Defense system by mesenchyme cells in bipinnaria larvae of the starfish, Asterina pectinifera.

Here we characterize starfish larval mesenchyme cells, in terms of not only their phagocytic behavior, but also their structural and functional properties as a defense system. Our study reveals the following: (1) most mesenchyme cells construct a dynamic network structure beneath the body wall; (2) mesenchyme cells phagocytically respond to almost all foreign materials and form syncytial aggregates to conceal relatively large amounts and large sizes of foreign material; (3) the morphologies of the syncytial aggregates differ from one another depending on the species and the surface configuration of the cellular foreign material; (4) no mesenchyme cells respond to live mesenchyme cells even though they phagocytose chemically fixed cells; (5) mesenchyme cells phagocytose both cellular constituents effluxed from the ectodermal cells and foreign materials taken into the blastocoel through the body wall. Together, these results suggest that mesenchyme cells are equipped with a spectrum of abilities to engage in a defense system in starfish larva.

Fibrous component of the blastocoelic extracellular matrix shapes epithelia in concert with mesenchyme cells in starfish embryos.

By using a monoclonal antibody (4H11 Mab), we have investigated morphogenetic functions of a fibrous component of the blastocoelic extracellular matrix in relation to cellular activities during early development of the starfish Asterina pectinifera. The 4H11 fibers fill the blastocoele from the late-cleavage to late-gastrula stage and contain the 370-kDa proteinaceous molecule secreted only by the epithelial cells. When 4H11 Mab is introduced into the blastocoele of blastulae, the embryos reveal three distinct morphological abnormalities after the mid-gastrula stage: (1) Distribution of mesenchyme cells confined near the tip of the archenteron, (2) swelling of the posterior ectoderm, and (3) suppressed growth of the mouth, esophagus, and coelomic pouches.

Sorting Out of Presumptive Stomach Cells of the Starfish Embryo: (sorting out /presumptive stomach cells/starfish embryo/1,8-ANS).

Presumptive stomach cells of the starfish embryo are shown to sort out and to occupy a position in the endoderm of the reconstructed embryo. A new method is introduced to specifically mark these cells by staining the embryo with a fluorescent dye, 8-anilino-1-naphthalenesulfonic acid (1,8-ANS).

MESENCHYME CELLS IN STARFISH DEVELOPMENT: EFFECT OF TUNICAMYCIN ON THEIR DIFFERENTIATION, MIGRATION AND FUNCTION.

The effect of tunicamycin, an inhibitor of protein glycosylation, on starfish development was investigated. Specific developmental events such as 1) bulging of the archenteron tip, 2) migration of mesenchyme cells, 3) formation of coelomic pouches and 4) mouth formation, are inhibited in the presence of this drug. These events are discussed in connection with differentiation, migration and function of mesenchyme cells.

FORMATION OF JOINED LARVAE IN THE STARFISH, ASTERINA PECTINIFERA.

A method for joining larvae in the starfish, Asterina pectinifera, is presented. Any number of embryos are stably united by simple contact of the cell clusters (descendents of individual denuded eggs) before reaching the early blastula stage (ca. 6 1/2 hr after insemination at 21°C).

A "NORMAL" DEVELOPMENT OF DENUDED EGGS OF THE STARFISH, ASTERINA PECTINIFERA.

Experimental conditions that allow "normal" development of starfish eggs stripped of the fertilization membrane are reported in this paper. Four kinds of intercellular relation are distinguished during the pre-hatching stages of these eggs. Cells from 2- to 8-cell stages are hardly related to each other, while those from 16- to 128-cell stages are bound loosely together.