scholarly journals Parturition and perfect prematurity: birth in marsupials

2006 ◽  
Vol 54 (3) ◽  
pp. 139 ◽  
Author(s):  
Geoff Shaw ◽  
Marilyn B. Renfree
Keyword(s):  
Reproductive Tract ◽  
Tammar Wallaby ◽  
Experimental Manipulation ◽  
Lung Maturation ◽  
Plasma Progesterone ◽  
Macropus Eugenii ◽  
Surfactant Production ◽  
Glucocorticoid Production ◽  
The Brain ◽  
Adrenal Glucocorticoid

Marsupials are distinguished from eutherian mammals in their mode of reproduction. They give birth to a highly altricial young, which completes its development whilst attached to a teat, usually within a pouch. The marsupial neonate has relatively well-developed digestive, respiratory and circulatory systems but retains its fetal excretory system with a fully functional mesonephric kidney and undifferentiated gonads and genitalia. We have investigated birth in the tammar wallaby (Macropus eugenii) and shown that the tiny (400 mg) fetus determines the time of its own delivery. Although plasma progesterone falls, and oestradiol associated with the postpartum oestrus typically rises, around the time of parturition, neither hormone is essential for the timing of birth. However relaxin may loosen the connective tissue of the cervix and vaginae for birth. Labour starts suddenly and is completed within minutes. Both prostaglandins and mesotocin are essential for the contractions that deliver the young. Prostaglandins from the reproductive tract act via the brain to control parturient behaviour. In the last 2 days of gestation fetal adrenal glucocorticoid production increases, promoting lung maturation and surfactant production and ultimately triggering labour. The accessibility of the altricial neonatal marsupial provides a unique opportunity for experimental manipulation of organ development and maturation.

Effects of bromocriptine at parturition in the tammar wallaby, Macropus eugenii

1990 ◽  
Vol 2 (1) ◽  
pp. 79 ◽  
Author(s):  
TP Fletcher ◽  
G Shaw ◽  
MB Renfree
Keyword(s):  
Post Partum ◽  
Tammar Wallaby ◽  
Plasma Prolactin ◽  
Plasma Progesterone ◽  
Macropus Eugenii ◽  
Sequence Of Events ◽  
Prostaglandin Release ◽  
Peripartum Period ◽  
And Control ◽  
Subsequent Onset

Female tammar wallabies were treated with the dopamine agonist bromocriptine at the end of pregnancy to suppress the peripartum pulse of plasma prolactin. The animals were subsequently observed, and a series of blood samples taken to define the hormonal profiles before and immediately after parturition. Birth was observed in 4/5 control animals and occurred in 8/9 bromocriptine-treated animals. The peripartum peak in plasma PGFM concentrations was not affected by bromocriptine although the pulse of prolactin normally seen at parturition was completely abolished. The timing of luteolysis was apparently unaffected, as plasma progesterone concentrations fell similarly in both treated and control animals immediately after parturition. However, all of the neonates of the bromocriptine-treated animals died within 24 h, possibly because of a failure to establish lactation. Subsequent onset of post-partum oestrus was delayed or absent both in control and in bromocriptine-treated animals, suggesting that the frequent blood sampling and disturbances in the peripartum period interfered with these endocrine processes. It is concluded that both prolactin and prostaglandin can induce luteolysis in the pregnant wallaby, but that the normal sequence of events results from a signal of fetal origin inducing a prostaglandin release from the uterus, which in turn releases a pulse of prolactin that induces a progesterone decline.

scholarly journals Influence of donor age on development of gonadal tissue from pouch young of the tammar wallaby, Macropus eugenii, after cryopreservation and xenografting into mice

Reproduction ◽  
2002 ◽  
pp. 143-153 ◽  
Author(s):  
D Mattiske ◽  
G Shaw ◽  
JM Shaw
Keyword(s):  
Reproductive Tract ◽  
Follicular Development ◽  
Tammar Wallaby ◽  
Corpora Lutea ◽  
Follicle Development ◽  
Primordial Follicles ◽  
Antral Follicles ◽  
Macropus Eugenii ◽  
Reduced Rate ◽  
Timing Of Onset

Ovaries from a marsupial, the tammar wallaby (Macropus eugenii), were grafted into a eutherian recipient at known stages of development to ascertain whether normal development would occur. Xenografted ovaries from pouch young < 20 days old, before the onset of meiosis, retained few germ cells and developed tubule-like structures reminiscent of seminiferous cords. Ovaries from 50-day-old pouch young, which contain primordial follicles, developed into antral follicles and corpora lutea within the eutherian host, and produced hormones that stimulated the reproductive tract of the host. The timing of onset of antrum formation and the progress of follicle development were advanced relative to the timing of events in ovaries in situ. Frozen-thawed ovaries from 50-day-old donors developed into preantral follicles, but at a reduced rate and number. This finding shows that gonads of a marsupial species can develop as xenografts in a eutherian, forming large antral follicles. Accelerated follicular development in xenografts provides a potentially valuable model for studying the factors that control follicle development. Assisted reproduction of endangered marsupials may also be feasible using follicles from pouch young grown as xenografts in a eutherian host.

scholarly journals 198 DISTRIBUTION OF SPERMATOZOA AND COPULATORY PLUG IN RELATION TO THE TIME OF MATING AND OVULATION IN THE FEMALE TAMMAR WALLABY (MACROPUS EUGENII)

2005 ◽  
Vol 17 (2) ◽  
pp. 249
Author(s):  
D.B.B.P. Paris ◽  
D.A. Taggart ◽  
M.C.J. Paris ◽  
P.D. Temple-Smith ◽  
M.B. Renfree
Keyword(s):  
Reproductive Tract ◽  
Tammar Wallaby ◽  
Gravid Uterus ◽  
Limited Sample ◽  
Macropus Eugenii ◽  
Copulatory Plug ◽  
Large Numbers ◽  
Single Mating ◽  
Sperm Reservoir ◽  
The University

In the monovular macropodid marsupial, the tammar wallaby (Macropus eugenii), the cervices are the primary selective barrier to spermatozoa, resulting in differential transport to the non-gravid uterus where a sperm reservoir is established (Tyndale-Biscoe CH and Rodger JC 1978 J. Reprod. Fertil. 52, 37–43). However, due to limited sample size, the dynamics of sperm transport could not be thoroughly examined. In this study, the distribution of spermatozoa, the size of the copulatory plug in the reproductive tract at various times after mating, and the timing of ovulation were characterized in 28 naturally mated female tammars. After the first postpartum (p.p.) mating, adult females were isolated and their reproductive tracts dissected at 0.5, 6, 18, 36, and 40 h post-coitum (p.c.). Each tract was ligated into 13 major anatomical sections, and spermatozoa and eggs were recovered by flushing. Mating occurred 21.7 ± 2.5 h p.p. (mean ± SEM; n = 20) in these animals that were checked frequently and lasted 7.8 ± 0.7 min (n = 15). Within 0.5 h after a single mating (n = 5) the tract contained 2.6 ± 1.0 × 107 spermatozoa and 21.6 ± 8.8 g of copulatory plug, 96 and 70% of which was lost within 6 h p.c., respectively. Spermatozoa reached the uterus, isthmus, and ampulla of the oviduct ipsilateral to the developing follicle within 0.5, 6, and 18 h p.c. respectively, and a uterine population of 2.6 ± 1.2 × 104 spermatozoa (n = 24) was maintained for over 40 h (ANOVA, P > 0.05). Sperm numbers were reduced at the cervix (up to 57-fold) and utero-tubule junction (8-fold), and only 1 in ∼7600 ejaculated spermatozoa (3.4 ± 0.9 × 103; n = 14) reached the oviduct on the side of ovulation. Although sperm numbers were reduced in the gravid uterus (n = 24), differential transport of spermatozoa was not observed (ANOVA, P > 0.05). Ovulation and recovery of sperm-covered eggs from the isthmus of the oviduct occurred 36–41 h p.c. (49–72 h p.p.) (n = 8). Like many eutherian mammals, but in contrast to polyovular dasyurid and didelphid marsupials, the tammar ejaculates large numbers of spermatozoa, but transport is relatively inefficient and sperm storage in the tract before ovulation is limited. Research was supported by the Australian Research Council (grant No. C09930004) and the University of Melbourne.

Sperm transport, size of the seminal plug and the timing of ovulation after natural mating in the female tammar wallaby Macropus eugenii

2004 ◽  
Vol 16 (8) ◽  
pp. 811 ◽  
Author(s):  
Damien B. B. P. Paris ◽  
David A. Taggart ◽  
Monica C. J. Paris ◽  
Peter D. Temple-Smith ◽  
Marilyn B. Renfree
Keyword(s):  
Reproductive Tract ◽  
Post Partum ◽  
Tammar Wallaby ◽  
Sperm Storage ◽  
Sperm Transport ◽  
Macropus Eugenii ◽  
Large Numbers ◽  
Single Mating ◽  
Natural Mating

The distribution of spermatozoa and seminal plug in the reproductive tract and the timing of ovulation were examined at various times in a naturally mated monovular macropodid marsupial, namely the tammar wallaby (Macropus eugenii). After the first post partum (p.p.) mating, 28 females were isolated and their reproductive tracts dissected at 0.5, 6, 18, 36 and 40 h post coitum (p.c.). Each tract was ligated into 13 major anatomical sections and spermatozoa and eggs were recovered by flushing. Mating was possibly delayed by handling and occurred 21.7 ± 2.5 h p.p. in these animals. Copulation lasted 7.8 ± 0.7 min. Within 0.5 h after a single mating, the tract contained 25.8 ± 10.2 × 106 spermatozoa and 21.6 ± 8.8 g of seminal plug, 96% and 70% of which was lost within 6 h p.c. respectively. Spermatozoa reached the uterus, isthmus and ampulla of the oviduct on the side of the developing follicle within 0.5, 6 and 18 h p.c., respectively, and a uterine population of 26.1 ± 12.103 spermatozoa was maintained for over 40 h. Sperm numbers were reduced at the cervix (up to 57-fold) and uterotubule junction (eight-fold) and only one in approximately 7500 ejaculated spermatozoa (3.4 ± 0.9 × 103) reached the oviduct on the follicle side. Differential transport of spermatozoa was not observed. Although the numbers of spermatozoa were reduced in the parturient uterus, they were highly variable and were not significantly different to those in the non-parturient uterus. Ovulation and recovery of sperm-covered eggs from the isthmus occurred 36–41 h p.c. (49–72 h p.p.). In contrast with the polyovular dasyurid and didelphid marsupials, the tammar wallaby ejaculates large numbers of spermatozoa, but transport is relatively inefficient and sperm storage in the tract before ovulation is limited.

Sexual development of a model marsupial male

2006 ◽  
Vol 54 (3) ◽  
pp. 151 ◽  
Author(s):  
Marilyn B. Renfree ◽  
Andrew J. Pask ◽  
Geoff Shaw
Keyword(s):  
Sexual Development ◽  
Sexual Differentiation ◽  
Extended Period ◽  
Tammar Wallaby ◽  
Experimental Manipulation ◽  
Exact Role ◽  
Oestrogen Treatment ◽  
Linked Gene ◽  
Macropus Eugenii ◽  
And Control

In eutherian mammals sexual differentiation occurs during fetal development, making experimental manipulation difficult, unlike in marsupials. We are investigating the roles of several key genes and hormones whose exact role in gonadal differentiation is still unclear using the tammar wallaby (Macropus eugenii) as a model. As in humans, unlike in mice, the testis-determining gene SRY is expressed in male tammar fetuses in many tissues over an extended period. Not all sexual differentiation depends on testicular hormones. Scrotum and mammary glands are under the control of X-linked gene(s). Our demonstration of DMRT1 expression in tammar and mouse ovaries suggests it has a wider role than previously thought. The Y-borne copy of ATRX (ATRY) is coexpressed with DMRT1 in developing testis. Gonadal sex reversal can be induced in males by neonatal oestrogen treatment and in females by grafting developing ovaries to males or culturing them in minimal medium. Treatments of developing young with various androgens, and studies of steroid metabolism have shown that the steroid androstenediol may have a previously unrecognised role in virilisation. Our studies using a marsupial model have given some surprising insights into the evolution and control of sexual development in all mammals.

Prostaglandin alone does not cause luteolysis in the non-pregnant tammar wallaby, Macropus eugenii

1991 ◽  
Vol 3 (1) ◽  
pp. 17 ◽  
Author(s):  
LA Hinds
Keyword(s):  
Sampling Period ◽  
Tammar Wallaby ◽  
Plasma Prolactin ◽  
Plasma Progesterone ◽  
Macropus Eugenii ◽  
Prostaglandin F2 Alpha ◽  
Group 3 ◽  
Group 2 ◽  
Group 1

At parturition in the tammar wallaby, Macropus eugenii, the process of luteolysis involves both prostaglandin and prolactin. Prolactin alone is luteolytic, but it has been unclear whether prostaglandin F2 alpha (PGF2 alpha) is also directly luteolytic. To examine this, three groups non-pregnant animals were studied on Day 26 after removal of pouch young (the day equivalent to parturition). Group 1 (controls) received saline injections on Days 25 and 26, Group 2 received saline on Day 25 and PGF2 alpha on Day 26, and Group 3 was pre-treated with bromocriptine (Parlodel LA, Sandoz) on Day 25 and received PGF2 alpha on Day 26. For 12 h after treatment on Day 26, plasma progesterone and prolactin concentrations were determined and behaviour was recorded. Plasma progesterone concentrations remained elevated and plasma prolactin was basal throughout the sampling period in the control animals (Group 1). After treatment with PGF2 alpha (Group 2), plasma prolactin was elevated within 15 min and plasma progesterone decreased significantly (P less than 0.001) from 600 pg mL-1 (1.91 nmol L-1) to less than 200 pg mL-1 (0.64 nmol L-1) by 8 h. However, luteolysis did not occur in females pre-treated with bromocriptine on Day 25 and injected with PGF2 alpha on Day 26 (Group 3), and prolactin concentrations remained basal. All females treated with PGF2 alpha showed parturient behavior. The results clearly show that PGF2 alpha is not directly luteolytic on Day 26 of the non-pregnant cycle, but they confirm that PGF2 alpha induces the release of prolactin, which is directly luteolytic.

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