pinecone/core-2020-05-10-deduplication huggingface dataset:
Bone Morphogenetic Protein-2 (BMP-2) Inhibits Muscle Development and Promotes Cartilage Formation in Chick Limb Bud Cultures

AbstractBone morphogenetic proteins (BMPs) induce ectopic cartilage and bone when implanted intramuscularly in adult rats. Expression data suggest that BMPs signal skeletal development in embryos. An important question is which cells are targets of BMP signaling in adult and embryonic tissues. Here, we examined the effect of BMP-2 on micromass cultures of chick limb bud mesenchyme. We report that BMP-2 promotes formation of cartilage and simultaneously inhibits development of muscle cells. To follow the fate of presumptive muscle cells, we replaced chick somites with quail somites at the wing level and made micromass cultures from the chimeric wings. In untreated cultures, quail cells formed muscle but not cartilage. In BMP-2-treated cultures, quail cells disappeared altogether. This suggests that BMP-2 may simultaneously promote cartilage differentiation and reduce the presumptive myogenic cell populations in regions of skeletal development
Clonal and Population Analyses Demonstrate That an EGF-Responsive Mammalian Embryonic CNS Precursor Is a Stem Cell

AbstractIn cultures of embryonic striatum, we previously reported that EGF induces the proliferation of single precursor cells, which give rise to spheres of undifferentiated cells that can generate neurons and glia. We report here that,in vitro,these embryonic precursor cells exhibit properties and satisfy criteria representative of stem cells. The EGF-responsive cell was able to generate the three major phenotypes of the mammalian CNS—neurons, astrocytes, and oligodendrocytes. Approximately 90% of both primary spheres and secondary expanded clones, derived from the primary spheres, contained all three cell types. The increase in frequency of EGF-generated spheres, from 1% in primary culture to close to 20% in secondary culture, and the large number of clonally derived secondary spheres that could be generated from a single primary sphere indicate that EGF induces both renewal and expansion of the precursor cell itself. In population studies, the EGF-responsive cells were carried through 10 passages, resulting in a 107-fold increase in cell number, without losing their proliferative and multilineage potential. Thus, this study describes the first demonstration, through clonal and population analysesin vitro,of a mammalian CNS stem cell that proliferates in response to an identified growth factor (EGF) and produces the three principal cell types of the CNS
Involvement of KCaChannels and Stretch-Activated Channels in Calcium Influx, Triggering Membrane Fusion of Chick Embryonic Myoblasts

AbstractCalcium influx is known to be prerequisite for membrane fusion of myoblasts. However, little is known about the channels that are responsible for the entry of calcium into the cells. Here we show that KCachannels and stretch-activated channels are involved in the calcium influx. Upon analysis of single-channel recordings, calcium sensitivity of KCachannels in myoblasts was found to be about sixfold higher than that in myotubes. Their density in myoblasts (1.68 μm−2) was also about sixfold higher than that in myotubes (0.27 μm−2). In addition, the opening of the calcium-permeable cationic channels in myoblasts was found to increase with membrane stretching and could be blocked by gadolinium. The density of stretch-activated channels was 0.22 μm−2for myoblasts, and the relative permeability of calcium to potassium wasPCa/PK≅ 3.6. The channels could generate inward calcium currents to open KCachannels in physiological solution. Furthermore, the activation of KCachannels by phloretin dramatically hyperpolarized the resting membrane potential of myoblasts and this effect could be reversed upon treatment of tetraethylammonium. While phloretin induced precocious fusion, tetraethylammonium or gadolinium blocked not only the phloretin-induced precocious fusion but also the spontaneous fusion of myoblasts. These results suggest that hyperpolarization generated by reciprocal activation of stretch-activated channels and KCachannels is involved in the calcium influx that triggers myoblast fusion
Cell Fates in the Adult Abdomen ofDrosophilaAre Determined bywinglessduring Pupal Development

Abstractwinglessactivity is required for the patterning of tergites and sternites in the adult abdomen ofDrosophila melanogaster.In the absence ofwg,tergite and sternite cuticular differentiation is replaced by that of pleura. Temperature shift analysis of awgtemperature-sensitive allele has shown that sensory bristles and tergite/sternite histotype are determined independently and thatwgis required between 15 and 20 hr after pupariation for bristle formation. The determination of sensory mother cells at this stage of development was confirmed by expression of theneuralizedgene in a subset of the proliferating histoblasts. Ectopic expression ofwgleads to the appearance of ectopic bristles and expanded tergite and sternite, indicating thatwgexpression is sufficient to promote both bristle formation and tergite/sternite differentiation.wgis expressed in the dividing and spreading histoblast population in a restricted pattern which may determine the spatial arrangement of cuticular elements
The Function of theDrosophila argosGene Product in the Development of Embryonic Chordotonal Organs

AbstractWe characterized the embryonic expression pattern and mutant phenotypes of theDrosophilageneargos,which encodes a secreted protein with an epidermal growth factor motif. Theargosnull mutation caused an increase in chordotonal (Ch) organs in both the thoracic and the abdominal segments, whereas overexpression of theargosgene resulted in a decrease in these organs. We showed that theargostranscripts are expressed transiently in the cells surrounding the Ch organ precursor and that the generhomboid(rho), which is involved in the regulation of the number of Ch organs, acts epistatically toargosin this event. Our findings suggest thatargosplays a role in Ch organ precursor formation and regulates the final number of Ch organs
A Role for an Inhibitory Connexin in Testis?

AbstractFunctional expression of gap junction proteins can be obtained conveniently with the paired oocyte cell–cell channel assay. So far all gap junction proteins (connexins), with the exception of one, have been found to make functional channels either by themselves or as hybrid channels (two hemichannels of different connexin composition). Connexin33 (cx33) appears not to follow this rule. Expression of cx33 in oocytes does not yield functional channels, and attempts to identify another connexin with which cx33 can form hybrid channels have failed so far. The observation was made that cx33 inhibits functional expression of other connexins in a connexin-specific way. While expression of cx32 remains unaffected by coinjection into oocytes of cx33 mRNA together with cx32 mRNA, junctional conductance obtained with cx43 is marginally reduced whereas coinjection of cx33 mRNA at equimolar concentrations almost completely abolishes functional cx37 expression. The fact that testis is the only tissue found to express significant levels of cx33 mRNA together with cx37 and cx43 suggests a possible functional role for an inhibitory connexin. A model is proposed where cx33 limits a cell's capability to make functional channels by allowing formation of heterotypic channels with other cells while formation of homotypic channels is disallowed. Such a mechanism would permit asynchronous maturation of germ cells while at the same time allowing communication between germ cells and Sertoli cells
Endoderm Differentiationin VitroIdentifies a Transitional Period for Endoderm Ontogeny in the Sea Urchin Embryo

AbstractThe vegetal plate of the sea urchin embryo is specified during early cleavage divisions of the embryo as shown by the classical experiments of Horstadius (reviewed in “Experimental Embryology of Echinoderms,” 1973, Clarendon, Oxford). Not until gastrulation, though, do the cells within this territory differentiate into their characteristic cell types. Vegetal plate descendents comprise the coelomic epithelium, circumesophageal muscle, basal cells, pigment cells, and endodermal epithelium. We report here that cells of the endodermal lineage acquire the ability to differentiate autonomously several hours prior to gastrulation, between the late blastula and early mesenchyme blastula stages. Cells dissociated from whole embryos after the late blastula stage have the ability to differentiatein vitro,independent of cell contacts and of the embryonic environment. In contrast, preendoderm cells removed from the embryo prior to the late blastula stage show no ability to differentiate when culturedin vitroeven though cells of other lineages, e.g., ectoderm and skeletogenic mesenchyme, show morphological and molecular differentiation in these same cultures. We have used the expression of the endoderm-specific gene products Endo 1 and LvN1.2, detected by RNase protection assays and byin situimmunolabeling, to quantify endoderm differentiation independent of embryonic or cellular morphology. These studies define a transitional period in the ontogeny of the endoderm, from cells reliant on interactions to promote fate specification and organization of territories to later events involved in morphogenesis that result from cell-type-specific gene expression
Formation and Early Morphogenesis of Endocardial Endothelial Precursor Cells and the Role of Endoderm

AbstractThe formation of endocardial endothelium in quail embryos was investigated usingin vivoandin vitrosystems. Based on the expression of an quail endothelial marker, QH-1, the initial emergence of endothelial precursor cells in the embryo occurs at stage 7+(two somites) in the posterior parts of the bilateral heart forming regions. Cells that expressed the QH-1 antigen were mesenchymal and positioned between the mesodermal epithelium of the heart region and the endoderm. By confocal microscopy, an asymmetrical distribution of QH-1 positive cells was observed between the two heart regions: specifically between 7+and 8−, more precursor cells were seen in the right region than the left. Endothelial precursor cells did not appear outside of the heart forming regions until stage 8−(three somites). Free, mesenchymal-like endothelial precursor cells intrinsic to the heart regions also expressed two extracellular antigens, JB3, a fibrillin-like protein, and cytotactin, both associated with segments of the primary heart tube where endothelial cells “re-transform” back to a mesenchymal phenotype during cardiac cushion tissue formation. Between stages 8 and 9 (four to seven somites), (1) QH-1 positive cells within the heart forming region established vascular-like connections with QH-1 positive cells located outside of the heart region, as initially shown by Coffin and Poole (1988), (2) after fusion of the heart regions, a plexus of QH-1 positive cells was formed ventral to the foregut, and (3) the definitive endocardial lining of the primary heart tube formed directly from the ventral plexus of endothelial precursor cells. Because the QH-1 positive, endothelial precursor cells of each heart forming region were always in close association with anterior endoderm, we sought to determine if the endoderm mediated the formation of precursor cells committed to a cardiac endothelial lineage as reflected by their expression of QH-1, JB3 antigen, and cytotactin. To test this hypothesis, precardiac mesodermal explants were isolated from stage 5 heart forming regions prior to their expressing of either endocardial or myocardial markers and cultured on the surface of collagen gels in the presence or absence of endoderm. In the absence of endoderm, precardiac mesoderm of each stage 5 explant remained epithelial, formed contractile tissue, but did not exhibit any QH-1 positive cells or mesenchymal cells. Conversely, when cocultured with endoderm or endoderm conditioned medium, in addition to the formation of contractile tissue, the explant formed mesenchymal cells. The latter invaded the gel lattice and, asin vivo,expressed QH-1 antigen, JB3 antigen, and cytotactin. These findings suggest that endoderm induces mesoderm of the heart fields to undergo an epithelial to mesenchyme transformation that results in the segregation of myocardial and endocardial precursor cells
Satellite Cell Proliferative Compartments in Growing Skeletal Muscles

AbstractThe cell cycle time of satellite cells in growing rats was determined to be approximately 32 hr, with an S-phase of 14 hr. The estimated cycle time was the same for satellite cells in both oxidative soleus and glycolytic EDL muscles and is consistent with the rate at which myonuclei are produced during growth. Continuous infusion of bromodeoxyuridine (BrdU) was used to determine if all satellite cells had the same cycle timein vivo.Approximately 80% of the satellite cell population was readily labeled over the first 5 days of continuous infusion. Remaining satellite cells accumulated label at a much slower rate and were still not completely saturated after an additional 9 days of infusion. Only a small portion of the cells labeled with BrdU during the first 5 days could be labeled with a second label ([3H]thymidine) during tandem continuous infusion experiments, suggesting that they pass through a limited number of mitotic divisions prior to fusion. These results suggest that satellite cells in growing oxidative and glycolytic skeletal muscles can be subdivided into two distinct compartments. About 80% divide with a 32-hr cell cycle duration and are responsible chiefly for providing myonuclei to growing fibers. The remaining 20% of the cells divide more slowly, probably because the cells enter a G0-phase between mitotic divisions. These reserve cells, through asymmetric divisions, may generate the myonuclei-producing satellite cell population. Proliferative potential for regeneration and adaptive responses is likely located in this reserve population
Inductive Processes Leading to Inner Ear Formation duringXenopusDevelopment

AbstractThis study examines the spatial and temporal attributes of inner ear induction inXenopusembryos. These results are compared to recent experiments concerning lens induction to assess whether head sensory structures share common ontogenetic features. Ectoderm from different regions and stages was transplanted to the presumptive ear region of hosts of either early (neural plate) or late (neural tube) stages. Explants of the presumptive ear ectoderm were also taken from embryos at these stages to establish the time of otic ectoderm specification. We find that ectodermal competence for otic vesicle formation extends through neural plate stages, far longer than for lens formation. Otic vesicle specification occurs substantially earlier, at neural plate stages, than lens specification. Competent ectoderm forms otic vesicles in a high fraction of cases when exposed to the ear-inducing environment of either neural plate stages or neural tube stages, a result which contrasts with lens induction where the neural tube stage embryo provides a much weaker inducing environment than earlier stages. Otic vesicles induced in neural tube stage hosts are primarily in contact with presumptive hindbrain, suggesting that this neural tissue may be sufficient for otic vesicle induction. These studies reveal overall similarities between lens and inner ear induction, but sufficient differences to propose that some facets of determination of these sensory tissues may occur by independent mechanisms and not via a common developmental state
Induction of Axial Mesoderm by zDVR-1, the Zebrafish Orthologue ofXenopusVg1

AbstractThe zebrafish DVR-1 (zDVR-1) gene, likeXenopusVg1, is present maternally as an unprocessed precursor protein which is distributed ubiquitously along the future dorsoventral axis. Also, like Vg1, overexpression of zDVR-1 in zebrafish directs synthesis of more precursor, but no processed protein. However, the native zDVR-1 precursor is processed to mature protein when expressed inXenopus.Like processed Vg1, mature zDVR-1 is a potent inducer of axial mesoderm. The parallels in expression pattern, apparent regulation of protein processing, and mesoderm-inducing activity support the hypothesis that localized protein processing controls production of a dorsal mesoderm inducer in these two species. Furthermore, using mutant mRNAs, we show that cleavage site sequences of the precursor protein are important in regulating protein processing
Avian Olfactory Receptors: Differentiation of Olfactory Neurons under Normal and Experimental Conditions

AbstractThe bird olfactory system has a simple structure and affords an attractive developmental model for the study of olfactory morphogenesis and differentiation. We have cloned and characterized several chick olfactory receptor (COR) genes belonging to the superfamily of seven-transmembrane domain proteins.In situhybridization analysis of their spatiotemporal patterns of expression during development reveals several important characteristics.CORexpression starts early in placodal cells (Embryonic Day 5, E5). Changes in their expression pattern then correlate with the onset of synaptogenesis (E8). The adult pattern, achieved before hatching, shows that cells expressing a particularCORare not regionalized within the epithelium. By double-labelin situhybridization, we clearly demonstrate that a single cell does not coexpress differentCORgenes (or subsets ofCORs) at any stage of development. Following bulbar deafferentation,CORexpression ceases more rapidly than expected from previous axotomy experiments. Concomitantly, a reactivation of theCash-1gene, which is involved in early neuronal specification, could be an early sign of olfactory neuronal regeneration. Modulation ofCORandCash-1expression points to a simultaneous process of neuronal degeneration and regeneration in the olfactory epithelium after axotomy.CORexpression is restricted to the olfactory epithelium except during early stages (before synaptogenesis). At that time, cells distributed along the olfactory nerve, from the placode to the anterior telencephalon, also expressCORs. This cell population is different from the luteinizing hormone releasing hormone neurons migrating from the placode. Our results show that the olfactory neurons or neuroblasts choose to express oneCORbefore establishing functional connections with the bulb. Later on, bulboepithelial connections seem important not only for olfactory neuron survival but also for stimulation ofCORexpression. In addition, beyond their implication in functional odor detection, CORs could be involved, at early stages, in processes of olfactory morphogenesis, including the establishment of a bulbar chemotopy
Isolation and Characterization of Two Novel, Cytoplasmically Polyadenylated, Oocyte-Specific, Mouse Maternal RNAs

AbstractDuring early development in mouse andXenopus,translational activation of stored maternal mRNAs by cytoplasmic polyadenylation requires both the nuclear polyadenylation signal AAUAAA and U-richcis-acting adenylation control elements (ACEs), also termed cytoplasmic polyadenylation elements, located in the 3′ UTR. Using an ACE-based PCR strategy (Salléset al.,1992) we have isolated two novel cDNAs from mouse oocytes: OM2a and OM2b (for Oocyte Maturation). Each message contains an ACE consensus sequence upstream of AAUAAA, is specifically transcribed in the growing oocyte, and is cytoplasmically polyadenylated upon oocyte maturation. Comparison of the mouse and rat homologs reveals considerable nucleotide sequence homology and conservation of overall gene organization. However, the predicted open reading frames are far less conserved, suggesting that these genes may not be functioning as proteins. The tissue specificity and tight temporal regulation of the RNAs suggest a role for these genes during early development
The PH-20 Protein in Cynomolgus Macaque Spermatozoa: Identification of Two Different Forms Exhibiting Hyaluronidase Activity

AbstractIn these experiments, we have characterized the bifunctional sperm protein PH-20 in macaque sperm and studied its hyaluronidase activity. Intact sperm were evaluated before the acrosome reaction (AR), and a soluble form of PH-20 released during acrosomal exocytosis was also investigated. Western blots of SDS–PAGE of acrosome-intact sperm extracts revealed a 64-kDa form of PH-20 was recognized by a polyclonal antibody (R-10) raised in rabbits against purified, recombinant cynomolgus macaque sperm PH-20. The soluble components released during the AR which were recognized by the R-10 antibody included both the 64-kDa form and a 53-kDa form of PH-20. An ELISA-like procedure for determining PH-20 hyaluronidase activity indicated that acrosome-intact sperm exhibited two peaks of hyaluronidase activity near pH 4 and ≥pH 7. The majority of enzyme activity in acrosome-intact sperm extracts occurred at neutral pH, while the soluble hyaluronidase activity released at the AR was predominantly acid-active. Hyaluronidase activity of PH-20 at different pH optima was investigated using hyaluronic acid substrate gel electrophoresis, and results indicated that the 64-kDa polypeptide had a broad range, with the majority of activity at neutral pH (pH 7). The 53-kDa polypeptide in sperm extracts only exhibited activity at acid pH (pH 4). The hyaluronidase activities of both enzymes could be inhibited by apigenin. The soluble PH-20 hyaluronidase activity released during the AR was primarily of the acid-active 53-kDa form. Fine structural localization of PH-20 using Fab fragments of R-10 IgG demonstrated that PH-20 was associated not only with sperm membranes, but also with the dispersing acrosomal contents. These data suggest that the more neutral-active form of PH-20 (64 kDa) is present on the plasma and inner acrosomal membranes and gives rise to the soluble acid-active form at the time of the AR. The generation of the soluble form of PH-20 may result from the action of acrosomal enzymes, which could include proteases, glycosidases, and phospholipases
Dynamic Interactions between Nerve and Muscle inCaenorhabditis elegans

AbstractSynaptogenesis among developing motoneurons and muscles was examined in the nematodeCaenorhabditis elegans.In this animal embryonic precursor cells give rise to regionally localized, contiguous clones of muscle cells that form two dorsal and two ventral sets that run longitudinally along the body wall. Ablation of selected embryonic muscle precursors resulted in gaps in the posterior dorsal muscle quadrants. We compared the morphological development of GABAergic locomotory neurons in the presence and absence of their target muscle cells. The results led to four main conclusions: (1) target muscle cells are not required for the morphological differentiation of the motoneurons; (2) target muscle cells appear to be required for the formation of presynaptic varicosities by the motoneurons; (3) embryonic muscle cells serve as a guide for migrating postembryonic muscle cells and in the absence of these guides the postembryonic muscles often assume ectopic locations; and (4) in the presence of ectopic muscle cells, the GABAergic locomotory neurons sprouted and formed branches that contributed to ectopic neuromuscular junctions