Outer dense fibres: functional or structural elements?*

Summary. By electron microscopic studies it could be demonstrated that malformed outer dense fibres are a major cause of structural, flagellar disorder in human spermatozoa. Biochemical investigations of isolated outer dense fibres revealed that these flagellar substructures consist of three major polypeptides and do not contain phosphoproteins. They seem to have passive-elastic properties with respect to sperm motility. Further studies are required to elucidate the cause of the disturbed development of outer dense fibres, which may be due to inflammatory, toxic, or genetic influences.     

Detection of a mutation in the intron of Sperm‐specific glyceraldehyde‐3‐phosphate dehydrogenase gene in patients with fibrous sheath dysplasia of the sperm flagellum

The fibrous sheath is a unique cytoskeletal structure surrounding the axoneme and outer dense fibres of the sperm flagellum. Dysplasia of the fibrous sheath (DFS) is a defect of spermatozoa observed in severe asthenozoospermic patients and characterised by morphologically abnormal flagella with distorted fibrous sheaths. Sperm‐specific glyceraldehyde‐3‐phosphate dehydrogenase (GAPDS) is a glycolytic enzyme that is tightly associated with the fibrous sheath of the sperm flagellum. The enzymatic activity of GAPDS was investigated in sperm samples of seven patients with DFS and compared to that of normal spermatozoa (n = 10). The difference in GAPDS activity in DFS and normal spermatozoa was statistically significant (0.19 ± 0.11 and 0.75 ± 0.11 μmol NADH per min per mg protein respectively). Immunochemical staining revealed irregular distribution of GAPDS in the flagellum of DFS spermatozoa. Other five samples with typical alterations in the fibrous sheath were assayed for mutations within human GAPDS gene. In all five cases, a replacement of guanine by adenine was revealed in the intron region between the sixth and the seventh exons of GAPDS. It is assumed that the deficiency in GAPDS observed in most DFS sperm samples is ascribable to a disorder in the regulation of GAPDS expression caused by the mutation in the intron region of GAPDS gene.     

Electron microscopic observations of human sperm whole-mounts after extraction for nuclear matrix and intermediate filaments (NM-IF)

The extraction for nuclear matrix and intermediate filaments (NM-IF) is used to reveal, isolate and study these highly resistant structures in different cell types. We applied for the first time this chemical dissection to human spermatozoa and observed them as whole-mounts by unembedded electron microscopy. The general appearance of NM-IF extracted sperm cells was preserved, showing the intermediate filament-like properties of their cytoskeletal components. In most heads, a network was observed in subacrosomal position, consisting of hubs interconnected by filaments. It seemed to be overlaid on another, finer network. The neck retained its integrity, allowing observations of the three-dimensional structure of the segmented columns. More distally, axoneme and outer dense fibres were covered by submitochondrial cytoskeleton in the middle piece and fibrous sheath in the principal piece, with the annulus usually detached from the fibrous sheath. End piece microtubules were retained in most cells and showed a tendency of cohesion, remaining in a parallel bundle or forming flat sheets. In conclusion, our results provided additional structural details of human sperm cytoskeleton and demonstrated the advantages of combining different methodological approaches in ultrastructural research.     

三种实验性IgA肾病模型的比较

目的探讨建立一种理想的IgA肾病（IgAN）动物模型方法。方法分别采用葡聚糖G200、大肠杆菌外膜蛋白和金葡菌的细胞膜20肽抗原决定簇诱导小鼠IgA肾病模型。用分子生物学和病理学方法对3组IgAN模型小鼠进行鉴定和比较。结果（1）葡聚糖组尿蛋白增高，伴有血尿；免疫荧光显示部分肾小球大量IgA沉积；光镜下肾小球系膜细胞增多，肝和脾可见弥漫性的粉染物质沉积；电镜下肾小球系膜区少量低电子密度的致密沉积物，肝和脾可见淀粉丝样物质沉积。（2）大肠杆菌外膜蛋白组尿蛋白增高，伴有血尿；免疫荧光显示肾小球有少量IgA沉积；光镜下肾小球系膜细胞轻度增多，间质炎细胞浸润明显；电镜下肾小球系膜区无电子致密沉积物。（3）金葡菌细胞膜20肽抗原决定簇组尿蛋白增高，伴有血尿；免疫荧光显示多数肾小球均可见大量IgA沉积；光镜下肾小球系膜细胞增多，伴系膜基质轻度增生；电镜下肾小球系膜区和基底膜的内皮细胞下可见高电子密度的致密沉积物。结论金葡菌细胞膜20肽抗原决定簇组诱导的IgAN模型从临床表现和病理学变化与人IgAN极其相似，是3种IgAN模型中最理想的IgAN模型。     

Immunocytochemical localization of acrosin on both acrosomal membranes and in the acrosomal matrix of porcine spermatozoa

Immunocytochemical techniques were employed to determine, at the ultrastructural level, the location of acrosin in porcine spermatozoa. Antisera to highly purified porcine acrosin was produced in rabbits. The (Fab')2 fragments of the immunoglobulins were purified and conjugated with horseradish peroxidase (HRP). Washed, formaldehyde-fixed spermatozoa were reacted with the labeled antiacrosin immunoglobulins, utilizing a direct staining technique. Electron microscopy revealed that the peroxidase reaction product of HRP-antiporcine acrosin was distributed evenly over the outer acrosomal membrane of spermatozoa with intact acrosomes. The labeled antibody was also distributed evenly over the inner acrosomal membrane of cells when the overlying acrosomal structures were absent. In some spermatozoa, labeling was noted throughout the acrosomal matrix. No significant labeling was observed in control specimens when spermatozoa were exposed to HRP-antiporcine acrosin immunoglobulins that had been adsorbed previously with excess purified acrosin or exposed to HRP-conjugated rabbit antiporcine immunoglobulins. This pattern of labeling is consistent with the hypothesis that acrosin may function as a zona lysin. The observation that the outer acrosomal membrane and acrosomal matrix are labeled suggests that acrosin is not exclusively located on the inner acrosomal membrane and, thus, could participate in physiologic events other than zona penetration.     

Release, extraction, and stability of hyaluronidase associated with human spermatozoa. Comparisons with the rabbit

In contrast to the rabbit: 1) no hyaluronidase could be detected in fresh or frozen human seminal plasma, all color formation on assay being due to a dialyzable, heat stable factor; 2) almost no hyaluronidase could be extracted from frozen-thawed human testicles; 3) the hyaluronidase from human spermatozoa was rapidly inactivated upon release, either spontaneously or on extraction; and 4) a large decrease in hyaluronidase activity occurred when human spermatozoa were stored under various conditions. Rabbit spermatozoa contained six to 13 times more hyaluronidase than human spermatozoa. These results show that distinct species differences exist in the hyaluronidase associated with spermatozoa. None of the human genital tract sources studied could be used to obtain adequate amounts of hyaluronidase for the further isolation and purification of the enzyme. For both human and rabbit spermatozoa, it was optimal to add the cells directly to the assay system for the quantitation of hyaluronidase on spermatozoa rather than extracting the spermatozoa and testing the extracts. The spermatozoa of both species appear to be capable of digesting hyaluronic acid directly. As had previously been found for acrosin, a higher amount of hyaluronidase was maintained when human spermatozoa were cryopreserved in a zwitter buffer (TESTCY) rather than in glycerol.     

Quantitative ultramorphological evaluation of swim-up spermatozoa used in human in vitro fertilization and transcervical intrauterine insemination

Ultramorphological changes that occur on the sperm head during in vitro incubation of human spermatozoa was investigated using transmission electron microscopy (TEM). Motile spermatozoa that swim-up were processed for TEM. Washed but unincubated sperm heads had all of the fine structural characteristics of normal spermatozoa: intact plasma membrane, acrosome, equatorial segment, postacrosomal sheath, subacrosomal space filled with fine granular material, dense nucleus containing conspicuous nuclear vacuoles of differing sizes and numbers, and faintly discernible nuclear membrane. The procedure of washing and centrifugation did not alter the structural integrity of spermatozoa. Any evidence of ultramorphological changes in the incubated spermatozoa appeared to be confined to the surface of the anterior two-thirds of the sperm head. These changes were characterized by detachment of plasma membrane, fusion of plasma and acrosomal membranes, vesiculation of membranes, and exposure of acrosomal contents. There was a significant (p less than 0.001) time-dependent increase in the proportion of spermatozoa with such changes. The anterior border of these denuded sperm heads were bound only by the acrosome that appeared as electron-dense granular material on the outer margin and attached on its inner border to the inner acrosomal membrane. Furthermore, in vitro incubation of washed spermatozoa did not lead to any time-dependent degenerative changes.     

特发性弱精子症精子与正常精子蛋白质双向电泳图谱分析

目的:探讨双向电泳技术在人类精子差异表达蛋白研究中的应用。方法:运用固相pH梯度双向凝胶电泳分离4例正常人和4例弱精子症患者精液标本的总蛋白质,凝胶银染后,用PDQuest软件进行分析,分辨出差异表达蛋白。结果:按照5倍的表达量计算,发现有差异表达的蛋白质点7个,2个点在弱精子症精子中高表达,而在正常精子为低表达;相反,在正常精子中高表达的5个点,而在弱精子症为低表达。结论:初步建立了正常精子和弱精子症患者精子的双向电泳图谱,并发现两者之间存在一些差异表达蛋白,为进一步研究特发性弱精子症精子差异表达蛋白的分离及鉴定奠定了良好基础。     

The Sperm Acrosome: Immunological Analysis using Specific Polyclonal and Monoclonal Antibodies Directed Against the Outer Acrosomal Membrane of Boar Spermatozoa

An antiserum to the purified porcine outer acrosomal membrane (OAM) was raised in female Balb/c mice and was characterized by means of an indirect ELISA. The hyperimmune serum reacted selectively with the acrosomal cap of the sperm head and showed an extremely good cross reactivity with bull and human spermatozoa when assayed by indirect immunofluorescence. Immunoelectron microscopy using the protein A-gold method further confirmed the specificity of the anti-OAM-antiserum for the OAM. In an effort to identify the OAM antigens recognized by the hyperimmune serum and to analyse the extent of cross reactivity on a molecular level, the SDS-extractable proteins were separated by SDS-PAGE, transblotted and immunoprinted using an 125J-conjugated anti-mouse-antibody. To facilitate functional and structural analysis of distinct OAM-proteins monoclonal antibodies were generated by hybridization of mouse myeloma cells with the splenocytes of female Balb/c mice immunized with the purified OAM. One fusion resulted in about 100 anti-OAM-antibodies secreting hybridoma cultures, of which about 30% showed cross reaction with human and bull spermatozoa. Four stable cell lines were selected for this study secreting antibodies directed against the outer acrosomal membrane of boar spermatozoa. Whereas the polyclonal immune mouse serum stained the entire acrosomal cap, the four hybridoma antibodies generated a patch-work-like immunofluorescence pattern over the acrosome. HPLC-ELISA of the solubilized OAM revealed first information on the nature of the corresponding membrane antigen.     

Ultrastructural alterations of frozen-thawed Asian elephant (Elephas maximus) spermatozoa

Intact plasma and acrosome membranes and functional mitochondria following cryopreservation are important attributes for the fertilizing ability of spermatozoa. In the present study, functional and ultrastructural changes of Asian elephant spermatozoa after cryopreservation either in TEST + glycerol or HEPT + dimethyl sulphoxide (DMSO) were evaluated by fluorescent techniques and electron microscopy. Sperm frozen in TEST + glycerol had higher proportion of sperm with intact plasma (49.1 +/- 9.2% vs. 30.9 +/- 3.9%) and acrosomal (53.7 +/- 4.9% vs. 35.8 +/- 6.1%) membranes, as well as active mitochondria (57.0 +/- 7.2% vs. 42.0 +/- 5.0%) than those cryopreserved in HEPT + DMSO. The results obtained from electron microscopy were similar to those obtained by fluorescence microscopy. The percentage of normal spermatozoa was higher when spermatozoa were frozen in TEST + glycerol than those frozen in HEPT + DMSO (31.8 +/- 5.6 vs. 28.5 +/- 6.4). The ultrastructural alterations revealed by transmission electron microscopy could be classified as (i) distension of plasma membrane, while the acrosome was swollen; (ii) disruption or loss of plasma membrane, while acrosome was swollen with distended outer acrosomal membrane; (iii) disruption or loss of plasma and outer acrosomal membrane with leakage of acrosome content; (iv) extensive vesiculation of plasma and outer acrosomal membrane and leakage of acrosome content; (v) a complete loss of both plasma membrane and outer acrosomal membrane; and (vi) swelling of mitochondria. These findings suggest that the freezing and thawing procedure caused structural damage to elephant spermatozoa, especially in the plasma membrane, acrosome and mitochondria. Fluorescence and electron microscopic evaluations are potentially a powerful tool in the analysis of elephant spermatozoa after freezing and thawing.     

Histochemical demonstration of zinc ions in ejaculated human semen

A revised in-vitro technique for autometallographic demonstration of chelatable zinc in the human ejaculate is presented, and the localization of the loosely bound pool of zinc ions is described in semen smears and at the ultrastructural level. In semen smears, black autometallographic (AMG) grains indicated the presence of zinc ions dispersed between the spermatozoa. These AMG grains have the same size as grains associated with the sperm tail and may have the same origin. EM analysis of AMG-developed smears fixed in osmium suggested that the detected zinc ions might be related to huge protein molecules present in semen and adhering to the surface of the spermatozoa.
Spermatozoa in AMG-stained smears exhibited zinc ions in the midpiece and head, and also joined to the membrane of the tail. Washed spermatozoa exhibited zinc ions only within the midpiece. Ultrastructurally, they were found located in the helecine mitochondria. A few grains were found in the acrosome of the washed spermatozoa. Treatment with the chelating agent DEDTC resulted in complete bleaching of the zinc staining. These findings and the fact that calcium EDTA acid blocks the plasma and surface staining, but not the acrosomal and mitochondrial staining, suggest that chelatable zinc ions exist in two separate pools in human semen.     

Proteasomes in human spermatozoa

In the present study we describe the localization of proteasomes in human spermatozoa by means of immunolabelling with different monoclonal and polyclonal antibodies detected by confocal microscopy. Western blotting confirmed the specificity of the antibodies and has shown that proteasomes are present in spermatozoa and in seminal fluid. In spermatozoa proteasomes are concentrated in the neck region where the centrioles are located. Some labelling was also detected at the periphery of the head, but no proteasomal antigens were detected in either the nucleus or associated with the flagellum. Proteasome inhibitors did not affect the motility of the spermatozoa, acrosome reaction nor zona binding. It is hypothesized that paternal proteasomes enter the oocyte during fertilization in tight association with the centrioles and may serve a special function during further development which can be associated with the function of a hypothetical proteolysis centre.     

Localization of Hsp60 and Grp78 in the human testis, epididymis and mature spermatozoa

Molecular chaperones of the heat shock proteins (HSP) family are important in numerous cellular processes. In this study, the expression of Hsp60 and Grp78 proteins was investigated in the male reproductive tract. The cellular distribution of Hsp60 and Grp78 proteins was analysed in the human testis and epididymis by immunohistochemical approaches. DNA microarray technology was used to analyse HSP60 and GRP78 gene expression along human epididymis. The cellular localization of these chaperone proteins in ejaculated spermatozoa was investigated by indirect immunofluorescence and by Western blot following sperm sub-cellular fractionation. In the human testis, Hsp60 was detected in spermatogonia, whereas a strong Grp78 staining was observed in spermatocytes and round spermatids. Grp78 protein was also observed in the epididymal epithelium, whereas no Hsp60 staining was observed in this organ by immunohistochemistry. The presence of both Hsp60 and Grp78 RNA in human epididymis was confirmed by microarrays. In ejaculated spermatozoa, Hsp60 was localized in the mid-piece, whereas Grp78 was detected in the neck region. These results indicate that in addition to being expressed in human testis spermatogenic cells, both Hsp60 and Grp78 proteins persist in ejaculated spermatozoa. These findings are in agreement with the involvement of Hsp60 and Grp78 during spermatogenesis and in sperm functions such as fertilization.     

Secretory Phospholipase A2 Group IID Is Involved in Progesterone-Induced Acrosomal Exocytosis of Human Spermatozoa

Phospholipase A2 (PLA(2)) plays a major role during acrosomal exocytosis (AE) in mammalian spermatozoa, but the identity of PLA(2) subtypes present in spermatozoa remains elusive. This study explored whether secretory PLA(2) Group IID (sPLA(2)-IID) isoform is present in human spermatozoa and whether it is involved in AE. Localization and expression of sPLA(2)-IID in human spermatozoa were explored by immunofluorescence staining and Western blot analysis. Occurrence of AE was evaluated by triple staining, and arachidonic acid (AA) levels were quantified by gas chromatography-mass spectrometry. Sperm motion parameters and hyperactivation were analyzed by computer-assisted sperm analysis. sPLA(2)-IID was localized in the postacrosomal region of the head and the midpiece of tail in human sperm. A 16-kd protein band was detected by Western blotting in sperm extracts. Progesterone-induced AE was significantly inhibited in a concentration-dependent manner using a sPLA(2)-IID neutralizing antibody. The increase in AA levels seen during progesterone-stimulated exocytosis was significantly abrogated by the antibody. The sPLA(2)-IID antibody significantly inhibited hyperactivation, sperm curvilinear velocity, and amplitude of lateral head displacement, but it did not affect the proportion of motile sperm. In conclusion, sPLA(2)-IID is present at the head and midpiece in the human sperm, and activation of such sPLA(2)-IID seems to be involved in AE. Therefore, sPLA(2)-IID isoform plays a functional role during the AE in human sperm.     

人精子膜蛋白的二维电泳实验研究

目的 :利用二维电泳技术对人精子膜蛋白进行分离 ,为建立正常人精子膜蛋白的蛋白质图谱打下基础。　方法 :使用Percoll密度梯度离心筛选精子 ,用等电聚焦结合聚丙烯酰胺凝胶电泳对人精子膜蛋白进行二维电泳分析。　结果 :图像分析软件共可识别出约 80 0个蛋白质斑点 ,绝大多数蛋白的相对分子质量为 2 0 0 0 0～ 10 0 0 0 0 ,等电点为 3.0～ 7.0。　结论 :精子膜上至少有 80 0种蛋白 ,二维电泳可以对精子膜蛋白进行较精确的分离     

外周致密纤维1在人精子中的表达差异及其意义

目的:比较外周致密纤维1(ODF1)在健康男性和弱精子症患者精子中的表达差异。方法:根据WHO标准,收集正常男性和弱精子症患者的精液标本各20份,Percoll非连续梯度离心法分离精子,收集95%Percoll以下和57%与76%Percoll层之间的精子,以排除生精细胞和白细胞的污染;采用逆转录-多聚酶链式反应(RT-PCR)和Western印迹方法,从mRNA和蛋白水平检测ODF1的表达。结果:RT-PCR结果表明,与正常男性组相比,ODF1在弱精子症患者精子中的mRNA表达水平显著降低(2.79±0.28vs1.35±0.25,P<0.05);免疫印迹与RT-PCR结果一致,与正常男性组相比,弱精子症患者精子中的ODF1蛋白的表达亦显著降低(3.64±0.34vs1.44±0.26,P<0.05)。结论:ODF1在弱精子症患者精子中的表达显著降低,提示其可能与精子活动力低下有关。     

On the Teratogenesis of Round-Headed Spermatozoa: Investigations with Antibodies Against Acrosin, an Intraacrosomally Located Acrosin-Inhibitor, and the Outer Acrosomal Membrane

Acrosin, the outer acrosomal membrane (OAM) and an acrosin inhibitor were studied in testicular cells and ejaculated spermatozoa of fertile men and in those of an infertile patient with exclusively round-headed spermatozoa in his ejaculates. The investigations were performed with the aid of immunohistochemical techniques using specific antibodies against the three acrosomal markers isolated from boar spermatozoa. The spermatozoa of fertile men exhibit staining for acrosin, the OAM and the acrosin inhibitor in the cap region while the round-headed spermatozoa of the patient are totally negative for the three markers, clearly supporting the conclusions of other authors that round-headed spermatozoa lack acrosomes. The lack of the acrosin system was further substantiated by the gelatin substrate film technique. In the course of normal human spermatogenesis acrosin, the OAM and the acrosin inhibitor we first demonstrable in early round spermatids, namely in identical compartments adjacent to the cell nucleus. During spermatid differentiation the staining for the three markers becomes flattened over the nucleus, resulting in a cap-like structure in testicular spermatozoa. In contrast to the ejaculated round-headed spermatozoa, the early round spermatids in the testis of the infertile patient exhibit fluorescent staining for the three markers in the region adjacent to the nuclear membrane. In the course of further spermiogenesis, the staining did not extend over the nuclear membrane, as was observed during normal spermiogenesis, but became separated from the nuclear membrane, as was observed during normal spermiogenesis, but became separated from the nuclear membrane, was translocated at various locations in the cytoplasm and was finally eliminated with the loss of the cytoplasm. These results are in accordance with the results of electron microscopically investigations on the teratogenesis of round-headed spermatozoa. Furthermore, the developmental pattern of the acrosin inhibitor during normal and abnormal spermiogenesis supports the intraacrosomal location of the acrosin inhibitor recently described by Tschesche et al. (1982).     

Detection of inflammation following renal ischemia by magnetic resonance imaging

BACKGROUND: Determining the disease culprits in human acute renal failure (ARF) has been difficult because of the paucity of renal biopsies and the lack of noninvasive methods to determine the location or cause of renal injury. Recently, ultrasmall superparamagnetic iron oxide (USPIO) particles have been used to detect inflammation in animal models. Therefore, we tested if USPIO enhanced magnetic resonance imaging (MRI) could detect inflammation in ischemic ARF in rats. METHODS: Rats were subjected to 40 or 60 minutes of bilateral ischemia or injected with mercuric chloride. MR images were obtained before and 24 hours after USPIO injection, and the signal intensity decrease in the outer medulla was measured. Cells containing iron particles were identified by iron staining and transmission electron microscopy (TEM). Leukocytes were identified by ED-1 and chloracetate esterase staining. RESULTS: Injection of USPIO particles caused a black band to appear in the outer medulla at 48, 72, and 120 hours after ischemia. This band was not detected in normal animals, 24 hours after ischemia, or 48 hours after mercuric chloride injection. The signal intensity change in the outer medulla correlated with serum creatinine and the number of iron particle containing cells. Most infiltrating cells were macrophages, and iron particles were present inside lysosomes of macrophages. USPIO injection did not alter renal function in normal or ischemic animals. CONCLUSION: USPIO-enhanced MRI could detect inflammation noninvasively from 48 hours after 40 or 60 minutes of renal ischemia in rats. This method might be useful to understand the pathogenesis of human ARF and to evaluate the effectiveness of anti-inflammatory agents.     

Characterization of lectin receptors isolated from the outer acrosomal membrane of boar spermatozoa

The outer acrosomal membrane (OAM) of boar spermatozoa was isolated by homogenization and centrifugation through modified colloidal silica. Homogeneity of the isolated membrane fraction (OAM) was revealed by transmission electron microscopy. At least 10 protein components could be discriminated by SDS-PAGE electrophoresis of the OAM, with molecular weights ranging from 340 to 15 kdal. Radiolabelling of the externally disposed carbohydrate side-chains by [3H]borhydride reduction of the isolated membrane, oxidized by use of galactose oxidase, revealed one main galactoprotein with a reduced molecular weight of about 270 kdal. This was identified as the RCA-120 receptor protein by means of lectin-affinity chromatography, high resolution gelfiltration and SDS-PAGE. Screening of the Con A binding properties of the solubilized membrane components partially isolated by affinity chromatography and HPLC was performed by an enzyme-linked-lectin-assay (ELLA). Electrophoretic analysis including a Con A-peroxidase staining procedure allowed the identification of 4 Con A binding proteins of the OAM with molecular weights of 120, 110, 88 and 66 kdal.     

Electron microscopic evidence on the acrosomal status of bound sperm and their penetration into human hemizonae pellucida after storage in a buffered salt solution.

The hemizona assay (HZA) was developed to evaluate sperm binding potential using microbisected human zona pellucida. In this study, eight human oocytes stored in a buffered salt solution for 60 days were bisected into two identical hemispheres (hemizonae) and coincubated with the spermatozoa from a fertile man. All evaluated spermatozoa were tightly bound to the outer surface or had begun penetration into the zona pellucida. The hemizonae with bound spermatozoa were prepared and fixed for transmission electron microscopy (TEM) using standard techniques. Among the 108 sperm bound to the zone we were able to evaluate 25 by TEM. Twenty (80%) of the zona bound spermatozoa were partially or completely acrosome reacted, while six (20%) of the zona bound sperm had intact acrosomes. Acrosome intact, partially acrosome reacted and completely reacted spermatozoa were observed within the zona. Penetration pathways or tunnels were seen within the zona matrix. The results illustrate, that typically spermatozoa tightly bound the human zona pellucida show induction of the acrosome reaction. Importantly, following storage of human eggs in salt solution (buffered to 7.4), the zona pellucida retain their biological and functional characteristics for at least 90 days.