The effect of two packaging systems on the post-thaw characteristics of canine sperm

The aim of this study was to compare the effect of different packaging systems on some parameters of cryopreserved canine spermatozoa. The experimental material consisted of the sperm-rich fractions of ejaculates collected from four Beagle dogs. Semen samples for cryopreservation were stored in 0.25 ml plastic straws and two aluminum tubes with a total volume of 5.0 ml. Semen was frozen in static nitrogen vapor for 10 minutes (0.25 ml straws) or 15 and 20 minutes (aluminum tubes). Post-thaw assessments involved the determination of sperm motility parameters using a computer assisted sperm analyzer (CASA), sperm plasma membrane integrity (SPMI), mitochondrial membrane potential (MMP) and acrosome integrity (normal apical ridge, NAR). Regardless of the packaging system applied, no significant differences in total sperm motility (TMOT) or selected kinematic parameters were observed after freezing-thawing. However, spermatozoa frozen in 0.25 mL straws were characterized by improved functionality, in particular mitochondrial function, after thawing. The results indicate that large quantities of canine semen can be frozen in aluminum tubes. Further studies are required, however, to evaluate different freezing and thawing rates of aluminum tubes

Int. J. Cancer

Advanced and recurrent prostate tumors contain elevated levels of activated extracellular signal-regulated kinases I and 2 (ERK) in comparison to early-stage or benign specimens, and inhibition of ERK activation attenuates growth factor-dependent proliferation of prostate cells, suggesting a potential regulatory role for ERK in prostate tumorigenesis. Factors responsible for ERK activation in prostate cells are not well defined. Here, we show positive cooperative interaction between the G protein-coupled lysophosphatidic acid (LPA) and tyrosine kinase epidermal growth factor (EGF) receptors in androgen- insensitive prostate cancer PC-3 cells. Pre-treatment of the PC-3 cells with LPA decreases the dose of EGF required to elicit maximal activation of EGFR. Furthermore, treatment with LPA alone induces the rapid (maximal signal within 2 min) tyrosine phosphorylation of EGFR, and subsequent (maximal signal after 5 min) activation of ERK, suggesting that EGFR activation precedes ERK phosphorylation and may constitute a required component for signal relay from the LPA receptor to ERK. Accordingly, we show that inhibition of EGFR kinase activity attenuates the LPA-regulated ERK activation. In addition, we find that the LPA-regulated tyrosine phosphorylation of EGFR and activation of ERK are attenuated by batimastat, a generic inhibitor of matrix metalloproteinases (MMP). However, unlike the situation in fibroblasts, we find that the LPA-induced transactivation of EGFR in PC-3 cells is not mediated by shedding of heparin-binding EGF. Together, our data show that LPA and EGF cooperate to induce mitogenic signaling in prostate cancer cells in an MMP-regulated activation of the ERK pathway. (C) 2002 Wiley-Liss, Inc

Lysophosphatidic acid-regulated mitogenic ERK signaling in androgen-insensitive prostate cancer PC-3 cells

Advanced and recurrent prostate tumors contain elevated levels of activated extracellular signal-regulated kinases I and 2 (ERK) in comparison to early-stage or benign specimens, and inhibition of ERK activation attenuates growth factor-dependent proliferation of prostate cells, suggesting a potential regulatory role for ERK in prostate tumorigenesis. Factors responsible for ERK activation in prostate cells are not well defined. Here, we show positive cooperative interaction between the G protein-coupled lysophosphatidic acid (LPA) and tyrosine kinase epidermal growth factor (EGF) receptors in androgen- insensitive prostate cancer PC-3 cells. Pre-treatment of the PC-3 cells with LPA decreases the dose of EGF required to elicit maximal activation of EGFR. Furthermore, treatment with LPA alone induces the rapid (maximal signal within 2 min) tyrosine phosphorylation of EGFR, and subsequent (maximal signal after 5 min) activation of ERK, suggesting that EGFR activation precedes ERK phosphorylation and may constitute a required component for signal relay from the LPA receptor to ERK. Accordingly, we show that inhibition of EGFR kinase activity attenuates the LPA-regulated ERK activation. In addition, we find that the LPA-regulated tyrosine phosphorylation of EGFR and activation of ERK are attenuated by batimastat, a generic inhibitor of matrix metalloproteinases (MMP). However, unlike the situation in fibroblasts, we find that the LPA-induced transactivation of EGFR in PC-3 cells is not mediated by shedding of heparin-binding EGF. Together, our data show that LPA and EGF cooperate to induce mitogenic signaling in prostate cancer cells in an MMP-regulated activation of the ERK pathway. (C) 2002 Wiley-Liss, Inc