Biomedical subjects

Clara I Marín-Briggiler

Publications and source records attributed to Clara I Marín-Briggiler.

6 recordsLinked to original sources

PubMed2005

Evidence of the presence of calcium/calmodulin-dependent protein kinase IV in human sperm and its involvement in motility regulation.

The mechanisms involved in the regulation of mammalian sperm motility are not well understood. Calcium ions (Ca(2+)) have been suggested to play a key role in the maintenance of motility; nevertheless, how Ca(2+) modulates this process has not yet been completely characterized. Ca(2+) can bind to calmodulin and this complex regulates the activity of multiple enzymes, including Ca(2+)/calmodulin-dependent protein kinases (CaM kinases). Results from this study confirmed that the presence of Ca(2+) in the incubation medium is essential for maintaining human sperm motility. The involvement of CaM kinases in Ca(2+) regulation of human sperm motility was evaluated using specific inhibitors (KN62 and KN93) or their inactive analogues (KN04 and KN92 respectively). Sperm incubation in the presence of KN62 or KN93 led to a progressive decrease in the percentage of motile cells; in particular, incubation with KN62 also reduced sperm motility parameters. These inhibitors did not alter sperm viability, protein tyrosine phosphorylation or the follicular fluid-induced acrosome reaction; however, KN62 decreased the total amount of ATP in human sperm. Immunological studies showed that Ca(2+)/calmodulin-dependent protein kinase IV (CaMKIV) is present and localizes to the human sperm flagellum. Moreover, CaMKIV activity increases during capacitation and is inhibited in the presence of KN62. This report is the first to demonstrate the presence of CaMKIV in mammalian sperm and suggests the involvement of this kinase in the regulation of human sperm motility.

Acrosome Reaction↗

PubMed2004

Bicarbonate is required for migration of sperm epididymal protein DE (CRISP-1) to the equatorial segment and expression of rat sperm fusion ability.

Numerous studies have demonstrated that sperm capacitation is a bicarbonate-dependent process. In the rat, capacitation has not been studied as much as in other species, mainly because of the difficulties in carrying out functional assays with this animal model. In the present study, we have examined the influence of bicarbonate in the overall rat sperm capacitation process by analyzing involvement of the anion in 1) protein tyrosine phosphorylation, 2) migration of epididymal protein DE (also known as CRISP-1) from the dorsal region to the equatorial segment of the sperm head that occurs during capacitation, and 3) ability of sperm to fuse with the egg. Incubation of sperm under capacitating conditions produced a time-dependent increase in protein tyrosine phosphorylation. This phosphorylation did not occur in the absence of HCO3- and rapidly increased by either exposure of sperm to HCO3- or replacement of the anion by a cAMP analog (dibutyryl-cAMP) and a phosphodiesterase inhibitor (pentoxifylline). The absence of HCO3- also produced a significant decrease in the percentage of cells showing migration of DE to the equatorial segment. This parameter was completely restored by addition of the anion, but dibutyryl-cAMP and pentoxifylline were not sufficient to overcome the decrease in DE migration. Sperm capacitated in the absence of HCO3- were unable to penetrate zona-free eggs independent of the presence of the anion during gamete coincubation. Exposure of these sperm to bicarbonate, or replacement of the anion by dibutyryl-cAMP and pentoxifylline, only partially restored the sperm fusion ability. Altogether, these results indicate that, in addition to its influence on protein tyrosine phosphorylation, bicarbonate is required to support other rat sperm capacitation- associated events, such as migration of DE to the equatorial segment, and expression of the ability of sperm to fuse with the egg.

Animals↗

PubMed2003

Calcium requirements for human sperm function in vitro.

OBJECTIVE: To determine extracellular calcium (Ca(2+)) requirements for the maintenance of human sperm function in vitro. DESIGN: Prospective study. SETTING: Basic research laboratory. PATIENT(S): Normozoospermic volunteers provided fresh semen samples; follicular fluid (human FF) and oocytes were collected from women undergoing IVF-ET. INTERVENTION(S): Spermatozoa were incubated for </=18 hours in media containing different CaCl(2) concentrations (maximum, 2.5 mM [control]). MAIN OUTCOME MEASURES: Protein tyrosine phosphorylation patterns, development of hyperactivated motility, induction of the acrosome reaction (AR) in response to human FF, and sperm interaction with homologous zona pellucida (ZP). RESULT(S): Cells maintained for 18 hours in medium containing >/=0.1 mM of Ca(2+) were able to undergo the AR when exposed to human FF in the presence of 2.5 mM of Ca(2+). Calcium concentrations of >/=0.22 mM were sufficient to reach protein tyrosine phosphorylation levels and hyperactivated motility values similar to those of controls. Higher Ca(2+) concentrations (>/=0.58 mM) were required to produce maximum human FF-induced AR in previously capacitated cells and to obtain an adequate sperm-ZP binding. CONCLUSION(S): Different steps of the fertilization process have distinctive Ca(2+) requirements. Whereas 0.22 mM of Ca(2+) is sufficient for the development of some capacitation-related events, human FF-induced AR and sperm-ZP interaction require 0.58 mM of this cation.

Acrosome↗

PubMed2003

Modulation of human sperm function by peritoneal fluid.

OBJECTIVE: To examine the effect of peritoneal fluid on various parameters of sperm function in vitro. DESIGN: Prospective study. SETTING: Basic research laboratory. PATIENT(S): Semen samples were obtained from normozoospermic volunteers (n = 43). Peritoneal fluids were aspirated laparoscopically from women with unexplained infertility (n = 14). Follicular fluid and oocytes were collected from patients undergoing IVF-ET. INTERVENTION(S): Sperm incubated under capacitating conditions were exposed to peritoneal fluid, and functional variables were evaluated in vitro. MAIN OUTCOME MEASURE(S): Sperm viability and motility, follicular fluid and calcium ionophore-induced acrosome reactions, protein tyrosine phosphorylation, expression of D-mannose binding sites, and ability of sperm to interact with zona pellucida. RESULT(S): Exposure of sperm to peritoneal fluid for up to 6 hours did not affect sperm viability or motility. Unlike follicular fluid, peritoneal fluid did not induce the acrosome reaction. Moreover, incubation of sperm with > or =20% v/v peritoneal fluid for 1 hour prevented the follicular fluid and the ionophore-induced acrosome reaction. Although treatment with peritoneal fluid allowed protein tyrosine phosphorylation during capacitation, it resulted in a significant decrease in the expression of D-mannose binding sites and sperm-zona pellucida binding. CONCLUSION(S): Peritoneal fluid maintains sperm survival and decreases sperm ability to respond to inducers of the acrosome reaction and bind to the zona pellucida in vitro, indicating that this fluid might modulate sperm function in vivo.

Acrosome Reaction↗

PubMed2003

Effect of antisperm antibodies present in human follicular fluid upon the acrosome reaction and sperm-zona pellucida interaction.

PROBLEM: To determine the ability of IgGs isolated from follicular fluids (hFFIgGs) to induce the acrosome reaction (AR) in human spermatozoa and to inhibit sperm-zona pellucida (ZP) interaction. METHOD OF STUDY: Incubation of capacitated spermatozoa with hFFIgGs (n = 40) and assessment of their effect on the AR or hemizona (HZ) assay in a condition that allows sperm-ZP interaction, avoiding acrosomal exocytosis. RESULTS: hFFIgGs from different women varied in their ability of inducing the AR. Those hFFIgGs with the highest AR-inducing capacity evoked the exocytotic response in most of the different sperm donors tested [high Induction Frequency (IF)]. Some of these antibodies were also able of inhibiting sperm binding to ZP [low HZ Index (HZI)]. A significant correlation was found between the IF and the HZI for each hFFIgG. CONCLUSIONS: Human follicular fluid contains antibodies capable of inducing the AR and inhibiting sperm-ZP binding, suggesting that they could be directed towards ZP receptors. hFFIgGs would constitute a tool for the identification of sperm entities involved in fertilization.

Acrosome Reaction↗

PubMed2002

Effect of incubating human sperm at room temperature on capacitation-related events.

OBJECTIVE: To determine the effect of human sperm incubation at room temperature (20 degrees C) upon capacitation-related events. DESIGN: Prospective study. SETTING: Basic research laboratory. PATIENT(S): Semen samples were obtained from normozoospermic volunteers. Human follicular fluid (hFF) was collected from women undergoing assisted reproductive treatment. INTERVENTION(S): Spermatozoa were incubated for up to 18 hours at 20 degrees C and/or 37 degrees C. MAIN OUTCOME MEASURE(S): Protein tyrosine phosphorylation patterns, development of hyperactivated motility, and induction of acrosome reaction (AR) in response to hFF. RESULT(S): Spermatozoa incubated for 18 hours at 20 degrees C showed an array of tyrosine phosphorylated proteins similar to noncapacitated cells. After incubation at 20 degrees C, the percentage of spermatozoa displaying hyperactivated motility and undergoing acrosomal loss in response to hFF was significantly lower when compared with cells kept the same time at 37 degrees C. Conversely, spermatozoa incubated overnight at 37 degrees C could respond to hFF, either at 37 degrees C or 20 degrees C. When preincubation at 20 degrees C was followed by sperm exposure to 37 degrees C, capacitation-related events could be activated. In capacitated cells (16 hours at 37 degrees C), 2-hour incubation at 20 degrees C led to a significant decrease in acrosome reaction inducibility, suggesting sperm decapacitation. CONCLUSION(S): Human sperm incubation at room temperature does not allow capacitation, although it does not affect hFF-induced acrosome reaction in capacitated cells. The blocking effect is overcome when spermatozoa are exposed to 37 degrees C.

Acrosome Reaction↗