surface epithelial cells, stained with the DI but not the PA‐TCH‐SP method and apparently contained glycosaminoglycan. Intraepithelial cells, interpreted as globule leukocytes, appeared to represent mast cells infiltrating the epithelium

ISSN:0002-9106    

DOI:10.1002/aja.1001580109

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

年代:1980

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001580101

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

年代:1980

数据来源: WILEY