bluuebunny/crossref_metadata_2025_split huggingface dataset:
Alterations in the fine structure of the rat epididymis after vasectomy
Authors: Flickinger Charles J. 
Published: February 2005

AbstractThe fine structure of the epldidymal epithelium of the rat was studied at intervals up to nine months after bilateral vasectomy, unilateral vasectomy, or a bilateral sham operation. Membranous material accumulated in the cytoplasm of the ‘light’ cells of the cauda epididymidis in greater amounts after bilateral vasectomy than following a sham operation. The membranes were found in apical vacuoles, in moderately dense membrane‐bounded bodies in the mid‐region of the cells, and, most prominently, in large infranuclear masses. These large infranuclear membranous masses had a polymorphic interior composed of granules and amorphous material as well as membranes, and thus morphologically resembled large lysosomes or residual bodies. In some instances readily dentifiable parts of sperm were found in apical vacuoles of epithelial cells after vasectomy. It is suggested that these changes may reflect the absorption of parts of sperm by the epithelium of the cauda epididymidis after vasectomy. The nature of the ‘light’ cells is discussed, and the results are compared with alterations in other species after vasectomy.
Spermatogenesis in the dog
Authors: Foote R. H. , Swierstra E. E. , Hunt W. L. 
Published: February 2005

AbstractThe cycle of the seminiferous epithelium of the dog was divided into eight stages, using as criteria the shape of the spermatid nucleus, the location of spermatids and spermatozoa in regard to the basement membrane, the presence of meiotic figures and the release of spermatozoa from the lumen of the tubule. Based upon these criteria, a modification of the eight‐stage system of classification of the cycle of the seminiferous epithelium was developed. Cell populations making up each stage are described. The relative frequencies of stages 1 through 8 were 21.9, 12.7, 2.8, 11.5, 8.3, 15.4, 13.3 and 14.0%, respectively. The duration of one cycle of the seminiferous epithelium was 13.6 days (SE ± 0.7), as determined from cells labeled by tritiated thymidine. The absolute durations of stages 1 through 8 were 3.0, 1.7, 0.4, 1.6, 1.1, 2.1, 1.8 and 1.9 days, respectively. The life span of primary spermatocytes was 20.9 days, of secondary spermatocytes 0.5 days, spermatids with round nuclei 10.5 days, spermatids with elongated nuclei up to the time they are released into the lumen, 10.6 days. Counts of the different types of spermatogenic cells in tubular cross sections revealed little or no germ cell degeneration during the two maturation divisions.
Evidence for refractoriness of the pituitary‐gonadal axis to the pineal gland in golden hamsters and its possible implications in annual reproductive rhythms
Authors: Reiter Russel J. 
Published: February 2005

AbstractThe testes of adult hamsters maintained in short daily photo‐periods (light:dark “LD” cycles of 1:23, in hours) undergo regression within ten weeks and spontaneous regeneration within about 30 weeks. Thereafter (at least up to 80 weeks), as long as these animals are kept in short photoperiods the gonads do not experience a second atrophic response. After the 30 week period of dark exposure, if the hamsters are moved into a long photoperiodic environment (LD 14:10) for either one or ten weeks and are then returned to short photoperiods, the gonads do not involute a second time. However, if the duration of exposure to LD 14:10 is increased to 22 weeks, the return to LD 1:23 causes the gonads to degenerate. The regressive responses of the testes never occur in hamsters that have been pinealectomized indicating that the observed changes are mediated by this gland. The inability of darkness and, thus the pineal gland, to induce a second gonadal involution unless the hamsters are maintained in LD cycles of 14:10 for 22 weeks (after a 30 week period of dark exposure) may be explicable in terms of (1), a transient refractoriness of the brain to the pineal antigonadotropic principle or (2), the temporary failure of the pineal to be activated by short daily photoperiods.
Spinal nerve root degeneration in aging laboratory rats: A light microscopic study
Authors: Gilmore Shirley Ann 
Published: February 2005

AbstractDegeneration of unknown etiology was noted in the spinal nerve roots of aging rats. These animals (Charles River CD® rats) were included in a study of long‐term effects of ionizing radiation. The initial lesion was a de‐myelination of an individual axon or a few, isolated, scattered axons in the ventral roots of rats between 18 and 20 months of age. As the lesion progressed, the dorsal roots showed involvement, and by 24 months the usual finding was marked degeneration in ventral roots with degenerative changes of a lesser degree in the dorsal roots. When degeneration was complete, connective tissue filled the regions normally occupied by neural tissue. The lesion was unrelated to the radiation procedure, occurring with equal frequency in both irradiated and non‐irradiated animals. Furthermore, lesions occurred with equal frequency in both males and females. The one factor to which the lesion appeared to be related was age since it was not observed in animals less than 18 months old but was seen in 66.7% of those between 18 and 20 months and in 96.0% of those older than 20 months. These data indicate that this lesion needs to be considered when using aging laboratory rats.
Vestibular ampullary structures in the pigeon: A scanning electron microscope overview
Authors: Landolt Jack P. , Young Eric R. , Correia Manning J. 
Published: February 2005

AbstractA scanning electron microscope (SEM) was used to explore the complex surface features of the ampullary structures in the vestibular apparatus of the pigeon. The depth perspective inherent in SEM microscopy enabled: 1. three‐dimensional views of major ampullary structures such as the crista ampullaris, eminentia cruciata, and the planum semilunatum; 2. identification of a tongue‐like structure, the “lingula,” that is part of the eminentia cruciata; 3. the observation that the base of the eminentia is a projection of the crista ampullaris and not a structural partition; and 4. evidence that the lingulae, together with the torus, partition the crista into two separate regions. Additionally, an examination was made of the surface topography of non‐sensory cells in the membranous ampulla.The morphology of the cells and gross ampullary structures observed with SEM are compared to those obtained using light microscopy and where advantageous, complimentary light photomicrographs are presented.
Transitional cells in the postnatal thyroid gland of the rat
Authors: Calvert R. 
Published: February 2005

AbstractIn two and four‐week old rats three types of follicles were observed: thyroid follicles made of follicular cells and C cells; ultimobranchial follicles (or cysts) and ducts composed of lumen‐bordering cells and subjacent cells; mixed follicles lined by follicular cells on one side and by lumen‐bordering cells on the other. Occasionally C cells were seen in the wall of mixed follicles. On their basal side the lumen‐bordering cells of mixed follicles were in direct contact with the wall of ultimobranchial ducts or cysts. In the wall of these ducts transitional cells were observed. One type had ultrastructural features of subjacent cells (i.e., hemidesmosomes) and of lumen‐bordering cells (i.e., pale cytoplasm and dispersed tonofilaments). Another type of transitional cell had hemidesmosomes and a deeply indented nucleus, like subjacent cells, but had accumulated slightly distended cisternae of rough‐surfaced endoplasmic reticulum and was displaying long slender microvilli, which is typical of follicular cells. A third type of cells were called “young follicular cells.” They contained slightly distended cisternal profiles of rough‐surfaced endoplasmic reticulum collected in one corner of the cells and few apical vesicles. However, their cisternae were less abundant, less distended and had a more restricted distribution than those found in mature follicular cells. Hence the subjacent cells of ultimobran‐chial ducts might possibly give rise to lumen‐bordering cells and to some follicular cells. The latter are associated with the lumen‐bordering cells in the formation of mixed follicles; at the beginning these new follicular cells seem less active than the mature follicular cells. The origin of C cells after birth is discussed.
Trout hepatoma: Fibrosis and lymphocytosis as suppressive mechanisms in the rainbow trout (Salmo gairdneri)
Authors: Wales J. H. , Sinnhuber R. O. 
Published: February 2005

AbstractFibrosis and lymphocytosis are common in aflatoxin‐induced hepatoma in rainbow trout. It is suggested that these reactions may control the growth of tumors and in some cases destroy them. Nearly all of the hepatomas we have observed are fibrotic to some extent. The extent of the fibrosis seems to be age dependent and in advanced cases fibrosis appears to have disorganized the tumors to a degree which we believe is suppressive. The lymphocytosis shows a negative correlation with the size and age of the hepatoma, being found almost exclusively in the very “early” (small) hepatomas and preneoplastic nodules. It is suggested that the invasion of the tumors by lymphocytes is a host defense mechanism.
The fine structure of granulosa cell nexuses in rat ovarian follicles
Authors: Merk Frederick B. , Albright John T. , Botticelli Charles R. 
Published: February 2005

AbstractAn intercellular junction known as the nexus has been identified in developing granulosa tissue of rat ovaries. Nexuses are common in Graafian follicles of mature cycling rats and in similar follicles of immature animals stimulated by exogenous gonadotrophins. The angle at which the plane of section intersects a nexus significantly governs its internal appearance. Within obliquely cut nexuses there is often a cross‐striated pattern of uniform lines in specimens prepared by conventional fixation and staining procedures. These lines could be significant because they may represent points of continuity between communicating cells.Two forms of nexuses are observed. The abutment form is found at cell surfaces, is continuous with plasma membranes, and is frequently associated with cell processes. The other form of nexus is ring‐shaped and appears free within the cytoplasm. These circular profiles probably represent transverse views through nexus‐girdled cell processes as well as nexus‐bound spheres which may have pinched off the processes. Since the profiles from the two sources are ordinarily indistinguishable, both are designated “annular nexuses” even though some may be cell inclusions. Lanthanum tracer can percolate into the central region of abutment nexuses but is absent from the large majority of annular nexuses, suggesting that many of them are isolated from the extracellular space. Reconstruction of serial sections reveals that some annuli are parts of cell inclusions. Sphere formation could be a means of removing nexuses from cell surfaces.
Fine structure of astrocyte mitochondria in the spinal cord of the dog, cat and monkey
Authors: Duncan Donald , Morales Ricardo 
Published: February 2005

AbstractAfter perfusion of the animals with buffered aldehyde solutions, spinal cords of normal dogs, cats and monkeys were prepared for electron microscopic examination by standard methods. Observations were limited to the upper cervical levels in all animals, except in two cats where thoracic and lumbar regions also were studied. Large mitochondria, up to 5.0 μ in diameter, are abundant in astrocytes that form a dorsolateral glial septum in dogs and cats. The septum is present but less well developed in monkeys and the accompanying large mitochondria are smaller and less numerous. These mitochondria have a moderately dense matrix and few or no cristae. They are accompanied by more numerous smaller mitochondria with similar matrix and prismatic cristae. The cristae are of constant size and shape in all three species but vary greatly in numbers and arrangement. It is suggested that local mechanical forces may be responsible for the configuration of these morphologically specialized mitochondria.
Fine structure of photoreceptors in the owl monkey
Authors: Murray Raymond G. , Jones Arthur E. , Murray Assia 
Published: February 2005

AbstractThe owl monkey (Aotes trivirgatus) differs from most primates in being nocturnal in habit and having primarily scotopic vision. Photoreceptor cells of the retina of this species were studied with the electron microscope and compared with corresponding cells of other primates. No striking qualitative differences were noted. Most of the receptors are typical rods, but approximately 5% are cones, based on the following features: shorter, tapering outer segments, discs with smooth rather than scalloped margins and with uniformly narrow internal spaces, the membranes of which in some cases are continuous with the plasma membrane; broad inner segments with numerous mitochondria; nuclei that lie immediately against the outer Junctional zone (outer limiting membrane) with relatively thick inner fibers leading to large pedicles in the floor of which are numerous typical “synaptic triads.” One relatively unusual feature of the rods is the prominence of the striated rootlets associated with the basal bodies of the cilium‐like connecting pieces. An apparently intimate relation of the rootlets to investing mitochondria, especially to their tubular internal cristae, is discussed with regard to the possibility of a function for the rootlet other than static anchoring of the cilium.
Lymphoid cells in the turtle bladder
Authors: Lefevre M. E. , Reincke U. , Arbas R. , Gennaro J. F. 
Published: February 2005

AbstractLymphoid nodules and diffuse lymphocytic infiltration are common in turtle urinary bladders. Nodules, usually located immediately beneath the epithelial layer, were found in 15 of 29 different hemibladders surveyed. A whole cross‐section of each hemibladder was examined in the survey. The nodules consisted of aggregates of dense lymphocytes without germinal centers. Erosion of the epithelial layer over the nodule was found in approximately one third of the cases. Scattered lymphocytes were abundant within the epithelial layer and were found in smears from the mucosal surface. Pyroninophilic cells resembling plasma cells were found in all regions of the bladder. Electron micrographs showed lymphocytes and plasma cells in the epithelial layer above the basement membrane.
Metabolic activity during the degenerative and early regenerative stages of minced skeletal muscle
Authors: Snow Mikel H. 
Published: February 2005

AbstractIn the rat, autotransplanted minced skeletal muscle undergoes degenerative changes prior to the regeneration of a whole muscle. In this study, both the degenerative and early regenerative processes were examined using histochemical procedures for the localization of glycogen, neutral lipid, phosphorylase, lactate dehydrogenase, cytochrome oxidase, glucose‐6‐phosphate dehydrogenase and non‐specific esterases. Glycogen and phosphorylase activity disappeared in all muscle fibers within 24 hours after mincing. Vascular injections of ink demonstrated that during the second to tenth days after mincing a central ischemic zone of degenerating minced muscle was surrounded by a vascularized zone of regenerating muscle. Lactate dehydrogenase staining persisted during the first week in the degenerating muscle fragments of the central zone. This latter histochemical observation was supported by quantitative evidence which showed that degenerating muscle isolated from the central zone of four day regenerates produced lactic acid in the presence of glucose. Cytochrome oxidase activity decreased rapidly in the degenerating muscle while succinic dehydrogenase persisted somewhat longer. Although non‐specific esterases and glucose‐6‐phosphate dehydrogenase activities were not significant in normal muscle, they were histochemically detectable in degenerating muscle during the first week. The capacity for anaerobic metabolism apparently persists in the degenerating minced muscle for several days; this energy source may be sufficient to maintain the myogenic cells in an environment of degeneration and ischemia until they become reassociated with a vascular supply.
Identification of neonatal grey lethal mice
Authors: Hollinshead M. B. , Schneider L. C. 
Published: February 2005

AbstractThe grey lethal mouse is an osteopetrotic mutant which cannot be identified by its external appearance (grey fur) until eight days of age and dies within one month of birth. Techniques for the identification of neonatal mutants would greatly facilitate study of the pathogenesis of osteopetrosis and its early treatment.Under hypothermal anesthesia, the left lower limbs of neonatal mice were amputated just above the knee joint. The external appearance of two day old amputated tibiae could be correlated with the external appearance of the mice at eight days of age. The diaphyses of normal tibiae appeared red under the dissecting microscope due to the presence of hemopoietic tissue occupying the central marrow cavity. Grey lethal tibiae appeared opaque because relatively more unresorbed bone occupied the center of the diaphysis.Histologic examination showed that in normal mice at birth, the mandibular incisor extended posteriorly to the molar region of the jaw, but that in grey lethals dense bone prevented the incisor from growing posteriorly in this fashion.
Electron microscopic and microradiographic investigation of a morphologic basis for the mineralization pattern in rat incisor enamel
Authors: Glick Paul L. , Eisenmann Dale R. 
Published: February 2005

AbstractAlthough it has been established that human enamel mineralization follows the incremental pattern of matrix secretion, microradiographic studies of rodent enamel still support a non‐incremental pattern of mineralization. This study examines the mineralization sequence using microradiography, as well as measurement of crystal size and distribution on electron micrographs of the various regions of rat incisor enamel. The microradiographic density pattern was found to correlate with the major regions of structural variation within the enamel. Measurement of crystals revealed a rather uniform positive gradation in their size from the surface to the dentino‐enamel junction, i.e., crystal size was found to be directly related to crystal age. Crystal distribution analysis demonstrated that an inner region of enamel contains a much larger volume of crystal‐free space than other areas. This is the same region which has been described as being out of step with an incremental pattern of mineralization, in that it is less dense than enamel either superficial or deep to it. It is concluded that mineral accretion follows the same incremental pattern in the rat incisor as in humans and that the misleading microradiographic image merely reflects a non‐homogeneous distribution of crystals.
The morphology of tadpole (Rana catesbeiana) liver under varying conditions of organ culture
Authors: Bennett Thomas Peter , Kreigstein Henry 
Published: February 2005

AbstractPrimary explants from Rana catesbeiana tadpole liver have been maintained in organ culture for six days using methods of cultivation which are described in detail. The organization and morphology of the cells in culture have been defined by light and electron microscopy. By adjustment of the experimental conditions of culture, after six days, the cells are morphologically identical to those freshly excised from tadpole liver. Soon after being put into culture, however, the chromatin of the nuclei becomes condensed, and only after about 30 hours in culture do the original euchromatic characteristics of the nucleus reappear. The effects of changes in the culture conditions on these morphological characteristics are presented.The system that has been developed is discussed with a view toward elucidating the basis of the cytological changes which occur during anuran metamorphosis.
Golgi impregnation study of a new catecholamine‐containing cell type in the toad hypothalamus
Authors: McKenna Olivia C. , Pinner‐Poole Betty , Rosenbluth Jack 
Published: February 2005

AbstractA population of catecholamine‐containing subependymal cells bordering the preoptic recess of the toad hypothalamus was studied by the rapid Golgi method to determine whether the cells have the characteristic contours of neurons or are instead secretory cells similar to peripheral chromaffin cells as proposed in an earlier study. Golgi impregnations of these cells reveal that they possess long basal processes which extend toward the lateral surface of the brain and which are covered with clusters of short projections and longer single projections. The relatively large caliber and rough surface of these processes distinguish them from axonal processes of neurons. Instead the cells closely resemble the ependymal cells bordering the preoptic recess with respect to the lateral course of the basal processes and with respect to the projections on these processes. The only qualitative difference between the ependymal and subependymal cells seen in Golgi preparations is the presence of apical processes projecting from the subependymal cell bodies through the ependymal layer to border on the ventricle. On the basis of this and the earlier study it is concluded that the subependymal cells do not have the characteristics of neurons but instead constitute a new cell type similar to ependymal cells but specialized for the synthesis, storage and secretion of catecholamines.
Cytokinesis in the rabbit zygote: Fine‐structural study of the contractile ring and the mid‐body
Authors: Gulyas Bela J. 
Published: February 2005

AbstractThe temporal events of cytokinesis were examined with light‐ and electron‐microscopes during first cleavage of the rabbit zygote. When karyokinesis is at the late anaphase‐to‐early‐telophase stage a shallow indentation appears in the vitelline membrane in a plane perpendicular to the spindle. Microvilli are absent in the indentation although present elsewhere. A band of microfilaments is recognizable under the plasma membrane of this region. Sections which pass through the band of microfilaments contain several early mid‐bodies located centrally in the egg. In later stages of furrowing the band of filaments is 0.1 μ wide and is circumferentially arranged. These filaments which underlie the broad leading edge of the furrow are 50–80 Å in diameter and are components of the contractile ring. The furrow cavity is filled with blebs of the plasma membrane. The microvilli of the lateral furrow walls interdigitate and “primitive” intermediate junctions develop between the two blastomeres. During late cleavage the stem‐bodies fuse into a continuous mid‐body which spans two opposite points of the intercellular bridge and fuses with the filaments of the contractile ring.
Casting the lungs in‐situ
Authors: Phalen Robert F. , Yeh Hsu‐Chi , Raabe Otto G. , Velasquez David J. 
Published: February 2005

AbstractA method for producing flexible silicone rubber casts of the airways of the lungs in‐situ is described. Casts are made to correspond to lung volumes occurring during normal breathing. The lung is prepared for casting by replacing the air within with CO2 followed by filling with degassed physiological saline. The saline dissolves the CO2 gas within the airways allowing for a bubble‐free finished cast. Casting compound is then slowly injected through the trachea. The saline diffuses out of the lung and passes out of the thorax through several small slits in the thoracic wall. After the injection is completed, the cast lung is allowed to cure in‐situ before it is removed and the tissue digested away. Finished casts have an overall shape corresponding closely to the shape of the thorax. Casts produced by this in‐situ method appear to have more realistic geometrical relationships than those produced from excised lungs.