Cold-acclimated twigs of Amelanchier alnifolia Nutt. released less HCN at -4.5 C than nonacclimated twigs following slow freezing to -25 C or rapid freezing to -78 C. Cold-acclimated twigs frozen slowly to -25 C released more HCN than cold-acclimated twigs frozen only to -4.5 C. Cold-acclimated twigs frozen slowly to -25 C and then rapidly to -78 C released less HCN at -4.5 C than cold-acclimat...

The relationship between freezing rate, ultrastructure and recovery in a human diploid cell line has been studied by freezing cells at rates that are known to give high and low recoveries and examining them immediately after thawing. Some correlation was found between structural damage and recovery. The main types of damage observed were loss of cytoplasm and nucleoplasm, indicating disruption ...

Spermatocytogenesis starts from lumens of seminiferous cords and after migration to the basal membrane ends to the lumens again. We attempt to review the protective effects of melatonin and ghrelin on Spermatocytogenesis and in particular on spermatogonial stem cells, as two rather newly-discovered hormones. Testicular freezing prior to chemotherapy and radiotherapy is one of the ways of preser...

Laboratory experiments show that undercooling to about -5 degrees C occurs in colonized Beacon sandstones of the Ross Desert, Antarctica. High-frequency temperature oscillations between 5 degrees C and -5 degrees C or -10 degrees C (which occur in nature on the rock surface) did not damage Hemichloris antarctica. In a cryomicroscope, H. antarctica appeared to be undamaged after slow or rapid ...

Germinating conidiospores of Neurospora crassa that were exposed to 45 degrees C, a temperature that induces a heat shock response, were protected from injury caused by freezing in liquid nitrogen and subsequent thawing at 0 degrees C. Whereas up to 90% of the control spores were killed by this freezing and slow thawing, a prior heat shock increased cell survival four- to fivefold. Survival was...

Three ejaculates were collected from each of five dogs. After initial evaluation, the sperm-rich fractions were diluted to 100 x 10(6) spermatozoa x mL(-1) in two steps with an egg yolk-TRIS extender containing a final concentration of 5% glycerol and 0.5% Equex STM paste. Half of the 0.5 mL straws obtained from each ejaculate were frozen on nitrogen vapours (4 cm above the liquid surface) ("ra...

The fact that freezing caused marked changes in oxidative activity of tissues was of comparatively little interest until it became apparent that most if not all the enzymatic activities of cells could be reproduced under suitable conditions in cell-free systems. Isolated soluble enzymes were usually unaffect,ed or even stabilized by freezing, and damaging effects of freezing on other enzymes co...

Ram spermatozoa are most susceptible to damage during freezing between the temperatures of -10 degrees C and -25 degrees C. The objectives of the present study were to examine how freezing rate through this critical temperature zone affected the fertility of spermatozoa as assessed in vivo and in vitro. Semen from six adult rams was frozen at two different rates ("fast": 5 degrees C/min from +5...

Conservation of indigenous poultry species is an important part of the new Hungarian agricultural strategy. Semen cryopreservation is the most practical method for the long term storage of poultry genetic material. The objective was to compare four protocols for cryopreservation of guinea fowl sperm (slow and fast programmable, freezing in nitrogen vapor, and pellet) and three cryoprotectants (...