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C J De Jonge

Publications and source records attributed to C J De Jonge.

At least 19 recordsLinked to original sources
PubMed1998

An update on human fertilization.

The process of fertilization and the role that each gamete plays in that process have been the subject of investigation in a large number of species and for many years. However, while much is now known for some species relatively little is known for others. Indeed, the specific events that are required to occur in the human male and female gametes and that facilitate fertilization are still somewhat ill-defined. For example, as of today, there have been numerous biomolecular processes that have been put forth as playing an important role in the sequence of events during which sperm acquire fertilizing ability, yet the actual significance of many of these remains suspect. This article will summarize what is presently best known about prefertilization processes occurring in human spermatozoa. For those interested in nonhuman mammalian and nonmammalian species, articles addressing this and other topics can be found in the many review articles cited herein.

Acrosome Reaction↗
PubMed1997

Failure of multitube sperm swim-up for sex preselection.

OBJECTIVE: To use double-label fluorescence in situ hybridization to evaluate a modified swim-up procedure that is purported to be effective for preconceptual sex selection. DESIGN: Controlled, blinded study. SETTING: University hospital laboratories. PATIENT(S): Donor males reporting for routine semen analysis. MAIN OUTCOME MEASURE(S): Percentages of X- and Y-bearing spermatozoa in neat semen and in two swim-up fractions, determined using double-label fluorescence in situ hybridization. RESULT(S): No clinically significant change from a 1:1 ratio was found in the distribution of X- or Y-bearing spermatozoa after double-label fluorescence in situ hybridization following a modified swim-up procedure and irrespective of the time (15, 30, 45, and 60 minutes) allowed for swim-up. CONCLUSION(S): Using fluorescence in situ hybridization, a modified swim-up procedure was evaluated for its purported ability to skew the relative percentages of X- and Y-bearing spermatozoa. No clinically significant change in the ratio of X- to Y-bearing spermatozoa was detected independent of time. Therefore, clinical application of this procedure should be strongly discouraged.

Bias↗
PubMed1994

Are capacitation or calcium ion influx required for the human sperm acrosome reaction?

OBJECTIVE: To determine if the acrosome reaction of human spermatozoa can occur without prior incubation to induce capacitation or in calcium-free medium. DESIGN: Noncapacitated (washed ejaculated) or capacitated (incubated for 3 hours in the presence of albumin) human spermatozoa were treated with either solubilized zonae pellucidae (ZP); a calcium ionophore (A23187); or activators of protein kinases A, G, and C, and the acrosomal status was monitored by the double stain technique. During agonist treatment, the capacitated spermatozoa were in medium either with or without calcium ions (Ca2+). The noncapacitated spermatozoa were always in Ca(2+)-containing medium. Sperm motility was monitored throughout the experiments. RESULTS: Solubilized ZP and kinase activators induced acrosomal exocytosis of capacitated spermatozoa (both in Ca(2+)-containing and Ca(2+)-free medium) and of noncapacitated spermatozoa. The lack of added Ca2+ or capacitation reduced the percentage of spermatozoa that reacted in response to solubilized ZP but not to the kinase activators. Ionophore A23187 stimulated acrosomal loss from noncapacitated spermatozoa to the same extent as capacitated spermatozoa in Ca(2+)-containing medium but had no effect on capacitated spermatozoa in Ca(2+)-free medium. CONCLUSIONS: Human spermatozoa do not require incubation under capacitating conditions or the presence of extracellular Ca2+ before they can undergo the acrosome reaction in response to certain agonists. Therefore, Ca2+ influx and/or preincubation to induce capacitation are not absolute requirements for the in vitro agonist-induced acrosome reaction. However, these conditions can optimize the acrosome reaction response to zona proteins. The intracellular mechanisms leading to the acrosome reaction appear to be functional in noncapacitated spermatozoa but membrane changes probably are required before certain extracellular ligands such as zona proteins can exert their maximal effect.

Acrosome↗
PubMed1994

The zona pellucida-induced acrosome reaction of human spermatozoa is mediated by protein kinases.

OBJECTIVE: To determine if the solubilized human zona pellucida (ZP)-induced acrosome reaction is mediated by protein kinases. DESIGN: Capacitated spermatozoa were incubated with inhibitors of cyclic adenosine 3':5'-monophosphate (cAMP)-dependent kinase (KT5720), Ca(2+)- and phospholipid-dependent kinase (Calphostin C), and cyclic guanosine 3':5'-monophosphate (cGMP)-dependent kinase (KT5823) and then treated with a corresponding kinase stimulator (dibutyryl cAMP, phorbol 12-myristate 13-acetate and dibutyryl cGMP, respectively) to determine the effect on the acrosome reaction. Appropriate controls were performed. Zonae obtained from the unfertilized oocytes of women attending an IVF program were solubilized using acidic NaH2PO4, and the effect of solubilized ZP on the acrosome reaction was tested in dose-response fashion. Comparative studies with solubilized, zona-free oocyte-treated spermatozoa were performed. The effect of the kinase inhibitors on the solubilized ZP-induced acrosome reaction was then determined. RESULTS: No significant stimulation of the acrosome reaction by kinase stimulators occurred when spermatozoa were pretreated with inhibitors of the kinases, in contrast to the controls. Capacitated spermatozoa incubated with 2, 4, and 6 solubilized ZP showed a dose-dependent increase in the acrosome reaction. Solubilized oocytes had no effect on the acrosome reaction. Pretreatment of spermatozoa with kinase inhibitors significantly lowered the acrosome reaction induced by solubilized ZP but not completely. When a "cocktail" of the three inhibitors was used, a significant reduction in the acrosome reaction occurred in comparison with single inhibitor treatment. CONCLUSION: The present data indicate a role for human ZP-induced activation of multiple second messenger pathways, involving kinases A, C, and G in the human sperm acrosome reaction.

Acrosome↗
PubMed1993

Acrosin activity in human spermatozoa in relation to semen quality and in-vitro fertilization.

Acrosin, a sperm proteinase released during acrosomal exocytosis, facilitates penetration through the oocyte vestments. The purpose of this investigation was to determine if a correlation exists between the acrosin activity of ejaculated human spermatozoa, before motility enrichment techniques, and in-vitro fertilization (IVF) success using selected (glass wool or swim-up) spermatozoa. Since all the oocytes were retrieved from women receiving exogenous hormonal stimulation and a mixed population of mature and immature oocytes were encountered, only cases with > or = 50% mature oocytes were analysed. Under these conditions, the acrosin activity was significantly greater (P < 0.01) in the ejaculates in which spermatozoa ultimately fertilized > or = 70% of the mature oocytes, than in the ejaculates in which spermatozoa ultimately fertilized < 70% of the mature oocytes. Furthermore, a strong correlation (r = 0.962, P = 0.0001) was detected between pre-IVF acrosin activity and subsequent high (> or = 70%) IVF success. Acrosin activity from normozoospermic and oligo-asthenozoospermic men was also compared and was significantly (P < 0.01) higher for the normozoospermic group. These data suggest that measurement of acrosin activity may be a valuable clinical laboratory assay for assessing the sperm fertilizing potential and that low acrosin activity is associated with abnormal semen characteristics.

Acrosin↗
PubMed1991

Modulation of the human sperm acrosome reaction by effectors of the adenylate cyclase/cyclic AMP second-messenger pathway.

The acrosome reaction of spermatozoa appears to be analogous to various somatic cell exocytotic events which involve cascade reactions, i.e., transmission of an external signal across the cell membrane resulting in activation of an "amplifier" enzyme and the generation of a second messenger. Using a synchronous acrosome reaction system (De Jonge et al., J. Androl., 10:232-239, '89a), it was found that analogues of the second-messenger cAMP, dibutyryl cAMP (dbcAMP) and 8-bromo cAMP, stimulated the acrosome reaction of capacitated spermatozoa. Additionally, treatment of spermatozoa with either xanthine or non-xanthine phosphodiesterase inhibitors induced a significant (P less than 0.05) increase in the percent acrosome reaction after a period of capacitation in comparison to untreated controls. These results indicate that analogues of cAMP or inhibitors which prevent cAMP hydrolysis can induce the human sperm acrosome reaction. Subsequent experiments were conducted to test whether the amplifier enzyme in the cascade reaction, adenylate cyclase, has a role in the acrosome reaction. Forskolin, an adenylate cyclase stimulator, caused a significant (P less than 0.01) increase in the percent acrosome reaction in comparison to controls. Modulators of adenylate cyclase--adenosine, 2'-0-methyladenosine, and 2',3'-dideoxyadenosine--significantly (P less than 0.01) inhibited the forskolin-induced acrosome reaction. dbcAMP was able to overcome the inhibition by adenosine. Two inhibitors of protein kinase A, the Walsh inhibitor and H-8, caused a significant (P less than 0.01) inhibition of the dbcAMP-induced acrosome reaction. Finally, in the absence of extracellular calcium, dbcAMP induced a significant (P less than 0.01) increase in the acrosome reaction in contrast to A23187. These results suggest that: 1) a molecular mechanism for the human sperm acrosome reaction involves the cAMP second-messenger system; i.e., activation of adenylate cyclase, the amplifier enzyme that produces cAMP, production of cAMP as a second messenger, and activation of cAMP-dependent kinase A; and that 2) activation of adenylate cyclase occurs after calcium influx.

Acrosome↗
PubMed1991

Human sperm capacitation and the acrosome reaction.

A model is presented that describes the mechanism of human sperm capacitation and the acrosome reaction. The processes of capacitation and the acrosome reaction are proposed to function in control of the activation/release of acrosomal enzyme(s) involved in sperm penetration through the zona pellucida. During capacitation, the sperm head membranes are biochemically modified, allowing the acrosome reaction to take place when the spermatozoon approaches or reaches the zona pellucida, resulting in the localized activation and release of the appropriate enzyme(s). Further, capacitation is presented as a continuing process that occurs during sperm transport through the female genital tract and is physiologically not completed until the spermatozoon reaches the oocyte (unless the spermatozoa are kept at a particular genital tract site for prolonged periods). The biochemical alterations that occur during capacitation are discussed. It is suggested that extensive modifications in the lipid bilayer structure, e.g. in the cholesterol or phospholipid content, are not part of capacitation because such changes would prematurely destabilize the membranes. Rather, such changes occur during the acrosome reaction. It is also proposed that the human sperm acrosome reaction has many similarities to the somatic cell exocytotic events which occur during the regulated pathway of secretion. One or more oocyte stimuli result in the activation of protein kinases, likely (but not necessarily) via activation of G-protein coupled receptors on the sperm plasma membrane and the formation of second messengers. The kinases phosphorylate and activate proteins, continuing the biochemical cascade that ultimately results in the acrosome reaction. The role of other enzyme systems such as those involved in ion transport, proteolysis, phospholipid metabolism (including that of arachidonic acid) and other metabolic events, is discussed. Calcium ion influx as initiator of the acrosome reaction is reconsidered. The proposed model also takes into consideration the structural events of membrane fusion.

Acrosome↗
PubMed1989

Inhibition of the human sperm acrosome reaction by proteinase inhibitors.

The analogue of the second messenger cAMP, dibutyryl cAMP (dbcAMP), was shown to induce the human sperm acrosome reaction to the same extent as calcium ionophore A23187, providing preliminary evidence for the involvement of the adenylate cyclase system in the acrosome reaction (AR) of human spermatozoa. Using the human synchronous acrosome reaction system, proteinase inhibitors were tested for their effect on the dbcAMP-induced human sperm acrosome reaction. The proteinase inhibitor 4'-acetamidophenyl 4-guanidinobenzoate (AGB), an inhibitor of proacrosin activation and of acrosin, when added at either the onset of incubation or to capacitated spermatozoa, 5 min prior to stimulation by dbcAMP, significantly (P less than 0.01) inhibited the acrosome reaction at final concentrations of 1 x 10(-4) M to 1 x 10(-6) M in comparison to dbcAMP treatment alone. At concentrations less than 1 x 10(-6) M, no significant inhibitory effect was seen. Similarly, para-aminobenzamidine (pAB), also an inhibitor of proacrosin activation and of acrosin, significantly (P less than 0.01) inhibited the dbcAMP-induced acrosome reaction at final concentrations of 1 x 10(-4) M to 1 x 10(-6) M when added at either the onset of incubation or to capacitated spermatozoa, 5 min prior to stimulation by dbcAMP, in comparison to stimulation by dbcAMP alone. However, at concentrations less than 1 x 10(-6) M, no significant (P greater than 0.05) inhibitory effect was seen. These results indicate that a serine proteinase, most likely acrosin, has a role in the human sperm acrosome reaction and suggest that the enzyme functions after the involvement of the adenylate cyclase system.

Acrosin↗
PubMed1988

Induction of the human sperm acrosome reaction by human oocytes.

The acrosome reaction of human spermatozoa incubated in the presence or absence of vested human oocytes was investigated. All gametes were obtained from human in vitro fertilization (IVF) cases. Spermatozoa were collected after incubation in insemination medium only and following removal of the oocytes from insemination medium during the IVF procedure. After 16 hours of incubation 18.5% of the spermatozoa in insemination medium alone were acrosome-reacted compared to 31.5% for spermatozoa incubated in medium containing oocytes. The acrosome reaction of spermatozoa incubated with fertilized or unfertilized oocytes was also investigated. The percentage of acrosome reaction did not differ (P greater than 0.05) between the two groups (29.7% in the fertilized cases versus 30.7% in the unfertilized cases). Completion of oocyte nuclear maturation did not affect the proportion of acrosome-reacted spermatozoa observed with unfertilized eggs. A similar (P greater than 0.05) percentage of acrosome reacted spermatozoa were observed regardless of whether the unfertilized oocytes had (29%) or had not (35%) reached metaphase II. These findings indicate the acrosome reaction of human spermatozoa is enhanced in the presence of vested human oocytes. Furthermore, there is no apparent correlation between the percentage of the population of spermatozoa that acrosome react in the medium and the potential of an oocyte for fertilization.

Acrosome↗
PubMedDate not supplied

Synchronous assay for human sperm capacitation and the acrosome reaction.

A synchronous acrosome reaction system was established for human spermatozoa. Seminal plasma is removed from the spermatozoa by centrifugation and the washed spermatozoa are capacitated in a modified BWW medium (without exogenous substrates) containing 35 mg/ml human serum albumin for 3 h at 37 C. Subsequently, 10 microM ionophore A23187 (final concentration) is added, the mixture incubated for 15 min at 37 C and the percent acrosome reaction determined by a modified triple stain technique (trypan blue stain omitted). Since no significant decrease in sperm motility occurs during incubation or after ionophore treatment, a vital stain does not need to be employed, allowing the use of any acrosome detection technique. The average percentage of acrosome-rejected spermatozoa after ionophore treatment (40 +/- 10%) was about 2- to 3-fold higher than that seen without ionophore treatment. Ionophore treatment for 15 min failed to stimulate the acrosome reaction in spermatozoa incubated for less than 3 h. Additionally, the presence of substrates in the BWW medium, higher sperm numbers, increased ionophore concentrations or longer incubation periods did not enhance the induction of the acrosome reaction. Ionomycin, a more specific calcium ionophore than A23187, produced essentially the same results as A23187 but tended to decrease sperm motility. This synchronous acrosome reaction system for human spermatozoa is relatively simple and can be used to study the effect of modulators on capacitation and/or the acrosome reaction.

Acrosome↗
PubMedDate not supplied

Effect of phorbol diesters, synthetic diacylglycerols, and a protein kinase C inhibitor on the human sperm acrosome reaction.

The acrosome reaction of spermatozoa may be analogous to various somatic cell exocytotic events that incorporate cascade reactions. One such cascade system involves the hydrolysis of a membrane-bound phospholipid; generation of the intracellular second messenger, diacylglycerol; and activation of protein kinase C, followed by the phosphorylation of a number of intracellular proteins. Stimulators of protein kinase C, phorbol diesters and synthetic diacylglycerols, were evaluated to determine if this system functions in the human sperm acrosome reaction. Phorbol 12-myristate 13-acetate and 4 beta-phorbol 12,13-didecanoate caused a significant (P less than 0.01) increase in the acrosome reaction of capacitated spermatozoa. Conversely, an inactive phorbol diester had no significant (P greater than 0.05) stimulatory effect on the acrosome reaction. The synthetic diacylglycerols, 1-oleoyl-2-acetyl-sn-glycerol, 1,2-dioctanoyl-sn-glycerol, and 1,2-dioleoyl-sn-glycerol caused a significant (P less than 0.01) increase in the acrosome reaction of capacitated spermatozoa, and to a similar extent as the phorbol diesters. A nonactivating isomer of 1,2-dioleoyl-sn-glycerol, 1,3-diolein, had no significant (P greater than 0.05) stimulatory effect on the acrosome reaction. Protein kinase C activation is a diacylglycerol-dependent and Ca2(+)-dependent process, and stimulation of the acrosome reaction by 1,2-dioctanoyl-sn-glycerol required the presence of calcium ions in the capacitation medium. An inhibitor of protein kinase C, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine (H-7), prevented the diacylglycerol-induced acrosome reaction (P less than 0.01). These results support the hypothesis that protein kinase C, via activation by the intracellular second messenger diacylglycerol, has a role in the human sperm acrosome reaction.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMedDate not supplied

The acrosome reaction-inducing effect of human follicular and oviductal fluid.

The human sperm acrosome reaction (AR) can be induced in vitro by a variety of naturally occurring and synthetic compounds. The present investigation determined the effect of human natural cycle periovulatory follicular (hFF) and oviductal fluids (hOF) on the human sperm AR in dose-response fashion using the synchronous AR assay. When hFF (30% v/v) or hOF (40% v/v) was added to non-capacitated spermatozoa, no significant (P > 0.05) increase in the % AR was detected in comparison to the non-treatment control. When either of these compounds was added (10%, 20%, and 30% v/v hFF; 20%, 30%, and 40% v/v hOF) to capacitated spermatozoa (3 hour incubation), a significant (P < 0.05) stimulation of the AR was detected. Bovine oviductal fluid (bOF) was tested (20%, 30%, and 40% v/v) to determine if it might have an effect similar to hOF. In contrast to hOF, the highest concentration of bOF (40% v/v) tested failed to stimulate a significant (P > 0.05) increase in the % AR of capacitated spermatozoa in comparison to control. Inhibitors of protein kinases A (KT5720) and C (calphostin C) were tested to determine their effects on the hFF-induced AR. In comparison to hFF treatment alone, the kinase A inhibitor KT5720 (50 nM, 100 nM) prevented hFF (20%) stimulation of the AR when added at the end of the capacitation period and 5 minutes prior to the addition of inducer. Similarly, the kinase C inhibitor calphostin C (50 nM, 100 nM) prevented hFF (20%) stimulation of the AR. The present data demonstrate that periovulatory hFF and hOF stimulate the human sperm AR.(ABSTRACT TRUNCATED AT 250 WORDS)

Acrosome↗