bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphometric and cytochemical analysis of lysosomes in rat Peyer's patch follicle epithelium: Their reduction in volume fraction and acid phosphatase content in M cells compared to adjacent enterocytes
Authors: Owen R. L. , Apple R. T. , Bhalla D. K. 
Published: February 2005

AbstractM cells are specialized epithelial cells over lymphoid follicles in Peyer's patches which take up viruses, bacteria, and antigenic macromolecules from the intestinal lumen. Unlike ordinary enterocytes which sequester pinocytosed material in lysosomes, M cells transport such material across the epithelium to antigen‐processing areas in lymphoid follicle domes, suggesting a difference in lysosomal activity or a different route for movement of endocytic vesicles. Ileal Peyer's patches in rats were examined by electron microscopy to identify lysosomes by acid phosphatase activity. Acid phosphatase was found in dense bodies in enterocytes but not in M cells. Stereological analysis showed the volume fraction occupied by dense bodies in M cells to be 16 times less than in enterocytes (P <.0005), even though the volume fractions of cytoplasm occupied by mitochondria in M cells and enterocytes were not significantly different. The small volume fraction of dense bodies and the absence of acid phosphatase activity in M cells thus correlate with absence of lysosomal degradation of luminal microorganisms during transport into lymphoid follicles by M cells and may provide not only a complete array of microbial antigens for initiation of immune responses, but also a route through the mucosal barrier for microorganisms which can evade local containment mechanisms.
Prolactin causes increased turnover of dopamine in 10‐day‐old rat median eminence
Authors: Silverman William F. , Walsh Raymond J. 
Published: February 2005

AbstractThe present work examines the ability of prolactin to enter the CNS of the rat and effect its feedback stimulation of dopamine release prior to the appearance of prolactin receptors in choroid plexus (i.e., 10 days postnatal). An inhibitor of tyrosine hydroxylase was used to allow the assessment of dopamine turnover separate from synthesis and transport of the amine. Chronic but not acute hyperprolactinemia resulted in increased dopamine release relative to vehicle‐treated controls, as shown by diminished fluorescence intensity in the median eminence. These results indicate that activation of the prolactin short‐loop feedback system occurs by 10 days postnatal, prior to the appearance of prolactin receptors at the choroid plexus.
Regulation of the density of spermatogonia in the seminiferous epithelium of the Chinese hamster: I. Undifferentiated spermatogonia
Authors: De Rooij D. G. , Janssen J. M. 
Published: February 2005

AbstractThe topographical arrangement of the clones of Asingle, Apaired, and Aaligned (As, Apr, and Aal) spermatogonia on the basement membrane of seminiferous tubules of the Chinese hamster was studied. It was found that at least some of these clones are not distributed at random as clones of similar cell number were often seen in clusters. Areas were found with few or many As spermatogonia. Also, clusters of Apr spermatogonia were found, indicating that in such an area many As spermatogonia more or less synchronously formed Apr spermatogonia. Since clusters of clones of 16 Aal spermatogonia were observed, it can be concluded that these clusters of Apr spermatogonia may proliferate in at least a roughly synchronous way.It was found that over large areas the densities of undifferentiated spermatogonia may be very low or high in comparison to the mean density in the animal. Whether the ratio of self‐renewal and differentiation of the stem cells changed locally in response to the high or low density of undifferentiated spermatogonia in particular areas was investigated. No indications for a regulatory mechanism to keep the density of stem cells and/or the density of undifferentiated spermatogonial clones at a certain level could be detected in the normal Chinese hamster. This lack of regulation was at least partly responsible for the widely different numbers of A1 spermatogonia that were formed in the various areas studied in stage IX.
Pathways of lymph flow through superficial inguinal lymph nodes in the pig
Authors: Spalding Hugh , Heath Trevor 
Published: February 2005

AbstractThe pig lymph node has an unusual structure in that tissue containing lymph nodules generally occupies a central position. Our aim was to describe the lymphatic pathways through this node. We studied the structure of these pathways with light and electron microscopy, made casts of lymphatic vessels and sinuses with Microfil, and studied the distribution within the node of subcutaneously injected carbon particles.Most afferent lymphatics penetrate deeply within the node, where they give off several branches to peritrabecular sinuses that ramify through centrally located nodular tissue. However, where an afferent lymphatic enters the node there is a subcapsular sinus over an area of nodular tissue that occupies a conventional superficial position. Some lymph reaches this sinus from the central peritrabecular sinuses, but there can also be direct communications between this sinus and the afferent lymphatic.After flowing through sinuses in nodular tissue, lymph enters tissue that is analogous to medullary tissue in other species. This tissue is of two types, one consisting mainly of a diffuse network of reticular cells around spaces up to 10–12 μm across, and one that more closely resembles conventional medullary tissue. Lymph then flows to collecting ducts, which lack valves, and then to efferent lymphatics.Our findings do not support suggestions that a purely physical obstruction of lymphocytes in the lymph node accounts for the dearth of lymphocytes in efferent lymph of pigs.
Two‐headed, two‐necked conjoined twin calf with partial duplication of thoracoabdominal structures: Role of blastocyst hatching
Authors: McGirr Wendy J. , Partlow Gary D. , Fisher Kenneth R. S. 
Published: February 2005

AbstractGross anatomical analysis of a derodidymic monosomic stillborn male calf from an embryo transfer recipient was carried out. Two normal heads were present on two necks which were fused at the shoulders. Although the ribs were abnormal in shape and number, there was one trunk and four legs. The vertebrae were double and partially fused from the thoracic region to the sacrum, which was singular and normal. In the thoracic region there was a single vertebral canal that contained two incompletely fused spinal cords which shared common meninges. In the lumbar region there was a spina bifida. The medial neck musculature was variously fused. Two esophagi entered one enlarged rumen and the liver and gall‐bladder had extra lobes. Two sets of lungs occupied three pleural cavities and also part of the pericardial cavity. Two hearts were joined by a common cavernous venous sinous. The vasculature cranial to the heart reflected the doubling. The vasculature caudally was singular. The calf was uniscrotal and ipsilaterally cryptorchid. Our results are consistent with the hypothesis that atypical “hatching,” that is, emergence of the blastocyst from the zona pellucida, may cause anomalous twinning.
Postnatal development of the duct system in the mouse parotid gland
Authors: Domon Masaharu , Kurabayashi Tohru 
Published: February 2005

AbstractThe morphology of the parotid gland in adult mice is mouse strain‐specific. C57BL/6 and C3H/He strains of mouse are representatives of two types of the morphology identified previously. The postnatal development of such morphologic differences was investigated by sialography of excised glands of these strains of mouse. It was observed that the mouse strain‐dependent morphological characteristics were already present at birth, except for the branching pattern of the peripheral duct system, which became differentiated at 3 weeks of age. These results indicate that the C3H/He mouse‐specific branching pattern of the peripheral ducts reflects the profile of matured secretory units and ducts, and that the C57BL/6 mouse‐specific pattern resembles that of an immature C3H/He mouse.
Ultrastructure of human fetal mammary gland
Authors: Kellokumpu‐Lehtinen P. , Johansson R.‐M. , Pelliniemi L. J. 
Published: February 2005

AbstractEarly cytodifferentiation of human fetal mammary gland was studied at the time of the beginning of the sexual differentiation during the sixth to eleventh developmental weeks. The gland appeared as a solid epithelial ingrowth into the underlying mesenchyme on both sides of the thoracic wall at the age of 5 weeks in both sexes. These ingrowths contained primitive glycogen‐rich cells with large nuclei. The surrounding mesenchymal cells gathered around the basal lamina. These cells differentiated into fibroblasts, and collagen fibers were seen in the mesenchyme near the mammary buds. No lumina appeared within the buds during this study. Differences between the male and female mammary epithelium or mesenchyme were not observed, although androgen synthesis and secretion in the fetal testis had already begun. The close connections and concomitant differentiation of the mammary bud epithelium and mesenchyme during the early embryogenesis in this study suggest that epithelio‐mesenchymal interaction plays an important role in the differentiation of human mammary gland.
Taste bud development in chickens (Gallus gallus domesticus)
Authors: Ganchrow Judith R. , Ganchrow Donald 
Published: February 2005

AbstractOral epithelium in the anterior mandibular glands region was examined in embryonic, hatchling, and mature chickens to establish the timing of morphologic events during taste bud ontogeny. Hematoxylin‐and‐eosin‐stained sections (10 μm) from 27 Anak (broiler breed) chickens were examined serially, and buds were quantified at 16–20 days of incubation (E) and, posthatch days 1 and 50–60. Taste buds were first recognized at the beginning of E17 as small clusters of cells in the basal epithelium. Only spherical‐shaped buds were observed on E17 and E18, and these spherical clusters never penetrated to the surface of the stratified epithelial layer. E19 marked a transitional stage when mature bud features began to emerge: the buds assumed a more elongate shape, several kinds of cells comprising the bud were distinguishable and the first taste pores were observed. During the ensuing embryonic days, buds continued to elongate commensurate with the deepening oral epithelium and by hatching virtually all buds opened to the oral cavity. No marked morphological changes in taste bud structure were observed on the day of hatching and at 50–60 days posthatching. Taste bud numbers increased dramatically during E17 and E18, peaked on E19, and remained relatively constant there‐after. It is concluded that the morphological sequence of taste bud development in chickens is similar to that in mammals. The timing of bud ontogeny, though initiated only during the third trimester in ovo, essentially is completed by hatching, thus providing the precocial hatchling with the sensory apparatus essential for gustatory experience.
Position of the larynx in odontoceti (toothed whales)
Authors: Reidenberg Joy S. , Laitman Jeffrey T. 
Published: February 2005

AbstractThis study examines the positional relationships of the odontocete (toothed whale) larynx to further an understanding of their breathing, swallowing, and vocalizing abilities. Seventeen specimens representing nine cetacean genera (Delphinus, Stenella, Tursiops, Grampus, Delphinapterus, Globicephala, Kogia, Mesoplodon, and Phocoena) were studied post mortem. Nine specimens were sectioned in the midsagittal plane and the position of the larynx relative to vertebral levels, skull base, and palatal structures was recorded. In eight specimens that could not be bisected for reasons of large size or condition of preservation, the larynx was removed by a ventral approach for further dissection. The results show that the upper respiratory tract of the odontocetes has evolved away from a basic mammalian pattern. Laryngeal position among terrestrial mammals usually corresponds to the level of cervical vertebrae 1–3. The odontocete larynx, however, lies rostral to the level of the atlas and extends to the presphenoidal synchondrosis. Its extension above the level of the foramen magnum is due to three factors: (1) The larynx is elongated into a tubular extension that projects beyond the soft palate into the nasopharynx; (2) the neck region is shortened owing to the highly compressed cervical vertebrae; and (3) the skull base is oriented in the same direction as the cervical vertebrae because of the horizontal and fusiform alignment of the head and thorax. Whereas the larynx of most terrestrial mammals is separable from the nasopharynx, that of the odontocetes studied may be permanently intranarial, held in place by the palatopharyngeal sphincter. Laryngeal position may affect their vocal abilities, allowing odontocetes to simultaneously swallow and echolocate.
Sensory innervation of pulp and dentin in adult dog teeth as demonstrated by autoradiography
Authors: Byers Margaret R. , Närhi Matti V. , Dong Willie K. 
Published: February 2005

AbstractIn order to study the location of sensory nerve fibers in dog teeth, we injected 3H‐amino acids into the left trigeminal ganglion of 2 anesthetized adult dogs; we then waited 24 hours for axonal transport of labeled protein and prepared the fixed decalcified teeth for autoradiography. Heavily labeled sensory neurons were found in the maxillary and mandibular divisions of each injected ganglion and its peripheral nerves and central root. Numerous labeled axons were found entering dental roots; they arborized mostly in the crown to end in peripheral pulp or inner dentin. Some labeled fibers extended 150–175 μm into dentinal tubules, but most intradentinally labeled fibers were less than 100 μm long. The dentinal innervation was most concentrated in the crown, with autoradiographic label over more than 50% of the tubules at the tip of each pulp horn. Differences in innervation density for coronal, cervical, intercuspal, septal, radicular, and reparative dentin were analyzed. In some regions, labeled endings branched along the pulp‐predentin border but did not enter the dentinal tubules.Electron microscopic autoradiograms were prepared to confirm specific labeling of nerve fibers and nerve endings, and to describe their ultrastructure and association with odontoblasts. The results show that labeled sensory fibers in dog teeth have an ultrastructure similar to that described previously for rat molars and for monkey and cat teeth. No specific junctions were found between labeled sensory fibers and odontoblasts, in agreement with previous studies of other teeth.
Nonclathrin‐coated vesicles are involved in endocytosis in kidney collecting duct intercalated cells
Authors: Brown Dennis , Weyer Patrick , Orci Lelio 
Published: February 2005

AbstractIntercalated cells of the kidney collecting duct are able to modify the structure of their apical plasma membrane in response to different physiological conditions. It has been proposed that this process involves the transfer of membrane components (including a proton‐pumping ATPase) to and from the apical membrane by a specialized population of tubulovesicles that are found in the apical cytoplasm of these cells. These vesicles have a prominent cytoplasmic coat of regularly arranged dense studs that we have recently shown to be immunocytochemically and morphologically distinct from clathrin. In this study, we have examined the function of these vesicles by using horseradish peroxidase as a tracer of endocytosis at the light and electron microscopic levels. Following the intravenous injection of rats with the tracer, we found a massive labeling of the tubulovesicle compartment of intercalated cells, providing direct evidence that these nonclathrin‐coated vesicles are involved in endocytotic events in this cell type. This novel membrane coating material could contain the cytoplasmic domains of molecules transported to and from the plasma membrane by these vesicles (e.g., an H+ ATPase) or it could be a molecule that is involved in vesicle function, by analogy with clathrin.
Structure and neural control of the pectoralis in pigeons: Implications for flight mechanics
Authors: Dial Kenneth P. , Kaplan Sandra R. , Goslow G. E. , Jenkins Farish A. 
Published: February 2005

AbstractThe pectoralis muscle in pigeons (Columba livia) is composed of two heads (sternobrachialis, thoracobrachialis) that are separately innervated and have different fiber orientations. High‐speed film and electromyographic studies of free‐flying pigeons reveal that the pectoralis is activated prior to wing depression (the power stroke) and that its two heads are differentially recruited during takeoff, level flight, and landing. The elecrical activity patterns of both heads support an interpretation that intramuscular elasticity provides energy storage. The pectoralis is not only the prime wing depressor but is also capable of adjusting the excursion of the wing during different phases of flight.
Morphogenesis of the truncus arteriosus of the chick embryo heart: Movements of autoradiographic tattoos during septation
Authors: Thompson Robert P. , Abercrombie Vant , Wong Matthew 
Published: February 2005

AbstractIn order to trace tissue movements during septation of the embryonic truncus arteriosus into aortic and pulmonary cardiac outlets, the cephalic margin of the developing tubular heart of chick embryos was tattooed at Hamilton‐Hamburger Stages 20–22 using diffusion micropipettes filled with 0.5% agarose and radioactive macromolecular precursors (tritiated thymidine, uridine, and leucine). Following further incubation for 2, 48, or 96 hours, the locations of such tatoos were determined by autoradiography of sectioned tissue and computer reconstruction of the developing outflow tract.Two hours after tattooing, radiolabeled cells were clustered at the right distal margin of the myocardial tube, as intended. Two days later, during septation of the outflow tract into the two arterial streams, label was concentrated along the posterior margin of the myocardium, between the developing aortic and pulmonary valve anlagen to the embryo's right and left, respectively. Four days following tattooing, as truncal septation neared completion, remaining label was found primarily to the left of the aortic valve ring posterior to the pulmonary outlet. The movements of thymidine tattoos during septation were demonstrated in a series of 31 embryos, 14 fixed at 2 hours, 12 at 2 days, and 5 at 4 days following tattooing; similar results were seen in uridine and leucine labeled hearts.The motion of such tattoos in the developing chick heart suggests that the left side of the definitive semilunar valve ring derives from the right distal margin of the primitive tubular heart and that normal morphogenesis of the great arterial streams involves both retraction and rotation of the embryonic truncus arteriosus.
Bone “mass” and the “mechanostat”: A proposal
Authors: Frost H. M. 
Published: February 2005

AbstractThe observed fit of bone mass to a healthy animal's typical mechanical usage indicates some mechanism or mechanisms monitor that usage and control the three longitudinal growth, bone modeling, and BMU‐based remodeling activities that directly determine bone mass. That mechanism could be named a mechanostat. Accumulated evidence suggests it includes the bone itself, plus mechanisms that transform its mechanical usage into appropriate signals, plus other mechanisms that detect those signals and then direct the above three biologic activities. In vivo studies have shown that bone strains in or above the 1500–3000 microstrain range cause bone modelling to increase cortical bone mass, while strains below the 100–300 microstrain range release BMU‐based remodeling which then removes existing cortical‐endosteal and trabecular bone. That arrangement provides a dual system in which bone modeling would adapt bone mass to gross overloading, while BMU‐based remodeling would adapt bone mass to gross underloading, and the above strain ranges would be the approximate “setpoints” of those responses.The anatomical distribution of those mechanical usage effects are well known. If circulating agents or disease changed the effective setpoints of those responses their bone mass effects should copy the anatomical distribution of the mechanical usage effects. That seems to be the case for many agents and diseases, and several examples are discussed, including postmenopausal osteoporosis, fluoride effects, bone loss in orbit, and osteogenesis imperfecta.The mechanostat proposal is a seminal idea which fits diverse evidence but it requires critique and experimental study.
Decrease of proteoglycan granule number but increase of their size in articular cartilage of young rabbits after physical exercise and immobilization by splinting
Authors: Paukkonen Kari , Helminen Heikki J. 
Published: February 2005

AbstractThe effects of physical exercise (running) and immobilization by splinting on the number and size of proteoglycan (PG) granules and the diameter of collagen fibers of the articular cartilage were studied with the transmission electron microscope with a stereological method. The lateral tibial condyles of 24 young rabbits were examined. The analysis was carried out in the superficial, middle, and deep zones of uncalcified articular cartilage and also in the pericellular, territorial, and interterritorial regions of each zone. PGs were demonstrated in situ by using en bloc staining with the cationic dye ruthenium red, which binds to negative groups of glycosaminoglycans. Results of the control group showed that there was a large pericellular number of PG granules, and the number of granules tended to increase through cartilage depth. The mean diameter of PG granules was highest in the superficial zone and decreased through cartilago depth. The collagen fibers were thicker in the interterritorial than in the territorial region and their diameters increased from superficial toward the deep zone of uncalcified cartilage. Results of the experimental groups showed that the number of ruthenium‐red‐positive PG granules decreased by 3–46% in all zones and regions after both physical exercise and joint immobilization. On the other hand, the diameter of PG granules increased by 4–42% in all zones and regions in all groups. Collagen fibers in the territorial region of the middle zone were thinner in the exercised and in the splinted knee, while thicker in the contralateral knee to the splinted limb, as compared with the controls. Depending on its degree, mechanical stress or loading of the joint is suggested to have either anabolic or catabolic effects on articular cartilage.