bluuebunny/crossref_metadata_2025_split huggingface dataset:
Movement of entire cell populations during renewal of the rat incisor as shown by radioautography after labeling with 3H‐thymidine. The concept of a continuously differentiating cross‐sectional segment
Authors: Smith C. E. , Warshawsky H. 
Published: February 2005

AbstractRenewal of the rat incisor was studied in three dimensions by employing a serial cross‐sectioning technique to locate the boundary between labeled and unlabeled cells in the enamel organ and odontoblast layer at various times after a single injection of 3H‐thymidine. This boundary, or leading edge of the front of labeling, was graphically illustrated through point‐plotting reconstruction of the labial surface of the incisor. At one hour after the injection of 3H‐thymidine the front of labeled ameloblasts was located within the presecretory zone related to early predentin secretion. This front formed a “C”‐shaped curve stretching across the labial surface of the tooth from the lateral to the mesial cemento‐enamel junction. The “C” was open anteriorly and the lateral arm extended almost twice as far incisally as the mesial arm. The edge of the front of labeled odontoblasts was positioned apical to and parallel with this “C”‐shaped curve. The morphological appearance of all cells along each respective front was found to be similar. As the fronts of labeled ameloblasts and labeled odontoblasts moved forward with the erupting incisor, the cells along these fronts differentiated simulataneously and subsequently formed enamel and dentin. Throughout this movement the distance between fixed points along the leading edge of the front of labeled ameloblasts, and its positional relationship to the front of labeled odontoblasts, did not change appreciably. This indicated that cells of the tooth were being carried incisally at a uniform speed. It was concluded that renewal in the rat incisor consists of the generation by the bulbous part of the odontogenic organ of epithelial “U”‐shaped cross‐sectional segments which enclose a core of pulp. As this segment is transported towards the gingival margin, cellular differentiation and subsequent formation of hard tissue is seen to begin at the central labial side of the segment and to progress in a mesial and lateral direction towards the lingual side. In the process, the limits of the enamel organ at the mesial and lateral cemento‐enamel junctions are established and the entire circumference of the segment is eventually enclosed by a rim of dentin.
Mitochorial form in hepatic parenchymal cells in rats of several ages
Authors: Stempak Jerome , Laurencin Mary 
Published: February 2005

AbstractSlices of livers from neonatal, 7‐day‐old and adult rats were fixed in osmium tetroxide or a formaldehyde‐osmium tetroxide sequence and processed for electron microscopy. Mitochondria from neonatal hepatic parenchymal cells are pleomorphic. Disc‐shaped forms are common. In 7‐day‐old animals, cylinders are the most numerous single from, discs are present but smaller, and spherical forms increase in number. In the adult, mitochondria are predominantly cylindrical in from. The average volume of neonatal mitochondria is greater than that of 7‐day‐old or adult mitochondria.
Architecture of the marrow vasculature in three amphibian species and its significance in hematopoietic development
Authors: Tanaka Yasukazu 
Published: February 2005

AbstractArchitecture of the bone marrow vasculature, particularly that of the femur, was analyzed in three amphibian species in relation to the early phylogeny of marrow hematopoiesis. A dye‐injection method and histological techniques, including both serial sectioning and reconstruction methods, were used for this purpose. From these observations the following conclusions may be drawn. (1) Marrow hematopoiesis is absent from the femur of the urodelan (Triturus pyrrhogaster) and appears first in the femur of the primitive anuran (Xenopus laevis). (2) The site of primitive hematopoiesis (granulopoiesis) is the subendosteal region where the venous vascular net develops. (3) The primitive vascular architecture observed in the femur of Xenopus is characterized by the absence of a central vein. Subendosteal veins drain the blood from the bone marrow. A vein collateral to the primary artery appears in the femur of Rana catesbeiana, an advanced anuran, in which further development of both the subendosteal venous plexus and hematopoietic activity are noted. In both anura examined, the primitive blood sinuses form near the mid‐shaft of the femur. The proliferation of mesenchymal elements containing dark pigment, presumably melanin, was also noted in this area. (4) The architecture of marrow vessels in Rana approaches the structure noted in mammalian bone marrow. (5) Fat tissue is observed in the urodelan bone marrow prior to the appearance of hematopoietic activity. This indicates that the formation of marrow fat is phylogenetically unrelated to the development of hematopoiesis.The present investigation on primitive hematopoiesis suggests that the development of hematopoietic activity is intimately related to the development of the marrow vasculature, particularly that of the subendosteal venous plexus. A favorable vascular arrangement may be necessary to allow active hematopoiesis.
Ultrastructure of the thyroid in dwarf mice
Authors: Cordier André C. , Denef Jean‐François , Haumont Stanislas M. 
Published: February 2005

AbstractThe thyroid gland of Snell's dwarf mice consists of small follicles with flattened epithelium, partly differentiated cords and undifferentiated masses. Many adipocytes are found. The ultimobranchial cysts are well developed. Parafollicular cells are normal. In the partly organized cords, microfollicular cells and some small follicles limited by two or three cells are seen.The presence of these structures led us to think that they represent the first stages of normal folliculogenesis, described as the fusion of two adjacent unicellular microfollicles. Their further growth is the result of the coalescing of small adjacent follicles or of cellular multiplication. The presence of undifferentiated masses and partly differentiated cords, in dwarf mice, seems due to a developmental arrest rather than to aberrant development. This disorder of organogenesis is ascribed mainly to a lack of pituitary growth hormone.
Immunohistochemical localization of somatostatin, insulin and glucagon in the principal islets of the anglerfish (Lophius americanus) and the channel catfish (Ictalurus punctata)
Authors: Johnson Dana E. , Torrence Judith L. , Elde Robert P. , Bauer G. Eric , Noe Bryan D. , Fletcher Donald J. 
Published: February 2005

AbstractSomatostatin, insulin and glucagon were localized in the principal islets of the anglerfish (Lophius americanus) and the channel catfish (Ictalurus punctata) by means of the unlabeled antibody‐peroxidase‐antiperoxidase immunocytochemical method. Both species showed a similar ratio of positive cells 9:6:4 (insulin:somatostatin:glucagon), but the interrelations of the three cell types differed between species. The large number of somatostatin‐positive cells may be indicative of an important role for this hormone in teleost physiology. The principal islets appear to be a good source of tissue for further work on somatostatin.
Glucagon levels in pancreatic extracts and plasma of the lizard
Authors: Rhoten William B. 
Published: February 2005

AbstractLevels of glucagon in the splenic pancreas and in plasma of the lizard Anolis carolinesis were estimated by radioimmunoassay. The splenic pancreas of Anolis has a glucagon concentration nearly a 1000 times greater, on a weight basis, than that of the mammalian pancreas. Glucagon‐like immunoreactivity (GLI) of anolian plasma varied over a wide range, but relative to mammals the GLI levels were inappropriately elevated for the concentration of plasma glucose. The anole may prove valuable in studies on the regulation of glucagon secretion, particularly as related to alpha cell function in the diabetic state.
Light and electron microscopic localization of acetylcholinesterase activity in the rat renal nerves
Authors: Barajas Luciano , Wang Patricia , De Santis Steve 
Published: February 2005

AbstractAcetylcholinesterase activity is shown in the renal nerves of the rat with the technique of Karnovsky and Roots. By light microscopy, the acetylcholinesterase‐positive nerves are seen in association with blood vessels, including the glomerular arterioles, and occasionally with renal tubules. By electron microscopy the precipitate appears extracellularly around axons and varicosities. DFP inhibits the deposition of precipitate. Previous demonstration by serial section electron microscopy in the rat revealed that all nerves around the glomerular arterioles contain small dense‐cored vesicles characteristic of adrenergic nerves, indicating that the acetylcholinesterase‐positive nerves demonstrated here are likely to be adrenergic nerves containing acetylcholinesterase.
Endothelial DNA synthesis in the microvasculature of rat skin during the hair growth cycle
Authors: Sholley Milton M. , Cotran Ramzi S. 
Published: February 2005

AbstractEarlier studies of the vascular patterns around hair follicles revealed that actively growing follicles have an extensive microvasculature relative to that around quiescent follicles. In order to determine whether the establishment of the active perifollicular vascular pattern involves replication of endothelial and perivascular cells, we studied the 3H‐thymidine labeling indices of these cells in autoradiographs of rat skin from regions containing either actively growing follicles or recently inactive follicles. In skin containing inactive follicles, the endothelial labeling index was 0.22%, a figure similar to those reported for the endothelium of small blood vessels in several other non‐stimulated adult tissues. However, skin containing actively growing follicles displayed an endothelial labeling index of 2.35%. The labeling indices of perivascular cells paralleled those of the endothelial cells. Thus, endothelial and perivascular cells in vessels associated with actively growing follicles undergo significantly more DNA synthesis than those in vessels associated with inactive follicles. Replication of these cells apparently contributes to the extension of the microvascular network around growing follicles.
The binding of calcium within the Golgi saccules of the rat odontoblast
Authors: Reith Edward J. 
Published: February 2005

AbstractOdontoblasts of developing rat molar teeth were treated with OsO4‐pyroantimonate to ascertain the localization of calcium. In addition, some tooth germs were incubated in solutions which were intended to allow for the escape of diffusible ions prior to fixation in OsO4‐pyroantimonate. In tissues treated directly with OsO4‐pyroantimonate, antimonate reaction product was found chiefly in abacus bodies and secretory granules of the Golgi region and in secretory granules in the distal pole of the cell. Lesser amounts of reaction product were found in the extracellular space, mitochondria, nucleus and generally throughout the cell. Tissues pre‐treated to allow for the escape of diffusible ions showed reaction product, identified as containing calcium, only in the abacus bodies and secretory granules.These results are considered to reflect the binding of calcium within the Golgi apparatus of the odontoblast. Moreover, since it has been shown by others that the abacus bodies and secretory granules contain collagen precursor, it is suggested that the collagen precursor is being seeded with calcium within the Golgi apparatus and that this intracellular calcium binding will play a role in facilitating the major wave of extracellular mineralization of the dentin which is to follow.
Stability of the intra‐epithelial component of the blood‐testis barrier in epinephrine‐induced testicular degeneration in Syrian hamsters
Authors: Gravis C. J. , Chen I. , Yates R. D. 
Published: February 2005

AbstractAdult male Syrian hamsters were given daily intraperitoneal injections of epinephrine (1.0 mg/kg) and papaverine, a vasodilator, (60 mg/kg) for a period of ten days. After the treatment period, lanthanum and horseradish peroxidase tracer studies were used to examine the intra‐epithelial component of the blood‐testis barrier. Degenerating tubules often exhibited only Sertoli cells and spermatogonia, or Sertoli cells alone. Sertoli cell processes in the degenerating tubules often arched out from the main cell body to make contact with other Sertoli cell processes, forming a series of vacuole‐like spaces in the germinal epithelium, adluminal to the Sertoli‐Sertoli junctions. At the site of contact between these arching Sertoli cell processes one to eight tight junctions had formed, with hexagonal arrays of Sertoli cell cytoplasmic filaments located immediately adjacent to these junctions. Cisternae of the Sertoli cell endoplasmic reticulum lay deep to the layer of cytoplasmic filaments. It appeared that these junctions had originated after the expulsion of the germinal elements of the seminiferous epithelium. Penetration of the tracers in the degenerating seminiferous tubules was prevented by what appeared to be normal Sertoli‐Sertoli junctions located between apposed Sertoli cells, adluminal to the remaining spermatogonia when these resisted degeneration, or just adluminal to the basal lamina in those tubules in which spermatogonia were absent.
Absorption from the peritoneal cavity: Sem study of the mesothelium covering the peritoneal surface of the muscular portion of the diaphragm
Authors: Tsilibary Effy C. , Wissig Steven L. 
Published: February 2005

AbstractColored tracers, injected intraperitoneally in mice, are taken up by diaphragmatic lymphatics, outlining their large, terminal cisterns, the so‐called lacunae. The lacunae occur exclusively on the muscular portion of the diaphragm. The mesothelium covering non‐lacunar and lacunar areas of the muscular portion was examined with the SEM. Mesothelial cells overlying non‐lacunar areas are extremely flat, and their boundaries are indistinct. Mesothelial cells overlying lacunae protrude towards the lumen of the peritoneal cavity and have distinct outlines. There are openings or stomata, 4‐12 μm in diameter, between them. Some of the stomata overlie a deep pit; others overlie a shallower pit in which the surface of another cell can be seen beneath the opening. It seems likely that the bulk of the fluid draining from the peritoneal cavity passes through these stomata into underlying lymphatic lacunae.
Ultrastructural identification of the Sertoli cell in the testis of the northern pike, Esox lucius
Authors: Grier H. J. , Linton J. R. 
Published: February 2005

AbstractIdentification of the intralobular Sertoli cell in the testis of Esox lucius is based upon residual body phagocytosis. Formerly, this lipid‐containing cell type was referred to as the “lobule boundary cell” and erroneously believed to be homologous to the interstitial Leydig cell.
Morphology of the intrarenal lymphatic system. Capsular and hilar communications
Authors: Holmes Michael J. , O'Morchoe Patricia J. , O'Morchoe Charles C. C. 
Published: February 2005

AbstractRecent functional evidence has indicated that ureteric obstruction for three or more days in dogs causes a diversion of renal lymph from the hilar to the capsular system. The present study was concerned with the structural correlate of this functional evidence, having special reference to communications between the two systems. Within three days of ureteric occlusion the capsular lymphatic system became dilated. On histological examination two types of tributaries were found. One (termed a perforating lymphatic) served as a primary pathway for superficial cortical lymph from the subcapsular plexus, and penetrated the capsule either alone or in company with a small vein. The other (termed a communicating lymphatic) was closely associated with the occasional penerating interlobular blood vessel which traversed the capsule to ramify in the perirenal tissue. Approximately 60% of the penetrating arteries in eight dog kidneys had associated communicating lymphatics. On the renal surface the perforating and communicating lymphatics formed the primary collecting vessels of the capsular system. Within the renal substance the communicating lymphatics were directly continuous with lymphatics which surrounded the interlobular blood vessels and which have been shown to drain into the hilar network. Thus the communicating lymphatics formed direct connections between the hilar and capsular systems. It was concluded that these communications, although dilated by hydronephrosis, existed under control conditions. Functionally they are probably of importance only under special circumstances when intrarenal lymph may be diverted from one to the other system.
The fine structure of blood vessels of the telencephalic germinal matrix in the human fetus
Authors: Povlishock John T. , Martinez A. Julio , Moossy John 
Published: February 2005

AbstractBlood vessels of the human telencephalic germinal matrix during the tenth through the twenty‐second week of gestation have been examined by light and electron microscopy. In all fetuses studied the ependymal and sub‐ependymal zones of the germinal matrix have a prominent vascular network. During the tenth and twelfth weeks of gestation, the endothelial cells are plump and display numerous organelles, junctional complexes, conspicuous luminal microvilli and stub‐like abluminal projections. Coated and micropinocytotic vesicles were found both in the cytoplasm and on luminal and abluminal surfaces. In endothelial cells intracytoplasmic, membrane‐limited, rod‐shaped bodies were frequently observed. These bodies have been linked to endothelial thromboplastic and clotting activities and related to abnormal clotting status. Their role in the pathogenesis of subependymal germinal matrix hemorrhage in premature infants remains unknown. Pericytes apposing the endothelial cells were recognized in all gestational periods. The endothelial basal lamina and astrocytic end‐feet are ill defined, and the extracellular space is pronounced. By the fifteenth and seventeenth weeks of gestation the endothelial cells are still large and now possess more numerous luminal microvilli and abluminal projections. At this stage the pericytes, basal lamina and astrocytic end‐feet are all well developed, resulting in a decrease in the surrounding extracellular space. By the twenty‐second week the endothelial cells possess few luminal and abluminal projections and the associated basal lamina, glia, pericytes and extracellular compartment appear mature. The relationship of the germinal matrix vasculature to the pathogenesis of subependymal hemorrhage is discussed.
Fine structure of the monkey epididymis
Authors: Ramos Angel S. , Dym Martin 
Published: February 2005

AbstractThe monkey epididymis was subdivided into four regions: initial segment (continous with the ductuli efferentes), head, body and tail. The initial segment possesses a very tall columnar epithelium (108 ± 4 μm). Epithelial height in the head, body and tail is diminished to 81 ± 5 μm, 69 ± 2 μm, and 50 ± 5 μm, respectively. The pseudostratified epithelium is composed of four main cell types: principal, apical and basal epithelial cells, and intraepithelial lymphocytes. Occasional macrophages are also found in the epithelium. The tall, narrow, columnar principal cells demonstrate morphological features characteristic of absorption and secretion. An unusual feature, apparently unique to the primate, is the presence of deep invaginations of the apical cytoplasm which contain membrane‐bounded vacuoles. Similar, but larger vacuoles are present among the stereocilia and in the tubular lumen. Large clusters of mitochondria and electron‐dense membrane‐bounded granules characterize the infranuclear region of the cytoplasm. Principal cells are studded with closely aligned stereocilia. Their nuclei are spindle‐shaped in the initial segment and first portion of the head region, but become highly infolded in the distal head, body and tail portions. The apical or mitochondrion‐rich cells possess a cytoplasm which extends from the base of the epithelium to the tubular lumen. Basal cells contain few organelles and are found throughout the length of the duct. Arterioles and capillaries appear to penetrate directly into the epithelium from the underlying connective tissue; however, the basal lamina of the epididymal duct always intervenes between the endothelium of the blood vessels and the epithelial cells. Several of the above observations have not been noted in rodents and other mammalian species and may be unique to the primate.
Effects of clomiphene on the structure of the testis, epididymis and sex accessory glands of the rat
Authors: Flickinger Charles J. 
Published: February 2005

AbstractYoung adult male rats were treated with clomiphene citrate, a non‐steroidal inhibitor of gonadotropin release in the rat. They were administered 2.5, 3.5, or 5.0 mg/100g/day for intervals up to 12 weeks. The weights of the sex accessory glands were less than those of control rats, and decreased with increasing dose and length of treatment. At the longer intervals, the weights of the testis and epididymis were also less than those of control animals. Microscopic alterations in the testis included a scarcity or even absence of late spermatids, the presence of necrotic cap‐phase spermatids, and accumulation of lipid droplets and large lysosome‐like structures in Sertoli cells. In rats treated for the longest interval, 12 weeks, testicular changes were even more extensive; degenerating primary spermatocytes were observed, and in one rat germ cells were virtually completely absent and the seminiferous tubules were occupied by Sertoli cells. The Leydig cells of treated animals were smaller than those of normal or control rats. Sperm were absent from the lumen of the caput epididymidis in most specimens. Although the epithelium of the caput appeared reduced in height in some samples, ultrastructural changes in cellular organelles were not detected. In most specimens of the cauda epididymidis, the lumen was small, irregularly shaped, and lacking in sperm. Light cells were prominent in the epithelium by virtue of their content of many apical vacuoles and dense granules. In some specimens of the distal cauda epididymidis, the duct had a circular profile and the lumen contained round cells and debris. The seminal vesicle and the ventral prostate were greatly suppressed. The normally tall columnar epithelia were reduced to a low columnar or cuboidal shape. Especially at the longer treatment intervals, the normally abundant rough endoplasmic reticulum was sparse, and in some samples secretory vacuoles were absent. The possible mechanism of production of these morphological changes is discussed, and the results are compared with those following treatment with other antifertility agents, including cyproterone acetate, a progestin, and a progestin‐androgen regimen.