bluuebunny/crossref_metadata_2025_split huggingface dataset:
An investigation of lymphatic vessels in the feline dental pulp
Authors: Bishop M. A. , Malhotra M. 
Published: February 2005

AbstractThe existence of lymphatic vessels in the dental pulp has been a matter of continuing controversy. We have now used light microscopy to examine semithin transverse sections of perfusion‐fixed incisors and canines in cats. Lymphatics were found in all the teeth studies. In most teeth they were present in the coronal, middlel, and apical regions of the pulp; but in a few they were lacking coronally and in the middle. Within individual teeth, lymphatics were found in the subodontoblastic zone or more centrally in the pulp; but none were found in the odontoblast layer or in the pulp horns.Vessels located by light microscopy were subsequently examined by transmission electron microscopy. Their ultrastructural features were typical of lymphatics and included irregular, attenuated endothelium with adjacent cells joined in different ways. Occasional gaps connected the extracellular spaces with their lumens, and abluminal endothelial projections appeared to form open and bulbs. There was very little basement membrane, but anchoring filaments were found near the abluminal surface of the endothelium and near collagen fibrils.The total cross‐sectional area of lymphatic vessels was measured in semithin sections and, with pulp area, increased from the coronal region to the middle. However, both areas decreased from the middle to the apical region suggesting either that lymph flows faster as it reaches the formens of the apical delta or that some vessels leave the tooth through lateral root canals.Using the methods of light and transmission electron microscopy, therefore, we have shown that pulp lymphatic vessels exist. Questions remain, however, about their distribution within teeth, variations between teeth, and routes of exit from teeth.
Reappraisal of histogenesis in the bursal lymphoid follicle of the chicken
Authors: Lupetti Mario , Dolfi Amelio , Giannessi Francesco , Bianchi Francesco , Michelucci Sergio 
Published: February 2005

AbstractThe development of the bursal follicle and the appearance of the follicle‐associated epithelial (FAE) cell and the reticuloepithelial (REp) cell were studied. The stadied. The stages of development of the bursal follicle were observed by light and electron microscopy; an anticytokeratin monoclonal antibody was also used. At the beginning of folicle development, a mesenchymal cell cluster is observed in the tunica propria; the cluster becomes wedged in a niche of the surface epithelium, and gradually it is completely surounded by the epithelium itself, which closes under the clump of mesenchymal cells. The epithelial cells lying upon the mesenchymal clump become necrotic, and anumber of mesenchymal cells bulge out, forming the FAE cells. The epithelial cells that hav closed under the mesenchymal nodule become stratified and form the REp cells; they become star‐shaped because the mdedullarylymphoid cells grow between them. Finally, the cortex in formed, possibly as a result of the migration of medullary cells before they peripheralize. it is concluded that FAE cells are not specialized It is concluded that FAE cells are not specialized epithelial cells, as they do not react to an anticytokeratin monoclonal antibody; on the contrary, they are formed by mesenchymal stemcells that bulge into the lumen and change their character after moving into the epithelium. The REp cells appear in the follicular primordium shortly after the bursal follicle begins to develop; the pronounced reactivity of the REp cells to an anticytokeratin monoclonal antibody supports the hypothesis of their epithelial origin.
The role of the mesenchyme in mouse neural fold elevation. II. Patterns of hyaluronate synthesis and distribution in embryos developing in vitro
Authors: Morris‐Wiman Joyce , Brinkley Linda L. 
Published: February 2005

AbstractHyaluronate (HA) distribution patterns were examined in the cranial mesenchyme underlying the mesencephalic neural folds of mouse embryos maintained in roller tube culture. Using standard image‐processing techniques, the digitized images of Alcian blue‐stained or 3H‐glucosamine‐labeled sections digested with an enzyme specific for HA, were subtracted from adjacent, undigested sections. The resultant difference picture images (DPI) accurately depicted the distribution of stained or labeled HA within the cranial mesenchyme. 3H‐glucosamine‐labeled HA was distributed uniformly throughout the cranial mesenchyme as 12, 18, and 24 hr of culture. By contrast, the mesenchyme was uniformly stained with Alcian blue at 12 hr, but stain intensity decreased in the central regions of the mesenchyme at 18 and 24 hr.HA distribution patterns were also examined in the cranial mesenchyme of embryos cultured in the presence of diazo‐oxo‐norleucine (DON), a glutamine analogue that inhibits glycosaminoglycan and glycoprotein synthesis. In DON‐treated mesenchyme, Alcian blue staining of HA was decreased from that in controls at 12, 18, and 24 hr. However, incorporation of 3H‐glucosamine into HA was increased. The distribution of labeled HA within treated mesenchyme as 12, 18, and 24 hr resembled that in controls at 12 hr.These results indicate that the distribution of HA within the cranial mesenchyme of normal mouse embryos during neural fold elevation and convergence is not determined solely by regional differences in HA synthesis. We propose that HA distribution patterns result from the expansion of the HA‐rich extracellular matrix of the central mesenchyme regions. This expansion may play a major role in fold elevation. These results also suggest that DON treatment reversibly inhibits HA synthesis, since treated mesenchymal cells retain the capability of synthesizing HA when provided with a glucosamine substrate. Patterns of 3H‐glucosamine incorporation by DON‐treated mesenchyme are similar to those observed in control mesenchyme prior to mesenchymal expansion at 12 hr.
Laminin expression in the mouse lung increases with development and stimulates spontaneous organotypic rearrangement of mixed lung cells
Authors: Schuger Lucia , Varani James , Killen Paul D. , Skubitz Amy P. N. , Gilbride Kevin 
Published: February 2005

AbstractThe recent establishment of a role for laminin in mouse lung organogenesis (Schuger et al., 1990a,b, 1991) prompted us to study its expression in the developing lung. Laminin A and B chains were detected in the murine lung from the first hours of development onward. In situ hybridization of mRNA as well as SDS‐PAGE studies of lung cells in monoculture indicated that both epithelium and mesenchyme produce complete laminin molecules. Quantitative analysis of the in situ hybridization studies showed a gradual increase in laminin expression during development which was further supported by immunohistochemistry and ELISA. The overall pattern of expression suggested that the effects of laminin in morphogenesis were not restricted to a particular stage of development. Furthermore, the increase in expression during late development supported a role for the molecule in the fetal lung, which was not previously established. We next determined whether the increase in laminin production modulated the behavior of fetal lung cells as compared with their embryonic counterparts. We previously showed that organotypic pattern formation does not occur in cultures of mixed embryonic lung cells unless exogenous laminin is added (Schuger et al., 1990b). Organotypic pattern formation is the result of cell sorting into epithelial and mesenchymal compartments and further rearrangement in a pattern resembling the tissue of origin. In the present study, we demonstrated that organotypic pattern formation occurs spontaneously in cultures of mixed fetal lung cells, which express high laminin levels. Pattern formation was abolished by antibodies to laminin. These studies suggest a correlation between laminin expression and the ability of lung cells in culture to reproduce normal tissue patterns. We conclude that laminin is critical for epithelial‐mesenchymal recognition and further morphogenic interaction during both the embryonic and fetal stages of lung development. © 1992 Wiley‐Liss, Inc.
Noncoordinate developmental regulation of N‐cadherin, N‐CAM, integrin, and fibronectin mRNA levels during myoblast terminal differentiation
Authors: MacCalman Colin D. , Bardeesy Nabeel , Holland Paul C. , Blaschuk Orest W. 
Published: February 2005

AbstractN‐cadherin, N‐CAM, fibronectin, and β1‐integrins have been implicated in the control of myoblast fusion to form multinucleate myotubes, a critical step in the terminal differentiation of skeletal muscle. We have analyzed the temporal pattern of expression of mRNA transcripts encoding these adhesion molecules during the terminal differentiation of C2 mouse myoblasts. The accumulation of mRNA transcripts encoding N‐cadherin, N‐CAM, fibronectin, β5‐integrin, and β1‐integrin subunits was developmentally, but not coordinately, regulated. N‐cadherin and integrin subunit expression was maximal in profusion myoblasts and declined thereafter. In contrast, N‐CAM mRNA levels were low in prefusion myoblasts, and increased coincident with the onset of terminal differentiation. Fibronectin mRNA levels were also low in myoblasts, and they did not increase until after cell fusion had occurred. The results indicate that despite their lack of coordinate regulation maximal levels of mRNA transcripts encoding adhesion molecules are present at a stage which corresponds to the peak of the active phase of myoblast fusion. © 1992 Wiley‐Liss, Inc.
Clonal analysis of cardiac morphogenesis in the chicken embryo using a replication‐defective retrovirus. III: Polyclonal origin of adjacent ventricular myocytes
Authors: Mikawa Takashi , Cohen‐Gould Leona , Fischman Donald A. 
Published: February 2005

AbstractReplication‐incompetent variants of the avian spleen necrosis virus (SNV) encoding cytoplasmic or nuclear‐directed β‐galactosidase (β‐gal) have been used to trace the clonal growth of myocytes during left ventricular free‐wall formation. Tubular‐stage hearts were infected with a mixed suspension of both retroviruses and, after hatching, the progeny of marked cells in the ventricular wall were examined by X‐gal histochemistry. When a small number of virions was introduced individual blue patches contained myocytes with only one label type (cytoplasmic or nuclear). These results confirmed our previous conclusion that each cluster or patch represents a single clone (Mikawa et al., 1992, Dev. Dynamics, 193:11–23). Each of these clones formed a cone‐shaped patch which often extended through the entire thickness of the ventricular myocardium, but typically each patch was heterogeneous, containing a mixture of labeled and unlabeled cells. We then asked whether the two populations of myocytes in each patch were clonally related or generated from more than one progenitor. When hearts were infected with high titer viral suspensions many patches were observed in which cytoplasmic‐tagged myocytes were intermingled with nuclear‐tagged myocytes. Thus, the cone‐shaped myocyte patches in the ventricular wall are polyclones derived from separate progenitors in the precardiac mesoderm. This finding led us to examine the separation of clonally related ventricular myocytes in the developing hearts. Embryos were infected with retroviral suspensions at varying stages of development and the resulting colonies examined after hatching. Infections on embryonic days one or two (E1, E2) gave rise to transmural colonies, whereas infection at stages later than E3 resulted in smaller clusters which were not transmural, i.e., the patches filled only a layer of each cone. This result is most simply explained by myocyte migration until E2 but with progressively restricted myocyte movements after E3. © 1992 Wiley‐Liss, Inc.
Differential expression of the two δ‐crystallin genes in lens and non‐lens tissues: Shift favoring δ2 expression from embryonic to adult chickens
Authors: Li Xuan , Zelenka Peggy S. , Piatigorsky Joram 
Published: February 2005

AbstractChicken argininosuccinate lyase (ASL)/δ‐crystallin, a lens enzyme‐crystallin, is encoded in two linked genes (δ1 and δ2); only the δ2 polypeptide contains ASL activity. Here we have quantified δ1‐ and δ2‐crystallin mRNA in the lens, cornea, neural retina, heart, and brain at different stages of embryonic development and in 1‐wk‐old and 1‐yr‐old chickens by the polymerase chain reaction using internal δ1 and δ2 RNA standards. The δ1/δ2 mRNA ratio differed for every tissue and was regulated during development. In the embryo there was more δ1 than δ2 mRNA in the lens (50–100 times), cornea (3–4 times), and neural retina (2–20 times), about equal amounts of δ1 and δ2 mRNA in the heart, and more δ2 mRNA in the brain (15 times). δ1‐Crystallin mRNA differentially decreased in every tissue after hatching; by contrast, the δ2 mRNA remained about the same except for the lens, where it decreased 50‐fold between 1 wk and 1 yr after hatching. In the 1‐yr‐old chicken, the δ2/δ1 mRNA ratios were 7 in the lens, 175 in the cornea, 22 in the neural retina, 107 in the heart, and 136 in the brain, indicating that δ2‐crystallin is strongly favored in all adult tissues of the chicken. The excess of δ1 to δ2 mRNA in the embryonic lens, cornea, and neural retina is intriguing, and suggests some connection with developing transparent eye tissues. Finally, we raise the possibility that expression of both δ‐crystallin genes may create tetrameric ASL isoenzymes (perhaps with different specific activities). The unexpected predominance of δ2 mRNA in the 1‐yr‐old lens suggests that both the enzymatic and refractive functions of ASL/δ‐crystallin are operative and spatially separated, with the enzymatic role present in the cortical fibers and the refractive role in the center of the lens. © 1993 wiley‐Liss, Inc.
Crooked Neck Dwarf (cn) mutant chicken skeletal muscle cells in low density primary cultures fail to express normal α ryanodine receptor and exhibit a partial mutant phenotype
Authors: Airey Judith A. , Deerinck Thomas J. , Ellisman Mark H. , Houenou Lucien J. , Ivanenko Anna , Kenyon James L. , McKemy David D. , Sutko John L. 
Published: February 2005

AbstractThe Crooked Neck Dwarf (cn) mutation in chickens causes marked changes in intact embryonic skeletal muscle. We have investigated whether the cn/cn phenotype develops in vitro, and if cultured muscle cells are suitable for studies of this mutation. The properties of cn/cn muscle cells maintained in low density primary cultures (6.25 × 103 cells/cm2) are described in this report. In normal muscle cells, the α ryanodine receptor (RyR) isoform appears prior to, and at greater levels than, the βRyR, and is detected in mononucleated myocytes. The βRyR isoform appears within 24 hr after the initiation of myotube formation, which is earlier than anticipated from studies with intact embryonic muscle. Normal αRyR protein is not detected in cultured cn/cn muscle cells, whereas the βRyR, the α1‐subunit of the dihydropyridine receptor, the sarcoplasmic reticulum Ca2+‐ATPase, and calsequestrin are expressed at comparable levels in normal and mutant muscle cells. Calcium transients elicited by electrical stimulation, acetylcholine, and caffeine are similar in normal and cn/cn cultured myotubes and are blocked by ryanodine in both cell types. In addition, comparable L‐ and T‐type calcium currents are observed in normal and mutant muscle cells, suggesting that both the α1‐subunit of the dihydropyridine receptor and the βRyR in mutant muscle cells are functional. Normal and cn/cn muscle cells proliferate and form myotubes in a similar manner. These latter events do not appear to depend on sarcoplasmic reticulum calcium release, as they also occur in normal muscle cells in which calcium release is prevented by chronic treatment with 100 μM ryanodine. Both cn/cn and ryanodine‐treated normal muscle cells exhibit morphological changes similar to those observed in intact cn/cn skeletal muscle. Thus, the mutant phenotype observed in ovo is partially expressed under low density culture conditions, and neither βRyR protein nor its function appear to be capable of preventing the associated changes. © 1993 Wiley‐Liss, Inc.
Test of a model for the effects of retinoic acid on urodele limb regeneration
Authors: Ludolph David C. , Cameron Jo Ann , Stocum David L. 
Published: February 2005

AbstractPrevious studies have shown that in axolotls (Ambystoma mexicanum), retinoic acid (RA) treatment evokes pattern completion in limb regenrates derived from anterior and dorsal half zeugopodia (lower arms and legs), but causes regenerative failure in posterior and ventral half zeugopodia. Pattern completion in anterior and dorsal half limbs may be explained by postulating that intercalary regeneration occurs in the anteroposterior (AP) and dorsoventral (DV) axes between blastema cells that are posteriorized (anterior half limb) or ventralized (dorsal half limb) by RA, and circumferential anterodorsal cells that remain unaffected by RA and thus maintain their original positional indentities. The contrasting regenerative failure of RA‐treated posterior and ventral half zeugopodia may likewise be explained by postulating that all the blastema cells in the posterior half are posteriorized, and all the cells in the ventral half are ventralized by RA, thus eliminating differentials in transverse positional identity essential for blastema formation and outgrowth. To test these postulates we grafted blastemas derived from limbs halved in the AP and DV axes of control and RA‐treated animals to untreated whole limb stumps and analyzed the patterns of supernumerary (SN) regeneration. The site or location of SN formation will demonstrate (1) whether RA has posteriorized and ventralized the positional identity of the blastema cells and (2) if blastema cells in the periphery of the anterodorsal quadrant of the limb are resistant to these RA‐induced changes in positional identity. Our results are consistent with a model in which RA posteriorizes positional identity in both halves of the anteroposterior axis and ventralizes it in both halves of the dorsoventral axis, while circumferential anterodorsal cells maintain their original positional identities. In addition, this model can explain why systemically administered RA in urodeles does not induce transverse axial duplications in zeugopodial regenerates of whole limbs, like it does in regenerating anuran and developing chick limb buds. © 1993 Wiley‐Liss, Inc.
Cellular morphology and extracellular space at rhombomere boundaries in the chick embryo hindbrain
Authors: Heyman Isobel , Kent Andrew , Lumsden Andrew 
Published: February 2005

AbstractThe chick embryo hindbrain is a segmented region of the CNS characterised by repeated blocks of neuroepithelial cells, known as rhombomeres. Individual rhombomeres are polyclonal compartments, defined both by cell lineage restriction and by the restricted expression of development control genes, that later acquire specific patterns of neuronal differentiation and axon outgrowth. The interfaces between adjacent rhombomeres are defined by boundaries across which cells do not move; the boundaries contain specialised cells and are preferentially colonised at early stages of development by extending axons. In this study, routine electron microscopy and high‐pressure cryopreservation, a technique that avoids artifacts of chemical fixation, have been used to examine the morphology of rhombomere boundaries through a staged series of chick embryos. We find that the boudary regions contain enlarged extracellular spaces and that these form conduits for axons subsequently extending in the circumferential plane of the hindbrain. Labeling the ventricular surface of the neuroepithelium with DiI crystals in aqueous suspension revealed the morphology of individual cells in the intact neural tube, and demonstrated unusual fan‐shaped arrays of cells at the boundaries. These findings contribute further to the evidence that cells at rhombomere boundaries differ from those in rhombomere centres, and leads to hypotheses about both the mechanism of development of the boundaries, and the role they may play in hindbrain patterning. © 1993 Wiley‐Liss, Inc.
Effects of calcium deficiency on chondrocyte hypertrophy and type X collagen expression in chick embryonic sternum
Authors: Reginato Anthony M. , Tuan Rocky S. , Ono Tamao , Jimenez Sergio A. , Jacenko Olena 
Published: February 2005

AbstractMaintenance of chick embryos in long‐term culture without their calcareous eggshell is a useful method for studying the relationship between calcium homeostasis and cell differentiation during skeletogenesis. Previously, we have shown that in shell‐less (SL) embryos, calcium deficiency induces a cartilage‐like phenotype in osteogenic tissues, such as calvaria (Jacenko and Tuan [1986] Dev. Biol. 115:215). In this investigation, we have studied the relationship between cartilage calcification and hypertrophy, and the expression of type X collagen, a specific product of hypertrophic chondrocytes. For this study, the cephalic (calcifying) and caudal (permanently cartilaginous) regions of sterna from day 18 and day 20 normal (NL) and SL embryos were metabolically labeled with [14C]‐proline. Analysis of the biosynthetic products revealed significant differences in type X collagen expression in the cephalic region of sternal cartilage. In NL tissues, type X collagen production increased from 13.1% of total collagen at day 18 to 43.7% at day 20. In contrast, in SL embryos, type X collagen was not detectable until day 20, when it represented only 1% of total collagen. Comparison of the NL and SL embryos with respect to their serum calcium level and sternal calcium content and histology revealed a direct relationship between low systemic calcium and limited cartilage hypertrophy, undermineralization, and decreased type X collagen production in the sternal cephalic cartilage. Supplementation of CaCO3 to SL embryos increased their serum and sternal calcium, and restored cartilage hypertrophy, mineralization, and type X collagen synthesis in the cephalic portion of the sterna. These findings confirm that a critical relationship exists between calcium homeostasis, chondrocyte hypertrophy, mineralization, and type X collagen synthesis in the cephalic region of sternal cartilage. These results further demonstrate the importance of calcium in the morphogenetic events of endochondral ossification, in particular the transition from hyaline cartilage to hypertrophic cartilage, and eventually to bone. © 1993 Wiley‐Liss, Inc.