Analysis of motility parameters from paddlefish and shovelnose sturgeon spermatozoa

Ninety to 100% of paddlefish Polyodon spathula were motile just after transfer into distilled water, with a velocity of 175 μm s^-1, a flagellar beat frequency of 50 Hz and motility lasting 4–6 min. Similarly, 80–95% of shovelnose sturgeon Scaphirhynchus platorynchus spermatozoa were motile immediately when diluted in distilled water, with a velocity of 200 μm s^-1, a flagellar beat frequency of 48 Hz and a period of motility of 2–3 min. In both species, after sperm dilution in a swimming solution composed of 20 mM Tris–HCl (pH 8·2) and 20 mM NaCl, a majority of the samples showed 100% motility of spermatozoa with flagella beat frequency of 50 Hz within the 5 s following activation and a higher velocity than in distilled water. In such a swimming medium, the time of motility was prolonged up to 9 min for paddlefish and 5 min for sturgeon and a lower proportion of sperm cells had damage such as blebs of the flagellar membrane or curling of the flagellar tip, compared with those in distilled water. The shape of the flagellar waves changed during the motility phase, mostly through a restriction at the part of the flagellum most proximal to the head. A rotational movement of whole cells was observed for spermatozoa of both species. There were significant differences in velocity of spermatozoa between swimming media and distilled water and between paddlefish and shovelnose sturgeon.     

Effects of osmolality, morphology perturbations and intracellular nucleotide content during the movement of sea bass (Dicentrarchus labrax) spermatozoa.

Sea bass spermatozoa are maintained immotile in the seminal fluid, but initiate swimming for 45 s at 20 degrees C, immediately after dispersion in a hyperosmotic medium (1100 mOsm kg-1). The duration of this motile period could be extended by a reduction of the amplitude of the hyperosmotic shock. Five seconds after the initiation of motility, 94.4 +/- 1.8% of spermatozoa were motile with a swimming velocity of 141.8 +/- 1.2 microns s-1, a flagellar beat frequency of 60 Hz and a symmetric type of flagellar swimming, resulting in linear tracks. Velocity, flagellar beat frequency, percentage of motile cells and trajectory diameter decreased concomitantly throughout the swimming phase. After 30 s of motility, the flagellar beat became asymmetric, leading to circular trajectories. Ca2+ modulated the swimming pattern of demembranated spermatozoa, suggesting that the asymmetric waves produced by intact spermatozoa after 30 s of motility were induced by an accumulation of intracellular Ca2+. Moreover, increased ionic strength in the reactivation medium induced a dampening of waves in the distal portion of the flagellum and, at high values, resulted in an arrest of wave generation in demembranated spermatozoa. In non-demembranated cells, the intracellular ATP concentration fell immediately after transfer to sea water. In contrast, the AMP content increased during the same period, while the ADP content increased slightly. In addition, several morphological changes affected the mitochondria, chromatin and midpiece. These results indicate that the short swimming period of sea bass spermatozoa is controlled by energetic and cytoplasmic ionic conditions and that it is limited by osmotic stress, which induces marked changes in cell morphology.     

Mechanochemical Coupling in Flagella : II. Effects of viscosity and thiourea on metabolism and motility of Ciona spermatozoa

The relation between oxygen consumption and motility of Ciona spermatozoa has been measured by using pH stats to measure the acid production of spermatozoa swimming in dilute suspensions where their motility can be analyzed accurately, and calibrating the acid production by measuring it simultaneously with measurements of oxygen consumption, using more concentrated sperm suspensions. When the motility of the spermatozoa is inhibited by thiourea or by increased viscosity, their oxygen consumption decreases in proportion to the decrease in beat frequency. 80–85 % of their oxygen consumption appears to be tightly coupled to motility. The amount of movement-coupled oxidative metabolism per beat remains nearly constant, even when there are significant changes in the energy required per beat for movement against the viscous resistance of the medium. This implies that under these conditions, where the radius of curvature of flagellar bending remains constant, the amount of ATP used is determined by a stoichiometric relation to bending rather than by the energy requirement. The movement-coupled oxidative metabolism appears to be sufficient to generate approximately two molecules of ATP per beat for each molecule of the flagellar ATPase, dynein.     

The movement characteristics of rabbit spermatozoa before and after activation

Spermatozoa were flushed with mineral oil from the lower isthmus of the rabbit oviduct at four hours postcoitus (pc) and 11 hours pc. Videotapes were made of sperm behavior in the native isthmic fluid and after dilution of the fluid with culture medium. The tapes showed that, initially, spermatozoa in the native isthmic fluid were virtually immotile, but immediately resumed movement on contact with the culture medium. Isthmic sperm motility then evolved over a five- to 10-minute interval into the characteristic biphasic pattern of activated movement. Cine films of isthmic spermatozoa taken with a high-speed camera were analyzed to determine flagellar beat frequency, maximum flagellar curvature, and swimming velocity. Progressiveness ratios and hydrodynamic power outputs were then calculated for individual spermatozoa. Two phases of activated sperm movement, a whiplash phase and a progressive phase, were identified and characterized. The power output of activated spermatozoa increased twentyfold in comparison with the preactivated state. The power output of activated spermatozoa did not differ between the two phases of activated movement.     

Comparative analysis of movement characteristics of lancelet and fish spermatozoa having different morphologies

The movement characteristics of the sperm and their flagella obtained from a lancelet and 35 species from almost all orders of fishes were examined using high-speed video microscopy. The aim was to clarify the relationship between the motility parameters of the spermatozoa having different morphologies and how these motility parameters affect the swimming speed of the spermatozoa. The motility parameters representing the flagellar waveform, the wavelength, and the amplitude were neither very different between the spermatozoa of the different species nor related to the swimming speed. In contrast, the beat frequency was remarkably changed in the different spermatozoa and was proportional to the swimming speed. The maximum shear angle of the flagellar wave, which is directly related to the maximum sliding displacement between the doublet microtubules, remained nearly constant while the beat frequency varied widely; therefore, the spermatozoa beat in the constant sliding displacement mode. An analysis of the relationship between swimming speed and flagellar length revealed that short flagella were at a disadvantage in developing swimming speed; however, so were extra-long flagella. The ratio of the swimming speed to the wave velocity calculated from the wavelength and the beat frequency depended on the distance from the glass surface. The swimming speeds calculated using the original resistive-force theory were greater than the measured values. To rationalize the measured values, the ratio between the normal and tangential drag coefficient in the resistive-force theory was corrected; namely, 1.99 at 1 μm and 1.63 at 3 μm from the glass surface.     

Effects of osmolality on sperm morphology, motility and flagellar wave parameters in Northern pike (Esox lucius L.)

Northern pike (Esox lucius L.) spermatozoa are uniflagellated cells differentiated into a head without acrosome, a midpiece and a flagellar tail region flanked by a fin structure. Total, flagellar, head and midpiece lengths of spermatozoa were measured and show mean values of 34.5, 32.0, 1.32, 1.17 μm, respectively, with anterior and posterior widths of the midpiece measuring 0.8 and 0.6 μm, respectively. The osmolality of seminal plasma ranged from 228 to 350 mOsmol kg⁻¹ (average: 283.88 ± 33.05). After triggering of sperm motility in very low osmolality medium (distilled water), blebs appeared along the flagellum. At later periods in the motility phase, the tip of the flagellum became curled into a loop shape which resulted in a shortening of the flagellum and a restriction of wave development to the proximal part (close to head). Spermatozoa velocity and percentage of motile spermatozoa decreased rapidly as a function of time postactivation and depended on the osmolality of activation media (P < 0.05). In general, the greatest percentage of motile spermatozoa and highest spermatozoa velocity were observed between 125 and 235 mOsmol kg⁻¹. Osmolality above 375 mOsmol kg⁻¹ inhibited the motility of spermatozoa. After triggering of sperm motility in activation media, beating waves propagated along the full length of flagella, while waves appeared dampened during later periods in the motility phase, and were absent at the end of the motility phase. By increasing osmolality, the velocity of spermatozoa reached the highest value while wave length, amplitude, number of waves and curvatures also were at their highest values. This study showed that sperm morphology can be used for fish classification. Sperm morphology, in particular, the flagellar part showed several changes during activation in distilled water. Sperm motility of pike is inhibited due to high osmolality in the seminal plasma. Osmolality of activation medium affects the percentage of motile sperm and spermatozoa velocity due to changes in flagellar wave parameters.     

Trypanosomes and mammalian sperm: one of a kind?

Flagellar-mediated motility is an indispensable function for cell types as evolutionarily distant as mammalian sperm and kinetoplastid parasites, a large group of flagellated protozoa that includes several important human pathogens. Despite the obvious importance of flagellar motility, little is known about the signalling processes that direct the frequency and wave shape of the flagellar beat, or those that provide the motile cell with the necessary environmental cues that enable it to aim its movement. Similarly, the energetics of the flagellar beat and the problem of a sufficient ATP supply along the entire length of the beating flagellum remain to be explored. Recent proteome projects studying the flagella of mammalian sperm and kinetoplastid parasites have provided important information and have indicated a surprising degree of similarities between the flagella of these two cell types.     

Trout sperm motility. The transient movement of trout sperm is related to changes in the concentration of ATP following the activation of the flagellar movement

For freshwater fish the motile period of sperm is extremely brief, even after a dilution in isotonic media. This result is in contrast to most other animals (ranging from invertebrates to mammals), in which sperm are generally motile for at least several hours. We have analyzed the reasons for the brevity of this movement by studying the relationships between the metabolism of trout sperm and the activation of their motility upon dilution. Sperm motility was not initiated when the dilution medium contained an elevated concentration of potassium (20-40 mM), but dilution in an isotonic solution of sodium chloride triggered an immediate activation of motility, and sperm swam vigorously. Motility of sperm decreased rapidly and 15 s after dilution sperm were moving slowly in small circles. Sperm became abruptly immotile at 20-30 s and flagella straightened. When millimolar concentrations of Ca2+ were also present in the dilution medium, movement did not stop abruptly, flagella kept beating and stopped only after 1-2 min. When sperm remained immotile they retained a high concentration of ATP. The activation of motility induced a rapid decrease of ATP. In the absence of calcium, and after the cessation of motility, ATP increased slowly back to its original concentration. In the presence of millimolar concentrations of calcium the concentration of ATP decreased to a very low level and remained low thereafter. The progressive decrease of the flagellar beat frequency, that had been observed during the period of trout sperm movement, might be related to the rapid exhaustion of intraflagellar ATP. Motility could be reinduced in sperm that had recovered high concentrations of ATP, demonstrating the functional integrity of the motile apparatus even after flagellar arrest. In conclusion we suggest that the maximum duration of trout sperm motility, at most 2 min (as a consequence of a depletion of ATP during the movement), is due to a low mitochondrial oxidative phosphorylation capacity.     

Kinematics of human spermatozoa

A microcinematographic (50 f/s) study was performed on motile human spermatozoa. Eighty percent were found to have a linear trajectory and a pseudo-sinusoidal head displacement pattern. Throughout their progression, the spermatozoa periodically rotated on their longitudinal axis at a frequency equal to that of flagellar wave formation. These waves were found always to begin on the same side of the cell and to propagate in the flattened plane of the head until the moment of rotation. At this time the wave had reached a point near the middle of the flagellum. Beyond this point, the flagellum moves out of the plane of the head. Different variables used to characterize the movement of spermatozoa included the velocity of progression, amplitude and velocity of head displacement, frequency of rotation, wave amplitude, and propagation velocity of the flagellar wave. Among these variables, it was the propagation velocity of the wave that was found to be best correlated with the velocity of spermatozoan progression. This flagellar wave exhibited two stages, one of initiation and one of propagation.     

Evolution of the flagellar waveform of ram spermatozoa in relation to the degree of epididymal maturation.

Motility and flagellar movement of ram spermatozoa along the epididymis were analysed in vitro. From the caput to the cauda of the epididymis, the percentage of motile and progressive spermatozoa increases. No flagellar bending was observed in spermatozoa from the testis or the epididymal anterior caput. When spermatozoa reached the distal caput of the epididymis, a static curvature, associated with an initiation of the flagellar beating, appeared on the flagella. This curvature normally disappeared during epididymal transit. Its disappearance was associated with an increase in the flagellar beat efficiency. Our results suggest that the initiation of motility is related to two mechanisms involving: (1) the presence of a transient static curvature, and (2) the establishment of a symmetric regular beating of the flagellum.     

Kinematics of hamster sperm during penetration of the cumulus cell matrix

During capacitation, mammalian spermatozoa gain the ability to penetrate the cumulus cell matrix (CCM). The role of hyperactivated motility for this capacity is uncertain. In the present study, hamster sperm were observed during penetration and progression through the CCM, and flagellar beat patterns were quantitated by characterization of the underlying flagellar bends. Small numbers of sperm were added to cumulus masses slightly compressed on a slide (150 μm depth), and penetration was videorecorded using interference contrast optics. During penetration of the cumulus surface, sperm did not generate the large flagellar bends and asymmetric beats that are hallmarks of hyperactivation in low viscosity media. Instead, they entered slowly using high-frequency, low-amplitude sinusoidal flagellar motions. Within the CCM, sperm continued to move slowly, and they exhibited three distinct patterns of motility. The first was sinusoidal, produced by alternating, propagated bends: principal bends (PB) moved the head away from the beat midline, with the convex edge of the head leading, and reverse bends (RB) had the opposite curvature. The second pattern was asymmetric and sinusoidal: an extreme RB developed in the distal flagellum, was propagated distally, and was followed by a PB of less curvature. The third motility pattern was a hatchet-like stroke of the sperm head which resulted when an extreme, nonpropagated PB developed slowly in the proximal midpiece, and was released rapidly. In this mode there were no reverse bends, and sperm did not progress. There were subpopulations of capacitating sperm in free-swimming medium which had these same bend types and motility patterns, suggesting that qualitative flagellar movement may not change during CCM penetration. Sperm velocity in the CCM was not strongly correlated with flagellar beat kinematics, suggesting local heterogeneity in cumulus mechanical resistance and/or differences in interaction of the matrix with the surfaces of individual sperm. An effective viscosity of the cumulus near its border was estimated to be of the order of 1–4 P.     

Glycolysis plays a major role for adenosine triphosphate supplementation in mouse sperm flagellar movement

The mammalian sperm must be highly motile for a long time to fertilize a egg. It has been supposed that ATP required for sperm flagellar movement depends predominantly on mitochondrial respiration. We assessed the contribution of mitochondrial respiration to mouse sperm motility. Mouse sperm maintained vigorous motility with high beat frequency in an appropriate solution including a substrate such as glucose. The active sperm contained a large amount of ATP. When carbonyl cyanide m-chlorophenylhydrazone (CCCP) was applied to suppress the oxidative phosphorylation in mitochondria, the vigorous motility was maintained and the amount of ATP was kept at the equivalent level to that without CCCP. When pyruvate or lactate was provided instead of glucose, both sperm motility and the amount of ATP were high. However, they were drastically decreased when oxidative phosphorylation was suppressed by addition of CCCP. We also found that sperm motility could not be maintained in the presence of respiratory substrates when glycolysis was suppressed. 2-Deoxy-d-glucose (DOG) had no effect on mitochondrial respiration assessed by a fluorescent probe, 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine iodide (JC-1), but, it inhibited motility and decreased ATP content when pyruvate or lactate were provided as substrates. The present results suggest that glycolysis has an unexpectedly important role in providing the ATP required for sperm motility throughout the length of the sperm flagellum.     

Effect of the human cumulus oophorus on movement characteristics of human capacitated spermatozoa

The effect of human cumulus oophorus on movement characteristics of human spermatozoa previously incubated in vitro under capacitating conditions was studied using automated digital image analysis. When spermatozoa were incubated for a short time with whole cumuli, most of those that penetrated the cumulus intercellular matrix were characterized by a linear movement with small amplitudes of lateral head displacement, but with elevated values of beat cross frequency. Short (5 min) incubation with solubilized cumulus intercellular matrix of spermatozoa preincubated in capacitating conditions (6 h) significantly reduced the percentage of spermatozoa showing the 'hyperactivated' type of motility characterized by high curvilinear velocity, low progressive velocity and elevated values of lateral head displacement. Moreover, a subpopulation of spermatozoa with very high values of progressive velocity and beat cross frequency and with reduced amplitudes of lateral head displacement appeared in these conditions. This cumulus-related motility pattern was not seen in fresh spermatozoa or in those incubated in the absence of cumulus material. Changes in the sperm movement characteristics similar to those observed in the presence of the solubilized cumulus matrix could also be induced by some of its h.p.l.c. fractions. These results show that the intercellular matrix of the human cumulus oophorus exerts a specific effect on human sperm motility, probably acting preferentially on the 'hyperactivated' sperm subpopulation.     

Decrease of internal free calcium and human sperm movement

In order to elucidate the effects of calcium on the movement of human spermatozoa, studies were conducted using motile cells selected by swim-up migration at 37 degrees C in 5% CO2 in air in a synthetic BWW medium containing 1.7 x 10(-3) M CaCl2 or BWW without added calcium (BWW-Ca). Preliminary experiments have confirmed that the addition of EGTA (5 x 10(-3); 10(-2) M) to BWW medium decreased the intracellular calcium concentration ((Ca++)i) of spermatozoa, as measured in cells loaded with a fluorescent Ca++ indicator, Quin-2. Concomitant measurements of (Ca++)i and sperm movement (analysed by videomicrography at 200 f/s at room temperature) were carried out on Quin-2 loaded cells incubated in BWW-Ca medium plus EGTA (10(-5) M; 10(-4) M; 10(-3) M). Under these conditions a decrease in (Ca++)i was observed and associated with a decrease in mean amplitude of lateral head displacement (ALH). Analysis using an automatic analyser (Hamilton Thorn at 37 degrees C) confirmed these results: the percentage of spermatozoa swimming with ALH greater than or equal to 6 microns is decreased when the external free calcium in BWW-Ca is decreased by the addition of 10(-5) M, 10(-4) M, or 10(-3) M EGTA. Flagellar analysis of the sperm population characterized by ALH greater than or equal to 6 microns showed a large proximal curvature of the tail associated with a low propagation wave velocity and a low beat frequency as compared to the spermatozoa with ALH less than 6 microns with similar progressive velocities. These characteristics result in a high flagellar beat efficiency (in terms of head displacement per beat). The disappearance of this pattern of movement when intracellular calcium is lowered indicates that calcium plays a complex role in the relationship between curvature and wave propagation. The ability of spermatozoa to modulate their movement in response to an alteration in the intracellular calcium level confirms the role of calcium in controlling flagellar movement in intact cells.     

Flagellar movement of intact and demembranated, reactivated ram spermatozoa

The flagellar movement of intact ejaculated ram sperm, and of demembranated models reactivated with ATP, has been studied using high-speed, high-resolution video microscopy. Intact sperm attached to the coverslip by their heads had an average beat frequency of 20.9 Hz and an average wave amplitude of 20.2 micron. There was little difference in the beat frequency or waveform of these sperm and sperm swimming freely near the coverslip or captured by their heads with a micropipette and held far from the coverslip, indicating that the flagellar waveform of ram sperm is relatively resistant to distortion as a result of immobilization of the head or proximity to a surface. The beat envelope was nearly planar as determined by observations of free-swimming sperm and sperm captured by their head and oriented so they were beating either parallel or perpendicular to the plane of focus. The effect of various conditions for demembranation and reactivation of the sperm were examined. Treatment of sperm with 0.2% Triton X-100 removed most of their plasma membrane. Under optimal conditions, nearly 100% of the demembranated sperm reactivated at MgATP2- concentrations ranging from approximately 4 microM to approximately 20 mM. From approximately 1 mM to approximately 10 mM MgATP2-, their beat pattern closely resembled that of intact sperm; beat frequency depended on MgATP2- concentration. Percent motility was maximal between pH 7.5 and 8.0 and decreased sharply below pH 7.0 and above pH 8.5. The addition of 50 microM cAMP to the reactivation medium had no effect on percent motility or the beat pattern and did not accelerate the initiation of movement.     

F-actin involvement in guinea pig sperm motility

Sperm motility is a must for natural fertilization to occur. During their travel through the epididymis, mammalian spermatozoa gradually acquire the ability to move. This is accomplished through a sliding movement of the outer doublet microtubules of the axoneme which is energized by the dynein ATPase. Within its complex structure, the mammalian sperm flagellum contains F-actin and thus, we decided to test in the guinea pig sperm flagellum the role of F-actin in motility. During maturation, capacitation, and the acrosome reaction, a gradual decrease of the relative concentration of F-actin was observed. Motility increased as spermatozoa became able to fertilize. Gelsolin, phalloidin, and KI inhibited sperm motility. Gelsolin canceled sperm motility within 20 min of treatment while 0.6 M KI had immediate effects. Phalloidin diminished hyperactive sperm motility slightly. All three compounds significantly increased the relative concentration of F-actin. Latrunculins are conventional drugs that destabilize the F-actin cytoskeleton. Latrunculin A (LAT A) did not affect sperm motility; but significantly increased F-actin relative concentration. The results suggested that in guinea pig spermatozoa, randomly severing F-actin filaments inhibits flagellar motility; while end filament alteration does not. Thus, specific filament regions seem to be important for sperm motility.     

Synchronous triggering of trout sperm is followed by an invariable set sequence of movement parameters whatever the incubation medium.

The movement of live trout spermatozoa is very brief (25 sec at 20 degrees C) and conditions have been developed to get synchronous initiation of sperm motility which allowed quantification of the major parameters of sperm movement during the motility phase. Recorded flagellar beat frequencies decreased steadily from values of 55 Hz at the beginning to 20 Hz at the end of the motility phase. Sperm forward velocities followed a similar pattern from 250 to 20 microns.sec-1 in the same conditions and the diameters of sperm trajectories were reduced from 370 to 40 microns. Thus none of the characteristics of sperm movement was constant during the motile phase which ended abruptly by a straightening of the flagella. The decrease in flagellar beat frequencies and sperm velocities are much greater than what could be extrapolated from the decrease of intracellular ATP (Christen R. et al: Eur. J. Biochem, 166: 667-671, 1987) or from measurements of ATP-dependence of reactivated sperm velocities (Okuno M. and Morisawa N.: In Biological Functions of Microtubules and Related Structures. New York: Academic Press, pp. 151-162, 1982). Therefore, the cessation of flagellar beating at 25 sec is not directly the result of the low concentration of intracellular ATP. The decrease in the diameters of sperm trajectories which occurred during the first part of the motility phase was correlated with [Ca]i measurements (Cosson M.P. et al, Cell Motil. Cytoskeleton, 14:424-434, 1989). The effect of Ca2+ at the axonemal level does not indicates that Ca2+ influx is previous to flagellar beating but rather suggests a classical Ca2+ regulation of the flagellar assymetry. The short duration of the motility phase and the characteristics of sperm movement were very similar in various conditions (high external K+, low pH media) where increased external Ca2+ or divalent ions were shown to overcome K+ and H+ inhibition of sperm motility, both conditions which have been shown to depolarize the plasma membrane potential (Gatti J.L. et al: J. Cell Physiol., 143:546-554, 1990). The present study of the parameters of sperm movement suggests that once motility is initiated, a defined set of axonemal events will take place whatever the external conditions.     

Studying sperm motility in marine fish: an overview on the state of the art

This contribution reviews existing literature and some new own findings on teleost sperm motility and factors controlling it, emphasizing selected marine species. In marine teleosts with external fertilization (halibut, turbot, sea bass, hake, cod and tuna serving as examples), mainly the osmolality controls sperm motility: movement is activated by transfer from the seminal fluid into sea water, representing a large upward step in osmolality. The exception are flatfishes (such as halibut or turbot) where CO₂ is responsible for flagellar immotility in seminal fluid. In all cases, the duration of motility is short and limited to minutes ranges due to partial exhaustion of the ATP energy and to increase of internal ionic concentration as suggested by studies with de‐membranated/ATP reactivated flagellae. In this overview, we compare motility characteristics (percentage of active spermatozoa, velocity, linearity), flagellar waves parameters (wave length and amplitude, number of waves) and energy content (respiration and ATP concentration) within species where these data have been established. All parameters show a rapid decrease after activation; therefore progressive forward movement needed by the sperm to effectively reach the egg surface, is limited to a short initial period following activation. In two species (turbot and sea bass) the rapid decrease of sperm motility is reflected by a corresponding decrease of the fertilizing ability. Exposure to external environments (sea water) at activation also leads to local defects of the sperm flagella posing additional limitations on motility duration. However, minor flagellar damages as well as energetic exhaustion are reversible: after a resting period in a non‐swimming solution at the end of the motility period, spermatozoa can be re‐activated for a second motility period. From these results and from additional data obtained from de‐membranated/ATP re‐activated spermatozoa, a paradigm has been developed which establishes a link between external osmolality (sea water), internal ionic concentration and control of axonemal activity.     

The velocity of microtubule sliding: its stability and load dependency

It is now well understood that ATP-driven active sliding between the doublet microtubules in the sperm axoneme generates flagellar movement. However, much remains to be learned about how this movement is controlled. Detailed analyses of the flagellar beating of the mammalian spermatozoa revealed that there were two beating modes at a constant rate of microtubule sliding: that is, a nearly constant-curvature beating in nonhyperactivated spermatozoa and a nearly constant-frequency beating in hyperactivated spermatozoa. The constant rate of microtubule sliding suggests that the beat frequency and waveform of the flagellar beating are dependently regulated. Comparison of the sliding velocity of several mammalian and sea urchin sperm flagella with their mechanical property clarified that the sliding velocity of the microtubule was determined by the stiffness of the flagellum at its base, and that its relationship was expressed by a logarithmic equation that is similar to the classical force-velocity equation of the muscle contraction. Data from sea urchin spermatozoa also satisfied the equation, suggesting that the same microtubule sliding system functions in both the mammalian and echinoderm spermatozoa.     

鱼类精子活力研究进展

鱼类精子在精巢和精浆中一般不活动,只有当精子被排到体外并被外界环境的溶液稀释后才能活动．鱼类精子活力受渗透压、离子、ｐＨ 值、温度及ＣＯ２ 等因子的调节和影响, 不同的鱼类其精子活力有不同的调节方式;外界因子对鱼类精子活力的影响, 是通过影响ｃＡＭＰ－ＡＴＰ－Ｍｇ２＋ 系统来影响鞭毛的活动而实现的． 精子活力的评价指标主要有：精子激活后的运动时间、精子激活比例、精子运动速度及精子鞭毛摆动频率等． 大多数鱼类的精子,其活动能力是在生殖管道中获得的．