摘要:

AbstractThe objective of this study was to determine how the coronary artery stems develop in the chick embryo. The hearts of 51 inkinjected and cleared chick embryos, aged embryonic days 6, 6.5, 7, 7.5, 9, and 10, were dissected, examined, and selectively photographed. Two representative hearts from each group were paraffin embedded, serially sectioned at 10 ¨︁m, and examined for aortic endothelial budding. We found that the proximal coronary artery did not appear to grow outward from the aorta as commonly described in the literature. It appeared to originate from a capillary ring which encircled the aortic and pulmonary outflow tracts. On embryonic day 7.5, one to three channels arising from this ring penetrated each aortic sinus, in an area of darker textured endothelium. Histologically and grossly, multiple channels were still apparent on day 9, particularly in the left coronary artery. One of these channels always became dominant to form the stem. Each stem, which varied in length from embryo to embryo, always ended in a plexus of sinusoidal endothelial tubes. By day 10, the coronary artery stems were longer, with many major branches. Histologically, evidence of multiple channels still was visible. It is significant that channels from the bulbar vascular ring penetrated the aorta at very specific points in the aortic sinuses and did not penetrate the pulmonary trunk or other aortic sites. We believe this fact indicates that the penetration of the aortic sinuses by channels from the bulbar vascular ring represents a controlled invasion of the aor

ISSN:0002-9106    

DOI:10.1002/aja.1001880202

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

年代:1990

数据来源: WILEY

摘要:

AbstractUsing the computer‐assisted method of smoothed spatial averaging, spatial and temporal patterns of cell distribution and mitotic activity were analyzed in the cranial mesenchyme underlying the mesencephalic neural folds of mouse embryos maintained in roller tube culture. Total cell density increased in central and medial mesenchymal regions after 12 hr in culture, decreased after 18 hr, and showed a further decrease after 2 hr when the neural folds of the embryos had elevated, converged, and were fusing or fused. Mitotic activity, as measured by the ratio of3H‐thymidine‐labeled cells to unlabeled cells, was highest in the central mesenchyme at all culture times.Embryos were also cultured in the presence of diazo‐oxo‐norleucine (DON), which inhibits glycosaminoglycan and glycoprotein synthesis. After 24 hr in culture, neural folds of DON‐treated embryos had failed to elevate. Total cell density increased in central and medial regions of the mesenchyme of DON‐treated folds at 12 hr but showed no significant decrease in these regions with further culture. Mitotic activity was highest in the central mesenchyme of these treated embryos.These results suggest that cell distribution patterns observed in the cranial mesenchyme during neural fold elevation in normal cultured embryos are not produced by regional differences in mitotic activity. Rather, we propose that cell distribution patterns in the central and medial regions of the mesenchyme result from expansion of a glycosaminoglycan‐rich extracellular matrix that disperses cells from these regions and decreases their density. In DON‐treated embryos, in which expansion of the mesenchyme is prohibited by the decreased glycosaminoglycan and glycoprotein content of the extracellular matrix, mitotic activity apparently determin

ISSN:0002-9106    

DOI:10.1002/aja.1001880203

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

年代:1990

数据来源: WILEY

摘要:

AbstractHyaluronate (HA) distribution patterns were examined in the cranial mesenchyme underlying the mesencephalic neural folds of mouse embryos maintained in roller tube culture. Using standard image‐processing techniques, the digitized images of Alcian blue‐stained or3H‐glucosamine‐labeled sections digested with an enzyme specific for HA, were subtracted from adjacent, undigested sections. The resultant difference picture images (DPI) accurately depicted the distribution of stained or labeled HA within the cranial mesenchyme.3H‐glucosamine‐labeled HA was distributed uniformly throughout the cranial mesenchyme as 12, 18, and 24 hr of culture. By contrast, the mesenchyme was uniformly stained with Alcian blue at 12 hr, but stain intensity decreased in the central regions of the mesenchyme at 18 and 24 hr.HA distribution patterns were also examined in the cranial mesenchyme of embryos cultured in the presence of diazo‐oxo‐norleucine (DON), a glutamine analogue that inhibits glycosaminoglycan and glycoprotein synthesis. In DON‐treated mesenchyme, Alcian blue staining of HA was decreased from that in controls at 12, 18, and 24 hr. However, incorporation of3H‐glucosamine into HA was increased. The distribution of labeled HA within treated mesenchyme as 12, 18, and 24 hr resembled that in controls at 12 hr.These results indicate that the distribution of HA within the cranial mesenchyme of normal mouse embryos during neural fold elevation and convergence is not determined solely by regional differences in HA synthesis. We propose that HA distribution patterns result from the expansion of the HA‐rich extracellular matrix of the central mesenchyme regions. This expansion may play a major role in fold elevation. These results also suggest that DON treatment reversibly inhibits HA synthesis, since treated mesenchymal cells retain the capability of synthesizing HA when provided with a glucosamine substrate. Patterns of3H‐glucosamine incorporation by DON‐treated mesenchyme are similar to those observed in control mesenchyme prior to mesen

ISSN:0002-9106    

DOI:10.1002/aja.1001880204

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

年代:1990

数据来源: WILEY

摘要:

AbstractMorphological differentiation of uterine stromal and luminal epithelial cells was studied in steroid‐injected ovariectomized rats following unilateral intrauterine instillation of sesame oil, phosphate‐buffered saline containing gelatin (PBSG), PBSG + indomethacin (IM; an inhibitor of prostaglandin synthesis), or PBSG + IM + prostaglandin E2(PGE2). The latter two treatments were preceded by a subcutaneous injection of IM. Uteri were examined by light and electron microscopy at intervals between 8 and 120 hr (n = 4/treatment/time). Differentiation began in the periluminal antimesometrial region and progressed peripherally and towards the mesometrial aspect in all groups. Structural features and timing of differentiation were similar for oil‐injected and PBSG‐infused uteri. Administration of IM inhibited the onset of the decidual cell reaction and had deleterious effects on the luminal epithelium. Inclusion of PGE2in the instillate accelerated stromal cell differentiation and overcame the inhibitory effects of IM. The results implicate prostaglandins, particularly PGE2, in endometrial transformation during decidual

ISSN:0002-9106    

DOI:10.1002/aja.1001880205

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe distribution of neuropeptide Y‐immunoreactive (NPY‐IR) perikarya, fibers, and terminals was investigated in the brain of two species of hibernatory ground squirrels,Spermophilus tridecemlineatusandS. Richardsonii, by means of immunohistochemistry. In the telencephalic and diencephalic structures studied, distinct patterns of NPY‐IR were observed which were essentially identical in male and female animals of both species. No differences in amount or distribution of NPY‐IR structures were observed between animals which had been in induced hibernation for several months before sacrifice in March/April and those sacrificed one week after their capture in May. In some brain structures (e.g., the hypothalamic arcuate nucleus), IR cell bodies were observed only after pretreatment with colchicine.NPY‐IR perikarya and fibers were found in the cerebral cortex, caudate nucleus‐putamen, and dorsal part of the lateral septal nucleus. Dense fiber plexuses were seen in the lateral and medial parts of the bed nucleus of the stria terminalis. The numbers of IR perikarya observed in the medial part of the nucleus increased following intraventricular colchicine injections. The accumbens nucleus exhibited few IR cells and many fibers. Claustrum and endopiriform nuclei showed a considerable number of stained cells and fibers that increased in number and staining intensity in colchicine‐treated ground squirrels. The induseum griseum showed a small band of IR cell bodies and varicose fibers. Bipolar of multipolar IR cells and varicose fibers were found in the basal nucleus of the amygdala.Dense fiber plexuses as well as IR terminals were seen in the median, medial, and lateral preoptic areas of the hypothalamus. Terminals and relatively few fibers were located in the periventricular, paraventricular, and supraoptic nuclei. The anterior, lateral, dorsomedial, and ventromedial hypothalamic nuclei contained relatively large numbers of terminals and fibers. In the suprachiasmatic nuclei, dense terminals were distributed mainly in the ventromedial subdivision. In the median eminence, immunoreactive terminals were concentrated in the external layer, with fibers predominant in the internal layer. NPY‐IR perikarya were observed only in the arcuate nucleus of the hypothalamus and only following colchicine treatment. In the epithalamus (superficial part of the pineal gland and habenular nuclei), varicose fibers appeared mainly in perivascular locations (pineal) or as a dense plexus (habenular nuclei). These results from ground squirrels are discussed in comparison to those obtained in other species and with regard to considerations of the physiologi

ISSN:0002-9106    

DOI:10.1002/aja.1001880206

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

年代:1990

数据来源: WILEY

摘要:

AbstractAuditory hair cells of three lizard and one snake species were studied by serial transmission electron microscopy (TEM) sections of two unidirectinal hair cells (UHC) and two bidirectional hair cells (BHC) and by nonserial section montages of each entire papilla cut at 2‐μm intervals across the papillar width. The unidirectional hair cell region of the agamid lizard,Acanthosaura crucigera, lacked efferent innervation. Another agamid lizard,Agama agama, studied by nonserial section only, lacked efferent innervation to the UHC. Afferent innervation to both the UHC and BHC ofAcanthosaurawas primarily exclusive (each nerve fiber innervates only one hair cell), although an occasional nerve fiber innervated two hair cells. Both the UHC and the BHC of the anguid,Celestus costatus, were exclusively innervated. Both hair cell types of the varanid,Varanus exanthematicus, were nonexclusively innervated (all afferent nerve fibers innervate two or more hair cells). The auditory papilla of the colubrid snake,Elaphe obsoleta, has only one type of hair cell and each is nonexclusively innervated. The numbers of afferent and efferent nerve fibers and of afferent synapses are presented in tabular fo

ISSN:0002-9106    

DOI:10.1002/aja.1001880207

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

年代:1990

数据来源: WILEY

摘要:

AbstractColloid‐containing follicles and ciliated cysts in the hypophysial pars tuberalis of guinea pigs at various ages ranging from 5 days to 36 months were examined by periodic acid‐Schiff (PAS) reaction, immunohistochemistry, and electron microscopy. The follicles storning PAS‐positive colloid were encountered in the pars tuberalis of all guinea pigs examined, although only a few were present in young animals. The follicles gradually increased in number with age. The largest number of follicles was found in the senile male group: 141.3 ± 11.9, about 10 times the number in the 5‐day‐old male group. The follicles were scattered throughout the entire length of the pars tuberalis. Follicles with enlarged luminal cavities were concentrated in the ventral caudal region surrounding the infundibular stem and merges with the pars distalis. Three different types of follicles were found by electron microscopy:(1) those surrounded by nongranulated follicular cells that may correspond to the stellate‐follicular cells in the pars distalis, (2) those surrounded by specific cells that were packed with vesicular inclusions, and (3) those surrounded by granulated cells that may be gonadotropes. In the follicles lined by nongranulated follicular cells, long, prominent microvilli and cytoplasmic processes protruding into the lumen and invaginations of colloid were often observed at the apical cell region. The follicles lined by the specific cells having numerous vesicles were localized only in the ventral caudal portion. The vesicles ranged from 200 to 700 nm in diameter, and the outer surface of their limiting membrane was partly studded with ribosomes. Gonadotropes immunoreactive to the luteinizing hormone (LH) and follicle‐stimulating hormone (FSH) antisera were distributed in the guinea pig pars tuberalis. As well as the typical follicles described above, the follicles composed solely of granulated cells showed microvilli protruding into the cavities and junctional complexes at the apical lateral surface. They stored heterogeneous materials in the lumina. Some secretory granules gave the appearance of being discharged into the lumen. Ciliated cysts were frequently observed in the pars tuberalis; their incidence was 71.7%. The ciliated cysts were much larger than colloid‐containing follicles. Cystic cavities were only partly filled with heterogeneous materials showing colloid‐like, flocculent, and

ISSN:0002-9106    

DOI:10.1002/aja.1001880208

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

年代:1990

数据来源: WILEY

摘要:

AbstractWe used a panel of histochemical techniques to identify and characterize the cell‐associated extracellular material at the surface of the frog's taste organ. We employed morphological and histochemical techniques using both the light microscope and the electron microscope. Results show that the apical, external aspect of cells reaching the surface of the taste organ is in close contact with a layer of amorphous material. The histochemical characteristics of this material vary according to the cell type with which it is in contact. Three different microenvironments can be identified at the surface of the frog's taste organ: type 1 microenvironment is associated with the superficial layer of mucus (secretory) cells; type 2 microenvironment characterizes the surface of the so‐called wing cells, which reach the surface of the taste organ as thin laminae running among mucus cells; and type 3 microenvironment shrouds the free endings of putative taste cells and is rich in calcium and lipids. Type 2 and type 3 microenvironments fix peroxidase (a sapid macromolecule) with increasing affinity. We conclude that highly differentiated microenvironments exist at the surface of the frog's taste organ, and these could play a role in the chain of biological events leading to the taste sensation. Furthermore, characterization of the cellassociated, specific microenvironments can help clarify the role of the different cell types in the frog's taste or

ISSN:0002-9106    

DOI:10.1002/aja.1001880209

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

年代:1990

数据来源: WILEY

摘要:

AbstractThe pigmentation pattern of ventral skin of the frogRana esculentaconsists mainly of melanophores and iridophores, rather than the three pigment cells (xanthophores, iridophores, and melanophores) which form typical dermal chromatophore units in dorsal skin. The present study deals with the precise localization and identification of the types of pigment cells in relation to their position in the dermal tracts of uncultured or cultured frog skins. Iridophores were observed by dark‐field microscopy; both melanophores and iridophores were observed by transmission electron microscopy.In uncultured skins, three levels were distinguished in the dermal tracts connecting the subcutaneous tissue to the upper dermis. Melanophores and iridophores were localized in the upper openings of the tracts directed towards the superficial dermis (level 1). The tracts themselves formed level 2 and contained melanophores and a few iridophores. The inner openings of the tracts made up level 3 in which mainly iridophores were present. These latter openings faced the subcutaneous tissue.In cultured skins, such pigment‐cell distribution remained unchanged, except at level 2 of the tracts, where pigment cells were statistically more numerous; among these, mosaic pigment cells were sometimes obser

ISSN:0002-9106    

DOI:10.1002/aja.1001880210

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

年代:1990

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001880201

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

年代:1990

数据来源: WILEY