Directional freezing of spermatozoa and embryos

2014 ◽  
Vol 26 (1) ◽  
pp. 83 ◽  
Author(s):  
Amir Arav ◽  
Joseph Saragusty
Keyword(s):  
Cooling Rate ◽  
Drop Size ◽  
Mechanical Damage ◽  
Rapid Freezing ◽  
Wild Animals ◽  
Microscope Slide ◽  
Freezing Method ◽  
Wide Range ◽  
Sexed Semen ◽  
Directional Freezing

Directional freezing is based on a simple thermodynamic principle whereby the sample is moved through a predetermined temperature gradient at a velocity that determines the cooling rate. Directional freezing permits a precise and uniform cooling rate in small- and large-volume samples. It avoids supercooling and reduces mechanical damage caused by crystallisation. Directional solidification was used to date for slow and rapid freezing, as well as for vitrification of oocytes and embryos by means of the minimum drop size technique: small drops are placed on a microscope slide that is moved at high velocity from the hot base to the cold base. Sperm samples from a wide range of domestic and wild animals were successfully cryopreserved using the directional freezing method. The bovine sexed semen industry may benefit from the increased survival of spermatozoa after directional freezing.

Directional Solidification Stage With Dynamically Variable Speeds: Assessment of Cell Viability After Interrupted Cooling

2011 ◽  
Author(s):  
Josh LaFountain ◽  
Ram V. Devireddy
Keyword(s):  
Cell Viability ◽  
Directional Solidification ◽  
Cooling Rate ◽  
Room Temperature ◽  
Adult Stem Cells ◽  
Membrane Integrity ◽  
Freezing Method ◽  
A Cell ◽  
Directional Freezing ◽  
Solidification Stage

A two-step directional freezing method was utilized to assess the membrane integrity in frozen/thawed adult stem cells (ASCs). Using a custom built directional solidification stage (DSS) we determined that cells cooled at two different rates (i.e., a slower rate between room temperature, 27 °C and −10 °C and a higher rate between −10 °C and −60 °C) experienced significantly higher loss of cell viability when compared with those cooled at a single and uniform slower cooling rate between 27 °C and −60 °C. Specifically, the cells cooled using the two-step freezing method exhibited a post-thaw cell viability of ∼17% while those that were cooled using the traditional method exhibited a cell viability of 49%. We also found that varying the cooling rate between 27 °C and −10 °C did not significantly affect the post-thaw viability of ASCs, suggesting that they are not susceptible to supra-zero cooling injury.

Theoretical Aspccts of Cloud Drop Distributions

1949 ◽  
Vol 2 (3) ◽  
pp. 376 ◽  
Author(s):  
EB Kraus ◽  
B Smith
Keyword(s):  
Cooling Rate ◽  
Drop Size ◽  
Initial Temperature ◽  
Theoretical Study ◽  
Air Pressure ◽  
Size Spectrum ◽  
Condensation Nuclei ◽  
Cloud Drop ◽  
Rate Of Cooling

A theoretical study indicates that the number and size of the drops formed in a cloud vary with the rate of cooling, the initial temperature, and the air pressure. The faster the cooling rate, the lower the initial temperature, and the lower the altitude, the greater is the number of drops and the smaller their size. The drop size spectrum also depends, to a large extent, on the number of available condensation nuclei. Furthermore, it tends to be widened by sedimentation and turbulence.

Marine Wildlife Bycatch Under the CMS: Progress and Prospects

2003 ◽  
Vol 18 (2) ◽  
pp. 215-240
Keyword(s):  
Marine Species ◽  
Wild Animals ◽  
Migratory Species ◽  
Considerable Potential ◽  
Marine Turtles ◽  
Incidental Capture ◽  
Wide Range ◽  
Marine Wildlife

AbstractThis article explains the provisions of the Convention for the Conservation of Migratory Species of Wild Animals (CMS) and its subsidiary marine wildlife instruments as they relate to bycatch management. The CMS was primarily developed with the purpose of protecting and conserving migratory species and their habitats. The Convention was initially regarded as little more than a paper accord. Since its inception the CMS has undergone gradual significant changes not only in its scope but also in its geographical coverage. There are ten subsidiary instruments currently in force under the CMS which include regional accords on a wide range of marine species such as cetaceans, marine turtles and pinnipeds. These agreements have considerable potential for regulating the incidental capture of marine wildlife in fisheries. Issues of interest in regard to these agreements include the use of non-binding instruments, and mechanisms for coordination between accords. This article examines the CMS and its subsidiary instruments; it identifies challenges facing the Convention, and provides options for the development of more comprehensive approaches to the management of bycatch.

Classification and Prediction of Dripping Drop Size for a Wide Range of Nozzles by Wetting Diameter

Langmuir ◽  
2019 ◽  
Vol 35 (13) ◽  
pp. 4763-4775 ◽  
Author(s):  
Pei-Hsun Tsai ◽  
An-Bang Wang
Keyword(s):  
Drop Size ◽  
Wide Range

scholarly journals Detection of Pneumocystis in lungs of bats from Brazil by PCR amplification

2009 ◽  
Vol 29 (6) ◽  
pp. 469-473 ◽  
Author(s):  
Edna Maria Cavallini Sanches ◽  
Susi M. Pacheco ◽  
Alison S. Cericatto ◽  
Rosane M. Melo ◽  
Edson Molleta Colodel ◽  
...  
Keyword(s):  
Nested Pcr ◽  
Urban Areas ◽  
Pcr Amplification ◽  
Small Subunit ◽  
Rrna Gene ◽  
Wild Animals ◽  
Tadarida Brasiliensis ◽  
Desmodus Rotundus ◽  
Mato Grosso ◽  
Wide Range

Pneumocystis has been isolated from a wide range of unrelated mammalian hosts, including humans, domestic and wild animals. It has been demonstrated that the genome of Pneumocystis of one host differs markedly from that of other hosts. Also, variation in the chromosome and DNA sequence of Pneumocystis within a single host species has been observed. Since information about the occurrence and nature of infections in wild animals is still limited, the objective of this work was to detect the presence of Pneumocystis sp. in lungs of bats from two states from Brazil by Nested-PCR amplification. The bats, captured in caves and in urban areas, were obtained from the Program of Rabies Control of two States in Brazil, Mato Grosso and Rio Grande do Sul, located in the Mid-Western and Southern regions of the country, respectively. DNAs were extracted from 102 lung tissues and screened for Pneumocystis by nested PCR at the mtLSU rRNA gene and small subunit of mitochondrial ribosomal RNA (mtSSU rRNA). Gene amplification was performed using the mtLSU rRNA, the primer set pAZ102H - pAZ102E and pAZ102X - pAZY, and the mtSSU rRNA primer set pAZ102 10FRI - pAZ102 10R-RI and pAZ102 13RI - pAZ102 14RI. The most frequent bats were Tadarida brasiliensis (25), Desmodus rotundus (20), and Nyctinomops laticaudatus (19). Pneumocystis was more prevalent in the species Nyctinomops laticaudatus (26.3% = 5/19), Tadarida brasiliensis (24% = 6/25), and Desmodus rotundus (20% = 4/20). Besides these species, Pneumocystis also was detected in lungs from Molossus molossus (1/11, 9.1%), Artibeus fimbriatus (1/1, 100%), Sturnira lilium (1/3, 33.3%), Myotis levis (2/3, 66.7%)and Diphylla ecaudata (1/2, 50%). PCR products which could indicate the presence of Pneumocystis (21.56%) were identified in DNA samples obtained from 8 out of 16 classified species from both states (5 bats were not identified). This is the first report of detection of Pneumocystis in bats from Brazil.

Sessile drop profiles: corrected methods for surface tension and spreading coefficients

1972 ◽  
Vol 330 (1583) ◽  
pp. 561-572 ◽  
Keyword(s):  
Surface Tension ◽  
Drop Size ◽  
Sessile Drop ◽  
Graphical Form ◽  
Drop Diameter ◽  
Maximum Height ◽  
Drop Height ◽  
Wide Range ◽  
Spreading Coefficients ◽  
Limiting Value

The height of a sessile drop first increases as the drop size increases and then diminishes to a limiting value for very large drops. The variation of sessile drop height with drop size has been calculated and is given in graphical form for a very wide range of drop size and of contact angle. These data are then used to derive correction factors so that the surface tension and the spreading coefficient may be obtained from equations which would normally apply with the limiting drop height. A comparison is made of these data with some empirical equations, developed by earlier workers, to express the drop height as a function of its size. It is shown that these equations apply over limited ranges of size only. The phenomenon of a sessile drop possessing some maximum height is shown to be a consequence of the capillary pressure at the apex changing with drop diameter in a different way from that at the base of the drop.

Preservation of beluga (Delphinapterus leucas) spermatozoa using a trehalose-based cryodiluent and directional freezing technology

2010 ◽  
Vol 22 (4) ◽  
pp. 653 ◽  
Author(s):  
J. K. O'Brien ◽  
T. R. Robeck
Keyword(s):  
Freezing Rate ◽  
Slow Freezing ◽  
Delphinapterus Leucas ◽  
Freezing Method ◽  
Progressive Motility ◽  
Sperm Characteristics ◽  
Preservation Method ◽  
Systematic Development ◽  
Directional Freezing

A beluga (Delphinapterus leucas) sperm preservation method was developed for use in genome banking and AI. In Study 1, glycerol-based cryodiluents (modified BF5F and modified Platz Diluent Variant (PDV)) were unable to maintain adequate progressive motility using straws (fast and slow freezing rate (FR)) or pellets (slow FR). Neither freezing method nor FR affected in vitro sperm characteristics (P > 0.05), but retention of prefreeze progressive motility following thawing was greater (P < 0.05) for BF5F (21%) than PDV (15%). In Study 2, examining the effects of straw freeze–thawing using BF5F with glycerol (1 and 3%, v/v) or trehalose (46 and 91 mM) on sperm characteristics, samples cryopreserved in trehalose exhibited superior (P < 0.05) in vitro parameters compared with their glycerol-treated counterparts. In Study 3, compared with a straw method, directional freezing using 91 mM trehalose enhanced (P < 0.05) sperm characteristics, with samples retaining 38%, 75% and 61% of their prefreeze progressive motility, curvilinear velocity and viability, respectively. A higher (P < 0.05) proportion of motile spermatozoa displayed rapid velocity after directional (21 ± 1%) compared with straw (12 ± 3%) freezing. Systematic development of a cryodiluent and the use of directional freezing resulted in beluga spermatozoa exhibiting adequate post-thaw quality for genome banking and use in AI.

scholarly journals Metal-Free Polymerizations of Microencapsulated Activated Alkynes for Autonomous Damage Visualization of Polymers

2021 ◽  
Author(s):  
Ting Han ◽  
Shusheng Chen ◽  
Xinnan Wang ◽  
Xinyao Fu ◽  
Haifei Wen ◽  
...  
Keyword(s):  
Composite Film ◽  
Polymer Film ◽  
Chemical Reactions ◽  
Mechanical Damage ◽  
Metal Free ◽  
Turn On ◽  
Wide Range ◽  
Additional Protection ◽  
Activated Alkynes ◽  
Damage Visualization

The development of autonomous materials with desired performance and built-in visualizable sensing units is of great academic and industrial significance. Although a wide range of damage indication methods have been reported, the “turn-on” sensing mechanism by damaging events based on microcapsule systems, especially those relying on chemical reactions to elicit a chromogenic response, are still very limited. Herein, a facile and metal-free polymerization route with an interesting reaction-induced coloration effect is demonstrated. Under the catalysis of 1,4-diazabicyclo[2.2.2]octane (DABCO), the polymerizations of difunctional or trifunctional activated alkynes proceed very quickly at 0 oC in air. A series of polymers composed of stereoregular enyne structure (major unit) and divinyl ether structure (minor unit) are obtained. Both the catalyst and monomers are colorless while the polymerized products are deep-colored. This process can be applied for the damage visualization of polymers using the microencapsulation technique. Microcapsules containing the reactive alkyne monomer are prepared and mixed in a DABCO-dispersed polymer film. The mechanical damage of this composite film can be readily visualized once the reaction is initiated from the ruptured microcapsules. Moreover, the newly formed polymer automatically sealed the cracks with an additional protection function.

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