Cryopreservation of Pacific oyster (Crassostrea gigas) larvae: Revisiting the practical limitations and scaling up the procedure for application to hatchery

International audiencePacific oyster Crassostrea gigas is one major species for aquaculture, and the development of breeding programs and the need for preservation of wild stock genetic resources prompted the need for larvae cryopreservation. The objective of the present study was to choose the most reliable protocol from several existing publications, to test its biological and practical limitations, and to adapt it to hatchery conditions. The selected protocol was characterized by a very slow freezing rate without seeding, and by the use of ethylene glycol and sucrose as cryoprotectant. The best survivals after thawing and rearing up to 48 h post fertilization (hpf) were obtained with larvae that were frozen at late trochophore (20 hpf) and early-D (24 hpf) stages. Increasing the larvae concentration in the straws and using high throughput straw filling and freezing devices did not alter the cryopreservation outcome. The whole procedure was applied to cryopreservation in a commercial hatchery (Satmar, France), and the thawed larvae yielded 9.4 ± 4.5% survivals at 12 days post fertilization. The overall success was dampened by some variability in the larvae survival that is likely due to the physiological status of the larvae. In all, the proposed procedure is robust and reliable and can be used for cryobanking of oyster genetic resources

Maintenance of cyanotoxin production by cryopreserved cyanobacteria in the New Zealand culture collection

A culture collection of freshwater planktonic and benthic cyanobacteria collected from sites across New Zealand has been established at the Cawthron Institute, Nelson, New Zealand. Limited resources led to uncertainty regarding the long-term maintenance of this collection. The present study demonstrates cryopreservation to be a viable method for long-term storage of cyanobacteria. Seventeen of 20 strains evaluated were successfully cryopreserved using the permeating cryopreservation agent dimethyl sulfoxide (Me2 SO), at a final concentration of 15% (v/v). Cyanotoxin analysis was undertaken on selected strains known to produce microcystins, nodularin, anatoxin-a, and saxitoxins. All strains retained their ability to produce these toxins following cryopreservation

Second asymptomatic carotid surgery trial (ACST-2) : a randomised comparison of carotid artery stenting versus carotid endarterectomy

Background: Among asymptomatic patients with severe carotid artery stenosis but no recent stroke or transient cerebral ischaemia, either carotid artery stenting (CAS) or carotid endarterectomy (CEA) can restore patency and reduce long-term stroke risks. However, from recent national registry data, each option causes about 1% procedural risk of disabling stroke or death. Comparison of their long-term protective effects requires large-scale randomised evidence. Methods: ACST-2 is an international multicentre randomised trial of CAS versus CEA among asymptomatic patients with severe stenosis thought to require intervention, interpreted with all other relevant trials. Patients were eligible if they had severe unilateral or bilateral carotid artery stenosis and both doctor and patient agreed that a carotid procedure should be undertaken, but they were substantially uncertain which one to choose. Patients were randomly allocated to CAS or CEA and followed up at 1 month and then annually, for a mean 5 years. Procedural events were those within 30 days of the intervention. Intention-to-treat analyses are provided. Analyses including procedural hazards use tabular methods. Analyses and meta-analyses of non-procedural strokes use Kaplan-Meier and log-rank methods. The trial is registered with the ISRCTN registry, ISRCTN21144362. Findings: Between Jan 15, 2008, and Dec 31, 2020, 3625 patients in 130 centres were randomly allocated, 1811 to CAS and 1814 to CEA, with good compliance, good medical therapy and a mean 5 years of follow-up. Overall, 1% had disabling stroke or death procedurally (15 allocated to CAS and 18 to CEA) and 2% had non-disabling procedural stroke (48 allocated to CAS and 29 to CEA). Kaplan-Meier estimates of 5-year non-procedural stroke were 2·5% in each group for fatal or disabling stroke, and 5·3% with CAS versus 4·5% with CEA for any stroke (rate ratio [RR] 1·16, 95% CI 0·86-1·57; p=0·33). Combining RRs for any non-procedural stroke in all CAS versus CEA trials, the RR was similar in symptomatic and asymptomatic patients (overall RR 1·11, 95% CI 0·91-1·32; p=0·21). Interpretation: Serious complications are similarly uncommon after competent CAS and CEA, and the long-term effects of these two carotid artery procedures on fatal or disabling stroke are comparable