bluuebunny/crossref_metadata_2025_split huggingface dataset:
Purkinje fibers of sheep papillary muscle: Occurrence of discontinuous fibers
Authors: Hondeghem L. M. , Stroobandt R. 
Published: February 2005

AbstractMapping of the peripheral specialized conducting system of the heart could contribute to an understanding of normal and abnormal impulse propagation. In this study, a sheep right anterior papillary muscle was sectioned serially and stained for Purkinje fibers with the periodic acid Schiff and hematoxylin procedure. The subendocardial Purkinje fibers entered the papillary muscle through its base and extended nearly to its apex. Except for one “mixed” fiber group, the subendocardial fibers did not connect to the deep Purkinje fibers, and both groups contained discontinuous Purkinje fibers. The fibers of the moderator band radiated in such a complex fashion that they could not be reconstructed exactly, but they generally disappeared in the ventricular wall through the base of the papillary muscle and false tendons. No direct connections between the subendocardial Purkinje fibers and those of the moderator band could be found within the boundaries of the papillary muscle, and this may form the basis for the relatively late activation of the papillary muscle as compared to the surrounding myocardial wall. The discontinuous fibers we observed are compatible with a current concept regarding the embryology of the ventricular specialized conducting system, and are not in conflict with normal impulse propagation.
Ethionine induced degeneration and regeneration in the rat parotid gland: An electron microscope study
Authors: Leeb Irwin Joel 
Published: February 2005

AbstractThe object of the present study was to establish a model for the study of parotid gland regeneration. Adult female Sprague‐Dawley rats were placed for 11 days on a protein‐free diet with daily intraperitoneal doses of aqueous DL‐ethionine equivalent to 0.5 mg/gm body weight, and returned to a normal diet on day 12. At varying intervals, both during and after intoxication, animals were sacrificed and the parotid glands prepared for study with the transmission electron microscope.Ultrastructural observations indicated that damage was essentially limited to the acinar cells, in which the protein synthetic apparatus was the focus of injury. The rough endoplasmic reticulum displayed atypical configurations, loss of attached ribosomes and membrane fragmentation. In the Golgi region, an atypical structure, a “crystalloid” arose during intoxication. Because of the morphology and apparent formation of the “crystalloid” it was assumed to be an abnormal secretion product. Resumption of a normal diet resulted in the rapid restitution of the normal cytoarchitecture. During the first week of recovery, there was prominent mitotic activity in mature acinar cells.It was concluded that the primary effect of ethionine upon the parotid gland is interference with the function of the protein‐synthetic apparatus, leading to morphologic alteration of the acinar cells. The mitotic activity observed during recovery indicated that in the adult rat, acinar cells retain the potential for proliferation.
Ultrastructural studies of traumatic cataractogenesis: Observations of a repair process in mouse lens
Authors: Rafferty Nancy S. , Goossens William 
Published: February 2005

AbstractLenses of CFl mice were studied with the transmission electron microscope at frequent intervals through 13 months following a transcorneal needle injury to the lens. While this kind of injury causes a high incidence of traumatic cataract in the human and frog, it elicits a repair process in the mouse lens whereby the damaged capsule, epithelium and lens fibers are rapidly renewed and permanent lens opacity seldom occurs. Ultrastructural changes in lens epithelial cells adjacent to the wound, which precede and accompany localized cellular proliferation and production of new capsule, involve a rapid increase or enlargement of organelles associated with protein synthesis and assembly. The capsule and epithelium are repaired within a couple of months. Cortical lens fibers in the wound area undergo conformational changes into smaller, ordered arrays of “membranous sacs.” These are replaced within a week by normal appearing lens fibers. There is minimal degeneration or hyperplasia noted, and except for a few fibroblastic cells on the lens surface, little evidence remains of the injury by two months. Ultrastructural differences between mouse and human lens, such as presence or absence of dense bundles of microfilaments and desmosomes are considered in relation to lens shape and tension, and susceptibility to injury‐induced cataract.
Histological and three dimensional organization of the odontogenic organ in the lower incisor of 100 gram rats
Authors: Smith C. E. , Warshawsky H. 
Published: February 2005

AbstractA three dimensional reconstruction of the epithelial tissue at the apical end of the lower rat incisor was made from serial 1 μm thick cross sections. This tissue formed an elongated structure, called the odontogenic organ, which was composed of a bulbous and a “U”‐shaped part. Both parts were joined to one another at the posterior aspect of the apical foramen. The bulbous part of the odontogenic organ was situated at the lingual side of the “U”‐shaped part and protruded anteriorly over the pulp. It was formed by cells of the outer dental epithelium and stellate reticulum whose organization suggested that the bulbous part was important in the production of cells for renewal of all the epithelia of the incisor. The “U”‐shaped part of the odontogenic organ was apparently derived from the bulbous part and delineated the pulp by forming the lateral, mesial and labial sidewalls around the apical foramen. It was composed of all the epithelial cell types recognizable as precursors to (a) cells of the enamel organ which form the enamel, and (b) Hertwig's epithelial root sheath, a part of the odontogenic organ which induces the formation of dentin on the lingual aspect of the incisor.
Histological and three dimensional organization of odontogenic organ in the upper incisor of 100 gm rats: Comparison with the lower incisor
Authors: Smith C. E. 
Published: February 2005

AbstractThe epithelial tissue forming the posterior aspect of the apical foramen in the upper incisor of the rat was reconstructed from 1 μm thick serial cross sections. Like the lower incisor, this portion of the odontogenic organ in the upper incisor was composed of a bulbous and a “U”‐shaped part. However, the bulbous part was considerably blunter and the “U”‐shaped part much larger in circumference in comparison to the lower incisor. Although no differences were found between the upper and lower incisor regarding the contents and the basic organization of cells within each part of the odontogenic organ, specific differences were found within the bulbous part in the upper incisor. There was a more definitive boundary between the outer dental epithelium and stellate reticulum, a more intimate relationship of cell streams to the stellate reticulum, and a noticeable lack of swirling of cells as part of the streams. These features suggest that the activity inside the bulbous part is less intense in the upper incisor than it is in the lower incisor. In addition, the relationships between the bulbous part, the “U”‐shaped part and the root sheath part of the odontogenic organ and the enamel organ were described for the upper incisor.
Fetal monkey absorption of 55Fe from amniotic fluid
Authors: Orlic Donald , Lev Robert 
Published: February 2005

AbstractA single dose of 0.5 mCi radioiron (55Fe) was injected directly into the amniotic cavity of each of four pregnant monkeys near term. At 6 or 24 hours after 55Fe administration, samples of fetal jejunum, ileum, blood, spleen, liver, lung and fetal membranes were taken for radioautography and scintillation counts. Counts were also made on corresponding maternal tissues.Intestinal radioiron levels and localization indicated that fetuses swallowed and absorbed 55Fe within 6 to 24 hours after injection. Silver grains over the meconium bodies of fetal ileum suggested that intestinal epithelium retained at least some of the absorbed radioiron. However, elevated 55Fe levels in fetal blood and hematopoietic organs indicated that transport of radioiron to the circulation had occurred, presumably through fetal intestine, extraembryonic membranes and/or fetal lungs. Transfer of 55Fe across the placenta from fetus to mother occurred at a slow rate, i.e., samples of maternal organs obtained at 24 hours gave low counts.
Scanning electron microscopy of yolk absorption in early chick embryos
Authors: Litke Larry L. , Low Frank N. 
Published: February 2005

AbstractFresh pullet eggs (White Leghorn Strain) were incubated from 6–19 hours. Blastoderms were fixed in situ with aldehyde fixative, post‐osmicated in 2% OsO4, dehydrated in acetone, criticalpoint‐dried, mounted ventral side up, coated with palladium‐gold wire and observed in a Cambridge Stereoscan S4 scanning electron microscope.Large extracellular yolk granules had a smooth surface and appeared to break up into smaller particles. Similar particles have been observed intracellularly in transmission electron microscopy. Numerous microappendages, mostly ruffles, suggest phagocytosis as a method of absorption of yolk granules into the cells. Absorption of yolk by the cells of the blastoderm involves an initial break up of yolk granules followed by phagocytosis.
Morphological effects of a large single dose of cycloheximide on the intestinal epithelium of the rat
Authors: Altmann Gabriel G. 
Published: February 2005

AbstractAdult male rats received 15 mg/kg cycloheximide and the subsequent morphological effects at three and six hours after injection were evaluated using histometry, light and electron microscopy, histological demonstration of terminal web and acid phosphatase, and radioautography with tritiated thymidine.Rapid atrophy of the villi took place, progressing from the villus tip by premature exfoliation of epithelial cells. The crypts also diminished by random exfoliation of many crypt cells and by partial or complete disintegration. Mitosis and epithelial cell migration were absent. By six hours, the area occupied by the villi and the crypts per unit length of histological section was decreased by about 70–90% in most of the small intestine but only by about 40–60% in the duodenum and the terminal ileum. In the upper half of the villi, the epithelium was strongly positive for acid phosphatase and contained large numbers of round bodies resembling primary lysosomes. In the lower half, the microvillous border and terminal web were found to be disrupted. Animals receiving only 5 mg/kg cycloheximide also showed the atrophy of villi and crypts, and the round bodies resembling lysosomes.Evidence from several sources has indicated that protein synthesis in normal villus epithelial cells subsides toward the villus tip and becomes minimal at exfoliation. At exfoliation, proteins responsible for epithelial cohesion probably fail because they are no longer replenished. Cycloheximide appears to accelerate this process.
A scanning electron microscopic study of the luteo‐follicular complex. II. Events leading to ovulation
Authors: Motta Pietro , Van Blerkom Jonathan 
Published: February 2005

AbstractMorphological changes on the ovarian surface of different mammals both before and during ovulation have been examined by scanning electron microscopy. Preovulatory follicles were blisterlike structures that protruded markedly from the ovarian surface. Basal areas of preovulatory follicles were covered with polyhedral cells containing numerous microvilli, whereas on the lateral surfaces, superficial cells were elongated and possessed few microvilli. At the apex of the follicle, cells were very flattened and possessed few microvilli, which were present only in regions of intercellular contact. In some apical areas, cells appeared to be degenerating, whereas in other regions, groups of cells had “sloughed off.” In addition, a fluidlike material was observed to exude from intercellular spaces of the superficial epithelium and to cover some apical cells. By transmission electron microscopy, the same fluidlike material was observed to (1) infiltrate the connective tissue of the tunica albuginea, (2) accumulate under the basal lamina, and (3) distend intercellular spaces of the superficial epithelium.Just prior to ovulation, large, irregular areas of the apex were ruptured and the oocyte, covered with a large amount of fluid, appeared to emerge from the follicle. At ovulation, the oocyte was not completely covered with follicle cells and the zona pellucida was clearly evident. The surface of the zona was quite irregular and contained numerous infoldings, channels and crypts. Follicle cells had polyhedral or star shapes and possessed large cytoplasmic evaginations that obliquely penetrated the zona. Both the zona pellucida and corona cells were covered with a fine layer of granular material.The SEM results and parallel TEM observations suggest that a local increase of fluids (edema) may be an important factor in the final decomposition of the distended and weakened apex of the preovulatory follicle. In addition, the participation of follicle cells, smooth muscle cells and the oviduct in the escape of the oocyte from the ruptured follicle is discussed.
Histophysiological evidence for the secretion of polypeptides by the pineal gland
Authors: Lukaszyk Andrew , Reiter Russel J. 
Published: February 2005

AbstractHistophysiological examinations of the bovine and monkey pineal gland indicate that this organ may be involved in the secretion of polypeptides. Using various histochemical procedures designed to identify peptidesecreting cells, granules and/or droplets of presumptive secretory product were identified within cellular processes, within the walls of blood vessels and associated with multilayered corpuscles (corpora arenacea). In bovine pineal tissue, the stained material was found most often in what appeared to be pinealocyte processes, as perivascular granules and associated with multilayered corpuscles. In the monkey pineal the stainable material was more distinct; this was probably due to the earlier fixation of the glands after death of the animals. In this species, the presumptive secretory material was found in nerve fibers, occasionally in glial cell and pinealocyte processes and within and around the walls of capillaries. In nerve fibers, the stained material sometimes resembled Herring bodies of the posterior pituitary gland. Similar material appeared to be located in capillary endothelial cells and within multilayered corpuscles. In pineal tissue of both species, calcium was detectable histochemically within multilayered corpuscles. Although tinctorially different, the presumptive neurosecretory material was similar to that found in the posterior pituitary gland. As a working hypothesis, we propose that polypeptides may be released from cells in conjunction with a carrier protein and that the mechanism of secretion of the polypeptide into the vascular system may involve its exchange for calcium. The calcium is then theoretically deposited in the multilayered corpuscles.
Carbohydrate histochemistry of the opossum submandibular and major sublingual glands
Authors: Pinkstaff Carlin A. 
Published: February 2005

AbstractSubmandibular and major sublingual salivary glands of the opossum contain histochemically demonstrable neutral mucosubstances, nonsulfated acid mucosubstances and sulfomucins. Sialomucins could not be demonstrated conclusively with the methods used in this study. Special serous cells of the opossum submandibular gland contained low concentrations of acidic mucosubstances but no appreciable concentration of neutral mucosubstances was seen. Sulfomucins were not observed in special serous cells. The mucous tubules of the submandibular gland contained high concentrations of neutral mucosubstances. No appreciable acidic mucosubstance was demonstrated in the submandibular gland mucous tubules. Unlike the mucous tubules of the submandibular gland, the major sublingual gland mucous tubules contained high concentrations of both neutral and acidic mucosubstances. The mucous tubules often contained sulfomucin‐positive cells interspersed among cells that contained high concentrations of non‐sulfated acidic mucosubstance. Marked staining of sulfated acidic mucosubstance was seen only in the major sublingual gland, in both the mucous tubules and in the seromucous demilunes. The seromucous demilunes contained both sulfated and non‐sulfated acidic mucosubstances.
Fine structural observations on hemopoiesis in the chorioallantoic placenta of the marmoset
Authors: Jollie William P. , Haar Jack L. , Craig Shirley S. 
Published: February 2005

AbstractHemopoietic sinuses in the chorionic trabeculae of marmoset placenta were examined electron microscopically at several stages of pregnancy. Tissues were prepared both by standard technique and following injection of exogenous peroxidase into the maternal circulation prior to autopsy, and subsequent cytochemical localization of its reaction product in the fetal placenta. Aside from their dilated size and cellular content, the sinuses resembled the allantoic capillaries of the peripheral umbilical circulation in this species; and, in early and midgestational placentas, sinusal endothelium, like that of capillaries, looked mesenchymal. Within the sinusal lumina, differentiating elements in the erythroid line were present in placentas at all stages. Such cells appeared to arise both by a process of proliferation of undifferentiated progenitors from the sinusal lining and by mitosis of pre‐existing erythroid cells. Only the latter process was observed in the mature placenta near term. Granulopoiesis was not observed at any stage; on the other hand, cells in the thromboid line were identified in placentas believed to be near midgestation; and large intrasinusal phagocytes were present in both midgestational and late placentas. In the latter, they were seen to have endocytosed peroxidase, and, by tenuous, dendriform processes, to be related anatomically to large numbers of erythroid cells. Early in gestation, the developing erythroid elements were closely related by areas of contact, both to each other and to the delimiting endothelium of the sinuses.
Labelling of murine epidermal Langerhans cells with H3‐Thymidine
Authors: Mackenzie Ian C. 
Published: February 2005

AbstractEpidermal Langerhans cells may be identified by light microscopy by their strongly positive reaction following incubation for ATPase activity. Intact sheets of epidermis from mice killed at various time intervals following a single pulse label of H3‐thymidine were incubated to demonstrate ATPase activity and subsequently processed for autoradiography. In specimens taken one hour after labelling, many basal keratinocytes were labelled but very few ATPase positive dendritic cells. At subsequent time periods a few pairs of labelled ATPase positive cells were found but individually labelled cells were not observed. The findings suggest that epidermal Langerhans cells from a very stable (labelling index < 0.01%) self‐replicating population which divides to maintain cell spacing during growth. No evidence was found for migration and interchange of Langerhans cells with the connective tissue, or for an origin of Langerhans cells by transformation of another cell type.
Mitochondrial granules of chondrocytes in cryosections of growth cartilage
Authors: Ali S. Yousuf , Wisby Angela 
Published: February 2005

AbstractFresh frozen specimens of growth cartilage have been drysectioned and examined in the electron microscope without any staining. Dense granules in the mitochondria of chondrocytes were observed near calcifying areas. This confirms the presence of these mineral granules in the original tissue because this technique avoids the preparative artefacts of conventional electron microscopy.
Mitotic cells and their microappendages in the primitive streak of the chick embryo
Authors: Harri James E. , Low Frank N. 
Published: February 2005

AbstractFresh pullet eggs (White Leghorn Strain) were incubated to the primitive streak stage of development. Blastoderms were fixed in situ with isotonic aldehyde fixatives and prepared for scanning electron miscroscopy by means of post‐osmication, critical point drying and gold‐palladium coating.Cells judged to be in various stages of mitosis by their surface contours were numerous on the ventral surface of the chick blastoderm. Cells which were in the late preparatory stages for mitosis had rounded up from their surroundings. Microvilli dominated the surface. The degree of separation and number of microvilli increased until late metaphase or anaphase. Mitotic cells did not completely separate themselves from adjacent cells. Ruffles and blebs were not prominent during mitotis and long filopodia were absent. A definite localization of microappendages (microvilli, blebs, ruffles) to the area of cytokinesis was evident in early telophase and persisted through daughter cell formation.
The stimulatory effects of diethylstilbestrol and diethylstilbestrol diphosphate on the reticuloendothelial cells of the rat spleen
Authors: Steven William M. , Snook Theodore 
Published: February 2005

AbstractThe effects of the estrogenic compounds, diethylstilbestrol (DS) and diethylstilbestrol diphosphate (DSP) on morphologically demonstrable characteristics of reticuloendothelial (RE) cells were studied in rat spleen. These included metalophilia, acid phosphatase, nonspecific esterase and phagocytosis. Routine histological and histochemical techniques were used to determine the distribution of metalophilic cells, hydrolytic enzymes, the presence of intracytoplasmic PAS‐positive material, hemosiderin sequestration, and the ability to phagocytose injected carbon particles and bacterial organisms.Changes in these parameters associated with increased RE function were observed in several regions of spleens of DS or DSP‐treated animals. The marginal metalophils at the periphery of the nodule, normally not phagocytic in animals of the age studied, became phagocytic and demonstrated increased metalophilic and enzymatic activity. The red pulp was characterized by increased densities of cells in pulp cords demonstrating metalophilia, hydrolytic enzyme activity, PAS positivity and hemosiderin. Phagocytosed material was limited to cells in the pulp cord. The reactions of the sinus‐lining cells were not affected by this treatment. Results indicated that the marginal metalophils have the capacity to become fully functional RE cells under the influence of these drugs.
Localization of antisera to LHβ and FSHβ in the rat pituitary gland
Authors: Herbert Damon C. 
Published: February 2005

AbstractPituitary glands from adult male and female rats were stained by the immunocytochemical bridge technique with antisera to ovine LHβ and human FSHβ. Peroxidase reaction product was localized in the same PAS‐positive cells with both antisera. The cells varied in size and topographical distribution within the pars distalis. These observations support the concept that a single cell type is responsible for the synthesis of both LH and FSH in the rat.
Junctions between sinusoidal endothelial cells in fetal rat liver
Authors: Montesano R. 
Published: February 2005

AbstractDuring a freeze‐fracture study of tight junctions in fetal rat liver (Montesano et al., '75) unusual patterns of intramembranous particles were observed in regions of contact between sinusoidal endothelial cells. These patterns were mainly represented by arrays of particles, often associated with linear elevations or crests in the membrane A‐face; they may represent abortive forms of tight junctions.