bluuebunny/crossref_metadata_2025_split huggingface dataset:
C‐type virus‐lymphocyte interactions in developing mouse thymus
Authors: Koppenheffer Thomas L. , Phillips Joseph H. , Vankin G. Lawrence 
Published: February 2005

AbstractThe appearance of C‐type virus particles in thymus cells of Swiss mouse embryos, 11.5 to 15.5 days post‐conception age (PCA), was studied with the electron microscope. In thymic rudiments of all specimens examined, virus particles were seen in epithelial cytoplasm, budding from epithelial cell surfaces and in extracellular spaces. Lymphoid cells were first seen in thymic rudiments of 13.5 days PCA, and did not display virus particles at this stage. At 14.5 days PCA, thymic lymphocytes had localized plasmalemmal thickenings of high electron‐density which were adjacent to extracellular virus particles. Viruses appeared to be penetrating thymic lymphocytes by viropexis in embryos of 15.5 days PCA. At this stage, many lymphocytes also had cytoplasmic virus‐containing vesicles and viral buds at their surfaces. These observations suggest the possibility that, in embryos, C‐type I viruses are transmitted horizontally from thymic epithelium to early populations of thymic lymphocytes.
Cytology and distribution of secretory cell types in the mouse hypophysis as demonstrated with immunocytochemistry
Authors: Baker Burton L. , Gross Douglas S. 
Published: February 2005

AbstractSince differential chemical staining has been unsatisfactory for demonstration of specific secretory cell types in the hypophyseal pars distalis of the mouse, the objective of this study was to determine whether the peroxidase‐antiperoxidase immunocytochemical procedure might be more effective. Accordingly, representative sections from the hypophyses of 17 female and 15 male adult mice of the Swiss‐Webster strain were immunostained, 16 antisera to 5 pituitary hormones or their subunits being utilized. Five secretory cell types were demonstrated. Somatotropes were ovoid to spheroidal and distributed quite generally in the gland except for the “sex zone” where they were scarce. Somatotropes were larger and more numerous in the male than in the female. Mammotropes were polyhedral and also generally distributed in the gland except for the “sex zone” where few were observed. Mammotropes were larger and more numerous in the female than in the male. Corticotropes were small, stellate and few. They were most common near the ventral surface of the gland and formed bilateral centromedial groups in the lateral wings. Thyrotropes were usually large and polyhedral. They were restricted almost solely to the ventral region of the pars distalis. Gonadotropes were polyhedral, and generally distributed, except for aggregation in the cephalomedian “sex zone.” Most gonadotropes appeared to contain both luteinizing hormone and follicle‐stimulating hormone. Thus, all secretory cell types recognized in other species can be demonstrated readily in the mouse hypophysis with immunocytochemistry.
Ultrastructural identification of afferent fibers of cardiac origin in thoracic sympathetic nerves in the dog
Authors: Seagard Jeanne L. , Pederson Harlan J. , Kostreva David R. , Van Horn Diane L. , Cusick Joseph F. , Kampine John P. 
Published: February 2005

AbstractWhile cardiac afferent nerve activity has been recorded from the ventrolateral (VLCN) and ventromedial (VMCN) cardiac nerves, left dorsal and ventral ansae subclaviae, and left upper thoracic white rami communicantes, little anatomical evidence for the existence of afferent fibers in these nerves has been reported. This study was designed to characterize the normal ultrastructure of the above nerves and to identify afferent fibers in them through Wallerian degeneration produced by dorsal root ganglionectomy. Laminectomies followed by dorsal root ganglionectomies were performed on left thoracic roots T1‐T4 in six mongrel dogs. The nerves to be examined were removed from two animals at 1, 2, and 3 weeks following ganglionectomy and prepared for electron microscopy. Control nerves were obtained from two normal dogs. Degenerating nonmyelinated fibers were characterized by watery axoplasm containing clumps of electron‐dense material. Degenerating myelinated fibers were distinguished by the separation of their myelin lamellae, producing characteristic whorls. After three weeks, afferent nonmyelinated axons had degenerated in all nerves, leaving only layered processes of Schwann cells in these areas. Approximately 5–15% of the fibers in each nerve degenerated, indicating their afferent nature. Of these fibers, 85–90% were nonmyelinated C fibers and the remainder myelinated Aδ fibers. These results indicate participation of both Aδ fibers and a large population of C fibers in transmission of cardiac afferent activity.
Structure of the chicken's inner ear: SEM and TEM study
Authors: Tanaka Katsuhiko , Smith Catherine A. 
Published: February 2005

AbstractThe inner ears of 35 adult chickens were studied by TEM, SEM and light microscopy. Two well differentiated hair cell/nerve ending units were present: tall hair cells with small vesiculated nerve endings were located on the attached part of the basilar membrane; short hair cells with large vesiculated nerve endings were located on the free basilar membrane except for the distal tip. In this respect the chicken ear is similar to that of the pigeon. The chickens examined did have some unique features. Sensory cells of lenticular and hemispheric shape were also present at the proximal end. Bundles of long dense tubules were seen frequently within the sensory cell cytoplasm. Kinocilia were absent from the hair bundles of many of the sensory cells. The internal structure of the kinocilia which were present was atypical and consisted of a variable number of doublets. Eight peripheral plus one central doublet were found most frequently.
The fine structure of the ventricular surface of the area postrema of the cat, with particular reference to supraependymal structures
Authors: Leslie R. A. , Gwyn D. G. , Morrison C. M. 
Published: February 2005

AbstractThe ependymal surface of the feline area postrema (AP) has been examined with the scanning and transmission electron microscopes. Particular attention was paid to the distribution and structure of supraependymal (SE) cells which have not been described before on this organ. A population of SE cells was found consistently on the cat AP; they were grouped most frequently toward the caudal aspect of the organ. Their structure bears a great resemblance to that of macrophages, containing: (1) many small apical vacuoles, (2) numerous lysosomes, and (3) phagosome‐like bodies. Arrays of microvillous tufts and also singly‐occurring microvilli are features of the unciliated ependymal surface of the organ. Tufts are often found in very close proximity to superficial blood vessels which are characteristically surrounded by large perivascular spaces.
The cochlear nuclei in man
Authors: Moore Jean Kavanagh , Osen Kirsten Kjelsberg 
Published: February 2005

AbstractThe human cochlear nuclei are composed of a ventral and a dorsal nucleus which are similar, though not identical, in their cytoarchitecture to those of other mammals. The ventral cochlear nucleus (VCN) consists of a rostral area of spherical cells, a central area of multipolar and globular cells, a posterior area of octopus cells, and a laterodorsal cap of small neurons. The interareal boundaries are less distinct in man than in the cat. The central region of multipolar cells and the cap area of small cells constitute the bulk of the human VCN. The spherical, globular, and octopus cells appear relatively less numerous in man than in other mammals. The dorsal cochlear nucleus (DCN) in man is relatively large, but lacks the typical stratification seen in other mammals, with only vestiges of the granular and molecular layers remaining. Virtually the entire DCN consists of an area of cochlear fiber neuropil containing pyramidal cells, small neurons, and occasional giant cells. The pyramidal cells have lost their typical radial orientation and lie scattered within the cochlear neuropil. Thus the entire human DCN may be equivalent to layers 2 and 3 of this nucleus in other mammals. In spite of the relatively large DCN, the acoustic striae appear small. This is in contrast to the large trapezoid body leaving the VCN. Intrinsic and descending fiber pathways to the cochlear nuclei are not clearly defined and may be less prominent in man than in the cat.
Morphogenesis of the truncus arteriosus of the chick embryo heart: The formation and migration of mesenchymal tissue
Authors: Thompson Robert P. , Fitzharris Timothy P. 
Published: February 2005

AbstractThe appearance and migration of mesenchymal cushion tissue within the truncus arteriosus of the normal 2.5‐to 6‐day chick embryo heart was surveyed systematically with the light microscope. Series of cross‐sections taken from replicate hearts at successive developmental stages allowed comparison of the following qualitative and quantitative aspects of early truncal morphogenesis. Mesenchyme within the truncus was derived from two distinct sources. The first mesenchyme appeared to migrate caudally into the cardiac jelly of the distal truncus from the nearby aortic arch region, coincident with slowing of the anterior elongation of the heart tube (Hamburger‐Hamilton Stage 17–18). A second, separate mesenchymal population, derived from endocardium, began to fill the conus and proximal truncus in a radial direction, coincident with expansion of the bulbus cordis (Stage 12–19). The measured kinetics of relative cell numbers, distributions, and mitotic indices suggest substantial contributions from both sources. By Stage 26, the conotruncal region was filled with mesenchyme, which then condensed to form the anlagen of three future structures: the semilunar valves, the aorticopulmonary septum, and the tunica media of the great arteries.
Morphogenesis of the fetal membranes of an American mole, Scalopus aquaticus
Authors: Prasad M. R. N. , Mossman H. W. , Scott G. L. 
Published: February 2005

AbstractScalopus membranes are characterized by: Superficial nidation; antimesometrial orientation of the embryonic disc; amniogenesis by folding; an extensive but transitory choriovitelline placenta; a large yolk sac with late and incomplete inversion; large persistent allantoic vesicle; a very broad, thin, villous, epitheliochorial chorioallantoic placenta of annular shape interrupted mesometrially, dotted with numerous areolae, and bordered by a non‐villous sparsely vascular chorioallantoic membrane connected with the persistent bilaminar omphalopleure by a very narrow rim of chorion. There is no decidua. Electron microscopy shows that at 8 mm, CR, (limb bud embryo) the uterine epithelium of the interhemal membrane may be 0.5 μm or less in thickness, but that it shows no signs of degeneration. Trophoblastic microvilli often penetrate the epithelium to within 0.2 μm of its base. At this time there is active secretion by the uterine glands, and cellular hypertrophy and cytolysis of the epithelium at the gland mouths, with active phagocytosis by the areolar cytotrophoblast. The occurrence of absorptive areolae in an insectivore emphasizes the probable primitiveness of this widely distributed placental mechanism. In spite of similarities of the yolk sac to that of rabbits and rodents, the bilaminar omphalopleure produces no invasive trophoblastic giant cells. The definitive membranes of Parascalops breweri and Scapanus latimanus are like those of Scalopus. The placentae of Talpa europaea, Condylura cristata, and Neurotrichus gibbsii are discoid and relatively much smaller, thicker and more complex in internal structure. There is some reason to believe that the fetal membrane systems of moles and shrews (Soricoidea) are more like those of the ancestral mammalian stock than are those of any other recent eutherians.
Loss of thick filaments from fast‐twitch glycolytic muscle fibers of the pigeon pectoralis after chronic administration of dantrolene sodium
Authors: Silverman Harold , Hikida Robert S. , Staron Robert S. 
Published: February 2005

AbstractAdult pigeons received dantrolene sodium, a skeletal muscle relaxant which blocks the release of calcium during excitation‐contraction coupling, for 12 to 16 weeks. The pectoralis muscles of these birds were analyzed for changes occurring in the various fiber types of the muscle. Both histochemistry (ATPase and SDH activity) and electron microscopy (mitochondrial and lipid volume percentages) differentiated two fiber types. The two fiber types consisted of fast‐twitch glycolytic fibers (FG) and fast‐twitch oxidative‐glycolytic (FOG) fibers. After dantrolene treatment some FG fibers showed little or no ATPase activity. Dantrolene treatment also produced a disappearance of thick filaments in some FG fibers. We infer that the fibers without thick filaments are the ones lacking ATPase activity. The FOG fibers were nearly normal. Since drug‐fed birds lose weight, a few birds were starved to determine whether the filament loss was related solely to the bird's loss in weight. No fibers in starved birds showed reduced ATPase activity or loss of thick filaments. In fibers that showed thick filament disappearance, the I‐bands remained organized and intact, suggesting that the I‐band maintains its integrity without interaction with the thick filaments. Changes in activity patterns may cause loss of thick filaments by inhibiting either their synthesis or assembly.
The habenular nuclei of the elasmobranch “Scyllium stellare”: Myelinated perikarya
Authors: Kemali Milena , Miralto Antonio 
Published: February 2005

AbstractSome habenular cells of the elasmobranch, Scyllium stellare, have a perikaryon completely enveloped by myelin of the compact type. They are found only in the left habenula and not in the right. The myelin sheath accompanies the proximal segment of the process arising from the perikaryon, in a node of Ranvier‐like pattern. The identity of these myelinated cells and the functional significance of their myelination are unknown.
The prism pattern of rat molar enamel: A scanning electron microscope study
Authors: Risnes Steinar 
Published: February 2005

AbstractRat molar enamel has been studied by sectioning the enamel along various planes, and observing the etched surfaces in the SEM. It was found that the prism pattern was much more variable than in rat incisor enamel. Regions without prism decussation seemed to dominate in the occlusal half of the molars. Where present, prism decussation was of the uniserial lamellar type, but it varied considerably in distribution, extent, and distinctness. Prism decussation seemed to have a predilection for the cervical enamel, and was almost absent in the enamel on the occlusal surface.The interprismatic substance showed a characteristic configuration: In the inner enamel it appeared in the form of radially oriented sheets, which tended to delimit radially directed, single lines of prisms. In regions with prism decussation these single lines of prisms encompassed prisms belonging to different prism lamellae. In the outer part of the enamel the interprismatic substance exhibited a honeycomb appearance.The similarities and differences between the prism patterns of rat incisor and molar enamel may be of importance for understanding the mechanisms of amelogenesis, especially for the recognition of factors controlling the movement of ameloblasts.
Observations on the inter‐relationships of Sertoli cells at the level of the blood‐testis barrier: Evidence for formation and resorption of Sertoli‐Sertoli tubulobulbar complexes during the spermatogenic cycle of the rat
Authors: Russell Lonnie D. 
Published: February 2005

AbstractStructures termed tubulobulbar complexes are known to be formed by adjoining Sertoli cells at the level of the blood‐testis barrier (Russell and Clermont, 1976). Here, long (2–4 μm) tubular evaginations of one Sertoli cell, which end in bulbous dilations, are seen in corresponding invaginations of a neighboring Sertoli cell. In most regions of the tubular and bulbous portions of the complex, the Sertoli plasma membranes were found to be separated by a 4–5‐nm intercellular space, but in some areas the membranes converged to form tight and gap junctions. The numbers, distribution and properties of tubulobulbar complexes were studied in relation to the cycle of the seminiferous epithelium. From the data obtained it was concluded that tubulobulbar complexes develop and undergo regressive changes during the spermatogenic cycle. Most complexes arise during the early stages of the cycle (Stages II‐V) and develop large bulbous endings. Developing tubulobulbar complexes consist of short evaginations of one Sertoli cell which face a bristle‐coated pit of the opposing Sertoli cell. At midcycle (Stages VI‐VII) most show regressive changes and are eventually resorbed as a consequence of the action of nearby Sertoli lysosomes. Once resorbed, the probability of seeing a tubulobulbar complex in thin sections decreases from 4‐ to 8‐fold. The few tubulobulbar complexes which remain past this period (Stages VII‐XIV‐I) usually lack bulbous endings and are frequently seen above type A spermatogonia. The data suggest that small fragments of cytoplasm and plasma membrane (including junctional surfaces) are lost from one Sertoli cell as a result of the degradative processes occurring in a neighboring Sertoli cell. Tubulobulbar resorption is discussed in relation to the impending breakdown of the blood‐testis barrier above spermatocytes as these cells move upward. The possible significance of the cyclic resorption of tight and gap junctional sites between Sertoli cells is also discussed.
Density variation in the humeral cortex of Macaca
Authors: Burr David B. 
Published: February 2005

AbstractThe purpose of this research was to describe patterns of density variation throughout the cortex of the humeral shaft in Macaca and to attempt to explain these variations in terms of the gross anatomy and mechanical function of the bone. One hundred ninety transverse sections were taken from five sites along the humeral diaphyses of 38 Macaca. The density at eight positions around each section was measured using radiographic and densitometric techniques. Analysis of variance indicated significant (p < 0.02) differences among cross‐sectional levels and positions within each level. No sexual dimorphism in density could be demonstrated, although sexual dimorphism in density has been reported for the femora of this same sample. This relationship between humerus and femur parallels that found in humans. Density increased distally in the humerus, probably due to major areas of muscle attachment. Comparison with similar data from the femur of Macaca indicated unexpected differences in density pattern which may underlie differences in the strength and mechanics of the upper and lower extremities.
A route for direct retinal input to the preoptic hypothalamus: Dendritic projections into the optic chiasm
Authors: Silver Jerry , Brand Scott 
Published: February 2005

AbstractWith the use of Golgi, horseradish peroxidase, and electron microscopic techniques, neurons within a broad region of the preoptic hypothalamus of the mouse were shown to have dendrites that projected well into the depths of the optic chiasm. Further experimental and ultrastructural investigation demonstrated synapses between these dendrites and retinal axonal boutons within the chiasm. All synapses located in the chiasm were classified as Gray's type I. The possible function of these dendritic projections is discussed.
Cephalic neurulation and optic vesicle formation in the early mouse embryo
Authors: Kaufman Matthew 
Published: February 2005

AbstractThe overall pattern of cephalic neurulation and the concomitant early development of the optic vesicles in mouse embryos were examined by scanning electron microscopy. Paraffin‐sectioned specimens were also examined.The overall pattern of closure of the cephalic neural folds accords well with earlier observations of this process. The earliest indication of optic placode formation was seen in histological sections of embryos at the 4‐ysomite stage, while optic pit formation was first observed at the 5‐ to 6‐somite stage. The upper halves of the optic vesicles were formed in 10‐ to 15‐hsomite embryos by the fusion of the neural folds at the junction between the mesencephalon and prosencephalon, while closure of the lower halves was associated with the closure of the rostral neuropore, and was usually completed by about the 20‐somite stage.By the 25‐ to 30‐somite stage, a rapid increase in the volume of the forebrain was observed, so that the optic vesicles were displaced laterally. An overall increase in the volume of the optic vesicles and decrease in the diameter of the optic stalks were also observed at this time. This account of cephalic neurulation and optic organogenesis provides useful baseline data relevant to the study of the normal early development of the mouse. A comparison is made between similar events in the rat, the hamster, and the human embryo.
Mode of action of cortisol on bone resorption in fetal rat fibulae cultured in vitro
Authors: Liskova‐Kiar Marie 
Published: February 2005

AbstractSeveral concentrations of cortisol (10‐8 to 10‐6 M) were tested for their ability to inhibit the spontaneous or parathyroid extract‐induced (PTE) bone resorption in organ cultures of 19‐day‐old fetal rat fibulae. The criteria used for the assessment of bone resorption were: the release of 45Ca from pre‐labeled bone rudiments into the culture medium, the dry weight and the number of osteoclasts per bone. At a dose of 10‐6 M, cortisol diminished significantly the release of 45Ca from fetal fibulae. This inhibition was accompanied by an increase in bone dry weight and by reduced numbers of osteoclasts. PTE, alone, caused extensive bone resorption with numerous osteoclasts and enhanced 45Ca release, without weight gain. This resorptive action of PTE was partially suppressed by cortisol at a dose of 10‐6 M. Lower concentrations were ineffective. Radioautographic studies with 3H‐thymidine revealed that cortisol restricts the recruitment of osteoclasts from osteoprogenitor cells, without decreasing the potential of precursor cells to form osteoblasts. PTE, however, stimulates the proliferation of progenitor cells and favors their differentiation towards osteoclasts. This effect can be suppressed by cortisol. It is concluded that cortisol inhibits bone resorption in vitro by limiting the ability of precursor cells to form osteoclasts. Moreover, our study shows that, in fetal rat bones cultured in vitro, osteoclasts arise from locally proliferating mononucleated precursor cells.
Establishment of an epithelial cell line from rat thymus
Authors: Itoh Tsunetoshi 
Published: February 2005

AbstractA cell line (IT‐26R21), composed only of epithelial cells, was established from normal rat thymus. Thymuses were treated with both collagenase and trypsin. Four months after the initiation of cultures, epithelial cells in packed colonies formed a monolayer and no other cells were found in cultures. Thereafter, epithelial cells have been subcultured with trypsin and EDTA, and are currently at the 30th subculture.Based upon the fine structure of the thymus in vivo, IT‐26R21 cells were identified as epithelial cells from the thymus, because of their mosaic‐like arrangement, desmosomes and tonofilaments. Other features also supported their origin and identity.