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J W Lash

Publications and source records attributed to J W Lash.

At least 19 recordsLinked to original sources
PubMed1996

Skeletal myogenesis: the preferred pathway of chick embryo epiblast cells in vitro.

The epiblast layer of the chick embryo gives rise to all embryonic tissues. In vitro analyses were carried out to determine whether epiblast cells could form skeletal muscle prior to entry into the primitive streak. Epiblasts were separated from the mesoderm, hypoblast, and primitive streak, dissociated to produce a single cell suspension, and plated at high density. Myogenesis began on the first day in culture, and by the fifth day most cells had differentiated into skeletal muscle. Some cells differentiated without replicating. MyoD messenger RNA was present in epiblast tissue and translated in practically all cells in culture. Cells from regions of the epiblast which do not form muscle later in the embryo did so in vitro. Epiblasts cultured for 2 days as an intact epithelium, or in the presence of the mesoderm and hypoblast, did not undergo myogenesis. These findings demonstrate that myogenic potential is wide-spread within the primitive streak stage epiblast, and that muscle differentiation, which occurs relatively autonomously in culture, can be prevented by cell and tissue interactions.

Animals↗
PubMed1995

Posterior extension of the chick nephric (Wolffian) duct: the role of fibronectin and NCAM polysialic acid.

The nephric duct of the chick embryo starts to form at about stage 10 of Hamburger and Hamilton ([1951] J. Morphol. 88:49-92) and extends posteriorly, fusing with the cloaca at about the end of the third day of incubation (HH stage 17). Evidence from the literature suggests that the extension involves active migration of the posterior tip. This investigation concerned some molecules that might control this migration: fibronectin, vitronectin, the beta 1 integrin receptor, and NCAM polysialic acid. The concentration of fibronectin in the extracellular matrix was found by immunocytochemistry to be negligible at the posterior end of the duct; treatment of the living embryo with GRGDS failed to halt further extension of the duct; SEM examination of embryos treated with the synthetic peptides of fibronectin GRGDS, GRDGS, SDGR, and GRGES, or with vitronectin, revealed negligible morphological effects on the duct. It is concluded that there is yet no evidence that fibronectin is an important factor in duct migration. NCAM polysialic acid had a similar distribution to fibronectin, but treatment of the living embryo with Endo-N caused cessation of extension of the duct. Endo-N is an enzyme that specifically degrades PSA without affecting the NCAM polypeptide itself. It is suggested therefore that PSA may play an important role in duct extension. The synthetic peptides of fibronectin each produced distinctive patterns of blebbing on the surfaces of cells in trunk mesoderm, but the duct cells were unaffected. GRGES and SDGR caused blebbing on cells in the somites and the anterior segmental plate, though not on cells in the posterior segmental plate. This suggests that integrin receptors change in the anterior segmental plate as the mesoderm forms somites from somitomeres.

Amino Acid Sequence↗
PubMed1995

Cell surface alterations in embryonic tissues exposed to RGD-peptides: selective expression.

Whole animal studies have implicated cell adhesion molecules in a diverse array of developmental processes. The present study reports on the morphological effects of RGD-related peptides on the cell surface of various living chick embryonic tissues. We report a novel and characteristic plasma membrane reaction that is caused by treatment with different RGD-peptides. Not only does each peptide evoke a response in certain tissues and not in others, but each brings about a specific type of plasma membrane reaction (bleb). Although the mechanisms are unknown, the specificity of this phenomenon suggests that it could provide a window into new surface interactions in morphogenetic systems.

Animals↗
PubMed1994

Maturation of myogenic and chondrogenic cells in the presomitic mesoderm of the chick embryo.

The establishment of cells with myogenic or chondrogenic potential is temporally and spatially separated from terminal differentiation in the developing chick embryo. Both cell types arise from tissue adjacent to the neural tube and notochord, the paraxial mesoderm. A cell culture system was developed in order to study the maturation and differentiation of myogenic and chondrogenic cells along the length of the paraxial mesoderm at different stages of development. Somite and segmental plate cells obtained from 36- to 52-h (stages 10-15) embryos were plated as a monolayer on substrata of gelatin, fibronectin, or laminin. A substratum of gelatin plus fibronectin was most effective in supporting adhesion and differentiation. Maximal increase in number of cells in somite cultures occurred 24 h earlier than that in segmental plate cultures. Fewer skeletal muscle cells and chondroblasts were present in cultures prepared from progressively more caudal regions of the paraxial mesoderm and from younger embryos. Some cells present within the somites and the rostral two-thirds of the stage 13 segmental plate differentiated without replication after placement in culture. Only the progeny of cells from its caudal third, and from stage 10 somites and segmental plates, differentiated under these conditions. The results suggest that some myogenic and chondrogenic cells obtain the ability to differentiate under these in vitro conditions after stage 10 of development, as they occupy more rostral positions within the segmental plate relative to the addition of cells at its caudal end. Although some stage 13 segmental plate cells form skeletal muscle and cartilage directly after removal from the embryo, differentiation is not observed in ovo until these cells are incorporated into somites, a minimum of 10 h later. Three-dimensional tissue interactions, and/or cell-cell interactions, while not required for segmental plate cells to undergo myogenesis and chondrogenesis, may play a role in regulating the timing of terminal differentiation within the embryo.

Animals↗
PubMed1993

Early heart development: dynamics of endocardial cell sorting suggests a common origin with cardiomyocytes.

The myocardial and endocardial cell sorting out processes take place primarily between 19 and 29 hr of development in the avian embryo. This occurs in an apparent rostral to caudal wave through the heart forming region. During heart development considerable uncertainty exists regarding the processes that regulate cell commitments, progressive aggregation, and sorting out of the different precardiac cell populations. The question addressed in this report is whether endocardial and myocardial cells have a common origin or do the endocardial cells arise from a distinct population of cells from within the precardiac mesoderm. These cells then migrate to become localized between the developing myocardium above and the endoderm below. The distribution of preendocardial cells and premyocardial cells has been followed immunohistochemically in quail heart-forming region mesoderm explants from embryos approximately 18 hr in development and incubated for a 24-hr period. Differentiating myocardiocytes were immunostained with anti-N-cadherin and endocardiocytes with QH-1, a monoclonal antibody that recognizes an antigenic determinant on quail endothelial cells. Sparsely localized QH-1 labeled endothelial cells are localized in the stage 5 heart-forming region. These cells are often arranged in a columnar fashion in the mesoderm explants 6 hr after explantation. By 15-22 hr large patches of QH-1 expressing cells are interspersed with the N-cadherin expressing myocardiocytes. A subpopulation of cells express both N-cadherin and QH-1 antigen suggesting that endocardial and myocardial cells may arise from a common precursor population and that N-cadherin regulation may be a mechanism underlying specific cell sorting of these two cell populations during heart development.

Animals↗
PubMed1990

Blisters in the area pellucida, area opaca, and segmental plate of avian embryos.

This is a special communication in an area of special interest to all researchers using avian material. Avian embryos in the Northeast, representing four species (chicken, quail, duck, guinea hen), have been found to be drastically deficient in presomitic tissue (segmental plate tissue) between 45 and 60 h of incubation. These deficiencies first appear in the embryo as blisters, then, through tissue repair, they disappear and the embryos continue seemingly normal development. Similar blisters and excrescences appear in the area pellucida and area opaca between 20 and 30 h of incubation. Associated with these blisters and excrescences in very young embryos and blisters in segmental plates, but not necessarily the result of them, is a high incidence of congenital malformation during later development. These anomalies may be affecting the results obtained in avian research.

Animals↗
PubMed1990

Evidence for the involvement of receptors for fibronectin in the promotion of chick tail segmentation.

In the chick embryo the paraxial mesoderm forms about 50-53 pairs of somites, the precise number depending on the extent to which segmentation proceeds along the tail. However, the terminal mesoderm of the tail fails to segment despite the fact that it appears to contain a reservoir of potential somites. Why does this mesoderm not segment? Some clues can be obtained by comparing this non-segmenting region with the segmental plate in the trunk. We and others have shown that in the trunk region of the chick, cell adhesion plays a major role in somitogenesis and that this increased cell adhesion is associated with compaction of segments of mesoderm immediately prior to segmentation. This compaction can be brought about prematurely by fibronectin and by the specific adhesion peptide GRGDS. The terminal mesoderm in the tail resembles the segmental plate mesoderm in the trunk in undergoing compaction in response to fibronectin and GRGDS. The tail mesoderm differs from the segmental plate mesoderm in that it can also respond to peptides closely related to GRGDS. The response suggests that, whereas the integrin receptors for fibronectin and GRGDS appear to be specific in the presomitic trunk mesoderm, responding only to the specific adhesion-peptide GRGDS, the tail mesoderm may contain more heterogeneous sets of receptors within the integrin/VLA family that respond to a wider variety of ligands. Coincident with these differences is the phenomenon of regional cell death in the tail bud mesoderm. All of these factors are thought to play a role in the extent of segmentation in the paraxial mesoderm of the embryonic chick.

Animals↗
PubMed1990

Is chemotaxis a factor in the migration of precardiac mesoderm in the chick?

The chick heart is formed from bilateral patches of presumptive cardiac mesoderm cells which migrate over the endoderm and fuse in the midline. We have tested the possibility that this migration is controlled, at least in part, by a chemotactic substance exuded by the anterior end of the endoderm. We have used chick/quail combinations to follow naturally marked cells during the course of their migration. Chimaeric embryos were formed by fusing together parts of chick and quail embryos of stage 5-6. Each embryo possessed two pairs of precardiac regions, the quail pair lying immediately anterior to that of the chick. These chimaeras were then explanted in embryo culture. In the event of chemotaxis, cells from the posterior end of the quail precardiac mesoderm might be expected to invade the chick area. Samples of explants and chimaeras were examined at intervals from 2 to 24 h, but in no case were cells found to have changed their direction of migration as a result of the proximity of anterior endoderm. It is concluded that this work does not provide evidence for a chemotactic attraction by the anterior end of the endoderm.

Animals↗
PubMed1990

Migration of chick blastoderm under the vitelline membrane: the role of fibronectin.

In the earliest stages of its development the chick blastoderm is a flattened disc at the surface of the yolk. It gradually increases in diameter, partially because the cells are rapidly proliferating, but also because the cells at the periphery (the margin of overgrowth) are migrating in a centrifugal direction. These cells utilize the inner surface of the vitelline membrane as their substratum. In the normal blastoderm, these cells at the edge of the spreading blastoderm are the only cells which are attached to the vitelline membrane. This investigation is concerned with the possible role played by fibronectin in the interaction between these migrating cells and the vitelline membrane. Chick blastoderms, explanted by the New (1955) technique have been treated with synthetic peptides that mimic the adhesive recognition signal of the fibronectin molecule. The pentapeptide GRGDS (containing the specific RGD cell adhesion sequence) caused the edge cells of the blastoderm to detach within minutes, and the expansion of the blastoderm was inhibited for about 4 hr. After this period there was gradual recovery and the cells reattached and spreading resumed. Examination of the margin of the blastoderm by scanning electron microscopy showed that cell processes were lost soon after treatment with GRGDS but concomitant with reattachment and the resumption of spreading, the cell processes reformed. The pentapeptide GRDGS (with the amino acids G and D inverted) produced a brief inhibition of spreading, but after an hour these blastoderms spread at the same rate as controls. Immunocytochemical staining with anti-fibronectin demonstrated that fibronectin was not only present at the interface of the edge cells and the vitelline membrane, but also between the epiblast and the hypoblast. These results indicate that tissue movement during blastoderm spreading is dependent upon fibronectin and that the specific RGD amino acid sequence, and presumably the VLA/integrin family of receptors, is involved in this embryonic morphogenetic movement.

Amino Acid Sequence↗
PubMed1988

Malformations in chicken embryos in the Northeast.

In Deborah Barnes' article "Joint Soviet-U.S. attack on heart muscle dogma" (Research News, 14 Oct., page 193), credit for a photograph was inadvertently omitted. John Oberpriller of the University of North Dakota graciously supplied the photograph of a newt ventricular myocyte dividing in culture.

Animals↗
PubMed1988

Type X collagen alterations in rachitic chick epiphyseal growth cartilage.

We examined collagens of both normal and vitamin D-deficient chick epiphyseal growth cartilage. Special emphasis was placed on the study of Type X collagen, a recently described product of hypertrophic chondrocytes. Scanning electron microscopy of the epiphyseal growth cartilage of vitamin D-deficient chickens showed an enlarged growth cartilage with a disorganized extracellular matrix. The cartilage collagens were solubilized by proteolytic digestion and disulfide bond reduction of both normal and rachitic growth tissues. Sequential extraction with neutral salt and acetic acid buffers followed by pepsin digestion at 4 degrees C solubilized about 12% of normal tissues and about 7% of collagen from rachitic growth cartilage. Treatment of the pepsin-resistant collagens with neutral salt-dithiothreitol buffer under nondenaturing conditions and a subsequent pepsin digestion increased the yield of solubilized collagen to greater than 95% of the total tissue collagen. Results of the biochemical studies showed a marked increase in the relative proportion of Type X collagen (from 5.6 to 27.9%), a corresponding decrease in the proportions of Types II and IX collagens, and a moderate increase in Type XI collagen in rachitic cartilage. Amino acid analysis indicated that there were no differences in the Types II and X collagens of normal and rachitic cartilage. However, an abnormality in the relative proportions of the CNBr peptides of Type X collagen was detected in the rachitic cartilage. We suggest that the increase in collagen in the rachitic state may reflect increased levels of Type X collagen synthesis by cells in the hypertrophic region. It is likely that in rickets the overproduction of Type X collagen may be a compensatory mechanism by which the hypertrophic chondrocyte attempts to provide a maximum area of calcifiable matrix for the calcium-depleted serum.

Amino Acids↗
PubMed1988

A role for fibronectin in the migration of avian precardiac cells. I. Dose-dependent effects of fibronectin antibody.

An anterior-posterior concentration difference of fibronectin associated with the endoderm in early chick embryos has been implicated in the directional migration of precardiac mesoderm cells. We have examined the effect of increasing concentrations of an antibody to fibronectin (FN) to test the essentiality of FN to precardiac cell migration. For controls embryos were incubated in the presence of antibodies produced against several other extracellular components, such as laminin and anti-collagen types I and IV, as well as against integrin, a cell surface FN receptor. Embryos were also incubated in the presence of a high concentration of exogenous FN, as well as in the presence of an RGD-containing synthetic pentapeptide that is recognized by the FN receptor. After incubation of chick embryos in various concentrations of anti-FN (5 to 80 micrograms/ml), a dose-dependent effect of anti-fibronectin was observed, whereby heart development was arrested at high concentrations of anti-FN. Early developmental stages were more susceptible to lower antibody concentrations than later stages. Incubation in the presence of the RGD-containing synthetic peptide resulted in partial cardiabifida. None of the antibodies serving as controls affected cell migration or early heart development. These results support the hypothesis that FN is a major component in the migratory pathway and plays a role in the directional migration of precardiac cells to the embryonic midline.

Animals↗
PubMed1988

A role for fibronectin in the migration of avian precardiac cells. II. Rotation of the heart-forming region during different stages and its effects.

Precardiac cells in early chick embryos between stages 5 and 8 of development migrate anteriorly and medially from two well-defined, lateral heart-forming regions to the lateral walls of the developing anterior intestinal portal. Previously, it was shown that an increasing fibronectin (FN) concentration exists at the endoderm-mesoderm interface along the pathway in which the cells move. Thus, a haptotactic mechanism for precardiac cell migration was suggested. To analyze fibronectin's role further the FN concentration difference was interrupted by microsurgically rotating both the precardiac region mesoderm and endoderm (ectoderm was left intact) and by perturbation with the use of an antibody to fibronectin. These experiments, reported here, indicated that precardiac cells do follow cues established by a FN concentration difference at the mesoderm-endoderm interface in the lateral region and that anti-fibronectin can inhibit normal cell migration during heart formation.

Animals↗
PubMed1988

Somitogenesis in the mouse embryo.

This report describes the initiation of somitogenesis in the mouse embryo. Correlations are made with fibronectin distribution around the unsegmented mesoderm and the distribution of cytoskeletal elements within the cells as they undergo morphogenetic movements. The same temporal and topological changes in fibronectin, laminin, and cytoskeletal elements are seen in mouse somitogenesis as in the chick embryo. A notable exception is that the epithelial stage of somitogenesis in the mouse does not form a closed vesicle as it does in the chick. In the mouse the mesial portion of the forming somite does not become epithelial before the migration of sclerotomal cells.

Actins↗
PubMed1987

Synthetic peptides that mimic the adhesive recognition signal of fibronectin: differential effects on cell-cell and cell-substratum adhesion in embryonic chick cells.

Although fibronectin has been implicated in cell-cell as well as cell-substratum interactions, most experimentation has focused on cell-substratum interactions of fibroblasts. We have examined the effect of the specific peptide GRGDS derived from the cell-binding sequence of fibronectin upon cell-cell and cell-substratum interactions using embryonic cells and tissues. Embryonic chick segmental plate cells undergo compaction (i.e., increased cell-cell adhesion) during the early stages of somitogenesis. Fibronectin has been implicated in this increase in cell-cell interaction. In contrast, precardiac mesoderm undergoes directional migration upon a fibronectin-rich substratum, exhibiting both cell-cell and cell-substratum interactions. The segmental plate cells, which are the precursors of embryonic somites, normally show very little cell-cell or cell-substratum interaction in culture. These cells exhibit a striking increase in intercellular adhesion, but exhibit no cell-substratum adhesion, in the presence of relatively low concentrations of the fibronectin-derived peptide GRGDS. Somite cells, which normally exhibit both cell-cell and cell-substratum adhesion in culture, show complete inhibition of cell-substratum adhesion in the presence of this peptide. Precardiac mesoderm, which normally exhibits both cell-cell and cell-substratum adhesion in culture, shows a marked inhibition of both processes in the presence of GRGDS. Since the finding that a monovalent competitive inhibitor of fibronectin binding can stimulate cell-cell adhesion was unexpected, we propose a "trigger" hypothesis, whereby the peptide recognition signal acts as a specific signal or trigger for the morphogenetic process of compaction. There is a striking specificity to this effect, since synthetic peptides with even conservative changes in the amino acid sequence have no effect. Finally, we find that under certain conditions the effect of the specific peptide is lost in 6-8 hr and the cells resume cell-substratum interactions or, in the case of the segmental plate cells, revert from the compacted state and exhibit a substantial decrease in cell-cell adhesion. Our studies indicate the diversity of cell and tissue responses possible when even a single peptide inhibitor of adhesion, and we have identified the first known activating effect of a fibronectin peptide on cell behavior and differentiation.

Amino Acid Sequence↗
PubMed1986

Expression of type X collagen mRNA levels in embryonic chick sternum during development.

Embryonic chick sternum cartilage exhibits profound spatial and temporal changes in Type X collagen biosynthesis during development. Production of this collagen is confined to the presumptive calcification region and its expression is not acquired until stage 43. To examine the mechanisms responsible for regulation of developmental changes in biosynthetic expression of Type X collagen, we determined the levels of translatable Type X procollagen mRNA employing a cell-free translation system. We found that mRNA capable of directing Type X collagen synthesis was present exclusively in cartilage destined to undergo calcification and that its levels were nearly equivalent at all stages of development. These findings suggest that expression of Type X collagen in embryonic chick sternum is determined at the translational level.

Animals↗
PubMed1986

Biosynthetic expression of type X collagen in embryonic chick sternum cartilage during development.

To investigate the temporal and topographic changes in the expression of various collagens during the process of endochondral bone formation, qualitative and quantitative analysis of the collagens synthesized by organ cultures from the separated presumptive calcification and permanent cartilaginous regions of embryonic chick sternum at various stages of development was performed. Special emphasis was placed on the study of Type X collagen, a recently described species that may play a role in tissue calcification. We found that Type X collagen is biosynthesized exclusively by cartilage from the zone of presumptive calcification and that its biosynthetic expression is acquired at stage 43 (day 17) of sternal development. Quantitative analysis indicated that Type X was the biosynthetic product which showed the most dramatic changes increasing markedly with increased sternal age. While no Type X collagen could be detected at stage 40, it represented about 12% of the total collagen synthesized at stage 43, further increasing to 45% at stage 46 of sternal development. The increase in Type X collagen in the presumptive calcification region was accompanied by a relative decrease in the proportion of 1 alpha, 2 alpha, 3 alpha, alpha 1(II), and Type IX collagens. In contrast, the permanent hyaline cartilage did not display detectable synthesis of Type X collagen at any sternal age. The strict topographic distribution and the temporal expression of Type X collagen biosynthesis coincident with the development of sternal calcification, confirm the notion that this collagen may play an important role in the extracellular matrix remodeling associated with the initiation and progression of tissue calcification.

Animals↗