bluuebunny/crossref_metadata_2025_split huggingface dataset:
Distribution of glycogen in the floor plate of the chick spinal cord during development
Authors: Uehara Masato , Ueshima Toshihiko 
Published: February 2005

AbstractThe present study was undertaken to characterize the structural changes and the glycogen distribution in the floor plate of the developing chick spinal cord.The floor plate consisted of ventricular zone by stage 19 (staged according to Hamburger and Hamilton, 1951). The marginal zone of this plate could be distinguished as a narrow border at stage 21. It increased progressively in thickness and was the same thickness as the ventricular zone at stage 26. It increased again in thickness from stage 38 onward.Glycogen appeared and subsequently disappeared in the floor plate of the chick spinal cord during development. Little, if any, glycogen appeared in the midportion of the floor plate at stage 19. The floor plate was weakly glycogen positive from the cervical through lumbosacral segments at stage 21. In the floor plate of the lumbosacral enlargement the glycogen staining was the highest and was maximal through stages 34–37. The floor plate of the cervical and thoracic segments except for the cervical enlargement continue to have low concentrations of glycogen. The glycogen staining of the floor plate began to decrease from stage 38, and at the same time neuroglial cells began to migrate into the marginal zone of the floor plate, later than in other regions of the cord. The glycogen staining in the floor plate was barely detectable at stage 40.The accumulation of the glycogen granules in the floor plate was found only in the radial glial cells.
The microscopic structure of fibrous articular surfaces: A review
Authors: Wilson N. H. F. , Gardner D. L. 
Published: February 2005

AbstractThe present knowledge of the microscopic structure of fibrous articulating surface is reviewed. The influence of dissection, postmortem change, fixation, and dehydration on the microscopic appearances of these surfaces is considered. The results of those studies of surface morphology that investigate intact, supported specimens and that are controlled by surveys of fresh, unfixed, or frozen material are advantageous. New information on the effects of alterations in intermaxillary relationship on the morphology of fibrous articulating surfaces is presented. There is need for further work in this field of research.
Locomotion and scanning electron microscopic observations of primordial germ cells from the embryonic chick blood in vitro
Authors: Kuwana Takashi , Fujimoto Toyoaki 
Published: February 2005

AbstractThe locomotion of chick primordial germ cells (PGCs) in vitro was observed using 16‐mm time‐lapse microcinematography and 35‐mm timelapse film. The PGCs isolated from circulating blood of stage 14 to 16 embryos (Hamburger and Hamilton, 1951) were cultured on a substrate of mesenchymal feeder cells obtained from the dorsal mesentery of stage 40 embryos, using modified medium 199 containing 10% fetal calf serum. The PGCs were found to move actively and to show a tendency to move along the longer axis of the underlying cells. The velocity of PGC locomotion averaged 26 μm/hr and reached 58 μm/hr as a maximum.After observation, the PGCs were processed for scanning electron microscopy. They had a considerable number of microvilli about 0.2 μm in thickness and some cytoplasmic blebs on their surfaces. It was observed that the PGCs in the migrating phase adhered to the substrate with its filopodia only at the leading edge, while a large part of the cell appeared to be apart from the substrate.
Changes in the secretory acinar cells of the rat parotid gland during aging
Authors: Kim Sun‐Kee 
Published: February 2005

AbstractThe secretory acinar cells of parotid glands from rats of varying ages have been examined by electron microscopy to determine what age‐related changes occur in these cells. The most prominent change noted in these cells is the progressive increase in the amount of lipofuscin granules with age. Lipofuscin granules are membrane‐bound structures consisting of lipids, other subcomponents, and a matrix. In addition, these cells contain lipid droplets that are not associated with any other components and tend to accumulate at the base of the cells in older rats. Also, many acinar cells in the glands of old rats contain altered secretory granules which appear to be in the process of degeneration. The accumulation of lipid and degenerating secretory granules appears to be related to the reduced level of cellular secretory activity in the glands of older rats. It is possible that these two types of inclusions contribute to the formation of lipofuscin granules. Lipofuscin and degenerating secretory granules are associated with acid phosphatase, which is demonstrated cytochemically, indicating that these granules are lysosomal structures.
An immunocytochemical study of the pancreatic islet system of the channel catfish
Authors: McNeill Daniel L. , Brinn Jack E. , Fletcher Donald J. 
Published: February 2005

AbstractThe endocrine pancreas of the channel catfish is segregated into a large primary islet and numerous smaller secondary islets. In view of cell distribution differences in mammalian islets of ventral and dorsal primordia, we have determined the percentage volumes of insulin‐, glucagon‐, and somatostatin‐containing cells in primary and secondary catfish islets to ascertain if these islets correlated with those derived from ventral and dorsal primordia in mammals. Islets were immunocytochemically stained using antisera to anglerfish insulin, porcine glucagon, and synthetic somatostatin and volume densities were quantified on light micrographs by point‐counting procedures. In both primary and secondary islets the insulin‐, glucagon‐, and somatostatin‐containing cells comprised approximately 32%, 23%, and 38% of the endocrine cell volumes, respectively. Therefore, the cell populations did not reflect any embryological differences between the two groups of islets. In this study, the volume densities of insulin‐reactive cells in the primary islet were less than previously reported, and the overall insulin staining was about one‐half of that seen in mammals. The volume density of somatostatin‐reactive cells in primary islets was greater than previously reported. Based on these data, primary and secondary islets of the catfish do not appear to have a similar development to the ventral and dorsal islets of the mammalian system.
Effects of genic substitution at the brown locus on the differentiation of epidermal melanocytes in newborn mouse skin
Authors: Hirobe Tomohisa 
Published: February 2005

AbstractIn the dorsal epidermis of both C57BL/10J (black, BB) and C57BR/cdJ (brown, bb) mice, the number of melanocytes positive to the dopa reaction (melanocyte population) increases from birth to day 3 or 4, and then gradually decreases. However, the number of melanoblasts plus melanocytes positive to the combined dopa‐premelanin reaction (melanoblast‐melanocyte population) remains constant until day 3 or 4 and then decreases in the two strains. Despite the similarity of the developmental dynamics in both black and brown mice, there is a significant difference in the number of differentiated melanocytes. Melanocytes are more numerous and more dopa‐reactive in brown mice than in black. The maximal density of the melanoblast‐melanocyte population on day 3 or 4 does not differ in brown and black mice. Moreover, the maximal density of the melanocyte population in brown epidermis does not differ from that of the melanoblast‐melanocyte population of both brown and black. These results indicate that b allele, when homozygous, enhances the differentiation of epidermal melanoblasts by inducing high tyrosinase activity.
Enrichment of lysozyme‐containing cells from the rabbit endocervix by unit gravity sedimentation
Authors: Chilton Beverly S. , Nicosia Santo V. , Sowinski Janice M. 
Published: February 2005

AbstractLysozyme is a bacteriolytic enzyme component of the secretory granules of endocervical mucous cells. In order to study the subcellular distribution of this enzyme in specific cell populations, endocervical cells from estrous and 5‐day pseudopregnant rabbits were separated by unit gravity sedimentation. The application of this technique to pronase‐dispersed endocervical cells from estrous rabbits resulted in the isolation and enrichment of two mucous cell types that were distinguished morphologically into type I and type II cell populations. Lysozyme was identified in both cell types, using an unlabeled antibody enzyme method, and the degree of staining paralleled the number of mucous granules. In the absence of estrogen dominance in 5‐day pseudopregnant rabbits, there was a 50% reduction in the number of mucous cells with a concomitant reduction in both the number of secretory granules per cell and the intracellular concentration of lysozyme. In the absence of ovarian steroid hormones, i.e., 15–16 weeks after ovariectomy, endocervical cells were devoid of secretory granules and lysozyme staining was negative. Enriched populations of endocervical cells represent a potential experimental model for studying the hormonal role in the regulation of lysozyme synthesis by specific cell populations.
Effect of dexamethasone on the fetal mouse small intestine in organ culture
Authors: Beaulieu J.‐F. , Calvert R. 
Published: February 2005

AbstractThe formation of intestinal villi (organogenesis phase) may be studied in organ culture with a completely synthetic medium in 15‐day fetal mouse duodenal explants. However, in these explants absorptive cells remained poorly differentiated with all the hormones studied except with epidermal growth factor. In order to elucidate the role of hormones and other factors on the maturation of absorptive cells (maturation phase) in the fetal rodent in organ culture, we have taken the explants after the organogenesis phase. We have studied different culture conditions and have found that 17‐day mouse duodenal explants can be cultured during 48 hours with Leibovitz L‐15 medium in a 95% O2‐5% CO2 atmosphere provided that the explants are relatively large (5 × 2 mm). With this method, dexamethasone (Dx) has been shown to have a direct effect on the maturation of the fetal duodenal mucosa. The addition of Dx (300 ng/ml) to the completely synthetic medium (1) improves the morphology of the explants, (2) induces a significant increase in maltase activity in the tissues, and (3) reduces significiantly the labeling index of the duodenal explants after 48 hours of culture. Direct action of Dx on the duodenal mucosa is shown for the first time in organ culture using a completely synthetic medium. This method will permit us to study the effects of other intrinsic and extrinsic factors on the regulation of enzymatic maturation in fetal small intestine.
The neonatal porcine lung: Ultrastructural morphology and postnatal development of the terminal airways and alveolar region
Authors: Winkler Gian C. , Cheville Norman F. 
Published: February 2005

AbstractMorphology and postnatal development of the porcine lung are described in animals ranging in age from newborn through 60 days. Standardized fixation was accomplished by intratracheal instillation of glutaraldehyde under constant pressure. Light microscopic, scanning, and transmission electron microscopic investigations revealed that the porcine lung follows the common architecture of mammalian lungs, but has certain peculiarities as well: intravascular macrophages, ultrastructurally similar to Kupffer cells, are attached to endothelial cells in pulmonary capillaries and are involved in erythrophagocytosis during the first postnatal weeks. Type II pneumocytes of newborn pigs exhibit signs of cell activation, mainly complex nuclear bodies in the cell nuclei. At the same time high levels of 17‐hydroxycorticosteroids are observed in the newborn blood plasma. Terminal airways of the porcine lung are nonalveloarized and are, therefore, of purely conductive function.At birth the porcine lung exhibits a high degree of maturity, and thickwalled primary saccules, as described in newborn rodents, are not seen. Septa appear straight and smooth, owing to rare ramification. Septal buds are discernible, and two capillary networks visible on both sides of septal cross sections are seen. Further subdivision of the airspaces occurs in the first two postnatal weeks. Precociousness and fast postnatal growth of the porcine species are assumed to be the reason of this advanced degree of lung maturity at birth and the following rapid pulmonary development.
The glial cells in the nerve fiber layer of the rat olfactory bulb
Authors: Doucette J. R. 
Published: February 2005

AbstractIn mammals the olfactory receptor neurons are the only ones that are known to undergo continuous cell renewal in the adult animal. This means that the axon of each newly formed neuron must grow into the olfactory bulb to find its appropriate target cell. It is presumed that astrocytes ensheath the olfactory axons as they course through the nerve fiber layer of the bulb even though the cells in question differ ultrastructurally from typical astrocytes. The purpose of the present study was to examine the glial cells in the nerve fiber layer of the rat olfactory bulb in an effort to resolve this apparent discrepancy. Two morphologically distinct types of glial cell were found in the nerve fiber layer. One type, which resembled the typical astrocytes that are present in other areas of the cental nervous system, contained bundles of filaments in an electron‐lucent cytoplasm. These cells also formed endfeet on blood vessels and formed part of the external glial limiting membrane. They did not, however, ensheath the olfactory axons. The cytoplasm of the other type of glial cell was denser than that of typical astrocytes and contained fewer filaments, which were seldom grouped into bundles. These cells also formed part of the glial limiting membrane at the surface of the bulb and were the only ones that ensheathed the olfactory axons. It is concluded that the cell ensheathing the olfactory axons in the nerve fiber layer of the rat olfactory bulb is a morphological variant of the typical astrocyte. One role of the former cell may be to support or encourage the growth of olfactory axons within the central nervous system.
Freeze‐replica study of lipid droplets in the ito cells of rat liver
Authors: Yamamoto Kouta , Ogawa Kazuo 
Published: February 2005

AbstractThe structure of lipid droplets in the Ito cells was studied by the freeze‐replica method in vitamin A‐treated rats. Most lipid droplets were fractured in planes through their lipid contents. Some of them were surrounded by a membrane structure that had intramembranous particles (IMP), which were more numerous on the protoplasmic face than the exoplasmic face. Those with the membrane containing IMP correspond to the membranebounded lipid droplets (lipid droplets surrounded by lysosomes) seen in the electron microscopic observation of conventional thin section preparations. There were no lipid droplets showing concave or convex multilayered structures in the Ito cells from properly fixed livers. Since these multilayered structures were observed only in the materials fixed by immersion with glutaraldehyde or fixed 40 minutes after the death of animals, it is likely that they represent an artifact, showing an autolytic change, caused by poor fixation or postmortem change.
Myometrial ultrastructure and innervation in Motis lucifugus, the little brown bat
Authors: Buchanan G. Dale , Garfield R. E. 
Published: February 2005

AbstractUteri from hibernating bats, Myotis lucifugus, collected periodically from Renfrew County, Ontario, were fixed in 2% glutaraldehyde and processed for electron microscopy or incubated in glyoxylic acid to show adrenergic nerves by fluorescence. The bat uterus is structurally typical of mammalian species; although the right uterine horn is permanently enlarged in parous bats due to hypertrophy of both myometrium and endometrium. Nerves were abundant between both longitudinal and circular layers of muscle cells. Unmyelinated, and some myelinated, axons, ranging from few to many, coursed generally parallel to the uterine long axis. Numerous axonal varicosities containing small dense‐cored (adrenergic) vesicles or, less often, small agranular (cholinergic) vesicles, were found forming close nerve‐muscle contacts between myometrial cells and blood vessels. Fluorescent microscopy showed a dense network of adrenergic nerves in parous uteri, but a sparse network in nulliparous uteri. A specific adrenergic nerve marker, 5‐hydroxydopamine, greatly increased the density and in some instances, the size of granular vesicles, while 6‐hydroxydopamine, which depletes adrenergic neutrotransmitter, reduced the number of dense‐cored vesicles. Nulliparous uteri appeared unchanged by six daily injections of 0.1 μg estradiol‐17β; 0.25 mg progesterone, or both; but parous uteri were greatly enlarged by all regimes. Nerve ultrastructure, however, appeared unaffected by steroid treatment; nor, despite the absolute dextral bias in implantation, were left‐right differences observed. Gap junctions were not found between muscle cells in myometria of any bat uteri. Based on this study, we suggest that M. lucifugus may provide a most useful model for examination of neurogenic regulation of the uterus.
PGE2 stimulates both resorption and formation of bone in vitro: Differential responses of the periosteum and the endosteum in fetal rat long bone cultures
Authors: Nefussi Jean‐Raphael , Baron Roland 
Published: February 2005

AbstractThe ability of PGE2 to stimulate bone resorption in vitro and in vivo is well established but the effects of this compound on bone formation are still controversial. Recent clinical reports have suggested that long‐term infusion of PGE in infants with cyanotic heart diseases led to a stimulation of periosteal bone formation and to hyperostosis.In the present report, we describe the effects of PGE2 (10−5 M) in bone organ cultures on bone resorption, measured by the release of 45Calcium and the number of osteoclasts in sections of cultured bones, and bone volume, by measuring separately medullary and cortical areas. PGE2 induced a marked increase in 45Ca release and in cortical and medullary osteoclast numbers over 4 days in vitro; despite this increase in bone resorption, cortical bone volume remained constant, indicating a parallel increase in bone resorption and formation at this site. Morphological and quantitative data demonstrated a higher extent of osteoblastic surface along the periosteum of PGE2‐treated bones when compared with control cultures. Medullary bone volume, on the other hand, decreased sharply during the culture period, demonstrating a lack of parallel increase in bone formation at this site.It is concluded that, under these experimental conditions, prostaglandin E2 stimulated both resorption and formation along the periosteum and only bone resorption along the endosteum of the cultured bones. The overall effect of PGE2 on bone as a whole, however, was net bone loss.
The distribution and spatial organization of the extracellular matrix encountered by mesencephalic neural crest cells
Authors: Brauer Philip R. , Bolender David L. , Markwald Roger R. 
Published: February 2005

AbstractCephalic neural crest (NC) cells enter a cell‐free space (CFS) that contains an abundant extracellular matrix (ECM). Numerous in vitro investigations have shown that extracellular matrices can influence cellular activities including NC cell migration. However, little is known about the actual ECM composition of the CFS in vivo, how the components are distributed, or the nature of NC cell interactions with the CFS matrix. Using ultrastructural, autoradiographic, and histochemical techniques we analyzed the composition and spatial organization of the ECM found in the CFS and its interaction with mesencephalic NC cells. We have found that a specific distribution of glycoproteins and sulfated polyanions existed within the CFS prior to the translocation of NC cells and that this ECM was modified in areas occupied by NC. The interaction between the ECM components and the NC cells was not the same for all NC cells in the population. Subpopulations of the NC cell sheet became associated with ECM of the ectoderm (basal lamina) while other NC cells became associated with the ECM of the CFS. Trailing NC cells (NC cells that emerge after the initial appearance of NC cells) encountered a modified ECM due to extensive matrix modifications by the passage of the initial NC cell population.
Variation in basement membrane topography in human thick skin
Authors: Kawabe Thomas T. , Maccallum Donald K. , Lillie John H. 
Published: February 2005

AbstractSamples of human plantar and palmar skin were excised and incubated in 20 mM EDTA after which the epidermis was gently separated from the dermis with the plane of separation occurring in the lamina lucida. Scanning electron microscopic examination of the dermal component revealed the classically described series of regularly spaced grooves and papillae that characterize the epidermal‐dermal junction in thick skin. Primary dermal grooves exhibited evenly spaced tunnels that were originally occupied by sweat gland ducts. The basement membrane (basal lamina) in the primary grooves was relatively smooth but did exhibit a flattened, reticulated pattern at high magnifications. The basement membrane of secondary dermal grooves and papillae was in the form of numerous, elevated microridges off of which septae arose at roughly right angles. The surface appearance of the basement membrane in these areas was that of a honeycomb owing to the numerous compartments and recesses formed by the ridges and septae. Degradation of the basement membrane by trypsin demonstrated that the foundation for the highly folded and compartmentalized basement membrane was composed of dermal collagen fibrils, 60–70 nm in diameter, that were arranged in a series of variably sized, interconnected collagen bundles or walls. Epidermal basal cells extended cytoplasmic (foot) processes into two or more compartments, formed by the ridges and septae, which considerably amplified the basement membrane surface available for epidermal attachment. Scanning electron microscopic studies of the epidermal‐dermal junction confirm the variable surface character of this interface previously reported by others using sectioned material. This regional variation in surface architecture apparently distinguishes between areas in which epidermal basal cells are specialized for attachment (papillae, secondary dermal grooves) and regions occupied by slow cycling epidermal stem cells from which mitotically active keratinocytes arise.
Sex differences in circadian rhythms of several variables in lymphoreticular organs, liver, kidney, and corneal epithelium in adult CD2F1 mice
Authors: Tsai T. H. , Scheving L. E. , Scheving L. A. , Pauly J. E. 
Published: February 2005

AbstractIn this paper data resulting from an investigation into the influence of sex on selected circadian rhythms in lymphoreticular organs, liver, kidney, and corneal epithelium of adult CD2F1 mice are reported. Increased organ weight, total DNA and RNA in the spleen, total DNA and [3H thymidine ([3H]TdR)] incorporation into DNA in the thymus, and [3H]TdR incorporation into DNA in the liver and bone marrow in female mice compared to male littermates is demonstrated. In contrast, kidney weight and [3H]TdR incorporation into DNA as well as the corneal epithelium mitotic index are greater in male mice. Except for the corneal epithelium mitotic index and total splenic RNA and DNA, circadian rhythmicity in the variables studied is validated using the cosinor method of rhythmometric analysis in male but not in female mice. The lack of sinusoidal rhythmicity in female mice is presumed to be due to asynchrony of estrous cycling between mice within this group. Moreover, a differential organ response to exogenous testosterone enthanate is reported. The administration of this hormone suppresses [3H]TdR incorporation into DNA in the thymus and liver but not in the spleen or bone marrow at 18, 42, or 72 hr after injection.