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Previous studies have demonstrated that during neural fold fusion in different species, an apical extracellular material rich in glycoconjugates is involved. However, the composition and the biological role of this material remain undetermined. In this paper, we show that this extracellular matrix in rat increases notably prior to contact between the neural folds, suggesting the dynamic behaviour of the secretory process. Immunostaining has allowed us to demonstrate that this extracellular matrix contains chondroitin sulphate proteoglycan (CSPG), with a spatio-temporal distribution pattern, suggesting a direct relationship with the process of adhesion. The degree of CSPG involvement in cephalic neural fold fusion in rat embryos was determined by treatment with specific glycosidases.In vitro rat embryo culture and microinjection techniques were employed to carry out selective digestion, with chondroitinase AC, of the CSPG on the apical surface of the neural folds; this was done immediately prior to the bonding of the cephalic neural folds. In all the treated embryos, cephalic defects of neural fold fusion could be detected. These results show that CSPG plays an important role in the fusion of the cephalic neural folds in rat embryos, which implies that this proteoglycan could be involved in cellular recognition and adhesion. Copyright © 2008 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Epithelial cells from the anterior and equatorial surfaces of the frog lens were isolated and used the same day for studies of the Na/K ATPase. RNase protection assays showed that all cells express alpha(1)- and alpha(2)-isoforms of the Na/K pump but not the alpha(3)-isoform, however the alpha(2)-isoform dominates in anterior cells whereas the alpha(1)-isoform dominates in equatorial cells. The whole cell patch-clamp technique was used to record functional properties of the Na/K pump current (I(P)), defined as the current specifically inhibited by dihydro-ouabain (DHO). DHO-I(P) blockade data indicate the alpha(1)-isoform has a dissociation constant of 100 microm DHO whereas for the alpha(2)-isoform it is 0.75 microm DHO. Both alpha(1)- and alpha(2)-isoforms are half maximally activated at an intracellular Na(+)-concentration of 9 mm. The alpha(1)-isoform is half maximally activated at an extracellular K(+)-concentration of 3.9 mm whereas for the alpha(2)-isoform, half maximal activation occurs at 0.4 mm. Lastly, transport by the alpha(1)-isoform is inhibited by a drop in extracellular pH, which does not affect transport by the alpha(2)-isoform. Under normal physiological conditions, I(P) in equatorial cells is approximately 0.23 microA/microF, and in anterior cells it is about 0.14 microA/microF. These current densities refer to the area of cell membrane assuming a capacitance of around 1 microF/cm(2). Because cell size and geometry are different at the equatorial vs. anterior surface of the intact lens, we estimate Na/K pump current density per area of lens surface to be around 10 microA/cm(2) at the equator vs. 0.5 microA/cm(2) at the anterior pole. [ABSTRACT FROM AUTHOR]

The expansive force generated by the positive pressure of the neural tube fluid confined inside the brain vesicles has been shown to be a key factor during the earliest stages of brain morphogenesis and development of chick embryos. In a previous study, we demonstrated the existence of an intracavity extracellular matrix rich in condroitin sulfate in this species, which could be involved in the regulation of the expansive process. In this report, scanning electron microscopy and immunohistochemistry show that, after neurulation, a similar extracellular matrix rich in chondroitin sulfate is present inside the brain vesicles of rat embryos during early enlargement of the brain anlage. In vitro treatment of rat embryos with β-D-xyloside (a chemical compound which disrupts chondroitin sulfate synthesis) shows that changes in intralumen chondroitin sulfate concentration are accompanied by significant changes in brain anlage growth. These results support the hypothesis that intracerebral chondroitin sulfate plays a relevant role in the regulation of the expansive process of the brain anlage of rat embryos, and could represent a general mechanism in the early brain development of avian and mammalian embryos. [ABSTRACT FROM AUTHOR]

The iris anlage of 3-10 day old chicken embryos was studied by both light and electron microscopy. Serial semithin sections showed that some of the mesenchymal cells overlying the eye cup moved into the primitive eye cavity by the 3rd day of incubation. On the 4th day some of these cells came into close contact with the basement membrane of the dorsal iris epithelium. The bases of the epithelial cells were flat at this stage. Towards the 10th day they formed cytoplasmic processes which did not penetrate the basement membrane. Fine mesenchymal cytoplasmic processes and a large number of extracellular fibrils developed in the epithelial-mesenchymal interface. The fine mesenchymal processes came into close contact with the basement membrane of the posterior iris epithelium but did not penetrate it. Collagen-like material was observed within the cisternae of the rough ER of the mesenchymal cells at certain stages of development. Both, the mesenchymal cells and the collagen fibrils adjacent to the posterior iris layer disappeared by the 10th day when the entire iris epithelium was completely pigmented. The possible origin of the collagen fibrils and the differentiation of the posterior iris epithelium are discussed. [ABSTRACT FROM AUTHOR]

A subject index for the volume 5, number 4, 1985 issue of "Ophthalmic & Physiological Optics" is presented.

Epithelial or mesenchymal isolates cultivated on the chicken chorioallantoic membrane singly do not possess the potential for tooth morphogenesis. However, when randomly recombined in vitro, their histogenic interaction relates to tooth formation. After 16 days of continuous culture, surviving recombinants formed an advanced tooth germ. Such structures did not, however, demonstrate uniformity in odontogenesis or in developmental cusp patterns. [ABSTRACT FROM AUTHOR]