bluuebunny/crossref_metadata_2025_split huggingface dataset:
Local action of intrahypophyseal implants of estrogen as revealed by staining with peroxidase‐labeled antibody
Authors: Gersten Brian E. , Baker Burton L. 
Published: February 2005

AbstractThe direct action of 17 β‐estradiol and cholesterol on cells of the pituitary pars distalis, as revealed by staining with peroxidase‐labeled antibody, was studied in female rats. Pellets of pure cholesterol and of estradiol mixed with cholesterol were implanted into the left lobe of the pars distalis 14–32 days after ovariectomy and left in place for 7–16 days. Rabbit antisera to rat prolactin, human growth hormone, human chorionic gonadotropin (for gonadotropes — presumably luteinizing hormone cells), and porcine corticotropin were used. In no case were cells altered in the contralateral lobe of the pars distalis; cholesterol likewise had no significant effect on the ipsilateral lobe. However, in the ipsilateral lobe containing an estrogen pellet, prolactin cells were hypertrophied and hyperplastic; cells assumed to be responsible for luteinizing hormone secretion were reduced in size and stained more intensely; and growth hormone cells were reduced in size. Corticotropin cells remained unaffected. For the most part estrogenic effects were distributed ventrally, caudally and laterally from the pellet and not far medially, never reaching the midline. It was concluded that estrogen acts directly on the hypophysis, the spread of the effects reflecting the direction of blood flow within the gland. These observations support the hypothesis that the pituitary gland serves as a site for feedback action by estrogen.
Ultrastructural study of thoracic duct lymphocytes of mice
Authors: Wivel Nelson A. , Mandel Mark A. , Asofsky Richard M. 
Published: February 2005

AbstractThe fine structure of cells in mouse thoracic duct lymph was described, and the changes in cell population during a prolonged drainage of five days were characterized. From 93.9–97.0% of the cells were lymphocytes and 99.9% of them had the greatest axis ranging from 5.0–6.3 μ. Those cells which ranged in greatest dimension from 6.3–9.0 μ constituted 3–6% of the total population and were lymphocytes, developing and mature plasma cells, monocytes, polymorphonuclear leukocytes, and unclassified cells. The developing and mature plasma cells increased from 1.4–5.5% when day 1 of cannulation was compared with day 2. These cells constituted 3.5% of the population of day 3 and 3.9% on days 4 and 5. The numbers of these cells appeared to account for most of the increase in large lymphocytes seen by light microscopy. Approximately 5% of the lymphocytes contained inclusions which had the appearance of lipid. The findings were compared with previous observations in other mammalian systems.
Studies on the tadpole tail I. Structure and organization of the notochord and its covering layers in Rana catesbeiana
Authors: Bruns Romaine R. , Gross Jerome 
Published: February 2005

AbstractThis paper presents a detailed description of the notochord and its covering layers in the tail of the premetamorphic bullfrog (Rana catesbeiana) tadpole.In general, the notochord is a tapered, rod‐like structure composed of large vacuolated cells. It is covered by a thin basement membrane and by several thicker layers of connective tissue whose organization around the notochord differs along the length of the tail. In the proximal half of the tail the notochord and its basement membrane are followed consecutively by the notochord sheath, the elastica externa and the outer connective tissue sheath. In the distal part, however, the basement membrane is followed by the elastica interna, the notochord sheath and the outer connective tissue sheath. Toward the tip of the tail the connective tissue layers gradually become thinner and finally disappear leaving the tip of the notochord with its basement membrane lying in loose mesenchymal tissue.
Role of spermatogonia in the repair of the seminiferous epithelium following X‐irradiation of the rat testis
Authors: Dym Martin , Clermont Yves 
Published: February 2005

AbstractIn the normal adult rat testis, type A0 spermatogonia do not appear to participate to a significant extent in the production of spermatocytes, while type A1 spermatogonia periodically initiate a series of divisions resulting in the production of spermatocytes and new type A1 spermatogonia.The behavior of type A0 and A1 spermatogonia was investigated following administration of a single dose of x‐rays (300 r) to the testis. Using whole mounts of seminiferous tubules, the type A0 and A1 cells were counted at various intervals after irradiation. At 8 and 13 days after irradiation, type A1 spermatogonia reached lowest values, i.e., 6% and 3% of non‐irradiated control, while type A0 reached the lowest value, i.e., 62% of control at eight days. Thereafter the numbers of type A0 and A1 progressively increased to return to normal at 39 days. It was thus concluded that the type A0 were comparatively more resistant to x‐irradiation than type A1 spermatogonia.To verify if the surviving type A0 proliferated in the irradiated testis, animals were injected with 3H‐thymidine three hours before they were sacrificed at various times after x‐irradiation. In irradiated testes the labeling indices of the surviving type A (A0, A1–A4) were the same as in the non‐irradiated testes except in stages V‐VI of the cycle of the seminiferous epithelium. While in the controls only 2% of type A cells were labeled at these two stages of the cycle, after irradiation the labeling index of type A reached a maximum of 31% at 13 days to return to control values by 39 days. Since at 13 days after irradiation type A0 spermatogonia were the predominant component of the spermatogonial population, it was concluded that these cells must have incorporated 3H‐thymidine and thereby contributed to the reconstruction of the spermatogonial population partially destroyed by irradiation.
Electron microscope studies of sperm incorporation into the golden hamster egg
Authors: Yanagimachi R. , Noda Y. D. 
Published: February 2005

AbstractHamster eggs freed from the cumulus oophorus and zona pellucida were inseminated in vitro with capacitated spermatozoa. As soon as the spermatozoon reaches the surface of the egg cytoplasm, numerous microvilli of the egg surround the spermatozoon. Those microvilli attached to the acrosomal collar region of the spermatozoon quickly spread over the inner acrosomal membrane of this region, dislodging the outer acrosomal membrane and the overlying sperm plasma membrane. At the same time, microvilli fuse with the plasma membrane of the postnuclear cap region of the spermatozoon, and the egg cytoplasm quickly flows around the nucleus of that region of the spermatozoon. The inner acrosomal membrane persisting on the sperm head never fuses with the egg (microvillar) plasma membrane. This membrane is destined to disintegrate and be absorbed into the egg cytoplasm. Incorporation of the sperm flagellum into the egg cytoplasm takes place by fusion between plasma membranes of the spermatozoon and egg.
Nerve contributions to the pelvic plexus and the umbilical cord
Authors: Pearson Anthony A. , Sauter Ronald W. 
Published: February 2005

AbstractSerial sections of human embryos and fetuses reveal that the sacral nerves which contribute fibers to the pelvic plexus often have dorsal, ventral, and oblique communicating rami. The ventral rami resemble the white rami of upper thoracic nerves and some of their fibers pass close by or through the chain ganglia and into the pelvic plexus. The sizes of the ventral rami are often in inverse proportion to that of the pelvic splanchnic nerves. That is, when the pelvic splanchnic nerves are poorly developed, the ventral rami are large, and conversely, when the pelvic splanchnic nevers are well developed, these rami are small. The pelvic plexus was found to receive fibers from the sympathetic trunk and its ganglia in addition to those from the hypogastric plexus and the pelvic splanchnic nerves.Analysis of the observations made in this study together with a review of the literature in light of the present day classification of nerve fibers raises serious doubts concerning the limits set for the outflow of preganglionic nerve fibers from the spinal cord and the distribution of gray and white rami as described in recent textbooks in terms of their histological and physiological significance.Nerve fibers from the pelvic plexus can be traced along the walls of the bladder and the urachus and along the umbilical arteries into the umbilical cord. In embryos, only a few scattered nerve fibers were found distal to the umbilicus, but in fetuses at term, distinct nerve bundles were identified in the cord. These bundles sent branches to the walls of the umbilical arteries; other branches terminated as “end‐nets” in Wharton's jelly. These nets appeared as fine fibers with nodular swellings at irregular intervals. Innervation of the umbilical arteries was richest within the first few inches of the cord. Beyond this region, the nerves rapidly decreased in number. “End‐nets” were present as far as four inches from the umbilicus. Granular cells resembling Langerhans' cells were found in the cord. Often these cells were closely associated with fine nerve fibers.
Locomotor adaptations in the disc‐winged bat Thyroptera tricolor. I. Functional organization of the adhesive discs
Authors: Wimsatt William A. , Villa‐R Bernardo 
Published: February 2005

AbstractLocomotor capability on smooth vertical surfaces is rare in mammals. The adhesive discs on thumbs and soles of bats of the family Thyropteridae are uniquely specialized for this purpose, but their functional organization remains virtually unexplored. The face of the discs is concave, has a characteristic dermatoglyphic pattern, and is permanently moist. Each disc is supported by a biconcaval fibrocartilagenous framework; its circular “rim” is divided into 60–80 chambers, each accommodating a sudoriparous gland which discharges on the disc face. Glandular form and cytology are unique, reflecting special functional adaptations. Other significant adaptations involve the epidermis, distribution of adipose tissue, extrinsic muscle insertions, disc relations to digital joints, and distribution of certain sensory endings. The discs have no intrinsic musculature and are manipulated from without. Experiments with living Thyroptera and analysis of the internal organization of the discs verify that their functional mode is suctorial rather than some other adhesive mechanisms; special relationships within the thumb discs suggest that the adhesive force may be to some extent adjustable under normal use.
Fine structural modifications of the rat chromatoid body during spermiogenesis
Authors: Susi F. R. , Clermont Y. 
Published: February 2005

AbstractThe chromatoid body of rat spermatocytes and spermatids was studied with routine electron microscopy and the PA‐silver method for detection of glycoproteins. The chromatoid body consists of a membrane‐free aggregate of electron dense, finely filamentous material, in association with small vesicles. In late pachytene spermatocytes, there may be more than one chromatoid body; its dense component is diffusely reticulated. In young spermatids, there is only one chromatoid body per cell; the dense component is fairly compact, but it encloses less dense areas continuous with the cytoplasm. Within the less dense areas, as well as at the periphery of the dense component, small (400–800 Å) oval or tubular vesicular structures are observed whose contents exhibit a positive reaction for glycoprotein in PA‐silver stained sections. When the spermatid nucleus begins to elongate, the chromatoid body takes the form of an arc around the axial filament proximal to the centriolar apparatus. Soon thereafter, the bulk of the chromatoid body condenses into a sphere of very dense filamentous material surrounded by a corona of enlarged glycoprotein‐containing vesicles. In the later stages of spermiogenesis, the chromatoid body migrates away from the nucleus and disintegrates by fragmentation. It is noted that the chromatoid body undergoes its major morphological changes, possibly indicative of its active phase, while located in the para‐centriolar region, at the time when the nucleus elongates, and the connecting piece and ring of the spermatid are formed.
Histology of the corpus luteum in the ewe: Changes during the estrous cycle and early pregnancy, and in response to some experimental treatments
Authors: Thwaites C. J. , Edey T. N. 
Published: February 2005

AbstractA technique, developed for the objective histological evaluation of the corpus luteum of the sheep, was applied to normal cyclic and pregnant ewes as well as to ewes subjected to various experimental treatments. Gross histological regression of the corpus luteum progressed rapidly between days 15 and 17 of the estrous cycle. Similar regressive changes did not occur in pregnant ewes; up to day 40, the oldest stage studied, corpora lutea of early pregnancy were similar in appearance to those of mid‐cycle.Stresses such as high environmental temperature and acute undernutrition, which may lead to embryo mortality, had no significant effect on corpus luteum histology. Exogenous progesterone slightly depressed the size and weight of the corpus luteum but was without significant effect on its histology. Exogenous cortisol, and more particularly corticotropin, were sometimes associated with marked histological regression of the corpus luteum, although in ewes treated with these hormones there was no significant reduction in embryo survival at the time of autopsy.The observations do not support the suggestion that corpus luteum failure is a frequent cause of embryonic death in the ewe. The technique presented is considered sufficiently sensitive to detect quite small changes in the histological appearance of the corpus luteum, although the relationship of these changes to progesterone secretion is not known. However, the dramatic regression observed between days 15 and 17 of the estrous cycle fits the known pattern of progesterone secretion at this time.
The opisthonephric kidney of the sea lamprey of the great lakes, Petromyzon marinus L. III. Intermediate, distal, and collecting segments of the ammocoete
Authors: Youson John H. , McMillan Donald B. 
Published: February 2005

AbstractThe presence of microvilli and well‐developed organelles in the cells of the non‐ciliated intermediate segment of the ammocoete nephron suggests that this is not simply a conducting tubule but may be involved in the formation of urine. This region more closely resembles the thin limb of the loop of Henle of mammals than the intermediate segment of lower vertebrates.The distal segment consists of dark and light cells possessing varying amounts of glycogen, mitochondria, and smooth endoplasmic reticulum. Basal infoldings of the plasma membrane are lacking in the distal cells but wide intercellular spaces are present. Angular prismatic mitochondrial cristae are found within the glycogen‐rich cells of the intermediate and distal segments.The collecting segment also possesses narrow intercellular spaces as well as an abundance of organelles, particularly smooth endoplasmic reticulum and mitochondria, suggesting that this region may also be involved in urine formation.
Morphological changes in mouse eggs due to aging in the fallopian tube
Authors: Szollosi Daniel 
Published: February 2005

AbstractMorphological changes in mouse eggs due to aging become evident after the eggs have spent approximately 12 hours in the oviduct. The spindle rotates at first and is radially disposed. Later the entire spindle migrates to the center of the egg. In most eggs the spindle is maintained throughout the first 24 hours after ovulation. In some eggs a nucleus is reconstituted without formation of polar body II. Other eggs break into several cytoplasmic fragments but a nucleus is seen only in the largest fragment. The cortical granules lose their proximity to the cell membrane, migrate centrad and frequently swell. The cumulus cells and the cells of the corona radiata degenerate and/or disperse.
The relationship of the developing inner ear, subarcuate fossa and paraflocculus in the rat
Authors: McClure Theodore D. , Daron Garman H. 
Published: February 2005

AbstractA study of the development of the subarcuate fossa and its relationships to the semicircular canals and to the paraflocculus was made in the rat. Specimens ranging from 12‐day embryos through 31 days after birth and adults were used for dissection and microscopic studies.Two distinct steps are identified in the development of the fossa. First preceded by the differentiation of the semicircular canals, a primitive subarcuate fossa, which is completely filled with loose vascularized connective tissue, develops in the periotic capsule. Second, the primitive dura mater of the posterior cranial fossa evaginates into the area of the primitive fossa displacing the loose connective tissue contained therein, to form a laterally projecting cavity from the posterior cranial fossa, the definitive subarcuate fossa. Thus, the primitive subarcuate fossa appears passively as a product of the pattern of development of the periotic capsule.The paraflocculus of the cerebellum does not appear to influence the development of the definitive subarcuate fossa since it secondarily occupies the area of the fossa. The pedunculated nature of the paraflocculus is associated with, and probably results from, the diameter of the ostium of the fossa being smaller than its greatest width.A comparison is made of the development of the subarcuate fossa within the periotic capsule in the rat and man. In the adult rat a definitive subarcuate fossa is present, while in adult man only a rudimentary counterpart exists.
Vasculogenesis in the chick embryo. An ultrastructural study
Authors: Gonzalez‐Crussi Frank 
Published: February 2005

AbstractThe morphogenesis of the extra‐embryonic circulatory system of the chick was studied by light and electron microscopy, from precirculatory stages until the beginning of the definitive circulation. Early mesodermal migrations of prospective vasoformative cells and formation of blood islands take place with minimal morphologically expressed cytodifferentiation. The earliest mesodermal clusters are not syncytial. Formation of vascular lumina is not due to lysis of central cells. Undifferentiated mesenchyme possesses the capacity to establish complex junctional devices at points of contact with like cells. The first formed blood islands show intimate relationships with endoderm. The initial capillary network is sinusoidal in type, the endothelium being unsupported by a basement membrane. The major vitelline vessels acquire a more complex anatomy but the capillaries retain this simple pattern throughout the period studied. Several phases in the histogenesis of vitelline vessels are recognized, which could be correlated with the known progression of arterial pressure patterns. Continuing differentiation and mesenchymal investment of vascular walls, after stages 22–23 of Hamburger and Hamilton ('51), in correspondence with the last sustained pressure elevation, leads to completion of the adult vascular structure.
The fine structure of the peripheral nerve root sheath in the subarachnoid space in the rat and other laboratory animals
Authors: Haller Frederick R. , Low Frank N. 
Published: February 2005

AbstractSpinal nerve roots from several laboratory animals (rat, mouse, dog, chinchilla) were fixed by perfusion with buffered aldehydes and prepared for electron microscopy. The fine structure of the root sheath possesses a common histologic organization wherever found. Its cellular and fibrous coverings are arranged in several lamellae which can be divided into two basic layers. The cytology of the outer layers resembles the characteristics of cells which line the subarachnoid space elsewhere (pia, arachnoid, arachnoid trabeculae, blood vessel adventitia). These cells adjacent to the subarachnoid space are arranged loosely and are in close association with extracellular connective tissues. The junctions between them appear to be intermittent, which would allow communication between the subarachnoid space and the intercellular spaces. The inner layers (adjacent to the endoneurium) are regularly arranged and are close to each other. Facing the endoneurium a boundary (basement) membrane is almost invariably associated with the basal cell layer. The inner cell layers are more nearly comparable to perineurium but, because of structural variations, are not readily classified. However, in its totality, the root sheath does not correspond histologically to pia, arachnoid or perineurium as they are found in their usual locations.
Tooth transplantation in the mouse. I. The use of procion dyes and tritiated proline in a study of syngeneic tooth germ transplantation
Authors: Klein Jan , Secosky Walter R. , Klein Dagmar 
Published: February 2005

AbstractTooth germs of first molars from four‐ to six‐day old mice were transplanted heterotopically into the connective tissue under the dorsal skin of adult syngeneic recipients. The rate of the transplants was studied by histologic staining, vital staining with procion dyes, and autoradiography. Together these methods provided the following picture of the development of the transplant. Extraction of the tooth germ severs its vascular connections and disturbs the nutritional environment of the tooth so that many cells undergo necrosis and degeneration. The resulting inflammatory response clears the transplant of necrotic tissue, leaving a fibrous pulp of low cellularity and an extensively disrupted odontoblastic layer; the enamel organ is reduced to only a few epithelial cells. In the second week following transplantation, however, the surviving cells start to proliferate and the tissues of the transplant begin to reorganize. Reorganization starts at the apical foramen and spreads to the rest of the tooth. The central pulp is penetrated by new blood vessels, its cellular content is reestablished, and its morphology returns to normal. Odontoblasts start producing dentin which at first is highly irregular and contains many cells (osteodentin). Later the dentin formation becomes more and more regular and the dentin assumes its normal tubular structure. New enamel is not formed at any time after transplantation. The cells of the enamel organ undergo squamous metaplasia and form epithelial cysts. Abortive root formation is observed but typical roots never develop. Rudiments of periodontal ligament develop rarely. The transplants are enclosed in a capsule of connective tissue.It is concluded that the heterotopically transplanted tooth germs maintain their capability to recover, develop, and differentiate in syngeneic recipients. Although almost all of the developmental processes continue in the transplant after a period of adjustment, some of them are abortive.