bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lipoprotein particles in the jejunal mucosa of postnatal developing rats
Authors: Mak Ki M. , Trier Jerry S. 
Published: February 2005

AbstractThe jejunal mucosa of neonatal rats contains lipid particles of the same size, electron density and intracellular and extracellular distribution as particles identified by others in adult jejunum as lipoprotein particles. As in fetal jejunum obtained during the last three days of gestation, the jejunal mucosa of unsuckled newborn rats contains exclusively lipoprotein particles the size of very low density lipoproteins (VLDL). Within one day after initiation of suckling, there is in the mucosa a spectrum of lipoprotein particles ranging widely in size from those of VLDL particles to those of chylomicrons. These particles are seen in the endoplasmic reticulum and Golgi material of absorptive cells and within interepithelial cell spaces, the extracellular spaces of the lamina propria and lymphatic lacteals. VLDL‐sized and chylomicron‐sized particles are also seen, although in decreasing number, in the jejunal mucosa of 18‐day‐old suckling rats. However, in rats of comparable age, fasted for 48 or 72 hours, only VLDL‐sized particles are seen in the jejunal mucosa. Ligation and transection of bile duct followed by fasting in rats of this age results in a marked decrease in the number of lipoprotein particles in absorptive cells. The results indicate that endogenous lipid contributes to the formation of VLDL particles whereas dietary triglycerides are needed for formation of chylomicrons.
An autoradiographic and immunocytochemical study of the neonatal rat pituitary gland
Authors: Sheridan Peter J. , Herbert Damon C. 
Published: February 2005

AbstractTwo‐day‐old female rats were injected with 5 nmole/kg of 6,7‐3H‐11β‐methoxy‐17‐ethylestradiol (R 2858 = moxestrol) and killed one hour later. The animals were decapitated and, the pituitary glands were removed, mounted on tissue holders and frozen in liquified propane. The tissue was then processed for autoradiography according to the thaw mount technique. At the end of the exposure time, prior to photographic development, some of the tissue was fixed in 10% formalin and then photographically developed for autoradiography. The fixed tissue was subsequently stained immunocytochemically using antibodies to luteinizing hormone or prolactin. Between 10 and 15% of the cells of the pars distalis concentrated the synthetic estrogen or its metabolite. The immunocytochemical procedure revealed that both LH‐gonadotrophs and lactotrophs concentrated the steroid. These studies along with earlier studies suggest that the neonatal rat pituitary contains only a small portion of the adult complement of estrogen receptors and that these receptors are dispersed across a number of cell types.
Surface area ratios. I. A stereological method for estimating average cell changes in membrane surface areas
Authors: Bolender Robert P. 
Published: February 2005

AbstractThe study (i) describes a method for estimating relative changes in membrane surface areas as they occur in stereological “average cells,” and (ii) considers the effect of the controls on these estimates. The results indicate that changes in five membrane compartments of pancreatic exocrine cells‐produced by a secretagogue (carbomylcholine chloride)‐were detected similarly when related to either an average cell surface (surface area ratio method) or to an average cell volume (method of Loud, '68). Changes, however, detected with surface densities, which relate these membrane compartments to 1 cm3 of exocrine cell cytoplasm or pancreas, were notably different from the first two estimates. This inconsistency could be explained by the fact that the surface densities were influenced not only by membrane changes within the exocrine cells, but also by changes in the number of these cells filling the cm3 of reference volume. Relating the data to an average cell reference–instead of 1 cm3–improved the accuracy of the estimates for changes in membrane surface areas by as much as several fold; the choice of controls had a similar several‐fold effect on the results.
Structure of retzius lines in partially demineralized human enamel
Authors: Weber Dennis F. , Ashrafi Shahid H. 
Published: February 2005

AbstractHuman third molars were partially demineralized in an acid‐alcohol solution and embedded in Epon 812. Six‐micron sections were cut from regions of the cervical enamel exhibiting prominent Retzius lines. The plastic was removed from the specimens by microincineration and were examined with the scanning electron microscope. The most prominent structural feature seen along the Retzius lines was the cervical translocation of some of the prisms. The scanning electron microscopic images also suggested that prisms were translocating in the transverse plane of the tooth. A series of pores, which appeared to be empty, were observed in association with the translocations occurring along the Retzius lines.
Intercellular junctions in the rhesus monkey pars distalis
Authors: Herbert Damon C. 
Published: February 2005

AbstractFour rhesus monkey pituitary glands were examined by transmission electron microscopy. Three types of intercellular junctions, desmosomes, hemidesmosomes and zonula adherens‐type junctions, were observed between adjacent granular cells, folliculo‐stellate cells, and joining a folliculostellate cell with a granular cell. Desmosomes were most commonly observed between granular cells while the zonula adherens‐type junctions were generally found between the folliculo‐stellate cells.
Replacement of fatty marrow by active granulocytopoietic bone marrow following transplantation of mammary carcinoma into mice
Authors: Lee Minako Y. , Rosse Cornelius 
Published: February 2005

AbstractThe development of granulocytic hemopoiesis in the fatty marrow of metatarsal bones and caudal vertebrae of adult mice was studied in histological sections for up to six weeks following subcutaneous innoculation of granulocytosis inducing mammary carcinoma. The initial events observed were increase and engorgement of fatty marrow sinusoidal vascular beds, accompanied by numerous lymphoid mononuclear cells in the sinusoids and in the stroma. Foci of granulocytopoiesis appeared admixed with lymphoid cells in the stroma and near the endosteum. Hyperplastic granulocytopoiesis eventually predominated in the marrow of these bones as well as the femoral and sternal marrow of tumor bearing mice. The morphological findings suggested the possibility of stem cell and progenitor cell migration into fatty marrow, but activation of dormant stem cells could not be ruled out. The prevalence of granulocytopoiesis in the entire skeletal marrow in tumor bearing mice may seriously impair the production of other cellular components of the marrow including lymphocytes, reduced production of the latter would imply serious compromise for the immune system of the tumor bearing animals.
Developmental history of nervus terminalis in embryos of insectivorous bats
Authors: Brown Jerry William 
Published: February 2005

AbstractInsectivorous bat embryos (TadaridaandMyotis) ranging from 6‐to 16‐mm C‐R length were examined for the presence of the nervus terminalis. These embryos have no vomeronasal nerve with which the nervus terminalis could be confused. The nerve and associated ganglion cells first appear in the 7‐mm embryo. As the embryo ages, a gradual increase in nerve size and ganglion cell numbers occurs. In the 13‐mm embryo, nerve size and ganglion cell numbers are reduced, and in older embryos both nerve and cells are absent, as in the adult. The ganglion cells arise as clusters from the nasal septal epithelium. The largest number of cell clusters occurs in the 10.5‐mm embryo. Their number then decreases and none are present in embryos of 13‐mm and longer. These cells migrate centrally along the course of the nerve which accompanies the olfactory nerve from the nasal cavity roof to a level just caudal to the olfactory bulb, where the nervus terminalis turns dorsalward along the medial telencephalic wall surface. Except in the youngest and oldest embryos the nervus terminalis, where present, divides into two or three branches to pierce the hemispheric wall, one usually entering the region of the nucleus olfactorious anterior, and the other(s), the region of the medial septal nucleus. In some cases, several ganglion cells are present along the intrahemispheric course of the nerve fibers. All ganglion cells resemble those in various sensory ganglia, and so, are probably also sensory neurons.
Ascending projections of the dorsal column in a garter snake (thamnophis siritalis): A degeneration study
Authors: Jacobs Virgil L. , Sis Raymond F. 
Published: February 2005

AbstractAscending axons in the dorsal column of garter snakes were examined following hemisection of the spinal cord at segment levels 2, 3, 4, 11, 13, and 31. After postoperative survival periods of 11 to 28 days, sections of the spinal cord and brain were processed with a silver method to demonstrate degenerated axons and preterminals.The study demonstrated that most ascending degenerated axons are located in the outer half of the dorsal column. The somatotopic pattern of ascending fibers is evident, whereby dorsomedial fibers are primarily of caudal origin and the more dorsolateral axons are from rostral cord segments. Rostral to segment 31, all spinal segments appear to project to a strip of dorsal column adjacent to the dorsal median septum. From the septum, axons descend to terminate somatotopically on cells of the nucleus of Bischoff located caudal to the obex of the medulla.Dorsal column degeneration ascends to the level of the dorsal column nuclei, where most fibers terminate. Degeneration from caudal cord segments terminates on caudo‐medial cells of the dorsal column nuclei, while rostral cord segments project to rostro‐lateral cells. The dorsal column nuclei consist of an expanded lateral part between tractus descendens trigemini and the vago‐solitary complex, and a contiguous, thin medial lamina of cells dorsal and medial to the vagal nuclei. The somatotopic pattern of degeneration in the dorsal column nuclei, probably of dorsal root origin, follows the mammalian organization, which suggests that the garter snake has primitive nuclei gracilis and cuneatus. Other terminal sites of degenerating fibers, although probably of spinal gray origin, are nucleus commissura infima, nucleus descendens vestibuli, and area postrema.
Evolution of the endoplasmic reticulum in the Sertoli cell cytoplasm encapsulating the heads of late spermatids in the rat
Authors: Clermont Y. , McCoshen J. , Hermo L. 
Published: February 2005

AbstractThroughout stage VII and early stage VIII of the cycle of the seminiferous epithelium, the heads of the late spermatids, located in a juxtaluminal position, are embedded in apical processes of Sertoli cells. These processes contain cisternae of endoplasmic reticulum (ER) of two main types, i.e., flattened and tubular, which communicate with each other to form a continuous system. Throughout the long stage VII of the cycle, these two types of cisternae undergo marked changes. In early stage VII, the flattened cisternae, developing from the subsurface cisternae which compose the “junctional specialization,” form concentric sheets at the periphery and in the middle of each apical process. The less conspicuous tubular cisternae form a continuous network which is present in the bridge connecting the Sertoli cell body to the apical process, and extends along the dorsal and ventral aspects of the spermatid's head to end up as cup‐shaped flattened cisternae capping the bulbs of the tubulobulbar complexes described by Russell and Clermont ('76). In mid stage VII, the flattened cisternae start to regress, while the tubular cisternae become more abundant. In late stage VII, only fragments of the flattened cisternae are present, while the tubular cisternae form a profuse and elaborate network throughout the apical process. In the following stage VIII, the tubular cisternae disperse and only remnants of ER are present at the time of the release of the spermatid into the tubular lumen. These transformations of ER cisternae suggest a complex alteration in the relationship between Sertoli cells and late spermatids prior to their release as spermatozoa.
Gap junctions between cells of bone marrow: An ultrastructural study using tannic acid
Authors: Campbell Ferrell R. 
Published: February 2005

AbstractIn bone marrow of the mouse perfused with fixative containing tannic acid and glutaraldehyde, gap junctions were observed between certain cell types. Gap junctions were seen between adjacent reticular cells, between adjacent macrophages, and between macrophages and reticular cells. Macrophages formed gap junctions with immature neutrophils, eosinophils, monocytes, and erythroblasts. Often a single macrophage had gap junctions with neutrophilic, eosinophilic, and monocytic cells; these blood cells varied from immature to nearly mature forms. In contrast, the macrophages associated with erythroblasts had gap junctions only with erythroblasts and all the erythroblasts were in the same developmental stage. The possible role of the gap junctions in differentiation and mobilization of marrow cells is discussed.
Extracellular spaces of the rat pars intermedia as outlined by lanthanum tracer
Authors: Saland L. C. 
Published: February 2005

AbstractThe extracellular spaces of the rat pars intermedia were examined after perfusion with fixative containing lanthanum. The tracer reveals complex and extensive interdigitations among secretory cells. Spaces appear continuous with extracellular “channels” between the epithelial cells lining the hypophyseal cleft. Some suggestion for close contiguity between endocrine cells was present as “narrowing” or discontinuous areas within lanthanum‐filled spaces. Extracellular regions surrounding nerve fibers and terminals appear continuous with the spaces between secretory cells. Areas between cells are thought to provide access to vascular and local neurotransmitter input, as well as to provide an extensive area for extrusion of peptide hormones and endogeneous opiates.
Ultrastructural evidence for seasonal changes in pinealocytes of the 13‐lined ground squirrel, spermophilus tridecemlineatus: A qualitative and quantitative study
Authors: McNulty John A. , Dombrowski Teresa A. 
Published: February 2005

AbstractThe fine structure of pinealocytes in the hibernating ground squirrel, Spermophilus tridecemlineatus, was found to vary both qualitatively and quantitatively according to the season in which the animals were sacrificed. Ultrastructural features of pinealocytes from fall (prehibernation) and winter (hibernation) periods, when the animals were sexually quiescent, included: (1) arrangement of the endoplasmic reticulum into flattened stacks or concentric rings (formations which have been implicated in antigonadotropic activity of the pineal); (2) condensations of a fine granular material; and (3) dilation of the cisternae of the endoplasmic reticulum and Golgi bodies with an increased number of Golgi associated vesicles. Moreover, there was an apparent increase in the number of dense‐cored vesicles and microtubules in pinealocytes of winter animals. These findings indicate that a circannual rhythm in pinealocyte ultrastructure occurs in this species and further suggest that cellular activity is seasonal.
The effects of chronic hypoxia on the myocardial cell of normotensive and hypertensive rats
Authors: Lund Donald D. , Tomanek Robert J. 
Published: February 2005

AbstractMyocardial cellular and subcellular adaptations associated with chronic hypoxia were determined in 16 week old male normotensive Wistar‐Kyoto, spontaneously hypertensive and aortic constricted rats. The animals were exposed to six weeks of hypobaric hypoxia at a simulated altitude of 6,100 (m), and their glutaraldehyde perfuse‐fixed hearts compared to normoxic controls.Exposure to hypoxia abolished the hypertension associated with the spontaneously hypertensive and aortic constricted groups and reduced the mean heart rate in all three hypoxic groups. The magnitude of hypertrophy was significant and comparable in all three groups, based on heart weight and left ventricular fiber diameter measurements. While capillary density was significantly reduced in the spontaneously hypertensive and aortic constricted rats, exposure to hypoxia facilitated an absolute increase in the number of capillaries of the hypoxic spontaneously hypertensive and aortic constricted rats. In the hypoxic control group, the capillary density was maintained despite a 20% increase in the muscle fiber diameter, indicating a proliferation of the capillary bed in proportion to the increase in muscle mass. The myocytes in all hypoxic groups were characterized by deep invaginations of the cell membrane and an increase in the number of pinocytotic vesicles. Stereological analyses of the myocytes revealed a statistically significant decrease in the mitochondria/myofibril volume ratio in animals with pressure overload. This ratio was not significantly altered when the animals were subjected to chronic hypoxia. However, there was an increase in the number of mitochondrial profiles and a decrease in the size of individual profiles in all hypoxic groups when compared to the control group.These findings suggest that cardiac hypertrophy associated with chronic hypobaric hypoxia, unlike hypertrophy due to pressure overload, is associated with a number of structural adaptations which may aid the heart in functioning in the hypoxic environment.
The blood supply to the splenic lymphatic nodules in the rhesus monkey
Authors: Snook Theodore 
Published: February 2005

AbstractThe arterioles and capillaries supplying the lymphatic nodules and marginal zone (in part) in the rhesus monkey's spleen arise from a follicular artery branch of the central artery. This follicular artery first undergoes a series of convolutions and branchings, out of which a parallel array of tightly bound arterioles and capillaries, an anteriorlar capillary bundle (ACB), leading into the central part of the nodule is formed. From the proximal end, side, and distal end of the ACB, arterioles and capillaries radiate outward through the mantle zone of the nodule to terminate in the marginal zone. Some capillaries are formed within the bundle and others not until an arteriole nearly reaches the marginal zone.A similar ACB and capillary distribution is found in the human spleen. However, the supplying arteries, for the most part, come from recurrent penicillar arteries which pass close to the central artery before forming the bundle. This artery does not undergo the convolutions found in the rhesus monkey. In the monkey, the bundle contains a higher proportion of arteriolar vessels. It appears that in human and rhesus monkey spleens, the ACB replaces the internal capillary net of Jäger (′29).
The ultrastructure of oral (buccopharyngeal) membrane formation and rupture in the chick embryo
Authors: Waterman Robert E. , Schoenwolf Gary C. 
Published: February 2005

AbstractThe ultrastructure of the oral (buccopharyngeal) membrane was examined by transmission and scanning electron microscopy (SEM) from its initial formation (stage 8) to its complete disappearance (stage 20) in the chick embryo. Thinning of the oral membrane prior to rupture occurs in large measure by increased interdigitation between cells of the stomodeal ectoderm and foregut endoderm coincident with a decrease in the width of the intervening extracellular space. Large numbers of necrotic cells were not observed. Interdigitation of ectodermal and endodermal cells makes it increasingly difficult to discern two discrete epithelia, and no evidence that one germ layer disappears prior to the other was observed. Changes occurred in the fine structure of the extracellular matrix during formation and rupture of the oral membrane, and the organization of this material within the oral membrane differed from that in regions immediately lateral to it. Copious amounts of amorphous, flocculant (“lamina‐like”) material are present within the oral membrane at all stages. The basal lamina of the ectoderm exhibits small loops or folds at early stages. These decrease in number as the basal lamina becomes discontinuous prior to establishment of direct intercellular contact between cells of the ectoderm and endoderm across the intervening extracellular compartment. Initial perforations of the oral membrane are preceeded by clefts between cells on both sides of this structure, and SEM observations suggest that cells of the oral membrane continue to interdigitate, elongate, and change relative positions during the rupture process.
Immunohistochemical study of lymphocytes in rat pineal gland: Selective accumulation of T lymphocytes
Authors: Uede Toshimitsu , Ishii Yoshifumi , Matsuura Akihiro , Shimogawara Izuru , Kikuchi Kokichi 
Published: February 2005

AbstractMorphologic and immunohistochemical studies were performed to examine the existence of lymphocytes in the brain of rats. Special attention was paid to the time course of the appearance of lymphocytes in and around the pineal gland. Rabbit anti‐rat T cell and anti‐rat immunoglobulin sera were used for identification of T and B cells in tissue sections. Immunoperoxidase and immunofluorescence techniques were employed to identify cells reacting with anti‐T and anti‐immunoglobulin sera.No lymphocytes were found in the brain of rats until 20 days after birth. Small clusters of lymphocytes appeared in the pineal region by 30 days of age, after which they gradually increased in number, forming massive clusters in the pineal region by 120 days. Along with an increase in the number of lymphocytic cells, there was a gradual increase of cells reacting with anti‐T cell serum. These T cells were only a minority of pineal lymphocytes in younger animals, but 90% or more cells were stained by anti‐T cell serum at 120 days after birth. The remaining cells did not react with anti‐immunoglobulin sera either. These findings suggest that the gradual increase of T lymphocytes in the rat pineal region is a simple reflection of the normal course of maturation of T cells, and the pineal gland in the rat may have some role in immune responses within the brain.
Morphogenesis of conjunctival papillae from normal and scaleless chick embryos
Authors: Blanck Cynthia E. , McAleese Susan R. , Sawyer Roger H. 
Published: February 2005

AbstractMorphogenesis of avian conjunctival papillae follows a predictable temporal and spatial pattern and is in some manner directly related to the induction of the underlying scleral ossicles. We have been able, using Scanning Electron Microscopy (SEM), to correlate all of Murray's ('43) histological stages (1–6) of papillae development, with changes in elevation and morphology of the surface of the conjunctiva. The first indication of morphogenesis is the formation of “papillae primordia”. The centers of these primordia exhibit decreased intercellular contact, and become elevated as radially symmetrical humps whose surfaces are composed of rounded cells with numerous microvillar projections. As the papillae become asymmetrical and elongate, cells near the tip of the papillae enlarge and develop microridges. During regression of the papillae, single clusters of cells appear to become lost from the surfaces of the papillae into the surrounding fluid. In contrast to normal chick embryos, those homozygous for the “scaleless” gene (Abbott and Asmundson, '57) display reduction in the number of papillae and underlying scleral ossicles (Palmoski and Goetinck, '70). SEM of the mutant conjunctival surface indicates that these papillae do not exhibit all of Murray's ('43) histological stages and are morphologically abnormal. Data from the present SEM study of the normal and scaleless conjunctiva are discussed in relation to those data of other investigators, and we suggest that Stage 4 in papillae development is critical to scleral ossicle formation.