Cells In Seawater Research Articles

Glyconectin Cell Adhesion Epitope, β-d-GlcpNAc3S-(1→3)-α-l-Fucp, Is Involved in Blastulation of Lytechinus pictus Sea Urchin Embryos

Glycans, as the most peripheral cell surface components, are the primary candidates to mediate the initial steps of cell recognition and adhesion via glycan–glycan binding. This molecular mechanism was quantitatively demonstrated by biochemical and biophysical measurements at the cellular and molecular level for the glyconectin 1 β-d-GlcpNAc3S-(1→3)-α-l-Fucp glycan structure (GN1). The use of adhesion blocking monoclonal antibody Block 2 that specifically recognize this epitope showed that, besides Porifera, human colon carcinoma also express this structure in the apical glycocalyx. Here we report that Block 2 selectively immune-precipitate a Mr 580 × 103 (g580) acidic non-glycosaminoglycan glycan from the total protein-free glycans of Lytechinus pictus sea urchin hatched blastula embryos. Immuno-fluorescence confocal light microscopy and immunogold electron microscopy localized the GN1 structure in the apical lamina glycocalyx attachments of ectodermal cells microvilli, and in the Golgi complex. Biochemical and immune-chemical analyses showed that the g580 glycan is carrying about 200 copies of the GN1 epitope. This highly polyvalent g580 glycan is one of the major components of the glycocalyx structure, maximally expressed at hatched blastula and gastrula. The involvement of g580 GN1 epitope in hatched blastula cell adhesion was demonstrated by: (1) enhancement of cell aggregation by g580 and sponge g200 glycans, (2) inhibition of cell reaggregation by Block 2, (3) dissociation of microvilli from the apical lamina matrix by the loss of its gel-like structure resulting in a change of the blastula embryonal form and consequent inhibition of gastrulation at saturating concentration of Block 2, and (4) aggregation of beads coated with the immune-purified g580 protein-free glycan. These results, together with the previous atomic force microscopy measurements of GN1 binding strength, indicated that this highly polyvalent and calcium ion dependent glycan–glycan binding can provide the force of 40 nanonewtons per single ectodermal cell association of microvilli with the apical lamina, and conservation of glycocalyx gel-like structure. This force can hold the weight of 160,000 cells in sea water, thus it is sufficient to establish, maintain and preserve blastula form after hatching, and prior to the complete formation of further stabilizing basal lamina.

Dexamethasone modulates the activity of the eel branchial Na +/K +ATPase in both chloride and pavement cells

In fish, gills actively accumulate ions in freshwater (FW) with Na + absorption taking place at the level of pavement cells, and excrete monovalent ions, mainly Na + and Cl -, through the chloride cells in sea water (SW). The Na +/K +ATPase plays a crucial role in the functionality of osmoregulatory cells and we showed previously that angiotensin II modulates its activity in the eel gill (1). We here show the effects of synthetic steroid dexamethasone (DEX) on the activity of Na +/K +ATPase in both gill pavement and chloride cells from FW- and SW-adapted animals. Results showed that in the chloride cells 100 nM DEX provoked a significant increment in the activity of Na +/K +ATPase in both SW- and FW-adapted animals. This effect was greatest at 2 hours in SW, and at 6 hours in FW. The increment in the activity of the Na +/K +ATPase was dose-dependent in both environmental adaptations. Conversely, in pavement cells from FW-adapted eels 100 nM DEX decremented the activity of Na +/K +ATPase (4-fold reduction after 6 hour incubations), while in SW, DEX increased the enzyme activity of about 25% at 2 hours, and of about 55% at 6 hours. These results are consistent with the different physiological roles that pavement and chloride cells have in the two different adaptive conditions.

High performance liquid chromatography analysis of diarrhetic toxins inDinophysis spp. from the French coast

Diarrhetic shellfish poisoning has been a recurrent problem along the Brittany coast (France) since 1983. Okadaic acid (O.A.), the main toxin detected in mussels, is generally associated with the presence ofDinophysis cells in sea water. We report here the results of okadaic acid analyses by high performance liquid chromatography, on planktonic samples collected during the summer of 1991.D. sacculus, the majorDinophysis species, throughout this period, showed low okadaic acid content in raw extract, whereas toxic levels were 3- to 12-fold higher in sorted samples than in raw ones. A maximum O.A. concentration of 29.6 pg cell-1 was found inD. sacculus/D. cf. acuminata extract. Similarly, higher O.A. levels were noted in raw samples when these two species were associated. Generally speaking, variations in raw samples were similar to those in sorted samples. Nevertheless, whenD. rotundata reached a concentration equal to that ofD. sacculus in sorted samples, the O.A. level was lower.

Biosynthesis of macromolecules in chloride cells in the gills of the common eel, Anguilla anguilla, adapting to sea water

1. 1. Rates of incorporation of( 3H)thymidine, ( 14C)leucine and ( 3H)glucoseamine into TCA-precipitable products were measured in chloride and respiratory epithelial cell populations in the gills of silver eels adapting to sea water. 2. 2. A transient wave of DNA synthesis occurs in both cell populations during early stages of adaptation. 3. 3. Chloride cells but not respiratory epithelial cells turn over faster in sea water than in fresh water. 4. 4. A polysaccharide-rich fraction appears to turn over faster in chloride cells in sea water. A glycoprotein fraction appears to turn over faster in respiratory epithelial cells in sea water.

The relationship between the ionic composition of the environment and the secretory activity of the endocrine cell types of Stannius corpuscles in the teleost Gasterosteus aculeatus.

The corpuscles of Stannius of threespined sticklebacks contain two glandular cell types of presumed endocrine nature. To elucidate the function of both cell types the secretory activity of the cells was studied in fully adapted seawater and freshwater fishes and in specimens transferred from sea water to fresh water or adapted to media of various ionic composition. The secretory activity was established, in tissue sections and freeze-etch replicas, by estimating the volume of the nuclei, the density of the nuclear pores, and the frequency of exocytotic phenomena. The type-1 cells, ultrastructurally comparable to the predominant or only cell type described in many other teleosts, are more active in sea water than in fresh water. The activity of the type-2 cells, whose ultrastructural appearance is known only for salmonids and eels, is higher in fresh water. Transfer of seawater fishes to fresh water results in reduction of type-1 cells and activation of type-2 cells. The factors responsible for these changes were analyzed by exposure of fishes to solutions of various salts in fresh water and to artificial sea water with a reduced content of one of its components. The high activity of type-1 cells in sea water proved to be related to the high calcium content of this medium. These cells probably produce a substance comparable to hypocalcin, the endocrine factor isolated from the Stannius corpuscles of some other teleost species. The high activity of type-2 cells in fresh water appeared to be connected with the low sodium and potassium levels of this medium. Type-2 cells possibly produce a hitherto unknown hormone involved in the control of sodium and/or potassium metabolism.

Deformation and motion produced in isolated living cells by localized ultrasonic vibration.

Naturally-isolated living cells were subjected to ultrasonic vibration by means of the tip of a steel needle applied directly to the cell surface or inserted into a drop of a suspension of cells in sea water. The needle was machined into the tip of a stainless-steel cone, and the base of the cone was glued to one end of an electroded and polarized barium titanate hollow cylinder. This composite transducer was driven at its resonant frequency of approximately 85 000 cps. Ultrasound applier to the surfaces of egg cells of marine invertebrates produces rotation, translation, deformation, and fragmentation of the nucleoli; rotation and deformation of the nuclei; acoustic streaming of nucleoplasm and cytoplasm; and deformation of the cellular surface and fragmentation of the cell. Cells and intracellular bodies are often attracted to the sound source as a result of acoustic-radiation pressure, and, especially for whole cells in suspension, this attractive tendency is typically superposed on a tendency of the body to take part in acoustic streaming of the surrounding medium. Some aspects of the motion can be accounted for in terms of presently available theory of nonlinear acoustics. Information on the physical properties of nucleolus, nucleoplasm, and cytoplasm is gained from use of this sonic technique.