bluuebunny/crossref_metadata_2025_split huggingface dataset:
Desmosome‐like junctions between Sertoli and germ cells in the rat testis
Authors: Russell Lonnie 
Published: February 2005

AbstractDesmosome‐like junctions between Sertoli cells and germ cells (spermatogonia, spermatocytes and non‐elongate spermatids) were observed in the adult rat testis. At all levels, certain features were characteristic of this relationship, the most prominent being a densification of the subsurface aspect of the plasma membranes of each cell. The Sertoli cell counterpart demonstrated an abundance of cytoplasmic fibrils which converged on the density, but no such feature was evident in the germ cell counterpart. The width of the intercellular space was variable, ranging in some regions from approximately 3–5 nm, to other regions of approximately 14–18 nm, the latter being representative of most areas of contact. A poorly represented, and often discontinous, intermediate dense line was observed in the intercellular space. Hypertonic fixative solutions containing dextrose were utilized to provoke tissue shrinkage and exaggeration of the intercellular space within the basal compartment of the testis. Cell separation was evident over most regions of the cells, except where desmosome‐like contacts were present. Forces transmitted from one cell to another at desmosome‐like contacts resulted in tearing of cellular fragments, while junctional regions of both cells remained intact. These observations indicate that desmosome‐like junctions are strong adhesive sites between germ cells and Sertoli cells.
Movement of spermatocytes from the basal to the adluminal compartment of the rat testis
Authors: Russell Lonnie 
Published: February 2005

AbstractThe progressive movement of primary spermatocytes from the basal to the adluminal compartment of the seminiferous tubule was studies after testes were fixed with standard and hypertonic solutions. In stages VI, VII and VIII of the cycle (classification of Leblond and Clermont, '52), preleptotene spermatocytes were observed within the basal compartment of the seminiferous tubule. Resting on the basal lamina, these cells were bound tightly to neighboring Sertoli cells by desmosome‐like junctions. In late stage VIII and early stage IX, basal processes of Sertoli cells were observed between the newly formed leptotene cells and the basal lamina, and in stage IX, the Sertoli processes met to form a junction of the zonula adherens type. This junction formed a permeability barrier which restricted the free access of fixative into the spaces around leptotene cells. Evidence for this was found in the absence of the shrinkage artifact produced with hypertonic solutions in earlier stages. In longitudinal sections, the permeability barrier was first observed in an area of the tubule in which sperm release was also taking place. In mid‐ stage IX and in stage X, Sertoli‐Sertoli junctional specializations formed de novo below the leptotene spermatocyte, while those from the preceding stages, present above the leptotene spermatocytes, remained intact. Thus, tight junctions were in evidence for a considerable period of the time, both above and below the leptotene spermatocytes. At no time in the process of germ cell movement toward the lumen did these cells exhibit evidence of amoeboid movement or lose desmosome‐like contacts with the surrounding Sertoli cells.From this study it is concluded that the Sertoli cells play an active role in the transfer of spermatocytes to the adluminal compartment. A transient intermediate compartment of the seminiferous tubule is described, one which allows for the continual maintenance of the blood‐testis barrier during transit of spermatocytes from the basal to the adluminal compartment.
Morphological and histochemical organization of the flexor carpi radialis muscle in the cat
Authors: Gonyea W. J. , Ericson G. C. 
Published: February 2005

AbstractMost studies concerning the structure and function of skeletal muscle have utilized the hind limb of the experimental animal. However, it has been shown that the number of behavioral tasks performed by the cat's forelimb is greater than that of the hind limb. In addition, the forelimb muscles exhibit a functional complexity not observed in hind‐limb musculature. The purpose of this study was to investigate the distribution of fast‐twitch and slow‐twitch muscle fibers and muscle spindles in the flexor carpi radialis muscle (FCR) and to correlate the distributional patterns in these structures with muscle tendon architecture and muscle function. It was found that the FCR, a wrist flexor, contains 37% slow‐twitch fibers and 63% fast‐twitch fibers. However, the slow‐twitch fibers were concentrated in the deep region located between the tendons of origin and insertion, while the fast‐twitch‐glycolytic fibers were concentrated more peripherally. Muscle spindles were associated with the slow‐twitch region and were never found in the region containing high concentrations of fast‐twitch‐glycolytic fibers. Fast‐twitch‐oxidative‐glycolytic fibers were uniformly distributed throughout the muscle. It is proposed that the association of muscle spindles with slow‐twitch fibers and the differential distribution of muscle fibers into slow‐twitch and fast‐twitch regions might allow these regions to function independently of one another when called upon to perform complex behavioral tasks.
Arrangement of connective tissue components in the walls of seminiferous tubules of man and monkey
Authors: Hermo L. , Lalli M. , Clermont Y. 
Published: February 2005

AbstractIn primates the membrane separating the seminiferous epithelium from the interstitial space is composed of one to three (monkey) or two to six layers (man) of myoid cells associated with one to two layers of fibrocyte‐like adventitial cells. All these cells are separated from each other by irregular spaces filled with various connective tissue intercellular components. Subjacent to the elements of the seminiferous epithelium is a continuous, often redundant, basement membrane. A similar basement membrane‐like material forms a layer next to and over small areas of the plasma membrane of myoid cells. Collagen fibrils grouped in bundles of various sizes are seen in all connective tissue layers but are particularly abundant in the space between the seminiferous epithelium and the innermost layer of myoid cells. Elastic fibrils demonstrated by the Verhoeff iron hematoxylin technique are also present. Composed of a homogeneous material, the elastic fibrils are short, irregular, branching entities with a diameter comparable to or smaller than that of collagen fibrils. In addition, an abundance of microfibrils with a diameter of 12–15 nm is present in the various connective tissue layers. These microfibrils have a densely stained cortex and a lightly stained core. When seen close to the myoid cells, bundles of microfibrils appear to insert on well defined areas next to the plasma membrane. These areas commonly face the patches of electron‐dense material observed on the inner aspect of the plasma membrane of the myoid cells and in which the actin filaments are inserted. Bundles of microfibrils often span the gap between myoid cells of the same layer as well as those of adjacent layers. Microfibrils are also closely related to the surface of elastic fibrils and are seen intertwining with collagen fibrils. Thus microfibrils appear to bridge and bind together adjacent myoid cells and anchor the surface of these cells to the bundles of elastic and collagen fibrils present in the intercellular spaces of the limiting membrane.
An electron microscopic study of absorption of peroxidase conjugated immunoglobulin G by guinea pig visceral yolk sac in vitro,
Authors: King Barry F. 
Published: February 2005

AbstractIn the guinea pig and some other animals, passive immunity is conferred on the developing fetus by passage of immunoglobulin from mother to fetus across the yolk sac. In order to examine the cytological pathway involved in immunoglobulin transport, guinea pig visceral yolk sacs from late in gestation were exposed in vitro to peroxidase‐conjugated guinea pig immunoglobulin G (IgG‐HRP). Tissue was then fixed, incubated to show the site of localization of peroxidase reaction product and prepared for electron microscopy. The results suggested that the first step in the uptake of IgG‐HRP by yolk sac is attachment of the protein to the surface coats of endocytic invaginations at the apical surfaces of the endodermal cells. The endocytic vesicles then appear to pinch off from the surface and move deeper into the cytoplasm. Some of the small endocytic vesicles fuse with large apical vacuoles, which often contain large amounts of reaction product. Other small endocytic vesicles pinch off from the surface, move deeper into the cytoplasm and fuse with the lateral plasmalemma; their protein content is emptied into the intercellular space by exocytosis. From the intercellular spaces the protein presumably diffuses across the basement membrane and connective tissue spaces and enters the vitelline capillary bed. It is postulated that the latter cellular pathway, involving small vesicles and the intercellular spaces, is utilized by those immunoglobulins which are transferred intact across the yolk sac endoderm.
The effect of large unilateral cortical lesions on rubrospinal tract sprouting in newborn rats
Authors: Castro Anthony J. , Clegg Denis A. , McClung J. Ross 
Published: February 2005

AbstractMany previous reports have demonstrated the development of aberrant neural connections in response to neonatal brain lesions. This investigation was undertaken to study possible alterations, particularly axonal sprouting, in rodent rubrospinal projections after neonatal destruction of the corticospinal tract through frontal cortical ablation. The neonatal ablations were made by aspiration in 1 to 2‐day‐old rats under hypothermic anesthesia. At three to six months after neonatal surgery, the rubrospinal tracts were ablated bilaterally in these same animals as well as in controls, by stereotaxically transecting the ventral tegmental decussation. Animals were killed two to six days after adult surgery, and rubrospinal projections were demonstrated using the Fink‐Heimer degeneration stain. No differences in the pattern of rubrospinal projections were observed between animals with neonatal cortical lesions and controls. In all animals rubrospinal projections were located primarily in Rexed's lamina VI with a slight distribution into lamina V and the dorsal portion of lamina VII. Various hypotheses explaining the lack of rubrospinal sprouting after neonatal cortical lesions are presented, along with possible experiments to test these hypotheses.
The comparative fine structure of the interhemal membrane of chorioallantoic placentas from six genera of myomorph rodents
Authors: King Barry F. , Hastings Richard A. 
Published: February 2005

AbstractIn order to extend the cytological information available on the structure of the interhemal membrane in cricetid rodents, in particular, and myomorph rodents, in general, we have examined the fine structure of the placental labyrinth in five genera of cricetid rodents (Lemmus, Dicrostonyx, Clethrionomys, Microtus and Peromyscus) and one genus of murid rodent (Acomys). Small pieces of labyrinth from near‐term placentas were fixed in glutaraldehyde and osmium tetroxide and processed for electron microscopy. The interhemal membranes of all the species examined were hemotrichorial. The outermost layer of trophoblast, bordering the maternal blood spaces, was celular and often contained some patent fenestrae, whereas the middle and inner trophoblastic layers were apparently syncytial. The outermost trophoblastic layer of all the species contained abundant granular endoplasmic reticulum. The intercellular space between the outer and middle layers was variable in width, primarily due to the complex folding of the surface of the middle layer. The surfaces of the middle and inner layers were closely apposed. The middle trophoblastic layer in several species contained filamentous “glomerular bodies” and the innermost layer, particularly of Peromyscus, contained smooth membranous whorls. A basal lamina separated the innermost trophoblastic layer from the fetal capillary endothelium. The endothelial cells in most of the species contained fenestrated regions. These observations are compared to those on other hemochorial placentas, and common features of cricetid (and myomorph) rodent placental fine structure are emphasized.
Regeneration of tooth development in vitro following sodium fluoride treatment
Authors: Kerley Michael A. , Kollar Edward J. 
Published: February 2005

AbstractMandibular incisors were dissected from the jaws of 15‐ and 16‐ days C57BL/10 mouse embryos and cultured on agar‐solidified Eagle's basal medium supplemented with fetal calf serum, an antibiotic, and glutamine. The experimental medium was the same as the control except that fluoride was added such that the final concentrations ranged from 2.0‐8.0 mM NaF. Control and experimental explants were recovered after two, four and six days of incubation and studied histologically. After two days of fluoride treatment (3.0 mM NaF), cellular degeneration was observed in the dental papilla mesenchyme while the enamel organ epithelium appeared more resistant. Prolonged treatment or treatment at higher concentrations resulted in destruction of the dental papilla. The enamel organ was still present but was abnormal and reduced. Older tooth germs were less affected overall when incubated at the same fluoride dosage and time of treatment. When explants subjected to limited exposure (2 days) to fluoride were placed on control medium, the suppressed tooth germs recovered. The recovery was enhanced by grafting untreated mesenchyme to the treated explants followed by incubation on control medium. The observations indicate that NaF can suppress the development of tooth germs in vitro and that recovery from the suppresion does occur. The more severe inhibition observed in the mesenchymal component when compared to the response of the epithelial component of the treated explants suggests that fluoride may alter the ultimate morphology of the tooth crown by disrupting the normal epithelial‐mesenchymal interaction which occurs during early tooth development.
Pathogenesis of osteopetrosis in the microphthalmic mouse: Reduced bone resorption
Authors: Marks Sandy C. 
Published: February 2005

AbstractBone resorption, stimulated by injection of parathyroid extract, was measured in vivo in microphthalmic mice as the rate of release of 3H from bone after incorporation of 3H‐proline. Bone resorption in these mice, which inherit osteopetrosis, was less than 10% of that in normal littermates. Autoradiography confirmed the reduction in removal of radioactive bone matrix and in bone growth in microphthalmic mice. The ability of these mice to raise the serum calcium concentration in response to PTE was also reduce. These results, that bone resorption is reduced in microphthalmic mice, are discussed in relation to the pathogenesis and cure of the disease.
Three‐dimensional studies of resorption spaces and developing osteons
Authors: Tappen N. C. 
Published: February 2005

AbstractResorption spaces and their continuations as developing osteons were traced in serial cross sections from decalcified long bones of dogs, baboons and a man, and from a human rib. Processes of formation of osteons and transverse (Volkmann's) canals can be inferred from these three‐dimensional studies. Deposits of new osseous tissue begin to line the walls of the spaces soon after termination of resorption. The first deposits are osteoid, usually stained very darkly by the silver nitrate procedure utilized, but a lighter osteoid zone adjacent to the canals occurs frequently. Osteoid linings continue to be produced as lamellar bone forms around them; the large canals of immature osteons usually narrow very gradually. Frequently they terminate both proximally and distally as resorption spaces, indicating that osteons often advance in opposite directions as they develop. Osteoclasts of resorption spaces tunnel preferentially into highly mineralized bone, and usually do not use previously existing canals as templates for their advance. Osteons evidently originate by localized resorption of one side of the wall of an existing vascular channel in bone, with subsequent orientation of the resorption front along the axis of the shaft. Advancing resorption spaces also apparently stimulate the formation of numerous additional transverse canal connections to neighboring longitudinal canals. Serial tracing and silver nitrate differential staining combine to reveal many of the processes of bone remodeling at work, and facilitate quantitative treatment of the data. Further uses in studies of bone tissue and associated cells are recommended.
Programmed cell death in the Müllerian duct induced by Müllerian inhibiting substance
Authors: Price J. Michael , Donahoe Patricia K. , Ito Yasuo , Hendren W. Hardy 
Published: February 2005

AbstractThe importance of a secretory product of the fetal testis, Müllerian Inhibiting Substance, in determining the fate of the Müllerian duct in the developing male fetus has been well documented. The present investigation has examined the mechanism of action of Müllerian Inhibiting Substance in the male rat fetus during the course of Müllerian duct degeneration.The action of Müllerian Inhibiting Substance mimics the general morphogenetic phenomenon of “programmed cell death,” although important differences were found compared to the majority of other studies of cell death. The initial morphological event in the degenerating Müllerian duct is an increase in lysosomes within the duct cells. Following loss of polarity and orientation, the duct cells are subsequently removed by invading macrophages from the surrounding mesenchyme. Concommitant with the differentiation of these macrophages, the adjacent mesenchyme assumes a characteristic whorled pattern around the degenerating Müllerian duct. Cytochemical localization of acid phosphatase confirmed the presence of newly formed lysosomes within the Müllerian duct cells and subsequently within the cytoplasm of the invading macrophages.
Complicated colobomatous microphthalmos in the BW rat: A new form of inherited retinal degeneration
Authors: Wyse J. P. H. , Hollenberg M. J. 
Published: February 2005

AbstractA new model of inherited retinal degeneration has been found in the rat. It is inherited in association with a number of other ocular defects, including microphthalmos, coloboma, retinal dysplasia, optic nerve hypoplasia and/or aplasia, as well as medullation of the nerve fiber layer of the retina. Together, these abnormalities constitute a condition referred to as complicated colobomatous microphthalmos. This condition was originally discovered in the Bmn strain of rats but subsequently transferred to a new genetic background in the Bmn‐wys strain of rats (BW). This facilitated the histological evaluation of both the developmental and degenerative ocular defects in the adult animals. A well defined pattern emerged relating eye size, optic nerve size and retinal histology. Normal‐sized eyes had normal‐sized optic nerves and normal retinal histology while intermediate‐sized eyes with no optic nerves had uniformly thin retinas. In contrast, intermediate‐sized eyes with small optic nerves had areas of both normal thickness and thin retina. All of these eyes developed retinal degeneration characterized by a late onset and slow progression associated with normal phagocytic activity in the pigment epithelium and a tendency for the rod outer segments to fragment into very thin structures rather than accumulate as lamellar debris. This indicates that the retinal degeneration in the BW model differs in many respects from the well studied RCS model.
Proteolytic activity of guinea pig spermatozoa after induction of the acrosomal reaction in vitro
Authors: Gaddum‐Rosse P. , Blandau R. J. 
Published: February 2005

AbstractAfter inducing the acrosomal reaction in guinea pig spermatozoa in vitro, the sperm were tested for proteolytic activity by applying them to membranes of fixed gelatin. One to 5% of them showed slight evidence of proteolytic activity, while the rest were completely negative. Sperm that had retained their acrosomes throughout the incubation period displayed intense proteolytic activity. These results suggest that proteinases may be lost from spermatozoa as a result of the acrosomal reaction.
Morphological changes induced by cyclophosphamide in crypt epithelium of the small intestine in mice: Light and electron microscopic studies
Authors: Sobhon Prasert , Wanichanon Chaitip , Sretarugsa Prapee 
Published: February 2005

AbstractWhen a single sublethal dose (300 mg/kg body weight) of cyclophosphamide was injected intraperitoneally into experimental mice, several morphological alterations were detected in the crypt epithelium within a few hours. These were (a) mitotic activity of epithelial cells decreased, reaching the lowest level at 16 hours; (b) an abnormally high number of lymphocytes and cells with eosinophilic granules appeared in the epithelium; later these cells degenerated and the maximum number of dead cells was observed at six hours after the drug injection. At four days post‐injection the morphology of crypt epithelium had returned to normal.Electron microscopic examination revealed that although the mitotic activity of crypt epithelial cells was depressed, there was little change in their morphology following the drug administration. However, many intermediate stages of degeneration of lymphocytes and eosinophilic cells were observed in the intercellular spaces as well as apparently inside the cytoplasm of crypt epithelial cells. The eosinophilic cells are characterized by the presence of large crystal‐containing granules in the cytoplasm, and are believed to be equivalent to “globular leucocytes” described by many investigators. Evidence from this study suggests that lymphocytes and globular leucocytes are more sensitive to cyclophosphamide than crypt epithelial cells, and that they degenerate in crypt epithelium.
Mode of locomotion of Schwann cells migrating in vivo
Authors: Billings‐Gagliardi Susan 
Published: February 2005

AbstractThe manner of locomotion of Schwann cells during normal development was studied by means of repeated observations and photomicrographs of individual cells at closely spaced time intervals and focal levels. In developing tadpole peripheral nerves, Schwann cells move sporadically with brief periods of rapid translation of the whole cell interspersed with longer intervals when the cell shows little or no overall movement. Highest rates of locomotion averaged 5 μm/minute with a duration of no greater than four to six minutes. Net rates of speed measured over at least 20 minutes were always considerably lower, with the average being 1.9 μm/minute. Rapid locomotion involves protrusion and growth of several pseudopodia, while the cell body remains in place, followed by attachment of these processes to an axonal surface, and finally detachment of the trailing portions of the cell as the entire cell hitches forward, “inchworm‐style.”