bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of development on the number of calcitonin‐containing cells in the mouse thyroid
Authors: Wechbanjong Nualnoi , McMillan Paul J. , Dalgleish Arthur E. 
Published: February 2005

AbstractCalcitonin‐containing cells in serial, 6‐μm sections of the thyroid glands of Swiss Webster mice, at 1 day, 2 weeks, 4 weeks and 8 weeks of age, were demonstrated by an immunoperoxidase method, using antiserum to human calcitonin. C‐cell nuclei were counted in every sixth section of both left and right lobes. The average number of C‐cells counted in the thyroid glands of 8‐week‐old animals was 18‐fold, 5.5‐fold and 2.5‐fold greater than the number observed in 1‐day, 2‐week and 4‐week‐old animals, respectively. C‐cell concentration was found to be greatest in 4‐week‐old mice. Mitoses of C‐cells were observed in animals which were 1 day, 2 weeks and four weeks old. No mitotic figures were seen in 8‐week‐old animals. A few C‐cells were seen in close association with neurons. The volume of the thyroid glands of 8‐week‐old animals was about 14‐, 4‐ and 3‐fold greater than the volume in the 1‐day‐old, 2‐week‐old and 4‐week‐old mice, respectively.These changes in the C‐cell population during development provide a model for the study of C‐cell proliferation and storage of calcitonin.
Changes in the fine structure of tanycytes during the annual reproductive cycle of the male little brown bat Myotis lucifugus lucifugus
Authors: Brawer James R. , Gustafson Alvar W. 
Published: February 2005

AbstractThe hypothalamic arcuate nucleus in the male little brown bat Myotis lucifugus lucifugus was studied with the electron microscope. Animals were killed by intracardial perfusion at each season throughout the year so that the arcuate nucleus could be examined for seasonal variations in morphology. Striking seasonal changes in the fine structure of ependymal tanycytes lining the arcuate nucleus were observed. Tanycytes in animals collected in the fall and early winter exhibited pale processes characterized by a scant internal framework of microtubules and fine filaments. These processes, which were found throughout the arcuate nucleus, exhibited simple irregular shapes. In animals collected between January and June, tanycyte processes contained dense accumulations of fine filaments intermingled with microtubules, and projected long attenuated extensions that often formed multilamellar sheets around axodendritic terminals or other neuronal elements. Tanycyte processes of animals collected in July and August were densely packed with microtubules and fine filaments. The processes radiated elaborate multilamellar extensions that encapsulated axons, dendrites and even entire neuronal perikarya. Multilamellar sheets consisted of as many as 10 or 12 closely spaced gyres. The seasonal variations in tanycyte structure are suggestive of astrocyte‐like behaviour. These changes are discussed with respect to seasonal changes in hypothalamic neuroendocrine activity.
Fine structural studies of rat seminal vesicle in castrated and intact animals following estrogen treatment
Authors: Thompson Sue Ann , Rowley David R. , Heidger Jr. Paul M. 
Published: February 2005

AbstractThe effect of estradiol and/or testosterone upon secretion by seminal vesicle in castrated and intact rats was assessed in young adult Sprague‐Dawley rats, using light microscopy (LM), transmission (TEM) and scanning (SEM) electron microscopy. Hormones were injected daily for ten days beginning ten days after castrations were performed. The normal rat seminal vesicle, as revealed by SEM, was characterized by a large saccular lumen with highly folded walls. Cell surfaces were covered with microvilli, or occasionally displayed a protruding, ruffled surface, sparsely covered with short microvilli. Cytology was normal in testosterone‐treated animals. Estradiol treatment of castrated animals stimulated secretion by seminal vesicle epithelial cells as evidenced by the presence of normal secretory bodies, the presence of RER, and moderately hypertrophied Golgi complexes. These glands were not heavier than were glands from castrated, untreated animals, although the epithelial cells were significantly taller. Secretion was maintained in intact animals treated with estradiol, although glands were smaller and epithelial height was reduced. Estradiol and testosterone treatment in combination did not appear to have an additive effect on secretion, weight of the gland, or epithelial height. The following results support the hypothesis that estrogen‐induced prolactin synthesis and release may be involved in the mechanism by which estradiol effected stimulation of seminal vesicle epithelium. Prolactin‐treated, castrated animals exhibited focal areas of stimulated epithelium. In hypophysectomized animals (untreated controls), the seminal vesicle epithelium retained some secretory bodies and secretory fluid in the glandular lumen; epithelial height was taller than that in castrated controls. Estrogen treatment reduced the epithelial height to that of castrated controls; there was no evidence of secretion. This suggests that in the absence of anterior pituitary hormones, including prolactin, the stimulatory effect of estradiol on seminal vesicle epithelium was nullified. In adrenalectomized/castrated animals, estradiol treatment stimulated secretion in seminal vesicle epithelium just as in non‐adrenalectomized/castrated animals. This indicates that the adrenal gland plays a non‐essential role in the action of estrogen on seminal vesicle epithelium.
Immunocytochemical evidence for anti‐LHRH and anti‐ACTH activity in the “F” antiserum
Authors: Clayton Claudia J. , Hoffman Gloria E. 
Published: February 2005

AbstractAn antiserum which has previously been thought to be specific for LHRH‐ like immunoreactive material was shown to contain two populations of antibodies, one demonstrating anti‐LHRH activity and the other anti ‐ACTH (1‐24) activity. In rat and mouse, ACTH(1‐4)‐like immunoreactive substance is present in perikarya within the basal hypothalamus and in fibers in arcuate, periventricular and dorsomedial nuclei. LHRH‐like immunoreactivity is present in fibers within the median eminence and arcuate nucleus, in a few fibers running along the ventral border of the hypothalamus, and in a small number of cell bodies within the medial basal hypothalamus.
Development of the renal corpuscle during metamorphosis in the lamprey
Authors: Youson John H. , Ooi Eng C. 
Published: February 2005

AbstractThe renal corpuscle of the adult lamprey, Petromyzon marnus L., is formed during the programmed period of metamorphosis. Development is initiated early in this metamorphic period and is marked by the synchronous formation and growth of rudimentary nephron units (RNU) from a longitudinal cord of nephrogenic tissue extending from the posterior tip of the degenerating larval kidney to the cloaca and connected to the peritoneal epithelium. Detachment of the RNU from the peritoneum involves autolysis and cell death and is accompanied by their branching into five or six hexagonally‐arranged nephrons which radiate from the original point of attachment.Differentiation of the epithelial cells at the proximal ends of the nephrons is preceded by the widening of lateral intercellular spaces, the formation of tubular lumina (primitive urinary spaces), the loss of apical cell junctions, and the development of a capillary network with its associated mesangium. With the extension of the capillaries and mesangium between the proximal ends of adjacent undifferentiated nephrons, visceral epithelial cells (podocytes), with long cell processes (trabeculae) and slit membranes, make their appearance.The urinary spaces resulting from this form of development are lined by the epithelium of the dilated ends of the nephrons (nephric capsules). The cells of these capsules differentiate mainly into podocytes, but a few parietal cells connect to the draining tubule. This method of development explains the unique form of the renal corpuscle in the adult lamprey. Despite the type of morphogenesis, this renal corpuscle possesses the fine‐structural features seen in the renal corpuscles of other vertebrates.
Successful maintenance of suckling rat ileum in organ culture
Authors: Shields Helen M. , Yedlin Steven T. , Bair Frank A. , Goodwin Carol L. , Alpers David H. 
Published: February 2005

AbstractIleum from rats 4, 9, 11, 12, and 15 days old can best be maintained for 24 hours in a system using Hanks' Balanced Salt Solution without fetal calf serum, at 25°C and 21% O2. Suckling rat duodenum and jejunum were difficult to maintain well for 24 hours in this system or a variety of other systems that were tried. A temperature of 37°C hastened deterioration of duodenum, jejunum or ileum. With ileum, 3H‐thymidine and 14C‐leucine were increasingly incorporated into DNA and protein over the 24‐hour period. Light microscopy, as well as scanning and transmission electron microscopy, showed very good preservation of the ileum after 24 hours. The addition to the medium of hydrocortisone, 1 μm, and thyroxine, 0.01 μm, alone or in combination, did not change DNA or protein synthesis, or morphology, possibly because of the relatively short (24 hour) time period. Our organ culture system emphasizes the differences between suckling rat ileum and the rest of the intestine, and provides a new tool for evaluating, over a 24‐hour period, the developing rat small intestine.
Observations on closure of the neuropores in the chick embryo
Authors: Schoenwolf Gary C. 
Published: February 2005

AbstractNeuropore closure was studied in chick embryos by light and electron microscopy. Surface ectoderm reflects over the crests of the neural folds at all craniocaudal levels, merging with the neural ectoderm lining the neural groove. Apices of surface ectodermal cells have an essentially identical morphology prior to approximation of folds, both within the presumptive fusion sites and more laterally. Cells of these areas have slightly convex profiles exhibiting few cellular protrusions. Each neural fold contains a superficial half, composed of neural ectoderm covered by surface ectoderm, and a deep half consisting entirely of neural ectoderm. Initial contact between folds usually occurs near the junction between these halves in cranial regions, but is restricted primarily to surface ectoderm at caudal levels. Subsequent fusion of folds at all levels involves both ectodermal layers. Cellular protrusions and small, morphologically unspecialized intercellular junctions often interconnect cells of apposed folds in areas undergoing fusion. The anterior neuropore closes at stages 10–11, but fusion of folds in this region is not completed until stages 13–14. Fusion occurs dorsoventrally in this area and is more advanced internally than externally. Numerous pleomorphic inclusions and a few apparently necrotic cells are present in areas bordering the anterior neuropore. The posterior neuropore closes at stages 12–13 and fusion is completed in this region during stages 13–14. The caudal end of the posterior neuropore closes dorsal to the developing tail bud. Several morphological features of this closure may at least partially account for the high susceptibility to myeloschisis localized specifically at caudal spinal cord levels.
The effect of estrogen on epithelial cell proliferation and differentiation in the crypts of the descending colon of the mouse: A radioautographic study
Authors: Hoff Martin B. , Chang William W. L. 
Published: February 2005

AbstractThe regulatory role of estrogen on cell population kinetics in the descending colon was studied in intact female and ovariectomized mice. In the colonic crypts from intact mice, the crypt size (the number of epithelial cells per crypt column) and the proliferative activity of epithelial cells fluctuated slightly during the estrous cycle. Peak cellularity per crypt column was exhibited during estrus and early diestrus, whereas peaks in labeling index were seen during estrus and late metestrus. While the population size of mucous cells showed a minimal variation, the number of proliferative vacuolated cells per crypt column varied inversely with that of differentiated columnar cells during estrous cycle. The vacuolated cells were increased in number in the preovulatory phase and the columnar cells in the postovulatory phase.Three weeks after bilateral ovariectomy, the colonic crypt appeared to reach a new steady state, which was characterized by a small crypt size, a decrease in the number of differentiated cells, an increase in the relative number of proliferative cells and a relative increase in the proliferative activity of the crypt as compared to intact mice.When ovariectomized mice were treated with estrogen, the number of 3H‐thymidine‐labeled cells in the crypt was decreased as compared to untreated ovariectomized mice, the decrease being greater after a single injection than after multiple injections of estrogen, and the vacuolated‐columnar cell line being affected more than mucous cell line. Meanwhile, the crypt size as well as the population size of differentiated cells in the crypt failed to return to normal after estrogen treatments. Thus, estrogen did not promote differentiation of epithelial cells in the crypt.
The longitudinal orientation of structures in the subendothelial space of rat aorta
Authors: Buck Robert C. 
Published: February 2005

AbstractThe aortas of rats were sectioned parallel to the endothelial surface for the purpose of studying the orientation of structures in the endothelium and subendothelial space relative to the long axis of the aorta. Microfilament bundles within endothelial cells, and the associated anchoring filaments of the subendothelial space, lay parallel to the long axis. Other filamentous structures of the subendothelium, namely, the bundles of very fine microfibrils and the somewhat larger elastic fibers, also showed a generally longitudinal orientation, although they frequently deviated from this arrangement, and were not perfectly straight. Another group of filaments in the deepest part of the subendothelial space lay in the transverse axis of the aorta. These filaments appeared to represent the most superficial component of the internal elastic lamina.In addition to the longitudinally orientated fibrillar structures, the subendothelium also contained longitudinal cytoplasmic folds, or rugae, projecting from the deep surface of the endothelial cells.It is concluded that contact‐guidance by structures having a pronounced longitudinal orientation within the subendothelial space may be responsible for creating the longitudinal arrangement of smooth muscle cells seen in this layer of the arterial wall with aging, and with certain types of pathological change.
Differential response of myofibrils and 10‐nm filaments to a cocarcinogen
Authors: Toyama Y. , West C. M. , Holtzer H. 
Published: February 2005

AbstractMultinucleated myotubes containing large numbers of striated myofibrils and large numbers of longitudinally‐oriented 10‐nm filaments were treated with the cocarcinogen phorbol‐12‐myristate‐13‐acetate (PMA) for 24, 48 or 72 hours. The inhibitory effects of PMA on the accumulation of myofibrils was evident within 24 hours, and by 72 hours virtually all striated myofibrils had disappeared. In contrast, the density of the 10‐nm filaments was greatly enhanced in these myofibrildepleted myotubes. These effects were not due to a generalized cytotoxicity, for PMA stimulated the replication of the presumptive myoblasts and fibroblasts present in these cultures. 24 hours after removing the PMA, these myotubes assembled a new set of striated myofibrils and the density of 10‐nm filaments diminished proportionately.
The secretion of mullerian inhibiting substance by cultured isolated sertoli cells of the neonatal calf
Authors: Price J. Michael 
Published: February 2005

AbstractSertoli cells have been isolated from the newborn calf testis using a combination of mechanical and enzymatic disruption. Testicular fragments, previously chopped into 1‐mm pieces, are digested in an enzyme mixture consisting of hyaluronidase, collagenase, trypsin and DNAse, followed by a second digestion in trypsin and DNAse. Isolation of the resulting cellular fractions by sedimentation with unit gravity produces an aliquot of Sertoli cells which is over 95% pure when examined by light and electron microscopy. Cultures of these cells grow rapidly and produce Mullerian Inhibiting Substance as evidenced by their ability to cause the involution of the Mullerian duct of the female fetal rat when co‐cultured in an organ‐culture assay system.
Scanning electron microscopy of the subarachnoid space in the dog: Evidence for a non‐hematogenous origin of subarachnoid macrophages
Authors: Merchant Randall E. , Low Frank N. 
Published: February 2005

AbstractInjection of viable BCG into the subarachnoid space of immunized and non‐immunized dogs produced a 10‐fold increase in the populations of pial free cells. In immunized animals injected three days previously with BCG, stereoscopic SEM revealed that many pial cells had rounded up and were protruding into the subarachnoid space. With continued rounding these cells took on amoeboid characteristics, with shapes that suggested a capacity for cell movement. Internally, these pial cells possessed an increased volume of perinuclear cytoplasm and organelles. Reactive pial cells could be distinguished from macrophages of presumed hematogenous origin on the basis of their surface morphology. These findings suggested that pial cells had the ability to alter their normal structural and behavioral characteristics and to become macrophage‐like under these conditions of secondary challenge by BCG.
Fine structure of the liver in the larval lamprey, Petromyzon marinus L.; Hepatocytes and sinusoids
Authors: Peek W. D. , Sidon E. W. , Youson J. H. , Fisher M. M. 
Published: February 2005

AbstractThe ultrastructure of hepatocytes, bile canaliculi, and hepatic sinusoids of the larval lamprey, Petromyzon marinus, was examined using thinsectioned and freeze‐fractured tissues. The liver is a “tubular gland” with hepatocytes arranged in a tubular fashion around large bile canaliculi. Hepatocytes are roughly conical in shape, with their tapered apices facing a bile canalicular lumen. They possess extensive rough and smooth endoplasmic reticulum, a well‐developed Golgi complex, abundant mitochondria, and varying numbers of large secondary lysosomes. Both secondary lysosomes and the Golgi complex are concentrated in the apical or peribiliary cytoplasm, indicating a possible role in bile secretion. The apical surfaces of the hepatocytes bear numerous elongate microvilli and occasional cilia, which project into the bile canaliculi. The hepatocytes are joined, apically, by junctional complexes composed of zonulae occludentes and adhaerentes. In freeze‐fracture, the zonulae occludentes are of variable apicobasal depth and consist of honeycomb‐like meshworks of fibrils. Spaces of variable width frequently appear in the P‐face grooves, indicating that the zonulae occludentes are “leaky.” Numerous communicating (gap) junctions join the hepatocytes laterally. Varying numbers of lateral microvilli project into the intercellular spaces and, basally, the plasma membrane is deeply infolded, resulting in the formation of apparently interdigitating basal processes resting upon a thin basal lamina. Sinusoids are composed of both a heavily‐fenestrated, continuous endothelium, and phagocytic reticulo‐endothelial (Kupffer) cells. Despite the difference in arrangement of their hepatocytes, the mammalian and lamprey livers show similar ultrastructural features.
Aglomerular pathways in intrarenal microvasculature of aged rats
Authors: Casellas Daniel , Mimran Albert 
Published: February 2005

AbstractBy means of silicone rubber injections, we confirmed the existence of several types of aglomerular arterial pathways within kidneys of aged rats. In superficial cortex some interlobular arteries divide to form aglomerular branches (Ludwig's arterioles) towards cortex corticis. In juxtamedullary cortex these pathways are relatively more numerous, they comprise: (a) Vasa Recta Vera, (b) glomeruli in which afferent and efferent arterioles form a continuous vessel and (c) glomeruli with two efferent vessels, one by‐passing glomerular tuft. In addition, results obtained in the rat by the microsphere technique are in agreement with our morphological observations.
Morphology of the epithelium of the extratesticular rete testis, ductuli efferentes and ductus epididymidis of the adult male rabbit
Authors: Jones R. , Hamilton D. W. , Fawcett D. W. 
Published: February 2005

AbstractThe fine structure of the epithelium lining the extratesticular rete testis, ductuli efferentes and ductus epididymidis of the rabbit has been investigated. In the ductuli efferentes the epithelium is composed of two cell types, principal cells and ciliated cells. The latter cell type is distinguished from principal cells by the presence of cilia projecting into the lumen and the position of the nucleus in the apical half of the cell. Principal cells in this segment are characterized by micropinocytotic vesicles on the surface plasma membrane and a variety of small dense bodies scattered throughout the cytoplasm. In the ductus epididymidis basal cells replace ciliated cells as the second cell type, but differences between various segments of the epididymis are related to the fine structure of the principal cells. In the proximal caput epididymidis (Nicander's region 1) the principal cells are tall with long microvilli. They typically contain a small Golgi apparatus and a cluster of dense bodies adjacent to the nucleus. In the distal caput epididymidis (Nicander's regions 2–5) the apical cytoplasm of principal cells is filled with numerous micropinocytotic vesicles and large multivesicular bodies; these features are interpreted as signs of absorptive activity. The multivesicular bodies are absent from the cytoplasm of principal cells in the corpus epididymidis (Nicander's region 6) and, instead, numerous elements of smooth endoplasmic reticulum, a large Golgi apparatus, lipid droplets and dense bodies characterize principal cells in this segment. Towards the proximal cauda epididymidis (Nicander's region 7), the number of dense bodies (lysosomes) in the cytoplasm increases considerably. In the globose cauda (Nicander's region 8), the principal cells are reduced in height, and in addition to the features described in region 7, are characterized by a concentric array of rough endoplasmic reticulum in the basal cytoplasm. These observations are discussed in relation to the role of the epididymis in promoting the maturation and survival of spermatozoa.