Discrepancies in analyses of deoxyribonucleic acid in rabbit spermatozoa, involving Feulgen staining (Feulgen-DNA) and ultraviolet light absorption (UV-DNA) measurements

Embryos generated using testicular spermatozoa have higher developmental potential than those obtained using epididymal spermatozoa in men with obstructive azoospermia

OBJECTIVE

To determine whether the injection of testicular spermatozoa results in more viable embryos (higher implantation rate) than injection of epididymal spermatozoa in cases of obstructive azoospermia.

DESIGN

Retrospective analysis of 265 cases of testicular sperm aspiration (TESA) and percutaneous sperm aspiration (PESA), including 185 cases of obstructive azoospermia.

SETTING

Private Infertility clinic.

PATIENT(S)

None, charts review.

INTERVENTION(S)

None, charts review.

MAIN OUTCOME MEASURE(S)

Clinical pregnancy rate (PR), implantation rate.

RESULT(S)

Although fertilization rates were higher in the PESA group, implantation rates were significantly better in the TESA group. There was also a trend to higher ongoing PR and lower miscarriage rates in TESA cases.

CONCLUSION(S)

In cases of obstructive azoospermia, embryos generated using testicular spermatozoa have higher developmental potential than those obtained using epididymal spermatozoa.

Suppression of endogenous estrogen during development affects porcine epididymal sperm maturation

Estrogen plays an important role in male reproduction, critical for sustained fertility in some species. Reducing estrogen's interaction with its receptor(s) in monkey and mouse models is associated with reduced sperm motility and, in some cases, documented elimination of sperm fertilizing ability, suggesting that normal epididymal function may be estrogen dependent. The objective of these experiments was to evaluate the effects of reduced endogenous estrogen on development of epididymal function in the pig, a species in which males have very high levels of endogenous estrogen. Letrozole, a potent inhibitor of estrogen synthesis, was administered to neonatal boars from 1 week of age and markedly suppressed estrogen production. Epididymal function assessed as acquisition of sperm fertilizing ability (in vitro fertilization of zona-free oocytes) was reduced in Letrozole-treated animals at 24 and 28 weeks of age (23% and 30% fertilization, respectively compared with 37% and 54% in vehicle controls) but had recovered by 32 weeks of age. Cauda epididymal sperm numbers were reduced in treated animals (35% of control values at 20 weeks of age) but appeared to be recovering at 32 weeks of age. Reduction of endogenous estrogen had no effect on other aspects of epididymal function (percentage of motile sperm, sperm motion parameters, sperm head morphometrics, or ability of sperm to undergo an acrosome reaction). Reducing endogenous estrogen during postnatal development appears to have transient effects on porcine epididymal function. These transient effects suggest that the pig, with its high endogenous estrogen, may respond differently than other species to reduced estrogen synthesis.

Metachromatic staining of human sperm nuclei after reduction of disulphide bonds

Intra- and interprotamine cross-linking by disulphide bonds are the main factors responsible for the highly compact and stable structure of chromatin in mammalian spermatozoa. Unfixed or methanol fixed smears of human sperm and sperm suspensions from fertile donors and oligospermic patients were subjected to a reductive cleavage of disulphide bonds by using 2-mercaptoethanol (ME) or dithiothreitol (DTT). Untreated (control) and ME or DTT treated samples were stained with toluidine blue (TB) and examined in light microscopy; spectral characteristics of TB stained sperm nuclei were also analyzed. Untreated smears from fertile donors showed an orthochromatic (pale blue) staining of most sperm heads, while a variable proportion of metachromatic nuclei was found in spermatozoa from patients with oligospermia. After treatment with DTT followed by TB staining, fixed and unfixed smears showed metachromatic sperm heads. ME treatment only induced a scarce colour shift, whereas a striking metachromatic reaction and variable nuclear swelling were observed in DTT treated sperm suspensions. These results indicate that after cleavage of disulphide bonds, phosphate groups from chromatin DNA are unmasked and available for TB binding and metachromatic staining.

The effect of cervical mucus on measurable Feulgen DNA content of human spermatozoa

The DNA content of morphologically normal Feulgen-stained human spermatozoa (SP) without and with vacuoles was determined by visible light absorption at 560 nm. In an experimental device designed according to the sperm penetration meter of Kremer, sperm penetration into cervical mucus (CM) was allowed to take place for a 60-min period. Smears of the native and mucus-penetrated spermatozoa were applied to glass slides and fixed in a mixture of methanol, formalin, and acetic acid for 1 h. Hydrolysis was performed in 1 N HCl. The slides were stained using hematoxylin. Bull spermatozoa stored at -96 degrees C were applied as an internal standard to ach slide. Of a total of 1,464 spermatozoa measured, 485 came from the ejaculate, 491 had travelled through the cervical mucus for a distance of 15-30 mm, and 193 had migrated for 31-45 mm. The remaining 295 bull spermatozoa were also measured. It was found that after cervical mucus passage the content of Feulgen DNA material measured changed in two different ways: in some of the samples the Feulgen DNA content increased with passage through the cervical mucus, whereas in other samples the Feulgen DNA content decreased during cervical mucus passage. As in the ejaculate, we found a marked variation of the DNA content of spermatozoa after CM passage. The filtering effect of the CM on pathologic SP was not complete.

Nuclear decondensation of mammalian spermatozoa: changes during maturation and in vitro storage

Swelling of the spermatozoan nucleus and decondensation of the chromatim occur soon after penetration of spermatozoa into the egg cytoplasm. This decondensation was duplicated in vitro by incubating pre-ejaculatory ram, rabbit and bovine spermatozoa and also stored post-ejaculatory bovine spermatozoa in 1% sodium dodecyl sulfate and 2.0 mM dithiothreitol. Spermatozoa obtained from the testis and epididymal caput, corpus and cauda showed a progressive resistance to nuclear decondensation, while no change was evident in the decondensation time of spermatozoa obtained from the epididymal cauda, vas deferens and ejaculated semen. There was also a significant increase in decondensation time after the spermatozoa had been stored in vitro at 25 degrees C. This increased resistance to nuclear decondensation in the in vitro stored spermatozoa, reflecting an increase in cross-linking within the spermatozoan histones by formation of disulfide bonds, may account for part of the increased embryonic mortality observed when spermatozoa are stored in vitro prior to insemination.

The spermatozoan genome and fertility

The strategy for effective reproduction by eliminating genetically unbalanced gametes during spermatogenesis and transport varies in degree of success within as well as among species, but in no animal has it been reported to be completely effective. In the human subject, for example, it is estimated that one in every 50 ejaculated spermatozoa is genetically abnormal. The causal basis of these anomalies is poorly understood. Meiotic accidents, environmental mutagens, and gamete senescence in utero are all implicated. However, many of these abnormal cells are fertile. This fact plus the weight of the evidence reviewed suggest that fertility differences among males which cannot be ascribed to measurable differences in semen characteristics reflect, in large part, the increased opportunity of nuclear defective gametes in the semen of some males to effect fertilization. The elimination of embryos arising from eggs fertilized by genetically defective spermatozoa through spontaneous abortions, although biologically costly, must be viewed as the final check for the elimination of genetic detritus of the species.

[Morphological studies on abnormal human spermatids and spermatozoa (author's transl)]

Malformed spermatids and spermatozoa in the testes, epididymes, and ejaculates of 29 apparently healthy men and in 171 patients suffering from different andrological diseases were investigated with the electron microscope. The following types of malformations are described: 1) Malformations of the acrosome in contact with the nucleus of the spermatid: Vesicular inclusions in the acrosome vesicle, asymmetric thickenings of the acrosome cap, enfolding of the acrosomal lamina into the spermatid's nucleus, partial separation of the acrosome from the nucleus, apical knob-like thickenings of the acrosome. 2) Malformations of the acrosome independent from the spermatid's nucleus: the acrosomal material is contained in small vesicles, large vacuoles, in ring-like structures, in globular or shell-like laminar structures. The nucleus of such spermatids lacks an acrosome. 3) Malformations of the nucleus: inclusions of vesicles or membranes, excessive packages of membranes, gigantic nuclear vacuoles, lack of condensation of the caryoplasm. 4) Multinucleate spermatids: two or more nuclei within the pericaryon of one spermatid are joined by an acrosome. 5) Duplicate acrosome anlagen. 6) Malformations of the tail: disorganization of the axonema, a lack or excessive numbers of tubules and fibres, doublets of the axial filaments, destruction of the neck region, a lack of the mitochondrial sheath, and enlargement of the fibrous sheath. Malformed germ cells were observed to occur in varying amounts both in apparently healthy men and in those who were apparently infertile. This indicates that germ cell malformations are no absolute indicator of male infertility. However, certain distinct types of malformations (such as round-headed spermatozoa) are definitely associated with infertility, but only if all spermatozoa in the ejaculate of a patient have the same defect.