The effect of temperature on the velocity of human spermatozoa as measured by time-lapse photography

Effect of incubation and analysis temperatures on sperm kinematics and morphometrics during human semen analysis

INTRODUCTION

Human semen analysis must be performed after the liquefaction of the ejaculate. This takes place about 30min after ejaculation and samples must be maintained in the lab during this time. The temperatures for this incubation and the final analysis of motility are crucial but seldom taken into account. This study aims to examine the effect of these temperatures on various sperm parameters both manually (sperm count, motility, morphology, viability, chromatin condensation and maturation and DNA fragmentation) and CASA (kinematics and morphometrics, using an ISAS®v1 CASA-Mot and CASA-Morph systems, respectively) analyzed.

METHODS

Seminal samples from thirteen donors were incubated for 10min at 37°C followed by additional 20min at either room temperature (RT, 23°C) or 37°C and then examined following WHO 2010 criteria.

RESULTS

The data obtained show that there were no significant differences (P>0.05) in the subjective sperm quality parameters with incubation temperature. On the other hand, the head sperm morphometric parameters were significantly higher after room temperature incubation showing, in addition, lower ellipticity (P<0.05). Furthermore, kinematic parameters were evaluated both at RT and 37°C for the two incubation temperatures. In general, the four temperature combinations showed that kinematic parameters followed this order: RT-RT<RT-37<37-37<37-RT (incubation and analysis temperatures respectively).

CONCLUSIONS

Our results showed that temperature control during both incubation and analysis is needed for accurate semen analysis, recommending the use of 37°C during the entire process.

Manual methods for sperm motility assessment

Progressive motility is a vital functional characteristic of ejaculated human spermatozoa that governs their ability to penetrate into, and migrate through, both cervical mucus and the oocyte vestments, and ultimately fertilize the oocyte. A detailed protocol, based on traditional manual/visual methods, is provided for performing an accurate four-category differential count including the reliable identification of rapid progressive (grade "a") spermatozoa-the most biologically, and hence clinically, important subpopulation. Thorough prior training and the use of a microscope fitted with a heated stage are both essential requirements for achieving accuracy and an acceptable uncertainty of measurement of no more than ±10%.

Development of a novel home sperm test

BACKGROUND

The majority of men find the production of a semen sample an embarrassing and stressful experience. Consequently, the availability of an over-the-counter home sperm test, which would reliably and accurately allow the patient to obtain an assessment of fertility potential at their convenience, would be a major benefit. Our objective was to develop and evaluate a home sperm test that provides a visual estimate of the concentration of progressively motile sperm in a semen sample.

METHODS

Three particular challenges are described (i) developing a visualization system; (ii) optimization of the detection limit; and (iii) controlling variation due to changes in ambient temperature. The accuracy of the device was tested against two reference methods: computer-assisted sperm analysis (CASA) and a hyaluronate migration test (HMT).

RESULTS

In 129 semen samples, where both reference methods agreed (positive or negative), the accuracy of the device was 95%. The observed likelihood ratio of 8.8 indicated that a sample showing a red line in the device was over eight times more likely to have a positive (normal) result in CASA and HMT than a sample without a red line.

CONCLUSIONS

The final device provides a visual estimate of the concentration of progressively motile sperm in a semen sample using a test that is completed within approximately 1 h of production of the sample and can be used by the man in the comfort of his own home.

Controlling the swimming speed of human sperm by varying the incubation temperature and its effect on cervical mucus penetration

The objective of the present experiments was to study the effect of sperm velocity as a single variable on the ability of sperm to penetrate cervical mucus in a modified Kremer test. Sperm incubated at 13, 22 and 37 degrees C exhibited progressive velocities of 25 +/- 1.7, 40 +/- 2.1 and 56 +/- 2.1 microns sec-1 (mean +/- SEM, n = 6) respectively, but the percentage of progressively motile sperm, their lateral head displacement and the viscoelastic properties of cervical mucus remained comparatively unchanged over this temperature range. The number of sperm which penetrated the mucus and the percentage of successful collisions were correlated strongly with the average velocity of the sperm population (r = 0.82 and r = 0.72 respectively). It is concluded that sperm velocity has an important influence on the penetration of cervical mucus because it governs the frequency of collisions with the mucus interface and is determined by the thrust generated by the flagellum which also determines the ability of the sperm to traverse the mucus interface.

Dynamic laser light scattering compared with video micrography for analysis of sperm velocity and sperm head rotation

A new method which allows separation of the rotational and translational components of human sperm motility, based on the angular dependence of the dynamic laser light scattering (DLS) has been developed. The technique was used in a clinical study and was compared with an independent evaluation by video micrography. A good correlation was found between the two techniques when applied on different semen samples (r = 0.90; P less than 0.01 and r = 0.96; P less than 0.01 for rotation and translation, respectively) and when applied on the same semen sample at different temperatures. The rapid evaluation of these parameters using DLS technique opens the possibility to study large number of semen samples under physiological and pathological conditions at a lower cost.

Assessment of sperm motion characteristics from fertile and infertile men using a fully automated computer-assisted semen analyzer

Sperm curvilinear velocity (Vc) and linearity (L) were analyzed in semen from 20 fertile men and from 53 patients with unexplained infertility by a computer-assisted semen analyzer (CASA). Because the frequency distribution of Vc from patient's spermatozoa showed a nongaussian distribution, comparison of mean values of Vc and L between men with unexplained infertility and fertile men is inappropriate. As an alternative, the authors compared the cumulative distribution of the percent of cells measured at increasing intervals of Vc and L, and observed a significant difference between patients and fertile men from the level of Vc30 through Vc70 micron/sec for curvilinear velocity and L2 through L6 for linearity (P less than 0.001). Furthermore, the authors coanalyzed these two parameters at the greatest point of difference (Vc40 and L3) and observed that their patient population can be differentiated into four subpopulations of subjects accordingly to their Vc40 and L3 values. In this study, 43 of the 53 patients had a motility disorder characterized by having a higher percent of cells being substantially slower and less directional than cells from normal men. However, in some patients, motion characteristics were indistinguishable from those in normal men.

Determination of human sperm count and sperm motility using a laser beam and the Doppler effect (LAZYMOT machine)

For 25 consecutive human semen samples, a comparison was made of sperm count and sperm motility values obtained by routine manual methods and by using a machine that measures these functions by analysing the deflection of an impinging laser beam (Lazymot machine). Sperm counts in undiluted semen were approximately 5 times higher with the laser machine. As sperm counts increased to about 300 million/ml the counts obtained by the two methods converged as the chance of the beam hitting a spermatozoon and not another type of particle increased. In semen diluted 1 + 4 with Baker's solution, the uncorrected laser count agreed well with the sperm count obtained using a haemocytometer. Multiplication of the laser count by 5 did not reach the same count as that measured in the undiluted sample, showing that the dilution had dissolved some of the smaller particles. It was recommended to measure laser percentage motility in undiluted semen but the values obtained bore no relationship to those obtained using a haemocytometer and neither did the values obtained for laser percentage sperm with progressive motility. The mean laser velocity of the total motility was 23-64 micron/sec and for the progressive particles was 48-84 micron/sec, values which were much faster that the acceptably normal values of 8-30 micron/sec found for selected progressively motile spermatozoa timed with a stopwatch. The laser machine detected an increase in counts and the presence of residual motility after cytoplasm had been stripped away from the spermatozoa with a saponin reagent. The laser machine was unable to detect any increase in speed on increasing the temperature to 37 degrees C. It was concluded that the Lazymot machine as presently designed is not useful in the andrological laboratory for routine counting and motility determinations, mainly due to the absence of a size discriminator against the multitude of small particles that are present in human semen.

Factors affecting the variability of semen analysis results in infertile men

Infertile men who had 3 or more semen analyses performed in one laboratory were placed in 2 groups (I) oligozoospermic group (n = 106), mean sperm concentration between 1 and 20 million/ml (II) asthenozoospermic group (n = 71), mean sperm concentration greater than 20 million/ml, and mean motility less than 60%. With increasing durations of abstinence from ejaculation before the tests there were significant increases in semen volume and sperm concentration. Semen volume increased over the first 4 days to a similar extent in both groups. Sperm concentrations increased over 15 days, but the effect of abstinence was much greater in the asthenozoospermic group than in the oligozoospermic group (14% compared with 1.4% of the within subject variation). Significant changes in results accompanied repeated testing, notably rises in sperm concentration and motility. Sperm motility was lower in winter and higher in summer in both groups and also, but to a lesser extent, in artificial insemination donors who collected semen in the laboratory.

CONCLUSIONS

duration of abstinence, the elapse of time and seasonal temperature changes affect semen analysis results, and therefore controls for these variables must be incorporated in any therapeutic trial for male infertility. On the other hand, they only account for a small proportion of the total variability and thus routine correction of results would not greatly improve the value of semen analysis in the prediction of fertility. Furthermore because differences in the duration of abstinence have only a small effect on sperm concentration in oligozoospermic men, restricting sexual intercourse to the time of ovulation may not enhance fertility.

Optimum measurement time for human sperm velocity determination

The optimal time-duration required by spermatozoa to travel distances from which their average velocity can be accurately determined was investigated. For this purpose, 180 motile spermatozoa, from 12 seminal specimens, were photographed while being illuminated by six light pulses, given at 1-sec intervals. From these photographs, distances traveled by each spermatozoon were measured over identical time periods. Most individual spermatozoa showed slight deviation of their velocity when measured sequentially for 5 sec. Nevertheless, when mean sperm velocity of grouped spermatozoa were determined from 1- or 5-sec measurement time, the results were almost identical. This was attributed to a pure statistical law, that is, the mean deviation decreases as the number of spermatozoa in the sample increases. It was concluded that the sperm velocity of a certain specimen can be determined properly using a 1-sec measurement time. An extended period of time does not seem to contribute to the accuracy of sperm velocity determination.

Use of the elaborated multiple exposure photography (MEP) method in routine sperm motility analyses and for research purposes

Elaboration of the three basic components incorporated in the recently developed multiple exposure photography (MEP) method for objective sperm motility determination is described. This includes an improved version of the 10-micrometers counting chamber, modified procedures of photography, and a system for easier calculation of the results. During the last 2 years several thousands of sperm motility analyses were performed with the elaborated technique. In our institute this method has totally replaced motility evaluation by subjective estimation and has become the sole method for semen assessment performed during routine clinical work-up and research studies. This method is compared with other still-camera photographic techniques, and data about duration of performance, details of the relatively low cost of analysis, and specifications of some of its components are presented as well.