bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preovulatory changes in cumulus‐oocyte complex of the hamster
Authors: Leibfried M. Lorraine , First Neal L. 
Published: February 2005

AbstractAn orderly series of associations was found between the cumulus and the stages of nuclear development in the hamster oocyte as the oocytecumulus complex underwent preovulatory maturation. Ten hours prior to ovulation meiotic resumption was first seen in the oocyte. The onset of cumulus dissociation with corresponding morphological changes in cumulus cells was observed eight hours prior to ovulation. Completion of the first meiotic division in the oocyte and full cumulus dissociation occurred 2 hours prior to ovulation. Cumulus dissociation was found to occur only in vesicular follicles destined to ovulate and not in follicles undergoing atresia. Cells with large vacuolar inclusions with distorted, hyperchromatic nuclei were found in the maturing cumulus.
Development of harderian gland during metamorphosis in anurans
Authors: Shirama Kazuhiko , Kikuyama Sakae , Takeo Yuji , Shimizu Kiyoshi , Maekawa Kyutaro 
Published: February 2005

AbstractDevelopment of Harderian gland of larvae of Rana japonica, Bufo bufo japonicus, and Xenopus laevis was studied. In the adult animals, welldeveloped Harderian glands were invariably present in the orbit. In Rana and Bufo, the gland first appeared at late prometamorphic stage and in Xenopus it appeared around climax stage.In thyroidectomized tadpoles of Bufo and Rana, the Harderian gland was induced by thyrozine. In hypophysectomized tadpoles of Bufo the gland developed when they were treated with thyrozine or TSH.
Development of ultrastructural heterogeneity among hepatocytes in the mouse
Authors: Asada‐Kubota Mari , Kanai Kazuo , Kanamura Shinsuke 
Published: February 2005

AbstractUltrastructural stereological analyses of periportal and centrilobular hepatocytes of newborn, 5‐ and 10‐day‐old, and adult male ddY mice were carried out to study the postnatal development of the morphologic heterogeneity among hepatocytes. In newborn animals, the periportal and centrilobular cells did not differ in the volume densities of the smooth and rough endoplasmic reticulum; in the volume and numerical densities of the mitochondria, lysosomes, peroxisomes, and lipid droplets; or in the shape (the axial ratio) of the mitochondria. In 5‐day‐old animals, the volume densities of the mitochondria and rough endoplasmic reticulum were greater in periportal cells than centrilobular cells, and the volume density of the smooth endoplasmic reticulum was greater in centrilobular cells than periportal cells. In 10‐day‐old animals, a further difference was seen in the numerical density of the mitochondria, which was greater in centribular cells than periportal cells. Adult hepatocytes showed also a difference in the axial ratio of the mitochondria, which was greater in centrilobular than periportal cells; there was no difference in the volume density of the rough endoplasmic reticulum. When the data were expressed as volume and number per hepatocyte, the patterns of sublobular distributions of these organelles differed from the patterns seen in the volume and numerical density data, mainly in adult animals. This difference was caused by the marked increase in hepatocyte volume between 10 days of age and adulthood, especially in centrilobular cells.The results show that, in general, the ultrastructural heterogeneity among hepatocytes, evident in adult animals, is not present in newborn animals but arises during postnatal development, and suggest the occurrence of a lobular gradient in postnatal development of hepatocyte functions.
Cellular kinetics of the bone remodeling sequence in the rat
Authors: Van Phuc Tran , Vignery Agnes , Baron Roland 
Published: February 2005

AbstractThe kinetics of the bone remodeling sequence in the rat has been studied using a system in which well‐synchronized remodeling units were induced along the periosteum of rat mandibles. Remodeling of the periosteal surface of the mandibles was induced according to Tran Van (1979) by extraction of the opposing row of teeth; namely, the right maxillary molars were extracted under light ether anesthesia, therefore allowing the right mandibular molars to egress; this, in turn, induced a wave of remodeling activity on the buccal side of the periosteal surface of the alveolar bone. The quantification of the different cellular activities involved in bone remodeling has been performed up to 16 days after induction. This allowed us to demonstrate the sequential activity of the different cell types involved in bone remodeling, to study the cellular kinetics of this sequence of events, and to directly measure the duration of each phase of the bone remodeling sequence. A single wave of osteoclasts appeared 3 days after induction, reached a peak at 4–5 days, and then decreased sharply. This was followed by a single wave of mononuclear cells (Baron et al., 1980) within remodeling sites during the reversal phase; they appeared 4 days after induction, reached a peak by day 7, and then decreased sharply. This reversal activity was then followed by osteoblasts forming new bone on top of a reversal cement line in the remodeling sites, starting 6 days after induction and increasing until the end of the experiment. In addition, the synchronization of the system used in this study allowed direct measurement of the duration of the successive steps of the remodeling sequence. The directly measured values have then been compared to previous data calculated from other systems.
Formation of the outer dense fibers during spermiogenesis in the rat
Authors: Irons Margaret J. , Clermont Yves 
Published: February 2005

AbstractThe morphogenesis of the outer dense fibers (ODF) in rat spermatids has been studied by electron microscopy, and the synthesis and incorporation of proteins into the ODF during this process have been followed by radioautography using 3H‐proline and 3H‐cystine as precursors for ODF proteins. In the first phase (steps 8–14), nine very fine fibers termed anlagen of the ODF develop in association with the microtubule doublets. These first appear along the most proximal portion of the axoneme in step 8 of spermiogenesis; during steps 9–14 they gradually increase in length in a proximal‐to‐distal direction, being first observable along the forming midpiece and later along the principal piece as well. In the second phase (steps 15–16), the rudimentary fibers suddenly increase in diameter, with the most dramatic growth occurring in step 16, and assume a close resemblance to the mature ODF. This striking transformation, which appears to result from simultaneous deposition of electron‐dense material along the length of anlagen of the ODF, coincides with a period of rapid incorporation of 3H‐proline and 3H‐cystine‐containing proteins, which become permanent structural components of the ODF. These proteins, which comprise the bulk of the ODF, are synthesized in the cytoplasm of spermatids during the acrosome and early maturation phases. In the final phase (steps 17–19) the fibers continue to enlarge very slowly, assuming their definitive form in step 19 of spermiogenesis. Thus formation of the ODF in the rat is a lengthy multistep procedure, requiring from step 8–19 of spermiogenesis and utilizing proteins synthesized throughout most of this period.
Ultrastructure of turkey hepatocytes
Authors: Bhatnagar M. K. , Singh A. 
Published: February 2005

AbstractHepatocytes of normal male and female turkey livers perfused in situ with a fixative containing 4% glutaraldehyde in 0.05 M phosphate buffer (pH 7.4) were examined by electron microscopy. The hepatocytes, arranged in two‐cell‐layered plates, were polygonal and had three spatially different surfaces. The vascular surface was formed by microvilli, which at times projected into the sinusoids past the space of Disse. The interhepatocytic surfaces were closely applied and contained an occasional gap junction. The biliary surface participated in bile canaliculus formation and had short, regular microvilli. Tight junctions and adherens junctions were close to the canalicular lumen. The hepatocyte nucleus was located towards the vascular pole. The cytoplasm of hepatocytes of the females had many lipid droplets. The pleomorphic mitochondria, with relatively electron dense matrices were surrounded by one or, rarely, two profiles of flattened rER. Golgi complex was often observed in the vicinity of the nucleus, whereas the centrioles were located in the pericanalicular area of the biliary pole, which was rich in microtubules. These microtubules were extremely long, at times covering a substantial distance between the Golgi complex and bile canaliculi; microtubules occasionally formed bundles near the biliary pole. Small vesicles in close proximity of the microtubules were frequently observed. The spatial relationship between Golgi complex, microtubules, vesicles, and centrioles at the biliary pole of the hepatocyte appears to support the concept that the bile secretory mechanism in avian hepatocytes may involve a centrioles‐microtubules‐vesicles‐Golgi complex system.
Early myelin formation and glial cell development in the human spinal cord
Authors: Okado Nobuo 
Published: February 2005

AbstractIn order to identify the onset of myelination as well as to clarify the development of glial cells in human cervical spinal cord 21 embryos and fetuses ranging from 5 weeks of ovulation age (16 mm in crown‐rump length) to 13 weeks (110 mm) were examined with the light and electron microscope. The first appearance of definite myelinated fibers occurred in the lateral portion of the ventral marginal layer of a 66‐mm (10‐week) fetus. These nascent myelinated axons were always of larger diameter than unmyelinated axons. Although they occurred infrequently, there were, nevertheless, degenerative changes observed in some of these first myelinated axons in the 66‐mm fetus. By this time glial cells in the marginal layer rapidly increased in number and substantial differentiation had occurred. Young oligodendrocytes are considered as the only myelin‐forming cells in the human spinal cord.
DNA content, mitotic activity, and incorporation of tritiated thymidine in the developing inner ear of the rat
Authors: Khan Khalid M. , Marovitz William. F. 
Published: February 2005

AbstractThe rat inner ear is ectodermally derived from a region adjacent to the developing hindbrain. Beginning on day 8 of a 22‐day gestational period, this zone of ectoderm first forms the otic placode, then the otocyst, and ultimately the definitive membranous labyrinth. This report provides an estimation of total DNA content of the developing inner ear, and hence an estimation of the total number of cells that comprise the inner ear at each developmental stage. The incorporation of 3H‐thymidine indicates that most cells of the inner ear undergo DNA synthetic activity during gestational days 13 to 15. Radioautographic observations indicate a zone of DNA synthetic activity at the base of the outpocketing cochlear duct during early development. At the later stages of development, DNA synthesis is restricted to the cristae ampullares of the semicircular canals and the maculae of the utricle and the saccule. In contradistinction to the findings of other investigators, the statoacoustic ganglion complex undergoes terminal mitosis during gestational days 17 and 18. The gestational period between days 13 and 15 may prove to be a critical stage in normal otic development. The normal values of total DNA content and the number of cells that comprise the inner ear during development, established by these methods, can be compared with pathologic inner ears to provide quantitative means of assessing the damage in malformed inner ears. These values also form the baseline for future experimental studies of inner ear development.
Development of the glycogen body through the whole length of the chick spinal cord
Authors: Uehara Masato , Ueshima Toshihiko 
Published: February 2005

AbstractThe development of the glycogen body was studied throughout the entire length of the chick spinal cord. The glycogen body cells first appeared at stage 31 on each side of the ependymal septum from the 26th to 28th segments of the spinal cord. By stage 34 the paired primordia of the glycogen body extended from the 25th to 29th segments. In the middle of the structure described classically as the glycogen body (i.e., the portion restricted to the level of the spinal nerves 26–29), these primordia were fused dorsally at stage 34 and had fused completely by stage 37. The paired primordia extended from the cervical enlargement to the lumbosacral portion of the spinal cord by stage 36 and extended to the upper cervical segments by stage 38. They were totally fused throughout the entire length of the spinal cord by stage 42. The glycogen containing cells, in the classical glycogen body level, appeared ventrolateral to the central canal at stage 35. Thereafter they increased in number and glycogen content, and extended rostrad and caudad from the classical glycogen body level. They fused to each other and then fused with the glycogen body. Therefore, the bilateral clusters of the glycogen‐containing cells are considered as the ventral paired primordia of the glycogen body. The development of the glycogen body is essentially the same pattern as in the classical glycogen body throughout the entire length of the spinal cord.
Aspects of renal vascular organization and early vascular tubular relations of the marsupial Isoodon obesulus
Authors: Burger C. H. , Cross R. B. 
Published: February 2005

AbstractRenal vascular tubular relationships were studied in the marsupial Isoodon obesulus (the common brown bandicoot). The microcirculation was filled with colored silicone rubber by intra‐arterial injection of the intact kidney. Nephrons were defined by the injection of silicone rubber of a contrasting color into the space of Bowman's capsule in thick, cleared slices of renal tissue. The details of the vascular tubular relationship in this marsupial are strikingly similar to relationships previously described in true mammalian kidneys. An unusual feature is a wide (600μ) glomerulus‐free zone at the outer cortex. This zone contains the proximal and distal convoluted tubules of the most superficial cortical nephrons and is perfused by efferent vessels from glomeruli in superficial strata of the cortex.
Circadian ultrastructural changes in rat gastric parietal cells under altered feeding regimens: A morphometric study
Authors: Jacobs Danielle M. , Sturtevant Ruthann P. 
Published: February 2005

AbstractThe ultrastructure of rat gastric parietal cells was studied at six timepoints of the 24‐hour day. The rats, maintained on a 12 hour: 12 hour light‐dark regimen, had been subjected to either a 40‐hour fast or to a 4‐hour mid‐light restricted feeding period. At each time point, the volume density (Vv) of secretory canaliculi, surface density (Sv) of microvesicles and RER, and the numerical density (Nv) of multivesicular bodies were determined in cells of the neck and base of glands. Circadian variation of the four variables was suggested in both experiments. Canalicular and microvesicular measurements suggested that a rhythm in gastric acid secretion may persist during fasting; a peak and trough, respectively, occurred in the late dark phase, as in our previous report on ad libitum‐fed rats. Restriction of feeding to that which is normally the rat's resting phase caused an apparent 180 degree phase‐shift in the rhythm. The data suggested, however, that additional factors may have influenced the cellular activity pattern. At all timepoints in both experiments, cells of the neck of glands had higher RER and canalicular values than did cells of the base of glands. This suggests that parietal cells in glandular necks may be more active than those farther removed from the stomach lumen. There was no correlation between the Nv of multivesicular bodies and glandular location of the cells.
A cellular investment of bone marrow
Authors: Menton D. N. , Simmons D. J. , Orr B. Y. , Plurad S. B. 
Published: February 2005

AbstractWe describe a method for cleanly separating; the cell layers at the bone‐marrow interface, which reveals that the myeloid tissue is invested by an epithelial‐like layer of specialized squamous cells we call the marrow sac. The scanning electron microscope showed that the sac was fenestrated and that some of its cells pass as perivascular elements with the marrow capillaries that penetrate the bony cortex. The transmission electron microscope (TEM) showed that the cells comprising the marrow sac are less than 0.1 μm thick, overlap at their margins without specialized cell junctions, and are more electron dense than the reticular or fibroblastic cells of the marrow stroma. The fenestrations in the sac were intercellular and were usually occupied by cells having an ultrastructure compatible with an osteoprogenitor cell (OPC) lineage. The observation of a close proximity between the cells of the marrow sac and the osteogenic cells that line the endosteal surfaces of bone suggest that the sac cells, along with the OPCs of the superficial marrow stroma, should be included in any morphological or functional definition of an endosteum.
Tanycytes in long‐term ovariectomized ewes treated with estrogen exhibit ultrastructural features associated with increased cellular activity
Authors: Coates Penelope W. , Davis Steven L. 
Published: February 2005

AbstractEpendymal tanycytes on the floor of the third ventricle of longterm ovariectomized (OVX) female sheep (ewes) and OVX ewes treated with 17β‐estradiol (E2β) were investigated with scanning and transmission electron microscopy (SEM and TEM) for evidence of differences in ultrastructure. Plasma concentrations of luteinizing hormone (LH) in the same ewes that were analyzed ultrastructurally were 45.1 ± 28.7 ng/ml in the nontreated OVX group, and 2.2 ± 1.3 ng/ml in the OVX + E2β group, confirming the widely reported negative feedback effect of estrogen on LH. With SEM, the most prominent difference between groups was that tanycytes on the floor of the third ventricle in OVX ewes had very few surface membrane modifications, particularly microvilli, and appeared relatively bare‐surfaced compared to those from the estrogen‐treated group. Tissues from estrogen‐treated OVX ewes were, for the most part, covered with a fuzzy nap of delicate microvilli. Transmission electron microscopy confirmed and extended this impression. With TEM, tanycytes in E2β‐treated ewes exhibited not only a more luxurious display of microvilli but also a much richer complement of welldeveloped organelles including rough endoplasmic reticulum, ribosomes, Golgi complexes, microtubules, and filaments than tanycytes in OVX alone ewes. Collectively, the fine structural data indicates a positive correlation between tanycytes displaying well‐developed features associated with heightened cellular activity – synthesis, secretion and/or absorption – and the presence of estrogen.
Evolution of sertoli cell processes invading the cytoplasm of rat spermatids
Authors: Morales C. , Clermont Y. 
Published: February 2005

AbstractSertoli cell processes invaginating the cytoplasm of rat spermatids were investigated in thin or thick sections stained respectively with ferrocyanide‐reduced osmium (Karnovsky, 1971) and the Ur‐Pb‐Cu metallic impregnation method (Thiéry and Rambourg, 1976). Two types of Sertoli cell processes were observed: Some, seen in steps, 11–15 of spermiogenesis, were associated with a tight network of ER cisternae located within the spermatid cytoplasm subjacent to the plasma membrane facing the Sertoli cell process; others, seen from step 11 until the end of spermiogenesis, were not associated with such a spermatid subsurface ER network. Following their formation, the ER‐associated Sertoli cell processes were cleaved into double‐walled vesicles. Concomitantly, the enclosed Sertoli cell cytoplasm underwent autolysis followed by the dissolution of the Sertoli cell plasma membrane leaving within the spermatid cytoplasm many empty‐looking vacuoles delimited only by the plasma membrane of the spermatid. Thereafter, i.e., in steps 15 and 16 of spermiogenesis, these vacuoles clustered, and with the collapse of the vacuoles they gave rise to a single compact mass of interlaced ER cisternae and small vacuoles. With the dissolution of ER cisternae, in step 18, this mass was finally dispersed. These observations suggested that the ER‐associated Sertoli cell processes may constitute a pathway for the delivery of material from the Sertoli cells into spermatids. In contrast, the Sertoli cell processes not associated with a network of ER cisternae did not show cleavage or autolysis and appear to be involved mainly in holding the cytoplasm of the spermatid in place.
The cytoskeleton of human polymorphonuclear leukocytes: Phagocytosis and degranulation
Authors: Ryder Mark I. , Niederman Richard , Taggart Edward J. 
Published: February 2005

AbstractCurrent evidence indicates that polymorphonuclear leukocyte (PMN) chemotaxis and phagocytosis are effected by an actin–myosin contractile system. However, the structural relationship of the contractile cytoskeleton to cell motility is still in question. In addition, while evidence suggests that microtubules are responsible for orientation during chemotaxis, the role of microtubules in degranulation is unresolved. To determine the organizational relationship between these cytoskeletal elements and phagocytosis, we examined whole‐mount preparations of PMNs engulfing bacteria. These preparations were examined in the transmission electron microscope (EM) and photographed as stereo pairs. Two important observations were made. First, there was an increased density of cytoskeletal elements in the pseudopod surrounding bacteria. Second, microtubule elements were intimately associated with lysosomal granules, vesicles, and phagosomes. Lysosomal granules and vesicles aligned along microtubules and clustered around phagosomes. This suggests that the microtubules may provide a tracking mechanism whereby lysosomes are specifically parceled out to phagocytic vacuoles. These results also suggest that phagocytosis and degranulation may involve different effector mechanisms.
Substructure of granules from serous cells of porcine tracheal submucosal glands
Authors: Turek John J. , Sheares Bradley T. , Carlson Don M. 
Published: February 2005

AbstractThe ultrastructure of serous cells from porcine tracheal submucosal glands was studied by conventional transmission electron microscopy (TEM), and by cytochemical methods to stain for complex carbohydrates. In tissue fixed and processed for TEM, and stained with uranyl acetate and lead citrate, the condensing granules of serous cells occasionally possessed a hexagonal and sometimes a lamellar substructure. Tissue fixed in paraformaldehyde‐glutaraldehyde and stained with periodic acid‐thiocarbohydrazide‐silver proteinate (PTS) or with phosphotungstic acid (PTA) showed secretory granules stained for complex carbohydrates and revealed a substructure similar to that noted in the condensing granules. The dark staining substructure revealed by either the PTS or the PTA technique appeared to correspond to electron‐lucent areas observed in the condensing granules by conventional TEM. The PTS staining probably demonstrated the presence of neutral glycoprotein, since the serous‐cell granules did not react with a dialyzed iron stain for acidic glycoproteins. Treatment of periodic acid oxidized thin sections with pronase or pepsin prior to thiocarbohydrazide and silver proteinate treatment decreased the intensity of the PTS staining, but did not digest away any components of the granules. The substructure revealed by the carbohydrate stains may be a reflection of the mechanism of packaging or the macromolecular structure of the glycoproteins in the serous‐cell granules.