Energy conversion in bull sperm flagella

Assessment of ram sperm mitochondrial function by quantitative determination of sperm rhodamine 123 accumulation

A simple procedure is described for determining the functional state of ram sperm mitochondria by quantitative measurement of sperm rhodamine 123 (R 123) accumulation. Sperm were incubated with 1 microgram/ml R 123, and the accumulated R 123 was measured fluorimetrically after release from washed sperm by detergent lysis. Ram sperm R 123 uptake was maximal after 30 min of incubation and responded to changes in both sperm (P < 0.01) and R 123 (P < 0.01) concentration. There was a linear relationship (r = 0.98) between R 123 uptake and the proportion of cold-shocked sperm present in a sperm sample. R 123 uptake was unaffected by 20 mM 2-deoxyglucose or by 10 mM malonate (the latter being sufficient to reduce O2 uptake; P < 0.01). R 123 accumulation in ram sperm was reduced by 6 mg/ml sodium pentobarbitone (P < 0.05), by 1 microM 2,4-dinitrophenol (P < 0.01), and by 0.05% Triton X-100 (P < 0.01). It is concluded that quantitative estimation of R 123 uptake complements oxygen uptake in detecting mitochondrial dysfunction in ram sperm. While it is largely unaffected by inhibition of glycolysis, and is less sensitive than oxygen uptake to trichloroacetic acid cycle inhibition, R 123 uptake is sensitive to factors directly reducing the mitochondrial membrane potential of ram sperm. It may therefore by useful in the evaluation of the effects of such membrane-mediated injuries as cold shock and freezing damage on ram sperm mitochondria.

Motility, heat, and lactate production in ejaculated bovine sperm

Effects of various inhibitors on motility, heat, and lactate production of ejaculated bovine sperm were determined in the presence of antimycin A and rotenone. erythro-9-[3-(2-Hydroxynonyl)]adenine (EHNA) and polyvinylpyrrolidone (PVP-360) stopped motility and reduced heat or lactate production by 30-50%. Carbodiimides resulted in loss of motility and a reduction of metabolism by 60-75%. Quercetin treatment, which enhanced rather than inhibited motility, depressed heat and lactate production by 50-60%. Since mechanical immobilization reduced heat production by only 30%, the question arises as to what other cellular processes are major contributors to the energy budget. Inhibitors of ion flux had little-to-no effect on heat or lactate production, suggesting that neither mitochondrial nor Na+/K+ ATPases were major ATP-requiring processes. Calcium flux at the plasma membrane also was minimal and previous reports eliminated glycolytic substrate cycling as major consuming processes for ATP. Although quercetin inhibited lactate production in intact cells, no effect of quercetin on cell-free glycolysis and the ATPase activities of isolated dynein was detected. Quercetin did, however, inhibit ATPase activity of plasma membrane, suggesting that this unidentified ATPase may contribute to the formation of ADP and Pi required for lactate production by the intact cell. We propose (a) that the bioenergetic costs of motility are divided between regulatory events and dynein-microtubule interaction (dynein ATPase), (b) that some of the membrane-related processes may be "inefficient," and (c) that quercetin may render these steps more "efficient," in a manner analogous to its action on the Na+/K+ pump of Ehrlich ascites tumor cells.

Calcium regulation of flagellar curvature and swimming pattern in triton X-100--extracted rat sperm

Free Ca2+ changes the curvature of epididymal rat sperm flagella in demembranated sperm models. The radius of curvature of the flagellar midpiece region was measured and found to be a continuous function of the free Ca2+ concentration. Below 10(-7) M free Ca2+, the sperm flagella assumed a pronounced curvature in the same direction as the sperm head. The curvature reversed direction at 2.5 x 10(-6) M Ca2+ to assume a tight, hook-like bend at concentrations of 10(-5) to 10(-4) M free Ca2+. Sodium vanadate at 2 x 10(-6) M blocked flagellar motility, but did not inhibit the Ca2+-mediated change in curvature. Nickel ion at 0.2 mM and cadmium ion at 1 microM interfered with the transition and induced the low Ca2+ configuration of the flagellum. The forces that maintain the Ca2+-dependent curvature are locally produced, as dissection of the flagella into segments did not significantly alter the curvature of the excised portions. Irrespective of the induced pattern of curvature, the sperm exhibited coordinated, repetitive flagellar beating in the presence of ATP and cAMP. At 0.3 mM ATP the flagellar waves propagated along the principal piece while the level of free Ca2+ controlled the overall curvature. When Ca2+-treated sperm models with hooked midpieces were subjected to higher concentrations of ATP (1-5 mM), some cells exhibited a pattern of movement similar to hyperactivated motility in capacitated live sperm. This type of motility involved repetitive reversals of the Ca2+-induced bend in the midpiece, as well as waves propagated along the principal piece. The free Ca2+ available to the flagellum therefore appeared to modify both the pattern of motility and the flagellar curvature.

Effects of dibromochloropropane and ethylene dibromide on biochemical events and ultramorphology of ejaculated ram spermatozoa in vitro

The effects of dibromochloropropane (DBCP) and ethylene dibromide (EDB) on the function and ultrastructure of freshly ejaculated washed ram spermatozoa were assessed. These two compounds inhibited the collective motility of the sperm in a dose-dependent fashion when the sperm cells generated their energy either by mitochondrial respiration (2-deoxyglucose-treated sperm cells) or by the intact energy production system. DBCP and EDB inhibited the oxygen uptake by the sperm in a dose-dependent manner. No change in lactic acid accumulation and glucose utilization by the sperm cells was noted following DBCP and EDB addition. No change in the collective motility of the sperm was noted when DBCP or EDB were added to spermatozoa treated with the electron transfer inhibitor, antimycin A. Electron microscopy studies of sperm cells treated with DBCP revealed lesions in the plasma membrane adjacent to the acrosome and in the acrosomal membrane forming vesiculations. The inner membrane and the matrix space of the mitochondria were condensed following DBCP treatment, leaving a large mitochondrial peripheral space, compared with the control. EDB, at the concentration studied, caused no change in the ultramorphological structure of the sperm. DBCP was more potent, at least 4-fold, compared with EDB. An in vitro direct effect of DBCP and EDB on ram spermatozoa was established. It is suggested that quantitative measurements of sperm collective motility derived by different metabolic pathways can be used as an in vitro toxicological model for evaluation of toxicological and environmental factors affecting biological systems.

The relationship between glycolysis, mitochondrial respiration, protein-carboxyl methylation and motility in hamster epididymal spermatozoa

Endogenous protein-carboxyl methylase activity can be measured in intact motile spermatozoa by using [3H]methionine as a precursor of the methyl donor, S-adenosylmethionine (SAM). Since the conversion of methionine to SAM requires ATP, the relationship between the energy metabolism of spermatozoa and methylation was investigated using inhibitors of glycolysis and mitochondrial respiration. When hamster spermatozoa from cauda epididymides were incubated in 12.2 mM glucose, glycolysis was progressively inhibited as concentrations of 2-deoxyglucose (2-DOG) increased. On the other hand, endogenous protein-carboxyl methylation showed a biphasic response being stimulated at low concentrations of 2-DOG and inhibited at higher concentrations. Sperm movement was also altered by 2-Dog. Increasing concentrations of 2-DOG in the incubation medium resulted in an increase in beat amplitude and a corresponding decrease in beat frequency. When the glucose concentration of the medium was reduced to 5 mM, protein methylation was inhibited at all concentrations of 2-DOG. The biphasic effect of 2-DOG on methylation at 12.2 mM and its monophasic effect at 5 mM suggested that this reaction was related to the effective glucose concentration. To investigate this possibility, endogenous protein-carboxyl methylation was measured after incubation of sperm in glucose concentrations ranging from 0-48.8 mM. Low glucose concentrations stimulated protein methylation (up to 6.1 mM for maximal effect), but further increases in the glucose concentration (10-48.8 mM) suppressed the rate of protein methylation to that observed in the absence of glucose. 2-Deoxyglucose decreased conversion of pyruvate to CO2 consistent with diminished mitochondrial respiration. The inhibition of mitochondrial respiration by antimycin A also inhibited endogenous methylation and motility. The results of these studies suggest that maximal endogenous protein-carboxyl methylation in intact spermatozoa from hamster epididymides depends upon active glycolysis as well as mitochondrial respiration.

Alterations in motility and metabolism associated with sperm interaction with accessory sex gland fluids

Sperm passing through the male tract interact with accessory sex gland fluids during ejaculation. Cellular metabolism is stimulated by this interaction for unknown reasons. These experiments involved calorimetric measurements [P.B. Inskeep and R.H. Hammerstedt (1983) J. Biochem. Biophys. Methods 7, 199-210] on ejaculated sperm (EJS) and cauda epididymal sperm (CES) from bulls to establish the contribution of individual pathways to total cellular ATP synthesis. Parallel incubations outside the calorimeter yielded samples for oxygen consumption measurements and for motility analysis, the major ATP-consuming reaction of sperm. Energy charge values were identical for incubations of EJS and CES with glucose, thereby establishing that the ratios of rates of ATP synthesis and degradation were equivalent for these cells under this incubation condition. The total rate of ATP synthesis was greater for EJS than for CES (5 vs 13 mumol ATP h-1/10(8) cells) with less than 2 mumol ATP h-1 for each cell type coming from degradation of endogenous reserves. Thus, ejaculation is associated with a large increase in catabolic rate that is satisfied by degradation of extracellular glucose. No difference in percentage of motile sperm was noted, but mean velocity was lower for CES (58 micron s-1) than for EJS (85 micron s-1). A difference in forward motility pattern was observed (wig-wag to flipping). We conclude from these data that interaction with accessory sex gland fluids alters ATP requiring activities of sperm, with one obvious alteration being their motility pattern. The increase in ATP requirement is satisfied by increased degradation of extracellular substrates, but not intracellular reserves, to provide sufficient ATP to satisfy cellular needs.

Interdependence of mitochondrial ATP production and extramitochondrial ATP utilization in intact spermatozoa

The dependence of both respiration and total activity of ATP-consuming reactions on the cellular adenine nucleotide pattern was investigated in intact bovine spermatozoa. ATP consumption was manipulated by inhibition with vanadate and activation with caffeine, leading to a decrease or increase in the rate of respiration up to 70% or 20%, respectively. Oligomycin blocked the respiration to the same extent as did vanadate, suggesting that the total extramitochondrial ATP-consuming activity is vanadate-sensitive. The major part of ATP utilization must be linked to dynein ATPase, since inhibition of (Na+, K+) ATPase by ouabain showed only a small effect on respiration (-17%). Being a potent inhibitor of dynein ATPase, vanadate drastically reduced the amount of motile cells, whereas caffeine tended to increase the intensity of motion. The effects of vanadate or caffeine on respiration were paralleled by changes in cellular ATP, reflecting the response of mitochondrial respiration on the cellular ATP/ADP ratio. Respiration was found to depend on changes in the ATP/ADP ratio in the range from about 3 (+caffeine) to 9 (+vanadate). The range of response of ATP consumption to the ATP/ADP ratio was determined by varying the mitochondrial ATP production via the concentration of lactate which was used as substrate. The measured effects on both respiratory rate and ATP/ADP ratio suggested that ATP consumption was markedly dependent on ATP/ADP ratios below 5. It is concluded that lactate concentrations above 1 mM sufficiently supply bovine spermatozoa with substrate and the energy turnover is mainly limited by the activity of dynein ATPase rather than by the capacity of mitochondrial oxidative phosphorylation.

Mechanical hypothesis of sperm penetration

Sperm have generally been supposed to penetrate the zona pellucida surrounding the mammalian egg with the aid of a protease, acrosin. Difficulties associated with this view are discussed and an alternative, mechanical hypothesis introduced. The calculated force exerted by individual sperm is too small to permit the rupture of any but the weakest of secondary chemical bonds. Mechanical progress through the zona must rely on stress relaxation in a viscoelastic medium. The known properties of the zona appear to be consistent with such a mechanism of penetration.

Time course of the motion of bull sperm flagella

Detailed measurements were made of the time course of the motion of bull spermatozoa. Fourier analysis of the data showed the time course to be basically sinusoidal within 2% to 3%. An asymmetry in the motion was present, resulting in a second harmonic component in the Fourier spectra of normal sperm of approximately 11% of the main component. When the energy metabolism of the sperm was inhibited or when the external viscosity of the medium was raised, the asymmetry was reduced. When the internal Mg2+ content of the sperm was lowered, the asymmetry was increased. The asymmetries and the corresponding second harmonic components in the Fourier spectra were correlated with the overall bend shape of the sperm and with the curvature of the path in which the sperm were swimming. Model calculations showed that the asymmetry could reside in either the internal active moments in the sperms or in the stiffness of the sperm flagella.

Effect of the membrane active ionophore, nigericin, on motility of ram spermatozoa

Ram spermatozoa diluted in Ringer-fructose-phosphate to a concentration of 5 X 10(6) cells/ml, were exposed to continuous variations of pH, using HCl or NaOH. Percent of motility and ATP level were measured within 1-2 min from the pH change. High percent of motility was observed in the range of 2 pH units, between pH 6.5 to 8.5, regardless of the source of the ATP production: mitochondria, fructolysis, or both. In the presence of nigericin (H +/K+ exchanger), two peaks of high motility were observed: one at alkaline pH (7.8-8.3) and the other at acidic pH (6.5-7.0). When nigericin was added to cells inhibited by 2-deoxyglucose (possessing mainly mitochondrial motility), the high percent of motility was noted at the alkaline pH (7.2-7.6). However, when nigericin was added to cells inhibited by Antimycin-A (possessing mainly fructolytic motility), the high percent of motility was observed at the acid pH (6.0-6.7). The ATP level was correlated with the pattern of the motility.

A fluorometric-reflectometric technique for simultaneous measurement of pH and motility in ram semen

An optical technique for simultaneous assessment of pH and motility in ram semen was described. Motility was evaluated by the measurement of changes in intensity of reflected light from semen samples illuminated with 366 nm light. pH was measured by using a pH-sensitive fluorescent indicator (umbelliferone). From the changes in fluorescence intensity (450 nm) as a function of the pH of the semen, a calibration curve was constructed. The relationship between pH changes and motility in various metabolic conditions were described. Different kinetics for pH changes occurred when sperm motility was driven by both mitochondrial respiration and fructolysis or by either one of them. An analysis of the fluorescence signal from extracellular or cellular fractions of semen suggested that the pH measurement reflected extracellular pH.

The effect of pH on ram sperm collective motility driven by mitochondrial respiration

Ram sperm cells treated with 0.02 M 2-deoxy-D-glucose exhibit collective motility which is driven only by mitochondrial respiration. This motility was measured, by means of multichannel optical objective technique, under various [H+] concentrations (pH range 5.6-7.2) buffered by 0.125 M phosphate buffers. Semen was divided into 8 aliquots and motility was monitored simultaneously for intensity and duration within 10 min of ejaculation until its complete cessation. The optimal pH range found for the two above-mentioned parameters was in the range of 6.0-6.5. A certain characteristic of the pattern of sperm motility intensity (an oscillations phenomenon) was similarly related to pH. It is suggested that the mechanisms underlying the relationship between pH and motility are rather metabolic. Concerning the results, some practical implications are introduced.

A new optical technique for evaluating collective motility of ram and bull ejaculated spermatozoa

A new, non-destructive, objective technique for measuring collective motility of highly-concentrated ram and bull semen is described. The principle is based on changes in the reflected light scattered by motile spermatozoa. These changes can be recorded as a continuous analog wave pattern (Reflectospermiogram-RSG) and are correlated to the intensity of the turbulent motility as evaluated subjectively with an ordinary light microscope. Ram spermatozoa have, after ejaculation, a typical motility pattern, i.e., high, stable activity for about 20 min, then a period during which the motility decreases at a constant rate, and finally, a period with a low but rather constant activity. The usefulness of the technique has been demonstrated in various types of experiments.

Radiation damage to bull sperm motility. III. Further x-ray studies

The results of previous radiation experiments, which indicated that the centriole serves as a control center for bull sperm motility, appear to be in conflict with experiments showing that the bull sperm flagellum is an autonomous oscillator. To resolve this conflict experiments were conducted to calibrate absolutely the dose-response curves for the radiation damage, and to measure the force production and the mechanochemical energy conversion after irradiation in bull sperm. The results indicate that the centriole acts as a mechanical anchor for the contractile fibers.

Adenosine triphosphate-induced motility and sliding of filaments in mammalian sperm extracted with Triton X-100

Bull sperm that had been extracted with 0.2% Triton X-100 could be reactivated with ATP, and their movement closely resembled the motion of intact live sperm. Their motility required the presence of ATP, magnesium, and a medium of suitable salt concentration and pH. When Triton-extracted bull sperm were digested breifly with trypsin at pH 9.0, they appeared to reatin most of their normal structure, but subsequent exposure of the digested sperm to ATP caused a disintegration by light microscopy, using dark-field illumination, combined with an electron microscope study of preparations of the disintegrated sperm, demonstrated the presence of an active sliding mechanism of filament interaction in bull spermatozoa. Human sperm subjected to the same procedures showed similar patterns of reactivation and of disintegration.