Search PubMed⌕ Search

Biomedical subjects

L J Zaneveld

Publications and source records attributed to L J Zaneveld.

At least 19 recordsLinked to original sources
PubMed1992

Effect of abstinence on sperm acrosin, hypoosmotic swelling, and other semen variables.

OBJECTIVE: To compare the variability of sperm acrosin and hypoosmotic swelling to the more standard semen variables in relationship to controlled periods of sexual abstinence using a defined group of men. DESIGN: Ten men abstained sequentially for 1, 2, 3, 4, 5, and 10 days and produced an ejaculate after each time period. The ejaculate variables measured at each time point were sperm acrosin, hypoosmotic swelling, volume, sperm number, sperm concentration, sperm motility, sperm morphology, pH, and white blood cells (WBCs). Comparisons were performed between the values obtained at each abstinence period. RESULTS: The percentage of hypoosmotically reactive spermatozoa did not vary significantly with the abstinence period. Sperm acrosin remained similar up to 5 days of abstinence but decreased almost twofold after 10 days of abstinence. The sperm volume and concentration increased gradually with the length of abstinence, being approximately twofold higher after 10 days of abstinence than after 1 day of abstinence. The total sperm number increased about fourfold from 1 day of abstinence to 10 days of abstinence. The percent normal sperm forms tended to increase until 5 days of abstinence but decreased after 10 days of abstinence. The WBC count showed only a small increase with longer abstinence periods. The pH remained essentially the same. CONCLUSIONS: The length of abstinence affects the various semen variables differently. An abstinence period of up to 10 days does not alter the hypoosmotic swelling test results. However, the sperm acrosin values decrease after prolonged abstinence so that the abstinence period needs to be taken into consideration when performing this assay.

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↗
PubMed1990

Proacrosin activation and acrosin release during the guinea pig acrosome reaction.

The kinetics of proacrosin activation and release from guinea pig spermatozoa during the nonsynchronous acrosome reaction were studied. Epididymal spermatozoa were incubated at 37 degrees C in a defined medium (pH 7.8) containing 1.7 mM Ca2+. After 195 min, 78% of the motile spermatozoa had undergone the acrosome reaction as determined by light microscopy. Acrosin and proacrosin levels in the spermatozoa and medium were measured at the beginning of the incubation period. Most of the total acrosin activity (78%) was associated with the spermatozoa, of which greater than 90% was in the form of proacrosin. Proacrosin represented a small, stable fraction (23%) of the total acrosin in the medium; it did not activate to acrosin while in the medium. After 195 min, a decrease in sperm-associated total acrosin (42%; p less than 0.05) was accompanied by an increase in the total acrosin level in the medium (115%; P less than 0.05). No change in the relative proacrosin content (percent of total acrosin) was evident in either medium or spermatozoa. Additional experiments quantified acrosin and proacrosin during the progression of the acrosome reaction. Both the loss of sperm-associated total acrosin and the increase in total acrosin levels in the medium were highly correlated with the fraction of acrosome-reacted spermatozoa (r = 0.954 and 0.922, respectively; P less than 0.001). However, the rate of acrosin appearance in the medium was only 60% (P less than 0.001) of the rate of acrosin loss from the spermatozoa. The fractional proacrosin content of spermatozoa (94%) and medium (31%) remained unchanged during the acrosome reaction (r = 0.15 and 0.30, respectively; P greater than 0.1).(ABSTRACT TRUNCATED AT 250 WORDS)

Acrosin↗
PubMed1990

Characterization and inhibitor sensitivity of human sperm phospholipase A2: evidence against pivotal involvement of phospholipase A2 in the acrosome reaction.

The kinetic properties and inhibitor sensitivity of human sperm phospholipase A2 (PLA2; EC 3.1.1.4) were studied. Phospholipase activity was isolated from human spermatozoa by acid extraction. Hydrolysis of dipalmitoyl phosphatidylcholine was specific to the sn-2 position. Activity was sensitive to product inhibition (60% inhibition by 0.1 mM lysophosphatidylcholine). The effects of Ca2+ and sodium deoxycholate on enzyme activity were biphasic; maximal activities were observed at 0.5 mM concentration of each agent. PLA2 was stimulated (135%) by 3% dimethylsulfoxide and was inhibited by elevated ionic strength (approximately 70% inhibition with either 0.2 M NaCl or 0.2 M KCl). Two molecular forms of PLA2 were kinetically distinguishable, one with an apparent Michaelis constant and maximal reaction velocity of 3.0 microM and 0.64 mlU/mg protein and the other with respective constants of 630 microM and 32.0 mlU/mg protein. Both forms of the enzyme were Ca2+ dependent and heat stable; however, the low-Km activity was less resistant to 60 degrees C preincubation at pH 7.5 (28% inactivation of low-Km activity after 45 min, as compared to no effect on high-Km activity). Quinacrine was a noncompetitive PLA2 inhibitor with Kis for low- and high-Km activities of 0.42 mM and 0.49 mM, respectively. Trifluoperazine (calmodulin antagonist) inhibited the high-Km activity noncompetitively (Ki = 87 microM) and the low-Km activity by a mechanism consistent with the removal of a nonessential activator. Dissociation and rate constants for inactivation of low- and high-Km activities by p-bromophenacyl bromide were 0.28 mM and 0.032 min-1, and 0.73 mM and 0.066 min-1, respectively. PLA2 was inhibited by p-nitrophenyl-p'-guanidinobenzoate, at higher concentrations (10(-4)-10(-3) M) than required to inhibit trypsinlike proteinases; p-aminobenzamidine, another potent trypsin/acrosin inhibitor, stimulated (approximately 40%) PLA2 at concentrations from 2-5 mM but inhibited PLA2 (40-50%) at a concentration of 10 mM. MnCl2 (5mM) inhibited low- and high-Km PLA2 activities by 77% and 76%, respectively. Quinacrine (0.4 mM), trifluoperazine (20 microM), p-bromophenacyl bromide (20 microM), and MnCl2 (5 mM) were tested as inhibitors of the ionophore A23187-induced human acrosome reaction. Inhibition was noted only with quinacrine (32%) and MnCl2 (93%). The effect of MnCl2 was restricted to an interaction with A23187, rather than with PLA2; p-Bromophenacyl bromide inhibited (P less than 0.05) PLA2 (29%) when added to intact spermatozoa but had no effect on the acrosome reaction. PLA2 inhibition was poorly correlated with the acrosome reaction.(ABSTRACT TRUNCATED AT 400 WORDS)

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1990

Comparative vaginal spermicidal studies in the stumptailed macaque with alkyloxynol-741, nonoxynol-9 and chlorhexidine.

Alkyloxynol-741 ("agent 741") is used in the People's Republic of China as a substitute for nonoxynol-9 in vaginal contraceptive formulations. However, no studies are available that compare the effectiveness of these agents as vaginal spermicides. For this reason, dissolvable polyvinylalcohol (PVA) films were prepared containing various concentrations of alkyloxynol-741 and nonoxynol-9. Films were also prepared containing chlorhexidine, a potentially new vaginal contraceptive agent. Postcoital vaginal spermicidal studies were performed with the films in the stumptailed macaque (Macaca arctoides). The order of spermicidal potency was: alkyloxynol-741 greater than nonoxynol-9 greater than chlorhexidine. These observations suggest that alkyloxynol-741 can be used instead of nonoxynol-9 in those countries where alkyloxynol-741 is more readily available and can be obtained at a lower cost.

Animals↗
PubMed1990

The effect of ketoconazole on fertility of male rats.

The effect of ketoconazole on the fertility of male rats was evaluated. Three days of oral dosing with ketoconazole at 200 mg/kg reduced fertility compared to controls. A complete loss of fertility was observed after doses of 400 mg/kg. There was no change in the testicular weight, epididymal sperm concentration or epididymal weight between the control and treatment groups. Motility was reduced in the high-dose group and forward progression was reduced in both dosing groups compared to control. These data support previous observations in the dog and primate that orally administered ketoconazole alters sperm viability. Although ketoconazole is too toxic for contraceptive application, its derivatives may be useful for this purpose.

Administration, Oral↗
PubMed1990

The lack of mutagenicity of aryl 4-guanidinobenzoates in the transplacental micronucleus assay in mice.

Two acrosin inhibitors, 4'-methylumbelliferyl 4-guanidinobenzoate and 2'-carbomethoxyphenyl 4-guanidinobenzoate, were tested for mutagenicity in the transplacental micronucleus assay and the mouse bone marrow micronucleus assay. The compounds were administered intraperitoneally at doses of 125 mg/kg and 250 mg/kg to pregnant mice. Fetal peripheral blood and maternal bone marrow cells were examined at 36 h for the frequency of micronucleated polychromatic erythrocytes. Neither compound induced micronuclei in maternal or fetal tissues. The ratio of polychromatic erythrocytes to normochromatic erythrocytes was not affected by the drug treatments indicating that the compounds had no effect on the cell cycle or mitosis in these tissues and that they were not cytotoxic. Both compounds, which show promise as vaginal contraceptives, were not mutagenic in this study.

Animals↗
PubMed1990

Hypo-osmotic swelling test: analysis of prevasectomy ejaculates.

The hypo-osmotic swelling (HOS) test was applied to 1,890 ejaculates obtained from previously fertile men who subsequently underwent a vasectomy. Less than 3% of the ejaculates produced an abnormal HOS test (less than 50% swelling), and more than 95% were normal (greater than or equal to 60% swelling). The sperm concentration and motility data were similar to those obtained by other investigators with prevasectomy ejaculates. Statistically significant but low correlation coefficients were present between the HOS test and these other sperm variables. On the assumption that the large majority of these men were fertile when the ejaculates were produced, the results support the contention that fertility is usually associated with normal or, occasionally, equivocal values in the HOS test.

Adult↗
PubMed1990

Inhibition of the human sperm acrosome reaction by a high molecular weight factor from human seminal plasma.

Human seminal plasma possesses a factor (acrosome reaction-inhibitory factor) that is precipitated by high speed centrifugation and that inhibits the ionophore- and dbc AMP-induced acrosome reaction of capacitated human spermatozoa but only if it is added toward the end of the capacitation period. Acrosome reaction-inhibitory factor can be partially purified by cation exchange chromatography and appears to differ from another factor that can be obtained by ultracentrifugation of human seminal plasma and that prevents the fertilization of mouse gametes.

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↗
PubMed1989

Testosterone production by the prepubertal mouse testis is not depressed by ethanol.

The purpose of the present study was to evaluate the sensitivity of testicular steroidogenesis during pubertal development to inhibition by ethanol. In vivo and in vitro human chorionic gonadotropin (hCG)-stimulated steroidogenesis were examined in CFW mice as a function of age. Plasma androstenedione, testosterone, and dihydrotestosterone (DHT) increased from ages 23 to 60 days in control mice. Acute ethanol treatment (3 g/kg) yielded static levels of androstenedione (0.45 +/- 0.03 ng/mL), testosterone (6.4 +/- 0.56 ng/mL), and DHT (2.3 +/- 0.18 ng/mL) from ages 23 to 60 days, 30 to 60 days, and 35 to 60 days, respectively, resulting in reduction of plasma androstenedione, testosterone, and DHT (P less than 0.05) relative to control values, but not until ages 35, 50, and 45 days, respectively. A similar insensitivity of the prepubertal testis to ethanol was seen in vitro. Inhibition of in vitro androstenedione and testosterone accumulation was seen only after ages 26 and 45 days, respectively. The data indicate that testosterone production by the pubertal testis is relatively insensitive to direct inhibition by ethanol. Previous studies have shown that chronic ethanol treatment of adolescent mice delays testicular maturation. The present study suggests that if chronic ethanol-induced delayed testicular development were due to impaired steroidogenesis, such impairment would be secondary to reduced gonadotropin stimulation and/or due to a chronic, rather than an acute, effect of ethanol.

Aging↗
PubMed1989

Ethanol-induced delayed male puberty in mice is not due to impaired Leydig cell function.

The present study was performed to evaluate the involvement of reduced testosterone in ethanol-induced impairment of male reproductive tract development. In vivo and in vitro gonadotropin (hCG)-stimulated steroidogenesis were examined in CFW mice as a function of chronic ethanol treatment during pubertal development. Chronic ethanol treatment from ages 20 to 49 days impaired testicular growth from ages 35 days (29 +/- 2 mg vs 37 +/- 2 mg for pair-fed controls) to 50 days (42 +/- 2 mg vs 63 +/- 2 mg for pair-fed controls). Consistent with a reduction in testicular weight, testicular content of androstenedione, testosterone, and dihydrotestosterone (DHT) was depressed in ethanol-treated mice. At age 50 days, the content (expressed as pg/testis) of androstenedione, testosterone, and DHT was reduced in ethanol-treated animals by 49%, 31%, and 38%, respectively, as compared to that of their respective controls. However, no difference in plasma (ng/mL) or testicular (pg/mg protein) concentrations of steroids was observed. Except for the DHT response at ages 35 to 40 days, neither in vivo nor in vitro steroidogenesis was impaired by chronic ethanol treatment at ages 26 to 50 days; similarly, the acute ethanol effect on steroidogenesis was unaffected. However, an adaptive increase (54%-173%) in the in vivo testosterone response to hCG was seen at ages 26 to 40 days. The data indicate that 1) chronic ethanol treatment does not impair gonadotropin-stimulated steroidogenesis or result in tolerance to acute ethanol effects on steroidogenesis in older animals; and 2) ethanol-induced reduction in testosterone is not a likely mechanism for delayed sexual maturation.

Aging↗
PubMed1979

Development of a reversible vas deferens occlusive device. VI. Long-term evaluation of flexible prosthetic devices.

Fifty-three dogs received implants of several types of flexible devices containing valving mechanisms. These devices were constructed entirely of silicone rubber with the exception of the valve stem, which was made of stainless steel. Generally, the devices were (1) implanted in the open mode and left this way for 27 to 44 months, (2) implanted in the closed mode and kept this way for 11 to 12 months before the valves were reopened, (3) implanted in either the closed or open mode and cycled to the opposite mode every 3 months (four or five cycles), or (4) implanted in either the closed or open mode and cycled to the opposite mode every 6 months (two or three cycles). Different implant methods were also evaluated. Semen analyses were regularly performed on all of the dogs, and a number of the animals were bred during the experiments. It can be concluded that (1) the devices can be opened and closed successfully over long periods, respectively allowing and preventing sperm transport; (2) the breeding ability of the animals is not impaired while the devices are in the open mode, independent of the type of device; (3) the devices do not result in an enhanced incidence of congenital abnormalities in the offspring; and (4) the success rate of device performance does not depend on the method of implanatation used. Thus, the results clearly indicate that the basic mechanism of a soft, reversible valve is a feasible approach to conception control.

Animals↗
PubMed1979

The role of acrosin in sperm penetration through human cervical mucus.

Enzymes have been implicated in facilitating cervical mucus penetration by spermatozoa. One of these enzymes in the neutral proteinase acrosin, which is associated with the sperm acrosome. To determine the validity of this hypothesis, human spermatozoa were incubated with the following acrosin inhibitors: p-aminobenzamidine (AB), N-alpha-p-tosyl-L-lysine chloromethyl ketone (TLCK), and p-nitropheyl-p'-guanidino benzoate (NPGB). An in vitro slide test system was developed which allowed inhibitor-treated and control spermatozoa to be evaluated against the same human cervical mucus sample. At inhibitor concentrations far exceeding those necessary for the inhibition of human acrosin, there was no effect on spermatozoal penetration into or through the mucus. These findings indicate that, in man, acrosin activity is neither necessary nor facilitory to sperm penetration of cervical mucus. Evidence is also presented that demonstrates the superiority of the newly developed double-interface slide test, especially for comparative purposes, over the tests currently in use.

Acrosin↗
PubMed1979

Acrosin of mouse spermatozoa.

Mouse spermatozoa possess a neutral proteinase, acrosin, that is to a large extent (70-80%) present in the zymogen (proacrosin) form. Acid extraction yields higher amounts of acrosin than detergent extraction. Synthetic inhibitor studies indicate that mouse acrosin has a serine and histidine at its active site and hydrolyzes the peptide bonds of lysine and arginine but of not phenylalanine. An inhibitor of acrosin is associated with mouse spermatozoa, capable of preventing the activity of at least 60% of all available acrosin. Acrosin activity is essential for fertilization because natural and synthetic inhibitors of mouse acrosin prevent the union of the gametes. Also, the relative inhibitory activity of synthetic agents toward acrosin runs approximately parallel to their antifertility activity. The percent of acrosin in the proacrosin form does not change after capacitating mouse spermatozoa in vitro.

Acrosin↗