Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “EPIDIDYMITIS”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,387 records · Page 77Linked to original sources
PubMed1982

Origin of adenomatoid tumor: a comparison between the structure of adenomatoid tumor and epididymal duct cells.

In this study the structure of the adenomatoid tumor was compared with that of the epididymal duct cells. Several similar histochemical and ultrastructural features such as PAS-positive cytoplasmic granules, microvilli, intracellular vacuoles, and extracellular canaliculi were found. Based on these findings, it is suggested that the adenomatoid tumor is derived from the coelomic epithelium after it has begun to differentiate in the direction of genital epithelia. Because mesothelial cells are also derived from coelomic epithelial cells, the similarities between adenomatoid tumor and mesothelial cells may also be explained.

Adenoma↗
PubMed2000

Time course of transforming growth factor-beta(1) (TGF-beta(1)) mRNA expression in the host reaction to alginate-poly-L-lysine microcapsules following implantations into rat epididymal fat pads.

Microencapsulation of islets of Langerhans within semipermeable membranes has been proposed to prevent their immune destruction after transplantation. However, the successful application of this method is impaired by a pericapsular reaction, which eventually induces graft failure. Our goal is to study the role of cytokines in the pathogenesis of this reaction, using the model of alginate-poly-L-lysine microcapsule implantation into Wistar rat epididymal fat pads (EFP). The specific objective of this study was to determine the time course of transforming growth factor (TGF)-beta(1) mRNA expression by semi-quantitative reverse transcriptase-polymerase chain reaction. Microcapsules induced an increase of TGF-beta(1) mRNA expression that reached a maximum 14 days after implantation. Seven, 14, 30, and 60 days after microcapsule implantation, the expression of TGF-beta(1) mRNA was significantly higher in pericapsular infiltrate cells than in nonimplanted EFP cells (p<0.05, p<0.0001, p<0.005, and p<0.01, respectively). Injection of physiological saline induced a small and gradual augmentation of TGF-beta(1) mRNA expression with a maximum 30 days after injection (p<0.01 vs. nonimplanted EFP cells). These results demonstrated that microcapsule implantation, in comparison with saline injection, induce an early, extended, and amplified TGF-beta(1) mRNA expression. This suggests that TGF-beta(1) plays a role in the pathogenesis of the pericapsular host reaction.

Alginates↗
PubMed2001

Induction of the acrosome reaction in dog sperm cells is dependent on epididymal maturation: the generation of a functional progesterone receptor is involved.

In the current study we investigated the progesterone receptor exposure on the sperm from the testis and different parts of the epididymis, the relation to the sperm maturation stage, the functionality of the progesterone receptor and the capacity of sperm to undergo acrosome reaction. Exposed progesterone receptors on spermatozoa were detected using Progesterone-BSA conjugate labeled with fluorescein isothiocyanate (P-BSA-FITC) or a monoclonal antibody against progesterone receptor, C-262. Either progesterone or calcium ionophore was used to induce acrosome reaction. A high percentage (69 +/- 8%; mean +/- SD) of spermatozoa from the cauda epididymis showed P-BSA-FITC labeling at the onset of incubation, whereas only 0.1 +/- 1 and 4 +/- 2%, of spermatozoa from the testes, caput, and corpus epididymis, respectively, were labeled. There was no significant increase in P-BSA-FITC binding during the course of a 6 hr incubation. Treatment with either 10 microM progesterone or 5 microM calcium ionophore induced acrosome reaction in cauda epididymal sperm but not in testicular sperm, caput or corpus epipidymal sperm. It is concluded that the matured sperm of the dog from cauda epididymis and freshly ejaculated sperm demonstrate a functional membrane-bound progesterone receptor while less matured spermatozoa from the testicle, caput, and corpus epididymis fail to demonstrate such a receptor. Acrosome reaction of dog sperm can be induced using either progesterone or calcium ionophore; however, the maturation stages of spermatozoa influence this occurrence.

Acrosome Reaction↗
PubMed1982

Studies on prolonged spermatozoa survival in Chiroptera: a morphological examination of storage and clearance of intrauterine and cauda epididymal spermatozoa in the bats Myotis lucifugus and M. velifer.

The cauda epididymidis, uterine corpus, and cornua and uterotubal junction of Myotis function to retain and preserve normal spermatozoa throughout hibernation. In none of the sites do spermatozoa show features that might account for their extended viability. Spermatozoa stored in the uterus and epididymis show no special orientation toward the epithelium lining these sites, whereas an intimate relationship is established between some sperm and the epithelial cells of the uterotubal junction which might either account for extended postcoital sperm survival or forecast their removal from further participation. Transmission and scanning electron microscopic observations do not disclose any morphological changes in stored luminal spermatozoa. A low rate of phagocytosis of sperm is evident in the female tract during hibernation. However, spermatozoa are evidently not vulnerable to being removed from the storage sites until spring arousal when ovulation occurs. Both uterotubal epithelial cells and phagocytes appear to be involved in the disposal of spermatozoa in the female, whereas epididymal spermatozoa apparently are primarily voided during urination. A mechanism that delays capacitation must underlie the ability of spermatozoa to survive in the female reproductive tract of the hibernating bat.

Animals↗
PubMed1987

Plasma membrane structure of bat spermatozoa: observations on epididymal and uterine spermatozoa in Myotis lucifugus.

Plasma membrane structure of bat spermatozoa was examined utilizing electron microscopy of thin sections and freeze-fracture replicas. Notable membrane features observed in replicas from cauda epididymal spermatozoa included specialized particle aggregates at the junction between the acrosomal and postacrosomal region of the head (a membrane structure not previously described in mammalian spermatozoa) and another row of rod-like particles just anterior to the posterior ring. Both of these specializations in fractured plasma membranes correspond with regions where the membrane is closely apposed to underlying structures when viewed in thin sections. The postacrosomal sheath appears to be composed of an array of longitudinally oriented filamentous components. Characteristic ordering of intramembranous particles was also noted in replicas from the midpiece region and the annulus. Major changes in plasma membrane structure were not seen in spermatozoa stored in the female reproductive tract; however, the appearance of linear particle aggregations in the principal piece membrane was noted. No evidence was obtained to suggest that an acrosome reaction had occurred in spermatozoa stored in females.

Animals↗
PubMed1981

Changes in intramembranous particle distribution epididymal spermatozoa of the boar.

Membranes of boar spermatozoa from different regions of the epididymis and after ejaculation were studied by the freeze-fracture replica technique. The ordered pattern of the intramembranous particles of spermatozoan plasma membranes was different in the five arbitrary zones of the epididymis and in the semen. A distinctive ordered pattern was absent in zone 1, which is the proximal segment of the epididymis. In zone 2, paired parallel rows of the particles were present in the plasma membrane over the acrosomal region. This parallel arrangement was not present in zone 3 spermatozoa. Anterior to the posterior ring, cords formed by packed particles were apparent in zone 2 spermatozoa and reached their maximum prominence in zone 3, and persisted in zones 4 and 5 and in the semen. The plasma membrane over the marginal ridge of the acrosome had a hexagonal array of particles only in zones 4 and 5 spermatozoa. A similar pattern appeared on the post-acrosomal region of spermatozoa in zone 5 and in the semen. The plasma membrane of the middle piece had a rectilinear arrangement of the particles in zone 2 spermatozoa in which the migration of the cytoplasmic droplet was complete. Rudiments of the rectilinear arrangement persisted in spermatozoa in zones 4 and 5 and in the semen. These changes are discussed in relation to sperm maturation in the epididymis. The acrosomal membrane had a hexagonal arrangement of particles in the equatorial segment. The marginal ridge of the outer acrosomal membrane had parallel rows of intramembranous particles. The organization of the acrosomal membrane particles did not change during the epididymal passage of boar spermatozoa.

Acrosome↗
PubMed1994

Immunocytochemical detection of actin and 53 kDa polypeptide in the epididymal spermatozoa of rat and mouse.

BACKGROUND: Presence of immunocytochemically detectable actin in the rat and mouse sperm head has been enigmatic for years. In this study, we demonstrate actin in the perinuclear theca and show that the detection of actin epitopes in the rat and mouse epididymal spermatozoa can effectively be enhanced by pre-extraction of sperm cells with SDS. METHODS: The study with one monoclonal and one polyclonal anti-actin antibody was carried out at conventional and confocal fluorescence and electron microscope level, and by immunoblotting of proteins isolated from the head and tail fractions. RESULTS: In the head of the control methanol-acetone fixed rat spermatozoa, the polyclonal antibody gave a stronger immunostaining in the postacrosomal area and in the perforatorium than the monoclonal antibody. In the mouse sperm head, the monoclonal antibody labeled the ventral edge of the postacrosomal area and slightly the perforatorium, whereas the polyclonal antibody stained the entire perinuclear space. In the SDS-extracted spermatozoa, an intense postacrosomal and perforatorial labeling was obtained with both antibodies but, in particular in the rat spermatozoa, the middle lateral portion of the postacrosomal segment remained unlabeled. Sonication seemed to cause structural modifications which specifically impeded staining with the monoclonal antibody. Both antibodies detected actin in the basal plate and the monoclonal antibody in the neck. Amorphous matrix of the connecting piece showed immunogold labeling. In the tail, the monoclonal antibody recognized actin and a relatively basic 53 kDa polypeptide, whereas the polyclonal antibody reacted with several protein bands. SDS-soluble actin of the tail was addressed to the midpiece and the SDS-insoluble 53 kDa protein profoundly to the outer dense fibers of the principal piece. CONCLUSIONS: Intense labeling of actin in the SDS-extracted rat and mouse spermatozoa was presumably due to the generated demasking of actin epitopes embedded in the perinuclear cytoplasm. The results are important in confirming that actin in the rat and mouse sperm head is not lost during spermiogenesis but apparently contributes to the three-dimensional packing of the mature perinuclear cytoplasm. This study further demonstrates the importance of the methods used in sample preparation and advantages of confocal microscopy when attempting to detect cytoskeletal proteins which, as in spermatozoa, may occur in small quantities.

Actins↗
PubMed1987

Regulation of activation state and flagellar wave form in epididymal rat sperm: evidence for the involvement of both Ca2+ and cAMP.

Rat sperm from the cauda epididymis exhibit increased motility, longevity, and a distinct circular pattern of flagellar curvature in response to 5 mM procaine-HCl or 0.1 mM 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate (TMB-8), reagents that are thought to play a role in the immobilization of free cellular calcium. Triton X-100-extracted sperm models will exhibit the same pattern of motility and curvature as procaine- or TMB-8-activated cells, but only when calcium is removed by a strong chelating agent, and in the presence of cAMP (3 microM). Demembranated sperm models produced from epididymal rat sperm are quiescent unless cAMP is added. In these sperm models, the presence or absence of free calcium mediates a transition in flagellar curvature. The increased activity of the procaine-treated intact cells was not accompanied by a change in cellular ATP content, nor was ATP availability the limiting factor in the quiescent sperm. Therefore, the increased motility produced by procaine is probably mediated by a fall in free intracellular Ca2+ accompanied by a rise in cAMP. Our finding that calcium controls the curvature of sperm flagella may explain altered patterns of flagellar beating, such as the hyperactivated motility that sperm exhibit in the female reproductive tract.

Adenosine Triphosphate↗
PubMed2001

Prolonged survival of mouse epididymal spermatozoa stored at room temperature.

The viability and fertility of isolated mouse epididymal spermatozoa kept for up to 7 days at various temperatures (4 degrees C, 22 degrees C, and 37 degrees C) were determined. Spermatozoa kept for 3 days at 22 degrees C were still active, while those kept at 37 degrees C or 4 degrees C exhibited great reduction in motility within 2 days after isolation. In vitro fertilizing abilities of spermatozoa left for 0, 1, 2, and 3 days at 22 degrees C were 69.2, 32.5, 9.5, and 4.9%, respectively, when the cleavage rate to two-cell stage was examined. Transfer of two-cell embryos produced in vitro with spermatozoa left for 1, 2, and 3 days at 22 degrees C resulted in production of fetuses with efficiencies of respectively 30.2, 11.5, and 16.7%, which were lower (63.3%) than that of embryos derived from in vitro fertilization with fresh spermatozoa. These findings indicate that spermatozoa kept for up to 3 days at 22 degrees C can fertilize oocytes, although at relatively low efficiency.

Animals↗
PubMedDate not supplied

Synthesis and secretion of glycoprotein by the epididymal epithelium.

The secretory activity of the middle segment of the mouse caput epididymidis was studied using 3H-fucose as a precursor to glycoprotein. Young adult male mice were injected with a concentrated solution of 3H-fucose interstitially, ie beneath the connective tissue capsule of the epididymis. Two animals were killed and prepared for light microscopic radioautography at each of six intervals between 10 minutes and 24 hours after injection. Silver grains were concentrated over the supranuclear Golgi region at 10 minutes and over the apical ends of the cells 30 minutes and 1 hour after injection. Quantitative analysis showed that luminal radioactivity increased greatly beginning with the 2-hour samples. The results indicate that the epididymal epithelium synthesizes and secretes glycoproteins, and that 1 to 2 hours are required for terminal glycosylation, intracellular transport, and release of the secretory product.

Animals↗
PubMedDate not supplied

Rat cauda epididymal fluid is a mucus.

Immobilin, the highly viscoelastic glycoprotein isolated from rat cauda epididymal fluid, exhibits all of the key biochemical characteristics of a mucin: 1) it has a very high molecular weight (will not pass through a 10(6) dalton cut-off filter; 2) it contains 56% carbohydrate, with low or undetectable levels of mannose, xylose and uronic acid; 3) the carbohydrates (primarily galactose, N-acetylglucosamine and N-acetylgalactosamine) are arranged in short, oligosaccharide chains (4-20 monosaccharides per chain); 4) these oligosaccharide chains can be cleaved by NaOH in the presence of NaBH4, suggesting O-glycosidic linkages; and 5) the protein core is pronase-resistant. Immobilin, however, contains no detectable sialic acid, and 67% of the oligosaccharides are uncharged, indicating that immobilin is less acidic than most other mucins.

Animals↗
PubMedDate not supplied

Isolation and characterization of the plasma membrane of rat cauda epididymal spermatozoa.

Cauda epididymal rat spermatozoa were isolated by flushing the excised epididymis and the plasma membrane was detached by a nitrogen cavitation treatment (500 psi, 10 minutes equilibration at 4 C). Membrane vesicles were recovered after sucrose gradient centrifugation. Portions of the sperm surface releasing the plasma membrane were assessed by light microscopy of fluoroscein isothiocyanate-succinylated concanavalin A-treated spermatozoa and by transmission electron microscopy. Plasma membrane was detached from the region overlying the acrosome from most spermatozoa and from the middle-piece overlying the mitochondria from some cells. Thus, the fraction analyzed was derived from at least two portions of the sperm surface. The fractions from the sucrose density gradient were analyzed for gross chemical composition (phospholipid, protein and sterol) and the protein components were detected after electrophoresis under denaturing conditions; the peak fractions (at density approximately 1.13 g/ml) were judged homogeneous. Replicate analyses of such preparations established mass ratios of protein to phospholipid of 0.63, total sterol to phospholipid of 0.18, and demosterol to cholesterol of 0.32. The molecular composition of the phospholipid fraction was determined to be 10% phosphatidylserine (mole percent), 3% phosphatidylinosital, 3% sphingomyelin, 31% phosphatidylethanolamine, 27% phosphatidylcholine, 10% diphosphatidylglycerol and 5% of an unknown component. Fatty acyl analyses of the phospholipid fraction revealed that approximately 70% of the residues consisted of palmitoyl (16:0) and stearoyl (18:0) acyl groups, with the balance distributed among various unsaturated acyl groups (18:1, 22:3, 22:4 and 22:5); about 40% of the recovered phospholipids represented ether acyl phosphatides. Differences in the lipid composition of rat vesicles described here and similar vesicles isolated from ram and boar spermatozoa (described previously) are discussed. The partitioning of the nitroxyl spin label 3-doxylheptane into vesicles isolated from rat and ram spermatozoa was assessed by electron paramagnetic resonance spectroscopy at temperatures between 4 C and 26 C; no difference in the response of the spin label in the two vesicle preparations was detected.

Animals↗
PubMedDate not supplied

Relationship between the characteristics of epididymal red deer spermatozoa and penetrability into zona-free hamster ova.

A heterologous (zona-free hamster oocytes) in vitro fertilization (IVF) system was used to evaluate the relationship between sperm factors and penetration capacity of epididymal red deer spermatozoa. The sperm parameters evaluated in 36 sperm samples obtained postmortem from stags selectively shot during the rutting season were sperm motility, functional integrity of plasma membrane by means of the hypo-osmotic swelling test (HOST), and, simultaneously, viability and acrosomal status via a triple-stain technique. Zona-free hamster oocytes were used to evaluate the capacity of the different sperm assays to predict in vitro penetration. In order to increase the variability in sperm quality, we recovered samples from stags at different intervals between the death of the male and the collection of the genitalia. All measures of sperm quality declined progressively (P <.001) with increasing intervals between death and sample collection. In addition, many sperm parameters were related to penetration ability in vitro. Subsequently, sperm samples were rearranged in 2 categories according to the interval that had elapsed between death and the collection of the genitalia (group 1, short interval = 0-12 h; group 2, large interval = 18-40 hours). When samples were grouped, less correlation achieved significance, especially for group 1, than when samples were not divided. Also, correlation between the number of sperm per oocyte and sperm parameters for group 1, which had the highest values of sperm quality, failed to reach significance. It is concluded that the classical parameters accepted in assessing the viability of deer spermatozoa can be good predictors of the penetrating ability of the spermatozoa when satisfactory in vitro conditions are used for the development of the IVF system. Also, this study demonstrates that compatible heterologous gamete interaction allows thorough assessment of sperm function in a wild deer.

Animals↗
PubMedDate not supplied

Progesterone receptor availability in mouse spermatozoa during epididymal transit and capacitation: ligand blot detection of progesterone-binding protein.

The goals of the present study were to determine the availability of progesterone (P4) receptor (P4r) in mouse sperm during maturation and capacitation and to make the first steps toward a characterization of P4r. It has been proposed that P4 is able to induce an acrosomal reaction (AR) by using a membrane P4r. This induction was verified in sperm isolated from the cauda epididymis (fully mature) when incubated in specific conditions that capacitate sperm. First, we set up the conditions in our laboratory to induce an AR in mature and capacitated sperm triggered by P4 that was detected by a chlortetracycline (CTC) assay. Then, we examined sperm isolated from the caput epididymis (immature) incubated under conditions that support cauda sperm capacitation and found that the AR could not be detected. Moreover, P4 was unable to induce the AR when it was applied to sperm isolated from either region and incubated under conditions that did not support capacitation. These results can be explained by changes in P4r availability. A suitable marker for P4r is the gold (Au)-P4 complex. This marker shows a binding capacity that can be visualized directly by electron microscopy (EM) and indirectly by silver-enhanced methods with light microscopy. The Au-P4 complex was localized in capacitated cauda sperm at the dorsal edge of the head. Using these techniques, we observed a significant decrease in both noncapacitated cauda sperm and caput sperm (whether incubated in capacitating media or not). Genomic P4r could be responsible for the signal detected, but antibodies against the P4 nuclear receptor did not recognize any sites in the sperm by immunostaining methodology. Instead, a 44-kd protein band was detected in the sperm by a ligand blot assay. In conclusion, P4 promotes the AR in capacitated cauda sperm but is unable to do so in noncapacitated or immature sperm because the availability of P4r increases during epididymal transit and after capacitation. The P4r responsible for this behavior is different from a classical nuclear receptor-on the basis of the immunostaining results-and is probably a protein close to 44 kd-on the basis of the ligand assay results.

Acrosome Reaction↗
PubMed1995

The rat epididymal fat pad as an implantation site for the study of microcapsule biocompatibility: validation of the method.

The study of microcapsule biocompatibility is hindered by their uneven distribution and low recovery when implanted into the peritoneum. We evaluated the use of the rat epididymal fat pad as a microcapsule implantation site for biocompatibility studies. The recovery rate of microcapsules containing 85Sr-labeled microspheres was 99.6 +/- 0.75%. Microcapsules made from the same batch of nonpurified alginate, were injected into both fat pads of male Lewis rats (n = 18) and retrieved 14 days later. A semiquantitative fibrosis score scaled from 0 to 3.0 showed that the pericapsular reaction was uniform throughout a fat pad, and that the results of the two fat pads were equivalent because the null hypothesis of inequivalence was rejected (P < .001). Thus, this method can be used to compare the biocompatibility of microcapsule of differing compositions.

Adipose Tissue↗
PubMed1987

Ecto-cyclic AMP-receptor in goat epididymal intact spermatozoa and its change in activity during forward motility.

Goat epididymal intact spermatozoa have been shown to possess on the external surface specific receptors that bind with high affinity to exogenous [8-3H]cyclic AMP. The ecto-cyclic AMP-receptor activity was not due to contamination of broken or "leaky" cells, if any. The binding reaction of [3H]cyclic AMP with the receptors was extremely rapid. Uptake of the labeled cyclic AMP to the sperm cytosolic fraction was undetectable. There was little leakage of cyclic AMP-receptors from intact spermatozoa during the binding assays. The binding reaction was proportional to cell concentration, specific and saturable at 250 nM cyclic AMP. The binding of the labelled cyclic nucleotide was nearly completely displaced at saturating concentrations (2.5 microM) of the unlabelled nucleotide. The ecto-receptors showed high specificity for binding to cyclic AMP. The Kd of the binding sites was approximately 1.7 X 10(-8) M. The binding interaction was highly sensitive to treatment with proteolytic enzymes: trypsin, chymotrypsin, or pronase (125 micrograms/ml). Sonication caused a nearly 450% increase of the ecto-receptor activity. The specific activity of the ecto-cyclic AMP-receptor was approximately twofold higher in the vigorously forwardly motile spermatozoa than in the "composite" cells, suggesting that the ecto-receptors may have a role in modulating flagellar motility.

Animals↗
PubMed1995

Different regulatory pathways involved in ATP-stimulated chloride secretion in rat epididymal epithelium.

The regulatory pathways involved in the ATP-stimulated Cl- secretion across rat epididymal epithelium were investigated by the short-circuit current (ISC) technique. Biphasic characteristic was observed in the ISC responded to ATP (0.01-10 microM). Inhibitor of P1 receptor, 8-phenyltheophylline (up to 100 microM), did not have any effect on both phases of the ATP-stimulated ISC. The order of potency for stimulation of the two phases in ISC was ATP > ADP >> AMP, adenosine, consistent with the presence of P2-purinoceptors. Cl- channel blocker, disulfonic acid stilbene (DIDS, 300 microM), only inhibited the first peak of the ATP-stimulated ISC while diphenylamine-dicarboxylic acid (DPC, 1 mM) reduced both, indicating the involvement of different conductance pathways. DIDS was found to have an inhibitory effect on Ca(2+)-activated ISC (induced by ionomycin, 10 microM) but not cAMP-activated ISC (induced by forskolin, 1 microM) which could only be blocked by DPC. Both peaks of the ATP-activated ISC could be significantly inhibited by pretreatment with a Ca(2+)-chelating agent, BAPTA-AM (50 microM). An increase in cellular cAMP content upon stimulation of ATP was measured by radioimmunoassay. No significant increase in cAMP production was observed in cells stimulated with adenosine. The ATP-induced cAMP increase was prevented by pretreatment with BAPTA-AM (100 microM) indicating that cAMP production upon ATP stimulation was secondary to an increase in intracellular Ca2+ concentration. These results indicate that the ATP-stimulated Cl- secretion could be mediated by Ca2+ and cAMP-dependent regulatory pathways giving rise to the biphasic nature of the ATP-induced ISC.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1979

An ultrastructural study of epididymal mouse spermatozoa binding to zonae pellucidae in vitro: sequential relationship to the acrosome reaction.

Mouse sperm bind to the zona pellucida of the egg prior to penetration of the zona and entry into the perivitelline space. The question then arises: when does the acrosome reaction occur relative to these processes? An ultrastructural study of mouse epididymal sperm bound to the surface of the zona and in the privitelline space was undertaken to clarify this point. Cumulus-free mouse eggs were inseminated in either a complete defined culture medium capable of supporting in vitro fertilization or in Tris/NaCl buffer containing Ca+2. Both media support sperm binding to the zona to the same extent; binding is complete in 15 minutes. Unbound sperm were removed by a step gradient density centrifugation to yield a preparation of eggs with sperm firmly bound. All sperm in the perivitelline space had undergone the acrosome reaction. Sperm bound at the surface of the zonae pellucidae of eggs recovered at ten minutes after insemination all had intact acrosomes. At 40 minutes after insemination, half of the sperm were intact; the other half were in the initial stages of the acrosome reaction. At 90 minutes after insemination, 12% of the sperm had undergone the full acrosome reaction and were starting to penetrate the zona; of the balance, half were in various stages of the acrosome reaction, while half were still intact. These findings support the hypothesis that the sequence of the early reactions leading to fertilization in the mouse is: intact sperm binding to zona; acrosome reaction at the zona surface; penetration of the zona.

Acrosome↗