摘要:

AbstractThe nature of the microcirculation of the diaphyseal portion of long bones and the adjacent bone marrow is poorly understood. The purpose of this study was to describe the blood supply in the diaphyseal cortex and the relationship of the bone vascular circulation to that of the bone marrow in the growing rat. India ink‐gelatin was infused in the arterial system of 3‐month‐old rats and the vascularization was determined from histological sections. In some studies the periosteal circulation was blocked but the nutrient and metaphyseal arteriole systems were left intact. In the growing rat, most of the vascular flow appears to be centripetally through the diaphyseal cortex and this appears to be the primary blood supply for the adjacent bone marrow. The India ink traversed the cortex and entered the marrow through osteal canals at the endocortical surface. At the marrow‐endocortical bone surface interface, ink exiting from the osteal canals filled the adjacent marrow sinusoids in what appeared as “bush‐like” structures. From the bone marrow the ink appeared to drain into the central vein. Some arterioles from the nutrient system were found to penetrate the inner two thirds of the cortical bone and then re‐enter the bone marrow. The centripetal flow of blood and the importance of the cortical flow for perfusion of the hemopoietic tissue was further documented when periosteal flow was obstructed. In this situation, the cortical bone and adjacent bone marrow were not perfused while the nutrient system and central vein were filled with ink. These results show that in the growing rat, the diaphyseal circulation is almost entirely centripetal and the adjacent hemopoietic tissues are perfused mostly with blood that must first traverse the cortical bone. © 1992

ISSN:0003-276X    

DOI:10.1002/ar.1092330202

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

年代:1992

数据来源: WILEY

摘要:

AbstractAlthough exercise‐induced muscle fiber hyperplasia has been demonstrated through direct fiber counts following nitric‐acid digestion of muscle, morphological studies to determine the mechanism of hyperplasia have not been performed previously. In this study, light and electron microscopy were used to evaluate evidence of muscle fiber splitting or de novo formation of new muscle fibers. Since both fiber hypertrophy and hyperplasia may result in alterations in the muscle nuclear populations, myonuclear number and satellite cell frequency were assessed quantitatively to determine their role in regulating muscle fiber size. Ten adult cats performed weight‐lifting exercise, and the right (exercised) and left (control) forelimbs were fixed by vascular perfusion. Spaced serial sections were used to evaluate muscle fiber morphology along the lenght of fibers, and muscle fiber areas were measured. Myonuclei and satellite cells were counted using electron microscopy. Morphological evidence supporting muscle fiber hyperplasia was observed in exercised muscles. These observations included the presence of small fibers which may signify de novo fiber formation. Myonuclear counts indicate that myonuclear density is not a primary regulator of fiber size. Satellite cell frequency was unchanged following exercise. Autoradiographic studies revealed satellite cell activation by uptake of tritiated thymidine in exercised muscles. Satellite cell activation appears to result from increased activity in exercised muscles. These findings confirm previous studies demonstrating muscle fiber hyperplasia following weight‐lifting exercise, and suggest that de novo fiber formation is the major mechanism contributing to muscle fiber hyperplasia in this model. © 1992 Wiley

ISSN:0003-276X    

DOI:10.1002/ar.1092330203

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

年代:1992

数据来源: WILEY

摘要:

AbstractFor many species, blastocyst implantation is associated with a reduction in the number of cellular and extracellular matrix layers which separate the trophoblast from maternal vasculature. Following loss of uterine epithelial cells along the distal mural trophoblast, the mouse blastocyst encounters the residual epithelial basement membrane. This sheet of extracellular matrix must be breached and later removed prior to trophoblast invasion of the uterine stroma and formation of the placenta. The interactions between the trophoblast, luminal epithelial basement membrane, and decidual cells during the time when embryonic and uterine stromal cells first achieve contact were examined in this study.Distal mural trophoblast of activated delay blastocysts was in contact with the residual luminal epithelial basement membrane 36 hr after estrogen administration. This portion of the basement membrane contained areas in which the usual linear appearance was changed to an irregular, tortuous profile. The lamina densa frequently appeared flocculent and diffuse. Cytoplasmic processes from trophoblast and decidual cells simultaneously perforated the basement membrane at multiple discrete loci. With further development the basement membrane was lost, leaving trophoblast and decidual cells in close contact over large areas.In normally implanting blastocysts a similar stage of embryonic development, as described above, was attained by 0400 hr on day 6 of pregnancy. Regions of convoluted epithelial basement membrane were also seen in these implantation sites. However, only decidual cell processes were seen penetrating the residual basement membrane. These processes extended to the fetal side of the basement membrane and separated that matrix from overlying trophoblast. They contained organelles and formed rudimentary intercellular junctions with the trophoblast. It is concluded that decidual cells play an active role in the penetration of the epithelial basement membrane and may aid in its disintegration. © 1992 Wiley‐Liss, I

ISSN:0003-276X    

DOI:10.1002/ar.1092330204

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe light and electron microscopic appearance of the various epithelial cells lining the efferent ducts and different regions of the epididymis were examined in rats on postnatal days 21, 39, 49, 56, and 90 to determine the role of androgens and/or spermatozoa, as well as other possible factors, on the structural differentiation of these cells. Five conclusions may be drawn from the observations made. First, on day 21 epithelial cells of all regions are structurally undifferentiated. Second, it was not until day 49 that nonciliated cells of the efferent ducts resembled those of adult animals, suggesting that more than one factor, such as androgens, testicular products, and/or spermatozoa, is needed for their full structural differentiation. Third, principal cells of the epididymis become structurally differentiated by day 39, i. e., these cells contained an elaborate Golgi apparatus, endoplasmic reticulum cisternae, and numerous 200–400 nm electron lucent secretory vesicles, as well as a full complement of endocytic organelles; this occurred in spite of the absence of spermatozoa in the epididymal lumen. The differentiation of these epididymal cells may be under the influence of androgens, which are known to be high at this time, but may also be due to specific secretions from Sertoli cells secreted directly into the efferent ducts. Fourth, clear cells of the cauda epididymidis are fully differentiated by day 39. The presence of degenerating germ cells in the lumen of the cauda epididymidis and various cellular debris, as well as high androgen levels, may be factors causing the differentiation of the cells of this region. Finally, clear cells of the corpus and cauda epididymidis only become fully differentiated by day 49, at a time when spermatozoa appear in the lumen, despite high levels of androgens at day 39; this observation indicates that the presence of spermatozoa in the lumen may be a necessary factor in causing their differentiation. Overall, these results suggest that a combination of different factors are necessary for the structural differentiation of the various epithelial cell types of the different regions of the epididymis. © 1992 Wiley‐Liss,

ISSN:0003-276X    

DOI:10.1002/ar.1092330205

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

年代:1992

数据来源: WILEY

摘要:

AbstractCloacae were examined from male and female salamanders representing 12 genera and 22 species in the Salamandridae. All female salamandrids possess numerous sperm storage glands, spermathecae, in the roof of the cloaca, but intergeneric variation exists in the occurrence of additional cloacal glands.PleurodelesandTylototritonpossess both vent and anterior ventral glands, and secondary loss has occurred of vent glands in all other genera and anterior ventral glands inChioglossa, Cynops, Paramesotriton, andTriturusThe most highly derived cloaca occurs inEuproctus asper, in which the cloacal tube extends through a conical projection, and ventral glands secrete onto the dorsolateral surface of the projection rather than into the cloaca. Marked intergeneric variation occurs in males in conformation of the cloacal cavities and in extent of the dorsal gland. InCynops, Euproctus, Pachytriton, Paramesotriton, Taricha, andTriturus, the pseudopenis (a broad, posteriorly projecting evagination of the dorsal roof) fills much of the cavity of the anterior cloacal chamber. In most salamandrids, distal ends of the dorsal glands occur lateral to pelvic glands in the anterior end of the cloaca, and dorsal gland tubules descend to secretory sites at the posterior end of the vent.SalamandraandMertensiellapossess a unique, bifurcated dorsal gland in which distal ends of tubules lie dorsal to the other cloacal glands, and proximal ends curve ventrally in the anterior end of the cloaca to secretory sites along the cloacal orifice. Cladistic analyses indicate that the variation in presence of anterior ventral glands is due to homoplasy. The occurrence of female vent glands, bifurcated dorsal glands, and the pseudopenis supports a phylogeny based upon noncloacal characters. © 1992 Wiley‐Liss, I

ISSN:0003-276X    

DOI:10.1002/ar.1092330206

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

年代:1992

数据来源: WILEY

摘要:

AbstractWe examined the disassembly and reformation of the Golgi apparatus as a function of the cycle of the seminiferous epithelium in adult rats during stages XIII and XIV, i. e., just prior to and during meiosis I and II. Serial section analysis of primary spermatocytes at metaphase I demonstrated the presence of two Golgi complexes. At the ultrastructural level, these Golgi complexes were shown to be composed of stacks of cisternae and vesicles, with each stack having a varying number of saccules. Although Golgi complex intermediates resulting from the process of organelle disassembly were not clearly identified in diplotene spermatocytes immediately prior to nuclear envelope vesiculation, we did observe clusters of vesicles resembling the “nuage,” with each cluster varying in size and number of vesicles. Meoisis I results in the formation of secondary spermatocytes that exhibit a well‐formed spherical Golgi complex approximately half the size of the diplotene spermatocyte Golgi. Next, secondary spermatocytes enter meiosis II. In contrast to metaphase I, during metaphase II reformation of the Golgi apparatus into stacks was not observed and only small clusters of vesicles at two poles of dividing cells were detected. In addition, “nuage”‐like structures were not identified during meiosis II.Our results begin to characterize the process by which Golgi apparatus partitioning is accomplished during meiosis, presumably resulting in the delivery of equal complements of this organelle to four round spermatids. We suggest that partitioning of the Golgi apparatus takes place prior to metaphase I and that the two steps of meiosis may exhibit subtle differences with respect to Golgi partitioning. © 1992 Wil

ISSN:0003-276X    

DOI:10.1002/ar.1092330207

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

年代:1992

数据来源: WILEY

摘要:

AbstractForty‐nine 12‐week‐old male Syrian golden hamsters (Mesocricetus auratus), weighing 108 to 128 g, were injected i. p. with [3H]‐thymidine (3HTdR 2 μCi/g body wt). Animals were divided into 7 weight‐matched groups and were killed at 1 hour (day zero) and 1, 2, 3, 4, 7, and 14 days after thymidine injection. Lungs were fixed by vascular perfusion of 4% formalin/1% glutaraldehyde in 0.2 M cacodylate buffer at pH 7.4, cut at 2 μm, dipped in Kodak NTB3 or NTB2 nuclear emulsion, exposed for 2 weeks, developed and stained. In each airway cross‐section, total epithelial and fibroblast counts and labeled cell count were estimated. A cell was considered labeled when 3 or more silver grains appeared on its nucleus. The background grain count was less than 1 grain per nucleus.Mean epithelial and fibroblast cell density in a 100 μm segment were respectively 14.8 ± 0.1 and 6.6 ± 0.1 cells (the second number is one standard error of the mean). One hour after labeling, their respective labeling indices (L. I.) were 0.13 ± 0.02 and 1.24 ± 0.1. On day 1, their L. I. doubled and then returned to the initial value. One hour after labeling, epithelial and fibroblast mean grain counts did not differ significantly. They were respectively 20.6 + 1, and 15.8 ± 2. Because grain count intensity is closely related to DNA synthetic time, it seems plausible that epithelial and fibroblast synthetic times do not differ much. Cell turnover and cell cycle times were estimated from grain count dilution curves. The respective loggrain dilution slopes, ‐0.025 ± 0.005 and ‐0.044 ± 0.014 do not differ significatly when tested by t‐test. It is concluded, therefore, that both cell types turn over at the same rate with an estimated cell cycle time of 20 d

ISSN:0003-276X    

DOI:10.1002/ar.1092330208

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe tracheal mucosa of the Syrian golden hamster has been extensively employed as a model system for respiratory tract cell renewal, injury, and carcinogenesis. However, baseline cell kinetic data are not available for normal juvenile and adolescent animals in which the mucosa and cartilage are rapidly enlarging. The objective of this research was to elucidate alterations in cell kinetics, epithelial morphology, and gene expression in the trachea of hamsters at different ages. Cell kinetics were examined by3H‐thymidine labeling indices, morphology by light and electron microscopic examination, and gene expression by slot blot analysis. Results showed that mucosal epithelium of the young and adolescent hamster undergoes cyclic necrosis and cell shedding, exposing portions of the elastic basal lamina. Epithelial shedding was associated with hyperplasia and squamous metaplasia. Additionally, the labeling indices of mucosal epithelial cells and chondroblasts also exhibited variable patterns which were associated with a cyclic pattern of expression of c‐fos and c‐erB2 proto‐oncogenes and epidermal growth factor receptor. © 1992 Wiley

ISSN:0003-276X    

DOI:10.1002/ar.1092330209

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

年代:1992

数据来源: WILEY

摘要:

AbstractNeuroectoderm‐derived epithelia of the primary nasal cavity and the fourth ventricular floor and roof were observed by scanning (SEM) and transmission electron microscopy (TEM) and SEM‐TEM correlative views in mouse embryos of 9th to 13th days of gestation, and in 38 externally normal human embryos ranging at Carnegie stages from 13 to 18 (about 5 to 7 weeks of gestation). Smooth‐surfaced spindle‐shaped cells with one or more cytoplasmic processes and cord‐like cytoplasmic structures were observed by SEM on the wall of the primary nasal cavity of both species. They had morphological features similar to those of neuronal type 1 supraependymal (SE) cells and SE fibers on the floor and roof of the fourth ventricle in both species. Type 1 SE cells, SE fibers, and corresponding structures in the primary nasal cavity were localized in relation to the underlying developing nerve and vascular systems. Furthermore, their processes and fibers ran roughly parallel to these underlying structures and they penetrated the epithelial layer at the ends, suggesting a connection with underlying structures. From TEM and SEM‐TEM correlative observations, SE fibers in the fourth ventricle and cord‐like structures in the primary nasal cavity, both with a larger diameter, were deduced as single axon‐like processes or bundles of processes. Those fibers and cord‐like structures of smaller diameters were interpreted as elongated telophase bridges; both contained parallel packed microtubules and connected distant cells. Since these processes and fibers were generally longer and became fewer at later developmental stages, they appeared to be transient neuronal structures. They may play a development‐related role in such morphogenetic cell movements as in the developing nerve and vascular systems in the epithelial and/or subepithelial layers, but not as direct rudiments of adult nerve tissues. ©

ISSN:0003-276X    

DOI:10.1002/ar.1092330210

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

年代:1992

数据来源: WILEY

摘要:

AbstractThe morphology of the paranodal and postnodal levels of the neural plate as well as the fate of its cells was examined in chick embryos at stages 3–11. The morphology of the paranodal and postnodal levels of the neural plate closely resembles that of the prenodal neural plate. Furthermore, during shaping and bending of the neural plate, these levels undergo changes similar to those of the prenodal level. In short, the paranodal and postnodal levels of the neural plate consist of a pseudostratified columnar epithelium that thickens dorsoventrally and narrows mediolaterally and then undergoes localized furrowing and folding. Fate mapping revealed that at mid‐neurula stages, the prospective hindbrain and spinal cord levels of the neuraxis flank the primitive streak. Hensen's node moves caudally with respect to these future neuraxial levels as it regresses during the latter stages of gastrulation. Cells of the medullary cord, the rudiment of the secondary portion of the neural tube, arise in the vicinity of the cranial portion of the primitive streak, near the caudal end of the postnodal levels of the neural plate. Thus, during stages of gastrulation and primary neurulation, the precursor cells of the primary and secondary portions of the neural tube (spinal cord) lie in close proximity to one another. This study provides new information on the morphology and extent of the paranodal and postnodal levels of the neural plate, the changes these areas undergo during shaping and bending oif the neural plate, and the contributions of its cells to the primary and secondary levels of the neural tube, increasing our understanding of the complex events underlying avian gastrulation and neurulation. © 1992 Wiley‐Lis

ISSN:0003-276X    

DOI:10.1002/ar.1092330211

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

年代:1992

数据来源: WILEY