Crocus sativus lectin recognizes Man3GlcNAc in the N-glycan core structure.
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Crocus sativus lectin (CSL) is one of the truly mannose-specific plant lectins that has a unique binding specificity that sets it apart from others. We studied sugar-binding specificity of CSL in detail by a solution phase method (fluorescence polarization) and three solid phase methods (flow injection, surface plasmon resonance, and microtiter plate), using a number of different glycopeptides and oligosaccharides. CSL binds the branched mannotriose structure in the N-glycan core. Substitution of the terminal Man in the Manalpha(1-3)Man branch with GlcNAc drastically decreases binding affinity much more than masking of the terminal Man in the Manalpha(1-6)Man branch. Most interestingly, the beta-Man-linked GlcNAc in N-glycan core structure contributes greatly to the binding. The effect of this GlcNAc is so strong that it can substantially offset the negative effect of substitution on the nonreducing terminal Man residues. On the other hand, the GlcNAc that is usually attached to Asn in N-glycans and the l-Fuc linked at the 6-position of the GlcNAc are irrelevant to the binding. A bisecting GlcNAc neither contributes to nor interferes with the binding. This unique binding specificity of CSL offers many possibilities of its use in analytical and preparative applications. (+info)
Angioblast differentiation is influenced by the local environment: FGF-2 induces angioblasts and patterns vessel formation in the quail embryo.
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The embryonic vasculature forms by the segregation, migration, and assembly of angioblasts from mesoderm, a process termed vasculogenesis. The initial role of fibroblast growth factor 2 (FGF-2) in vascular development appears to be in the induction of endothelial precursors, angioblasts. Quail somites transplanted into chick embryos will give rise to angioblasts of quail origin. The number of angioblasts present within the chimera is dependent on the host environment. Angioblast induction can be demonstrated in vitro by the addition of FGF-2 to cultures of dissociated somitic mesoderm, as assessed by QH-1 epitope expression. Manipulation of FGF-2 concentration in the quail/chick chimeras by FGF-2 peptide or neutralizing antibody injections increases or decreases angioblast induction in the predicted manner. To better control growth factor release in vivo we have implanted beads that release FGF-2 into the embryonic environment. FGF-2 beads implanted into the somite induce angioblast differentiation in the epithelial somite; whereas, beads lateral to the somitic mesoderm induce the formation of ectopic vessels. These studies suggest that FGF-2 is important for both the induction of angioblasts and the assembly of angioblasts into the initial vasculature pattern. (+info)
Fate determination of neural crest cells by NOTCH-mediated lateral inhibition and asymmetrical cell division during gangliogenesis.
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Avian trunk neural crest cells give rise to a variety of cell types including neurons and satellite glial cells in peripheral ganglia. It is widely assumed that crest cell fate is regulated by environmental cues from surrounding embryonic tissues. However, it is not clear how such environmental cues could cause both neurons and glial cells to differentiate from crest-derived precursors in the same ganglionic locations. To elucidate this issue, we have examined expression and function of components of the NOTCH signaling pathway in early crest cells and in avian dorsal root ganglia. We have found that Delta1, which encodes a NOTCH ligand, is expressed in early crest-derived neuronal cells, and that NOTCH1 activation in crest cells prevents neuronal differentiation and permits glial differentiation in vitro. We also found that NUMB, a NOTCH antagonist, is asymmetrically segregated when some undifferentiated crest-derived cells in nascent dorsal root ganglia undergo mitosis. We conclude that neuron-glia fate determination of crest cells is regulated, at least in part, by NOTCH-mediated lateral inhibition among crest-derived cells, and by asymmetric cell division. (+info)
Localization of calcium and zinc in the sperm storage tubules of chicken, quail and turkey using X-ray microanalysis.
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Sperm storage tubules from the utero-vaginal junction of chickens, quails and turkeys were analysed for calcium and zinc using X-ray microanalysis of ultra-rapidly frozen tissue in a scanning electron microscope. This technique enabled the tubular fluid surrounding the stored spermatozoa and the intracellular content of the cells of the sperm storage tubules to be analysed separately and, by using standards with known concentrations, their elemental concentrations were estimated. The mean (+/- SEM) concentration of calcium in the tubular fluid from chickens, quails and turkeys was 17 +/- 3, 19 +/- 3 and 17 +/- 4 mmol kg(-1) wet weight, respectively. The intracellular calcium concentration of the cells of the tubules did not differ significantly from these values and was also similar in the mucosal epithelial cells of the utero-vaginal junction. Zinc was localized in the cells of turkey sperm storage tubules and tubular fluid, but at low concentrations. No zinc could be detected in corresponding structures from chickens and quails. The concentration of calcium in the tubular fluid is within the range known to inhibit the motility of spermatozoa, supporting this function for calcium during storage. Zinc is known to depress turkey sperm metabolism and it may also be involved in inducing quiescence of spermatozoa during storage in this species. (+info)
Innervation pattern of substance P- and calcitonin gene-related peptide-immunoreactive nerves of the cerebral arteries in the quail.
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The pattern of cerebrovascular substance P (SP)- and calcitonin gene-related peptide (CGRP)-immunoreactive (IR) innervation was investigated in the quail. SP- and CGRP-IR nerves were relatively a few in the rostral part of the anterior circulation, and very scanty or lacking in its caudal part and the whole of the posterior circulation. A significant finding was that the anterior circulation in the majority of individuals is furnished with a varying proportion of SP-IR nerves with or without CGRP immunoreactivity. There was a good correlation in the expression of CGRP immunoreactivity between SP-IR cells in the ophthalmic division of the trigeminal ganglion and SP-IR nerves supplying the major cerebral arteries. In the quail, SP- and CGRP-IR fiber bundles are usually present in the internal ethmoidal artery (IEA). From these and other findings, it is most probable that cerebral perivascular SP- and CGRP-IR nerves are mainly derived from the same categories of neurons in the primary sensory ganglion via the IEA. The close association of varicose SP-IR axons to the nerve cells in the pial arteries suggests that these intrinsic neurons may play some vasocontrolling roles through the modulatory effect of their pericellular SP-IR axons. (+info)
Dual origin and segmental organisation of the avian scapula.
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Bones of the postcranial skeleton of higher vertebrates originate from either somitic mesoderm or somatopleural layer of the lateral plate mesoderm. Controversy surrounds the origin of the scapula, a major component of the shoulder girdle, with both somitic and lateral plate origins being proposed. Abnormal scapular development has been described in the naturally occurring undulated series of mouse mutants, which has implicated Pax1 in the formation of this bone. Here we addressed the development of the scapula, firstly, by analysing the relationship between Pax1 expression and chondrogenesis and, secondly, by determining the developmental origin of the scapula using chick quail chimeric analysis. We show the following. (1) The scapula develops in a rostral-to-caudal direction and overt chondrification is preceded by an accumulation of Pax1-expressing cells. (2) The scapular head and neck are of lateral plate mesodermal origin. (3) In contrast, the scapular blade is composed of somitic cells. (4) Unlike the Pax1-positive cells of the vertebral column, which are of sclerotomal origin, the Pax1-positive cells of the scapular blade originate from the dermomyotome. (5) Finally, we show that cells of the scapular blade are organised into spatially restricted domains along its rostrocaudal axis in the same order as the somites from which they originated. Our results imply that the scapular blade is an ossifying muscular insertion rather than an original skeletal element, and that the scapular head and neck are homologous to the 'true coracoid' of higher vertebrates. (+info)
Relationship between retroviral DNA integration and gene expression.
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Although retroviruses can integrate their DNA into a large number of sites in the host genome, factors controlling the specificity of integration remain controversial and poorly understood. To assess the effects of transcriptional activity on integration in vivo, we created quail cell clones containing a construct with a minigene cassette, whose expression is controlled by the papilloma virus E2 protein. From these clones we derived transcriptionally active subclones expressing the wild-type E2 protein and transcriptionally silent subclones expressing a mutant E2 protein that binds its target DNA but is unable to activate transcription. By infecting both clones and subclones with avian leukosis virus and using a PCR-based assay to determine viral DNA integration patterns, we were able to assess the effects of both protein binding and transcriptional activity on retroviral DNA integration. Contrary to the hypothesis that transcriptional activity enhances integration, we found an overall decrease in integration into our gene cassette in subclones expressing the wild-type E2 protein. We also found a decrease in integration into our gene cassette in subclones expressing the mutant E2 protein, but only into the protein binding region. Based on these findings, we propose that transcriptionally active DNA is not a preferred target for retroviral integration and that transcriptional activity may in fact be correlated with a decrease in integration. (+info)
Hox genes and morphological identity: axial versus lateral patterning in the vertebrate mesoderm.
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The successful organization of the vertebrate body requires that local information in the embryo be translated into a functional, global pattern. Somite cells form the bulk of the musculoskeletal system. Heterotopic transplants of segmental plate along the axis from quail to chick were performed to test the correlation between autonomous morphological patterning and Hox gene expression in somite subpopulations. The data presented strengthen the correlation of Hox gene expression with axial specification and focus on the significance of Hox genes in specific derivatives of the somites. We have defined two anatomical compartments of the body based on the embryonic origin of the cells making up contributing structures: the dorsal compartment, formed from purely somitic cell populations; and the ventral compartment comprising cells from somites and lateral plate. The boundary between these anatomical compartments is termed the somitic frontier. Somitic tissue transplanted between axial levels retains both original Hox expression and morphological identity in the dorsal compartment. In contrast, migrating lateral somitic cells crossing the somitic frontier do not maintain donor Hox expression but apparently adopt the Hox expression of the lateral plate and participate in the morphology appropriate to the host level. Dorsal and ventral compartments, as defined here, have relevance for experimental manipulations that influence somite cell behavior. The correlation of Hox expression profiles and patterning behavior of cells in these two compartments supports the hypothesis of independent Hox codes in paraxial and lateral plate mesoderm. (+info)