bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrastructural and cytoarchitectural features of lymphoreticular organs in the colon and rectum of adult BALB/c mice
Authors: Owen Robert L. , Piazza Anthony J. , Ermak Thomas H. 
Published: February 2005

AbstractThe structure and function of colonic mucosal lymphoid organs remain largely unexplored, especially in the rectum hidden within the pelvic vault. Two‐month‐old female BALB/c mice were anesthetized, and the entire colon was removed from cecum to anus. Distal colonic patches were then prepared for electron microscopy or were quick‐frozen and sectioned for immunoperoxidase localization of B cells and T cell subsets. Aggregated lymphoid follicles were distributed irregularly along the entire colon with an average of 1.4 patches per centimeter of colon length. There were large collections of follicles opposite the ileocecal valve (cecal patches), variable numbers of patches throughout the colon, and at least one patch within 10 mm of the anus (rectal patch). Follicles were adjacent to branching crypts lined by epithelium infiltrated by lymphoid cells and containing few goblet cells. In electron micrographs, M cells were identified by their short, irregular microvilli; intraepithelial lymphoid cells; reduced lysosomal dense bodies; and an expanded tubulovesicular network. Small germinal centers were seen. Cytoarchitectural components of colonic lymphoid follicles and Peyer's patch follicles were remarkably similar, despite differences in surrounding mucosa and luminal microbial exposure. The presence of organized lymphoid tissue with M cells and germinal centers suggests that transepithelial particle transport and antigen recognition can take place in the rectum. Whether such tissue has the capacity for uptake of luminal microorganisms is of particular interest, not only because colonic follicles may be sites for local initiation of immune responses but also because they may be important entry points for systemic infection.
Subcellular distribution of [3H]‐dexamethasone mesylate binding sites in leydig cells using electron microscope radioautography
Authors: Stalker Alison , Hermo Louis , Antakly Tony 
Published: February 2005

AbstractThe present view is that glucocorticoid hormones bind to their cytoplasmic receptors before reaching their nuclear target sites, which include specific DNA sequences. Although it is believed that cytoplasmic sequestration of steroid receptors and other transcription factors (such as NFKB) may regulate the overall activity of these factors, there is little information on the exact subcellular sites of steroid receptors or even of any other transcription factors. Tritiated (3H)‐dexamethasone 21‐mesylate (DM) is an affinity label that binds covalently to the glucocorticoid receptor (GR), thereby allowing morphological localization of the receptor at the light and electron microscope levels as well as for quantitative radioautographic (RAG) analysis. After injection of 3H‐DM into the testis, a specific radioautographic signal was observed in Leydig cells, which correlated with a high level of immunocytochemically demonstrable GR in these cells at the light‐microscope level. To localize the 3H‐DM binding sites at the electron microscope (EM) level, the testes of 5 experimental and 3 control adrenalectomized rats were injected directly with 20 μCi 3H‐DM; control rats received simultaneously a 25‐fold excess of unlabeled dexamethasone; 15 min later, rats were fixed with glutaraldehyde and the tissue was processed for EM RAG analysis combined with quantitative morphometry. The radioautographs showed that the cytosol, nucleus, smooth endoplasmic reticulum (sER), and mitochondria were labeled. Since the cytosol was always adjacent to tubules of the sER, the term sER‐rich cytosol was used to represent label over sER networks, which may also represent cytosol labeling due to the limited resolution of the radioautographic technique. Labeling was highest in sER‐rich cytosol and mitochondria, at 53% and 31% of the total, respectively. Cytosol (exclusively of all organelles) and nucleus showed comparatively weak labeling, at 9% and 7%, respectively. This study thus clearly establishes with the electron microscope, the localization of glucocorticoid binding sites using DM. It remains to be determined whether or not these DM binding sites represent bona fide glucocorticoid receptors or nonreceptor proteins that bind DM. Whereas the functional significance of the subcellular distribution of DM is not known, the labeling of the cytosol may represent localization of the steroid and GR in their traditional compartment. The steroid antagonistic properties of DM may have prevented the DM‐GR complexes from translocating to the nucleus. However, the significant labeling of the sER‐rich cytosol and mitochondria was unexpected and raises intriguing questions that are being addressed in current studies.
Calcitonin gene‐related peptide‐immunoreactive nerves in the rat kidney
Authors: Knight D. S. , Cicero S. , Beal J. A. 
Published: February 2005

AbstractCryostat‐ and vibratome‐cut rat kidney secretions were singly or doubly labeled to visualize immunoreactive calcitonin‐gene‐related peptide (CGRPI) and substance P (SPI). Rats were perfused with 2–4% paraformaldehyde + 0.15% picric acid then rinsed with buffer. Horseradish peroxidase (HRP) was used to visualize CGRP in vibratome sections, and combined HRP and fluorophore were used to visualize the two peptides simultaneously in cryostat sections. There is a complex, multilayered plexus of CGRP nerves on the renal pelvis and a less dense, single‐layered plexus on the major branches of the renal artery and on interlobar arteries and veins. A few axons innervate finer branches of the arterial tree and other intrarenal structures. Results of double immunolabeling suggest that SPI axons comprise a subpopulation of the CGRP axon population in the rat kidney. There was no evidence for a separate population of SPI axons.
Parent‐specific expression of a human keratin 18/β‐galactosidase fusion gene in transgenic mice
Authors: Thorey Irmgard S. , Pedersen Roger A. , Linney Elwood , Oshima Robert G. 
Published: February 2005

AbstractInsertion of a human keratin 18 (K18)‐bacterial β‐galactosidase (LacZ) fusion gene into mice has led to a unique transgenic line in which expression of the transgene is subject to unusual germ line‐specific, genomic imprinting effects. Fetal expression of the LacZ reporter gene depends on the gender of the transmitting parent, with appropriate expression in liver after maternal inheritance, and ectopic expression in retina and mesodermal tissues after paternal inheritance. This tissue‐specific imprinting pattern is superimposed upon a basic expression pattern which is unaffected by parental inheritance. Insertion of the transgene has led to a recessive‐lethal phenotype, with no parent‐of‐origin effects on viability, suggesting that the transgene has not inserted into an imprinted region of the genome. HpaII and HhaI methylation sensitive restriction sites within the bacterial LacZ reporter gene are completely methylated when activity of the maternally inherited transgene is detected in the fetal liver, and not methylated when the paternally inherited transgene is silent. Thus DNA methylation of LacZ is correlated with maternal inheritance and may be implicated in the genomic imprinting mechanism as others have suggested. However, in contrast to the commonly found correlation of expression and low DNA methylation, the LacZ gene was expressed in fetal liver when fully methylated. This result may imply the existence of negative regulatory activities that recognize the unmethylated LacZ gene. © 1992 Wiley‐Liss, Inc.
Connexin expression and gap junction communication compartments in the developing mouse limb
Authors: Laird Dale W. , Yancey S. Barbara , Bugga Lakshmi , Revel Jean‐Paul 
Published: February 2005

AbstractFundamental to the understanding of mouse limb morphogenesis and pattern formation is the need to elucidate the spatial and temporal distribution of gap junction proteins (connexins, Cx) and cell‐cell communication compartments. To this end, we used immunofluorescence and confocal microscopy together with 3‐dimensional reconstruction software to map the distribution of Cx43 and Cx32 in 11–14.5 days postcoitum (dpc) mouse limbs. Cx43 was strictly localized to the apical ectodermal ridge (AER) and non‐ridge ectoderm throughout all stages of mouse limb development studied. Cx32, on the other hand, was abundant in the mesenchyme with only low levels of expression in the 11–13.5 dpc ectoderm. However, at 14–14.5 dpc there was a clear increase in Cx32 expression in the ectoderm. Double labeling for connexins and confocal microscopy revealed Cx43 and Cx32 in the same optical section of the basal cells of the ectoderm but in separate plaques. Lucifer yellow dye injections showed that the cells of the AER were in direct communication with the nonridge ectoderm but dye was never observed to spread to the mesenchyme. Cells of the mesenchyme were coupled to each other but to a much lesser extent than cells of the ectoderm. Finally, although there was an increase in Cx32 expression in the ectoderm at 14–14.5 dpc, this was not correlated with any detectable change in communication compartments. Thus, the lack of dye transfer between the ectoderm and underlying mesenchyme from the peak of AER height through its decline suggests that bulk transfer of morphogens between these two layers is not necessary for mouse limb development. © 1993 Wiley‐Liss, Inc.
Xenopus gastrulation without a blastocoel roof
Authors: Keller Ray , Jansa Sharon 
Published: February 2005

AbstractThe objective of this paper is to determine the function in gastrulation of several of the five major regional morphogenetic processes in the African clawed frog, Xenopus laevis. These regional processes are (1) epiboly of the animal cap (AC); (2) migration of the mesoderm on the roof of the blastocoel; (3) convergence and extension of the dorsal, noninvoluting marginal zone (NIMZ); (4) formation of the bottle cells at the site of blastopore formation; and (5) convergence and extension of the involuting marginal zone (IMZ). After the AC and the NIMZ were removed, thus eliminating the first three of these processes, the IMZ involuted, constricted, and closed the blastopore. It also converged and extended to form notochord and somites, although these tissues were often crooked and sank into or were covered over by the vegetal endoderm. When the AC was removed, the dorsal axial mesoderm involuted and stuck to the inner surface of the NIMZ. The IMZ and NIMZ converged and extended together to form a longer, straighter axis than that formed by the IMZ alone. Moreover, presence of the NIMZ also prevented the sinking of the IMZ into the endoderm. Misalignment of the available AC‐NIMZ substratum and the IMZ at the beginning of gastrulation suggested that the IMZ determines the general direction of its own extension. Absence of the AC‐NIMZ accelerated and increased the normal effects of bottle cell formation on the IMZ and vegetal endoderm. In absence of the AC‐NIMZ as a substratum on which to migrate, prechordal mesoderm was pushed anteriorly by the converging and extending mesoderm behind it, but it did not spread normally. We conclude that (1) involution and blastopore closure by the IMZ can occur without pushing by epiboly and convergence and extension of the NIMZ‐AC; (2) involution and blastopore closure can occur without migration of the mesoderm on the blastocoel roof; (3) convergence and extension of the IMZ are sufficient to bring about IMZ involution and blastopore closure; (4) the function of bottle cells in initiating involution is retarded by presence of the NIMZ‐AC; (5) the associated dorsal NIMZ and IMZ together form an axis that extends better and is perhaps stiffer than the IMZ alone; and (6) the dorsal axial and paraxial mesoderm form the “skeleton” around which the mechanics of the other parts of the embryo are organized. These findings are important for the analysis of gastrulation by cellular, genetic, and molecular approaches. © 1993 Wiley‐Liss, Inc.
Neurofibromin, a predominantly neuronal GTPase activating protein in the adult, is ubiquitously expressed during development
Authors: Daston Maryellen Maneri , Ratner Nancy 
Published: February 2005

AbstractThe onset of manifestations of the common, autosomal dominantly inherited disease type 1 neurofibromatosis (NF1) is usually in childhood. To begin to understand the pathogenesis of NF1, we analyzed the developmental pattern of expression of the protein product of the NF1 gene, neurofibromin, by Western blotting and immunohistochemistry using the rat as a model system. Neurofibromin is uniformly distributed throughout embyronic day 10 and 12 rat embryos. By embryonic day 16, neurofibromin immunore‐activity is enriched in neurons of the cortical plate, in peripheral ganglia, and in developing CNS and PNS fiber tracts, but remains detectable outside the nervous system. Expression decreases in nonneural tissues by postnatal day 6, and neurofibromin is greatly decreased (lung, adrenal cortex, skin) or absent (skeletal muscle, cartilage) in adult tissues except for brain, spinal cord, peripheral nerve, and adrenal medulla. Transient expression of neurofibromin during development in many tissues suggests the importance of this GTPase‐activating protein in morphogenesis and organ growth. A separate role is proposed for neurofibromin in growing axons and in the mature nervous system. © 1993 Wiley‐Liss, Inc.
Tissue‐specific expression of type XII collagen during mouse embryonic development
Authors: Oh Suk Paul , May Griffith C. , Hay Elizabeth D. , Olsen Bjorn R. 
Published: February 2005

AbstractPolyclonal antibodies were raised in rabbits against a fusion peptide representing a portion of the amino‐terminal non‐triplehelical domain of mouse type XII collagen. The antibodies reacted with bands of 220 and 350 kDa on Western blots of mouse tissue extracts. Immunohistochemical analyses of mouse embryos demonstrated that type XII collagen is expressed mainly in dense connective tissues of tendons, ligaments, dermis, cornea, blood vessel walls, meninges, and developing membranous bones. Comparison of skin extracts and medium of cultured mouse skin fibroblasts by Western blotting showed that while tissues contain short 220 kDa type XII collagen polypeptides as well as the long form, cultured cells produce mainly the long form with 350 kDa polypeptides. © 1993 wiley‐Liss, Inc.
Early heart development: Dynamics of endocardial cell sorting suggests a common origin with cardiomyocytes
Authors: Linask Kersti K. , Lash James W. 
Published: February 2005

AbstractThe myocardial and endocardial cell sorting out processes take place primarily between 19 and 29 hr of development in the avian embryo. This occurs in an apparent rostral to caudal wave through the heart forming region. During heart development considerable uncertainty exists regarding the processes that regulate cell commitments, progressive aggregation, and sorting out of the different precardiac cell populations. The question addressed in this report is whether endocardial and myocardial cells have a common origin or do the endocardial cells arise from a distinct population of cells from within the precardiac mesoderm. These cells then migrate to become localized between the developing myocardium above and the endoderm below. The distribution of preendocardial cells and premyocardial cells has been followed immunohistochemically in quail heart‐forming region mesoderm explants from embryos approximately 18 hr in development and incubated for a 24‐hr period. Differentiating myocardiocytes were immunostained with anti‐N‐cadherin and endocardiocytes with QH‐1, a monoclonal antibody that recognizes an antigenic determinant on quail endothelial cells. Sparsely localized QH‐1 labeled endothelial cells are localized in the stage 5 heart‐forming region. These cells are often arranged in a columnar fashion in the mesoderm explants 6 hr after explantation. By 15–22 hr large patches of QH‐1 expressing cells are interspersed with the N‐cadherin expressing myocardiocytes. A subpopulation of cells express both N‐cadherin and QH‐1 antigen suggesting that endocardial and myocardial cells may arise from a common precursor population and that N‐cadherin regulation may be a mechanism underlying specific cell sorting of these two cell populations during heart development. © 1993 wiley‐Liss, Inc.
Perlecan gene expression precedes laminin gene expression during differentiation of F9 embryonal carcinoma cells
Authors: Chakravarti Shukti , Hassell John R. , Phillips Stephen L. 
Published: February 2005

AbstractF9 embryonal cells can be induced to differentiate and synthesize basement membrane proteins. Perlecan and laminin are two basement membrane constituents that have extensive regions of homology. Expression of perlecan and laminin B1 genes was followed during differentiation of F9 cells by measurements of transcription rate and mRNA abundance using nuclear run on assays and Northern hybridizations, respectively. The rate of precursor protein synthesis was determined by immunoprecipitation from lysates of pulse‐labeled F9 cells. The results showed that perlecan gene expression responds more rapidly after induction than does laminin B1 gene expression but is ultimately expressed at a substantially lower level than laminin. Thus, the perlecan and laminin genes appear to be regulated by different mechanisms and their gene products are not made in stoichiometric amounts. © 1993 Wiley‐Liss, Inc.
Expression of homeobox genes Msx‐1 (Hox‐7) and Msx‐2 (Hox‐8) during cardiac development in the chick
Authors: Chan‐Thomas Penny S. , Thompson Robert P. , Robert Benoît , Yacoub Magdi H. , Barton Paul J. R. 
Published: February 2005

AbstractThe vertebrate homeobox genes Msx‐1 and Msx‐2 are related to the Drosophila mshgene and are expressed in a variety of tissues during embryogenesis. We have examined their expression by in situ hybridisation during critical stages of cardiac development in the chick from stages 15 + to 37. Msx‐1 expression is apparent in a number of non‐myocardial cell populations, including cells undergoing an epithelial to mesenchymal transformation in the atrioventricular and the outflow tract regions that play an integral role in heart septation and valve formation. Msx.2 expression is restricted to a distinct subpopulation of myocardial cells that, in later stages, coincides morphologically with the cardiac conduction system. The timing of Msx‐2 expression suggests that it plays a role in conduction system tissue formation and that it identifies precursor cells of this specialised myocardium. The pattern of Msx‐2 expression is discussed with reference to current models of conduction tissue development. © 1993 Wiley‐Liss, Inc.
Structural abnormalities associated with congenital megacolon in transgenic mice that overexpress the Hoxa‐4 gene
Authors: Tennyson Virginia M. , Gershon Michael D. , Sherman Diane L. , Behringer Richard R. , Raz Regina , Crotty David A. , Wolgemuth Debra J. 
Published: February 2005

AbstractCongenital megacolon develops in transgenic mice that overexpress the homeobox‐containing gene, Hoxa‐4. The current study was done to identify abnormlities of the terminal colon that might account for the phenotype. The terminal bowel of transgenic mice was compared with that of control and lethal spotted (ls/ls) mice, a strain in which megacolon also develops. The terminal colon of the transgenic mice contained fewer ganglia than that of controls, but was hypoganglionic, rather than aganglionic like that of ls/ls mice. The neurons present in the adult transgenic colon were sifnificantly increased in size and a subset of very large neurons(>40 μm in maximum diameter) were observed. Electron microscopic studies of young adult transgenic mice revealed that the ganglia and nerves of the myenteric plexus had the ultrastructure of extraenteric peripheral nerve rather than that of the enteric nervous system (ENS). The myenteric ganglia in the transgenic animals contained Schwann cells associated with a basal lamina that enveloped axons completely and individually, instead of glia. Although collagen is excluded from the ganglia and thin nerve fibers of the normal ENS, a collagen‐containing endoneurium surrounded each of the axon‐Schwann cell units of the abnormal nerve fibers of the transgenic mice were located in these nerve bundles rather than in ganglia. There were smooth muscle abnormalities in the terminal bowel of the transgenic mice. Wide gaps were present in the longitudinal muscle of the transgenic mice; these gaps contained ganglia that were in contact with the adventitia. These longitudinal smooth muscle cells were more irregular than those of controls and they contained fewer puncta adherens; moreover, a larger proportion of the volume of the cytoplasm of transgenic smooth muscle cells was occupied by organelles. Finally, an extensive thickening and reduplication of the basal lamina surrounding the smooth muscle cells of the muscularis mucosa was observed in the transgenic colon and resembled that found in ls/ls mice. These data suggest that both smooth muscle and the innervation of the terminal bowel of neonatal Hoxa‐4 transgenic mice are structurally abnormal. Although some of the abnormalities seen in Hoxa‐4 transgenic mice are similar to those which arise in ls/ls mice, the two conditions are not identical. In both animals, the data are consistent with the hypothesis that the defects arise as a result of a defective interaction between the precursors of enteric neurons and smooth muscle. © 1993 Wiley‐Liss, Inc.
Tenascin is associated with articular cartilage development
Authors: Pacifici Maurizio , Iwamoto Masahiro , Golden Eleanor B. , Leatherman Judith L. , Lee Yun‐Shain , Chuong Cheng‐Ming 
Published: February 2005

AbstractThe roles of tenascin in cartilage development and function remain unclear. Based on the observation that tenascin is particularly abundant at the epiphyseal extremities of developing cartilaginous models of long bones in chick and mouse embryo, we tested the hypothesis that tenascin is involved in articular cartilage development. Immunofluorescence analysis revealed that tenascin was first localized in the cell condensation region of Day 4 chick embryo limb buds, where the cartilaginous models form. With further development, tenascin gene expression became indeed restricted to the articular cap of the models. Tenascin persisted in the articular cartilage of postnatal chickens but appeared to decrease with age. The protein was also abundant in embryonic and adult tracheal cartilage rings which, like articular cartilage, persist throughout postnatal life. Similar patterns of tenascin expression were seen in mouse. Using monoclonal antibodies to avian tenascin variants, we found that the bulk of articular cartilage contained the shortest tenascin variant (Tn190), whereas the largest variant (Tn230) was present in tissues associated or interacting with articular cartilage (ligaments and meniscus). The protein and its mRNA, however, were undetectable in growth plate cartilage undergoing maturation and endochondral ossification. This inverse correlation between chondrocyte maturation and tenascin production was corroborated by the finding that tenascin gene expression decreased markedly during maturation of a secondary ossification center within the articular cap in vivo. Thus, tenascin is intimately associated with the development of articular cartilage and other permanent cartilages whereas absence or reduced amounts of this matrix protein characterize transisent cartilages which undergo maturation and are replaced by bone. © 1993 Wiley‐Liss, Inc.