bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pattern of glucose transporter (Glut 1) expression in embryonic brains is related to maturation of bood‐brain barrier tightness
Authors: Dermietzel R. , Krause D. , Kremer M. , Wang C. , Stevenson B. 
Published: February 2005

AbstractA constant supply of blood‐borne glucose is vital to cerebral metabolism. Although transport of glucose into the nervous tissue, effectively separated from the blood by a functional barrier (the blood‐brain barrier, BBB), is one of the essential properties of the cerebral endothelium, little is known about its metabolic regulation and developmental expression in the BBB. In this study we provide evidence by immunocytochemistry that the pattern of the brain endothelial glucose transporter in rat brains (BBB‐GT), immunologically homologous with the human hepatoma (G2), human erythrocyte transporter (Glut 1), changes with BBB maturation. While the neuroepithelium at embryonic days 12 and 13 shows a high incidence of immuno‐detectable BBB‐GT, vascularisation of the cerebral anlage and subsequent development of vascular tightness, as evidenced by intravascularly applied horseradish peroxidase and fluorescinated dextrans, is accompanied by a significant reduction BBB‐GT expression in neuroepithelial cells and confinement of BBB‐GT expression to the cerebral endothelium. Immunoblots and Northern blots of embryonic brain homogenates corroborate this change in BBB‐GT expression in the brain anlage at the time of BBB maturation. However, low molecular weight glucose transporters, presumed to be of non‐endothelial origin, are less dramatically reduced. The development of BBB tightness, therefore, seems to play a pivotal role in the pattern of BBB‐GT expression during brain differentiation.
Effects of tunicamycin on retinoic acid induced respecification of positional values in regenerating limbs of the larval axolotl, Ambystoma mexicanum
Authors: Johnson Keith J. , Scadding Steven R. 
Published: February 2005

AbstractUrodele amphibians possess a remarkable ability to regenerate limbs following experimental or accidental amputation. Since only those parts of the limb distal to the plane of amputation usually regenerate, this suggests the existence of level‐specific positional values within the cells of the limb. Vitamin A and other retinoids respecify the positional values of regenerating limbs such that structures proximal to the actual plane of amputation are formed in the regenerating limb producing proximodistal duplications. Regenerating limbs of larval axolotls (Ambystoma mexicanum) treated with sufficient retinoic acid to induce proximodistal duplication were also treated via implantation with tunicamycin, a drug which blocks the synthesis of glycoproteins by blocking N‐glycosylation of proteins. Tunicamycin was shown to inhibit the proximalizing effects of retinoic acid. This indicates that asparaginelinked glycoproteins may be essential to the process through which retinoic acid induces these effects in the regenerating limb and that glycoproteins may be responsible for specifying positional values in regeneration blastema cells.
JunB does not inhibit the induction of c‐Jun during the retinoic acid induced differentiation of F9 cells
Authors: Kwon Moosik , Oshima Robert G. 
Published: February 2005

AbstractJunB, a member of the jun gene family of transcription factors, is distinguished from c‐Jun by its differential activity on certain arrangements of promoter regulatory elements and the ability of JunB to inhibit the action of cJun in both transforming and trans‐activating assays. We have tested the potential negative regulatory role of JunB during the retinoic acid induced differentiation of F9 murine embryonal carcinoma cells. Constitutive expression of high levels of JunB in F9 cells failed to inhibit the differentiation dependent induction of c‐Jun or the coincident expression of differentiation markers keratin 8 and 18, tissue plasminogen activator, and laminin Bl. Among these marker genes, keratin 18, has been shown to contain an AP‐1 binding site, TGA(C/G)TCA, which is essential for high level, differentiation dependent expression and which is transactivated by Jun and Fos proteins. These results suggest that JunB does not play a major negative or positive regulatory role during the retinoic acid induced differentiation of F9 cells.
Positional control of mesoderm movement and fate during avian gastrulation and neurulation
Authors: Garcia‐Martinez Virginio , Schoenwolf Gary C. 
Published: February 2005

AbstractSegments of primitive streak from donor quail embryos at stages of gastrulation and neurulation were transplanted heterotopically and isochronically to primitive streaks of host chick embryos. The subsequent movement and fate of grafted cells was determined using the quail nucleolar marker to define grafted cells. The pattern of movement of grafted cells depended on their new position within the primitive streak, not on their original position. When cells of cranial regions were placed more caudally, they moved to mesodermal subdivisions that were located lateral to those they would have populated if left in their original position. When caudal segments were placed more cranially, they moved to more medial mesodermal subdivisions. Whether the fate of grafted cells corresponded to their original location or their new location depended on both their level of origin and their new position. Cells from heterotopically transplanted Hensen's nodes, which migrated to the somitic and more lateral mesoderm, self‐differentiated notochords. Similarly, in some cases, heterotopically transplanted prospective somitic cells, which migrated to lateral plate mesoderm, formed ectopic somites. In other cases, however, grafted cells contributed to the host's somites, intermediate mesoderm, and lateral plate mesoderm. Moreover, prospective somitic cells, which migrated to the extraembryonic lateral plate mesoderm, changed their fate and formed extraembryonic lateral plate mesoderm; and prospective lateral plate mesoderm cells, which migrated to the somitic mesoderm, formed somites as well as intermediate mesoderm and lateral plate mesoderm. These results suggest that the movement of primitive streak cells to various mediolateral subdivisions of the mesodermal stream is determined solely by their craniocaudal position within the streak, but that determination of cell fate involves a combination of self‐differentiation and positional regulation. Cells from cranial levels of the primitive streak exhibit a considerably greater potential to self‐differentiate than those from more caudal levels, and cranial cells are more likely to migrate as a coherent group, unlike more caudal cells, which tend to freely disperse within host structures. © 1992 Wiley‐Liss, Inc.
Retinoic acid‐induced change in anteroposterior positional identity in regenerating axolotl limbs is dose‐dependent
Authors: Monkemeyer Jon , Ludolph David C. , Cameron Jo Ann , Stocum David L. 
Published: February 2005

AbstractRetinoic acid (RA) induces pattern duplication in the proximodistal (PD) axis of axolotl limb regenerates. The effect is dose‐dependent, with the maximum extent of duplication being evoked at a dose of 150 μ RA/g body weight, The same dose of RA induces maximum pattern completion in the anteroposterior (AP) axis of regenerating anterior half or double anterior half limbs. RA inhibits the regeneration of posterior half or double posterior half limbs (Kim, W.S., and Stocum, D.L. [1986] Dev Biol 114:170–179). The effects of lower doses of RA on the AP axis of limb regenerates have not been tested and thus it is not known whether the effects of RA on positional identity in this axis are dose‐dependent or are all‐or‐none. To answer this question, we examined the effects of a range of doses of RA on AP positional identity in regenerating double anterior and double posterior axolotl forelimbs and hindlimbs constructed by exchanging the anterior and posterior halves of right and left zeugopodia as either autografts or homografts. Ten days after the exchange, the double half zeugopodia were amputated through their distal ends. At 4 days postamputation, the animals were injected intraperitoneally with 20, 50, 75, or 100 μg RA/g body weight and the constructs allowed to regenerate for at least 6 weeks. Control double anterior forelimbs and hindlimbs formed symmetrical regenerates with an average of two and 1.8 anterior digits, respectively. RA treatment induced the blastema of double anterior zeugopodia to regenerate missing posterior structures in mirror‐image patterns and to duplicate zeugopodial and stylopodial elements in the PD axis. The extent of posterior regeneration and PD duplication was proportional to dose. Control double posterior forelimbs and hindlimbs produced symmetrical regenerates with an average of 2.4 and 3.3 posterior digits, respectively. Regeneration was inhibited at 100% frequency at doses above 50 μg of RA, but regeneration took place with increasing frequency at the 50 and 20 μg doses. We conclude from these data that RA posteriorizes AP positional identity in a dose‐dependent way, analogous to the dose‐dependent proximalization of positional identity reported previously for the PD axis. © 1992 Wiley‐Liss, Inc.
Mullerian inhibiting substance binding and uptake
Authors: Catlin E. A. , Ezzell R. M. , Donahoe P. K. , Manganaro T. F. , Ebb R. G. , MacLaughlin D. T. 
Published: February 2005

AbstractMullerian inhibiting substance (MIS) is a 140,000 Mr Sertoli cell derived glycoprotein with a critical regulatory role in the male fetus initiated presumably by ligand binding with receptor. To localize this binding species we performed time course incubations of cultured fetal rat lungs or control tissues with MIS, applied rabbit anti‐MIS IgG, and fluorescein conjugated antirabbit IgG, and examined specimens with laser confocal microscopy. Punctate surface fluorescence followed by cytosolic and nuclear localization in lung consistent with specific adsorptive endocytosis was seen. Confocal imaging also detected MIS binding to the Mullerian duct in the urogenital ridge. Crosslinking of 125I‐MIS with plasma membranes revealed a high molecular mass binder with signal displaceable by excess unlabeled ligand. These data support the hypothesis that a specific plasma membrane binding protein for MIS exists. © 1992 Wiley‐Liss, Inc.
Effect of systemic calcium deficiency on the expression of transforming growth factor‐β in chick embryonic calvaria
Authors: Sato Tomotaro , Tuan Rocky S. 
Published: February 2005

AbstractThe developmental process of intramembranous ossification involves bone formation directly from mesenchymal differentiation without a cartilage intermediate. We have previously observed that systemic calcium deficiency in the developing chick embryo, produced by long‐term shell‐less culture, results in the appearance of chondrocyte‐like cells in the calvarium, a parietal bone which normally develops via intramembranous ossification. This investigation aims to analyze the mechanism underlying this calcium deficiency–related, aberrant appearance of cartilage phenotype in the chick embryonic calvarium. In view of the reported involvement of transforming growth factor β (TGF‐β) in osteogenesis and chondrogenesis, we have examined and compared here the expression of TGF‐β in the chick embryonic calvaria of normal (in ovo development, NL), shell‐less (SL), and calcium‐supplemented SL (SL + Ca) embryos. TGF‐β expression was analyzed at the mRNA level by blot and in situ cDNA hybridization, and at the protein level by immunohistochemistry and immunoblotting. The results presented here indicate that: (1) TGF‐β is expressed in the chick embryonic calvarium by both periosteal cells and osteocytes, as revealed by in situ hybridization and immunohistochemistry; (2) TGF‐β expression is significantly increased in SL calvarium compared to NL calvarium, at both protein and mRNA levels; (3) the number of TGF‐β expressing cells increases in the SL calvarium, particularly along the central, subcambial core region of the bone; and (4) exogenous calcium repletion to the SL embryo affects the expression of TGF‐β such that the pattern approaches that in the NL embryo. Taken together, these results indicate that altered TGF‐β expression accompanies the aberrant appearance of cartilage phenotype caused by systemic calcium deficiency. We postulate that normal cellular differentiation along the osteogenic pathway during embryonic intramembranous ossification is crucially dependent on regulated TGF‐β expression. © 1992 Wiley‐Liss, Inc.
Sense and antisense TGFβ3 mRNA levels correlate with cardiac valve induction
Authors: Potts J. D. , Vincent E. B. , Runyan R. B. , Weeks D. L. 
Published: February 2005

AbstractThe formation of the valves in the heart is a spatially and temporally controlled process. A tissue interaction between the endothelium and its adjacent myocardium initiates the transformation of the endothelium into the mesenchymal precursors of the heart valve. One or more of the molecules implicated as critical for valve formation are members of the transforming growth factor β family of molecules. Presented here is a spatial and temporal analysis of TGFβ and TGFβ3 in the chick heart during valve formation. We show that TGFβ mRNA is concentrated in AV canal tissue where valve formation will occur, consistent with previous observations that TGFβ3 production is critical during valve formation. Additionally, an RNA complementary to TGFβ3 encoding mRNA is present in the heart. The temporally controlled appearance of RNA complementary to TGFβ3 suggests that this molecule may play a role in the regulation of TGFβ3 production in the heart. © 1992 Wiley‐Liss, Inc.
Differences in the histogenesis of EDL and diaphragm in rat
Authors: Yiping Ling , Appelt Denah , Kelly Alan M. , Franzini‐Armstrong Clara 
Published: February 2005

AbstractWe have examined the histogenesis of the diaphragm and extensor digitorum muscle in rat embryos, with the aim of defining differences in developmental patterns that can be related to the functional requirements of these muscles during and after development.Patterns of interactions between myotubes and other cells, and frequency of gap junctions are quite different in the two muscles. In diaphragm, primary myotubes (at day 16 in utero) are closely associated with each other, forming parallel sheets or palisades and communicating by gap junctions. Secondary myotubes have formed by day 18, but are immature, and the frequency of gap junctions is lower. The arrangement in palisades is maintained even after fibers are separated from each other by their individual basal lamina. In EDL primary fibers at day 16 have fewer gap junctions, and the peak in communication occurs after the appearance of secondary myotubes (day 18 and 21). Secondary myotubes are more mature than in diaphragm at day 18. © 1992 Wiley‐Liss, Inc.
Embryonic expression and functional analysis of a Xenopus activin receptor
Authors: Hemmati‐Brivanlou Ali , Wright David A. , Melton Douglas A. 
Published: February 2005

AbstractWe report the isolation and characterization of a Xenopus activin receptor (XAR1). The amino acid sequence of this protein shows extensive homology with a murine activin receptor. The mRNA is expressed maternally and is ubiquitously distributed during the early stages of embryogenesis. Consistent with a possible role in mesoderm induction and patterning, interference with the normal expression of the receptor by overexpression in the early embryo results in the formation of ectopic dorsal axial structures. During neurulation the XAR1 mRNA is expressed predominantly in the presumptive brain and spinal cord, suggesting an additional function for XAR1 in neurogenesis. © 1992 Wiley‐Liss, Inc.
Effects of lithium chloride and retinoic acid on the expression of genes from the Xenopus laevis Hox 2 complex
Authors: Leroy Pascale , de Robertis Eddy M. 
Published: February 2005

AbstractWe show that Xenopus laevis has a Hox 2 complex, and that this complex is strongly conserved with the mammalian one, both in structure and in the rules of spatial and temporal sequential expression of its genes during the early stages of development. Lithium chloride and retinoic acid, two reagents known to alter axial patterning of the body when applied to Xenopus embryos, produce, respectively, embryos with reduced posterior but exaggerated anterior structures and embryos with truncation of anterior structures. We report here on the effect of these reagents on the expression of Hox 2 genes in the Xenopus embryo. LiCl has a dramatic effect on Hox genes, suppressing the expression of these genes during gastrulation and early neurulation. However, later on expression of these genes reaches significant levels, suggesting the existence of two phases in the control of Hox gene expression. Retinoic acid increases the steady state level of transcripts from Hox genes with the greatest effect on Hox 2.7, the most anterior of the genes studied. This suggests that the results obtained in EC cells (Simeone et al., 1990, 1991) reflect what occurs in vivo. Neither LiCl nor RA change the sequential order of the onset of expression of the genes, showing that these reagents do not perturb the molecular mechanisms used to establish the sequential activation of the genes of the Hox complexes. © 1992 Wiley‐Liss, Inc.
Molecular analyses of carbonic anhydrase‐II expression and regulation in the developing chicken lens
Authors: Buono Russell J. , Linser Paul J. , Cuthbertson R. Andrew , Piatigorsky Joram 
Published: February 2005

AbstractThe expression of carbonic anhydrase‐II (CA‐II) in the developing chicken lens was examined and compared with that in the retina of the chicken embryo. CA‐II expression was measured by immunohistochemistry and radioimmunoassay during development, and CA‐II mRNA was quantified by Northern blot and densitometric scanning and localized by in situ hybridization. A functional promoter of the chicken CA‐II gene was identified by transfection of primary embryonic chicken lens epithelial cells and analyzed in deletion mutants. The results establish that CA‐II makes up about 0.1% of the total soluble protein of the embryonic chicken lens, an amount insufficient to make it a candidate for an enzyme crystallin in this species. Lens fiber differentiation coincided with a loss of CA‐II mRNA and protein; by contrast, CA‐II persisted in the epithelial cells of the embryonic and mature lens. This and previous studies showed that CA‐II amounts to as much as 3% of the protein of the embryonic chicken retina and follows a different developmental time course of expression; like the lens, CA‐II decreases until day 10 in the embryonic retina, but, unlike the lens, it increases thereafter and plateaus at hatching. Progressive deletions of the 5′ flanking regions (from position −1314 to +32) of the CA‐II gene fused to the bacterial chloramphenicol acetyltransferase (CAT) reporter gene resulted in a gradual loss of promoter activity, consistent with an additive effect of putative cis‐regulatory elements found in many crystallin genes. These experiments provide the foundation for a molecular analysis of the developmental and differential regulation of the CA‐II gene in lens and retina. © 1992 Wiley‐Liss, Inc.
Association interneurons of embryonic rat spinal cord transiently express the cell surface glycoprotein SNAP/TAG‐1
Authors: Vaughn J. E. , Phelps P. E. , Yamamoto M. , Barber R. P. 
Published: February 2005

AbstractSNAP/TAG‐1 is a 135 kDa glycoprotein of the immunoglobulin superfamily that is transiently expressed upon the surfaces of developing axons. In the embryonic rodent spinal cord, this molecule is expressed by motor neurons, dorsal root ganglion cells, and commissural neurons (Yamamoto et al.: J. Neurosci. 6:3576–3594, 1986; Dodd et al.: Neuron 1:105–116, 1988). The commissural cells are a subset of early‐forming dorsal horn interneurons whose axons follow a circumferential course in the embryonic spinal cord. The axons of commissural neurons cross the developing ventral commissure to terminate on contralateral synaptic targets, whereas those of the other subset of circumferential cells, the association interneurons, remain on the same side of the spinal cord to form ipsilateral, terminal synaptic fields. The difference between the axonal trajectories of these two subsets of nerve cells raised the question of whether or not association interneurons would also express the SNAP/TAG‐1 epitope and, if so, how would this expression be related to that of the commissural cells. Immunocytochemistry for SNAP/TAG‐1 and choline acetyltransferase (ChAT) was used to answer these questions. The results indicated that association interneurons expressed SNAP/TAG‐1 epitopes and that this expression began later and lasted longer than that of the commissural neurons. Other new findings of this study included the identification of a lateral subgroup of commissural fibers that expressed SNAP/TAG‐1 later than their more medially located counterparts, and these lateral fibers were more pronounced in the thoracic spinal cord than at cervical levels. Furthermore, interesting developmental relationships were observed between SNAP/TAG‐1‐positive fibers and ChAT‐positive motor neurons in both cervical and thoracic spinal cord. Lastly, SNAP/TAG‐1 immunoreactivity was detected on the terminal collaterals of dorsal root ganglion fibers during the late prenatal period. While the function(s) of SNAP/TAG‐1 remains enigmatic, its expression in developmental time and space, along with the recent suggestion that a released form of this molecule might serve a substrate adhesion function (Furley et al.: Cell 61:157–170, 1990; Karagogeos et al.: Development 112:51–67, 1991), hint that SNAP/TAG‐1 might play a role in the migration of certain cholinergic neurons in the developing spinal cord. © 1992 Wiley‐Liss, Inc.
Talpid2 limb bud mesoderm does not express GHox‐8 and has an altered expression pattern of GHox‐7
Authors: Krabbenhoft Karen M. , Fallon John F. 
Published: February 2005

AbstractWe have studied the expression patterns of the chick homeobox‐containing genes, GHox‐7 and GHox‐8, in the talpid2 (ta2) chick mutant whose limbs have abnormal pattern. These studies provide new insight into how homeobox gene expression and limb patterning may be related. This is the first study demonstrating a natural change in GHox‐7 and GHox‐8 along the anteroposterior axis. While GHox‐7 is expressed asymmetrically in normal limb buds, it is expressed at a uniform level across the anteroposterior axis of ta2 limb buds. GHox‐8 is expressed in anterior mesoderm of normal limb buds, but is un‐detectable in ta2 limb bud mesoderm. These data are consistent with the subtle anteroposterior polarity in ta2 limbs, and allow us to propose that ta2 limb buds lack anterior positional information, but have a narrow range of posterior positional values. We suggest that in normal limb buds GHox‐8 may establish the anterior limb bud boundary. Furthermore, we point out that coexpression of GHox‐7 and GHox‐8 in normal anterior limb bud mesoderm can be correlated with the reduced apical ridge maintenance activity of this tissue, while the lack of coexpression in ta2 limb buds is correlated with the strong ridge maintenance activity in the mutant's anterior limb bud mesoderm. Last, ta2 limbs contain no dying cells in their anterior and posterior border mesoderm; nevertheless, they express GHox‐7 in these regions. These data challenge the proposal that this gene determines cell death. © 1992 Wiley‐Liss, Inc.