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M Solursh

Publications and source records attributed to M Solursh.

At least 55 records · Page 3Linked to original sources
PubMed1992

Coordinate expression of IGF-I and its receptor during limb outgrowth.

The morphogenetic mechanisms involved in shaping the embyro are largely unknown. Previous studies from this laboratory suggest that the mesonephros promotes limb outgrowth in ovo in the chicken embryo and might be involved in early limb morphogenesis, since damage to the mesonephros results in truncated limbs. In limb bud organ cultures, the presence of the mesonephros promotes cartilage formation. This effect can be reproduced by exogenous IGF-I or prevented by blocking antibody to IGF-I. In order to examine the hypothesis that mesonephros-derived IGF-I is involved in the early morphogenesis of the limb, we examined the spatial and temporal expression of IGF-I and type I receptor for IGF by in situ hybridization at stages when the onset of limb development occurs. The results show that neither transcript is detected at stage 13, prior to the appearance of the limb bud; but both transcripts are detected in the mesonephros at stage 14, an early stage in limb outgrowth. The hybridization signal in the mesonephros for both transcripts increases with development and signal was codistributed as well. At stage 18 the level of receptor transcripts detected in the flank relative to the limb decreased. Thus, the temporal and spatial patterns of expression of IGF-I and its receptor are consistent with their involvement in the initiation of limb outgrowth and support the model that localized expression of a growth factor and its receptor can be involved in shaping the embryo.

Animals↗
PubMed1992

Localization of pro-alpha 2(V) collagen transcripts in the tissues of the developing mouse embryo.

Correct assembly of fibrillar collagen networks plays a critical role in animal morphogenesis. Very little is known about the contribution of the so-called minor fibrillar collagens (types V and XI) to fibrillogenesis. Here we examined the developmental expression of the mouse pro-alpha 2(V) collagen gene (col5a2) after the cloning and sequencing of cDNAs that cover the entire length of the message. Transcripts of col5a2, detectable as early as 9 days of gestation, localize with distinct patterns in the tissues of day 12.5 and day 16.5 fetuses. The earlier developmental stage is characterized by low and diffuse col5a2 expression in the peritoneal membranes and intestinal and craniofacial mesenchymes. The later stage exhibits higher and more restricted col5a2 mRNA accumulation in primary ossified regions, perichondrium, joints, tendon, atrioventricular valve of the heart, and selected portions of the head. A parallel analysis using a cartilage-specific pro-alpha 1(II) collagen (col2a1) probe confirmed that these two collagen genes are transcribed in a mutually exclusive manner during mouse embryogenesis. On the other hand, the developmental pattern of col5a2 expression closely resembles that of the type I collagen, thus further substantiating the notion that these macromolecules cooperate in the formation of fibrillar networks in non-cartilaginous matrices.

3T3 Cells↗
PubMed1992

Comparison of Hensen's node and retinoic acid in secondary axis induction in the early chick embryo.

Retinoic acid (RA) and Hensen's node, the organizer center in the chick embryo, have been shown to have polarizing activity when applied or grafted into the chick limb bud. Here we investigate and compare the effects of RA and grafted Hensen's node on the early chick embryo. Anion exchange beads soaked with RA at concentrations ranging from 5 to 100 ng/ml and implanted on the anterior side or on the left side of the host anteroposterior axis of a stage 4 chick embryo in ovo have the ability to induce secondary axis formation, while beads soaked with RA of the same concentration and implanted on the right side or on the posterior side of the host axis are unable to induce the secondary axis. All of the induced axes contain trunk-tail structures. Hensen's node from quail embryos implanted into the early chick blastoderm could also cause the formation of secondary axes in addition to self-differentiation of the graft into a secondary axis. Both RA and grafted Hensen's node caused the inhibition of forebrain development with an increase in hindbrain development and the host heart to loop in an abnormal direction. The results support the hypothesis that Hensen's node is a source of RA which is involved in early embryogenesis. Alternatively, RA might stimulate the formation of Hensen's nodal properties in adjacent tissue.

Animals↗
PubMed1992

Cellular contribution of the different regions of the somatopleure to the developing limb.

Regionalization of the presumptive limb region was examined before and at the onset of limb development by means of a variety of transplantation experiments between quail and chick embryos in ovo. The results demonstrate a two-step process, the first of which is the designation of the region of the somatopleure that would become part of the limb, followed by specification of dorsal and ventral regions of the limb. The medial half of the somatic mesoderm is the region which gives rise to the limb with only a smaller cellular contribution from the lateral half of the somatic mesoderm. The cellular contribution of the medial region of the somatopleure appeared to determine the type of limb formed (i.e., wing or leg). The second process relates to changes in the ability of the somatic ectoderm to undergo extensive lateral displacement with development. Starting at stage 14, the medial and lateral somatic ectoderms maintain their position after transplantation, in contrast to earlier stage limb or flank ectoderms which undergo extensive lateral displacement with development. The positional determination of the dorsal and ventral properties of the medial and lateral ectoderms of the prospective limb region and their distal displacement during limb outgrowth may be important morphogenetic events in limb development.

Animals↗
PubMed1992

Myogenic potential of chick limb bud mesenchyme in micromass culture.

The myogenic potential of chick limb mesenchyme from stages 18-25 was assessed by micromass culture under conditions conductive to myogenesis, and was measured as the proportion of differentiated (muscle myosin-positive) mononucleated cells detected. It was found that similar myogenic potentials existed in mesenchyme from whole limbs between stages 18 and 19, but this potential was halved by stage 20. At stage 21, proximal mesenchyme showed significantly more myogenesis than distal mesenchyme, but this difference was abolished by stage 22. Thereafter, myogenesis was increasingly restricted from the distal mesenchyme, whilst the potential in more proximal regions did not significantly increase after stage 23. When the ratio between total limb myoblasts which differentiated on days 1 and 4 of culture was analysed, it was found that two distinct peaks existed at stages 20 and 23. The significance of these ratio peaks is unclear, but may be related to different proliferative potentials of the pre-myoblasts at these stages.

Animals↗
PubMed1992

Localization of HstI transcripts to the apical ectodermal ridge in the mouse embryo.

The HstI gene is a transforming gene, coding for a protein of the fibroblast growth factor family (Sakamoto et al., 1986). Previous RNA hybridization studies with the mouse homolog demonstrated the presence of a 3.0-kb transcript in Day 11 and 14 mouse embryos. Here we detect a 3.0-kb transcript in the limb and body of the dissected Day 11 mouse embryo. PCR amplification using HstI-specific primers also showed comparable results. In order to localize the HstI transcripts during development, corresponding HstI cDNA was isolated, and an HstI-specific region was used as a probe for in situ hybridization analysis. Serial sections of embryos from Day 8 (early-somite stages) through Days 9, 10, 11, and 12 of gestation were examined. With the antisense probe, a signal was detected in the Day 11 and 12 embryo, where it was localized to the apical ectodermal ridge (AER) of the limb bud. This structure is well known for its role in promoting the distal outgrowth of the developing limb bud. Signal was detected in both fore- and hindlimbs during the period of rapid distal growth. This restricted localization suggests a role for HstI in normal embryogenesis, including outgrowth of the limb bud.

Animals↗
PubMed1992

A growth-promoting influence from the mesonephros during limb outgrowth.

It has been suggested that the mesonephros has a role in normal limb development. This hypothesis was directly tested by removing the mesonephros adjacent to the presumptive limb region of stage 12-18 chick embryos using microsurgery or laser ablation. The experimental manipulation resulted in reduced limb outgrowth on the operated side. The poor limb outgrowth was correlated with either the lack of or the presence of a rudimentary mesonephros on the operated side. Furthermore, the presence of nephric tissue in limb bud organ culture enhanced growth and morphological differentiation of cartilage formed in culture. In vivo, the influence of the mesonephros resulted in significantly higher cell proliferation in the adjoining medial half of the limb mesoderm compared with the lateral half. The removal of the mesonephros adjoining the prospective limb region reduced the number of dividing cells in the medial mesoderm. The higher proliferation in the medial limb mesoderm is significant to limb outgrowth since grafting experiments showed that most of the cells that form the limb are derived from the medial mesoderm. The results suggest that the influence from the mesonephros may provide some signal for limb outgrowth.

Animals↗
PubMed1992

Characterization of the human HOX 7 cDNA and identification of polymorphic markers.

cDNA clones for a human HOX 7 gene obtained with homologous clones of Drosophila were used in human gene mapping studies. The human cDNA clone was isolated from a library constructed from human embryonic craniofacial material. The sequence of the cDNA demonstrates significant homology with mouse HOX 7. A search for RFLPs identified MboII and BstEII variants. A CA dinucleotide repeat with 5 alleles was also identified and allowed placement of HOX 7 into a defined linkage map. Evidence for linkage disequilibrium was found with markers tested. These results place the human HOX 7 gene in a defined position on 4p.

Amino Acid Sequence↗
PubMed1992

Differential co-expression of long and short form type IX collagen transcripts during avian limb chondrogenesis in ovo.

Using RNA blot analysis of developmentally staged avian limb buds, we demonstrate that transcripts of several cartilage marker genes appear in limb tissue prior to overt chondrogenesis. Type II collagen mRNA, cartilage proteoglycan core protein mRNA, alpha 2(IX) collagen mRNA, and transcripts of the short form alpha 1(IX) collagen chain derived from the downstream promoter are co-expressed in limb tissue approximately 24-36 hours before the appearance of the respective polypeptides in differentiating cartilagenous tissue. Transcripts of the long form alpha 1(IX) collagen chain derived from the upstream promoter appear somewhat later in development; nearly coincident with the immunolocalization of type IX collagen in the cartilage elements of the limb. The spatial distribution of type II and type IX collagen transcripts was analyzed by in situ hybridization. Type II collagen and the long form alpha 1(IX) collagen transcripts co-localized in the chondrogenic elements of the developing forelimb. In contrast, short form alpha 1(IX) collagen transcripts which lack the 5' region encoding the NC4 globular amino-terminal domain were distributed throughout the non-chondrogenic, non-myogenic mesenchymal regions of the limb and were not detectable above background levels in the limb chondrogenic elements. The precocious appearance of several cartilage marker gene transcripts prior to chondrogenesis suggests that multiple levels of gene regulation including alternative promoter use, alternative RNA splicing, alternative polyadenylation, and other post-transcriptional as well as translational mechanisms are active prior to, and during avian limb chondrogenesis.

Animals↗
PubMed1991

Formation of cartilage tissue in vitro.

Articular cartilage is notoriously defective in its capacity for self-repair, making joints particularly sensitive to degenerative processes. However, methods are now available for the preparation of large numbers of differentiated chondrocytes from a small biopsy sample from any patient. The cells are amplified by proliferation as fibroblast-like cells that will re-express the cartilage phenotype when placed in suspension or gel culture. The chondrocytes can be collected from gel cultures after agarase treatment and reconstituted into cartilage tissue in pellet cultures. In addition, these chondrocytes can be suspended in an appropriate delivery vehicle and implanted into defect sites with a high reparative success rate in an animal model. Appropriate procedures can now be tested in appropriate patient populations.

Animals↗
PubMed1991

Primary mesenchyme cell migration requires a chondroitin sulfate/dermatan sulfate proteoglycan.

Primary mesenchyme cell migration in the sea urchin embryo is inhibited by sulfate deprivation and exposure to exogenous beta-D-xylosides, two treatments known to disrupt proteoglycan synthesis. We show that in the developing sea urchin, exogenous xyloside affects the synthesis by the primary mesenchyme cells of a very large, cell surface chondroitin sulfate/dermatan sulfate proteoglycan. This proteoglycan is present in a partially purified fraction that restores migratory ability to defective cells in vitro. The integrity of this chondroitin sulfate/dermatan sulfate proteoglycan appears essential for primary mesenchyme cell migration since treatment of actively migrating cells with chondroitinase ABC reversibly inhibited their migration in vitro.

Animals↗
PubMed1991

Repeating developmental expression of G-Hox 7, a novel homeobox-containing gene in the chicken.

Here we describe the isolation and characterization of a new chicken homeobox-containing gene, G-Hox 7, which is related to Drosophila msh. The deduced amino acid sequence of the cDNA shows greater than 96% homology to the homeo domain of other vertebrate msh-like genes. As for other species, the amino and carboxy termini of the protein are, however, greatly divergent when compared phylogenetically. In situ hybridization studies revealed the early and wide-spread expression of G-Hox 7 during chick development. This includes its expression in the primitive streak and extraembryonic cells undergoing epiboly, and its expression along the neural axis, including the forebrain. Expression was also observed in the neural crest, neural crest-derived facial and branchial structures, the otocyst, limb, and heart valves. This widespread and recurrent expression of the transcript suggests that the gene may play an essential role at multiple sites during the initiation of new developmental pathways.

Amino Acid Sequence↗
PubMed1991

Expression of two nonallelic type II procollagen genes during Xenopus laevis embryogenesis is characterized by stage-specific production of alternatively spliced transcripts.

The pattern of type II collagen expression during Xenopus laevis embryogenesis has been established after isolating specific cDNA and genomic clones. Evidence is presented suggesting that in X. laevis there are two transcriptionally active copies of the type II procollagen gene. Both genes are activated at the beginning of neurula stage and steady-state mRNA levels progressively increase thereafter. Initially, the transcripts are localized to notochord, somites, and the dorsal region of the lateral plate mesoderm. At later stages of development and parallel to increased mRNA accumulation, collagen expression becomes progressively more confined to chondrogenic regions of the tadpole. During the early period of mRNA accumulation, there is also a transient pattern of expression in localized sites that will later not undergo chondrogenesis, such as the floor plate in the ventral neural tube. At later times and coincident with the appearance of chondrogenic tissues in the developing embryo, expression of the procollagen genes is characterized by the production of an additional, alternatively spliced transcript. The alternatively spliced sequences encode the cysteine-rich globular domain in the NH2-propeptide of the type II procollagen chain. Immunohistochemical analyses with a type II collagen monoclonal antibody documented the deposition of the protein in the extracellular matrix of the developing embryo. Type II collagen expression is therefore temporally regulated by tissue-specific transcription and splicing factors directing the synthesis of distinct molecular forms of the precursor protein in the developing Xenopus embryo.

Amino Acid Sequence↗
PubMed1991

Myogenic cytodifferentiation of the precardiac mesoderm in the rat.

The contractile cells of the primitive heart are derived from a subpopulation of the lateral plate splanchnic mesoderm. While the formation of the cardiac primordia has been studied in the avian embryo, little is known about this cell population in the mammal. To investigate the distribution and cellular differentiation of the myocardial precursors in the early mammalian embryo, we studied the sequential immunohistochemical appearance of desmin and myosin in whole mounts of rat embryos from the presomite (gestational day 9) through the 6-8 somite, straight heart tube (gestational day 10) stages of early cardiac morphogenesis. In contrast to the chicken, and previous reports in the mouse, our results show that myogenic differentiation of the muscle precursor cells of the heart begins in the presomite embryo prior to formation of the anterior intestinal portal or foregut. In addition, this cell population of the precardiac mesoderm appears as a single crescent-shaped population of cells in continuity across the midline which extends caudally during development and then fuses in the midline to form the primitive heart tube. Unlike skeletal myogenesis, desmin and myosin appear simultaneously and are codistributed throughout this initial period of heart development. These results suggest that myocardial differentiation in the rat is precocious when compared to the chicken and precedes the morphogenetic processes involved in formation of the primitive heart tube. Furthermore, this study provides the first description in the mammal of the spatial distribution of the myogenic precardiac mesoderm.

Animals↗
PubMed1991

Progressively restricted expression of a new homeobox-containing gene during Xenopus laevis embryogenesis.

We have isolated cDNAs encoding a novel Xenopus homeodomain-containing protein homologous to the mouse Hox-7.1 and the Drosophila muscle segment homebox (msh). Northern blot and RNAase protection experiments established that transcripts of the frog gene, termed Xhox-7.1, first appear at about the beginning of gastrulation. After a rapid increase, mRNA levels plateau between the neurula and middle-tailbud stages, and decrease steadily thereafter. In situ hybridization localized the Xhox-7.1 message to the dorsal mesodermal mantle of gastrula stage embryos. Comparison of the hybridization patterns of progressively more anterior cross-section of tailbud stage embryos localized the signal to the dorsal neural tube and neural crest, to specific regions of the lateral plate mesoderm, and to the cardiogenic region. By the tadpole stage, the Xhox-7.1 message appears only at specific sites in the central nervous system, such as in the dorsal hindbrain. Thus, during embryonic development levels of Xhox-7.1 expression decrease as the transcript becomes more progressively localized. Finally, evidence is presented of a distinct msh-like transcript (provisionally termed Xhox-7.1') which begins to accumulate at early-gastrula stage, as well.

Amino Acid Sequence↗