bluuebunny/crossref_metadata_2025_split huggingface dataset:
Epithelial influences on skeletogenesis in the mandible of the embryonic chick
Authors: Tyler Mary S. , Hall Brian K. 
Published: February 2005

AbstractIntact mandibular processes and the enzymatically separated mesenchymal and epithelial components of the mandible from embryonic chicks of 2.5‐ to 5‐day incubation (Hamburger and Hamilton, '51: stages 16‐25) were grown individually, either in organ culture or as grafts to the chorioallantoic membranes of host embryos. The differentiation of cultured and grafted intact mandibular processes was histologically normal, but the time of histodifferentiation differed from that in vivo. The histodifferentiation of cultured and grafted mandibular mesenchyme grown isolated from its epithelium depended upon the age of the embryo from which the mesenchyme had been obtained. Intramembranous ossification producing membrane bones of the mandible occurred in mesenchyme isolated from 4.5‐ to 5‐day embryos (HH 24–25), but did not occur in mesenchyme isolated from younger embryos. Cartilage (Meckel's) and subperichondrial bone in the articular process of Meckel's cartilage differentiated in mesenchyme isolated from embryos of all age groups tested (HH 16–25). Mandibular mesenchyme, therefore, requires the presence of epithelium until 4.5 days of incubation if the membrane bones of the mandible are to differentiate; if epithelial influences are required for Meckel's cartilage and subperichondrial bone formation, they are not required beyond 2.5 days of incubation. Mandibular epithelium isolated from its mesenchyme became layers of squamous cells in culture; but when grafted onto the chorioallantoic membrane, the epithelium became underlain by host fibroblasts and differentiated into a stratified squamous epithelium. Mandibular epithelium, therefore, is capable of differentiation in the presence of foreign fibroblasts derived from the chorioallantoic membrane.
Enzymatic isolation of osteoblasts from fetal rat calvaria
Authors: Yagiela John A. , Woodbury Dixon M. 
Published: February 2005

AbstractA microanatomical study of the immature rat calvarium was performed in order to develop a method for the isolation of osteoblasts by enzymatic means. Although generalized osteogenesis was evident in fetal rats, differential growth patterns were observed beginning at 19 days in utero. Considerable portions of the endocranial periosteal bone surface were lined by flattened, less active cells; discrete areas also contained multinucleated osteoclasts. Cell counts of whole calvaria revealed that one fifth of the total cell population were osteoblasts, most of which were located in the central portions of the frontal and parietal bones. Prior excision of these segments permitted the subsequent removal of virtually all periosteal tissues. Cleaned 19‐day fetal bones, incubated in crude collagenase for two hours, released about 40,000 cells/calvarium, consisting of 85‐90% osteoblasts and lesser amounts of connective tissue and bone marrow elements. Because of the relatively small sizes of most extraneous cells, purity on a cell volume basis was approximately 95%. It is predicted this preparation will be useful in the investigation of certain aspects of osteoblastic function.
Experimental cryptorchidism in adult male rats: Histological and hormonal sequelae
Authors: Jones Thomas M. , Anderson Winston , Fang Victor S. , Landau Richard L. , Rosenfield Robert L. 
Published: February 2005

AbstractMature male rats were rendered cryptorchid and followed for up to nine weeks during which serial blood specimens were obtained for multiple hormonal analyses; serial testicular samples were obtained as well. In contrast with control animals, cryptorchid rats showed transient rises in FSH which returned to normal at the end of the study; estrogen levels were high in the final weeks. Plasma testosterone levels were unchanged and LH levels changed little. Light and electron microscopic studies of testicular biopsy specimens showed prompt disruption of spermatogenesis which became more extensive with time. Sertoli cells underwent multiple changes including increased lipid storage and phagocytosis of spermatozoa. Comparisons are made between the sequence of hormonal changes and that of histological changes. In addition, questions are raised concerning the ways in which Sertoli cells are affected by experimental cryptorchidism.
Phagocytosis of spermatozoa by the rabbit vagina
Authors: Phillips David M. , Mahler Susan 
Published: February 2005

AbstractTwenty‐four hours after mating in the rabbit, numerous spermatozoa are observed attached to the surface of the vaginal epithelium. Spermatozoa appear to be attached by their heads to microvilli of the simple columnar cells which compose the vaginal epithelium. Spermatozoa are taken up by the epithelial cells, and they are found within the cells in various stages of de generation up to seven days after mating. Epithelial cells frequently appear to be filled with numerous vacuoles containing sperm components in various stages of degeneration. It is suggested that some property of the surface of sperm heads may render them particularly susceptible to phagocytosis. Phagocytosis of spermatozoa may not have long‐term harmful effects for the epithelium since these epithelial cells presumably have a high rate of turnover.
Laparoscopic exposure and sequential observation of the ovary of the cycling bitch
Authors: Wildt David E. , Levinson Carl J. , Seager Stephen W. J. 
Published: February 2005

AbstractA method was developed to alter surgically the bursa of the bitch to allow sequential observation of the ovary by means of laparoscopy. Adult anesthetized female dogs of three breeds underwent laparoscopic examinations in which each natural bursa slit was lengthened 1.0‐1.5 cm using laparoscopic hook scissors in conjunction with electrocautery. The ovary could be effectively and repeatedly exposed for laparoscopic viewing through the lengthened bursa slit. Neither Laparoscopic surgery nor frequent routine laparoscopic examinations of the reproductive organs had an effect on subsequent ovarian activity. All dogs subjected to the laparoscopic ovarian exposure technique exhibited estrus behavior, follicle development, ovulation and corpus luteum formation.Preovulatory follicular development was detected as early as 11 days before ovulation with the most rapid follicular maturation occurring two to three days before ovulation. Follicular collapse and extensive hemorrhage at the rupture site during ovulation did not occur. Release of the cumulus mass from a vesicular follicle was observed in one bitch. The cumulative mass adhered to the follicular wall for an indefinite time following ovulation.The structural size of the bitch corpus luteum was maximal four to eight days following ovulation. Corpora lutea remained visible on the ovarian surface for 16 weeks. No differences in cyclic ovarian morphology were observed among the three breeds of dogs studied.
The ultrastructure of follicle cells in fetal guinea‐pig ovaries
Authors: Jeppesen Th. 
Published: February 2005

AbstractThe development of the follicle cells in fetal guinea‐pig ovaries has been examined in the electron microscope.The findings were as follows: at days 34 and 38 there were broad intercellular clefts within the germinal cords. However, a continuous layer of thin cytoplasmic processes from the follicle cells separated the germinal cords from the stromal compartment. The germinal cords were everywhere limited by a basal lamina. During all the period examined coated vesicles, possibly emptying their contents into the region of the basal lamina, were observed in the follicle cells.At days 42, 46 and 50 the cellular membranes were closely apposed with an intercellular distance of about 200 A. Complexes of deeply interdigitating folds of the membranes of neighboring follicle cells were observed. The follicle cells forming part of the primordial follicles at days 54 and 58 were characterized by a disappearance of these folds and by the appearance of bundles of microfilaments in the cytoplasm. These were especially numerous at day 66.At days 34 and 38 gap junctions were observed between the follicle cells, but not between the follicle cells and the germinal cells. During the entire period examined junctions resembling desmosomes without filaments were observed between the follicle cells as well as between the follicle cells and the germinal cells.The ultrastructure of the follicle cells is considered in detail and the functional significance of the findings discussed.
Intrahepatic distribution of nerves in the rat
Authors: Reilly Frank D. , McCuskey Patricia A. , McCuskey Robert S. 
Published: February 2005

AbstractThe intrahepatic distribution of nerves in the rat was studied using neurohistochemical and electron microscopic methods. Innervation was restricted primarily to vessels in the portal space and hilus. Both adrenergic and cholinergic fibers were observed in the adventitia of hepatic arteries, and to a lesser extent adjacent to portal veins. Some of the cholinergic fibers, however, were not contiguous with the vasculature. Near the hilus many of these fibers were associated with ganglia while peripherally some coursed into the immediately adjacent parenchyma where end bulbs abutted on hepatocytes. Ultrastructurally, scattered small nerves, devoid of neurolemma, were found contiguous with the portal lamina of hepatocytes. Nerve fibers deeper within the lobule were not seen but numerous gap junctions were observed between contiguous hepatocytes. Central and sublobular hepatic veins lacked innervation but adrenergic nerves were demonstrated in the walls of larger hepatic veins. Innervation of the biliary system was sparse. While nerves were interposed between vessels and bile ducts, such nerves tended to be associated more closely with the vasculature.
Specialized cell types in the human fetal small intestine
Authors: Moxey Pamela Colony , Trier Jerry S. 
Published: February 2005

AbstractIn the present study we describe the time of appearance and morphological differentiation of specialized epithelial cells in human fetal small intestine (SB). Proximal and distal SB from 36 nonviable fetuses was studied by light and electron microscopy. During the 9‐ to 10‐week period, villi lined by simple columnar epithelium replaced the stratified epithelial lining which was two to six cell layers thick. During this transition, distinctive junctional complexes and a single secondary lumen were identified in the deeper layers of stratified epithelium, and there was evidence of cellular degeneration of some superficial cells. Oligomucous and mature goblet cells were present in both the stratified and simple columnar epithelium. Crypt formation began proximally at 10 to 11 weeks and, within a week, crypts lined by undifferentiated crypt cells (UCC) could also be identified in the distal SB. These cells resembled adult UCC's except for the presence of large aggregates of glycogen, and the absence of large adult‐type secretory granules (SG) until 16 weeks. At all ages SG's were smaller and less numerous than in adults. Paneth cells appeared with crypt development at 11 to 12 weeks. Unlike adult Paneth cells their SG's were structurally heterogeneous and frequently had cores with halos of differing density. Caveolated or tuft cells with dense bundles of microfila‐ments extending from microvilli into apical cytoplasm, apical granules, occasional caveolae, and a microvillus membrane denser than that of adjacent cells were identified by 16 weeks. Putative microfold (“M”) cells were seen in the distal SB of a 17‐week fetus. These cells had an unusual apical border with irregular projections, many small membrane bound vesicles in the cytoplasm, and were in direct contact with underlying lymphoid cells. The glandular cells of Brunner's glands at 14 to 15 weeks resembled those of normal adult.
PAS‐lead hematoxylin as a stain for small‐granule endocrine cell populations in the lungs, other pharyngeal derivatives and the gut
Authors: Sorokin Sergei P. , Hoyt Richard F. 
Published: February 2005

AbstractEpithelial cells of the several subtypes that comprise the small‐granule cell population of the respiratory system are little studied, partly because adequate silver, monoamine fluorescence and other specific light microscopical preparations have been more difficult to obtain than in the gut and other organs possessing diffuse endocrine systems. Periodic acid‐Schiff (PAS) in combination with MacConaill‐Solcia's lead hematoxylin has in our hands proven dependable for routine staining of serial 2‐m̈m glycol methacrylate sections used in mapping the distributions of these cells along the airway. In lungs of mice, hamsters, kittens, and fetal rabbits, typical small‐granule cells stain weakly or not at all with lead hematoxylin alone, hence are easily overlooked. PAS adds to the cytoplasm a diffuse magenta coloration; and because it is diastase‐resistant, less brilliant than that of mucus but more so than bronchiolar cell secretions, and finer textured than lysosomal staining of other cells present, the effect is to highlight small‐granule cells whether solitary or in clusters. Additional PAS staining of basement membranes and lead hematoxylin staining of cilia enhance the combined stain's resolving power. In thyroid gland, parafollicular cells stand out boldly against follicular elements; in small intestine, hematoxylin‐positive endocrine cells are well differentiated from absorptive, mucous, and Paneth cells that surround them. Using a complementary monoamine fluorescence technique on plastic sections of lungs from control and 5‐hydroxytryptophan‐pretreated animals prior to staining, we can show that fluorescent epithelial cells are identical with those stained by PAS‐lead hema‐toxylin.
The surfactant system of human fetal lung organotypic cultures: Ultrastructural preservation by a lipid‐carbohydrate retention method
Authors: Stratton C. J. , Douglas W. J. H. , McAteer J. A. 
Published: February 2005

AbstractHuman fetal lung organotypic cultures consisted of epithelial elements (≃40‐100 m̈m in diameter) formed by the reaggregation of single cells from a monodisperse suspension of enzymatically dissociated fetal lung. These elements, termed alveolar‐like structures, were composed primarily of type II alveolar epithelial cells whose apical surfaces bordered the central lumen of the alveolar‐like structure. Pulmonary surfactant secreted by the type II cells was retained within the lumen and accumulated in close association with the epithelium. These characteristics made this culture system an advantageous model for the morphological study of human pulmonary surfactant in vitro. A lipid‐carbohydrate retention procedure which reduced the extraction of tissue components and thus provided improved preservation of multilamellar bodies and tubular myelin surfactant was used in an ultrastructural study of organotypically cultured surfactant. Human surfactant was observed for the first time with most of its structural components intact. In vitro human surfactant was found to be similar to in vivo rodent and non‐human primate surfactant, but with certain differences. Long surfactant tubules were not observed. There were more transformed multilamellar bodies present with more foci undergoing transformation. Each focus contained fewer layers of tubular myelin surfactant than occurs in rodent surfactant. No epiphase‐hypophase areas were observed, only tubular myelin surfactant. In addition, a previously unreported intrasurfactant matrix material was observed.
Ultrastructural features of the distended pulmonary arteries of the normal rat
Authors: Meyrick Barbara , Reid Lynne 
Published: February 2005

AbstractDetailed study has been made of the structure of the normal pulmonary artery of rat by both light (1‐μ sections) and electron microscopy. After tying the pulmonary veins at the hilum, the lungs were fixed by simultaneous injection of glutaraldehyde into the pulmonary trunk and trachea. Study of distended arteries allows precise measurement and assessment of normal lung structure.Four regions of the pulmonary artery can be identified by wall structure and are described here‐muscular, partially muscular, non‐muscular and the newly described thick‐walled oblique muscular. Electron microscopic examination has demonstrated in the non‐muscular regions of the partially muscular arteries, an “intermediate” cell and in the non‐muscular arteries, a pericyte. The intermediate cell lies internal to the single elastic lamina but external to the endothelial cell, is surrounded by its own basement membrane and contains filaments mainly along the adluminal region of the cell. The pericyte also lies internal to the single elastic lamina, is within the basement membrane of the adjacent endothelial cell and has previously been reported in the lung only in the walls of alveolar capillaries. The structure of the intermediate cell and its position suggest it is a transitional stage between the pericyte and smooth muscle cell.
Spermatid‐sertoli tubulobulbar complexes as devices for elimination of cytoplasm from the head region of late spermatids of the rat
Authors: Russell Lonnie D. 
Published: February 2005

AbstractThe traditional and generally accepted mode of elimination of excess spermatid cytoplasm, known to take place at the time of sperm release, occurs as a result of the disengagement of the residual cytoplasmic mass. The present study suggests that cytoplasm is also eliminated from the head region of the spermatid in the period prior to sperm release. Data presented herein indicates that the amount of cytoplasm eliminated in this manner is substantial since the volume of spermatid cytoplasm diminishes by about 70% in the period of formation and resorption of tubulobulbar complexes. Reports from this laboratory (Russell and Clermont, '76; Russell, '79) indicated that characteristic evaginations of spermatid cytoplasm, termed tubulobulbar complexes, are resorbed by Sertoli cells in the form of numerous small pockets of cytoplasm. These pockets of cytoplasm are organelle‐free and show a “watery” consistency. They are subsequently degraded by the Sertoli cell prior to sperm release.During the period of turnover of tubulobular complexes the organelles of the cytoplasmic lobe, which at first are loosely organized, become clustered and tightly packed. As a consequence, the cytoplasmic lobe appears electron dense and is stained intensely with toluidine blue. This feature is interpreted, although not proven, to be the result of elimination of the watery component of the cytoplasm via resorption of tubulobulbar complexes by the Sertoli cell. During the period in which tubulobulbar complexes form, there is an open channel in which cytoplasm may flow from the flagellum to the head and out the head into tubulobulbar complexes.
The growth and development of the superior oblique muscle and trochlear nerve in juvenile and adult goldfish
Authors: Easter Stephen S. 
Published: February 2005

AbstractSuperior oblique muscle/trochlear nerve pairs from goldfish of various ages (1‐5 years) have been examined light and electron microscopically. The muscle grows by enlargement (longitudinally and transversely) of individual fibers, and by addition of new ones at the rate of about 250/year. The nerve grows by enlargement of fibers, but few and perhaps nonew axons are added. The somata enlarge, and the neuromuscular synapses become much more numerous. The ratio of muscle fibers to nerve fibers increases from about 5 in the young to about 16 in the old fish.
Neural crest and placodal contributions in the development of the glossopharyngeal‐vagal complex in the chick
Authors: Narayanan C. H. , Narayanan Y. 
Published: February 2005

AbstractBy using the method of quail‐to‐chick transplantation of neural crest in one series (VNG) and placodal ectoderm in a second series (VPG) we were able to determine the relative contribution of cranial neural crest and placodal ectoderm to the formation of the Glossopharyngeal‐vagal complex. In chimeric embryos, quail cells originating from cranial neural crest grafts of postotic levels end up in the root ganglia, while quail cells originating from placodal ectoderm of postotic levels end up in the trunk ganglia. The results clearly indicate that the caudal levels of the medulla and rostral cervical segments represent the site, and the neural crest the source, for the neurons of the root ganglia. The neurons form a homogenous population of the small‐cell type. This clearly rules out any contribution to the root ganglia from placodal ectoderm. On the basis of our experiments, it is also concluded that the neurons of the trunk ganglia are purely placodal in origin and are composed of a population of cells of the large‐cell type. Our experiments also provide convincing evidence for a neural crest origin for Schwann cell and ganglionic Satellite cells.
Morphological characteristics of cells with apical nuclei in the initial segment of the adult rat epididymis
Authors: Sun Eric L. , Flickinger Charles J. 
Published: February 2005

AbstractThe cytology of epithelial cells with apical nuclei in the initial segment of the rat epididymis was studied with the light and electron microscopes. Two types of cells were distinguished and were designated apical cells and narrow cells. The apical cells are more numerous than the narrow cells and closely resemble principal cells except for the location of the nucleus. They probably correspond to the apical cells of Reid and Cleland (′57) and may represent a variation of the principal cell. The narrow cells differ markedly from the apical cells in both light microscopic appearance and fine structure. Narrow cells stain intensely with toluidine blue and are characterized by a slender shape, many mitochondria with tubular cristae, and a large number of apical cup‐shaped cytoplasmic vesicles. The possible relationship of narrow cells to other cell types is discussed.
Differential effect of cytochalasin B on the aggregation of melanosomes in cultured mouse melanoma cells
Authors: Koyama Yoh‐Ichi , Takeuchi Takuji 
Published: February 2005

AbstractMouse B16 melanoma cells in culture were treated with 2 μg/ml cytochalasin B. Melanosomes, localized in dendrites as well as those in the peripheral cell body, formed aggregates which then showed centripetal migration. After 24 hr of treatment, melanosomes were found as large aggregates near the nucleus. However, cytochalasin B showed no effect on the distribution of mitochondria and endoplasmic reticulum. When cells were released from the 24 hr‐treatment with cytochalasin B, each melanosome began centrifugal migration. In this process, melanosomes were situated in the periphery, and were in close association with microtubules. Side arm‐like structures were observed between microtubules and melanosomes, or mitochondria. These results seem to indicate the presence of a mechanism(s) specific to melanosome migration, and possible participation of microtubules in this melanosome migration.
The use of potassium ferricyanide in neural fixation
Authors: Langford Lauren A. , Coggeshall Richard E. 
Published: February 2005

AbstractThe present study suggests a mixture of buffered osmic acid and 1.5% potassium ferricyanide as a post‐fixation to improve the fixation of neural tissue. This procedure results in an improved preservation of membranes as well as cytoplasm and cytoplasmic organelles. It is to be emphasized that the quality of the initial perfusion is the primary determinant of quality of the fixation, but the addition of 1.5% potassium ferricyanide to post‐fixation fluid makes good fixation better and allows data to be gathered from otherwise unusable material.