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Biomedical subjects

J W Lash

Publications and source records attributed to J W Lash.

17 recordsLinked to original sources
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↗
PubMed1979

Monomeric and aggregate proteoglycans in the chondrogenic differentiation of embryonic chick limb buds.

Proteoglycan heterogeneity was studied during the in vivo differentiation of embryonic chick limb cartilage. Recently, it has been shown that during the differentation of limb cartilage the proportion of the aggregated form of proteoglycans increases whereas the unassociated monomeric forms decrease, and this has been related to the synthesis of two link proteins at a specific stage of differentation. In this study it is suggested that the appearance of the aggregate formation is also due to synthesis of a stable hyaluronic acid binding region of the core protein. Thus, it can be concluded that differential gene expression for these proteins takes place as a differentiation phenomenon.

Animals↗
PubMed1978

Proteogylcan heterogeneity in embryonic chick articular and epiphyseal cartilages.

Proteoglycans from two regions of the chick limb rudiment (articular and epiphyseal) were examined for chemical microheterogeneity. These cartilages are composed of at least two series of proteoglycan variants whose glycosaminoglycan side chains display microheterogeneity with respect to the proportions of 4- and 6-linked ester sulfate. Other differences are noted which are consonant with the hypothesis that extracellular matrix components may be structurally adapted to a tissue's developmental fate or function.

Animals↗
PubMed1978

Microheterogeneities, non-equivalance, and embryonic induction.

The thrust of this report is to stress the importance of microheterogeneities in the microenvironment of differentiating tissues as a possible inducer or regulator of differentiation. During chondrogenesis both qualitative and quantitative changes occur in the proteoglycan population. Using molecular sieve chromatography, these changes can be characterized and used as indices of differentiation. Microheterogeneities of the extracellular matrix may be an example of "non-equivalence" as a regulatory device for differentiation.

Animals↗
PubMed1977

Heterogeneity of proteoglycans in developing chick limb cartilage.

Proteoglycan heterogeneity was studied during the maturation of embryonic-chick limb cartilage in vivo. The results suggest that during the differentiation of limb-bud cartilage the aggregated forms of proteoglycans increase between stages 24 and 35, whereas the non-aggregated or monomeric forms decrease. Only one link protein is found in stage-24 limb buds, whereas two are present at stage 35. Evidence suggests that the synthesis of link proteins may be a regulatory factor in limb chondrogenesis.

Animals↗
PubMed1975

Chondrocyte metabolism as affected by vitamin A.

Chondrocytes from 13-day-old embryonic chick sterna were cultured for 6 days in the presence of vitamin A (10 I.U./ml). Vitamin A treated chondrocytes became flattened and stellate within the first 24 hours of culture. After 6 days of culture, the treated cells contained 59% less DNA than the untreated controls. Sulfated glycosaminoglycan synthesis was inhibited 84%, and a greater percentage of GAG was secreted into the medium (90%) than in control cultures (78%). Vitamin A inhibited cell proliferation, and to varying degrees, RNA and protein synthesis, and these effects are dose dependent.

Animals↗
PubMed1975

The ubiquitous occurrence of chondroitin sulfates in chick embryos.

The synthesis of sulfated glycosaminoglycans has been studied in a wide variety of embryonic chick tissues. All tissues studied have the capability to manufacture, but not necessarily accumulate, the chondroitin sulfates as well as other glycosaminoglycans. The relative distribution of glycosaminoglycans differs between tissues and changes with age.

Animals↗