bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electron microscopic changes following canine cardiac allografts: The effects of irradiation
Authors: Weymouth Richard J. , Seibel Hugo R. , Craig Shirley S. , Graham Walter H. , Lower Richard R. 
Published: February 2005

AbstractOrthotopic cardiac allotransplantation was performed on ten adult mongrel dogs. At the time of acute rejection (decline in QRS voltage to at least onehalf of the post‐operative level) a cardiac biopsy was removed from the left ventricle of each dog and followed by 300 r of local x‐irradiation on five consecutive days. After a full course of x‐irradiation (1500r) to each dog a second biopsy was removed from the left ventricle. In this way, each dog acted as its own control in order to determine the effects of x‐irradiation on cardiac transplants and the rejection phenomenon. The electron microscopic findings at the time of acute rejection involved primarily the myocytes and their cellular organelles in that the A, I, and Z bands were less distinct and there was significant enlargement and cytological distortion of the mitochondria, endoplasmic reticulum and T tubules. Endothelial hyperplasia of the smaller blood vessels was also more apparent in the pre‐irradiation biopsies. Following irradiation the ultrastructural changes appeared to be reversed in six of the ten dogs; mitochondria and other organelles of the myocytes were more normal and the banding of the fibers was more distinct. Vascular alterations were less and the tissue approached normal cytological architecture. Pre‐ and post‐irradiated cardiac tissues were not different in two animals and in two other animals the post‐irradiated tissues appeared more abnormal than those showing acute rejection. Local irradiation as a method of immunosuppression in cardiac transplants is discussed.
Repair of the external granular layer after postnatal treatment with 5‐fluorodeoxyuridine
Authors: Shimada Morimi , Langman Jan 
Published: February 2005

AbstractRepair of the external granular layer, damaged by prenatal treatment with methylazoxymethanol, has in previous experiments been shown to be successful; by postnatal day 20 little difference in cerebellar architecture could be detected between treated and control animals. In the present experiments repair of the external granular layer was studied after postnatal treatment with 5‐fluorodeoxyuridine (FUdR), a drug known to interfere with DNA synthesis. Two‐day‐old mice were injected with various doses of this compound and sacrificed at successive time intervals after treatment.A striking difference in response to the treatment was noted between the anterior, intermediate and posterior lobes of the cerebellum. In the anterior lobes 5‐FUdR caused almost complete destruction of the external granular layer and few if any surviving cells were noted. During subsequent days repair of the layer was minimal and a grossly abnormal cytoarchitecture resulted. The Purkinje cells were dispersed throughout the molecular layer and the (internal) granular layer contained only a few cells. In the posterior lobes (particularly in the uvula) 5‐FUdR destroyed many external granular cells but the surviving cells reconstituted a new layer and the normal architecture was temporarily reestablished. Many cells of this new layer migrated centrally to become neurons, but others stopped in their migration halfway through the molecular zone, forming a heterotopic granule cell layer. In the intermediate lobes a thin molecular layer was present, but the Purkinje cells were widely dispersed and separated from each other by light and dark nucleated cells. It is thus concluded that repair of the external granular layer after postnatal damage is minimal in the anterior lobes and most advanced in the posterior lobes; in the intermediate lobes repair was seen but the cytoarchitecture was abnormal.
On the histogenesis of the ovarian interstitial gland in rabbits. I. Primary interstitial gland
Authors: Mori Hiroshi , Matsumoto Keishi 
Published: February 2005

AbstractOvaries from rabbits one to three months old were examined to demonstrate the histogenesis of ovarian interstitial cells.Electron micrographs showed that “primary interstitial gland cells” with abundant agranular endoplasmic reticulum were present prior to appearance of follicular atresia and that extensive development of the agranular endoplasmic reticulum and accumulation of lipid droplets occurred in the epithelial cells of medullary cords and granulosal cell nests. Therefore, it was concluded that the “primary interstitial gland” of juvenile rabbit ovaries is of epithelial origin, derived from the medullary cords and the granulosal nests, although the “secondary interstitial gland” is considered to arise from the theca interna of atretic follicles.This conclusion was confirmed by biochemical and histochemical demonstration of 3β‐hydroxysteroid dehydrogenase, an enzyme system necessary for steroid biosynthesis. The activity of 3β‐hydroxysteroid dehydrogenase increased significantly at two months when the agranular reticulum began to devlop in epithelial cells. Histochemical findings showed that the cells having the enzyme activity were consistent with the cells containing a large quantity of lipid.
Ultrastructure of the bone marrow of the frog
Authors: Campbell Ferrell R. 
Published: February 2005

AbstractThe structure of hematopoietic marrow of the frog, Rana pipiens, was studied by electron microscopy. Lining cells of the sinus wall lack a basal lamina and are not phagocytic. Phagocytic cells of the marrow are found free in the lumina of sinuses and in the extravascular tissue. Heterophil leucocytes, during their differentiation, possess a single population of granules; mature granules are elongate bodies having a crystalline content. Eosinophil leucocytes also have a single population of granules; the granules are round and have a homogeneous content.
Secretory processes in follicular cells of the bat thyroid. I. Ultrastructural changes during the preearly and mid‐hibernation periods with some comments on the origin of autophagic vacuoles
Authors: Nunez Eladio A. , Becker David V. 
Published: February 2005

AbstractUltrastructural changes which occur in bat thyroid follicular cells between late August and early January are discussed. During the first half of this period the principle changes are proliferation of the granular endoplasmic reticulum, an increase in size of the Golgi apparatus and an increase in the number of apical vesicles. These changes are followed by a gradual reduction in the amount of endoplasmic reticulum and in the size of the Golgi complex. During the expansion phase of the granular endoplasmic reticulum, large numbers of dense granules, and “light” and “dark” multivesicular bodies are present throughout the cytoplasm of the follicular cells. An unusual finding is that in the bat, the thyroid follicular cells also contain many autophagic vacuoles at this time. The role of the dense granules in the formation of autophagic vacuoles is discussed and evidence for the transformation of multivesicular bodies into dense granules is presented. Autophagic vacuoles were not found during the phase when the granular endoplasmic reticulum underwent a marked regression. At this time, follicular cells contained prominent complex dense bodies which resemble the “phagolysosomes” of other mammalian follicular cells. These observations are discussed in relation to the changes which occur in thyroid function of hibernators during the period studied.
Myoid elements in the mammalian nephron and their relationship to other specializations in the basal part of kidney tubule cells
Authors: Ross Michael H. , Reith Edward J. 
Published: February 2005

AbstractThe basal region of proximal convoluted tubule cells from mouse kidney was studied with the electron microscope. Particular attention was given to grazing sections, i.e., sections whose plane was approximately parallel to that of the basement lamina. The findings indicate that many of the “basal compartments” of the proximal convoluted cells are elongate parallel structures which contain aggregations of filaments resembling those of smooth muscle. These elongate structures, referred to as myoid bands, react positively with dyes which are selective for muscle tissue. Close membrane appositions are also seen in grazing sections, apparently related to the myoid bands, at least by virtue of location.In addition, the basal region of the proximal convoluted tubule cells possesses branching microvillous processes. Because of their arrangement, the basal extracellular space associated with the microvillous processes appears as a maze‐like network of channels. The microvillous processes and the associated extracellular space are at a level just slightly higher than the level of the myoid bands. This space appears to be distinct from the basal labyrinth inasmuch as the latter extends well into the mitochondrial region of the cell, whereas the basal extracellular space does not. In places, the microvillous processes extend to the basement lamina between the myoid bands.It is postulated that the microvillous processes and the related extracellular space are associated with fluid transport and that the myoid bands may constitute a regulatory device related to the control of fluid movement.
Electron microscope studies of frozen‐substituted marine eggs. III. Structure of the mitotic apparatus of the first meiotic division
Authors: Rebhun L. I. , Sander G. 
Published: February 2005

AbstractEggs of the clam Spisula solidissima were studied by freeze‐substitution techniques at the time of the first meiotic division. The mitotic apparatus is organized into regions containing microtubules, endoplasmic reticulum, ribosomes and mitochondria which surround densely stained amorphous regions. The amorphous regions, which appear to be channels running through the mitotic apparatus, are radially arranged in the asters and are parallel to the spindle axis. Microtubule‐associated particles, each about 250 Å in diameter, are arranged in crystalline arrays around the microtubules of the mitotic apparatus. After a period of time in hypertonic sea water the mitotic apparatus disappears and the microtubule‐associated particles remain aggregated in hexagonally packed crystals. Histochemical tests suggest that the particles are composed of polysaccharide material. Other particles and inclusions show orientation relative to the mitotic apparatus axis or show non‐uniform localization in the egg. The possible meaning of such localization and orientation in the physiology of the egg is discussed.
The opisthonephric kidney of the sea lamprey of the great lakes, Petromyzon marinus L. IV. Intermediate, distal, and collecting segments of the adult
Authors: Youson John H. , McMillan Donald B. 
Published: February 2005

AbstractBoth short and long intermediate segments are found in the opisthonephric kidney of the adult sea lamprey and they possess morphologically distinct cell types. Wide lateral intercellular spaces appear between both the cuboidal cells of short segments and the squamous cells of long segments. Periodically the epithelium of the long segment is reduced in thickness providing for a close relationship between the interstitium and the tubular fluid. These features indicate that the segment may be involved in urine formation.The distal segment is divisible into two distinct portions: a straight pars recta and a twisted pars convoluta. The cuboidal cells of the pars recta and the columnar cells of the pars convoluta are characterized by abundant smooth endoplasmic reticulum and mitochondria, features reminiscent of cells involved in ion transport. Multivesicular bodies, coated vesicles, and dense apical tubules suggest that cells of both regions may also be involved in endocytosis.The cells of the collecting segment have few organelles but they possess a cytoskeleton of coarse filaments and wide intercellular spaces.The parallel arrangement of the intermediate, distal, and collecting segments and of the blood vessels within the adult kidney is suggestive of a functional unit similar to that found in the medulla of the mammalian kidney.
Organization and histology of the pineal region in the hyrax (Procavia capensis)
Authors: Quay W. B. , Millar R. 
Published: February 2005

AbstractThe pineal region of four adult male Procavia capensis from South Africa was studied in serial sections of median portions of entire brains. A consistent and unique pineal morphology was found in all specimens, in contrast with previous reports based on specimens of Procavia from diverse and distant populations or species. A principal pineal tissue mass bounds the pineal recess anterodorsally and makes contact with the subcommissural organ at the apex of the recess. A dorsal or accessory pineal tissue mass occurring on the opposite (anterior or dorsal) side of the habenular commissure forms part of the basal wall of the dorsal sac. Both pineal parts are penetrated throughout by nerve fibers, of which at least the great majority belong to the habenular commissure system. Tissue zonation, rich and distinctive vascularization, abundant pinealocytes in lobules, and parenchymal follicles are also characteristic. The dorsal sac and pineal recess are unusually large in this species. Additional features of the pineal body, dorsal sac and subcommissural organ are described.
Differentiation of the Leydig cell of the mouse testis during the fetal period — an ultrastructural study
Authors: Russo Jose , de Rosas Juan C. 
Published: February 2005

AbstractDifferentiation of the Leydig cell in the fetal mouse as studied by light and electron microscopy was divided into three phases. During phase 1 (day 12 to day 15) the spindle‐shaped cell becomes an immature Leydig cell which contains numerous free ribosomes and some polysomes. Phase 2 (day 16 to day 19) is marked by a considerable development of smooth endoplasmic reticulum and by an equally important decrease in ribosomal population. Mitochondria are increased in number 100%. Phase 3 (day 19 to birth) is characterized by maximal lipid and glycogen content. Close to the time of birth, smooth endoplasmic reticulum decreases in extent and becomes vesicular.The peak in prenatal Leydig cell differentiation as judged by development of the endoplasmic reticulum occurs during phase 2. These findings are discussed in the light of data derived from study of other species and an attempt is made to correlate morphological features with available information concerning the control of differentiation by gonadotropins.
Cholinesterase‐positive and catecholamine‐containing nerves in the guinea‐pig pericardium
Authors: Ellison Jeffrey P. 
Published: February 2005

AbstractThe functions of the pericardium are traditionally defined in terms of lubrication and support. However, its complement of autonomic nerve fibers, shown by physiologc experimnts to be sensory, suggests that the pericardium may also serve as a mechanoreceptor site. In this study acetycholinesterase‐positive, and catecholamine‐containing elements of the pericardial plexus of the guinea‐pig were visualized, using thiocholine and fluorescence techniques, respectively. A cholinesterase‐positive nerve net, containing the preterminal segments of unmyelinated fibers and simple nerve endings, extended over the entire parietal pericardium. Some of the cholinesterase‐positive endings, apparently separate from effector structures were assumed to be sensory. A few heavily myelinated fibers were contributed by the phrenic nerve. The parietal pericardium covering the atria contained many adrenergic nerves and endings. Not all pericardial adrenergic endings were linked to effector structures, such as blood vessels. Some fibers ended freely. It is suggested that liberation of catecholamines from “unattached terminals” may serve to lower the threshold, and prolong the adaptation of adjacent cholinesterase‐positive mechanoreceptor terminals.
Placentation in the American beaver (Castor canadensis)
Authors: Fischer Theodore V. 
Published: February 2005

AbstractImplantation in the beaver is superficial and antimesometrial. The embryonic disc occupies one side of the flattened mesometrial hemisphere of the large blastocyst. An endometrial papilla, unique to the beaver, forms on the mesometrial uterine wall just prior to chorioallantoic contact. The reniform placenta then develops around this papilla. Amniogenesis is by folding. A transient choriovitelline placenta develops very early. Yolk sac inversion is late, and the bilaminar omphalopleure is partially retained throughout gestation. The chorion persists until term as two paraplacental membranes. A large permanent allantoic vesicle is present. The labyrinthine placenta has a lobulate architecture. It possesses a hemodichorial barrier, the inner layer being syncytial and the outer cellular. Maternal blood is supplied by two arterial channels which do not penetrate the labyrinth, and is drained by a single, central venous channel. A large basal subplacenta develops by trophoblastic invasion of the endometrial papilla, and becomes quite massive at term. Its function is unknown. Except for this specialized subplacenta, all the fetal membrane characteristics are typical of the primitive sciuromorph group, to which the Castoridae seem to be closely related.
Argentaffin and other “endocrine” cells of the small intestine in the adult mouse. I. Ultrastructure and classification
Authors: Ferreira M. N. 
Published: February 2005

AbstractElectron microscopic examination of the epithelium of crypts and villi in the jejunum of the adult mouse revealed the existence of three main types of cells which may be classified within the group of argentaffin and other “endocrine” cells of the gastrointestinal tract.Sixty per cent of the cells are characterized by the presence of biconcave granules. They are referred to as biconcave granule cells (Type EC). While most granules are biconcave, some of them are spherical and may show a particulate structure. Those cells with 95% or more biconcave granules predominate in the crypt, while those with 50–75% predominate in villi. The cells of this type are considered by some authors to be true argentaffin or enterochromaffin cells.Thirty‐seven per cent of the cells have spherical dense granules, a few of which look like empty vesicles. However, because of the marked differences between the sizes of the granules, these cells are classified into two categories. Those with granules averaging 360 mμ in diameter are referred to as large spherical granule cells (Type L, 13%), while those with granules averaging 250 mμ in diameter, are referred to as small spherical granule cells (Type S, 24%). Both types are found in crypts and villi.Three per cent of the cells do not fit into these categories. All these uncommon cells contain spherical granules; and, in addition, some have oval ones; others show large halos; and still others include granules of different sizes and densities.The existence of several “endocrine” cell types suggests that they play different roles in the jejunum of the mouse.
The indifferent fiber plexus and its relationship to principal fibers of the periodontium
Authors: Shackleford John M. 
Published: February 2005

AbstractScanning electron micrographs demonstrate the presence of an indifferent fiber plexus as an integral part of periodontia in the rat, dog, armadillo and man. Individual fibers measure 1400 Å in diameter in scanning electron micrographs. The indifferent fibers course in every direction throughout the area between bone and cementum without particular orientation. They anastomose extensively with the principal fibers to form a continuous fibrous matrix. Anastomoses with principal fibers begin adjacent to bone or cementum and increase until the indifferent fiber plexus reaches maximum density a short distance from the mineralized matrix. At this point a principal fiber may lose its structural identity as it blends with the profusion of indifferent fibers. This phenomenon occurs in all species studied but is more evident in the relatively unstressed teeth of armadillos. In the dog, principal fibers may extend from cementum to bone as highly compact structures. Anastomoses between principal and indifferent fibers often occur via fibers of intermediate size. The latter fibers become more oriented as their fiber diameters increase. Gingival fibers of the rat, in contrast to principal fibers of the alveolodental ligament, rarely consist of compact fiber bundles. Instead, fibers of indifferent and intermediate size aggregate to form gingival cords in which component fibers are readily distinguishable.
Tubal surgery in the rabbit: Fertilization and polyspermy after resection of the isthmus
Authors: Hunter R. H. F. , Léglise P. C. 
Published: February 2005

AbstractTransport and capacitation of spermatozoa, and the normality of the process of fertilization, were examined after unilateral resection of the isthmus and end‐to‐end anastomosis of the remaining portions of the Fallopian tube. The operation was performed in eighteen rabbits, in each of which the contralateral tube remained intact to serve as a control.Recent ovulations were present in fourteen animals at autopsy, although in only eleven were ovulations detectable on the side of the anastomosis. Thirteen animals yielded a total of 89 eggs, the proportion recovered from the control tube (79.3%) being significantly higher than that from the anastomosed tube (57.2%). Six of nine anastomosed tubes yielding eggs were patent to sperm passage, and 67% of the eggs recovered from this side were fertilized compared with 91% from the control tubes. Three eggs recovered from the anastomosed tube of three animals were dispermic. It is concluded that normal fertilization and early cleavage of rabbit eggs can take place in the absence of the isthmus, and that the rate of cleavage is not retarded under such conditions. An increased number of spermatozoa on the eggs from the anastomosed tube, together with the incidence of dispermic eggs, indicates that the isthmus exerts considerable control over sperm transport to the site of fertilization.
Osmiophilia of the saturated phospholipid, dipalmitoyl lecithin, and its relationship to the alveolar lining layer of the mammalian lung
Authors: Kaibara Manabu , Kikkawa Yutaka 
Published: February 2005

AbstractThe appearance and the osmiophilic properties of synthetic dipalmitoyl lecithin (DPL) were characterized under various conditions. It was shown that DPL appeared as 50 Å round to oval dots and lamellae of 50 Å periodicity when negatively stained with phosphotungstate. Osmium‐vapor treatment of a DPL suspension produced negatively outlined DPL, similar to the images obtained with negative staining with phosphotungstate. A mixture of ethanol, osmium and DPL showed the heavily osmiophilic lamellae of DPL in thin sections. The periodicity measures 42 Å. These results are the first in the literature to reveal the osmiophilic nature of saturated dipalmitoyl lecithin.Prolonged washing after both glutaraldehyde and osmium fixation of lung tissue, thus eliminating the chance for interaction among osmium tetroxide, ethanol and saturated phospholipid, resulted in a loss of the heavily osmiophilic surface film that has been reported to be present after routine tissue processing. Secondary osmication of the washed lung with a mixture of osmium tetroxide and ethanol solution brought about striking osmiophilia of the surface film, which was lamellar and was identical to synthetic DPL in its periodicity.It is suggested that the osmiophilic line observed after routine tissue processing is saturated phospholipid that binds osmium during the process of ethanol dehydration immediately following osmium fixation.