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61.
In vertebrates, the endoderm is established during gastrulation and gradually becomes regionalized into domains destined for different organs. Here, we present precise fate maps of the gastrulation stage chick endoderm, using a method designed to label cells specifically in the lower layer. We show that the first population of endodermal cells to enter the lower layer contributes only to the midgut and hindgut; the next cells to ingress contribute to the dorsal foregut and followed finally by the presumptive ventral foregut endoderm. Grafting experiments show that some migrating endodermal cells, including the presumptive ventral foregut, ingress from Hensen's node, not directly into the lower layer but rather after migrating some distance within the middle layer. Cell transplantation reveals that cells in the middle layer are already committed to mesoderm or endoderm, whereas cells in the primitive streak are plastic. Based on these results, we present a revised fate map of the locations and movements of prospective definitive endoderm cells during gastrulation. 相似文献
62.
Wakisaka-Saito N Kohda T Inoue K Ogonuki N Miki H Hikichi T Mizutani E Wakayama T Kaneko-Ishino T Ogura A Ishino F 《Biochemical and biophysical research communications》2006,349(1):106-114
Somatic cell nuclear transfer technology has been applied to produce live clones successfully in several mammalian species, but the success rates are very low. In mice, about half of the nuclear transfer embryos undergo implantation, but very few survive to term. We undertook detailed histological analyses of placentas from cloned mouse embryos generated from cumulus cells at 10.5 dpc of pregnancy, by which stage most clones have terminated their development. At 10.5 dpc, the extraembryonic tissues displayed several defined histological patterns, each reflecting their stage of developmental arrest. The most notable abnormality was the poor development of the spongiotrophoblast layer of diploid cells. This is in contrast to the placental hyperplasia frequently observed in somatic clones at 12.5 dpc or later stages. A variety of structural abnormalities were also observed in the embryos. Both placental and embryonic defects likely contribute to the low success rate of the mouse clones. 相似文献
63.
Equilibria and kinetics of folding/unfolding of α-lactalbumin and its two N-terminal variants were studied by circular dichroism spectroscopy. The two variants were wild-type recombinant and Glu1-deletion (E1M) variants expressed in Escherichia coli. The presence of an extra methionine at the N terminus in recombinant α-lactalbumin destabilized the protein by 2 kcal/mol, while the stability was recovered in the E1M variant in which Glu1 was replaced by Met1. Kinetic folding/unfolding reactions of the proteins, induced by stopped-flow concentration jumps of guanidine hydrochloride, indicated the presence of a burst-phase in refolding, and gave chevron plots with significant curvatures in both the folding and unfolding limbs. The folding-limb curvature was interpreted in terms of accumulation of the burst-phase intermediate. However, there was no burst phase observed in the unfolding kinetics to interpret the unfolding-limb curvature. We thus assumed a sequential four-state mechanism, in which the folding from the burst-phase intermediate takes place via two transition states separated by a high-energy intermediate. We estimated changes in the free energies of the burst-phase intermediate and two transition states, caused by the N-terminal variations and also by the presence of stabilizing calcium ions. The Φ values at the N terminus and at the Ca(2+)-binding site thus obtained increased successively during folding, demonstrating the validity of the sequential mechanism. The stability and the folding behavior of the E1M variant were essentially identical to those of the authentic protein, allowing us to use this variant as a pseudo-wild-type α-lactalbumin in future studies. 相似文献
64.
Ohhara Y Kayashima Y Hayashi Y Kobayashi S Yamakawa-Kobayashi K 《Zoological science》2012,29(2):83-89
An invertebrate biogenic amine, octopamine, plays diverse roles in multiple physiological processes (e.g. neurotransmitter, neuromodulator, and circulating neurohormone). Octopamine is thought to function by binding to G-protein-coupled receptors. In Drosophila, three β-adrenergic-like octopamine receptors (Octβ1R, Octβ2R, and Octβ3R) have been identified. We investigated the expression of three OctβR genes in embryos, larvae, and adults. These OctβRs showed distinct expression patterns in the central nervous system (CNS) throughout development, and Octβ3R expression was evident in an endocrine organ, the ring gland, in larvae. In larvae, Octβ1R, Octβ2R, and Octβ3R were expressed in salivary glands and imaginal discs, Octβ2R and Octβ3R in midgut, and Octβ3R in gonads. In adult, besides in the CNS, each OctβR was strongly expressed in ovary and testis. Our findings provide a basis for understanding the mechanisms by which OctβRs mediate multiple diverse octopaminergic functions during development. 相似文献
65.
Gnesa E Hsia Y Yarger JL Weber W Lin-Cereghino J Lin-Cereghino G Tang S Agari K Vierra C 《Biomacromolecules》2012,13(2):304-312
Spider silk is renowned for its extraordinary mechanical properties, having a balance of high tensile strength and extensibility. To date, the majority of studies have focused on the production of dragline silks from synthetic spider silk gene products. Here we report the first mechanical analysis of synthetic egg case silk fibers spun from the Latrodectus hesperus tubuliform silk proteins, TuSp1 and ECP-2. We provide evidence that recombinant ECP-2 proteins can be spun into fibers that display mechanical properties similar to other synthetic spider silks. We also demonstrate that silks spun from recombinant thioredoxin-TuSp1 fusion proteins that contain the conserved C-terminal domain exhibit increased extensibility and toughness when compared to the identical fibers spun from fusion proteins lacking the C-terminus. Mechanical analyses reveal that the properties of synthetic tubuliform silks can be modulated by altering the postspin draw ratios of the fibers. Fibers subject to increased draw ratios showed elevated tensile strength and decreased extensibility but maintained constant toughness. Wide-angle X-ray diffraction studies indicate that postdrawn fibers containing the C-terminal domain of TuSp1 have more amorphous content when compared to fibers lacking the C-terminus. Taken together, these studies demonstrate that recombinant tubuliform spidroins that contain the conserved C-terminal domain with embedded protein tags can be effectively spun into fibers, resulting in similar tensile strength but increased extensibility relative to nontagged recombinant dragline silk proteins spun from equivalently sized proteins. 相似文献
66.
Tabata S Kuroki K Wang J Kajikawa M Shiratori I Kohda D Arase H Maenaka K 《The Journal of biological chemistry》2008,283(14):8893-8901
Paired Ig-like type 2 receptors (PILRs) are one of the paired receptor families, which consist of two functionally opposite members, inhibitory (PILRalpha) and activating (PILRbeta) receptors. PILRs are widely expressed in immune cells and recognize the sialylated O-glycosylated ligand CD99, which is expressed on activated T cells, to regulate immune responses. To date, their biophysical properties have not yet been examined. Here we report the affinity, kinetic, and thermodynamic analyses of PILR-CD99 interactions using surface plasmon resonance (SPR) together with site-directed mutagenesis. The SPR analysis clearly demonstrated that inhibitory PILRalpha can bind to CD99 with low affinity (K(d) approximately 2.2 microm), but activating PILRbeta binds with approximately 40 times lower affinity (K(d) approximately 85 microm). In addition to our previous mutagenesis study (Wang, J., Shiratori, I., Saito, T., Lanier, L. L., and Arase, H. (2008) J. Immunol. 180, 1686-1693), the SPR analysis showed that PILRalpha can bind to each Ala mutant of the two CD99 O-glycosylated sites (Thr-45 and Thr-50) with similar binding affinity to wild-type CD99. This indicated that both residues act as independent and equivalent PILRalpha binding sites, consistent with the highly flexible structure of CD99. On the other hand, it is further confirmed that PILRbeta can bind the T50A mutant, but not the T45A mutant, indicating a recognition difference between PILRalpha and PILRbeta. Kinetic studies demonstrated that the PILR-CD99 interactions show fast dissociation rates, typical of cell-cell recognition receptors. Thermodynamic analyses revealed that the PILRalpha-CD99 interaction is enthalpically driven with a large entropy loss (-TDeltaS = 8.9 kcal.mol(-1)), suggesting the reduction of flexibility upon complex formation. This is in contrast to the entropically driven binding of selectins to sugar-modified ligands involved in leukocyte rolling and infiltration, which may reflect their functional differences. 相似文献
67.
We examined life history traits and spermathecal morphology of both sexual and thelytokous Schwiebea mite species to determine ecological and morphological attributes during the evolution of parthenogenesis in this lineage.
We reconstructed a molecular phylogeny of eight Japanese species using the internal transcribed spacer 1 (ITS1) of the ribosomal
DNA (rDNA) and compared the sex ratio, developmental period, and egg number (fecundity) of each species within a species group
by rearing them in the laboratory. Habitat preference was also analyzed from both collection and literature data. The reconstructed
molecular phylogeny suggested that parthenogenesis evolved independently multiple times in this lineage. There were three
clusters in the tree, in each of which the idiosoma, leg, setae, and spermathecal morphology of females was similar or identical;
this suggested that mites in the same cluster were sister species. There was no relationship between sexual mode and life
history traits or habitat preference. These results suggest that sexual and asexual species use different microhabitats. Because
S. similis (sexual), S. elongata (thelytokous), and S. estradai (thelytokous) were in the same cluster and spermathecae of the first two were similar while that of the last was distinctively
reduced, we hypothesized that speciation occurred in this order and that spermathecae are reduced and eventually lost during
the course of parthenogenetic evolution. 相似文献
68.
Pluripotency of a single spermatogonial stem cell in mice 总被引:2,自引:0,他引:2
69.
DNA-binding specificity, transcriptional activation potential, and the rin mutation effect for the tomato fruit-ripening regulator RIN 总被引:1,自引:0,他引:1
70.
RNA- and DNA-synthesizing activities were much lower in conjugatingand zygote cells than in vegetatively growing cells. We suggestthat a certain factor(s) which may repress RNA and DNA Syntheseswas formed during the conjugation process. (Received December 24, 1971; ) 相似文献