bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in cellular dynamics during the development of the ciliary epithelium
Authors: Reichman Eric F. , Beebe David C. 
Published: February 2005

AbstractEye growth and the formation of the ciliary folds during development depend on the maintenance of normal intraocular pressure. In this study we measured labeling index, packing density, height, and volume of the prospective ciliary epithelial cells during the early development of the eye in chicken embryos. Changes in these values were related to the formation of the ciliary folds and to experimental alterations of intraocular pressure. These variables changed independently in the outer, pigmented layer and the inner, non‐pigmented epithelial layer of the ciliary epithelium. The labeling index in the pigmented epithelium declined steadily throughout development. Decreases in cell density and increases in cell height resulted in a four‐fold increase in calculated average cell volume in the pigmented epithelium during Hamburger‐Hamilton stages 29 and 30, the day before the formation of the ciliary folds. In the non‐pigmented epithelium, the labeling index increased abruptly at stage 31, the stage at which ciliary folds begin to form. At the same time there was a three‐fold increase in average cell volume. When intraocular pressure was reduced by intubating the eye, the formation of ciliary folds was prevented. Intubation also blocked the increase in labeling index and blunted the increase in cell volume that normally occur in the non‐pigmented epithelium at the time of fold formation. In the pigmented epithelium, intubation caused a sustained, three‐ to six‐fold increase in cell volume, but had no effect on labeling index. Based on these data, we suggest that increases in cell number and volume just before and during the formation of ciliary folds contribute to the formation of the ciliary folds.
Effects of heat shock on the pattern of fibronectin and laminin during somitogenesis in Xenopus laevis
Authors: Danker K. , Hacke H. , Wedlich D. 
Published: February 2005

AbstractHeat shock causes partial disruption of the segmentation pattern during somitogenesis in Xenopus as well as in other vertebrates. However, Xenopus undergoes a different type of somite formation than that of most vertebrates: Somites are formed by rotation of cell blocks out of the paraxial mesoderm. We attempted to determine whether or not the segmentation disorder following heat shock is caused by an altered pattern of fibronectin and/or laminin, that could then effect the rotation of cell blocks. Therefore, we carried out heat shock experiments and analyzed the distribution of both ECM proteins in correlation to the position of somitic cells.Our results reveal that heat shock causes an incorrect deposition of fibronectin as well as laminin during somite formation. This leads to an intermingling of cells from different segments and to an anchorage of cells at the lateral matrix. Immunoblots show that the defects in the pattern of these ECM proteins do not correlate with a decrease of both proteins. However, immunohistological staining patterns demonstrate that oversized blocks of 20‐cell width, instead of the normal ones of about 9‐cell width, are separated out of the paraxial mesoderm following heat shock treatment. This indicates that the altered pattern of fibronectin and laminin might be a secondary effect caused by incorrect segregation and detachment of cell blocks during somitogenesis. Since anchorage of somitic cells is mostly affected by the altered distribution of fibronectin and laminin, it is more likely that both ECM proteins function in anchorage of migrating presomitic cells and in maintaining of segment borders rather than in stimulating cell rotation movements.
The role of hyaluronan‐binding protein in assembly of pericellular matrices
Authors: Yu Qin , Banerjee Shib D. , Toole Bryan P. 
Published: February 2005

AbstractHyaluronan‐dependent pericellular matrices or “coats” are expressed by a variety of cell types in culture and modulation of their expression may be important in regulation of cell interactions in vivo during development. Monoclonal antibody IVd4, which recognizes hyaluronan‐binding protein with the properties of a hyaluronan receptor, was shown to block formation of these coats by a variety of cells. Using rat fibro‐sarcoma cells, it was found that the antibody not only blocked initial formation of the coats but also caused their loss when added subsequent to formation. The loss of preformed coats in the presence of antibody occurred at 4° and 37°, implying that the function of hyaluronan‐binding protein in coat formation is not in mediating metabolic processes. The antibody also had no significant effect on hyaluronan production by the fibrosarcoma cells. In addition, hyaluronan hexasaccharide, a competitive inhibitor of the interaction between polymeric hyaluronan and its cell surface receptor, was found to inhibit coat formation. Thus it is concluded that a hyaluronan‐binding protein with the properties of a hyaluronan receptor is required for pericellular matrix formation.
Ablation of the fetal mouse spinal cord: The effect on soleus muscle cytoarchitecture
Authors: Hughes Donna S. , Schade Robert R. , Ontell Marcia 
Published: February 2005

AbstractA technique is described whereby it is possible to surgically ablate the lumbosacral spinal cord of a developing mouse fetus without interfering with fetal viability. The lumbosacral spinal cords of 14‐day in utero, 129ReJ mice were ablated with a Cooper Nd‐YAG laser, and the fetuses, enclosed in their membranes and attached to the uterus by their placentae, were allowed to develop in the abdominal cavity of the dam. The cytoarchitecture and the temporal pattern of organogenesis of aneural soleus muscles were studied in spaced, serial, transverse, ultrathin sections of muscles of 16‐ and 18‐day gestation and newborn (20‐day gestation) mice. At the time of surgery, the soleus muscle was a discrete mass consisting of primary myotubes and a pleomorphic population of mononucleated cells. Axon bundles and blood vessels were found at the muscle's periphery, but had not penetrated throughout the muscle mass. The organogenesis of the aneural muscle was remarkably similar to that of the innervated soleus muscle (Ontell et al., Am J Anat 181:267–278, 1988). In the aneural muscle, as in the innervated muscle, significant numbers of secondary myotubes formed all along the lengths of primary myotubes. Moreover, the time course of myotube formation, the dynamics of cluster formation and cluster dispersal, and the ultrastructural appearance of the myotubes mimicked that observed in innervated muscle. The frequency of necrotic myotubes was no greater in the aneural muscle than in the innervated soleus muscle. Myotube maturation was similar in aneural and innervated soleus muscles until 18 days gestation. However, at birth, aneural myotubes appeared to be slightly less mature than innervated myotubes. Thus, the major morphogenic phenomena that characterize the development of the soleus muscle appear to be independent of innervation.
Morphometric analysis of the developing, murine aneural soleus muscle
Authors: Hughes Donna S. , Ontell Marcia 
Published: February 2005

AbstractThe pattern of organogenesis of the aneural soleus muscle of the 129ReJ mouse [rendered aneural by laser ablation of the lumbosacral spinal cord at 14 days in utero (during the period of primary myotube formation, but prior to the formation of secondary myotubes)] was evaluated quantitatively with spaced, serial ultrathin sections and computer‐assisted morphometric analysis. Aneural muscles from 16‐ and 18‐day gestation and newborn mice were analyzed to determine age‐related changes in a number of parameters including: muscles' maximal girths, numbers of myotubes, myotube diameter distributions, and cluster frequency. Data were compared with a similar study of the organogenesis of the normal soleus muscle (Ontell et al: Am J Anat 181: 279–288, 1988). Basic patterns of morphogenesis of the soleus muscle were unchanged by spinal cord ablation, and differences in development between the aneural and innervated muscles were quantitative rather than qualitative. At birth, the aneural muscle contained ∼76% of the myotubes found in the innervated muscle (∼840 myotubes in the innervated muscle and ∼640 in the aneural muscle). Evidence is presented consistent with the hypothesis that primary myotube formation is reduced by ∼32% in the aneural muscles and that while extensive secondary myotube formation occurs (∼78% of the myotubes present at birth in these muscles are secondary myotubes), there is a significant reduction in the number of secondary myotubes in aneural muscles. It is suggested that the reduced numbers of secondary myotubes may be related to the reduction in the number of primary myotubes, which are known to act as scaffolds for secondary myotube formation. The time course of secondary myotube formation and of cluster formation and cluster dispersal and the number of cells per cluster are similar in age‐matched, innervated and aneural muscles. The absence of innervation has little effect on myotube growth until birth, when comparison of the myotube diameter distributions reveals a slight alteration in myotube diameter distributions of aneural as compared with innervated muscles.
The cellular basis of the convergence and extension of the Xenopus neural plate
Authors: Keller Ray , Shih John , Sater Amy 
Published: February 2005

AbstractThere is great interest in the patterning and morphogenesis of the vertebrate nervous system, but the morphogenetic movements involved in early neural development and their underlying cellular mechanisms are poorly understood. This paper describes the cellular basis of the early neural morphogenesis of Xenopus laevis. The results have important implications for neural induction. Mapping the fate map of the midneurula (Eagleson and Harris: J. Neurobiol. 21:427–440, 1990) back to the early gastrula with time‐lapse video recording demonstrates that the prospective hindbrain and spinal cord are initially very wide and very short, and thus at the beginning of gastrulation all their precursor cells lie within a few cell diameters of the inducing mesoderm. In the midgastrula, the prospective hindbrain and spinal cord undergo very strong convergence and extension movements in two phases: In the first phase they primarily undergo thinning in the radial direction and lengthening (extension) in the animal‐vegetal direction, and the second phase is characterized primarily by mediolateral narrowing (convergence) and anterior‐posterior lengthening (extension). These movements also occur in sandwich explants of the gastrula, thus demonstrating the local automomy of the forces producing them. Tracing cell movements with fluorescein dextran‐labeled cells in embryos or explants shows that the initial thinning and extension occurs by radial intercalation of deep cells to form fewer layers of greater area, all of which is expressed as increased length. The subsequent convergence and extension occurs by mediolateral intercalation of deep cells to form a longer, narrower array. These results establish that a similar if not identical sequence of radial and mediolateral cell intercalations underlie convergence and extension of the neural and the mesoderm tissues (Wilson and Keller: Development, 112:289–300, 1991). Moreover, these results establish that radial and mediolateral intercalation are the principal neural cell behaviors induced by the planar signals emanating from the dorsal involuting marginal zone (the Spemann organizer) in the early gastrula (Keller et al: Develop. Dynamics, 193: 218–234, 1992). Radial and mediolateral intercalation are induced among the 5 to 7 rows of cells comprising the prospective hindbrain and spinal cord, thus producing the massive convergence and extension movements that narrow and elongate these regions of the nervous system in the late gastrula. A more general significance of these results is that neural induction is best analyzed and understood in terms of the dynamics of the morphogenetic processes involved. © 1992 Wiley‐Liss, Inc.
Planar induction of convergence and extension of the neural plate by the organizer of Xenopus
Authors: Keller Ray , Shih John , Sater Amy K. , Moreno Cecelia 
Published: February 2005

AbstractThis paper demonstrates that convergence and extension within the neural plate of Xenopus laevis are regulated by planar inductive interactions with the adjacent Spemann organizer. The companion article (Keller et al.: Developmental Dynamics 193:199–217, 1992) showed that the prospective hindbrain and spinal cord occupy a very short and very wide area just above the Spemann organizer in the early gastrula and that these regions converge and extend greatly during gastrulation and neurulation, using a sequence of radial and mediolateral cell intercalations. In this article, we show that “planar” contact of these regions with the organizer at their vegetal edge until stage 11 is sufficient to induce convergence and extension, after which their convergence and extension become autonomous. Grafts of the organizer in planar contact with uninduced ectodermal tissues induce these ectodermal tissues to converge and extend by a planar inductive signal from the organizer. Labeling of the inducing or responding tissues confirms that only planar interactions occur. Neural convergence and extension are actually hindered in explants deliberately constructed so that vertical interactions occur. These results show unambiguously that the Spemann organizer induces the extraordinary and precocious convergence and extension movements of the Xenopus neural plate by planar interactions acting over short distances.
Mesoderm movement and fate during avian gastrulation and neurulation
Authors: Schoenwolf Gary C. , Garcia‐Martinez Virginio , Dias Mark S. 
Published: February 2005

AbstractQuail/chick transplantation chimeras were constructed during stages of gastrulation and neurulation to follow the subsequent movement and fate of cells of the primitive streak. All grafts were placed solely within the confines of the primitive streak to prevent confusion between cells that had not yet ingressed and those that had already ingressed, and transplanted cells were distinguished from host cells on the basis of a naturally occurring cell marker. Pathways of movement of ingressing cells corresponded to their level of residence within the primitive streak. Cells residing within Hensen's node (the cranial end of the primitive streak) initially migrated mainly cranially, remaining on or near the midline, and then extended caudally along the midline as regression of Hensen's node occurred. Cells residing within the nodus posterior (the caudal end of the primitive streak) migrated caudally. Cells residing at levels of the primitive streak between Hensen's node and the nodus posterior typically migrated bilaterally, confirming that such cells had not already ingressed prior to their transplantation (in which case, they would have migrated unilaterally). Subsets of these cells residing at progressively more caudal levels of the primitive streak migrated incrementally more laterally. Hensen's node contributed cells to the gut endoderm, head mesenchyme, notochord, and median hinge‐point (MHP) cells of the neural tube (future floor plate). At younger stages (i.e., stages 3a, 3b) Hensen's node contributed cells to principally the foregut endoderm and head mesenchyme, where‐as at older stages (i.e., stages 3c, 3d, 4), it contributed cells to principally the notochord and MHP region. The remaining segments of the cranial half of the primitive streak contributed cells to the various mesodermal subdivisions of the embryo, and the lengths of the segments forming these subdivisions were estimated. The most cranial level of the streak (directly behind Hensen's node) contributed cells to the most medial mesodermal subdivisions (head mesenchyme, somites) and consecutively more caudal levels of the streak contributed cells to sequentially more lateral mesodermal subdivisions (intermediate mesoderm, lateral plate mesoderm). The caudal half of the primitive streak contributed cells to the extraembryonic mesoderm, with the nodus posterior contributing cells to the most caudal extraembryonic mesoderm, including the blood islands. Our results confirm and extend the previous avian prospective fate maps, increasing our understanding of the movement and fate of cells of the gastrula and neurula stages. © 1992 Wiley‐Liss, Inc.
Expression of sarcomeric myosin in the presumptive myocardium of chicken embryos occurs within six hours of myocyte commitment
Authors: Han Y. , Dennis J. E. , Cohen‐Gould L. , Bader D. M. , Fischman D. A. 
Published: February 2005

AbstractThe distribution of sarcomeric myosin heavy chain (MyHC) has been examined immunoctochemically in the presumptive myocardial cells of chicken embryos (stages 6–10) prior to the onset of the heart beat. Embryos were stained with monoclonal antibody MF20, a reagent which recognizes all chicken sarcomeric MyHCs (Bader et al., 1982), and then examined both in whole mount by immunofluorescence and in semithin, plastic‐embedded sections following immunoperoxidase labeling. We observed that myosin could be detected as early as stage 7 (0–2 pairs of somites) in 29% of the 31 embryos examined, and by stage 8 (4 pairs of somites) more than 80% of the embryos were MF20+, Every embryo with 5 pairs of somites (stage 8+) labeled strongly with MF20. Labeling was first detected at stage 7 to 7+ as a diffuse fluorescent signal within pleomorphic cells of the splanchnic mesoderm located in two crescent‐shaped regions bordering each side of the anterior intestinal portal (AIP). With progressive development, the two crescent‐shaped regions merged at the apex of the AIP, and as the two heart tubes began fusion at stage 9, the MyHC+ regions extended cranially and medially. By somite stages 9–10, the myosin‐positive cells completely encircled the heart tube. From stages 7 to 9 the myosin signal had no sarcomeric distribution; i.e., there were no MyHC striations nor periodic repeats evident in the presumptive myocytes until late stage 9 and stage 10. Semithin sections revealed that myosin was first distributed in apical regions of the myocytes, adjacent to the pericardial coelom. The implications of these findings for myocyte determination, differentiation and morphogenesis are discussed.© 1992 Wiley‐Liss, Inc.
The influence of bone and marrow on cartilage hypertrophy and degradation during 30‐day serum‐free culture of the embryonic chick tibia
Authors: Cole Ada A. , Luchene Lawrence J. , Linsenmayer Thomas F. , Schmid Thomas M. 
Published: February 2005

AbstractIn this study, an organ culture system is defined which demonstrates complete loss of cartilage matrix from embryonic chick tibiae. Efficient loss of the cartilage matrix occurs within 30 days of serum‐free culture only when the intact tibiae containing bone, marrow, and cartilage tissue are cultured. During organ culture nonhypertrophic chondrocytes become hypertrophic and stain positively for type X collagen and alkaline phosphatase. The cartilage loses Safranin O staining, and finally all cartilage matrix disappears leaving the bony collar and marrow cells. If the tibial cartilage is separated from the bony collar and cultured alone in serum‐free medium, the nonhypertrophic chondrocytes also hypertrophy; the matrix loses Safranin O staining; however, some components of the matrix including type X collagen still remain after 30 days. In the presence of serum, the chondrocytes will hypertrophy but cartilage degradation is not evident. The results of this study support the conclusions that (1) hypertrophy is inherently programmed in the chondrocyte and (2) while Safranin O staining of cartilage cultured alone is diminished in serum‐free organ culture, the degradation of cartilage is complete only when bone and marrow are also present. © 1992 Wiley‐Liss, Inc.
Developmental expression of two antigens associated with mouse intestinal crypts
Authors: Beaulieu J.‐F. , Millane G. , Calvert R. 
Published: February 2005

AbstractTwo monoclonal antibodies were prepared against the duodenal mucosa of fourday‐old mice (MIM‐1/39 and MIM 1/130). The expression of the antigens was associated with the crypts of the small and large intestine in the fetus and adult. MIM‐1/39 was present in epithelial cells of the intervillous areas in the small intestine at 17 and 18 days of gestation; afterwards its expression was detected only in crypt cells from birth to adulthood. Transition from the mouth of the crypts to intestinal villi was abrupt. Expression of MIM‐1/39 was first detected at time of birth in the colon: In the adult, only crypt cells expressed the antigen and goblet cells were negative. Antigen MIM‐1/130 was detected from 16 to 18 days of gestation in the small intestine, in the mesenchymal matrix lying under the intervillous epithelium. After birth, it was present in the pericryptal mesenchymal matrix. This antigen was also expressed at birth in the colon and remained in the pericryptal matrix in the adult. In vivo, multiple injections of an organic extract of rat amniotic fluid to mothers, starting at 14 days of gestation, induced a profound modulation in the pattern of expression of both antigens at 17 days of gestation: The pattern of expression was comparable to that observed at least 5 days after birth in untreated animals. The expression of both antigens before crypt appearance may reflect some molecular differentiation in preparation for the formation of crypts, while their association with differentiated crypts may indicate that they have a role in the maintenance of crypt functional and/or morphological integrity. Finally, the fact that their expression can be modulated experimentally may prove to be a breakthrough for the study of crypt formation. © 1992 Wiley‐Liss, Inc.
Expression of α‐cardiac and α‐skeletal actin mRNAs in relation to innervation in regenerating and non‐regenerating rat skeletal muscles
Authors: Toyofuku Toshihiko , Hoffman John R. , Zak Radovan , Carlson Bruce M. 
Published: February 2005

AbstractThe expression of α‐cardiac and α‐skeletal actin mRNA in regenerating muscle was examined. Changes in mRNA levels were analyzed in autografted extensor digitorum longus (EDL) muscles in rats using α‐isoform specific synthetic oligonucleotides and β‐actin cDNA as probes. After autografting, the expression of α‐cardiac actin mRNA was induced; concomitantly that of α‐skeletal actin mRNA was reduced. The pattern of α‐actin mRNA expression appeared to be similar to that seen in embryonic skeletal muscle. In order to evaluate the effects of innervation on α‐actin mRNA expression in regenerating muscle, nerveless, standard, and nerve‐intact autografted muscles were examined. More complete innervation facilitated the recovery of α‐skeletal actin mRNA to control levels, but had little effect on the amount of α‐cardiac actin mRNA. We found that regenerating muscle shows the embryonic pattern of α‐actin mRNAs in the early stage and concluded that the recovery of α‐skeletal actin mRNA expression to the adult pattern is influenced by innervation, while α‐cardiac actin mRNA expression is nerve independent. © 1992 Wiley‐Liss, Inc.