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Biomedical subjects

Peter N Schlegel

Publications and source records attributed to Peter N Schlegel.

At least 19 recordsLinked to original sources
PubMed2006

Identification of polymorphisms and balancing selection in the male infertility candidate gene, ornithine decarboxylase antizyme 3.

BACKGROUND: The antizyme family is a group of small proteins that play a role in cell growth and division by regulating the biosynthesis of polyamines (putrescine, spermidine, spermine). Antizymes regulate polyamine levels primarily through binding ornithine decarboxylase (ODC), an enzyme key to polyamine production, and targeting ODC for destruction by the 26S proteosome. Ornithine decarboxylase antizyme 3 (OAZ3) is a testis-specific antizyme paralog and the only antizyme expressed in the mid to late stages of spermatogenesis. METHODS: To see if mutations in the OAZ3 gene are responsible for some cases of male infertility, we sequenced and evaluated the genomic DNA of 192 infertile men, 48 men of known paternity, and 34 African aborigines from the Mbuti tribe in the Democratic Republic of the Congo. The coding sequence of OAZ3 was further screened for polymorphisms by SSCP analysis in the infertile group and an additional 250 general population controls. Identified polymorphisms in the OAZ3 gene were further subjected to a haplotype analysis using PHASE 2.02 and Arlequin 2.0 software programs. RESULTS: A total of 23 polymorphisms were identified in the promoter, exons or intronic regions of OAZ3. The majority of these fell within a region of less than two kilobases. Two of the polymorphisms, -239 A/G in the promoter and 4280 C/T, a missense polymorphism in exon 5, may show evidence of association with male infertility. Haplotype analysis identified 15 different haplotypes, which can be separated into two divergent clusters. CONCLUSION: Mutations in the OAZ3 gene are not a common cause of male infertility. However, the presence of the two divergent haplotypes at high frequencies in all three of our subsamples (infertile, control, African) suggests that they have been maintained in the genome by balancing selection, which was supported by a test of Tajima's D statistic. Evidence for natural selection in this region implies that these haplotypes may be associated with a trait other than infertility. This trait may be related to another function of OAZ3 or a region in tight linkage disequilibrium to the gene.

Base Sequence↗
PubMed2006

Visualization of GM1 with cholera toxin B in live epididymal versus ejaculated bull, mouse, and human spermatozoa.

The organization of membrane subdomains in mammalian sperm has recently generated controversy, with several reports describing widely differing localization patterns for the ganglioside GM1. Using the pentameric B subunit of cholera toxin (CTB), we found GM1 to be restricted to the plasma membrane overlying the acrosome in the heads of live murine sperm. Interestingly, CTB had minimal binding to live bovine and human sperm. To investigate whether this difference in GM1 localization was because of species differences or differences between collection from the epididymis (mouse) or an ejaculate (bull, human), we examined epididymal bovine and human sperm. We found that GM1 localized to the plasma membrane overlying the acrosome in sperm from these species. To determine whether some component of seminal plasma was interfering with the ability of CTB to access GM1, we incubated epididymal mouse sperm with fluid from murine seminal vesicles and epididymal bull sperm with bovine seminal plasma. This treatment largely abolished the ability of the CTB to bind to GM1, producing a fluorescence pattern similar to that reported for the human. The most abundant seminal plasma protein, PDC-109, was not responsible for this loss. As demonstration that the seminal plasma was not removing GM1, sperm exposed to seminal plasma were fixed before CTB addition, and again displayed fluorescence over the acrosome. These observations reconcile inconsistencies reported for the localization of GM1 in sperm of different species, and provide evidence for the segregation of GM1 to a stable subdomain in the plasma membrane overlying the acrosome.

Animals↗
PubMed2006

Microsurgical inguinal varicocelectomy with and without testicular delivery.

OBJECTIVES: To evaluate the effect of the delivery of testis on semen parameters, serum testosterone, and pregnancy rates after varicocelectomy, performed with and without delivery of the testis. METHODS: A total of 165 patients with clinically diagnosed varicoceles who underwent surgical ligation with (n = 55) or without (n = 110) testicular delivery were included in this study. Patients were followed up postoperatively at 3, 6, and 9 to 24 months. The postoperative outcome was assessed by determination of the semen parameters, testosterone level, varicocele recurrence, and pregnancy rate. RESULTS: No varicocele recurrences were clinically detectable after either surgical approach. The mean increase in motile sperm/ejaculate after varicocelectomy without testicular delivery was significant (P <0.05) for grade II and III varicoceles. When the testis was delivered, the increase was significant only for grade III varicoceles. No statistically significant difference was found in the change in motile sperm/ejaculate between the two cohorts for all three varicocele grades. The overall pregnancy rate was also not significantly different between the two groups. The testosterone levels rose from 323 to 471 ng/dL on average (P <0.05) after varicocelectomy without testicular delivery but did not change in men who had testicular delivery. The change in testosterone level, age, and testicular volume did not correlate with either the increase in semen parameters or the grade of varicocele treated. CONCLUSIONS: The results of our study have shown that varicocelectomy without testicular delivery has equivalent or more beneficial effects on semen parameters without affecting varicocele recurrence rates. Delivery of the testis did not offer any beneficial effects on semen quality or pregnancy rates after varicocelectomy.

Follow-Up Studies↗
PubMed2006

Efficacy and safety of histrelin subdermal implant in patients with advanced prostate cancer.

PURPOSE: This open label, multicenter study was done to evaluate the efficacy and safety of the gonadotropin hormone-releasing hormone agonist histrelin acetate administered as a 50 mg subdermal implant in men with advanced prostatic cancer. MATERIALS AND METHODS: The 3 cm x 3.5 mm histrelin implant was surgically inserted in the inner aspect of the upper nondominant arm of eligible patients under local anesthesia. Patients were evaluated weekly for the first 2 weeks after implant insertion and monthly thereafter. At week 52 the implant was removed and in most cases a new implant was inserted. Patient observation for safety and efficacy continued to week 60. Efficacy was determined by the proportion of patients who attained chemical castration (serum testosterone 50 ng/dl or less) at weeks 4 through 52. RESULTS: Of the 134 patients with week 4 testosterone levels available 100% achieved chemical castration. Testosterone suppression was maintained throughout the 52 weeks after implantation in more than 99% of patients. Significant LH and PSA suppression was also observed. By week 16 PSA had decreased an average of 90% from a baseline of 83.6 ng/ml (p = 0.0001). By week 60, 79% of patients had a complete PSA response (p <0.0175). No testosterone or LH surge was observed with reimplantation. Additionally, the implant was safe and well tolerated. CONCLUSIONS: The gonadotropin hormone-releasing hormone agonist histrelin acetate provided in a unique implant delivery device is effective for treating men with advanced prostate cancer, as demonstrated by the suppression of testosterone and LH to castrate levels at 4 weeks and the maintenance of these levels during 52 weeks. PSA, a secondary end point for effectiveness, was also suppressed significantly from baseline.

Adenocarcinoma↗
PubMed2005

SUMO-1, human male germ cell development, and the androgen receptor in the testis of men with normal and abnormal spermatogenesis.

Sumoylation affects multiple cellular events, including chromatin inactivation and transcriptional repression. Our data provide the first characterization of small ubiquitin-related modifier-1 (SUMO-1) expression during human spermatogenesis by the use of high-resolution cellular SUMO-1 bioimaging. During human meiotic prophase, SUMO-1 localizes to sex chromosomes and centromeric and pericentromeric chromatin. As human spermatocytes progress toward the end of prophase in meiosis I, SUMO-1 is no longer detected within the sex body and pericentromeric heterochromatin but localizes exclusively to centromeres. SUMO-1 localization along sex chromosome axes, pseudoautosomal region, and centromeres of both chromosomes supports a role for SUMO-1 sumoylation in epigenetic events occurring over the entire sex body, e.g., meiotic sex chromosome inactivation and chromatin condensation. Centromeric SUMO-1 throughout meiotic prophase suggests a role in centromeric chromatin condensation and/or other centromere/kinetochore functions. SUMO-1 is likely involved in both facultative and constitutive heterochromatin processes in spermatocytes. Haploid round spermatids show a consistent association of SUMO-1 with centromeric clusters. During spermatid elongation, SUMO-1 localizes in the manchette perinuclear ring. Steroidogenic Leydig cells show some cytoplasmic but strong nuclear and perinuclear SUMO-1. Peritubular myoepithelial cell SUMO-1 colocalizes with centromeric heterochromatin. In epithelial Sertoli cells, when associated with centromeric heterochromatin, SUMO-1 is adjacent but not colocalized with the nucleolus. Male germ cells demonstrate no SUMO-1 nucleolar association. Human and rodent Sertoli cells consistently show an inverse correlation between androgen receptor (AR) and SUMO-1 expression and compartmentalization. Sertoli cells from certain infertile patients, however, showed greatly decreased SUMO-1 and AR. Our data suggest that human testicular SUMO-1 has specific functions in heterochromatin organization, meiotic centromere function, and gene expression.

Animals↗
PubMed2005

Success of testicular sperm extraction [corrected] and intracytoplasmic sperm injection in men with Klinefelter syndrome.

PURPOSE: The aim of this study was to report the successful fertility treatment of men with Klinefelter syndrome using testicular sperm extraction (TESE) and intracytoplasmic sperm injection (ICSI). METHODS: A total of 42 men with Klinefelter syndrome who underwent 54 TESE procedures were identified. Before TESE, patients with serum testosterone levels less than 15.6 nmol/liter were treated with an aromatase inhibitor. Sperm retrieval rates and results of ICSI, including fertilization and clinical pregnancy, were collected. RESULTS: Mean pretreatment FSH and testosterone levels were 33.2 IU/liter and 9.8 nmol/liter. During medical therapy, the mean testosterone level rose to 17.0 nmol/liter (P < 0.01). Spermatozoa were found during 39 microdissection TESE procedures, on the day before, or day of oocyte retrieval during a programmed in vitro fertilization cycle. The sperm retrieval rate was 72% (39 of 54) per TESE attempt, and 29 of the 42 different men (69%) had adequate sperm found for ICSI. Thirty-three in vitro fertilization cycles yielded embryos for transfer in the 39 (85%) cycles with sperm retrieved. Eighteen clinical pregnancies have resulted in 21 live births [18 of 39 (46%)]. All children had a normal karyotype. CONCLUSION: TESE/ICSI is a successful intervention for the majority of patients with azoospermia and Klinefelter syndrome. Sperm retrieval and ICSI success in men with Klinefelter syndrome are comparable with other men with nonobstructive azoospermia treated at our center.

Adult↗
PubMed2005

Yet another test of sperm chromatin structure.

Sperm chromatin can affect reproductive performance, and it may be analyzed by measuring susceptibility of DNA to breakage using assays such as the sperm chromatin structure assay, comet assay, TUNEL, and DNA ladders. The newly proposed test, Halosperm, may not provide additional information beyond that obtained with existent evaluations.

Chromatin↗
PubMed2005

Births using sperm retrieved via immediate microdissection of a solitary testis with cancer.

OBJECTIVE: To determine the feasibility of achieving births using sperm retrieved from a solitary testis with cancer. DESIGN: Prospective clinical study of azoospermic men with testis cancer in a solitary testis. SETTING: Infertility patients in an academic environment. PATIENT(S): Azoospermic men with previous history of orchiectomy and testis cancer in a remaining solitary testis. INTERVENTION(S): Viable sperm were retrieved by immediate microdissection of paratumor testicular tissue from orchiectomy specimen. MAIN OUTCOME MEASURE(S): Live births were achieved using sperm from immediate microdissection of orchiectomy specimen with testis cancer. CONCLUSION(S): Azoospermic men with cancer in a solitary testis have potential for fertility.

Adult↗
PubMed2005

Structural and functional changes to the testis after conventional versus microdissection testicular sperm extraction.

OBJECTIVES: To compare, in a retrospective study, the ultrasound findings and hormonal changes after testicular sperm extraction (TESE) using the conventional multiple biopsy approach and the more recent microdissection technique. TESE has been performed using the conventional multiple biopsy approach and the more recent microdissection technique. METHODS: A total of 435 men with nonobstructive azoospermia who had undergone 543 TESE attempts were included in the study. The initial 83 attempts were done using the conventional open technique and the remaining 460 attempts were performed by microdissection. The sperm retrieval rates were compared, as were the complication rates as assessed by ultrasound and endocrinologic evaluations between the two groups. RESULTS: The retrieval rate by the conventional technique was 32% and by microdissection was 57% (P = 0.0002). In patients with hypospermatogenesis, the retrieval rate differed between the two approaches (P = 0.03). Ultrasound findings demonstrated fewer acute and chronic changes in the microdissection group than in the conventional group (P < 0.05). At 3 to 6 months after surgery, the testosterone levels had dropped to 80% of their pre-TESE levels in both groups (P < 0.01). The levels rose back to 85% after 12 months and to 95% after 18 months. The mean follicle-stimulating hormone levels increased from 22 +/- 2 to 30 +/- 3 IU/L (P = 0.02), and the luteinizing hormone levels increased from 12 +/- 2 to 16 +/- 2 IU/L (P = 0.2). CONCLUSIONS: TESE has effects on testicular function, but the microdissection procedure is relatively safer than the conventional technique and improves the sperm retrieval rate significantly in patients with nonobstructive azoospermia.

Adult↗
PubMed2005

Novel mutations in testis-specific ubiquitin protease 26 gene may cause male infertility and hypogonadism.

Patients (n = 188) with non-obstructive azoospermia (NOA), and 17 fertile controls were screened for sequence changes in the ubiquitin specific protease (USP) 26 gene. Semen analysis, hormonal evaluation, and testicular biopsies were performed. DNA was extracted from whole blood. Denaturing high-performance liquid chromatography was used to screen for single nucleotide polymorphisms. Amino acid sequences were determined in samples with mutations. Twenty out of 188 (10.6%) infertile men had amino acid changes in USP26. No changes were found in fertile controls. 1090C-->T substitution and (363insACA; 494T-->C; 1423C-->T) change were found in 3.3 and 1.9% of patients respectively. Serum testosterone concentrations and testicular volume were lower in the mutation positive group compared with the non-mutation group (272 versus 366 ng/dl; P = 0.01) (volume: 7.88 versus 10 ml, P = 0.03). Six out of 28 (21%) patients with Sertoli cell-only syndrome, and two out of 18 (11%) patients with maturation arrest had mutations in the USP26 gene. There were no live deliveries in couples with the USP26+ mutation, and three live deliveries in the group without mutations. The USP26 gene may be of importance in male reproduction. Mutations in this gene may be associated with male infertility, and may negatively affect testicular function.

Adult↗
PubMed2005

Recombination in men with Klinefelter syndrome.

Klinefelter syndrome (KS: 47,XXY), occurs in one in 1000 male births. Men with KS are infertile and have higher rates of aneuploidies in sperm compared with normal fertile men. In the course of analyzing recombination in a population of infertile men, we observed that four men in our study presented with KS. We examined whether these men differed in recombination parameters among themselves and relative to normal men. Even though the number of men with KS analyzed was small, we observed remarkable variation in spermatogenesis. In spite of the fact that the men had the same genetic cause for infertility, two of four KS patients had few or no spermatogenic cells that progressed through meiosis to the pachytene stage, whereas the other two men produced abundant pachytene cells that had recombination frequencies comparable with those of fertile men, although one had a significant reduction in fidelity of synapsis. Moreover, regardless of histological appearance, examination of outcomes of assisted reproduction indicated that sperm were extracted from testis biopsies in all four cases, and when used in assisted reproductive practices chromosomally normal babies were born. These results reinforce that: (i) men with the same underlying genetic cause for infertility do not present with uniform pathology, (ii) the checkpoint machinery that might arrest spermatogenesis in the face of chromosomal abnormalities does not prevent pockets of complete spermatogenesis in men with KS, and (iii) aneuploidy, in some cases, is compatible with birth of a chromosomally normal child, suggesting that sperm produced from a background of aneuploidy can be normal in men with KS.

Case-Control Studies↗
PubMed2004

Defective recombination in infertile men.

Two percent of men are infertile owing to defects in sperm production. In 10-15% of cases, Y chromosome deletions that encompass critical spermatogenesis genes are detected; in the remaining cases, the cause of infertility is unknown. In model organisms, defects in recombination genes cause infertility, germ cell aneuploidy and subsequent development of inviable or abnormal progeny. Several studies have also linked infertility and higher rates of germ cell aneuploidy in men and women. Thus, we reasoned that defective recombination may be a major cause of infertility in men with poor or no sperm production and we performed the first comparison of recombination parameters within populations of single spermatocytes from infertile and fertile men who reported for assisted reproduction. We observed that 10% of non-obstructive azoospermic men had significantly lower recombination frequencies than men with normal spermatogenesis. Furthermore, when we focused our analysis only on those men who had a pathological diagnosis of 'maturation arrest' due to arrest during sperm development, about half had detectable defects in recombination. In contrast, none of the men with normal spermatogenesis had defects in recombination. Thus, this study provides direct evidence that defects in recombination are linked to poor sperm production in a significant percentage of infertile men. Implications of this observation for the use of assisted reproductive technologies are especially relevant to consider, given that recombination is required to both introduce genetic variation and insure proper chromosome separation during meiosis.

Female↗
PubMed2004

AZF microdeletions of the Y chromosome and in vitro fertilization outcome.

OBJECTIVE: To determine whether the presence of a Y microdeletion confers any adverse effects on in vitro fertilization or intracytoplasmic sperm injection (IVF/ICSI) outcome. DESIGN: Retrospective case-control study. SETTING: Academic infertility center. PATIENT(S): A total of 17 patients with Y microdeletions who attempted IVF/ICSI cycles at our center between March 1996 and March 2002 were studied. Study patients were analyzed in two groups: those who underwent testicular sperm extraction (TESE) and those for whom ejaculated sperm was used. INTERVENTION(S): The two patient study groups were matched to controls treated at the same time who had either nonobstructive severe oligozoospermia or azoospermia with normal Y chromosomes. Controls were matched for age of the female partner, sperm concentration, and number of embryos transferred. MAIN OUTCOME MEASURE(S): Fertilization and clinical pregnancy rates. RESULT(S): Sperm was only obtained from patients with azoospermic factor (AZF)c microdeletions (and from one patient with a partial AZFb microdeletion). A trend toward lower fertilization rates in patients with Y microdeletions was noted, which did not reach statistical significance. Clinical pregnancy rates per cycle and per transfer were similar to those for controls. CONCLUSION(S): Patients with AZFc microdeletions seem to have IVF/ICSI outcomes comparable to those of controls with normal Y chromosomes.

Case-Control Studies↗
PubMed2004

Role of varicocelectomy in men with nonobstructive azoospermia.

OBJECTIVE: To evaluate the benefits of varicocelectomy in men with nonobstructive azoospermia. DESIGN: Retrospective review of effect of prior varicocelectomy on sperm retrieval rates in men with nonobstructive azoospermia. Chart review of men with nonobstructive azoospermia who underwent microsurgical varicocelectomy to determine the effect of the procedure on the need for testicular sperm extraction (TESE). SETTING: Tertiary, university-based referral center. PATIENT(S): Men with clinical varicoceles and nonobstructive azoospermia. INTERVENTION(S): Microsurgical varicocelectomy, TESE. MAIN OUTCOME MEASURE(S): Return of sperm to the ejaculate and need for TESE after varicocele repair, ability to find sperm using microdissection TESE. RESULT(S): Of 31 men who underwent varicocele repair at one institution for documented nonobstructive azoospermia, 7/31 (22%) had sperm reported on at least one semen analysis postoperatively. However, only 3/31 (9.6%) men after varicocele repair had adequate motile sperm in the ejaculate for ICSI, without TESE. Sperm retrieval rates for men with varicoceles were not affected by a history of prior varicocelectomy. CONCLUSION(S): Men with clinical varicoceles that are associated with nonobstructive azoospermia will rarely have adequate sperm in the ejaculate after varicocele repair to avoid TESE. A history of prior varicocele repair does not appear to affect the chance of sperm retrieval by TESE for men with clinical varicoceles and nonobstructive azoospermia. The benefits of varicocelectomy in men with nonobstructive azoospermia may be less than previously reported.

Biopsy↗
PubMed2004

Y chromosome assessment and its implications for the development of ICSI children.

The aetiology of compromised spermatogenesis is often genetic in nature. There are only a few reports of father/son cohorts that have been evaluated to assess heritability of mutations associated with male factor infertility and the psychological well-being of the children. In the present study, multiple tissues were sampled from consenting male patients and their sons derived from intracytoplasmic sperm injection (ICSI) and underwent chromosomal and genetic analyses. Paediatric and psychological examinations were also conducted. In 87 men and 47 boys, 22 sequence tagged sites (STS) were analysed by multiplex PCR and deletion breakpoints were defined with additional loci. In one patient, the breakpoints map to the highly unstable palindrome-rich region within AZFb and proximal AZFc was investigated. A total of 86 blood, 26 semen, and 73 cheek cells samples were collected from adults, and 36 blood samples and 44 cheek cell specimens were obtained from the boys. Though all of the fathers had normal karyotypes, the incidence of chromosomal abnormalities in the somatic cells of male progeny was 8.3% (3/36). The incidence of germ line aneuploidy in these men was 0.5-2.8%. A CF mutation (Delta508) was detected in one of 87 men (1.2%) and microdeletions in Yq AZF were detected in 3.4% of 87 adults and in 2.1% of their sons (n = 47). In conclusion, screening for Y chromosome microdeletions provides crucial information in the counselling of couples seeking infertility treatment. Moreover, DNA extraction and Y deletion assessments of cheek cells provide a non-invasive approach. Inheritance of Yq deletions appears not to affect the psychological and physical development of children derived from ICSI.

Adult↗