Detection of human cytomegalovirus in motile spermatozoa and spermatogenic cells in testis organotypic culture
© Naumenko et al; licensee BioMed Central Ltd. 2011
Received: 11 April 2011
Accepted: 28 June 2011
Published: 28 June 2011
The presence of human cytomegalovirus (HCMV) in male genital tract suggests its vertical transmission with spermatozoa and the development of a potentially dangerous fetal infection. The objective of the present study was to evaluate the possibility of intracellular HCMV localization in male germ cells and to examine the effect of the virus on human spermatogenesis.
Semen samples from 91 infertile and 47 fertile men were analyzed. HCMV was detected by real time PCR, rapid culture method and PCR in situ. Human testis organotypic culture and quantitative karyological analysis were used to investigate viral effects on spermatogenesis. Localization of HCMV in immature germ cells and spermatozoa was studied by immunostaining with monoclonal antibodies and ultrastructural analysis of infected organotypic culture.
Viral DNA was detected in 12.3% samples of motile spermatozoa, while infectious activity only in 2.9% infertile and fertile men without statistically significant intergroup difference. According to PCR in situ, the mean percentage of infected cell in both groups was 1.5% (0.25%-15%), which can serve as a criterion for evaluating the risk of HCMV transmission. In HCMV-infected organotypic culture viral antigens were identified in spermatides on day 4, in spermatogonia and spermatocytes on day 8, and in spermatozoa on day 14. Empty and full capsides and virions were visualized in germ cells by electron microscopy. The number of cells before introduction in culture was taken for 100%. On day 14 infected culture contained 36.8% spermatogonia, 18.7% spermatocytes, 27.6% round spermatides and 42.5% elongated spermatides; in comparison with 82.2%, 51.5%, 70.4% and 65.7% in uninfected culture, respectively (all p < 0.05). There were no changes in the number and viability of spermatozoa.
HCMV was detected in male germ cells, both in sperm samples and in testis organotypic culture. The virus may infect immature germ cells which develop to mature HCMV-carrying spermatozoa. A considerable decrease in the number of immature germ cells indicates that HCMV produces a direct gametotoxic effect and can contribute to male infertility.
Keywordshuman cytomegalovirus infertility spermatogenesis testis organotypic culture
Male infertility accounts for 20-50% infertile couples and is often associated with genital infections . Negative effects on reproductive function have been proposed for such viruses as the human immunodeficiency virus, human papillomavirus, herpes simplex virus, Epstein-Barr virus [1–4]. Human cytomegalovirus (HCMV) is widespread in human population and can be transmitted sexually. The effects of HCMV on spermatogenesis and its vertical transmission with sperm cells have not been investigated in sufficient detail due to the low detection rate of HCMV in semen - no more than 2.9% by the culture method [5, 6] and 1.4-8.7% by PCR [5, 7, 8]. At the same time Neofytou et al. have detected HCMV DNA by PCR in the semen of 56.9% asymptomatic fertile and infertile patients .
There is a controversy over the effects of HCMV on the major parameters of sperm quality - concentration, motility and morphology of gametes. A correlation between high concentration of HCMV in ejaculate and a transient decrease in the spermatozoa motility have been established , and the concentration of sperm cells has been found to decrease in patients with HCMV in semen . However, the majority of researchers have found no HCMV effect on sperm quality [3, 7, 12].
The issue of intragamete localization of HCMV is open to debate. The attempts to infect spermatozoa in vitro have been unsuccessful . Investigation of interactions between HCMV and testicular cells is hampered by the possibility of autoimmune orchitis after biopsy. High species-specificity of HCMV impedes the investigation of processes occurring in human organism on animal models. In an attempt to overcome these difficulties we developed the model of HCMV infection in an organotypic culture of human testis. Using this model we demonstrated the possibility of intracellular HCMV localization in immature and mature male germ cells and HCMV influence on spermatogenesis.
Materials and methods
Semen samples were obtained from 138 men, including 91 infertile men (Group I) and 47 healthy donors enrolled in the sperm donor program (Group II). The informed consent was obtained from all patients.
Semen samples were fractionated by gradient centrifugation with SupraSperm reagent (Origio, Jyllinge, Denmark) according to the World Health Organization Laboratory Manual for the Examination and Processing of Human Semen (2010). The fraction of motile spermatozoa (MS) was washed two times in 2 ml of Dulbecco modified Eagle Medium (DMEM; Paneko, Moscow, Russia) by centrifugation and used as described below.
Virus and cell culture
HCMV AD 169 strain was provided by the Russian Federation State Collection of Viruses. The virus was propagated and titrated in human embryo lung fibroblasts (HEF).
Rapid culture method (RCM)
RCM was used for detection of HCMV infectious activity in the samples. The material (0.2 ml) was injected into each well of 24-well culture plate (Costar, Washington DC, USA) with HEF confluent monolayer, incubated for 1 h at 37°C in an atmosphere of 95% air/5% CO2. The cells were washed 2 times in serum-free culture medium, incubated for 48 h in 1 ml of DMEM with 2% fetal calf serum (FCS; Gibco, Carlsbad, CA, USA), washed 2 times in PBS and fixed in cold methanol. HCMV was identified by immunoperoxidase staining with monoclonal antibody (Mab) against HCMV pp65 protein (DAKO, Glostrup, Denmark). Immunolabeled cells were calculated in an inverse light microscope LABOVEWRT FS (Leitz, Oberkochen, Germany).
HCMV DNA detection and quantification by real-time PCR
HCMV DNA extraction was performed from 200 μl of samples using QIAamp DNA mini kit (QIAGEN, Hilden, Germany) according to the manufacturer's protocol. In brief, 200 μl of sample and 10 μl of the STI-87 positive internal control (PIC; Interlabservice, Moscow, Russia) were added to 200 μl of AL-buffer and heated at 56°C for 15 min. 200 μl of 96% ethanol was added, applied to columns and washed as per the manufacturer's instruction with the final elution in 200 μl of the kit AE-buffer preheated to 50°C. Real-time PCR was performed using the Amplisense CMV-screen/monitor-FL kit (Interlabservice) according to the manufacturer's protocol. Real-time amplification was carried out using 10 μl DNA eluate combined with 10 μl PCR-mix-1-FL and 5 μl PCR-mix-2-FL using Rotor-Gene 6000 Instrument (Corbett Research, Doncaster, Australia) with the following cycling parameters: pre-denaturation at 95°C for 15 min, 95°C for 5 s, 60°C for 20 s and 72°C for 15 s for 45 cycles. Data acquisition was performed in both JOE/Yellow (for HCMV DNA) and ROX/Orange (for the STI-87 PIC) channels during the annealing (60°C) stage. For quantification of HCMV DNA two standard positive sample KSG1 (104 copies per reaction mixture) and KGS2 (102 copies per reaction mixture) (Interlabservice) were included in the run. Calculations of Ct, preparation of standard curve and quantification of DNA in each sample were performed by Rotor-Gene Operating Software, version 1.8 (Corbett Research).
PCR in situ
Washed-off MS were transferred to glass slides, centrifuged for 5 min at 1500 rpm in Cytospin 4 (Thermo Electron, Waltham, USA), air dried, fixed in 10% formaldehyde for 4 h and washed twice in 0.05 M Tris-HCl. The preparations were then incubated with proteinase K (DAKO) for 30 min at 37°C. Amplification with biotinilated primers (Gentech, Moscow, Russia) was carried out using T1 cycler (Biometra, Goettingen, Germany). Viral DNA was detected with the biotin-streptavidin-peroxidase complex (DAKO) and diaminobenzidene (Sigma-Aldrich, St Louis, MO, USA). The proportion of sperm cells containing HCMV DNA was calculated after analysis of at least 2000 cells.
Spermiological and quantitative karyological analysis
Spermiological analysis was performed according to the World Health Organization Laboratory Manual for the Examination and Processing of Human Semen (2010). The immature germ cells (IGC) in sperm samples were identified by morphological criterions under a light microscope BX51 (Olympus, Tokyo, Japan). At least 200-300 IGC were calculated in each slide. The proportions of spermatids and primary spermatocytes at early stages (leptotene, zygotene, pachytene and diplotene) and cells that could not be identified (classified as unidentified and/or degenerated) were calculated as described previously .
Organotypic culture of human testis explants
The procedures followed were in accordance with ethical standards of the Helsinki Declaration and were approved by the local Ethics Committee of the D.I. Ivanovsky Institute of Virology of Ministry of Health and Social Development of Russian Federation; informed consent was obtained from all patients. Testis samples from 3 patients with prostate cancer (62, 65 and 67 years old) were transported in fresh medium on ice immediately following orchidectomy. Testicular tissues were carefully dissected with scissors into 3 mm3 fragments. In each well of a six-well plate, two fragments were placed onto a permeable membrane insert (Falcon Labware, Mt Pritchard, NSW, Australia) and incubated at the interface between air and 2 ml of DMEM with 10% FCS (Gibco), 1 mmol/l sodium piruvate, 100 ng/ml vitamin A, 50 ng/ml vitamin C and 200 ng/ml vitamin E (all from Sigma-Aldrich), 4 mmol/l glutamine, 10 μg/ml insulin, 5 μg/ml transferrin and 50 μg/ml gentamycin (all from Paneko) at 37°C in an atmosphere of 95% air/5% CO2. Culture medium was replaced every other day.
HCMV-infection of testicular explants
Fragments were incubated with 0.025 ml of HCMV inoculate for 1 h at 37°C. Multiplicity of infection (MOI) was 0.0001-0.001 plaque forming units (PFU) per cell. Control uninfected cultures were incubated in DMEM under the same conditions. Then explants were washed three times in 1 ml DMEM and the culture was established for up to 14 days as described above. Viral load was estimated every other day in culture medium by PCR and RCM starting from Day 2. Three explants were analyzed in each point.
For histological analysis, testicular explants (3 mm3) were fixed in neutral buffered 10% formaldehyde for 24 h at 4°C, dehydrated in a series of graduated ethanol concentrations (70%, 96% and 100%), embedded in paraffin, sectioned at 4.0 μm and stained with Caracci's hematoxylin (BisVitrum, S.-Peterburg, Russia) for examination. The following morphological criteria were used for analysis of germ cells viability and explants architecture: cell number, cell size and location, signs of apoptosis, and histological characteristics of seminiferous tubules, including the basal membrane structure.
To reveal HCMV proteins in the testis explants immunostaining with Mab to HCMV pp65 was performed on formaldehyde-fixed, paraffin-embedded tissues. Antigen retrieval was performed as follows: deparaffinized and dehydrated sections were treated for 20 min at 750 Wt in microwave oven (Sanyo, Moriguchi, Osaka, Japan) in 10 mM citrate buffer (pH = 6.0, DAKO) and then washed in 0.05 mol/l phosphate-buffer saline (PBS, pH 7.6; Gibco). Endogenous peroxidase was inactivated in deparaffinized sections by 5-min treatment in PBS with 3% H2O2. Slides were processed by PBS supplemented with 2% bovine serum albumin (BSA, Sigma-Aldrich) to block the non-specific sites, before overnight incubation at 4°C with the Mab to HCMV pp65 (0.02 ug/ml) (DAKO) diluted in PBS with 1% BSA. Next steps were performed at room temperature. Reagents from UltraVision LP Large Volume Detection System kit (Thermo Scientific, Fremont, USA) were added according to the manufacturer's protocol after washing 4 times in PBS. The following substrate was used: 0.5 mg/ml diaminobenzidine (Sigma-Aldrich) in 0.05M TRIS-HCL, pH 8.0 with 3% H2O2. Sections were prepared immediately after tissue dissection and on days 2, 4, 7 and 14 after introducing in culture. Stained cells were identified and photographed with a BX51 microscope coupled to a digital macro camera U-CMAD3 (Olympus).
Transmission electron microscopy (TEM)
TEM was performed immediately after tissue dissection and on days 2, 4, 7 and 14 of culturing. Two infected and two uninfected explants were analyzed in each point. The explants were fixed in 2.5% glutaraldehyde in 0.1 M buffered sodium cacodylate (pH 7.4) for 24 h at 4°C, postfixed in 1% OsO4 in 0.1 M sodium cacodylate buffer at room temperature for 40 min, then dehydrated in gradual ethanol concentrations (70%, 96% and 100%) and, subsequently, submitted to progressive impregnations in epon resin (Sigma-Aldrich). Polymerization was carried out at 60°C for 48 h. Ultrathin sections were cut in an ultratome III (LKB, Bromma, Sweden), stained with uranyl acetate and lead citrate (Sigma-Aldrich) and examined in a JEM-100 S electron microscope (JEOL, Tokyo, Japan) at 80 kV.
Statistics and data analysis
The analysis was performed in StatXact 8 (Cytel, Cambridge, MA, USA) using Student's paired t-test, χ2 test and Mann-Whitney test. P < 0.05 was considered statistically significant.
HCMV detection in motile spermatozoa
Detection of HCMV in the fraction of motile spermatozoa
Frequency of HCMV detection by
Percentage of spermatozoa containing HCMV DNA by PCR in situ, median % [min, max]
rapid culture method
Group I (Infertile)
10/91 b (11%)
1.7 c [0.25; 15]
Group II (Fertile)
1/47 a (2.1%)
7/47 b (15%)
0.5 c [0.35; 5]
Groups I and II
1.5 [0.25; 15]
Spermiological and quantitative karyological analysis of HCMV-infected sperm
Analysis of immature germ cells population in the HCMV-infected sperm
Spermatocytes, median %
Spermatides, median %
Unidentified/degenerative cells, median %
Uninfected (n = 25)
HCMV-infected (n = 20)
HCMV-infection of testis organotypic culture
In order to study the effect of HCMV on spermatogenesis in more detail, we developed a model of HCMV infection in the human testis organotypic culture. It was demonstrated in preliminary experiments that general architecture of explants as well as viability of all germ cells preserved at least up to 14 days in culture.
HCMV markers in human testis organotypic culture
Method (viral load)
Days post infection
PCR (DNA copies/ml)
HCMV detection in testicular cells
Decrease of the germ cells population in HCMV- infected testis explants
Quantitative analysis of immature and mature germ cells in HCMV-infected human testis organotypic culture
Organotypic culture in vitro, days
The possibility of vertical transmission of herpes viruses with male gametes has been declared by several investigators [15, 16]. In the first part of this work we studied intracellular HCMV localization in male gametes as a potential transmission vector of infection. HCMV DNA was found in 12.3% of sperm cells (mean for Groups I and II), and infectious virus - in 2.9% of all cases. The percentage of infected cells reached 15% in infertile patients and 5% in healthy donors, while the mean value in both groups was found to be 1.5%.
There is no direct data concerning the correlation of HCMV infection of human spermatozoa and miscarriages and fetal maldevelopment. The results obtained in animal experiments are controversial. According to Neighbour et al. mouse CMV produced no effect on fertilization and embryogenesis in mice . At the same time inhibition of blastocyst formation after infection of two-cell embryos with mouse CMV was observed . There is evidence that herpes virus infection of males plays a role in fetal loss in goats . Statistical analysis has been used to evaluate the role of herpes viruses in human reproduction. The frequency of herpes simplex virus detection in sperm samples of partners of women with repeated miscarriages was higher than in the control (p < 0.05) . A correlation between the presence of herpes viruses in ejaculate and negative outcome of pregnancy can be regarded as an indirect evidence for a vertical herpes virus transmission and associated pregnancy loss. The percentage of gametes carrying HCMV may serve as a criterion for estimation of the risk of vertical transmission of infection.
The ability of the virus to replicate in male germ cells was confirmed in the second part of the study using testis organotypic culture. Intensive viral accumulation occurred in the testicular interstitium, especially in fibroblasts where HCMV was detected starting from the Day 4 of infection. On Day 8, viral antigens were identified in spermatogonia and spermatocytes, and on Day 14 - in spermatozoa. Infection of germ cells was confirmed by electron microscopy.
Data obtained supposes that the presence of HCMV markers in the mature spermatozoa, which was demonstrated both in organotypic culture and in sperm samples, is a consequence of the precursor immature germ cells infection. In vivo it takes 14 days for the round spermatid differentiation into the spermatozoon , while in vitro this period was found to be much shorter [21, 22]. These findings suggest that the presence of HCMV in spermatozoa at late stages of cultivation was due to differentiation of infected spermatids which had been already detected on the Day 4 of infection.
The association between HCMV infection and male infertility is discussed. In this work no difference between infertile and healthy men was found neither in the frequency of HCMV identification in sperm nor in the number of infected gametes. Routine semen analysis revealed no significant differences between infected and virus-free samples in concordance with previous reports [7, 12]. Nevertheless quantitative karyological analysis demonstrated a decrease in the number of spermatids in sperm with simultaneous increase in number of unidentified/degenerated germ cells. These data correspond to the results of Moustafa et al. that the number of apoptotic cells is greater in sperm of infertile men in comparison with that of healthy donors . Our results are also consistent with those of Wu et al. demonstrating an increase in number of apoptotic immature germ cells with chromatin pycnosis and vacuolation, damaged nuclear membrane, and apoptotic bodies in HCMV-infected semen samples .
Cultivation of testis explants in vitro allows one to examine the effects of various factors on spermatogenesis for at least two weeks. At the beginning of the second week post infection the following signs of viral replication were observed: the increase in viral DNA load and HCMV infectious activity with the spread of infection foci in the explants. The number of IGC decreased during the second week in vitro. This finding indicates that HCMV produces a specific lytic effect on germ cells at different stages of development, i.e., on spermatogonia, spermatocytes and spermatids.
The safety of spermatozoa population in infected culture raises the question of why HCMV has a deleterious effect on developing germ cells but not on mature cells. One of the possible explanations for such a difference is abortive HCMV infection of spermatozoa. This suggestion is supported by the fact that only empty capsids without electron-dense core (type A and type B) have been detected in mature sperm cells . Our group and other researchers failed to identify filled capsids (type C) and enveloped virions into spermatozoa. By contrast, infected IGC contain all types of viral particles (Figure 2). A considerable loss of germ cells in an infected testis organotypic culture (Table 4) points to a lytic type of HCMV-infection in IGC. Current knowledge does not allow us to characterize exactly molecular mechanisms responsible for blocking HCMV morphogenesis in spermatozoa. One can suggest that the abortive nature of the infection is determined by the events occurring in a maturing gamete: 1) hypercondensation of chromatin with switching off majority of genes, including those that are necessary for viral replication; 2) loss of the cytoplasm with considerable part of replication machinery; 3) impaired nucleus-cytoplasm transport due to nuclear pore complex modification . In sperm samples HCMV-infection of IGC resulted in decrease of spermatids and in increase of degenerative germ cells. At the same time neither concentration, nor sperm motility and morphology were found to be affected in infected sperm samples. We may suggest that in vivo the number of uninfected IGC is enough for producing a quantity of spermatozoa sufficient for fertilization. Moreover it should be noted that the major parameters of semen are highly variable in a population  and on the other hand, the frequency of HCMV detection and viral load in sperm is rather low. It means that a large group of patients would be required to reveal the HCMV effects on male fertility.
HCMV was found in male germ cells both in sperm samples and in testis organotypic culture infected in vitro. Data obtained suppose that HCMV infects immature germ cells that develop to mature HCMV-carrying spermatozoa. The significant decrease in immature germ cells upon viral infection indicates that HCMV produces a direct gametotoxic effect and can contribute in male infertility.
bovine serum albumin
Dulbecco modified Eagle medium
fetal calf serum
human embryo lung fibroblasts
immature germ cells
multiplicity of infection
plaque forming units
positive internal control
rapid cultural method
transmission electron microscopy.
We thank Prof. L'vov D.K. for general support; Gadgieva Z.S. and Chichev E.V. for technical assistance.
- Kapranos N, Petrakou E, Anastasiadou C, Kotronias D: Detection of herpes simplex virus, cytomegalovirus, and Epstein-Barr virus in the semen of men attending an infertility clinic. Fertil Steril. 2003, 79 (Suppl 3): 1566-1570.View ArticlePubMedGoogle Scholar
- Dejucq N, Jegou B: Viruses in the mammalian male genital tract and their effects on the reproductive system. Microbiol Mol Biol Rev. 2001, 65: 208-231. 10.1128/MMBR.65.2.208-231.2001.PubMed CentralView ArticlePubMedGoogle Scholar
- Klimova RR, Chichev EV, Naumenko VA, Gadzhieva ZS, Tsibisov AS, Adieva AA, L'vov DK, Kurilo LF, Shileiko LV, Ostroumova TV, Sorokina TM, Gavrilov IuA, Levchuk TN, Iakovenko SA, Vasil'eva SG, Voznesenskaia IuV, Simonenko Eiu, Kushch AA, Sukhikh GT: Herpes simplex virus and cytomegalovirus in male ejaculate: herpes simplex virus is more frequently encountered in idiopathic infertility and correlates with the reduction in sperm parameters. Vopr virusol. 2010, 55: 27-31.PubMedGoogle Scholar
- Lai YM, Lee JF, Huang HY, Soong YK, Yang FP, Pao CC: The effect of human papillomavirus infection on sperm cell motility. Fertil Steril. 1997, 67: 1152-1155. 10.1016/S0015-0282(97)81454-9.View ArticlePubMedGoogle Scholar
- Bantel-Schaal U, Neumann-Haefelin D, Schleferstein G: Cytomegalovirus is absent from semen of a population of men seeking fertility evaluation. J Infect Dis. 1993, 168: 518-519. 10.1093/infdis/168.2.518.View ArticlePubMedGoogle Scholar
- Levy R, Najioullah F, Keppi B, Thouvenot D, Bosshard S, Lornage J, Lina B, Guerin JF, Aymard M: Detection of cytomegalovirus in semen from a population of men seeking infertiliry evaluation. Fertil Steril. 1997, 68: 820-825. 10.1016/S0015-0282(97)00340-3.View ArticlePubMedGoogle Scholar
- Bezold G, Politch JA, Kiviat NB, Kuypers JM, Wolff H, Anderson DJ: Prevalence of sexually transmissible pathogens in semen from asymptomatic male infertility patients with and without leukocytospermia. Fertil Steril. 2007, 87: 1087-1097. 10.1016/j.fertnstert.2006.08.109.PubMed CentralView ArticlePubMedGoogle Scholar
- Bresson JL, Clavequin MC, Mazeron MC, Mengelle C, Scieux C, Segondy M, Houhou N: Risk of cytomegalovirus transmission by cryopreserved semen: a study of 635 semen samples from 231 donors. Hum Reprod. 2003, 18: 1881-1886. 10.1093/humrep/deg362.View ArticlePubMedGoogle Scholar
- Neofytou E, Sourvinos G, Asmarianaki M, Spandidos DA, Makrigiannakis A: Prevalence of human herpes virus types 1-7 in the semen of men attending an infertility clinic and correlation with semen parameters. Fertil Steril. 2009, 91: 2487-2494. 10.1016/j.fertnstert.2008.03.074.View ArticlePubMedGoogle Scholar
- Lang DJ, Kummer JF, Hartley DP: Cytomegalovirus in semen. Persistence and demonstration in extracellular fluids. N Engl J Med. 1974, 291: 121-123. 10.1056/NEJM197407182910303.View ArticlePubMedGoogle Scholar
- Wu KH, Zhou QK, Huang JH, Lai RQ, Lin FH, Li B, Zhang CB, Zhou WN, Zhu ZP: Infection of cytomegalovirus and herpes simplex virus and morphology of the infected spermatogenic cells in infertile men. Zhonghua Nan Ke Xue. 2007, 13: 1075-1079.PubMedGoogle Scholar
- Eggert-Kruse W, Reuland M, Johannsen W, Strowitzki T, Schlehofer JR: Cytomegalovirus (CMV) infection--Related to male and/or female infertility factors?. Fertil Steril. 2009, 91: 67-82. 10.1016/j.fertnstert.2007.11.014.View ArticlePubMedGoogle Scholar
- Pallier C, Tebourbi L, Chopineau-Proust S, Schoevaert D, Nordmann P, Testart J, Courtot AM: Herpesvirus, cytomegalovirus, human sperm and assisted fertilization. Hum Reprod. 2002, 17: 1281-1287. 10.1093/humrep/17.5.1281.View ArticlePubMedGoogle Scholar
- Bocharova EN, Kurilo LF, Shileiko LV, Bragina EE, Iurov YuB, Vorsanova SG, Iurov Iyu, Klimova RR, Kuchsh AA: Analysis of germ cell populations in ejaculate of men infected with herpes simplex virus. Ontogenez. 2008, 39: 47-57.PubMedGoogle Scholar
- Baskar JF, Furnari B, Huang ES: Demonstration of developmental anomalies in mouse fetuses by transfer of murine cytomegalovirus DNA-injected eggs to surrogate mothers. J Infect Dis. 1993, 167: 1288-1295. 10.1093/infdis/167.6.1288.View ArticlePubMedGoogle Scholar
- Neighbour PA, Fraser LR: Murine cytomegalovirus and fertility: potentional sexual transmission and effect of this virus on fertilization in vitro. Fertil Steril. 1978, 30: 216-222.PubMedGoogle Scholar
- Heggie AD, Gaddis L: Effects of viral exposure of the two-cell mouse embryo on cleavage and blastocyst formation in vitro. Pediatr Res. 1979, 13: 937-941.View ArticlePubMedGoogle Scholar
- Uzal FA, Woods L, Stillian M, Nordhausen R, Read DH, Van Campen H, Odani J, Hietala S, Hurley EJ, Vickers ML, Gard SM: Abortion and ulcerative posthitis associated with caprine herpesvirus-1 infection in goats in California. J Vet Diagn Invest. 2004, 16: 478-484. 10.1177/104063870401600523.View ArticlePubMedGoogle Scholar
- Bocharova EN, Zavalishina LE, Bragina EE, Klimova RR, Gusak YK, Kurilo LF, Shileiko LV, Petrov AN, Frank GA, Kushch AA: Detection of herpes simplex virus genomic DNA in spermatozoa of patients with fertility disorders by in situ hybridization. Dokl Biol Sci. 2007, 412: 82-86. 10.1134/S0012496607010279.View ArticlePubMedGoogle Scholar
- Heller CG, Clermont Y: Kinetics of the germinal epithelium in man. Recent Progr Horm Res. 1964, 20: 545-575.PubMedGoogle Scholar
- Cremades N, Bernabeu R, Barros A, Sousa M: In vitro maturation of round spermatids using coculture on Vero cells. Hum Reprod. 1999, 14: 1287-1293. 10.1093/humrep/14.5.1287.View ArticlePubMedGoogle Scholar
- Tesarik J, Greco E, Rienzi L, Ubaldi F, Guido M, Cohen-Bacrie P, Mendoza C: Differentiation of spermatogenic cells during in vitro culture of testicular biopsy samples from patients with obstructive azoospermia: effect of recombinant follicle stimulating hormone. Hum Reprod. 1998, 13: 2772-2781.View ArticlePubMedGoogle Scholar
- Moustafa MH, Sharma RK, Thornton J, Mascha E, Abdel-Hafez MA, Thomas AJ, Agarwal A: Relationship between ROS production, apoptosis and DNA denaturation in spermatozoa from patients examined for infertility. Hum Reprod. 2004, 19: 129-138. 10.1093/humrep/deh024.View ArticlePubMedGoogle Scholar
- Bocharova EN, Abdumalikov RA, Bragina EE, Klimova RR, Adueva SM, Medzhidova MG, Kurilo LF, Kushch AA: Determination of the proteins and capsids of herpes simplex virus in human spermatozoa. Dokl Biol Sci. 2003, 391: 379-383. 10.1023/A:1025179307236.View ArticlePubMedGoogle Scholar
- Hermo L, Pelletier R-M, Cyr DG, Smith CE: Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 4: intercellular bridges, mitochondria, nuclear envelope, apoptosis, ubiquitination, membrane/voltage-gated channels, methylation/acetylation, and transcription factors. Microsc Res Tech. 2010, 73 (4): 364-408.View ArticlePubMedGoogle Scholar
- Keel BA: Within- and between-subject variation in semen parameters in infertile men and normal semen donors. Fertil Steril. 2006, 85: 128-134. 10.1016/j.fertnstert.2005.06.048.View ArticlePubMedGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.