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M Solursh

Publications and source records attributed to M Solursh.

At least 37 records · Page 2Linked to original sources
PubMed1994

A concentration gradient of retinoids in the early Xenopus laevis embryo.

Previous studies have postulated that Xenopus embryos contain an endogenous retinoic acid (RA) concentration gradient from posterior to anterior during the process of primary axis formation, since RA is able to alter profoundly primary axis formation in Xenopus embryos, to increase the expression of some posterior markers, and to inhibit the expression of some anterior markers, including homeobox-containing genes. Here, we provide direct evidence for this hypothesis. By using a reporter cell system, we demonstrate that the endogenous biologically active retinoid concentration in whole Xenopus embryos increases 3-fold from the two-cell stage to the neurula stage, and that the active retinoid concentration in the dorsal marginal zone, a region wherein the Spemann's organizer is located, increases about 5-fold from the early gastrula to late gastrula stages, suggesting the developmental regulation of the retinoid levels. In the early neurula stage (stage 13-14), endogenous active retinoids are present in a concentration gradient with the highest level at the posterior end, about 10-fold higher than that at the anterior end, of the embryo. This concentration gradient may be established during gastrulation and may provide positional cues for primary axis formation.

Animals↗
PubMed1994

Characterization of the homeobox-containing gene GH6 identifies novel regions of homeobox gene expression in the developing chick embryo.

Homeobox genes are a major group of genes involved in regulating, embryogenesis. Here we describe the identification of GH6, a novel chicken homeobox-containing gene and its spatial and temporal expression pattern in the developing chick embryo. Identity comparisons of the GH6 homeodomain suggest that it is closely related to the human homeobox gene H6, with 93% amino acid conservation. Temporally, GH6 expression is highest between embryonic stages 23 and 26; however, some expression is also detectable as early as stage 13. In situ hybridization of stage 23 embryos indicates that GH6 expression occurs at high levels in discrete craniofacial regions including the second branchial arch, the neural retina, the lens epithelium, the optic nerve, and the infundibulum. GH6 expression was also seen in the developing ventricular myocardium, representing the first report of homeobox gene expression in the developing ventricle. GH6 is also expressed in sensory spinal and cranial ganglia, suggesting that GH6 plays several roles not only in the development of craniofacial structures such as the eye and ear, but also in formation of functionally defined ganglia and myocardial structures.

Amino Acid Sequence↗
PubMed1994

Role for short-range interactions in the formation of cartilage and muscle masses in transfilter micromass cultures.

In the embryonic limb bud, chondrogenic and myogenic regions arise by segregation from a mixture of chondrogenic and myogenic precursor cells (Schramm and Solursh, 1990). In in vitro micromass cultures, dissociated limb bud cells also segregate into chondrogenic and myogenic tissues. The process of segregation was studied using transfilter micromass cultures to determine the role of short-range interactions in the formation of these two tissue masses. Limb bud cells were plated on both sides of large and small Nucleopore filters. Pore size was chosen to permit cell-cell or cell-extracellular matrix contact across large pore filters but permit only interactions via diffusible molecules across small pore filters. Cultures were plated at high density on one surface to allow formation of chondrogenic nodules and at high or low density on the opposing surface to observe any segregation effect on chondrogenic and myogenic cells, respectively. Spatially organized extracellular matrix of micromass cultures was fixed by cold ethanol precipitation onto filters. The fixed micromass cultures lost the ability to affect segregation across the filter. These results suggest that chondrogenic aggregates enlarge in an autocrine manner dependent on direct cell-cell or cell-extracellular matrix contact provided by living cells. Myogenic segregation likely occurs in a paracrine manner that also requires short-range interactions.

Animals↗
PubMed1994

rDlx, a novel distal-less-like homeoprotein is expressed in developing cartilages and discrete neuronal tissues.

From a rat chondrosarcoma we isolated a cDNA that encodes a novel homeoprotein rDlx. The homeodomain of rDlx shows a high degree of sequence identity with those of Drosophila Distal-less, mouse Dlx, and Xenopus Xdll proteins. Northern hybridization of rDlx revealed a 1.4- to 1.6-kb RNA species in a rat chondrosarcoma and a cell line derived from this tumor and in mouse C3H10T1/2 cells, but no rDlx RNA was detected in mouse NIH3T3 fibroblasts, rat skin fibroblasts, mouse C2 myoblasts, mouse myeloma S194 cells, human B-cell lymphoma Daudi cells, or human acute myelocytic leukemia cells. RNase protection assays showed that rDlx transcripts were present at high levels in 14-day-old rat embryos, 18-day-old rat embryo skeletal tissues, and adult rat brain. rDlx RNAs were present at lower levels in newborn rat rib cartilage, 18-day-old rat embryo soft tissues, newborn rat skin, and adult rat heart. rDlx transcripts were not detected in adult rat liver, spleen, lung, kidney, testis, or skeletal muscle. In situ hybridization of rat embryos at different stages revealed that rDlx transcripts were present in otic vesicle, branchial arches, apical ectodermal ridge of limb bud, developing cartilages, perichondria of mature cartilages, mesenchymal cells of developing membranous bones, developing teeth, ganglionic eminence of the telencephalon, diencephalon, olfactory epithelia, and epidermis of the skin. rDlx RNAs were also detected in the developing parasympathetic mesenteric ganglia of the gastrointestinal tract. Hence, rDlx RNAs are mainly expressed in several neuronal tissues and developing skeletal tissues.

Amino Acid Sequence↗
PubMed1994

Hyaluronate degradation affects ventricular function of the early postlooped embryonic rat heart in situ.

Hyaluronic acid is the major glycosaminoglycan of the early cardiac extracellular matrix or "cardiac jelly," yet little is known about its role in the ontogeny of early ventricular performance. To investigate the in situ effect of hyaluronate degradation on ventricular function, whole rat embryos were cultured in rat serum alone (control embryos) or rat serum plus 20 TRU/mL of Streptomyces hyaluronidase (treatment embryos) from gestational day 9.5 (before formation of the heart tube) through initial looping of the heart. Cardiac function was measured before looping (24 hours in culture) and immediately after looping (36 hours in culture) by video motion analysis of the external wall motion of the bulbus cordis and primitive ventricle. Degradation of hyaluronic acid in the treated embryos was confirmed by Alcian blue staining at pH 2.5. Significant increases in heart rate, circumferential shortening fraction, maximum velocity of circumferential contraction, and maximum velocity of circumferential relaxation were observed with looping in both control and treatment embryos. Although there was minimal difference in ventricular performance between control and treatment embryos before looping, there was a significant increase in all parameters of ventricular performance in the hyaluronidase-treated embryos immediately after looping of the heart. Endocardial cushions were absent in hyaluronidase-treated embryos, and an additional group of embryos cultured in the presence of Streptomyces hyaluronidase for 48 to 72 hours failed to develop endocardial cushions. These experiments are the first to (1) document a quantifiable increase in ventricular performance during early cardiac looping and (2) demonstrate that hyaluronate degradation results in abnormal endocardial cushion formation and altered ventricular performance of the postlooped heart.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Bone cell expression on titanium surfaces is altered by sterilization treatments.

Phenotypic responses of rat calvarial osteoblast-like cells (RCOB) were evaluated on commercially pure titanium (cpTi) surfaces when cultured at high density (5100 cells/mm2). These surfaces were prepared to three different clinically relevant surface preparations (1-micron, 600-grit, and 50-microns-grit sand-blast), followed by sterilization with either ultraviolet light, ethylene oxide, argon plasma-cleaning, or routine clinical autoclaving. Osteocalcin and alkaline phosphatase, but not collagen expression, were significantly affected by surface roughness when these surfaces were altered by argon plasma-cleaning. In general, plasma-cleaned cpTi surfaces demonstrated an inverse relationship between surface roughness and phenotypic markers for a bone-like response. On a per-cell basis, levels of the bone-specific protein, osteocalcin, and the enzymatic activity of alkaline phosphatase were highest on the smooth 1-micron polished surface and lowest on the roughest surfaces for the plasma-cleaned cpTi. Detectable bone cell expression can be altered by clinically relevant surfaces prepared by standard dental implant preparation techniques.

Alkaline Phosphatase↗
PubMed1994

Elastin exhibits a distinctive temporal and spatial pattern of distribution in the developing chick limb in association with the establishment of the cartilaginous skeleton.

In this work we have analyzed the presence of elastic components in the extracellular matrices of the developing chick leg bud. The distributions of elastin and fibrillin were studied immunohistochemically in whole-mount preparations using confocal laser microscopy. The association of these constituents of the elastic matrix with other components of the extracellular matrix was also studied, using several additional antibodies. Our results reveal the transient presence of an elastin-rich scaffold of extracellular matrix fibrillar material in association with the establishment of the cartilaginous skeleton of the leg bud. The scaffold consisted of elastin-positive fibers extending from the ectodermal surface of the limb to the central cartilage-forming regions and between adjacent cartilages. Fibrillin immunolabeling was negative in this fibrillar scaffold while other components of the extracellular matrix including: tenascin, laminin and collagens type I, type III and type VI; appeared codistributed with elastin in some regions of the scaffold. Progressive changes in the spatial pattern of distribution of the elastin-positive scaffold were detected in explant cultures in which one expects a modification in the mechanical stresses of the tissues related to growth. A scaffold of elastin comparable to that found in vivo was also observed in high-density micromass cultures of isolated limb mesodermal cells. In this case the elastic fibers are observed filling the spaces located between the cartilaginous nodules. The fibers become reoriented and attach to the ectodermal basal surface when an ectodermal fragment is located at the top of the growing micromass. Our results suggest that the formation of the cartilaginous skeleton of the limb involves the segregation of the undifferentiated limb mesenchyme into chondrogenic and elastogenic cell lineages. Further, a role for the elastic fiber scaffold in coordinating the size and the spatial location of the cartilaginous skeletal elements within the limb bud is also suggested from our observations.

Animals↗
PubMed1994

Craniofacial morphogenesis workshop report.

The following report highlights the discussions and interaction at the workshop on craniofacial morphogenesis, sponsored by The Human Frontier Science Program, held in April 1993 at the University of Iowa. A brief summary of selected sessions is included to exemplify the benefits of bringing together individuals from various disciplines and backgrounds in order to establish a unified theory of craniofacial morphogenesis. The synthesis of information and experience of a wide range of approaches made the 4-day period an invaluable experience for the participants from nine different countries.

Cleft Lip↗
PubMed1994

Characterization of the human MSX-1 promoter and an enhancer responsible for retinoic acid induction.

Previous studies have shown that the expression of some human HOX genes can be induced by retinoic acid (RA) in cultured embryonal carcinoma (EC) cells. However, the mechanisms for the regulation of HOX gene expression by RA are still unclear. We have examined the effects of RA on the human MSX-1 (formerly named HOX-7) gene expression in cultured EC cells (NT2/D1). Furthermore, we have cloned and characterized the human MSX-1 promoter and analyzed the activities of the promoter in response to RA. Our results demonstrate that transcription of human MSX-1 is activated by RA in cultured EC cells. This activation is dose and time responsive. The MSX-1 promoter was shown to be TATA-box independent and able to promote transcription in RA-treated EC cells. DNase-I footprinting studies revealed protection of several GAGA factor binding sites and an NF-kappa B site upstream to the transcription start site by nuclear extracts prepared from EC cells. A downstream sequence was differentially protected by the nuclear extract from RA treated cells. This differential binding of the sequence with the nuclear extract was further confirmed by gel shift assays. This sequence confers to a heterologous promoter with the ability to respond to RA induction. Point mutation within this DNA fragment abolished the binding of the fragment to the nuclear extract and the response of this element in a heterologous promoter to RA induction. Deletion of this enhancer element together with the adjacent NF-kappa B and GAGA sites abolished the ability of the promoter to direct transcription in RA-treated EC cells. However, removal of a downstream DNA fragment from the promoter endowed the promoter with the ability to direct transcription in RA-untreated cells. Taken together, both positive and negative regulatory cis-elements are involved in the regulation of the MSX-1 promoter and coordinate to control the gene expression.

Animals↗
PubMed1993

Cartilage homeoprotein 1, a homeoprotein selectively expressed in chondrocytes.

We identified a rat cDNA that encodes cartilage homeoprotein 1 (Cart-1). The deduced amino acid sequence of Cart-1 contains a paired-type homeodomain. Northern blot hybridization and RNase protection assay revealed that Cart-1 RNA was present at high levels in a well-differentiated rat chondrosarcoma tumor and in a cell line derived from this tumor. Cart-1 RNA was detected in primary mouse and rat chondrocytes but not in various fibroblasts including mouse 10T1/2 cells, NIH 3T3 cells, BALB 3T3 cells, and rat skin fibroblasts. It was also undetectable in mouse C2 myoblasts, S194 myeloma cells, and embryonic stem cells. Cart-1 RNA was present at a very low level in tested but was not detected in other soft tissues of 8-week-old rats. In situ hybridization of rat embryos between 14.5 and 16.5 days post coitum revealed relatively high levels of Cart-1 RNA in condensed prechondrocytic mesenchymal cells and in early chondrocytes of cartilage primordia. The levels of Cart-1 RNA were lower in mature chondrocytes. No hybridization was observed in brain, spinal cord, heart, spleen, gastrointestinal tract, liver, and muscle. We speculate that Cart-1 has a role in chondrocyte differentiation.

3T3 Cells↗
PubMed1993

Effects of the mesonephros and insulin-like growth factor I on chondrogenesis of limb explants.

The mesonephros has been shown to have a growth-promoting influence in vivo on limb outgrowth. This influence has been studied in detail using an organ culture system. The results show that in the presence of the mesonephros limb explants formed larger cartilages than cultures without mesonephros. Furthermore, with mesonephros, morphology of the cartilages is comparable to that of skeletal elements in vivo while cartilages formed in cultures lacking mesonephros were amorphous. The mesonephric influence also promoted the formation of a well-organized extracellular matrix in the cartilage while cartilage in cultures without mesonephros formed an abnormal appearing matrix. Cartilage matrices in cultures with or without mesonephros were immunoreactive to type IX and type II collagens, cartilage proteoglycan PGH, and link protein although cultures lacking mesonephros had a very restricted distribution of type IX collagen immunoreactivity. Despite the different distribution of type IX collagen, long-form-type IX collagen transcripts appeared similar in both types of culture based on in situ hybridization. The mesonephric effect on limb explants could be partially duplicated by the addition of insulin-like growth factor I (IGF-I) to cultures without mesonephros. Furthermore, the mesonephric influence on cartilage growth and morphological differentiation could be blocked by the addition of a blocking antibody to IGF-I to cultures with mesonephros. The results support the hypothesis that IGF-I is one of the growth factors produced by the mesonephros which may play a role in early limb development and chondrogenesis.

Animals↗
PubMed1993

Activity of protein kinase C during the differentiation of chick limb bud mesenchymal cells.

To investigate the relationship between protein kinase C (PKC) and chondrogenesis, PKC activity was assayed in cultures of stage 23/24 chick limb bud mesenchymal cells under various conditions. PKC activities of cytosolic and particulate fractions were low in 1 day cultured cells. As chondrogenesis proceeds, cytosolic PKC activity increased more than twofold, while that of the particulate fraction increased only slightly. Three days' treatment of cultures with phorbol-12-myristate-13-acetate (PMA, 5 x 10(-8) M) inhibited chondrogenesis judged by the accumulation of Alcian blue bound to the extracellular matrix and depressed PKC activity in cytosolic fraction. When cells were grown for 3 days in control medium after 3 days' treatment with PMA, chondrogenesis resumed and PKC activity recovered to normal values. PKC activity in cultures plated at low density (5 x 10(6) cells/ml) where chondrogenesis is reduced was as low as that in 1 day cultured cells plated at high density (2 x 10(7) cells/ml) or that in PMA treated cells. On the other hand, staurosporine promoted chondrogenesis without affecting PKC activity. Furthermore, reversal of PMA's inhibitory effect on chondrogenesis by staurosporine was not accompanied by recovery of PKC activity. These data indicate that increases in PKC activity is closely related to chondrogenesis and that PMA inhibits chondrogenesis by depressing PKC. However, staurosporine's enhancing effect on chondrogenesis is not related to PKC activity.

Alkaloids↗
PubMed1992

Identification and genetic mapping of a homeobox gene to the 4p16.1 region of human chromosome 4.

A human craniofacial cDNA library was screened with a degenerate oligonucleotide probe based on the conserved third helix of homeobox genes. From this screening, we identified a homeobox gene, H6, which shared only 57-65% amino acid identity to previously reported homeodomains. H6 was physically mapped to the 4p16.1 region by using somatic cell hybrids containing specific deletions of human chromosome 4. Linkage data from a single-stranded conformational polymorphism derived from the 3' untranslated region of the H6 cDNA placed this homeobox gene more than 20 centimorgans proximal of the previously mapped HOX7 gene on chromosome 4. Identity comparisons of the H6 homeodomain with previously reported homeodomains reveal the highest identities to be with the Nk class of homeobox genes in Drosophila melanogaster.

Amino Acid Sequence↗
PubMed1992

Retinoic acid is enriched in Hensen's node and is developmentally regulated in the early chicken embryo.

Retinoic acid (RA) has been considered as a potential morphogen in the chicken limb and has also been suggested to be involved in early embryonic development. On the basis of biological activity, previous reports suggest that Hensen's node, the anatomical equivalent in the chicken of the Spemann's organizer, may contain RA. Here, by using a molecular assay system, we demonstrate that Hensen's node contains retinoids in a concentration approximately 20 times more than that in the neighboring tissues. Furthermore, stage 6 Hensen's node contains approximately 3 times more retinoid than that of stage 4 embryos. These endogenous retinoids may establish a concentration gradient from Hensen's node to adjacent tissues and play a role in establishing the primary embryonic axis in the vertebrate. The results also suggest that the retinoid concentration in Hensen's node is developmentally regulated.

Animals↗
PubMed1992

Sea urchin collagen evolutionarily homologous to vertebrate pro-alpha 2(I) collagen.

We isolated several overlapping cDNA clones covering the 4242 nucleotides of a Strongylocentrotus purpuratus transcript that codes for a fibrillar procollagen chain. The sea urchin polypeptide includes a 124-amino acid long amino pre-propeptide, a 1064-amino acid alpha-chain inclusive of 338 uninterrupted Gly-X-Y repeats, and a 226-residue carboxyl-propeptide. The distribution of the highly conserved cysteines within the last domain together with the structural configuration of the amino-propeptide and the organization of the corresponding coding region, strongly suggest that the sea urchin gene is evolutionarily related to the vertebrate pro-alpha 2(I) collagen. This work, therefore, represents the first report of the complete primary structure of an invertebrate fibrillar procollagen chain. It also provides a new insight into the evolution of the amino-propeptide, the most divergent among the major protein domains of fibrillar procollagen chains.

Amino Acid Sequence↗
PubMed1992

Localization of type II collagen, long form alpha 1(IX) collagen, and short form alpha 1(IX) collagen transcripts in the developing chick notochord and axial skeleton.

In this study we compare, by in situ hybridization, the spatial and temporal expression patterns of transcripts of avian type II collagen and the long and short forms of the (alpha 1) chain of type IX collagen during the development of the notochord and axial skeleton. We observed type II collagen and short form type IX collagen transcripts in the developing (stage 25-28) nonchondrogenic notochord. Conversely, long form type IX transcripts were not detectable in the notochord or perinotochordal sheath. Interestingly, all three transcripts colocalized in the developing chondrogenic vertebrae of the axial skeleton as well as in the chondrocranium and Meckel's cartilage. The expression of the short form of type IX collagen in these regions was more restricted than that of the long form. This report provides additional support for a complex regulatory pathway of cartilage marker gene expression in chondrogenic vs. nonchondrogenic tissues during avian embryogenesis.

Animals↗