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D F Katz

Publications and source records attributed to D F Katz.

At least 37 records · Page 2Linked to original sources
PubMed1991

Evidence for the function of hyperactivated motility in sperm.

After insemination, mammalian sperm undergo a striking change in flagellar beat pattern, termed hyperactivation. In low-viscosity culture medium, nonhyperactivated sperm flagella generate relatively symmetrical, low-amplitude waves, while hyperactivated sperm flagella generate an asymetrical beating pattern that results in nonprogressive movement. Since sperm encounter highly viscous and viscoelastic fluids in the female reproductive tract, the progress of hyperactivated sperm was compared with that of nonhyperactivated and transitional sperm in media of increasing viscosity. Hamster sperm obtained from the caudal epididymis were incubated in a medium that promotes capacitation. After 0, 3, and 4 h of incubation, the majority of the sperm exhibited, respectively, activated, transitional, and hyperactivated motility. At each of these time points, aliquots of sperm were removed from incubation and added to solutions of 0, 5%, 10%, 20%, and 30% Ficoll in medium. Samples containing mostly hyperactivated sperm (4 h) maintained higher swimming and flagellar velocities and were able to generate greater forces in response to increased viscous loading than activated sperm (0 h). Transitional sperm (3 h) showed an intermediate response. The paths of hyperactivated sperm through solutions of 20% and 30% Ficoll were considerably straighter than those made through medium alone. This is the first demonstration that hyperactivation can confer a mechanical advantage upon sperm in the oviduct where they may encounter viscous oviductal fluid and a viscoelastic cumulus matrix.

Animals↗
PubMed1991

The use of a urinary estrone conjugates assay for detection of optimal mating time in the cynomolgus macaque (Macaca fascicularis).

Forty-four female cynomolgus macaques (Macaca fascicularis) were examined to determine the optimum fertile period for mating. Daily urinary estrone conjugates (E1C) were measured, beginning on day 7 of the menstrual cycle, until a 1.5-gold E1C rise above the baseline was detected. The females were bred the next morning. Pregnancies were verified in all animals at day 18 postbreeding, and/or on day 25 postbreeding. Serum progesterone levels were used to correlate the relationship between ovulation and the E1C peak. Forty-four of the 57 cycles indicated a urinary E1C peak between days 10-15 of the menstrual cycle; this peak occurred on the day following the initial 1.5-fold to twofold rise in 90% of the cycles. A single 2-hr mating period the day before, the day of, or the day after the E1C peak resulted in conception in 17 of 44 (38.6%) animals.

Animals↗
PubMed1990

Mechanisms of filtration of morphologically abnormal human sperm by cervical mucus.

It is well known that cervical mucus restricts penetration of morphologically abnormal human sperm, both in vitro and in vivo. However, the mechanisms of such restriction are not well understood. Using videomicrography to simultaneously analyze the motions and morphology of individual human sperm, we analyzed differential penetration of normal and abnormal sperm into fresh human cervical mucus. Abnormal sperm swam slower in mucus than the normal sperm, but their flagellar beat parameters were not commensurately different. Multivariate statistical analysis of the relationship between individual sperm velocity and flagellar beat parameters indicated that the heads of the abnormal sperm experienced greater resistance from the mucus than did normal heads. Differential mucus resistance, more than altered motile vigor, appears to be responsible for the restriction of abnormal sperm during migration through mucus.

Cervix Mucus↗
PubMed1989

Factors regulating mammalian sperm migration through the female reproductive tract and oocyte vestments.

Mechanisms of mammalian sperm migration through the female reproductive tract and ovum vestments are described. The perspective is biophysical as well as biochemical and morphological, and the focus is upon the role of sperm motility in these processes. Sperm forward progression is characterized as an interactive process between the the cell and its environment, and the mediation of flagellar bend propagation by the physical properties of its surroundings is described. These properties, together with flagellar beat kinematics, sperm morphology, and surface properties, determine the magnitude of the forces generated by sperm and their consequent rate of progression. Sperm interactions with the cervical mucus, the cumulus oophorus, and the zona pellucida are described. The poorly understood affinity of the sperm surface for the macromolecules of the mucus, cumulus, and zona is stressed, as is the viscoelastic structural mechanical resistance of these biopolymers to sperm motion. The kinematics and consequences of hyperactivated sperm motion are presented, with emphasis on objective characterization of such motion (as a biomarker), along with analysis of the mechanical advantage that such motion may confer on spermatozoa during egg-vestment interaction.

Animals↗
PubMed1989

Movement of cynomolgus and rhesus monkey spermatozoa collected from the lower female reproductive tract.

Postcoital (pc) cervical mucus was collected in 73 menstrual cycles of cynomolgus monkeys and in 43 cycles of rhesus monkeys at 2, 6, 10, 30 hr pc. Videomicrography was used to analyze sperm numbers and movement in the mucus. Both cynomolgus and rhesus monkeys had comparable populations of motile sperm in the mucus at 2 hr pc. However, by 6 hr pc, cervical mucus from cynomolgus monkeys contained twice as many total sperm and motile sperm as mucus from rhesus monkeys (P less than .05). Mean swimming speeds of the free-swimming cervical sperm were similar for the two species at this time. No motile sperm were recovered in mucus from rhesus monkeys at 30 hr pc. In cynomolgus monkeys, however, 14 of the 26 animals examined at 30 hr pc had motile sperm in their mucus. These sperm exhibited lower percent motility, percent free-swimming sperm, and swimming speed than those sperm observed at 6 hr pc. Uterine sperm were collected by transcervical or transuterine aspiration from cynomolgus monkeys. In the transcervical technique, sperm were successfully obtained in four of nine animals examined at 6 hr and in four of five animals at 30 hr pc. The percentage of motile sperm in the uterine fluid was high, 82% +/- 4%, and the swimming speeds (86 +/- 2 microns/sec) were higher than those observed in cervical mucus. Approximately 5-10% of the uterine sperm exhibited swimming motions similar to the hyperactivated motility seen in most mammals. These findings indicate that the sperm cervical mucus interaction in vivo in cynomolgus monkeys has more similarities to the human situation than does the interaction in rhesus monkeys.

Animals↗
PubMed1989

Semen characteristics of Vietnam veterans.

As part of an epidemiologic study of the health status of a randomly selected group of Vietnam veterans, we measured the semen characteristics of 324 Vietnam veterans and compared them with a similar group of 247 veterans who did not serve in Vietnam. The participation rate was 81% in both groups. Measurements of sperm concentration, movement characteristics, and head dimensions were performed, using the Cellsoft computer-assisted semen analysis system. We found that Vietnam veterans had significantly (p less than 0.05) lowered mean sperm concentrations (64.8 x 10(6) sperm/mL for Vietnam veterans vs 79.8 x 10(6) sperm/mL for non-Vietnam veterans), and Vietnam veterans were twice as likely to have sperm concentrations less than or equal to 20 million/mL (odds ratio = 2.7, 95% confidence interval = 1.3-5.7). Vietnam veterans also had a significantly lowered mean proportion of morphologically normal sperm heads (57.9% vs 60.8%), with significantly longer mean major axis length and head circumference. The proportion of motile cells, velocity, linearity, amplitude of lateral head displacement, and beat frequency were not different between the two groups. Despite differences in sperm characteristics, Vietnam and non-Vietnam veterans reported fathering similar numbers of children.

Adult↗
PubMed1989

Human cervical mucus and its interaction with sperm: a fine-structural view.

Cervical mucus is a glycoprotein gel whose biological functions depend upon its macromolecular architecture. Using freeze-substitution fixation techniques, we have used transmission electron microscopy to examine the fine structural aspects of mucus, before and after unidirectional physical shearing, and during its interaction with sperm. The microstructure of mucus that has not been directionally stretched consists of a homogenous pattern of interconnecting electron-dense elements. The thickness of the primary structural elements varies from 0.04 to 0.5 microns, giving the impression that the elements have fibrillar but also ribbon-like properties. This dimension is smaller than the sizes depicted by prior studies using scanning electron microscopy. Within the mucus interior, the interstitial distance between adjacent primary elements ranges from 0.5 to 0.8 microns, and is filled with a fibrous network of secondary structural elements. This interstitial dimension is also significantly smaller than that suggested by prior electron microscopic work. At the exterior borders of the mucus, the interstitial sizes are reduced. After physical stretching by forceps, the mucus microstructure undergoes a radical deformation. In some specimens, the primary structural elements become longitudinally aligned and are less interconnected, with compaction at the exterior mucus borders. In other specimens, the primary structural elements become laterally compressed along the longitudinal axis; within the regions of compression, the intrapore diameter is reduced to less than 0.1 microns. These compressed regions will often exclude spermatozoa. Individual sperm deform the local mucus microstructure. The mucus directly anterior to the sperm head is stretched, and the mucus adjacent to the bending flagellum is compressed on the forward side and stretched on the opposite side.

Cervix Mucus↗
PubMed1989

Computer-aided sperm analysis (CASA): image digitization and processing.

The active undulations of a sperm flagellum are a basic expression of cell vitality. They reflect a number of intracellular processes, and also reveal the interaction between the sperm and its environment. The pattern of sperm-head motion during locomotion is a hydrodynamic consequence of the behavior of the flagellum. Hence, studies of sperm-head motion should provide insights into cellular function and membrane integrity. Because of its importance in fertility, considerable attention is devoted to the analysis of sperm-head motion at both a clinical and basic biological level. Historically, such work has been done by hand. Recently, new, computer-aided sperm analysis (CASA) systems have become available to automate this process. These new systems promise to advance the study of cell behavior because they facilitate the objective collection of large amounts of data at relatively low cost. At present, however, few workers understand the relative strengths and limitations of such systems. There is a tendency to uncritically accept CASA results because they are computer generated. In this article, we describe how CASA systems work, and discuss several technological and methodological problems which can produce spurious results. We argue for the development of optical, machine, and specimen preparation standards which will facilitate inter-laboratory comparisons of CASA data.

Animals↗
PubMed1988

Biophysical properties of the zona pellucida measured by capillary suction: is zona hardening a mechanical phenomenon?

Following fertilization, the zona pellucida, a glycoprotein shell investing mammalian eggs, becomes more resistant to dissolution by various agents. This decreased solubility, termed zona hardening, does not occur in hamsters. Thus, universal roles of zona hardening in the block to polyspermy and in oviductal interaction with embryos have been discounted. Although these roles probably have mechanical components, zona hardening has been assessed only as decreased solubility. In our studies, mouse and hamster ovulated oocytes were compared with 2-cell embryos by capillary suction. Step changes in pipet pressure were measured manometrically while resulting zona deformations were determined videomicrographically. Both mouse and hamster zonae were more "deformable" in oocytes than embryos. These results suggest that mechanical zona hardening may be a universal phenomenon. In addition to zona hardening following fertilization, a "spontaneous" zona hardening phenomenon has been reported for mouse oocytes (not embryos) cultured in vitro. In our system, this spontaneous decrease in zona solubility by protease was not accompanied by a mechanical change. In contrast, hamster oocyte and embryo zonae became slightly more soluble, and considerably more deformable during 4-h culture. Thus, spontaneous zona hardening is not a universal phenomenon, and, while decreased solubility has been called "hardening", it is not always accompanied by a mechanical change.

Animals↗
PubMed1988

Localization of cortical granule constituents before and after exocytosis in the hamster egg.

Electrical activation of the hamster egg was used to study cortical granule constituents before and after exocytosis. The activated hamster eggs underwent cortical granule decondensation just prior to and at the time of exocytosis. Some of the cortical granules of aged, unactivated eggs underwent similar changes. FITC- and gold-conjugated Lens culinaris agglutinin (LCA) bound intensely to the surfaces of activated but not unactivated eggs. This labelling was associated with the microvilli. Permeabilized eggs exhibited discrete cortical labelling before activation, with a subsequent decrease following the cortical reaction. Gold-conjugated LCA specifically bound to cortical granules when incubated with thin sections. FITC-soybean trypsin inhibitor (SBTI) bound in discrete foci in the cortex of unactivated eggs. Following activation, cortical labelling by SBTI decreased. Aprotinin and benzamidine hydrochloride inhibited FITC-SBTI from binding to the egg cortex. Gold-avidin localization of biotin-SBTI in the electron microscope demonstrated that condensed cortical granules did not bind SBTI but decondensed or exocytosing granules did. This suggests that a cortical granule protease is exposed just prior to exocytosis. Activated eggs exhibited dramatic decreases in the number of hamster sperm penetrating the cytoplasm, suggesting that a plasma membrane block to polyspermy is temporally related to cortical granule exocytosis.

Affinity Labels↗
PubMed1988

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 micron 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.

Animals↗
PubMed1988

Structure of the cumulus matrix and zona pellucida in the golden hamster: a new view of sperm interaction with oocyte-associated extracellular matrices.

Hamster oocyte-cumulus complexes (OCC), with and without sperm, were structurally analyzed by light- and electron microscopy using freeze substitution. This method has yielded a clear picture of the extracellular oocyte investments, the cumulus cell matrix and the zona pellucida. The cumulus matrix has an overall homogeneous fibrillar structure which appears to attach to cumulus cells at their filopodial extensions. The matrix also extends into the outer regions of the zona pellucida. The zona pellucida has a distinct porous configuration throughout its entire structure. During gamete interaction experiments, capacitated hamster sperm with ultrastructurally intact acrosomes were found throughout the matrix. Sperm had dramatic effects on the matrix, resulting in compression and stretching. Sperm found on the zona pellucida had initiated or completed the acrosome reaction. During the initial stages of the acrosome reaction, the matrix was in contact with the sperm. At later stages of the acrosome reaction, there was a complete loss of matrix material in regions near the sperm.

Animals↗
PubMed1988

Hamster sperm penetration of the zona pellucida: kinematic analysis and mechanical implications.

There have been few direct observations of penetration of the zona pellucida by spermatozoa, and no detailed description of the kinematics of this process. Such information is important in evaluating the contribution of mechanical thrust by the sperm flagellum to the mechanism of zona penetration by the sperm head. To make such observations, small numbers of hamster spermatozoa were inseminated to cumulus masses slightly compressed (150 micron) between a slide and coverglass. Observations were made with interference contrast optics and videorecorded at 60 fields/sec. A total of 63 penetrating spermatozoa were recorded, of which 21 were penetrating completely cumulus-intact zonae. Direct comparison of penetration angles for cumulus-intact and cumulus-dispersed zonae suggested that the cumulus may be important in reorientation of penetrating spermatozoa, which initially lie flat on the zona surface. The beat shape during zona penetration was more complex than the simple sinusoidal waves used previously in modeling the mechanics of sperm-zona interaction. Motility during zona penetration was bimodal, having high-amplitude, low-frequency lever strokes, alternating with low-amplitude, high-frequency propagated sinusoidal waves. The completely asymmetric lever mode and the oscillatory motions of the curved leading edge of the sperm head within the zona may afford significant mechanical advantages to spermatozoa in forcing their way through that matrix. Initial calculations of the maximum force exerted by the sperm head against the zona material during lever strokes predicted values as high as 2700 mu dyn. This result is two orders of magnitude higher than that previously estimated assuming more simple flagellar motility. Although not conclusive, our observations and analysis support the concept that zona penetration is more efficient when the cumulus is present, and that this may be due, in part, to a mechanical advantage conferred upon the sperm by the cumulus material.

Animals↗
PubMed1988

Mechanics of sperm-egg interaction at the zona pellucida.

Mammalian sperm traverse several layers of egg vestments before fertilization can occur. The innermost vestment, the zona pellucida, is a glycoprotein shell, which captures and tethers the sperm before they penetrate it. We report here direct measurements of the force required to tether a motile human sperm as well as independent calculations of this force using flagellar beat parameters observed for sperm of several species on their homologous zonae. We have compared these sperm-generated forces with the calculated tensile strength of sperm-zona bonds, and found that a motile sperm can be tethered, at least temporarily, by a single bond. Therefore, sperm can be captured by the first bond formed and tethered permanently by a few. The sperm cannot subsequently penetrate the zona unless the bonds are first eliminated. However, premature elimination would simply allow the sperm to escape. Therefore, not only must the bonds be eliminated, but the timing of this must be regulated so that the sperm is already oriented toward the egg and beginning to penetrate as the bonds are broken.

Animals↗
PubMed1988

Early indicators of male reproductive toxicity.

Longitudinal data were analyzed for seminal characteristics of rhesus monkeys and beagles. The monkeys were exposed to DBCP; the beagles were exposed to acute or chronic whole body gamma irradiation. The semen was analyzed for volume and sperm concentration. Sperm were measured for percent motility, swimming speed, and head dimensions. Abnormalities of the sperm tail were also noted. All treatments resulted in measurable effects on the semen parameters. Sperm production, as evaluated by seminal sperm concentration or total sperm numbers in the ejaculate, was as informative of testicular toxicity as any other parameter or combination of parameters. A consistent finding was that changes in sperm output occurred concomitantly with changes in sperm motility.

Animals↗