Allurin, a 21-kDa sperm chemoattractant from Xenopus egg jelly, is related to mammalian sperm-binding proteins.

Previously, we demonstrated that a protein from Xenopus egg jelly exhibits sperm chemoattractant activity when assayed by either video microscopy or by sperm passage across a porous filter. Here we describe the isolation and purification of allurin, the protein responsible for this activity. Freshly oviposited jellied eggs were soaked in buffer, and the conditioned medium was loaded onto an anion exchange column and eluted with an NaCl gradient. The active fraction was purified further by RP-HPLC, the chemoattractant protein appearing as a single sharp peak. The amino acid sequence of the protein, determined by direct sequencing and cloning of cDNAs coding for the protein, consisted of 184 amino acids having a molecular mass of 21,073 Da. The protein shares homology with the mammalian cysteine-rich secretory protein (CRISP) family that includes testes-specific spermatocyte protein 1, a cell adhesion protein which links spermatocytes to Seritoli cells, and acidic epididymal glycoproteins that bind to sperm and have been implicated in sperm-egg fusion. Phylogenetic analysis suggests that allurin evolved from the ancestral protein that gave rise to the mammalian CRISP family. Addition of allurin to this family portends that the CRISP family represents a group of "sperm escort" proteins, which bind to sperm at various steps in their life history, facilitating passage from one functional stage to the next. Allurin stands out in this regard, representing both the first vertebrate sperm chemoattractant to be purified and sequenced and the first member of the CRISP family to be found in the female reproductive tract.

Xenopus laevis egg jelly contains small proteins that are essential to fertilization.

The eggs of Xenopus laevis are surrounded by investment layers of egg jelly that interact with the sperm immediately prior to fertilization. Components of these egg jelly layers are necessary for the fertilization of the egg by incoming sperm. Eggs which are stripped of their jelly layers are refractile to fertilization by sperm, but the addition of solubilized jelly promotes fertilization. We have shown previously that the egg jelly layers are composed of a fibrous network of glycoconjugates which loosely hold smaller diffusible components. Extracts of these diffusible components were prepared by incubation of freshly ovulated eggs in high-salt buffers for 12 h at 4 degrees C. This diffusible component extract, when incubated with sperm, promoted the sperm's ability to fertilize dejellied eggs in a dose-dependent manner. In contrast, the high-molecular-weight "structural" glycoconjugates of jelly that remain after extraction of the diffusible components did not increase fertilization efficiency of dejellied eggs nor did nonspecific proteins, carbohydrate polymers, or organic polymers. The diffusible components, analyzed by SDS-PAGE, consisted of a mixture of proteins from 4 to 180 kDa. The protein responsible for fertilization rescue appeared to be <50 kDa and appeared to self-aggregate or to bind to larger proteins. This protein component was required during sperm binding to the egg, its action required an intact egg vitelline envelope, and its action was independent of large soluble polymers such as Ficoll.

The relationship of sperm counts to birth rates: a population based study.

PURPOSE: We determined if a statistical relationship exists between changes in sperm counts and birth rates by comparing data from a single geographic location for a 24-year period. MATERIALS AND METHODS: We retrospectively analyzed data from 660 men who banked 1,972 semen samples before vasectomy in Minnesota from 1971 to 1994. Using general linear models, annual variations in sperm count were determined after adjusting for age, duration of abstinence and seasonal (monthly) effects. Adjusted annual mean sperm count was then correlated with regional birth rate data obtained from The National Center for Health Statistics. RESULTS: Multiple regression analysis revealed a significant linear increase in mean annual sperm count at an estimated rate of 1.03 x 10(6) sperm per ml. per year (b = 0.14, t = 5.641, p < 0.0001). There was no effect of age (t = -0.814, p = 0.4156) but there were significant effects of abstinence (b = 0.14, t = 8.808, p < 0.0001) and month of sperm banking (b = 0.025, t = 5.00, p < 0.0001) on sperm counts. Using analysis of covariance there was a significant, nonlinear (year-to-year) fluctuation in mean sperm counts (F = 8.63, p < 0.001). For the study period mean birth rates in Minnesota (live births per 1,000 population) fluctuated yearly from 13.8 in 1973 to 16.7 in 1981. There was a strong correlation between adjusted mean yearly sperm count and annual birth rates (r = 0.63, p = 0.001). CONCLUSIONS: We found a statistically significant correlation between yearly variations in mean sperm counts and birth rates. Our data suggest that variations in male reproductive function may affect population based birth rates and, therefore, may be more important than previously understood.

Semen analyses in 1,283 men from the United States over a 25-year period: no decline in quality.

OBJECTIVE: To determine whether semen quality has changed in the United States over the last 25 years. DESIGN: Retrospective review. SETTING: Three U.S. sperm banks, Cryogenic Laboratories, Inc. (Roseville, Minnesota), Idant Laboratories (New York, New York), and California Cryobank, Inc. (Los Angeles, California). INTERVENTION: None. MAIN OUTCOME MEASURES: Age at sample collection, sperm concentration, volume, motility, and days of abstinence before sample collection were determined for each man. Linear and multiple regression analyses were used to assess changes in these characteristics over time. RESULTS: Controlling for the effects of age and duration of abstinence, there was a slight but significant increase in mean sperm concentration but no change in either motility or semen volume over the 25-year period. Both sperm motility and semen volume decreased with increasing age at sample collection. Both sperm concentration and semen volume increased as a function of duration of abstinence. There were significant differences in mean (+/- SEM) sperm concentrations (10(6) sperm/mL) and motilities between the different sperm banks with California lowest (72.7 +/- 3.1, 51.4% +/- 1.1%, respectively), Minnesota higher (100.8 +/- 2.9, 56.0%, respectively), and New York highest (131.5 +/- 3.5, 58.2% +/- 0.5%, respectively). CONCLUSIONS: Our data show no decline in sperm counts over a 25-year period in 1,283 men who banked sperm before vasectomy at three distinct geographical sites in the United States.

Semen cryobanking for men with cancer--criteria change.

OBJECTIVE: To summarize pregnancies and births after the use of pretherapy cryobanked semen from men with cancer and to reassess the clinical role of semen cryobanking for these patients. DESIGN: Survey of pregnancies and births that have occurred after the use of cryobanked semen from pretherapy cancer patients. SETTING: Survey of the literature and of nine semen banks. PATIENTS: Men with testicular cancer, Hodgkin's diseases, non-Hodgkin's lymphoma, and other types of cancer who cryobanked their semen specimens before therapy. OUTCOME MEASURES: Pregnancies and births resulting from the use of cryobanked semen after artificial insemination by husband (AIH) or other assisted reproductive technology (ART) procedures. RESULTS: The use of AIH and other ART procedures have resulted in 117 documented pregnancies and 115 livebirths. CONCLUSIONS: Cryobanking of semen should be offered to all men diagnosed with cancer because such a procedure provides the only reasonable chance of establishing a pregnancy after therapy that is detrimental to fertility potential. Existing criteria for pretherapy semen cryobanking, therefore, should be revised in view of successful pregnancies even with the use of semen with low spermatozoal densities and motilities, as well as other realized clinical efficacies of ART. Conceptions have occurred after in vitro fertilization (IVF) with < 1 x 10(6) motile spermatozoa. Semen cryobanking should be offered by the attending physician as a viable option for any pretherapy male patient who has any motile sperm and considers the future possibility of having children.