Fourth-order interference in the Wigner representation for parametric down-conversion experiments

In the Wigner formalism, after giving a general description of a light beam, the theory of parametric down-conversion is developed to second-order in the coupling constant. We then describe the detection process by calculating the auto-correlation and cross-correlations of the signal and idler beams. Four recent experiments are analyzed in detail: interference on a screen, Franson's experiments [Phys. Rev. Lett. 62, 2205 (1989)], Rarity and Tapster's experiments [Phys. Rev. Lett. 64, 2495 (1990)], and induced coherence without induced emission [X. Y. Zou, L. J. Wang, and L. Mandel, Phys. Rev. Lett. 67, 318 (1991)]

Long-term cryostorage does not negatively affect the recovery of Caenorhabditis elegans

Cryostorage of Caenorhabditis elegans nematodes is important to maintain the many lines used for research. The standard method uses 15% of glycerol in M9-Buffer and a cooling rate of 1 °C/min; then worms can be stored in a −80 °C freezer or in liquid nitrogen. The recovery of C. elegans from stocks stored in liquid nitrogen is reported to be in the range of 35–45% and slightly decreases after years of storage. The storage at −80 °C is also considered safe, but the recovery is not as high as in liquid nitrogen. These observations have not been experimentally reported and therefore require verification. In this study, the standard methods were used in a set of experiments to compare the recovery of larvae and adult worms stored at −80 °C or in liquid nitrogen, after short- (a week) or long-term storage (3.5 years). No differences were observed in recovery, either for the time of storage or for the temperature of storage. Recovery of larvae was 32% at −80 °C and 36% in liquid nitrogen after 3.5 yr and that was not significantly different from the 7-d recovery rates. Adult worm recovery was below 5% for all treatments. These results suggest that both methods of storage can be used to successfully store C. elegans larvae for at least 3.5 years.This work was supported by Junta de Andalucía (P08-CTS-03965), the research group CryoBioTech: cryopreservation of tissues and organs (BIO289) and the Ministry of Economy and Competitiveness (RTC-2016-4733-1).Peer reviewe

Use of fine capillaries for cryopreservation of Caenorhabditis elegans by vitrification

Caenorhabditis elegans is an exceptional model organism. More than twenty thousand different strains have been developed, increasing knowledge on countless topics. However, the traditional method to cryopreserve this nematode, based on slow freezing, usually reaches recovery rates of around 35% for the L1 and L2 larval stages. Here, we propose two alternative methods to cryopreserve this nematode based on vitrification that are applicable in common laboratories and allow the selective individual cryopreservation of this organism. These new methods require ultra-high warming rates, which are achieved by employing very thin capillaries as the nematode container, and a very low final concentration of cryoprotectants, which, as compared to slow freezing, reduce toxicity damage. The recovery rate was 98.5% for larvae (L1 - L4) and 84.3% for adults. Given these results, our procedures offer an alternative to cryopreserve this nematode (larvae and adults) with higher recovery rates, avoiding expensive requirements. Indeed, it only needed a container with liquid nitrogen and a warming bath for water at 37 °C. The high performance of this approach has been revealed by preserving the long-term memory and, probably, the connectome of this nematode.This work was supported by Junta de Andalucía (P08-CTS-03965), the research group CryoBioTech: cryopreservation of tissues and organs (BIO289) and the Ministry of Economy and Competitiveness (RTC-2016-4733-1).Peer reviewe

Criopreservación celular por vitrificación con bajas concentraciones de crioprotector.

Criopreservación celular por vitrificación con bajas concentraciones de crioprotector.El objeto de la presente invención se refiere a un nuevo procedimiento de criopreservación celular, que consigue la vitrificación de las muestras biológicas con presenc

HIFU Rewarming of Organs After Cold Preservation: Ex Vivo Assessment of Heart Performance in Murine Model

This research was partially supported by the grants Plan Propio de Investigacion de la Universidad de Sevilla and Ministry of Science and Technology (Spain), AICIA, PEJUS-89, and EQC2019-005949.Peer reviewe

Use of X-ray Computed Tomography for ice detection applied to organ cryopreservation

ne of the main problems in the cryopreservation of biological samples is the formation of ice and the consequent mechanical damage to cells and tissues, due to the crystalline structure of ice and its associated mechanical damage. It is necessary to detect this deleterious formation of ice, especially in tissues and organs, because of their large volume and the complexity of their vascular system in the case of bulky organs. In this work, we propose the use of X-ray Computed Tomography (CT) to detect this ice formation inside tissues and organs. To achieve this aim, rabbit kidneys were loaded with cryoprotectant solutions containing Me2SO at low temperatures (below −140°C). Drops of water with a volume between 2 and 8 μL were then introduced inside the organs. Finally, the rabbit kidneys were cooled to −196°C. Volumes of ice of up to 1 μL were detected in our CT device, with a resolution of up to 50 μm, validating the proposed technology. On the contrary, we analyzed bovine ovarian tissues cryopreserved with a controlled-rate slow-cooling protocol. CT images showed the different structure on the extracellular ice formation according to the procedure, and even the intracellular ice that can be formed in the tissues. These positive results have a straightforward application in the control of the formation of ice, of significant importance for the creation of biobanks.Peer reviewe

The equilibrium vitrification technique for human ovarian tissue cryopreservation

Trabajo presentado en CRYO 2018, 55th Annual Meeting of the Society for Cryobiology, celebrado en Madrid (España), del 10 al 13 de julio de 2018Peer reviewe

Utilization of a new freezing protocol containing a higher DMSO concentration to cryopreserve human ovarian tissue

Trabajo presentado en la Society for Low Temperature Biology Meeting (SLTB), celebado en Cambridge (Reino Unido) del 19 al 20 de septiembre de 2017Peer reviewe