The photoaffinity probe (.3'P)8-N, cAMP was used to label the cAMP binding proteins in washed eja... more The photoaffinity probe (.3'P)8-N, cAMP was used to label the cAMP binding proteins in washed ejaculated human sperm. Three saturable binding proteins werc photolabeled in both intact and disrupted cells with apparent molecular weights of 55,000, 49,000 and 40,000 daltons corresponding to the regulatory subunits of type I1 and type I CAMP-dependent protein kinase (CAMP-PK) and to an endogenous proteolytic product of the regulatory subunits, respectively. Photoincorporation in the three proteins could be totally blocked by preincubating the cells with CAMP. Cell-free seminal plasma was found to be free of detectable ("P) 8-N3 CAMP-binding proteins. The 8-N., CAMP was also eflective in stimulating endogenous CAMP-PK activity in intact and disrupted sperm. A substantial amount of ("P) 8-N, cA.MP binding to types I and I1 regulatory subunits and CAMP-PK activity was detected on washed intact cells. Intact cells bound I .80 pmol of (."P) 8-N, cAMP/mg protein and had CAMP-PK activity of 824 units/lO" cells. Disrupted cells bound 3.95 pmol ("P) 8-N., cAMP/mg protein and had a CAMP-PK activity of 2,206 units/lV cells. The data presented support the concept of two classes of CAMP receptors being differentially availablc to cxternally added ("P) 8-N, cAMP and protcases. Cellular membrane integrity and membranc sidcdncss are discussed as possiblc cxplanations for thc observation reported.
Aquatic ecosystems are influenced in a hierarchical fashion by the climate and landform in which ... more Aquatic ecosystems are influenced in a hierarchical fashion by the climate and landform in which they are embedded, by land use and land cover in the catchment and the immediate vicinity, and by ecosystem-scale factors. Quantifying organismal and ecosystem responses to the multiple and interacting effects of human activities requires a multi-pronged approach. We have investigated the effects of land management and climate change on wetland ecosystems, amphibian community, and organismal health using such an approach. Data ...
EPA Agreement Number: RD-83087901The prairie potholes wetlands of the Great Plains comprise some ... more EPA Agreement Number: RD-83087901The prairie potholes wetlands of the Great Plains comprise some of the most ecologically valuable freshwater resources of the nation, but they are also exceptionally vulnerable to anthropogenic stressors, particularly those associated with agricultural land use practices. They are also considered likely to be severely impacted by climate change. In this study we have quantified relationships among stressors associated with climate, agricultural land use and amphibian communities throughout much of the prairie pothole region
Collaborators: Jeff Hanson, Brandon Hanson, Stephanie Hanson, Michael Sadowsky, Randall Hicks, Da... more Collaborators: Jeff Hanson, Brandon Hanson, Stephanie Hanson, Michael Sadowsky, Randall Hicks, Daniel Jones, Tina Loesekann, Siqian Huang, Whitney Scherkenbach, Thomas Ferguson, Monica Haynes, Gina Chiodi Grensing, Travis Eisenbacher, Andrew Burke, Karen Haedtke, and Oksana Kolomitsyna
Life cycle assessment (LCA) is a well-established tool for measuring environmental effects of exi... more Life cycle assessment (LCA) is a well-established tool for measuring environmental effects of existing technology. While the most recent LCA research has focused on environmental impacts, in particular on the effects of climate change, there is growing interest in how LCA can be used prospectively. A 2019 workshop in Duluth, Minnesota sought to define the needs and priorities of prospective life cycle assessment from a perspective that considers diverse viewpoints. In that workshop, participants outlined frameworks for how sustainability impacts might figure into a prospective LCA tool focused on assessing technologies currently under development. Those frameworks included social and economic impacts, which were characterized alongside environmental impacts, with the goal of predicting potential impacts and developing recommendations for improving technologies. Cultural perspective, in particular the roots of the German circular economy, was explored and held up as a reminder that d...
Environmental toxicology and chemistry, Jan 26, 2017
Testicular oocytes (TOs) have been found in black basses (Micropterus spp.) from many locations i... more Testicular oocytes (TOs) have been found in black basses (Micropterus spp.) from many locations in North America. The presence of TOs is often assumed to imply exposure to estrogenic endocrine disrupting compounds (EDCs), however, a definitive causal relationship has yet to be established, and TO prevalence is not consistently low in fish from areas lacking evident EDC sources. This might indicate any of a number of situations: (a) unknown or unidentified EDCs or EDC sources, (b) induction of TOs by other stressors, or (c) TOs occurring spontaneously during normal development. In the present study we analyzed TO occurrence in smallmouth bass (M. dolomieu) from eight populations in Northeastern Minnesota watersheds with differing degrees of human development and hence, presumed likelihood of exposure to anthropogenic chemicals. Three watersheds were categorized as moderately developed, based on the presence of municipal wastewater discharges and higher human population density (4-81 ...
Plasma membrane vesicles isolated from bovine epididymal and ejaculated spermatozoa have widely d... more Plasma membrane vesicles isolated from bovine epididymal and ejaculated spermatozoa have widely different capabilities for transporting Ca2+. Spermatozoa were ruptured by nitrogen cavitation, and the plasma membrane fraction was harvested after low speed and sucrose gradient centrifugation; purity was assessed by marker enzyme analyses, electron microscopy, and sedimentation properties. Plasma membrane vesicles isolated from epididymal sperm accumulate Ca2+ passively at a faster rate and to a greater extent than vesicles prepared from ejaculated sperm. Ca2+ transport across bovine sperm plasma membranes is an ATP-independent, Na+-dependent process that obligatorily exchanges intravesicular Na+ for external Ca2+. The rate of Na+/Ca2+ exchange is significantly lower in ejaculated sperm vesicles than in those of epididymal sperm. Bovine plasma membranes contain little or no Ca2+-dependent ATPase activity. It is suggested that, at the time of ejaculation, calcium flux into bovine sperm ...
Treatment of washed, ejaculated bovine sperm with 30 mM sodium fluoride immoblized the cells in a... more Treatment of washed, ejaculated bovine sperm with 30 mM sodium fluoride immoblized the cells in a characteristically rigid form. In cells metabolizing endogenous substrates, fluoride decreased respiration by about
Global amphibian declines have often been attributed to disease 1, 2, but ignorance of the relati... more Global amphibian declines have often been attributed to disease 1, 2, but ignorance of the relative importance and mode of action of potential drivers of infection has made it difficult to develop effective remediation. In a field study, here we show that the widely used herbicide, atrazine, was the best predictor (out of more than 240 plausible candidates) of the abundance of larval trematodes (parasitic flatworms) in the declining northern leopard frog Rana pipiens. The effects of atrazine were consistent across ...
Simple media were developed to study the metabolic requirements of bovine embryos up to Day 7 (Da... more Simple media were developed to study the metabolic requirements of bovine embryos up to Day 7 (Day 0 = day of oocyte aspiration) in vitro. Embryos were derived from oocytes matured and fertilized in vitro. At 45 ± 2 h post insemination, embryos (-2 cells) were randomly allotted to treatments. Examined in experiments 1 and 3 was the effect of pyruvate concentration in the presence of lactate. In the presence of lactate, pyruvate (0.2-5.0 mM) had no effect (p > 0.05) on the percentage of morulae or blastocysts. However, increasing the concentration of hemicalcium L-lactate from 5 mM to 10 mM decreased (p < 0.001 ) the percentage of embryos reaching the morula or blastocyst stage (experiment 3). Neither magnesium sulfate (0.5 mM) nor EDTA (10 mM) improved embryo development when added to the medium CRI (experiment 2). Increasing the calcium level to 5 mM or the lactate level to 10 mM had no effect (p > 0.05) on embryo development (experiment 4). However, the interaction of adding calcium and lactate resulted in a decreased (p < 0.05) percentage of morulae. Determined in experiment 6 were the independent effects of pyruvate, lactate, and glucose on embryo development in vitro. As pyruvate or lactate level was increased from 1 to 10 mM, the percentage of blastocysts was decreased (p < 0.05). These experiments indicate that adding pyruvate to a medium containing lactate is not necessary for development of bovine embryos in vitro.
Bovine sperm that were subjected to extended anoxia (2.5 h) in the absence of glycolytic substrat... more Bovine sperm that were subjected to extended anoxia (2.5 h) in the absence of glycolytic substrates then diluted into oxygenated medium were immotile but metabolically active, producing ATP from lactate via oxidative phosphorylation. In response to anoxia sperm ATP titers dropped from 15-20 mumoles/10(8) cells to 1-2 mumoles/10(8) cells in the first 5 min then remained extremely low until reoxygenation. Cyclic AMP titers declined slowly over the anoxic period, but did not show the same scale of depression as ATP. After dilution and re-oxygenation ATP recovered to pre-anoxia levels within 1 min, and cAMP rose to about the pre-anoxia levels. However, motility, which varied quantitatively and qualitatively between ejaculates prior to anoxic treatment, was substantially depressed after extended anoxia in all cases; progressive motility was almost non-existent in post-anoxic sperm. Addition of isobutylmethylxanthine or Cibacron Blue F3GA, both putative phosphodiesterase inhibitors, stimu...
Adenylate kinase (ATP:AMP phosphotransferase, EC 2.7.4.3) activity was detected in the flagella o... more Adenylate kinase (ATP:AMP phosphotransferase, EC 2.7.4.3) activity was detected in the flagella of ejaculated bovine spermatozoa. This activity provided sufficient ATP to produce normal motility in cells permeabilized with digitonin and treated with 0.5 mM MgADP. In the presence of ADP, adenylate kinase activity was inhibited by P1,P5-di(adenosine 5')-pentaphosphate (Ap5A), an adenylate kinase-specific inhibitor, and motility was stopped. ATP-supported motility was not affected by Ap5A. Mitochondrial adenylate kinase activity allowed AMP to stimulate respiration in permeabilized sperm. Adenylate kinase activity in tail fragments was most active in a pH range from 7.6 to 8.4, and a similar pH sensitivity was observed for this enzyme activity in a hypotonic extract of whole sperm. The apparent km of adenylate kinase activity in permeabilized tail fragments was about 1.0 mM ADP in the direction of ATP synthesis. The fluctuation of nucleotide concentrations in normal and metabolical...
Methoprene (isopropyl (2E,4E)-11-methoxy-3,7,11-trimethyl-2,4-dodecadienoate) is an insect juveni... more Methoprene (isopropyl (2E,4E)-11-methoxy-3,7,11-trimethyl-2,4-dodecadienoate) is an insect juvenile hormone agonist that blocks metamorphosis in some insects. Recent evidence suggests that a metabolite, methoprene acid, activates vertebrate retinoid X receptors (RXRs), and may interfere with retinoic acid-regulated developmental processes. Methoprene, methoxy-methoprene acid, and two major breakdown products were tested for their ability to interfere with retinoid-regulated pathways when using transfected cells. The CV-1 cells were transiently transfected with genes encoding RXRs and response elements attached to luciferase reporters, and retinoic acid-sensitive F9 cells were stably transfected with retinoic acid receptor (RAR)/RXR response elements attached a lacZ reporter (Sil-REM/beta-gal-NEO). Experiments confirmed that methoxy-methoprene acid acted as a ligand for RXRs and was capable of activating transcription through RAR/RXR response elements. However, neither methoprene nor the breakdown products, 7-methoxycitronellal and 7-methoxycitronellic acid, activated transcription in transfected CV-1 or F9 cells. Methoprene and methoxy-methoprene acid may interfere with the conversion of all-trans-retinol and all-trans-retinaldehyde to all-trans-retinoic acid in the F9-derived cell line. Methoprene was as effective as the retinol dehydrogenase inhibitor citral in blocking the retinol-induced transcription of RAR/RXR-regulated reporter genes, whereas methoxy-methoprene acid blocked transcription stimulated by retinaldehyde.
Bovine sperm motility and respiration were stimulated by the triazine dye Cibacron Blue F3GA (CB)... more Bovine sperm motility and respiration were stimulated by the triazine dye Cibacron Blue F3GA (CB), which may operate as a nucleotide mimic. CB stimulation of respiration was half-maximal at about 35 microM and respiration reached maximal levels about 1.5 minutes after CB addition. Respiratory stimulation was preceded by a transient increase in cytosolic cAMP. Sperm cAMP titers were elevated from 5 to 10 pmoles/10(8) cells within 30 seconds of CB addition, but rapidly dropped to a stable level of about 7.5 pmoles/10(8) cells. CB was a potent inhibitor of sperm membrane adenylyl cyclase and inhibited respiration in permeabilized cells. Taken together, the data indicated that CB stimulation was not manifested via the cytosol. In addition, a nonpermeant blue dextran preparation synthesized with CB also stimulated sperm respiration and motility. CB inhibited sperm membrane phosphodiesterase activity, suggesting that the transient pulse of cAMP resulted from CB interaction with this enzyme in the sperm membrane.
The photoaffinity probe (.3'P)8-N, cAMP was used to label the cAMP binding proteins in washed eja... more The photoaffinity probe (.3'P)8-N, cAMP was used to label the cAMP binding proteins in washed ejaculated human sperm. Three saturable binding proteins werc photolabeled in both intact and disrupted cells with apparent molecular weights of 55,000, 49,000 and 40,000 daltons corresponding to the regulatory subunits of type I1 and type I CAMP-dependent protein kinase (CAMP-PK) and to an endogenous proteolytic product of the regulatory subunits, respectively. Photoincorporation in the three proteins could be totally blocked by preincubating the cells with CAMP. Cell-free seminal plasma was found to be free of detectable ("P) 8-N3 CAMP-binding proteins. The 8-N., CAMP was also eflective in stimulating endogenous CAMP-PK activity in intact and disrupted sperm. A substantial amount of ("P) 8-N, cA.MP binding to types I and I1 regulatory subunits and CAMP-PK activity was detected on washed intact cells. Intact cells bound I .80 pmol of (."P) 8-N, cAMP/mg protein and had CAMP-PK activity of 824 units/lO" cells. Disrupted cells bound 3.95 pmol ("P) 8-N., cAMP/mg protein and had a CAMP-PK activity of 2,206 units/lV cells. The data presented support the concept of two classes of CAMP receptors being differentially availablc to cxternally added ("P) 8-N, cAMP and protcases. Cellular membrane integrity and membranc sidcdncss are discussed as possiblc cxplanations for thc observation reported.
Aquatic ecosystems are influenced in a hierarchical fashion by the climate and landform in which ... more Aquatic ecosystems are influenced in a hierarchical fashion by the climate and landform in which they are embedded, by land use and land cover in the catchment and the immediate vicinity, and by ecosystem-scale factors. Quantifying organismal and ecosystem responses to the multiple and interacting effects of human activities requires a multi-pronged approach. We have investigated the effects of land management and climate change on wetland ecosystems, amphibian community, and organismal health using such an approach. Data ...
EPA Agreement Number: RD-83087901The prairie potholes wetlands of the Great Plains comprise some ... more EPA Agreement Number: RD-83087901The prairie potholes wetlands of the Great Plains comprise some of the most ecologically valuable freshwater resources of the nation, but they are also exceptionally vulnerable to anthropogenic stressors, particularly those associated with agricultural land use practices. They are also considered likely to be severely impacted by climate change. In this study we have quantified relationships among stressors associated with climate, agricultural land use and amphibian communities throughout much of the prairie pothole region
Collaborators: Jeff Hanson, Brandon Hanson, Stephanie Hanson, Michael Sadowsky, Randall Hicks, Da... more Collaborators: Jeff Hanson, Brandon Hanson, Stephanie Hanson, Michael Sadowsky, Randall Hicks, Daniel Jones, Tina Loesekann, Siqian Huang, Whitney Scherkenbach, Thomas Ferguson, Monica Haynes, Gina Chiodi Grensing, Travis Eisenbacher, Andrew Burke, Karen Haedtke, and Oksana Kolomitsyna
Life cycle assessment (LCA) is a well-established tool for measuring environmental effects of exi... more Life cycle assessment (LCA) is a well-established tool for measuring environmental effects of existing technology. While the most recent LCA research has focused on environmental impacts, in particular on the effects of climate change, there is growing interest in how LCA can be used prospectively. A 2019 workshop in Duluth, Minnesota sought to define the needs and priorities of prospective life cycle assessment from a perspective that considers diverse viewpoints. In that workshop, participants outlined frameworks for how sustainability impacts might figure into a prospective LCA tool focused on assessing technologies currently under development. Those frameworks included social and economic impacts, which were characterized alongside environmental impacts, with the goal of predicting potential impacts and developing recommendations for improving technologies. Cultural perspective, in particular the roots of the German circular economy, was explored and held up as a reminder that d...
Environmental toxicology and chemistry, Jan 26, 2017
Testicular oocytes (TOs) have been found in black basses (Micropterus spp.) from many locations i... more Testicular oocytes (TOs) have been found in black basses (Micropterus spp.) from many locations in North America. The presence of TOs is often assumed to imply exposure to estrogenic endocrine disrupting compounds (EDCs), however, a definitive causal relationship has yet to be established, and TO prevalence is not consistently low in fish from areas lacking evident EDC sources. This might indicate any of a number of situations: (a) unknown or unidentified EDCs or EDC sources, (b) induction of TOs by other stressors, or (c) TOs occurring spontaneously during normal development. In the present study we analyzed TO occurrence in smallmouth bass (M. dolomieu) from eight populations in Northeastern Minnesota watersheds with differing degrees of human development and hence, presumed likelihood of exposure to anthropogenic chemicals. Three watersheds were categorized as moderately developed, based on the presence of municipal wastewater discharges and higher human population density (4-81 ...
Plasma membrane vesicles isolated from bovine epididymal and ejaculated spermatozoa have widely d... more Plasma membrane vesicles isolated from bovine epididymal and ejaculated spermatozoa have widely different capabilities for transporting Ca2+. Spermatozoa were ruptured by nitrogen cavitation, and the plasma membrane fraction was harvested after low speed and sucrose gradient centrifugation; purity was assessed by marker enzyme analyses, electron microscopy, and sedimentation properties. Plasma membrane vesicles isolated from epididymal sperm accumulate Ca2+ passively at a faster rate and to a greater extent than vesicles prepared from ejaculated sperm. Ca2+ transport across bovine sperm plasma membranes is an ATP-independent, Na+-dependent process that obligatorily exchanges intravesicular Na+ for external Ca2+. The rate of Na+/Ca2+ exchange is significantly lower in ejaculated sperm vesicles than in those of epididymal sperm. Bovine plasma membranes contain little or no Ca2+-dependent ATPase activity. It is suggested that, at the time of ejaculation, calcium flux into bovine sperm ...
Treatment of washed, ejaculated bovine sperm with 30 mM sodium fluoride immoblized the cells in a... more Treatment of washed, ejaculated bovine sperm with 30 mM sodium fluoride immoblized the cells in a characteristically rigid form. In cells metabolizing endogenous substrates, fluoride decreased respiration by about
Global amphibian declines have often been attributed to disease 1, 2, but ignorance of the relati... more Global amphibian declines have often been attributed to disease 1, 2, but ignorance of the relative importance and mode of action of potential drivers of infection has made it difficult to develop effective remediation. In a field study, here we show that the widely used herbicide, atrazine, was the best predictor (out of more than 240 plausible candidates) of the abundance of larval trematodes (parasitic flatworms) in the declining northern leopard frog Rana pipiens. The effects of atrazine were consistent across ...
Simple media were developed to study the metabolic requirements of bovine embryos up to Day 7 (Da... more Simple media were developed to study the metabolic requirements of bovine embryos up to Day 7 (Day 0 = day of oocyte aspiration) in vitro. Embryos were derived from oocytes matured and fertilized in vitro. At 45 ± 2 h post insemination, embryos (-2 cells) were randomly allotted to treatments. Examined in experiments 1 and 3 was the effect of pyruvate concentration in the presence of lactate. In the presence of lactate, pyruvate (0.2-5.0 mM) had no effect (p > 0.05) on the percentage of morulae or blastocysts. However, increasing the concentration of hemicalcium L-lactate from 5 mM to 10 mM decreased (p < 0.001 ) the percentage of embryos reaching the morula or blastocyst stage (experiment 3). Neither magnesium sulfate (0.5 mM) nor EDTA (10 mM) improved embryo development when added to the medium CRI (experiment 2). Increasing the calcium level to 5 mM or the lactate level to 10 mM had no effect (p > 0.05) on embryo development (experiment 4). However, the interaction of adding calcium and lactate resulted in a decreased (p < 0.05) percentage of morulae. Determined in experiment 6 were the independent effects of pyruvate, lactate, and glucose on embryo development in vitro. As pyruvate or lactate level was increased from 1 to 10 mM, the percentage of blastocysts was decreased (p < 0.05). These experiments indicate that adding pyruvate to a medium containing lactate is not necessary for development of bovine embryos in vitro.
Bovine sperm that were subjected to extended anoxia (2.5 h) in the absence of glycolytic substrat... more Bovine sperm that were subjected to extended anoxia (2.5 h) in the absence of glycolytic substrates then diluted into oxygenated medium were immotile but metabolically active, producing ATP from lactate via oxidative phosphorylation. In response to anoxia sperm ATP titers dropped from 15-20 mumoles/10(8) cells to 1-2 mumoles/10(8) cells in the first 5 min then remained extremely low until reoxygenation. Cyclic AMP titers declined slowly over the anoxic period, but did not show the same scale of depression as ATP. After dilution and re-oxygenation ATP recovered to pre-anoxia levels within 1 min, and cAMP rose to about the pre-anoxia levels. However, motility, which varied quantitatively and qualitatively between ejaculates prior to anoxic treatment, was substantially depressed after extended anoxia in all cases; progressive motility was almost non-existent in post-anoxic sperm. Addition of isobutylmethylxanthine or Cibacron Blue F3GA, both putative phosphodiesterase inhibitors, stimu...
Adenylate kinase (ATP:AMP phosphotransferase, EC 2.7.4.3) activity was detected in the flagella o... more Adenylate kinase (ATP:AMP phosphotransferase, EC 2.7.4.3) activity was detected in the flagella of ejaculated bovine spermatozoa. This activity provided sufficient ATP to produce normal motility in cells permeabilized with digitonin and treated with 0.5 mM MgADP. In the presence of ADP, adenylate kinase activity was inhibited by P1,P5-di(adenosine 5')-pentaphosphate (Ap5A), an adenylate kinase-specific inhibitor, and motility was stopped. ATP-supported motility was not affected by Ap5A. Mitochondrial adenylate kinase activity allowed AMP to stimulate respiration in permeabilized sperm. Adenylate kinase activity in tail fragments was most active in a pH range from 7.6 to 8.4, and a similar pH sensitivity was observed for this enzyme activity in a hypotonic extract of whole sperm. The apparent km of adenylate kinase activity in permeabilized tail fragments was about 1.0 mM ADP in the direction of ATP synthesis. The fluctuation of nucleotide concentrations in normal and metabolical...
Methoprene (isopropyl (2E,4E)-11-methoxy-3,7,11-trimethyl-2,4-dodecadienoate) is an insect juveni... more Methoprene (isopropyl (2E,4E)-11-methoxy-3,7,11-trimethyl-2,4-dodecadienoate) is an insect juvenile hormone agonist that blocks metamorphosis in some insects. Recent evidence suggests that a metabolite, methoprene acid, activates vertebrate retinoid X receptors (RXRs), and may interfere with retinoic acid-regulated developmental processes. Methoprene, methoxy-methoprene acid, and two major breakdown products were tested for their ability to interfere with retinoid-regulated pathways when using transfected cells. The CV-1 cells were transiently transfected with genes encoding RXRs and response elements attached to luciferase reporters, and retinoic acid-sensitive F9 cells were stably transfected with retinoic acid receptor (RAR)/RXR response elements attached a lacZ reporter (Sil-REM/beta-gal-NEO). Experiments confirmed that methoxy-methoprene acid acted as a ligand for RXRs and was capable of activating transcription through RAR/RXR response elements. However, neither methoprene nor the breakdown products, 7-methoxycitronellal and 7-methoxycitronellic acid, activated transcription in transfected CV-1 or F9 cells. Methoprene and methoxy-methoprene acid may interfere with the conversion of all-trans-retinol and all-trans-retinaldehyde to all-trans-retinoic acid in the F9-derived cell line. Methoprene was as effective as the retinol dehydrogenase inhibitor citral in blocking the retinol-induced transcription of RAR/RXR-regulated reporter genes, whereas methoxy-methoprene acid blocked transcription stimulated by retinaldehyde.
Bovine sperm motility and respiration were stimulated by the triazine dye Cibacron Blue F3GA (CB)... more Bovine sperm motility and respiration were stimulated by the triazine dye Cibacron Blue F3GA (CB), which may operate as a nucleotide mimic. CB stimulation of respiration was half-maximal at about 35 microM and respiration reached maximal levels about 1.5 minutes after CB addition. Respiratory stimulation was preceded by a transient increase in cytosolic cAMP. Sperm cAMP titers were elevated from 5 to 10 pmoles/10(8) cells within 30 seconds of CB addition, but rapidly dropped to a stable level of about 7.5 pmoles/10(8) cells. CB was a potent inhibitor of sperm membrane adenylyl cyclase and inhibited respiration in permeabilized cells. Taken together, the data indicated that CB stimulation was not manifested via the cytosol. In addition, a nonpermeant blue dextran preparation synthesized with CB also stimulated sperm respiration and motility. CB inhibited sperm membrane phosphodiesterase activity, suggesting that the transient pulse of cAMP resulted from CB interaction with this enzyme in the sperm membrane.
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Papers by Patrick Schoff