The Reproductive Organs of the Female Plains Viscacha, Lagostomus Maximus

Weir, Barbara J.

doi:10.1530/jrf.0.0250365

Cited by 98 publications

(82 citation statements)

References 8 publications

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“…In addition, histological tests confirmed the results found in vaginal exfoliative cytology. The histological analysis showed cell proliferation and cornification more pronounced in proestrus and estrus, as found in Cavia porcellus (Stockard & Papanicolaou 1917) and Lagostomus maximus (Weir 1971). In this sense Deanesly (1966) showed that estradiol and sometimes small amount of androstenedione combined with estradiol stimulated cell proliferation.…”

Section: Discussionmentioning

confidence: 65%

“…Galea spixii showed formation of the vaginal closure membrane, which can also be found in other rodents, as Thryonomys swinderianus (Addo et al 2007), Lagostomus maximus (Weir 1971), Galea musteloides and Cavia aperea (Touma et al 2001), Octodon degus (Mahoney et al 2011), Cavia porcellus (Selle 1922, Lilley et al 1997 and Rattus norvegicus (Lephart et al 1989). Lephart et al (1987), Addo et al (2007) and Mahoney et al (2011) described that the first rupture of the vaginal closure membrane is positively correlated with the onset of puberty in the studied species.…”

Section: Discussionmentioning

confidence: 65%

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Characterization of the estrous cycle in Galea spixii(Wagler, 1831)

et al. 2015

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RESUMO.-[Caracterização do ciclo estral de Galea spixii (Wagler, 1831).]Os Galea spixii habitam a vegetação semiá-rida da Caatinga, no Nordeste brasileiro. Eles são criados em cativeiro para realização de pesquisas relacionadas a biologia da reprodução. Sendo assim, o objetivo deste trabalho foi caracterizar o ciclo estral de G. spixii para obtenção de informações que melhorem o conhecimento do manejo reprodutivo da espécie em cativeiro. O ciclo estral foi monitorado por citologia esfoliativa vaginal em doze fêmeas adultas. Após a detecção de dois ciclos completos em cada animal, os mesmos foram eutanasiados. Em seguida foi realizado estudo histológico do epitélio vaginal com três fêmeas em cada fase do ciclo estral; cinco foram pareadas com machos para realização do grupo controle e outras três fêmeas foram utilizadas para monitorar a formação e ruptura da membrana de oclusão vaginal. Através de citologia esfoliativa vaginal, constatou-se predomínio de células superficiais em estro, células intermediárias grandes em proestro, células intermediárias pequenas e células parabasais com presença de neutrófilos em diestro e metaestro, respectivamente. O es- The Galea spixii inhabits semiarid vegetation of Caatinga in the Brazilian Northeast. They are bred in captivity for the development of researches on the biology of reproduction. Therefore, the aim of this study is characterize the estrous cycle of G. spixii, in order to provide information to a better knowledge of captive breeding of the species. The estrous cycle was monitored by vaginal exfoliative cytology in 12 adult females. After the detection of two complete cycles in each animal, the same were euthanized. Then, histological study of the vaginal epithelium, with three females in each phase of the estrous cycle was performed; five were paired with males for performing the control group for estrous cycle phases, and three other were used to monitor the formation and rupture of vaginal closure membrane. By vaginal exfoliative cytology, predominance of superficial cells in estrus, large intermediate cells in proestrus, intermediate and parabasal cells, with neutrophils, in diestrus and metestrus respectively was found. Estrus was detected by the presence of spermatozoa in the control group. By histology, greater proliferation of the vaginal epithelium in proestrus was observed. We conclude that the estrous cycle of G. spixii lasts 15.8 ± 1.4 days and that the vaginal closure membrane develops until complete occlusion of the vaginal ostium, breaking after few days. Future studies may reveal the importance of this fact for the reproductive success of this animal. INDEX TERMS: Galea spixii, cavies, female, preservation, reproduction, rodents. Characterization of the estrous cycle in

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Section: Discussionmentioning

confidence: 65%

Section: Discussionmentioning

confidence: 65%

Characterization of the estrous cycle in Galea spixii(Wagler, 1831)

et al. 2015

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“…Females exhibit the highest rate of ovulation recorded for a mammal, releasing up to 800 oocytes at each oestrus cycle (Weir 1971a). Massive polyovulation has been explained to occur as a consequence of the peculiar anatomy of the ovary characterised by a highly convoluted cortex that goes deeply into the medulla, substantially increasing the surface area for ovulation (Weir 1971b, Mossman & Duke 1973, Flamini et al 2009. In addition to the increased ovulation area, we observed sustained expression of apoptosis-inhibiting BCL2 gene and low expression of apoptosis-inducing BAX gene, which may be responsible for suppressing apoptosisdependent follicular atresia in the ovary of the adult female (Jensen et al 2006).…”

Section: Introductionmentioning

confidence: 66%

Quantification of healthy and atretic germ cells and follicles in the developing and post-natal ovary of the South American plains vizcacha, Lagostomus maximus: evidence of continuous rise of the germinal reserve

et al. 2014

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The female germ line in mammals is subjected to massive cell death that eliminates 60–85% of the germinal reserve by birth and continues from birth to adulthood until the exhaustion of the germinal pool. Germ cell demise occurs mainly through apoptosis by means of a biased expression in favour of pro-apoptotic members of theBCL2gene family. By contrast, the South American plains vizcacha,Lagostomus maximus, exhibits sustained expression of the anti-apoptoticBCL2gene throughout gestation and a low incidence of germ cell apoptosis. This led to the proposal that, in the absence of death mechanisms other than apoptosis, the female germ line should increase continuously from foetal life until after birth. In this study, we quantified all healthy germ cells and follicles in the ovaries ofL. maximusfrom early foetal life to day 60 after birth using unbiased stereological methods and detected apoptosis by labelling with TUNEL assay. The healthy germ cell population increased continuously from early-developing ovary reaching a 50 times higher population number by the end of gestation. TUNEL-positive germ cells were <0.5% of the germ cell number, except at mid-gestation (3.62%). Mitotic proliferation, entrance into prophase I stage and primordial follicle formation occurred as overlapping processes from early pregnancy to birth. Germ cell number remained constant in early post-natal life, but a remnant population of non-follicular VASA- and PCNA-positive germ cells still persisted at post-natal day 60.L. maximusis the first mammal so far described in which female germ line develops in the absence of constitutive massive germ cell elimination.Free Spanish abstractSpanish translation of this abstract is freely available athttp://www.reproduction-online.org/content/147/2/199/suppl/DC1

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“…In most mammals, the production of oocytes in each reproductive cycle is adjusted to litter size, so ovulation rates correlate well with the number of embryos gestated to term. However, some mammals have been found to display natural polyovulation (Van der Horst & Gillman 1941, Tripp 1971, Weir 1971a,b, Nicoll & Racey 1985. These animals produce a large number of oocytes in each cycle, widely exceeding the effective number of gestated embryos and litter size at birth.…”

Section: Introductionmentioning

confidence: 99%

Naturally suppressed apoptosis prevents follicular atresia and oocyte reserve decline in the adult ovary of Lagostomus maximus (Rodentia, Caviomorpha)

Jensen

Willis²,

Albamonte³

et al. 2006

Reproduction

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It has been widely accepted that mammalian females are born with a non-renewing, finite pool of oocytes that will be continuously cleared by atresia, with only a small proportion of them reaching ovulation. Apoptosis regulates this mass germ cell death, especially through the balance between pro-and anti-apoptotic proteins encoded by the BCL-2 gene family. The caviomorph rodent Lagostomus maximus, the South American plains viscacha, displays the highest ovulation rate known for a mammal releasing 400-800 eggs per cycle. We tested the hypothesis that in L. maximus massive polyovulation is a consequence of reduced apoptosis resulting in suppressed follicular atresia. We found that anti-apoptotic BCL-2 gene is markedly expressed in all kind of follicles from primordial to fully mature antral stages in the adult ovary of L. maximus. On the other hand, pro-apoptotic BAX gene showed weak signals or was undetectable by immunohistochemical examination. Western blot against both proteins confirmed immunohistochemical results. Screening for DNA fragmentation by TUNEL assay was conspicuously negative in ovaries from both pregnant and non-pregnant females. In addition, a-oestrogen receptor also showed an enhanced expression from primordial stage to fully mature antral follicles. Our results show that natural preferential expression of BCL-2 and restricted BAX expression greatly suppresses apoptosis in the ovary of L. maximus. This prevents the decline of the oocyte reserve by abolishing follicular atresia and enables the highest ovulation rate known for a mammal, 400-800 or more eggs per cycle.

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The Reproductive Organs of the Female Plains Viscacha, Lagostomus Maximus

Cited by 98 publications

References 8 publications

Characterization of the estrous cycle in Galea spixii(Wagler, 1831)

Characterization of the estrous cycle in Galea spixii(Wagler, 1831)

Quantification of healthy and atretic germ cells and follicles in the developing and post-natal ovary of the South American plains vizcacha, Lagostomus maximus: evidence of continuous rise of the germinal reserve

Naturally suppressed apoptosis prevents follicular atresia and oocyte reserve decline in the adult ovary of Lagostomus maximus (Rodentia, Caviomorpha)

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