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The Superfluid High REynolds von Kármán experiment facility exploits the capacities of a high cooling power refrigerator (400 W at 1.8 K) for a large dimension von Kármán flow (inner diameter 0.78 m), which can work with gaseous or subcooled liquid (He-I or He-II) from room temperature down to 1.6 K. The flow is produced between two counter-rotating or co-rotating disks. The large size of the experiment allows exploration of ultra high Reynolds numbers based on Taylor microscale and rms velocity [S. B. Pope, Turbulent Flows (Cambridge University Press, 2000)] (Rλ > 10000) or resolution of the dissipative scale for lower Re. This article presents the design and first performance of this apparatus. Measurements carried out in the first runs of the facility address the global flow behavior: calorimetric measurement of the dissipation, torque and velocity measurements on the two turbines. Moreover first local measurements (micro-Pitot, hot wire,…) have been installed and are presented.

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We present a new cryogenic wind tunnel facility developed to study the high Reynolds number developed classical or quantum turbulence in liquid (4)He. A stable inertial round jet flow with a Reynolds number of 4 × 10(6) can be sustained in both He I and He II down to a minimum temperature of 1.7 K. The circuit can be pressurized up to 3.5 × 10(5) Pa. The system has been designed to exploit the self-similar properties of the jet far field in order to adapt to the spatial resolution of the existing probes. Multiple and complementary sensors can be simultaneously installed to obtain spatial and time resolved measurements. The technical difficulties and design details are described and the system performance is presented.

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Cryopreservation is widely used for long-term conservation of various tissues, embryos or gametes. However, few studies have described cryopreservation of invertebrate primary cell cultures and more particularly of marine invertebrate somatic cells. This technique would however be of great interest to facilitate the study of various metabolic processes which vary seasonally. The aim of the present study was to develop a protocol for cryopreservation of Crassostrea gigas vesicular cells. Different parameters were adjusted to improve recovery of cells after freezing. The most efficient cryoprotectant agent was a mix of Me(2)SO, glycerol, and ethylene glycol (4% each). The optimal cooling rate was -1 degrees Cmin(-1) down to -70 degrees C before transfer into liquid nitrogen. In these conditions the percentage of viable cells reached 70% of the control. The glucose metabolism of thawed cells was evaluated using radioactive glucose as a tracer. Immediately after thawing, glucose uptake involving membrane transporters was greatly reduced (24% of control) whereas glucose incorporation into glycogen was less affected (68% of control).

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Cultures of circulating cells from abalone (Haliotis tuberculata) may be used in fundamental research or in biotechnology. This paper describes attempts to develop a cryoconservation method for these hemocytes in order to constitute a standardized cell stock. Among a panel of five distinct cryoprotective solutions, 10% v/v glycerol ('G solution') was the most effective and better post-thaw recovery was achieved after cooling at 1 degrees C/min than after more rapid cooling (3 degrees C or 9 degrees C/min). In 2-day-old cultures, cell viability, assessed by DNA or protein content, was 83 and 78%, respectively, and metabolic activity, measured by the MTT reduction assay, reached 96%. Viability rates were only slightly reduced after 6 days of culture, suggesting a low proportion of damaged cells among the surviving hemocytes. This study identified a cryoprotective solution and a freezing protocol that allow thawed hemocytes to recover a large part of their viability.

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Dissociated mantle cells from the gastropod mollusc Haliotis tuberculata were cultured after a freezing-thawing procedure using either 10% dimethyl sulfoxide (Me(2)SO) or 10% glycerol (Gly) as a cryoprotector. The survival rate of 2-day-old cultured cryopreserved cells after thawing, based on analysis of DNA and protein contents, was nearly 80% in comparison with 2-day-old cultured fresh cells. Cells thawed after cryopreservation exhibited the maintenance of all tested physiological activities. Metabolic activity (measured by the MTT test) and the activity of alkaline phosphatase (a plasma membrane-bound enzyme) were not decreased in comparison to those in cultured fresh cells. In addition, cryopreserved cultured cells maintained a physiological stimulation ability in response to treatment with growth factors. These results taken together represent one of the most convincing demonstrations of the survival and of the recovery of intact functional activities of molluscan cells after a freeze-thawing procedure. Our results suggest that in the future primary cultures of cryopreserved mantle cells will be able to be used for fundamental research, in toxicity tests, or in the field of biotechnology.

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To evidence a collagen synthesis and identify which type(s) of collagen is present in hemocytes from the mollusc Haliotis tuberculata, we have performed three separate approaches, namely, de novo synthesis by cultured cells, immunological approaches, and northern blot analysis. We demonstrated first that after 40-hr labeling, the de novo synthesis of collagen in the cell layer of cultured hemocytes represents 9.48 +/- 1.25% with respect to the total [(3)H]proline-labeled protein synthesis. In addition, IGF-I elicited a significant stimulation of collagen synthesis in cultured hemocytes in a dose-dependent manner from 10(-10) to 10(-8) M. The maximal stimulation (10(-9) M) induced an increase of 286 +/- 56% with respect to 100% control. By immunocytochemistry and immunoblotting, we showed that hemocytes present immunoreactive molecules to antibodies directed against the type I fibrillar collagen. In addition, using as a probe Hf 677 corresponding to a human pro alpha1(I) collagen cDNA and which encompasses the (Gly-X-Y) repeated sequence found in all Metazoa, four collagen transcripts of approximately 6.4, 5, 2.2, and 2 kb in length have been detected. These data suggest the presence of fibrillar type I collagen in hemocytes and are compatible with the concept that these cells are involved in the extracellular matrix deposition, a cardinal function in tissue repair as well as in developmental processes. Our model may appear as an excellent system to study the role of growth factors on the regulation of collagen synthesis by molluscan hemocytes. J. Exp. Zool. 287:275-284, 2000.

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