| 1. |
- A Hulten, Maj, et al.
(författare)
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On the origin of the maternal age effect in trisomy 21 Down syndrome: the Oocyte Mosaicism Selection model
- 2010
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Ingår i: Reproduction. - 1470-1626 .- 1476-3990. ; 139:1, s. 1-9
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Forskningsöversikt (refereegranskat)abstract
- We have recently documented that trisomy 21 mosaicism is common in human foetal ovaries. On the basis of this observation we propose that the maternal age effect in Down syndrome (DS) is caused by the differential behaviour of trisomy 21 in relation to disomy 21 oocytes during development from foetal life until ovulation in adulthood. in particular, we suggest that trisomy 21 oocytes, lagging behind those that are disomic, may escape the timed pruning of the seven million in foetal life to the 300-400 finally selected for ovulation. The net effect of this preferential elimination will be an accumulation of trisomy 21 oocytes in the ovarian reserve of older women. We here highlight the implications of this Oocyte Mosaicism Selection (OMS) model with respect to the prevalent view that the maternal age effect is complex, dependent on many different biological and environmental factors. We examine conclusions drawn from recent large-scale studies in families, tracing DNA markers along the length of chromosome 21q between parents and DS children, in comparison to the OMS model. We conclude that these family linkage data are equally compatible with the maternal age effect originating from the accumulation of trisomy 21 oocytes with advancing maternal age. One relatively straightforward way to get to grips with what is actually going on in this regard would be to compare incidence of trisomy 21 oocytes (and their pairing configurations) in foetal ovaries with that in oocytes at the meiosis I stage from adult women.
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| 2. |
- Belen Poretti, Maria, et al.
(författare)
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Reproductive performance of male mice after hypothalamic ghrelin administration
- 2018
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Ingår i: Reproduction. - : BIOSCIENTIFICA LTD. - 1470-1626 .- 1476-3990. ; 156:2, s. 121-132
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Tidskriftsartikel (refereegranskat)abstract
- It has been demonstrated that food intake and reproductive physiology are both simultaneously modulated to optimize reproductive success under fluctuating metabolic conditions. Ghrelin (GHRL) is an orexigenic peptide identified as the endogenous ligand of the growth hormone secretagogue receptor that is being investigated for its potential role on reproduction. Considering that data available so far are still limited and characterization of GHRL action mechanism on the reproductive system has not been fully elucidated, we studied the participation of hypothalamus in GHRL effects on sperm functional activity, plasma levels of gonadotropins and histological morphology in mice testes after hypothalamic infusion of 0.3 or 3.0 nmol/day GHRL or artificial cerebrospinal fluid (ACSF) at different treatment periods. We found that GHRL 3.0 nmol/day administration for 42 days significantly reduced sperm concentration (GHRL 3.0 nmol/day =14.05 +/- 2.44 x 10(6)/mL vs ACSF =20.33 +/- 1.35 x10(6)/mL, P< 0.05) and motility (GHRL 3.0 nmol/day =59.40 +/- 4.20% vs ACSF =75.80 +/- 1.40%, P< 0.05). In addition, histological studies showed a significant decrease percentage of spermatogonia (GHRL 3.0 nmol/day =6.76 +/- 0.68% vs ACSF =9.56 +/- 0.41%, P< 0.05) and sperm (GHRL 3.0 nmol/day =24.24 +/- 1.92% vs ACSF =31.20 +/- 3.06%, P< 0.05). These results were associated with a significant reduction in luteinizing hormone and testosterone plasma levels (P < 0.05). As GHRL is an orexigenic peptide, body weight and food intake were measured. Results showed that GHRL increases both parameters; however, the effect did not last beyond the first week of treatment. Results presented in this work confirm that central GHRL administration impairs spermatogenesis and suggest that this effect is mediated by inhibition of hypothalamic-pituitary-gonadal axis.
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| 3. |
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| 4. |
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| 5. |
- Bertram, Michael, et al.
(författare)
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Reproduction in a polluted world: implications for wildlife
- 2020
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Ingår i: Reproduction. - 1470-1626 .- 1741-7899. ; 160, s. R13–R23-
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Forskningsöversikt (refereegranskat)abstract
- Environmental pollution is an increasing problem for wildlife globally. Animals are confronted with many different forms of pollution, including chemicals, light, noise, and heat, and these can disrupt critical biological processes such as reproduction. Impacts on reproductive processes can dramatically reduce the number and quality of offspring produced by exposed individuals, and this can have further repercussions on the ecology and evolution of affected populations. Here, we illustrate how environmental pollutants can affect various components of reproduction in wildlife, including direct impacts on reproductive physiology and development, consequences for gamete quality and function, as well as effects on sexual communication, sexual selection, and parental care. We follow with a discussion of the broader ecological and evolutionary consequences of these effects on reproduction and suggest future directions that may enable us to better understand and address the effects of environmental pollution.
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| 6. |
- Bourlev, Vladimir, et al.
(författare)
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The relationship between microvessel density, proliferative activity and expression of vascular endothelial growth factor-A and its receptors in eutopic endometrium and endometriotic lesions
- 2006
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Ingår i: Reproduction. - : Bioscientifica. - 1470-1626 .- 1476-3990 .- 1741-7899. ; 132:3, s. 501-509
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Tidskriftsartikel (refereegranskat)abstract
- Studies were performed to elucidate the possible relationship between microvessel density, proliferative activity and angiogenesis in eutopic endometrium from women with and without endometriosis and peritoneal endometriotic lesions. The question whether changes in these parameters in endometriotic lesions were reflected by the level of vascular endothelial growth factor-A (VEGF-A) in serum and peritonea fluid was also studied. Biopsy specimens of both eutopic endometrium and peritoneal endometriotic lesions from women with endometriosis (n=25) as well as eutopic endometrium from women without endometriosis (n=14) were analysed immunohistochemically regarding microvessel density, proliferative activity, and expression of VEGF-A and its receptors vascular endothelial growth factor receptors 1 and 2 (VEGFR-1 and VEGFR-2) in stroma, glands and blood vessels. The VEGF-A concentration was measured in peritoneal fluid and serum. Secretory phase eutopic endometrium from women with endometriosis had significantly higher microvessel density, expression of VEGF-A in glandular epithelium and VEGFR-2 in endometrial blood vessels than those from women without endometriosis. Endometriotic lesions with high proliferative activity had a higher microvessel density and showed higher vascular expression of VEGFR-2 as well as being accompanied by higher levels of VEGF-A in peritoneal fluid and serum, compared with lesions with low proliferative activity. In conclusion, there seems to be a dysregulation of angiogenic activity in the eutopic endometrium of women with endometriosis and endometriotic lesions with high proliferative activity were accompanied by higher local angiogenic activity and higher levels of VEGF in serum and peritoneal fluid.
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| 7. |
- Carlsson, IB, et al.
(författare)
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Kit ligand and c-Kit are expressed during early human ovarian follicular development and their interaction is required for the survival of follicles in long-term culture
- 2006
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Ingår i: Reproduction (Cambridge, England). - : Bioscientifica. - 1470-1626 .- 1741-7899. ; 131:4, s. 641-649
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Tidskriftsartikel (refereegranskat)abstract
- The receptor tyrosine c-Kit and its cognate ligand, c-Kit ligand (KL, stem cell factor, SCF), are involved in ovarian follicular development in several animal species. We studied the expression of KL and c-Kit usingin situhybridization and immunohistochemistry in donated human ovarian cortical tissue. The KL transcripts were expressed in granulosa cells of primary follicles, whereas the expression of c-Kit was confined to the oocyte and granulosa cells in primary and secondary follicles. We employed an ovarian organ culture using firstly serum-containing and then serum-free medium to study the effects of KL and an anti-c-Kit antibody, ACK2, on the development and survival of ovarian folliclesin vitro. Culture of ovarian cortical slices for 7 days resulted in a 37% increase in the number of primary follicles and a 6% increase in secondary follicles. The proportion of viable follicles decreased in all cultures. The addition of KL (1, 10 and 100 ng/ml) into the culture media did not affect the developmental stages of the follicles or the proportion of atretic follicles. Inclusion of ACK2 (800 ng/ml) in the culture medium significantly increased the proportion of atretic follicles on days 7 (49 vs 28% in control cultures) and 14 (62 vs 38%) of culture. In conclusion, c-Kit and KL are expressed in human ovaries during follicular development. Blocking the c-Kit receptor induces follicular atresia. The KL/c-Kit signaling system is likely to control the survival of human ovarian follicles during early follicular development.
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| 8. |
- Cecchini, Katharine, et al.
(författare)
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The transcription factor TCFL5 responds to A-MYB to elaborate the male meiotic program in mice
- 2023
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Ingår i: Reproduction. - 1470-1626 .- 1476-3990. ; 165:2, s. 183-196
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Tidskriftsartikel (refereegranskat)abstract
- In male mice, the transcription factors STRA8 and MEISON initiate meiosis I. We report that STRA8/MEISON activates the transcription factors A-MYB and TCFL5, which together reprogram gene expression after spermatogonia enter into meiosis. TCFL5 promotes the transcription of genes required for meiosis, mRNA turnover, miR-34/449 production, meiotic exit, and spermiogenesis. This transcriptional architecture is conserved in rhesus macaque, suggesting TCFL5 plays a central role in meiosis and spermiogenesis in placental mammals. Tcfl5(em1/em1) mutants are sterile, and spermatogenesis arrests at the mid- or late-pachytene stage of meiosis. Moreover, Tcfl5(+/em1) mutants produce fewer motile sperm.
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| 9. |
- Coward, K., et al.
(författare)
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Phospholipase C zeta, the trigger of egg activation in mammals, is present in a non-mammalian species
- 2005
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Ingår i: Reproduction. - : Bioscientifica. - 1470-1626 .- 1476-3990 .- 1741-7899. ; 130:2, s. 157-163
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Tidskriftsartikel (refereegranskat)abstract
- The activation of the egg to begin development into an embryo is triggered by a sperm-induced increase in intracellular egg Ca2+. There has been much controversy about how the sperm induces this fundamental developmental event, but recent studies suggest that, in mammals, egg activation is triggered by a testis-specific phospholipase C: PLC zeta. Since the discovery of PLC zeta, it has been unclear whether its role in triggering egg activation is common to all vertebrates, or is confined to mammals. Here, we demonstrate for the first time that PLC zeta is present in a non-mammalian vertebrate. Using genomic and cDNA databases, we have identified the cDNA encoding a PLC zeta orthologue in the domestic chicken that, like the mammalian isoforms, is a testis-specific gene. The chicken PLC zeta cDNA is 2152 bp in size and encodes an open reading frame of 639 amino acids. When injected into mouse oocytes, chicken PLC zeta cRNA triggers Ca2+ oscillations, indicating that it has functional properties similar to those of mammalian PLC zeta. Our findings suggest that PLC zeta may have a universal role in triggering egg activation in vertebrates.
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| 10. |
- Gallardo Bolanos, Juan M., et al.
(författare)
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Phosphorylated AKT preserves stallion sperm viability and motility by inhibiting caspases 3 and 7
- 2014
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Ingår i: Reproduction. - : Bioscientifica. - 1470-1626 .- 1476-3990. ; 148:2, s. 221-235
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Tidskriftsartikel (refereegranskat)abstract
- AKT, also referred to as protein kinase B (PKB or RAC), plays a critical role in controlling cell survival and apoptosis. To gain insights into the mechanisms regulating sperm survival after ejaculation, the role of AKT was investigated in stallion spermatozoa using a specific inhibitor and a phosphoflow approach. Stallion spermatozoa were washed and incubated in Biggers-Whitten-Whittingham medium, supplemented with 1% polyvinyl alcohol (PVA) in the presence of 0 (vehicle), 10, 20 or 30 mu M SH5, an AKT inhibitor. SH5 treatment reduced the percentage of sperm displaying AKT phosphorylation, with inhibition reaching a maximum after 1 h of incubation. This decrease in phosphorylation was attributable to either dephosphorylation or suppression of the active phosphorylation pathway. Stallion spermatozoa spontaneously dephosphorylated during in vitro incubation, resulting in a lack of a difference in AKT phosphorylation between the SH5-treated sperm and the control after 4 h of incubation. AKT inhibition decreased the proportion of motile spermatozoa (total and progressive) and the sperm velocity. Similarly, AKT inhibition reduced membrane integrity, leading to increased membrane permeability and reduced the mitochondrial membrane potential concomitantly with activation of caspases 3 and 7. However, the percentage of spermatozoa exhibiting oxidative stress, the production of mitochondrial superoxide radicals, DNA oxidation and DNA fragmentation were not affected by AKT inhibition. It is concluded that AKT maintains the membrane integrity of ejaculated stallion spermatozoa, presumably by inhibiting caspases 3 and 7, which prevents the progression of spermatozoa to an incomplete form of apoptosis.
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