Evaluation of alternative cryoprotectants for preserving stallion spermatozoa.

Although use of cryopreserved stallion spermatozoa is currently accepted by many breed registries, utilization of this technique remains limited due to poor fertility for some stallions. One reason for these results is osmotic stress that spermatozoa experiences when the cryoprotectant (glycerol) is added to the cells prior to freezing and removal from the cells after thawing. In an effort to minimize osmotic damage, alternative cryoprotectants, having lower molecular weights and greater membrane permeability than glycerol, were evaluated to determine their effectiveness for cryopreserving stallion spermatozoa. In the first experiment, equal molar concentrations of several amides were compared to determine if they could preserve the motility of sperm as well as glycerol. At 0.55 M concentration, addition of glycerol to a skim milk-egg yolk (SMEY) diluent resulted in higher percentages of motile sperm (61%) than methyl formamide (40%) or dimethyl formamide (38%, P<0.05), while formamide, acetamide, and methyl acetamide resulted in recovery of less than 20% motile cells (P<0.05). When methyl formamide or dimethyl formamide were increased to 0.6 or 0.9 M they resulted in percentages of motile cells (48-54%) similar to that achieved with glycerol (52%). Similarly, 0.9 M ethylene glycol also resulted in similar percentages of motile cells (43%). Replacing the glucose and fructose in the SMEY diluent with either raffinose or trehalose did not result in higher percentages of motile sperm (65 and 66%, respectively) than the control SMEY (63%). Similarly, addition of methyl cellulose also did not increase the percentages of motile spermatozoa in the samples, after cryopreservation (P>0.05). In conclusion, both methyl formamide and dimethyl formamide protected stallion spermatozoa from cryodamage as effectively as glycerol. Since these compounds permeate the plasma membrane more effectively than glycerol, they should cause less osmotic damage to stallion spermatozoa than glycerol. Therefore, these compounds may prove very effective in the cryopreservation of stallion spermatozoa, and may be particularly useful for spermatozoa from stallions that produce spermatozoa that have poor post-thaw characteristics when glycerol is used as the cryoprotectant.

Do graduated compression stockings and pneumatic boots have an additive effect on the peak velocity of venous blood flow?

Graduated compression stockings and intermittent pneumatic compression boots reduce the incidence of deep vein thrombosis. Recent studies suggest that the simultaneous use of these devices may have a synergistic prophylactic effect; however, conflicting reports also exist. Using duplex imaging, we analyzed the effect on peak venous velocity in the superficial femoral vein produced by the individual and simultaneous use of graduated compression stockings and intermittent pneumatic compression boots. Normal volunteers and postoperative patients were examined. The use of intermittent pneumatic compression boots significantly increased the peak venous velocity relative to rest, whereas the use of graduated compression stockings did not alter the peak venous velocity. Also, the addition of graduated compression stockings to legs already being treated with intermittent pneumatic compression boots did not produce a further augmentation of peak venous velocity. This study demonstrates that the simultaneous use of graduated compression stockings and intermittent pneumatic compression boots does not produce a synergistic augmentation of peak venous velocity in the superficial femoral vein.