Publications by authors named "Ben Colenbrander"

The effects of the GnRH vaccine Improvac on testicular and epididymal morphometrics, histology and spermatogenesis were measured in 19 young (15-20 months) colts randomly assigned to one control (saline, castration at 57 days, n = 6) or either of two GnRH vaccine-treatment groups, T-57 (castration at 57 days, n = 7) or T-100 (castration at 100 days, n = 6), respectively. All were immunized on Day 0 with a single booster on Day 28. Excised testes and epididymides were weighed and processed for histology to measure tubule, epithelial and muscle dimensions, the ratio of interstitial tissue to seminiferous tubules and determine the stage of spermatogenesis.

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Intracytoplasmic sperm injection is the technique of choice for equine IVF and, in a research setting, 18-36% of injected oocytes develop to blastocysts. However, blastocyst development in clinical programs is lower, presumably due to a combination of variable oocyte quality (e.g.

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Bull elephants exhibit marked increases in testosterone secretion during musth, and studies have shown a heightened sensitivity of the testis to GnRH-stimulated testosterone production in musth compared to nonmusth males. However, activity of the hypothalamo-pituitary-gonadal axis before or soon after musth has not been studied in detail. The aim of this study was to evaluate LH and testosterone responses to GnRH challenge in nine adult Asian elephant (Elephas maximus) bulls during three periods relative to musth: premusth, postmusth, and nonmusth.

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The swamp type of the Asian water buffalo is assumed to have been domesticated by about 4000 years BP, following the introduction of rice cultivation. Previous localizations of the domestication site were based on mitochondrial DNA (mtDNA) variation within China, accounting only for the maternal lineage. We carried out a comprehensive sampling of China, Taiwan, Vietnam, Laos, Thailand, Nepal and Bangladesh and sequenced the mtDNA Cytochrome b gene and control region and the Y-chromosomal ZFY, SRY and DBY sequences.

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Musth in adult bull elephants is a period of increased androgen concentrations ranging from a few weeks to several months. For captive elephant bull management, musth presents a serious challenge because of the aggressive behavior of musth bulls toward people and other elephants. Commercially available GnRH vaccines have been shown to suppress testicular function by interrupting the hypothalamo-pituitary-gonadal (HPG) axis in many species.

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Advanced maternal age and in vitro embryo production (IVP) predispose to pregnancy loss in horses. We investigated whether mare age and IVP were associated with alterations in mitochondrial (mt) DNA copy number or function that could compromise oocyte and embryo development. Effects of mare age (<12 vs ≥12 years) on mtDNA copy number, ATP content and expression of genes involved in mitochondrial replication (mitochondrial transcription factor (TFAM), mtDNA polymerase γ subunit B (mtPOLB) and mitochondrial single-stranded DNA-binding protein (SSB)), energy production (ATP synthase-coupling factor 6, mitochondrial-like (ATP-synth_F6)) and oxygen free radical scavenging (glutathione peroxidase 3 (GPX3)) were investigated in oocytes before and after in vitro maturation (IVM), and in early embryos.

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Zearalenone (ZEN) is a mycotoxin that can be a contaminant of food and feed commodities. ZEN acts as a xenoestrogen and is considered an endocrine disruptor. Since estrogens influence oogenesis during fetal growth, the effect of ZEN on oocytes was investigated in the F1-generation.

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Background: The aim of this study was to investigate the in vitro effects of the Fusarium fungus-derived mycotoxin, zearalenone and its derivatives alpha-zearalenol and beta-zearalenol on motility parameters and the acrosome reaction of stallion sperm. Since the toxic effects of zearalenone and its derivatives are thought to result from their structural similarity to 17beta-estradiol, 17beta-estradiol was used as a positive control for 'estrogen-like' effects.

Methods: Stallion spermatozoa were exposed in vitro to zearalenone, alpha-zearalenol, beta-zearalenol or 17beta-estradiol at concentrations ranging from 1 pM - 0.

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Background: NANOG is a key player in pluripotency and its expression is restricted to pluripotent cells of the inner cell mass, the epiblast and to primordial germ cells. Spermatogenesis is closely associated with pluripotency, because through this process highly specialized sperm cells are produced that contribute to the formation of totipotent zygotes. Nevertheless, it is unknown if NANOG plays a role in this process.

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In the mammalian ovary, oocytes are arrested at prophase of meiosis I until a hormonal stimulus triggers resumption of meiosis. During the subsequent meiotic maturation process, which includes completion of the first meiotic division and formation of the second metaphase spindle, oocytes acquire competence for fertilization. Recently, it was shown that clathrin, a cytosolic protein complex originally defined for its role in intracellular membrane traffic, is also involved in the stabilization of kinetochore fibers in mitotic spindles of dividing somatic cells.

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This study investigated the role of the leptin system in human oocyte maturation and its prognostic value for IVF outcome. The protein concentrations of leptin and soluble leptin receptor in follicular fluid were determined and the free leptin index (FLI) were established. Additionally, mRNA expression levels of different leptin receptor (ObR) isoforms and of PTX3 and HAS2 in cumulus cells were quantified, mutually compared and analysed relative to FLI, body mass index, age and number of retrieved oocytes.

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Mammalian spermatogonial stem cells are a special type of adult stem cells because they can contribute to the next generation. Knockout studies have indicated a role for TRP53 and PTEN in insulating male germ cells from pluripotency, but the mechanism by which this is achieved is largely unknown. To get more insight in these processes, an RNAi experiment was performed on the mouse spermatogonial stem cell line GSDG1.

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The rapid expansion of mutant mouse colonies for biomedical research has resulted in lack of space at laboratory animal facilities and increasing risks of losing precious lines. These challenges require cheap and effective methods in addition to freezing embryos and sperm to archive the expanding mutant mouse lines. Cryopreservation of mouse ovarian tissue has been reported, but the application in the diverse mutant lines and genetic backgrounds has not yet been studied.

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Cell lines from neonate porcine testis were cultured and characterized and the effect of growth factors were investigated, in order to determine the requirements for the establishment of porcine male germ cell lines. In primary cultures, three different colony types with distinctive morphologies could be recognized. From colonies resembling mouse spermatogonial stem cells (SSCs), two cell lines were derived and maintained for nine passages after which proliferation stopped.

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A unique feature of the reproductive physiology of Asian elephants (Elephas maximus) is the occurrence of two LH surges before ovulation, instead of one. An anovulatory LH (anLH) surge, the function of which is unknown, occurs consistently 3 weeks before the ovulatory LH (ovLH) surge that induces ovulation. Thus, the ability to induce an ovLH surge would be useful for scheduling natural mating or artificial insemination.

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Background: Two bovine species contribute to the Indonesian livestock, zebu (Bos indicus) and banteng (Bos javanicus), respectively. Although male hybrid offspring of these species is not fertile, Indonesian cattle breeds are supposed to be of mixed species origin. However, this has not been documented and is so far only supported by preliminary molecular analysis.

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Background: Mammalian oocytes acquire competence to be fertilized during meiotic maturation. The protein kinase CDC2 plays a pivotal role in several key maturation events, in part through controlled changes in CDC2 localization. Although CDC2 is involved in initiation of maturation, a detailed analysis of CDC2 localization at the onset of maturation is lacking.

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Captive Asian elephant (Elephas maximus) populations are decreasing due to low birth rates compared to wild elephants. Improving oestrous detection in female elephants is required to ensure successful mating in captive and semi-captive herds. Responsive behaviours of eight semi-captive bull elephants to the uro-genital area (genital inspection test) or urinary pheromones (urine test) of 14 female elephants throughout the oestrous cycle were evaluated.

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Frozen-thawed ovarian cortical fragments (1 mm(3)) were autotransplanted to the uterus of completely ovariectomized goats. The grafts developed preovulatory follicles, accompanied by estrous behavior and a rise in plasma E(2) levels, demonstrating successful cryopreservation and transplantation.

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Isolated caprine early-staged follicles were submitted to osmotic tolerance tests in the presence of sucrose, ethylene glycol (EG), or NaCl solutions and were exposed to and cryopreserved (by slow or rapid cooling) in MEM alone or MEM supplemented with sucrose, EG (1.0 or 4.0 M), or both.

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Two lineage segregation events in mammalian development form the trophectoderm, primitive endoderm, and pluripotent primitive ectoderm. In mouse embryos, Oct4, Cdx2, Nanog, and Gata6 govern these events, but it is unknown whether this is conserved between mammals. Here, the expression patterns of these genes and their products were determined in porcine oocytes and embryos and in bovine embryos.

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The micro-opioid receptor (MOR) was identified in equine oocytes, cumulus and granulosa cells. By RT-PCR, a 441bp fragment was observed. By immunoblotting, a 65 kDa band was detected in samples of winter anestrous whereas in cells recovered in breeding season, two bands, 65 and 50 kDa, were found.

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In this study, the mechanisms of supposed leptin action on oocyte maturation were examined. Expression of leptin mRNA, as determined with RT-PCR, was present in oocytes but not in cumulus cells. The long isoform of the leptin receptor (ObR-L) was expressed exclusively in cumulus cells after 7 and 23 hr of maturation.

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Fungi of the Fusarium species can infect food and feed commodities and produce the mycotoxins zearalenone (ZEA) and deoxynivalenol (DON). Since both toxins have been reported to reduce fertility, the mechanisms of ZEA and DON on inhibition of oocyte maturation were examined. Pig oocytes were matured in the presence of ZEA (a mycotoxin with estrogenlike activity), 17beta-estradiol, and DON (all 3.

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Transplantation of ovarian tissue has high potential for female gamete conservation. However, optimal timing of oocyte recovery for in vitro maturation and fertilization is still critical. Therefore the aim of the present study was to use high-resolution transcutaneous ultrasonography to monitor follicular development within xenografted ovarian tissue.

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