bluuebunny/crossref_metadata_2025_split huggingface dataset:
Further serial transmission electron microscopy studies of auditory hair cell innervation in lizards and in a snake
Authors: Miller Malcolm R. , Beck Janet 
Published: February 2005

AbstractAuditory hair cells of three lizard and one snake species were studied by serial transmission electron microscopy (TEM) sections of two unidirectinal hair cells (UHC) and two bidirectional hair cells (BHC) and by nonserial section montages of each entire papilla cut at 2‐μm intervals across the papillar width. The unidirectional hair cell region of the agamid lizard, Acanthosaura crucigera, lacked efferent innervation. Another agamid lizard, Agama agama, studied by nonserial section only, lacked efferent innervation to the UHC. Afferent innervation to both the UHC and BHC of Acanthosaura was primarily exclusive (each nerve fiber innervates only one hair cell), although an occasional nerve fiber innervated two hair cells. Both the UHC and the BHC of the anguid, Celestus costatus, were exclusively innervated. Both hair cell types of the varanid, Varanus exanthematicus, were nonexclusively innervated (all afferent nerve fibers innervate two or more hair cells). The auditory papilla of the colubrid snake, Elaphe obsoleta, has only one type of hair cell and each is nonexclusively innervated. The numbers of afferent and efferent nerve fibers and of afferent synapses are presented in tabular form.
Characterization of different microenvironments at the surface of the frog's taste organ
Authors: Sbarbati A. , Zancanaro C. , Franceschini F. , Balercia G. , Morroni M. , Osculati F. 
Published: February 2005

AbstractWe used a panel of histochemical techniques to identify and characterize the cell‐associated extracellular material at the surface of the frog's taste organ. We employed morphological and histochemical techniques using both the light microscope and the electron microscope. Results show that the apical, external aspect of cells reaching the surface of the taste organ is in close contact with a layer of amorphous material. The histochemical characteristics of this material vary according to the cell type with which it is in contact. Three different microenvironments can be identified at the surface of the frog's taste organ: type 1 microenvironment is associated with the superficial layer of mucus (secretory) cells; type 2 microenvironment characterizes the surface of the so‐called wing cells, which reach the surface of the taste organ as thin laminae running among mucus cells; and type 3 microenvironment shrouds the free endings of putative taste cells and is rich in calcium and lipids. Type 2 and type 3 microenvironments fix peroxidase (a sapid macromolecule) with increasing affinity. We conclude that highly differentiated microenvironments exist at the surface of the frog's taste organ, and these could play a role in the chain of biological events leading to the taste sensation. Furthermore, characterization of the cellassociated, specific microenvironments can help clarify the role of the different cell types in the frog's taste organ.
Neural organization of spindles in three hindlimb muscles of the rat
Authors: Kucera Jan , Walro Jon M. , Reichler Judith 
Published: February 2005

AbstractThe neuroanatomical organization of the dynamic (bag1) and static (bag2 and chain) intrafusal systems was compared by light and electron microscopy of serial sections among 71 poles of muscle spindle in soleus (SOL), extensor digitorum longus (EDL), and lumbrical (LUM) muscles in the rat. Eighty‐four percent of 195 fusi‐motor (γ) axons to the spindles innervated either the dynamic bag1 fiber or the static bag2 and/or chain fibers. Sixteen percent of the γ axons coin‐nervated the dynamic and static intrafusal fibers. Some of these nonselective axons were branches of efferents that also gave rise to axons selective to either the dynamic or static types of intrafusal fibers in one or more spindles. Thus activation of individual stem γ efferents might not have a purely dynamic or purely static effect on the integrated afferent outflow from spindles of a hind‐limb muscle in the rat. In addition, primary afferents in all muscles had terminations that cross‐innervated the dynamic bag1 and static bag2 and/or chain intrafusal fibers in individual spindles, an arrangement that may enhance the mixed dynamic/static behavior of afferents when different intrafusal fibers are activated concurrently. Spindles of the slow SOL and fast EDL muscles had similar features, whereas differences were observed in the organization of the proximal (SOL and EDL) and distal (LUM) muscles. Spindles in LUM muscles had fewer static intrafusal fibers, a higher ratio of dynamic to static γ axons, and a higher incidence of skeletofusimotor (β) innervation to intrafusal fibers than spindles in the SOL or EDL muscles. Thus, the relative contribution of dynamic and static systems to muscle afferent outflow may differ among spindles located in different segments of the rat hindlimb. However, the dynamic and static intrafusal systems of spindle were less sharply demarcated in each of the three hindlimb rat muscles than in the cat tenuissimus muscle.
Inflammatory macrophages in the dog contain high amounts of intravesicular ferritin and are associated with pouches of connective tissue fibers
Authors: Águas Artur P. , Grande Nuno Rodrigues , Carvalho Emanuel 
Published: February 2005

AbstractWe have studied the subcellular distribution of ferritin in inflammatory macrophages present in regional lymph nodes from dogs subjected to a pulmonary inflammatory reaction. The inflammatory reaction was induced by intrabronchial instillation of calcium tungstate (CaWO4), a water‐insoluble powder. Ferritin was identified by electron microscopy, and its electron density was enhanced by the use of a modified Perls method. From day 14 on after the CaWO4deposition, tungsten‐positive lymph node macrophages showed a massive accumulation of ferritin. Most of the ferritin was stored in membrane‐bounded vesicles that showed heterogeneous concentrations of the protein. A significant complement of ferritin was also detected in the cytoplasmic ground substance of phagocytes. The cell surface of the ferritin‐rich, tungsten‐positive macrophages showed deep infoldings that encompassed small pockets of connective tissue fibers. These features were not observed in control samples or in lymph nodes from dogs subjected to CaWO4‐induced inflammation for periods shorter than 1 week. Our data indicate that inflammatory macrophages greatly increase their content of ferritin and that ferritin is stored predominantly by a membrane‐bounded vesicular compartment. This is in contrast with suggestions that the inflammation‐induced increase in macrophage iron is restricted to the labile pool of iron and it does not involve the iron bound to ferritin molecules. Our observation of nodules of connective‐tissue fibers in intimate topographical association with ferritin‐rich macrophages may indicate that the increase in intracellular ferritin in the macrophage is in some way related to the secretion of factors by the phagocyte that will stimulate fibrillogenesis by neighboring fibroblasts.
Developing nephrons in adolescent dogfish, Scyliorhinus caniculus (L.), with reference to ultrastructure of early stages, histogenesis of the renal countercurrent system, and nephron segmentation in marine elasmobranchs
Authors: Hentschel Hartmut 
Published: February 2005

AbstractLight and electron microscopy of the excretory kidney of adolescent dogfish, Scyliorhinus caniculus (L.), revealed immature and mature nephrons as well as four developmental stages of nephrons. At stage I the nephron was characterized by a condensed mass of mesenchymal cells in the center of several concentric layers of connective tissue. At stage II of the nephron, the S‐shaped body was an elongate cyst with a high prismatic epithelium that was connected by a developing collecting tubule with the collecting duct system. At stage III, the developing nephrons already possess the essential features of the mature nephron but lack complete differentiation. Developing renal corpuscles had one afferent arteriole and two efferent vessels. Developing tubules ran four times between the lateral bundle zone and the mesial tissue zone before they joined the collecting duct system. A continuous sheath of flat cells, encompassing the collecting duct system, extended around the developing lateral bundle. A rudimentary central vessel ran from the developing lateral bundle to the venous sinusoid capillaries between the mesial convolutions. Developmental stage IV was similar to the mature nephron, however, renal corpuscles and tubular segments were smaller than those of mature nephrons.Conclusive evidence for morphological homology of elasmobranch nephron segments and collecting tubule‐collecting duct system with those of other vertebrates is provided. The origin and nature of the central vessel and the bundle sheath is clarified. These specific structures of marine elasmobranch kidney supposedly are of great functional relevance for the renal countercurrent system that in turn is essential for ion‐ and osmoregulation.
Regional differences in the morphology of the goat epididymis: A light microscopic and ultrastructural study
Authors: Goyal Hari Om , Williams Carol S. 
Published: February 2005

AbstractThe goat epididymis, based on morphological differences, was divided into five regions; regions I and II, and the proximal part of region III constituted the head; the distal part of region III and region IV, the body; and region V, the tail. The epithelium of all regions contained principal and basal epithelial cells and intraepithelial lymphocytes and macrophages. In addition, regions II to IV also contained a few apical cells. Clear cells were absent.The epithelium varied in height from the tallest in region I (88 ± 33 μm) to the shortest in region V (38 ± 5 μm). Conversely, the luminal diameter, thickness of smooth muscle wall, and luminal sperm concentration were highest in region V. The irregular epithelial height of regions I and IV accounted for a stellate lumen in contrast to the oval lumen of the other regions. Whereas the lumen of region I contained only a few sperm, those of regions II, III, and IV were filled with sperm.Principal cells were the only cell type that showed striking cytological differences between regions. While they contained absorptive features (canaliculi, pinocytotic and coated vesicles, and subapical vacuoles) in all regions, the principal cells of region II were filled with large, heterogeneous vacuoles (up to 5 μm in diameter), suggesting that they may be preferentially involved in transporting and digesting particulate material. Besides absorptive features, principal cells of all regions contained morphological correlates of protein synthesis such as highly developed Golgi complexes in the supranuclear area and numerous cisternae of RER near the Golgi body and in the infranuclear cytoplasm. The cisternae of RER were more developed in region IV, and in some instances, they were distended with flocculent material resembling newly synthesized protein. Unlike the protein synthesizing organelles, principal cells of all regions lacked morphological correlates of steroid hormone synthesis.These results are compared with previously published data on the regional differences in the epididymis of other species, especially with those of the rat and the bull, in an effort to understand the significance of the epididymis in sperm maturation.
Connexin 43 expression in the mouse embryo: Localization of transcripts within developmentally significant domains
Authors: Ruangvoravat Christine P. , Lo Cecilia W. 
Published: February 2005

AbstractThe expression of the gap junction gene, Cx43, during mouse embryogenesis was characterized by an in situ hybridization analysis of mouse embryos from gestation days 4.5 to 12.5. This analysis revealed that Cx43 transcripts are differentially expressed as a function of development beginning at the blastocyst stage. In many regions of the embryo, Cx43 transcripts were found in discrete spatially restricted domains. This was observed in conjunction with the development of the brain, neural tube, prevertebra, limb, and various aspects of organogenesis. In some cases, the differential localization of Cx43 transcripts is associated with developmental processes mediated by inductive interactions, such as that of the eye, otic vesicle, kidney, and the branchial arches. In addition, in the 10.5 day embryo, Cx43 transcripts appear to be distributed as a gradient in regions spanning the midbrain/hindbrain junction, in the telencephalon, and in the limb mesenchyme. Surprisingly, our results also suggest that neural crest and sclerotomal cells, i.e., cells that are presumably migratory, express high levels of Cx43 transcripts. Overall, these results suggest that gap junctions encoded by Cx43 may play a role in various aspects of mouse development, possibly including relaying second messengers emanating from signal transduction pathways that mediate inductive interactions. © 1992 Wiley‐Liss, Inc.
Regulation of anterior cell‐specific mec‐3 expression during asymmetric cell division in C. elegans
Authors: Way Jeffrey C. , Run Jin‐Quan , Wang Alice Y. 
Published: February 2005

AbstractThe homeobox‐containing mec‐3 gene of C. elegans is expressed in 10 mechanosensory neurons and is necessary for these cells to acquire their fate. All the mec‐3‐expressing cells are anterior daughters from an asymmetric cell division. In this paper, we examine the expression of a mec‐3–lacZ fusion in the presence of mutations that may disrupt asymmetric cell division or anterior‐posterior positional information, as well as mutations that may specifically alter mec‐3 expression. A mutation in lin‐17 causes production of additional mec‐3‐expressing cells and can have its effect on the cell division that produces a mec‐3‐expressing cell. In a lin‐5 mutant, in which postembryonic blast cells do not complete cell division and become polyploid, blast cells that would give rise to mec‐3‐expressing daughters instead express mec‐3 themselves. In a lin‐12 glp‐1 double mutant, which is disrupted for many cell interactions in which two cells compete for the same fate, mec‐3 expression is unaffected. These results are consistent with a model for asymmetric cell division in which the mec‐3‐expressing cell and its sister are different immediately upon cell division, rather than acquiring differences through later interaction with each other or their surroundings. lin‐17 mutant animals also show defects in the position of the PVM cell and the PLM axons. Animals mutant in unc‐73 and unc‐40, known to have axon outgrowth defects, also show errors in PVM position and a low frequency of additional mec‐3‐expressing cells, as well as occasional secondary vulval protrusions, a common phenotype of lin‐17 animals. Many other mutations have either no effect on mec‐3 expression or an effect that can be largely predicted from previously known phenotypes: these include mab‐5, mig‐1, unc‐53, egl‐5, lin‐32, and egl‐27. unc‐11 shows an unexpected and specific defect in mec‐3 expression in the PVD neurons, but not in the other mec‐3‐expressing cells. Two mutations that suppress the egg‐laying defect of unc‐86 have no effect on the mec‐3 expression defect in an unc‐86 mutant. © 1992 Wiley‐Liss, Inc.
Expression of collagenase and IL‐1α in developing rat hearts
Authors: Nakagawa Masao , Terracio Louis , Carver Wayne , Birkedal‐Hansen H. , Borg Thomas K. 
Published: February 2005

AbstractDuring development, extracellular matrix (ECM) molecules are thought to play a major role in regulating the formation of the heart. The change in the heart from a simple tube to a complex, four‐chambered organ requires the modification of both the cellular components as well as the surrounding ECM. Matrix metalloproteinases (MMP), which include collagenases, are enzymes present in the ECM that have the potential to modify the existing ECM during the development of the heart. Using both monoclonal and polyclonal antisera against collagenase, specific temporal and spatial patterns have been documented during critial periods of heart development. The cytokine interleukin 1α (IL‐1α), a potent inducer of the MMP expression, was also shown to have a similar staining pattern in the developing heart.The monoclonal anti‐rat collagenase (Mab) intensely stained the surfaces of the myocytes in the trabeculae and the ventricular and atrial walls of the 11.5 or 12.5 embryonic day (ED) rat hearts. In contrast, the polyclonal anti‐human collagenase (Pab) stained not only the cardiomyocytes but also the hypertrophic endocardial cells. Pab appeared to stain the leading edge of the mesenchymal cells that migrate into the cardiac jelly of the 11.5 or 12.5 ED hearts. Immunohistochemical staining showed IL‐1α on the endocardial endothelium and the surface of cardiomyocytes near the cardiac jelly just before or coincident with the appearance of migrating cells.IL‐1α was detected on the endocardial endothelium, cardiomyocytes in the trabeculae, and the ventricular and atrial walls, as well as in the myocardial basement membrane of the truncal or atrioventricular region. However, no staining could be detected on the migrating cells in the cardiac cushions. These results indicate the presence of collagenase and IL‐1α on the surface of cardiomyocytes and mesenchymal cells at times when the heart is undergoing acute remodeling during septation and trabeculation. These data suggest a role for collagenase/cytokine interaction in tissue remodeling during critical stages of cardiac embryogenesis where modification of the ECM is essential to cardiac morphogenesis. © 1992 Wiley Liss, Inc.
Fibrillin delineates the primary axis of the early avian embryo
Authors: Gallagher Betty C. , Sakai Lynn Y. , Little Charles D. 
Published: February 2005

AbstractChicken embryos were immunolabeled with antibodies to fibrillin, an extracelular matrix molecule implicated in the Marfan syndrome. The pattern of labeling, established using both whole‐mounted and sectioned embryos, showed a striking localization at the primary axis of the early embryo, including Hensen's node. After stage 8, the labeling of Hensen's node diminished while other structures in the embryo exhibited increased immunolabeling. These structures include the region of the presumptive dorsal aorta, the ventral surface of the notochord, and the mesocardium. Injections of the antibody between the vitelline membrane and the blastoderm in vivo failed to perturb the development of embryos, thus precluding any conclusions regarding the function of fibrillin. © 1993 wiley‐Liss, Inc.
gli, a zinc finger transcription factor and oncogene, is expressed during normal mouse development
Authors: Walterhouse David , Ahmed Maqbool , Slusarski Diane , Kalamaras Julie , Boucher Diane , Holmgren Robert , Iannaccone Philip 
Published: February 2005

AbstractThe oncogene GLI is amplified and expressed in some cases of human malignant glioma and undifferentiated childhood sarcoma a and is the prototype for a gene family characterized by a highly conserved set of five tandem zinc fingers and a consensus cysteine‐histidine link. This zinc finger motif has been shown to bind DNA with sequence specificity and may mediate transcriptional regulation. Since GLI is expressed in embryonal carcinoma cell lines but not in most normal adult tissues and shows significant sequence similarity within its zinc finger domain to cubitus interruptus dominant (ciD), a Drosophila segmentation gene known to be important in the morphogenesis of the posterior portion of each larval segment, we established the temporal and tissue expression patterns of the mouse homologue of human GLI in day 10 through 18 mouse embryos with Northern blotting, reverse transcriptase coupled PCR, and in situ hybridization. gli transcripts were demonstrated on days 10 through 18 of mouse embryonic development as well as in normal adult uterus, brain, testis, and limb. Tissue expression of gli during gestation was demonstrated in Meckel's precartilage mesenchyme, the basis occipitus, rib mesenchymal condensations, primordial vertebral bodies, digital mesenchymal condensations in forefoot and hindfoot plates, the ependymal layer of the spnal cord, and the mesoderm of the gastrointestinal tract. Expression persisted throughout gestation in developing bone and cartilage of the extremities, the ribs, and the vertebral bodies, as well as the gastrointestinal tract mesoderm. These findings support a role for gli family genes in normal craniofacial and digital development in mammals first suggested by the demonstration of translocation breakpoints within the GLI3 gene in families with the Greig cephalopolysyndactyly syndrome and subsequently by reduced gli3 expression in the mouse mutant extra toes. It is surprising that a single gene would be expressed in such a wide range of mesenchymal structures. © 1993 wiley‐Liss, Inc.
Analysis of LacZ reporter genes in transgenic embryos suggests the presence of several cis‐acting regulatory elements in the murine Hoxb‐6 gene
Authors: Eid Roland , Koseki Haruhiko , Schughart Klaus 
Published: February 2005

AbstractHomeobox genes are expressed in stage‐, region‐, and tissue‐specific patterns during embryonic development of the mouse. In order to understand the underlying regulatory mechanisms the murine homeobox gene Hoxb‐6 was analyzed for the presence of cis‐acting regulatory elements. Transgenic mouse embryos and lines were generated which contained the LacZ reporter gene under the control of different fragments from the Hoxb‐6 gene. In total, 13.2 kb of genomic DNA covering the entire Hoxb‐6 region were analyzed. Our results suggested the presence of three regulatory regions in the Hoxb‐6 gene: a limb/LPM element which directed gene expression into restricted regions of the developing limb buds and the ventro‐lateral and visceral mesenchyme, a regulatory element required for gene expression into ventral regions of the developing spinal cord, and a third element necessary for directing gene expression into developing mesonephric tubules and mesonephric ducts. We demonstrated that the limb/LPM element functions as an enhancer in a promoter‐ and orientiation‐independent manner. The comparison of the expression patterns of the reporter gene constructs and the endogenous Hoxb‐6 gene revealed that the regulatory regions were able to reproduce part of the Hoxb‐6 pattern. However, not all control elements necessary to completely mimic the endogenous Hoxb‐6 expression pattern could be detected, although the entire Hoxb‐6 genomic region has been analyzed. These observations suggest that for some aspects of Hoxb‐6 gene regulation the integrity of large genomic regions of the Hoxb cluster is required. © 1993 wiley‐Liss, Inc.