bluuebunny/crossref_metadata_2025_split huggingface dataset:
Artificial matrix barriers: A diffusion study utilizing dextrans and microspheres
Authors: Persky Bruce , Hendrix Mary J. C. 
Published: February 2005

AbstractEight artificial matrices (AMs) were evaluated for the ability to restrict the passage of diffusion probes. Three AMs were composed exlusively of interstitial type I collagen (Col I) and differed from each other in thickness only. Four AMs consisted of reconstituted basement membrane (RBM) ‐coated polycarbonate filters (containing 10 μm diameter pores) and also only differed in thickness. One AM consisted of an uncoated 10 μm pore polycarbonate filter. The diffusion probes were uncharged fluorescein isothiocyanate‐labeled dextrans, having molecular weights of 17,900, 42,000, 71,200, and 148,900 and negatively charged latex microspheres, having diameters of 0.08, 0.30, and 0.95 μm. Probes were applied to the AMs, incubated for 72 hr at 37°C, and then analyzed spectrophoto‐metrically. Dextran passage was increasingly restricted for Col I matrices as either molecular weight or collagen thickness increased (range 7% to 0.7%). Thin RBM‐coated filters were more permeable to dextrans (range 100% to 30%) than Col I matrices. The diffusion rate of microspheres for Col I matrices (range 3.5% to 0) was similar to both thick and thin RBM‐coated filters (range 4% to 0). The uncoated filter permitted the most diffusion for both dextrans and microspheres (range 100% to 7%). These data demonstrate that the AMs presented in this study will allow direct observation of the degradative and migratory potential of cells in vitro as they interact with various extracellular matrices.
Age‐related immunohistochemical studies of A and D cells in pancreatic islets of C57BL/6J mice
Authors: Slavin Bernard G. , Lerner Steven P. 
Published: February 2005

AbstractSections of pancreatic islets from C57BL/6J mice aged 3, 14, and 24 months, consisting of islets derived from the dorsal primordium (DPI) and from the ventral primordium (VPI), were immunostained using the peroxidase‐antiperoxidase (PAP) procedure for localization of glucagon (A cells) and somatostatin (D cells). The density (A or D cell area/islet area) of immunopositive cells were determined using computer‐assisted image analysis. The density of A cells was significantly less in VPI of 14‐ and 24‐month‐old mice compared to 3‐month‐old mice. The density of A cells in 24 month DPI was less than 3 month DPI but no different from 14 month DPI. The mean area (μm2) of A cells (only in DPI) was significantly less at 24 months compared to the 3 and 14 month groups. There were no differences in somatostatin staining when comparing the three age groups, although at all ages the density of D cells was always greater in the DPI. In conclusion, the major difference between the young and older mice was a deficiency of glucagonstained cells in older mice. These results might be important in explaining improved glucose tolerance in aged C57BL/6J mice.
Glycoconjugate unique to migrating primordial germ cells differs with genera
Authors: Fazel A. R. , Schulte B. A. , Spicer S. S. 
Published: February 2005

AbstractPrevious cytochemical studies showing that rat primordial germ cells (PGCs) possess a unique surface glycoconjugate containing terminal α‐Nacetylgalactosamine were extended in this study to determine whether a similar distinctive glycoconjugate coats the surface of PGCs in the mouse. The results showed that mouse PGCs fail to react with peroxidase‐conjugated lectins specific for localizing glycoconjugate with terminal N‐acetylgalactosamine. All available lectin conjugates with affinity for other terminal sugars or internal sugar linkages also failed to stain mouse PGCs except for the conjugates that bind to α‐fucose. One fucose‐specific lectin conjugate stained only PGCs in the early mouse embryo but stained additional sites in more mature embryos and lost reactivity with PGCs after gestational day 14. Another fucose‐specific conjugate stained PGCs until day 15, but with less selectivity, and a third such conjugate bound to several sites, but not to PGCs. The results suggest that the developmental mechanisms mediating cellular interaction, migration, and differentiation may be similar in different genera, but the specific structure of the cell surface glycoconjugate involved in these mechanisms differs.
Cytochemical analysis of the notochord in early rhesus monkey embryos
Authors: Wilson Doris B. , Hendrickx Andrew G. 
Published: February 2005

AbstractFunctional differentiation of the notochord in rhesus monkey embryos at stages 11–12 (25–28 days of gestation) was analyzed by means of ultrastructural cytochemistry. The notochordal cells exhibited well developed Golgi complexes, rough endoplasmic reticulum, mitochondria, and numerous coated vesicles. Large irregular intercellular spaces were common, and some contained fibrils and particulate matter similar to that observed in the perinotochordal space immediately surrounding the notochord. With the glycogen‐specific thiocarbohydrazide‐silver proteinate technique, solitary particles as well as large aggregates of glycogen were present within the notochordal cells. The center of some aggregates was electron lucent and contained collapsed membranous structures. The results indicate that as early as stage 11 the nonhuman primate notochord exhibits ultrastructural features suggestive of secretory activity and cytological complexity.
Formation of ectopic neurepithelium in chick blastoderms: Age‐related capacities for induction and self‐differentiation following transplantation of quail Hensen's nodes
Authors: Dias Mark S. , Schoenwolf Gary C. 
Published: February 2005

AbstractHensen's node, regarded as the avian and mammalian homologue of Spemann's neural inducer (i.e., the amphibian dorsal blastoporal lip), has been transplanted in many previous studies to the germinal crescent of avian blastoderms to examine ectopic neural induction. All these studies have suffered from one or more major shortcomings, the most significant of which has been the lack of a reliable cell marker to determine the contributions of graft cells to ectopic embryos. In the absence of such marker, induced (i.e., derived from the host) and self‐differentiated (i.e., derived from the graft) neurepithelium cannot be distinguished from one another with certainty. We have transplanted quail Hensen's nodes to chick host blastoderms and have subsequently used the quail nucleolar heterochromatin marker to identify graft cells unequivocally. We systematically varied both donor and host ages (i.e., stages 3–8 and 3–5, respectively) to examine the effects of age on ectopic neural induction and self‐differentiation. Our results demonstrate that the age of the donor is more critical than that of the host over the stages examined. With advancing donor age, the frequency of host induction decreases, while the frequency of graft self‐differentiation increases. Previous studies not using cell markers have concluded that the craniocaudal level of the induced neuraxis is determined by the age of the donor, that is, young donors induce cranial neuraxial levels, whereas old donors induce caudal levels. By contrast, we found that with grafts from older donors, neurepithelium was more commonly self‐differentiated rather than induced and that progressively more caudal levels of the neuraxis self‐differentiated with advancing donor age. Induction of caudal neuraxial levels never occurred in the absence of induced cranial levels. The frequency of neural induction was inversely correlated with the age of the donor and directly correlated with the quantity of graft endodermal cells contributed to the ectopic embryo, supporting a previous assertion that in avian embryos, the earliest and principal source of neural inducer lies within the endoderm rather than mesoderm. From our results, we propose that the role of neural induction is to produce neurepithelium of unspecified regional character, and that the formation of regional character depends on subsequent morphogenetic events.
Endotoxin‐induced endothelial injury and subendothelial accumulation of fibronectin in rat aorta
Authors: Kang Yuan‐Hsu , Williams Robert 
Published: February 2005

AbstractEndotoxin (lipopolysaccharide, LPS) induces endothelial injury in arterial vessels. Fibronectin is known to be involved in cell attachment and wound repair. The present study was designed to elucidate the effect of LPS on the production and distribution of fibronectin in relation to injury and repair in rat aortic endothelium. Male Sprague‐Dawley rats were sacrificed for ultrastructural and immunocytochemical evaluations at 1, 3, 6, 24, and 48 hr after a single intravenous injection of 1.5 or 3 mg/kg body weight E. coli LPS. Apparent morphological signs of endothelial injury, including cell detachment, denudation, cell death, and edema were observed 1–48 hr after injection. Parietal thrombosis and leukocyte diapedesis were also observed in the aorta. A profound increase in subendothelial fibronectin was found following LPS treatment. However, no distinct change in intracellular fibronectin was observed in the same endothelium until 24 hr after injection. Using horseradish peroxidase (HRP) and anti‐fibronectin‐HRP antibody as tracers, LPS was also found to increase permeability and extravasation of plasma proteins (fibronectin) of the aortic endothelium. The increase of subendothelial fibronectin possibly resulted from increased influx and sequestration of plasma fibronectin. This increase may provide a firm substratum for reendothelialization after vascular injury.
Ultrastructural analysis of the acrosome reaction in a population of single guinea pig sperm
Authors: Flaherty Sean P. , Olson Gary E. 
Published: February 2005

AbstractCauda epididymal guinea pig spermatozoa are arranged in rouleaux, with the sperm heads stacked one on top of the other; the plasma membranes over the apical segment of the acrosomes of adjacent sperm are linked and form non‐fusigenic “junctional” zones. A complex structural and temporal sequence of membrane fusions occurs during the acrosome reaction of guinea pig sperm in rouleaux. In this study, we have devised a procedure for dispersing the rouleaux and isolating a population of single, motile guinea pig sperm, and have investigated the ultrastructural features of the acrosome reaction in single sperm to determine if the pattern of membrane fusions is different from sperm in rouleaux. The rouleaux were dispersed using trypsin, and damaged cells were removed by passing the sperm suspension through a glass bead column; a population of 70–90% motile, acrosome‐intact, single sperm was obtained. Sperm were then induced to undergo lysolecithin‐mediated, “synchronous” acrosome reactions, and processed for transmission electron microscopy. The acrosome reaction involved a complex sequence of membrane fusions between the plasma membrane (PM) and outer acrosomal membrane (OAM). On the convex surface of the apical segment, sheets of hybrid membrane and parallel arrays of hybrid membrane tubules formed; filaments were associated with the luminal surface of the residual OAM in these regions. Hybrid membrane vesicles were produced on the concave surface of the apical segment, but fusion was delayed relative to the convex surface. In the principal segment, branching arrays of hybrid membrane tubules formed and later vesiculated. Hence, in single guinea pig sperm, the sequence of membrane fusions is similar to sperm in rouleaux except that fusion occurs in regions of the apical segment which form the non‐fusigenic PM “junctional” zones in rouleaux. The results suggest that, regardless of whether the acrosome reaction in vivo occurs before or after rouleaux dispersion, it will involve a complex sequence of membrane fusions which is determined by the structural properties of the OAM and PM.
Spermiation and sperm maturation in the marmoset
Authors: Kumar R. Asok , Phillips David M. 
Published: February 2005

AbstractThe scanning and transmission electron microscopes were used to examine the processes of spermiation and sperm maturation in the marmoset. We observe that the heads of late spermatids are embedded in the apical aspect of the large sleeve‐like columnar portion of Sertoli cells. As spermiogenesis progresses, spermatids become associated with numerous small apical Sertoli cell extensions. These finger‐like processes undergo a sequence of changes during spermiation. Spermatozoa from the caput, corpus, and cauda epididymides were examined. In caput epididymis of marmoset, the apical segment of the spermatozoa extends well beyond the rostral edge of the nucleus and folds back on itself. In sagittal sections, the acrosome exhibits a distinct hook shape. In the corpus, the distinctive hookshaped apical segment of the acrosome is observed in some spermatozoa, but the apical extension is significantly smaller or projects out only slightly beyond the nucleus. In cauda epididymis, the extension is absent. A similar acrosomal hook has been reported in the pigtailed monkey, which is an Old World species. We suggest that changes in acrosome structure during sperm maturation may be fairly widespread among primates.
Location of the motoneurons supplying the rabbit pharyngeal constrictor muscles and the peripheral course of their axons: A study using the retrograde HRP or fluorescent labeling technique
Authors: Kitamura Seiichiro , Ogata Kimio , Nishiguchi Takahiko , Nagase Yoshitaka , Shigenaga Yoshio 
Published: February 2005

AbstractThe location of the motoneurons supplying the rabbit pharyngeal constrictor muscles (the superior and the middle constrictors, and the thyropharyngeus and the cricopharyngeus; the last two collectively compose the inferior constrictor) was investigated with intramuscular injection of HRP or the fluorescent tracer nuclear yellow into the individual muscles. Moreover, the peripheral course of their axons was investigated by injection of HRP into all of the pharyngeal constrictors in conjunction with intracranial severing of either the vagus or the glossopharyngeal nerves. The pharyngeal constrictor motoneurons were ipsilaterally located within a subdivision of the nucleus ambiguus which is formed by a compact arrangement of the smallest neurons of the nucleus and situated in the rostral half of the nucleus. We named that subdivision the compact cell group (CoG). Axons of the pharyngeal constrictor motoneurons traversed the vagal rootlets. The rostrocaudal extent of the pharyngeal constrictor motoneurons covered almost the entire length of CoG at a level from about 500 to 2,900 μm rostral to the obex, with their number being most numerous in the middle one‐third level of the CoG. Although the motoneurons of the superior constrictor, those of the middle constrictor, and those of the thyropharyngeus and the cricopharyngeus overlapped considerably in location, they tended to be arranged rostrocaudally in that order. At the middle one‐third level of the CoG, where the CoG is subdivided into dorsomedial and ventrolateral subgroups of neurons, the superior and the middle constrictor motoneurons were confined to the medial portion of the dorsomedial subgroup, while the inferior constrictor motoneurons were distributed throughout its entirety.
Cytoskeleton in microridges of the oral mucosal epithelium in the carp, Cyprinus carpio
Authors: Uehara Kiyoko , Miyoshi Masayuki , Miyoshi Sakuichiro 
Published: February 2005

AbstractMicroridges produce a characteristic fingerprint‐like pattern on the surface of fish oral mucosa. The cytoskeleton in these microridges was examined by immunofluorescence microscopy and transmission electron microscopy after detergent extraction and decoration with myosin subfragment 1. The effect of cytochalasin B on microridges was probed with scanning electron microscopy. Immunofluorescence microscopy revealed that actin filaments were present throughout the periphery of the epithelial cells and were especially localized beneath the free surface of the epithelium. In thin sections treated with Triton X‐100, the majority of filaments in the microridges and their bases were found to be actin filaments and a plexus of keratin filaments that underlay the network of actin filaments. A part of the plexus of keratin filaments entered the microridges. After extraction with Triton X‐100 and decoration with myosin subfragment 1, decorated actin filaments were found in the microridge cores, connected to the keratin filaments. The keratin filaments aggregated in the pattern of microridges and a few of them protruded into the microridges. Treatment with cytochalasin B caused microridges to disappear or to become thinner and lower or to change short or microvillus‐like microridges. When most microridges disappeared, the surface of the superficial cells was prominently swollen, but the cell boundaries were fastened, and the microridges in the periphery were preserved. On the basis of these observations, the possible roles of actin and keratin filaments in the maintenance and the formation of microridges are discussed.
Colloidal gold localization of type IV collagen in the extracellular matrix of rat gastric mucosa: Influence of alcohol and prostaglandin
Authors: Rightor Kathryn S. , Mitchell Philip A. , Miller Thomas A. , Schmidt Karmen L. 
Published: February 2005

AbstractThe effect of acute alcohol exposure on the gastric mucosal basal lamina, and its major structural protein type IV collagen, was assessed by transmission electron microscopy (TEM) and immunogold (IG) labeling of this collagenous material. Fasted rats orally received either 50% or 100% ethanol. Five or 60 minutes later animals were sacrificed and mucosal samples were obtained from the glandular epithelium for TEM or IG localization of type IV collagen. For IG studies, the number of gold particles/area lamina densa was quantified in interfoveolar, pit, and gland regions as an index of the molecular integrity of type IV collagen. Both ethanol concentrations induced epithelial exfoliation with pleating of the denuded lamina densa. Absolute ethanol, and to a lesser extent 50% ethanol, caused frequent rupture of a thickened, precipitated lamina densa. Immunolabeling of type IV collagen varied with the experimental protocol. In control tissues exposed to oral saline, binding was greatest in the interfoveolar zone. Low binding occurred with 100% ethanol in all regions when compared with controls, but 50% ethanol evoked significantly higher binding in interfoveolar regions, in a similar fashion to controls. In additional studies in which 16,16 dimethyl prostaglandin E2 (PGE2) (10 μg/kg) was injected subcutaneously prior to oral ethanol exposure, PGE2 pretreatment prevented the large decrease in IG binding induced by absolute ethanol, but the level still remained significantly less than with corresponding controls. In contrast, pretreatment with PGE2 prior to 50% ethanol exposure restored type IV collagen immunolabeling to control levels. These results indicate that ethanol induces a concentration‐dependent lowering of IG binding to type IV collagen which also effects its reversibility by PGE2.
Freeze‐fracture observations on human fetal kidney in serum‐free organ culture
Authors: Brière Normand , Cabana Charles , Magny Pierre 
Published: February 2005

AbstractThe current study was undertaken to examine and characterize junctional complexes, through freeze‐fracture, in developing human fetal kidney and in cultured renal explants maturing in vitro. Tissue specimens were cultured for 7 days in Leibovitz's L‐15 medium in the absence of serum or hormones. In uncultured explants, cells in the different nephron segments were joined by zonulae occludentes which consisted of ridges on the P‐face and grooves on the E‐face of lateral membranes. Tight junction composition was heterogeneous and complexity increased from proximal to collecting tubules. Proximal tubule cells were also characterized by the presence of gap junctions and a brush border. Podocytes were joined by macular junctions, while zipper‐like junctions were observed between collecting duct cells. Intercalated cells were decorated with rod‐shaped intramembrane particles on lateral and apical membranes, instead of the usual spherical particles present in other cells. All these structures could be observed at various intervals during tissue culture, indicating the preservation of ultrastructural integrity of the explants. These observations extend and support previous studies made at the light and electron microscopic levels. Thence, the present culture model constitutes a valuable tool to study the direct effect of growth factors on nephrogenesis.
Characteristics of end‐plates formed in mouse skeletal muscles reinnervated by their own or by foreign nerves
Authors: Bewick Guy S. , Tonge David A. 
Published: February 2005

AbstractMorphological and electrophysiological techniques were used to study the neuromuscular junctions of soleus and extensor digitorum longus muscles in normal mice and 6 months after reinnervation by either their original or foreign nerves. In muscles reinnervated by foreign nerves, there were increased incidences of morphological abnormalities, including ultra‐terminal axonal sprouting, multiaxonal innervation of end‐plates, and ectopic synapse formation, as compared with both normal muscles and muscles reinnervated by their correct nerves. In spite of the morphological abnormalities, however, there was no evidence that the effectiveness of synapses (as estimated from the mean quantal content, m, of end‐plate potentials) formed between nerves and inappropriate muscles was impaired. As had also been found in normally innervated muscles, the value of m was again higher in extensor digitorum longus than in soleus following reinnervation by inappropriate nerves. These results suggest that in mammals, when muscles are reinnervated by foreign nerves, mechanisms exist to maintain the efficacy of neuromuscular transmission, in contrast to the situation in amphibians (Sayers and Tonge, 1982: J. Physiol. (Lond.), 330:57–68). The abnormalities observed in this study following reinnervation may be a morphological manifestation of these corrective mechanisms.
Changes of glycoconjugate contents of the zona pellucida during oocyte growth and development in the golden hamster: A quantitative cytochemical study
Authors: Roux Emmanuelle , Frederick W. K. Kan 
Published: February 2005

AbstractWe demonstrated here with the high resolution lectin‐gold approach and quantitative analysis, changes of glycoconjugates in the hamster zona pellucida (ZP) during oocyte growth and development in the ovary and the oviduct. Glycoconjugates which contain N‐acetyl‐D‐galactosamine as terminal sugar residues are absent in the ovary but are secreted by secretory cells in the oviduct and are added to the ZP of superovulated oocytes during oviductal transit. Glycoconjugates which carry sialic acid as terminal sugar residues appear to be acquired mainly from the ovary. The oviduct contributes little of this particular component to the ZP during the transit of oocytes in the oviduct. On the contrary D‐galactose and N‐acetylglucosamine associated glycoconjugates, added to the ZP in ovarian follicles, are also secreted by non‐ciliated oviductal epithelial cells and these secretory products are transferred to the ZP in significant amount during passage of the oocyte through the oviduct. Lectin‐gold labeling of the ZP of superovulated oocytes reveals homogeneous distribution of gold particles throughout the zona matrix. Thus, we conclude that the ZP of hamster superovulated oocytes consists of glycoconjugates that may derive from different origins. Deposition of ZP glycocomponents begins in the ovary. Similar and new glycoconjugates, secreted by oviductal non‐ciliated secretory cells, are added to the ZP of oocytes during oviductal transit. At this stage the ZP is made up of a homogeneous matrix of glycoconjugates.