bluuebunny/crossref_metadata_2025_split huggingface dataset:
The contribution of the inferior endocardial cushion of the atrioventricular canal to cardiac septation and to the development of the atrioventricular valves: Study in the chick embryo
Authors: De La Cruz María V. , Giménez‐Ribotta Minerva , Saravalli Oscar , Cayré Raúl 
Published: February 2005

AbstractThe contribution of the inferior endocardial cushion of the atrioventricular canal to cardiac septation and to the development of the atrioventricular valves was studied in the chick embryo by in vivo labelling techniques. The study was performed in White Leghorn chick embryos in which the dorsal cushion was labelled at stage 20‐21 (Hamburger and Hamilton, 1951), when the endocardial cushions were not yet fused. The embryos were sacrificed at stage 35 (mature heart).These experiments allow us to conclude that the inferior atrioventricular cushion gives origin to: (a) that part of the cardiac septum between the septal insertion of the antero‐septal leaflet of the mitral valve and the fibrous ridge which is the equivalent to the human septal leaflet of the tricuspid valve (atrioventricular septum); (b) the region of the interatrial and the interventricular septa adjacent to the atrioventricular septum; (c) the portion of the antero‐septal leaflet of the mitral valve which inserts into the septum; (d) the fibrous ridge corresponding to the septal leaflet of the tricuspid valve.Microdissection shows that, when they appear at stage 18, the superior and inferior endocardial cushions of the atrioventricular canal are in continuity, without boundaries, with both the interatrial and interventricular septa. Therefore, each atrioventricular orifice opens into its corresponding ventricle, there being no stage in the development of the chick embryo heart in which the atrioventricular orifices are connected to the left ventricle at the same time.The development of the atrioventricular canal is similar in the chick and human.
Cytodifferentiation of the nonciliated bronchiolar epithelial (Clara) cell during rabbit lung maturation: An ultrastructural and morphometric study
Authors: Plopper Charles G. , Alley Janice L. , Serabjitsingh Cosette J. , Philpot Richard M. 
Published: February 2005

AbstractThe nonciliated bronchiolar epithelial (Clara) cell of adult lung is commonly defined by two cellular components: abundant agranular endoplasmic reticulum (AER) and electron‐dense ovoid secretory granules. These reflect the Clara cell's proposed functions as the source of bronchiolar surface secretions and the site of xenobiotic metabolism via the cytochrome P‐450 monooxygenase system. Since previous studies have indicated that Clara cells may not attain a fully functional state until some weeks after birth, the present study was undertaken to characterize systematically the differentiation of this cell type during lung maturation. Lungs were fixed by airway infusion with glutaraldehyde/paraformaldehyde (550 mOsm, pH 7.4) from at least three male rabbits at each of the following ages: 24, 27, and 30 days fetal, and 0–1 day, 3–4 days, 1, 2, 3, 4, 5, 8, 12, 15, 17, and 25 weeks postnatal; and pieces were processed for transmission electron microscopy by a selective embedding procedure. Quantitation was performed on electron micrographs (at 15,750 x) of cell profiles, which included the base, apex, and nucleus. Volume fractions of constituents of a minumum of 30 cells per animal (8 weeks and younger) and 10 per animal in older groups, were estimated by point counting with a Weibel 168‐point test grid. Cell and nuclear size were estimated with a computerized digitizer (Zeiss Videoplan). Nonciliated cells of prenatal animals had large amounts of cytoplasmic glycogen (over 60% of the cell cytoplasm), few mitochondria (less than 15%), little granular endoplasmic reticulum (GER) (20%), minimal AER (less than 5%), and no granules. Postnatal animals 2 weeks of age and younger were similar, except for the presence of secretory granules and slightly more abundant AER (5 to 20%). By 4 weeks postnatal age, nonciliated cells resembled that of older animals with abundant apical AER (over 40%), secretory granules, little glycogen (11%), and GER (10%). We concluded that (1) the Clara cell is immature at birth; (2) differentiation occurs primarily during weeks 3 and 4 of postnatal life; (3) vast amounts of cytoplasmic glycogen are characteristic of the undifferentiated cell; and (4) four cellular constituents, AER, glycogen, mitochondria, and GER, undergo significant shifts in abundance during differentiation. These shifts appear to be in the sequence expected of a cell type undergoing the initiation of biosynthesis of secretory products and biogenesis of agranular endoplasmic reticulum.
Estimation of cell numbers and volumes of bronchiolar epithelium during rabbit lung maturation
Authors: Hyde Dallas M. , Plopper Charles G. , Kass Philip H. , Alley Janice L. 
Published: February 2005

AbstractTo estimate the numbers and volumes of bronchiolar epithelial cells during lung maturation, we examined rabbits at three time points, 30 days gestation and 4 and 17 weeks postnatal age. Morphometric measures (mean caliper diameter, surface area, and volume) of nonciliated and ciliated bronchiolar cell nuclei, using computer modeling from serial sections, showed a significant decrease in nuclear size for both cell types and a significant increase in cell volume for the nonciliated bronchiolar cell during lung maturation. A shape coefficient (β) proved to be the most efficient estimator of the number of cells per unit volume when it was used with estimates of the number of nuclei per unit area and the volumetric density of nuclei. Two‐dimensional estimates of bronchiolar epithelial cell abundance (the number of nuclei per unit length or area) significantly underestimated the percentage of nonciliated bronchiolar cells as compared to three‐dimensional estimates for rabbits 17 weeks of age. We have shown an inverse relationship between nonciliated and ciliated bronchiolar cell abundance during lung maturation. Nonciliated cells decreased while ciliated cells increased.We have confirmed that cytodifferentiation of the nonciliated bronchiolar cell occurs within the first 4 weeks of postnatal development. The volume of the nonciliated bronchiolar cell increased about twofold during development. Because of the concomitant decrease in nuclear volume, the cytoplasm of the cell showed an even greater increase in volume. Within the cytoplasm of the nonciliated bronchiolar cell, glycogen significantly decreased, and agranular endoplasmic reticulum (AER) and mitochondria significantly increased in volume during development. The biosynthesis of AER closely correlated with pharmacological studies of xenobiotic metabolism during rabbit lung maturation.
Immunocytochemical staining of isolated rat sertoli cells for anti‐FSHβ
Authors: Hon Charlene A. , Gardner Paul J. , Leuschen M. Patricia 
Published: February 2005

AbstractSertoli cells are a primary target for the action of follicle‐stimulating hormone (FSH) in the testis. The purpose of this investigation was to verify ultrastructurally that FSH binds to receptors on the plasma membrane of isolated rat Sertoli cells.A reltaively pure aliquot of Sertoli cells was obtained by first dissociating testicular tissue from immature rats with collagenase and then centrifuging the suspension in Percoll density gradients. Pre‐embedding staining with the peroxidase anti‐peroxidase (PAP) complex technique using anti‐FSHβ as the primary antiserum localized endogenous receptor‐bound FSH on the plasma membrane of isolated Sertoli cells. Staining was considered to be specific since membranes of Sertoli cells derived from hypophysectomized rats were not stained when subjected to the same procedure.Cytoplasmic vesicles in Sertoli cells from experimental, control, and hypophysectomized groups also stained with PAP. Staining of these structures appeared to be specific since it was obliterated by preabsorption of anti‐FSHβ with FSH. Preabsorption with luteinizing hormone (LH) did not affect the staining of cytoplasmic vesicles.The results of this investigation provide the first evidence for ultrastructural localization of specific binding sites for anti‐FSHβ on the cell membrane of isolated Sertoli cells using an unlabeled antibody technique, and they further support the contention that Sertoli cells are a primary target for the action of FSH.
Diurnal variations in the photoreceptor synaptic terminals of the newt retina
Authors: Ball Alexander K. , Dickson D. Howard 
Published: February 2005

AbstractNewt photoreceptor synaptic terminals undergo a variety of morphological changes over a 24‐hr (LD 12:12) cycle. During the day, densecored synaptic vesicles were found to increase in number and accumulate near the synaptic lamellae; during the dark phase, the dense‐cored vesicles decreased in number, while large clear vesicles and profiles of smooth endoplasmic reticulum increased in frequency. The most marked change in photoreceptor synaptic terminal morphology occurred after 10 hr of darkness, at 0730 hr. At this time, photoreceptor synaptic terminal cross‐sectional area was found to increase dramatically. Morphometric analysis showed that the number of synaptic vesicles in these terminals remained constant throughout the day, as did the perimeter of photoreceptor terminal profiles. The observed increase in area of synaptic terminals at 0730 hr was found to be due to a decrease in the folding of the terminal plasma membrane. Qualitative observations showed endocytosis to be occurring at a rapid rate at this time as well; and since the number of synaptic vesicles and terminal perimeter did not change, exocytosis of synaptic vesicles was assumed to be occurring at an equally rapid rate. These findings support an extension to the hypothesis of Monaghan and Osborne (1975), suggesting that photoreceptor synaptic vesicles become “supercharged” with transmitter substance in the light.
Effects of progesterone on the oviductal epithelium in estrogen‐primed prepubertal beagles: Light and electron microscopic observations
Authors: Sawyer H. R. , Olson P. N. , Gorell T. A. 
Published: February 2005

AbstractA total of 45 prepubertal beagles 6 to 8 weeks of age were used to study the cytological changes that accompany regression of the oviductal epithelium. The oviductal epithelium in untreated pups consisted of undifferentiated low cuboidal cells that measured 10.3 ± 2.0 μm in height. In response to estradiol (E2), low cuboidal cells underwent hypertrophy, hyperplasia, and cytodifferentiation and gave rise to columnar ciliated and secretory cells. After 12 days of E2 treatment the epithelium was fully differentiated and measured 29.4 ± 2.6 μm in height with 56% of the cells possessing cilia. When E2 treatment was continued for an additional 12 days, the epithelium was maintained in a differentiated state. However, if E2 treatment was terminated or progesterone (P) given alone or in conjunction with E2, the oviductal epithelium regressed and after 6 days was composed of low cuboidal cells that ranged in height from 9 to 14 μm with approximately 25% of the cells possessing cilia. A variety of cytological changes characterized the process of regression. The most immediate signs that regression was underway were a reduction in the height of the epithelium and the presence of cells with shrunken, pleomorphic nuclei that lacked prominent nucleoli. Degenerative events included: (1) pinching off and shedding of the apical cytoplasm of cells comprising the epithelium, (2) extrusion of whole cells and/or nuclei, and (3) resorption of cilia and basal bodies. During the first 6 days following E2 withdrawal or P treatment, macrophages and cellular debris were frequently present within the lumen of the oviduct. The process of regression did not proceed synchronously throughout the ampulla of the oviduct, nor did all cells appear to degenerate in the same manner. The cytological changes that accompanied oviductal regression following P treatment were identical to those observed following E2 withdrawal. Results from experiments conducted in the present study show that: (1) E2 induces the oviductal epithelium to differentiate and is required to maintain the epithelium in a differentiated state, (2) E2 withdrawal or P treatment causes the oviductal epithelium to regress, (3) at least three distinct degenerative processes are involved in the transition of columnar ciliated and secretory cells into low cuboidal cells, and (4) regression does not occur synchronously throughout the ampulla region of the oviduct.
Organogenesis of the mouse extensor digitorum logus muscle: A quantitative study
Authors: Ontell Marcia , Kozeka Kenneth 
Published: February 2005

AbstractA quantitative analysis of the pattern of development and growth of the fetal extensor digitorum longus muscle of the 129 ReJ mouse was carried out in spaced, serial ultrathin sections with computer‐assisted morphometry. Muscle from 12‐, 14‐, 16‐, and 18‐day in utero mice and from newborn and 5‐day postnatal mice was analyzed to determine age‐related changes in such factors as the maximal girth and length of the muscle, the number of myotubes, the “cluster” frequency, and the diameters and lengths of the myotubes and muscle units. A distinct temporal pattern of development was established. It was quantitatively determined that a delay ≥ 2 days occurs between the formation of primary myotubes (present at 12 days in utero, and secondary myotubes (present at 16 days in utero)). By 16 days in utero, groups of myotubes, consisting of one primary myotube and a variable number of secondary myotubes, form “clusters” surrounded by a common basal lamina. Morphometric analyses of diameter distributions establish that most, if not all, secondary‐generation myotubes are formed in association with larger, more mature myotubes. Quantitative data support the hypothesis (Ontell and Kozeka, 1984) that cluster formation and cluster dispersion occur simultaneously, beginning sometime between 16 and 18 days in utero. By 18 days in utero, the adult number of myofibers is present in the developing muscle mass. Analyses of lengths and diameters of the same fibers establish that the pattern of growth of the last‐formed myotubes of the developing muscle mass is different from that of myotubes formed earlier in development.
Graded morphogenetic patterns during the development of the extraembryonic blood system and coelom of the chick blastoderm: A scanning electron microscope and light microscope study
Authors: Kessel Joan , Fabian Barry C. 
Published: February 2005

AbstractThis scanning electron‐ and light‐microscopic study traces the morphogenesis of the yolk‐sac vascular system and extraembryonic coelom in the chick blastoderm. The fate of the mesodermal cells in both the area opaca vasculosa (AOV) and the area pellucida (AP) is followed, and the cellular patterning in these two areas is compared. We describe new details of the formation of coelom lining in the AOV, and new observations of the tendency of the intravascular blood island cells of the AOV to become flattened and attenuated. The morphogenesis of the blood system and coelom is analyzed in terms of polarized morphological patterns with coordinates in two modes: proximodistal (from the AP to the AOV) and dorsoventral (from the ectoderm to the endoderm). By highlighting differences in the methods of formation of blood vessels and coleom lining in the AP and AOV, this paper resolves some paradoxes in the literature.
Sulfation and transport of basement membrane proteoglycans, as visualized by 35S‐sulfate radioautography in the endodermal cells of the rat parietal yolk sac
Authors: Fatemi S. H. , Leblond C. P. 
Published: February 2005

AbstractIn the hope of clarifying the biogenesis of basement membrane proteoglycans, an injection of 35S‐sulfate was given to concepti of 12‐day gestant Sherman rats. The parietal wall of the yolk sac (including endodermal cells and the associated basement membrane known as Reichert's membrane) was removed at times varying from 7 min to 24 hr after injection and processed for electron microscopic radioautography. Silver grains were counted over the organelles of endodermal cells as well as over Reichert's membrane.Between 7 min and 2 hr after 35S‐sulfate injection, radioactivity was observed in the endodermal cells, while from 4 to 24 hr it was mostly present in Reichert's membrane. Detailed distribution of the cellular radioactivity at 7 and 15 min showed about 20% in the rough endoplasmic reticulum (rER), 60% in the Golgi apparatus, and 8% in secretory granules. The radiactivity present in rER and Golgi apparatus decreased to low levels by 2‐‐4 hr after injection. In secretory granules, radioactivity increased to reach a peak at 2 hr and then declined; moreover, only the granules associated with the trans Golgi face were radioactive at early time intervals, while those scattered through the cytoplasm and along the cell surface became radioactive at later times. Between 4 and 24 hr, radioactivity became negligible over all cell organelles, while it was collected in Reichert's membrane.Biochemical reports indicate that when 35S‐sulfate is added to organ cultures of Reichert's membrane and endodermal cells, about 90% of the incorporated which these proteoglycans acquire sulfate are likely to be those labeled at 7 min after 35S‐sulfate injection, that is, the Golgi apparatus and to a lesser extent the rER, whereas some labeling of the secretory granules located at the trans Golgi face is explained by rapid acquisition of sulfated proteoglycans from the Golgi apparatus. Label later appears in the secretory granules along the cell surface and, eventually, in Reichert's membrane. It is concluded that secretory granules transport newly formed proteoglycans from the Golgi apparatus to the outside for deposition into Reichert's membrane.
Plasma membrane biogenesis in the avian salt gland: A biochemical and quantitative electron microscopic autoradiographic study
Authors: Sarras Michael P. , Rosenzweig Lionel J. , Addis John S. , Hossler Fred E. 
Published: February 2005

AbstractThe avian salt gland provides an ideal system for the study of plasma membrane (PM) biogenesis. Feeding ducklings 1% sodium chloride (salt stress) induces the secretory cells of the gland to synthesize large amounts of PM, which forms an extensive basolateral PM domain after 7–9 days of treatment. In the present study, the initial biosynthetic events following salt stress were investigated. In vivo studies using 3H‐uridine indicated that increased rates of RNA synthesis could be detected by 2 hr after the beginning of salt stress and continued through at least 12 hr. Under in vitro conditions, increased rates of protein and glycoprotein synthesis (as monitored by 3H‐leucine and 3H‐fucose incorporation, respectively) were also detected after 2 hr and continued through 7–9 days. Increased levels of Na, K‐ATPase, a specific secretory cell PM marker, were detected after 8 hr of treatment as monitored by specific activity and 3H‐ouabain binding. Sodium dodecyl sulfate‐polyacryl‐amide slab gel electrophoresis coupled with fluorography indicated that both 3H‐leucine and 3H‐fucose were incorporated into partially purified preparations of Na, K‐ATPase isolated after 12 hr. Light microscopic autoradiographic analysis of pulse‐chase experiments indicated that in secretory cells of 12‐hr salt‐stressed glands, 3H‐leucine‐ and 3H‐fucose‐labelled products reached the cell periphery by 1–2 hr after the initial pulse. The incorporation of both tritiated precursors was predominately associated with the secretory cells. Quantitative electron microscopic autoradiography indicated that 3H‐leucine is initially taken up by elements of the rough endoplasmic reticulum (RER) and cytoplasm (5 min postpulse), subsequently transported to and concentrated within components of the Golgi apparatus (10 min of chase), and ultimately incorporated into all domains of the plasma membrane of secretory cells by 1–2 hr of chase. The data is consistent with a flow of newly synthesized membrane components from RER to Golgi to plasma membrane and is analogous to the pattern previously found for the synthesis and processing of PM proteins in a wide variety of cell types.
Bimodal variations in subcellular structures of rat thyroid follicular cells during 24 hours: Fine structural and morphometric studies
Authors: Murakami Gen , Uchiyama Yasuo 
Published: February 2005

AbstractTo clarify 24‐hr variations in rat thyroid follicular cells under physiological conditions, their subcellular structures were examined at six evenly spaced times during 24 hr by using a morphometric technique. The volume, surface, and numerical densities of subcellular structures varied distinctly over each 24‐hr period, with a bimodal pattern. The cellular and nuclear volumes varied also bimodally over 24 hr. A decrease in the surface density of the apical plasmalemma at 1200 and 0000 hr coincided with an increase in volume density of cytoplasmic granules representing colloid droplets and dense bodies. Most granules (colloid droplets) appearing at these times were reduced in electron density. At other times, especially at 1600 and 0400 hr, morphometric parameters of rough endoplasmic reticulum (rER), Golgi complex, and subapical vesicles were prominently increased, although values for rER did not peak at 1600 hr. At these times, the volume densities of cytoplasmic granules, most of which were heterogeneous and of homogeneous electron density, were decreased. These findings coincided with immediate and subsequent reactions of follicular cells after injection of thyroid‐stimulating hormone (TSH). From the evidence, it seems likely that variations in follicular cells over a 24‐hr period reflect variations in blood TSH concentration. The total membrane areas of membrane components in follicular cells were calculated from the morphometric measurements. These areas fluctuated unimodally during 24 hr over a 65% range. This suggests that the membranes in follicular cells are subjected to cyclic degradation and regeneration during each 24‐hr period.
Changes in colloid droplets and dense bodies in rat thyroid follicular cells during 24 hours: Fine structural and morphometric studies
Authors: Uchiyama Yasuo , Murakami Gen , Igarashi Masaya 
Published: February 2005

AbstractTwo changes in cytoplasmic granules, corresponding to colloid droplets and dense bodies, in rat thyroid follicular cells during 24 hr were analyzed morphometrically in the apical, intermediate, and basal parts of the cells. The volume and surface densities of the cytoplasmic granules and their volumes and surface areas in the apical and intermediate parts varied bimodally over a 24‐hr day, being high at 1200 and 0000 hr and low at other times. In apical and intermediate regions, colloid droplets were predominant at 1200 and 0000 hr, whereas the cytoplasmic granules became heterogeneously or homogeneously electron‐dense at other times. In the basal part, these morphometric parameters were not synchronized with those in the other two regions, showing lower values. The basal cytoplasmic granules were heterogeneously or homogeneously electron‐dense. Small, homogeneously dense granules appeared in both the apical and intermediate parts and in the basal part with a certain time lag. These granules were often in contact with colloid droplets in the lumenal two parts at 1200 and 0000 hr. Their numerical densities were low in the apical part, but high in the intermediate and basal parts. These results suggest that newly formed colloid droplets migrate from the apical through the intermediate to the basal part, changing in appearance as they go. Moreover, it seems likely that small, homogeneously dense granules are a final form of cytoplasmic granule. They may be reused for degradation of colloidal protein.