Contrast imaging ultrasound detects abnormalities in the marmoset ovary

The development of a functional vascular tree within the primate ovary is critical for reproductive health. To determine the efficacy of contrast agents to image the microvascular environment within the primate ovary, contrast ultrasonography was performed in six reproductive-aged female common marmosets (Callithrix jacchus) during the late luteal phase of the cycle, following injection of Sonovue™. Regions of interest (ROIs), representing the corpus luteum (CL) and noncorpus luteum ovarian tissue (NCLOT), were selected during gray-scale B-mode ultrasound imaging. The magnitude of backscatter intensity of CL and NCLOT ROIs were calculated in XnView, post hoc: subsequent gamma-variate modeling was implemented in Matlab to determine perfusion parameters. Histological analysis of these ovaries revealed a total of 11 CL, nine of which were identified during contrast ultrasonography. The median enhancement ratio was significantly increased in the CL (5.54AU; 95% CI -2.21-68.71) compared to the NCLOT (2.82AU; 95% CI 2.73-15.06; P < 0.05). There was no difference in time parameters between the CL and NCLOT. An additional avascular ROI was identified in the ovary of Animal 5, both histologically and by ultrasonography. This cystic ROI displayed a markedly lower enhancement ratio (0.79AU) and higher time parameters than mean CL and NCLOT, including time to peak and time to wash out. These data demonstrate, for the first time, the ability of commercially available contrast agents, to differentiate structures within the nonhuman primate ovary. Contrast-enhanced ultrasonography has a promising future in reproductive medicine.

Interactions between chuditch (Dasyurus geoffroii) and introduced predators: a review

The chuditch is a carnivorous marsupial that has suffered catastrophic decline since European settlement in Australia. The impacts of introduced foxes and feral cats are thought to have contributed to this decline. Although chuditch populations appear to respond favourably to fox control, ecological theory predicts that other predators, including feral cats, are also likely to increase in abundance when foxes are removed. The flow-on effects of these predicted increases are not known, but are potentially significant for chuditch and for other native fauna. Here, we review the evidence for limiting effects of foxes and feral cats on chuditch populations. We also discuss the likely effects on chuditch populations (direct and indirect) of current fox control practices. Using recent advances in carnivore community ecology, we make testable predictions regarding likely interactions within the predator guild. Experiments should adopt a whole-of-community approach, seeking to clarify the effects of fox control on the entire suite of native and introduced predators, as well as on the abundance and diversity of prey.

Germ cell differentiation in the marmoset (Callithrix jacchus) during fetal and neonatal life closely parallels that in the human

BACKGROUND

Testicular germ cell tumours (TGCT) are thought to originate from fetal germ cells that fail to differentiate normally, but no animal model for these events has been described. We evaluated the marmoset (Callithrix jacchus) as a model by comparing perinatal germ cell differentiation with that in humans.

METHODS

Immunohistochemical profiling was used to investigate germ cell differentiation (OCT4, NANOG, AP-2gamma, MAGE-A4, VASA, NANOS-1) and proliferation (Ki67) in fetal and neonatal marmoset testes in comparison with the human and, to a lesser extent, the rat.

RESULTS

In marmosets and humans, differentiation of gonocytes into spermatogonia is associated with the gradual loss of pluripotency markers such as OCT4 and NANOG, and the expression of germ cell-specific proteins such as VASA. This differentiation occurs asynchronously within individual cords during fetal and early postnatal life. This contrasts with rapid and synchronous germ cell differentiation within and between cords in the rat. Similarly, germ cell proliferation in the marmoset and human occurs throughout perinatal life, in contrast to rats in which proliferation ceases during this period.

CONCLUSIONS

The marmoset provides a good model for normal human germ cell differentiation and proliferation. The perinatal marmoset may be a useful model in which to establish factors that lead to failure of normal germ cell differentiation and the origins of TGCT.

Role of the neonatal period of pituitary-testicular activity in germ cell proliferation and differentiation in the primate testis

BACKGROUND

The neonatal period of pituitary-testicular activity (NPTA) in human males has been hypothesized to play a role in germ cell proliferation and differentiation and to be defective in cryptorchid testes. The present study was carried out to establish in the marmoset if suppression of the NPTA, by treatment with a GnRH antagonist, results in impaired germ cell proliferation and/or differentiation.

METHODS

Comparison of germ cell (GC) numbers and differentiation from gonocytes to pre-spermatogonia and spermatogonia, at birth (in controls) and at the end of the NPTA in marmoset co-twin males treated from birth to age 14 weeks with vehicle or GnRH antagonist.

RESULTS

From birth to age 18-24 weeks, testis weight increased approximately 5-fold and GC number approximately 10-fold, including increased numbers of gonocytes and pre-spermatogonia and the first appearance of spermatogonia. Treatment with GnRH antagonist attenuated the increase in testis weight and GC numbers, but the effect was only partial (24-30% reduction), and the relative proportions of gonocytes, pre-spermatogonia and spermatogonia in the GnRH antagonist-treated group were unchanged from control values.

CONCLUSIONS

The NPTA plays only a minor, if any, role in GC proliferation and differentiation in the marmoset. The changes in GnRH antagonist-treated co-twins may reflect impaired GC survival due to withdrawal of gonadotrophin support for Sertoli cells. These findings do not support a pivotal role for the NPTA in neonatal GC development in primates.

Testicular changes during infantile 'quiescence' in the marmoset and their gonadotrophin dependence: a model for investigating susceptibility of the prepubertal human testis to cancer therapy?

BACKGROUND

Inexplicably, boys treated with some therapies for cancer at age 2-10 years, a time of supposed 'testicular quiescence', are at risk of low sperm counts/infertility in adulthood. Our aims were to use the marmoset as a surrogate for man to establish testicular cell function/activity during 'quiescence' between the neonatal period and puberty, and to test if any cell activity could be suppressed by prior treatment with a GnRH antagonist.

METHODS AND RESULTS

Based on immunoexpression studies, functional development of Sertoli cells (SGP-2, androgen receptor) and Leydig cells (3 beta-hydroxysteroid dehydrogenase) was detectable at an age (35 weeks) when the testis is considered to be quiescent, and in advance of the pubertal rise in blood testosterone levels (50-60 weeks). Other changes at 35 weeks were the appearance of focal seminiferous tubule lumens and proliferating germ cells [indicated by immunoexpression of proliferating cell nuclear antigen (PCNA)]. Treatment from 25 to 35 weeks with GnRH antagonist largely (>85%) prevented these changes. However, the PCNA-labelling index of spermatogonia in GnRH antagonist-treated animals did not differ from controls (41.3 versus 43.6%) though total spermatogonia volume per testis was reduced by 41%. Some protein markers (inhibin-alpha, estrogen receptor-beta) showed little change with age or treatment. Beyond 35 weeks, GnRH antagonist-treated animals showed a delay in the pubertal rise in plasma testosterone levels.

CONCLUSIONS

These findings reinforce the view that the 'childhood' testis is not quiescent. This may explain the damaging effects of some cancer therapies on subsequent fertility of boys and raises the issue of protective intervention. The present studies suggest that GnRH antagonist-based intervention might be only partially successful. Identification of the factors regulating spermatogonial development in the infant marmoset may aid in the design of such strategies.

Comparison of androgen receptor and oestrogen receptor beta immunoexpression in the testes of the common marmoset (Callithrix jacchus) from birth to adulthood: low androgen receptor immunoexpression in Sertoli cells during the neonatal increase in testosterone concentrations

The aims of this study were: (i) to investigate the cellular immunoexpression of androgen receptor and oestrogen receptor beta in the testes of the common marmoset (Callithrix jacchus) during neonatal life compared with their expression at later ages; (ii) to establish whether neonatal marmoset Sertoli cells are targets for androgens or oestrogens or both; and (iii) to investigate the relationship between neonatal plasma testosterone concentrations and androgen receptor immunoexpression by abolishing the neonatal testosterone surge with a potent GnRH antagonist. Androgen receptor and oestrogen receptor beta immunoexpression were evaluated in neonatal animals aged 1-4 days, 4 weeks and 6 weeks, and compared with immunoexpression in animals aged 18-22 weeks (early infancy), 35 weeks (late infancy), 58-62 weeks (late pubertal) and > 100 weeks (adult). Immunoexpression of androgen receptor in the reproductive tract was also evaluated at each age. Sertoli cell immunoexpression of androgen receptor was weak or absent in neonatal animals, but increased substantially in infant animals, reaching adult levels by the end of infancy. In contrast, immunoexpression of androgen receptor during the neonatal period was strong in testicular interstitial cells and very strong in epithelial cell nuclei throughout the reproductive tract, and did not change greatly with age in these cells or tissues. Similarly, immunoexpression of oestrogen receptor beta was prominent in many Sertoli cells and in the germ cells of neonatal animals, and was relatively constant throughout life. Weak immunoexpression of androgen receptor in neonatal Sertoli cells was associated with high plasma testosterone concentrations (2.7-5.5 ng ml(-1)), whereas strong Sertoli cell immunoexpression was associated with baseline (approximately 0.12 ng ml(-1)) testosterone concentrations in infant animals and with > 10 ng ml(-1) in late pubertal and adult animals. Immunoexpression of androgen receptor and oestrogen receptor beta was also evaluated in co-twin males aged 4 and 35 weeks, after treatment from birth to 4 weeks or from week 25 to week 35, respectively, with either vehicle or with GnRH antagonist at a dose known to suppress the neonatal testosterone surge completely. Only GnRH antagonist treatment during weeks 25-35 reduced androgen receptor immunoexpression, whereas immunoexpression of oestrogen receptor beta was unaffected by treatment during either period. On the basis of these findings it is suggested that: (i) neonatal marmoset Sertoli cells may be targets primarily for oestrogens rather than androgens; (ii) androgen receptor expression in the testes of neonatal and infant marmosets is not regulated in a straightforward way by testosterone; and (iii) high neonatal concentrations of plasma testosterone are not absolutely necessary for expression of androgen receptor in marmoset testes at this time.

Water and electrolyte homeostasis and kidney function of desert-dwelling marsupial wallabies in Western Australia

Prolonged drought, necessitating conservation of water, is one of the major environmental challenges faced by many Australian marsupials. Radioactive isotopes of water and sodium were used to assess the ability of two species of marsupial wallabies to maintain water and electrolyte balance during periods of extreme water deprivation in the arid Pilbara region of Western Australia. The spectacled hare-wallaby, Lagorchestes conspicillatus, has the lowest mass-specific rate of water turnover at 27.5 ml.kg(-0.82).day(-1) yet reported for any mammal and was two to three orders of magnitude lower than that of the Rothschild's rock-wallaby, Petrogale rothschildi. Studies of renal function show that the hare-wallaby conserves water by producing a highly concentrated urine under the influence of lysine vasopressin (LVP), the anti-diuretic hormone (ADH) in macropodid marsupials. In contrast, rock-wallabies show unusual renal responses to water deprivation, with no change in LVP levels and a limited response to water deprivation involving a reduction in renal plasma flow and glomerular filtration rate, with no significant change in tubular function. Both species are able to maintain water and electrolyte homeostasis during periods of drought, highlighting the efficacy of their differing adaptive solutions to the problem of water scarcity, although the hare-wallaby is superior to the rock-wallaby in this respect. Rock-wallabies appear to rely primarily on behavioural rather than physiological responses for their survival in the Pilbara and appear to be more vulnerable to extinction in the event of significant habitat modification. The secure nature of their rock habitat, however, means that they have suffered less than hare-wallabies in the recent past.

Benzodiazepines act on GABAA receptors via two distinct and separable mechanisms

Benzodiazepines (BZs) act on gamma-aminobutyric acid type A (GABAA) receptors such as alpha1beta2gamma2 through key residues within the N-terminal region of alpha subunits, to render their sedative and anxiolytic actions. However, the molecular mechanisms underlying the BZs' other clinical actions are not known. Here we show that, with low concentrations of GABA, diazepam produces a biphasic potentiation for the alpha1beta2gamma2-receptor channel, with distinct components in the nanomolar and micromolar concentration ranges. Mutations at equivalent residues within the second transmembrane domains (TM2) of alpha, beta and gamma subunits, proven important for the action of other anesthetics, abolish the micromolar, but not the nanomolar component. Converse mutation of the corresponding TM2 residue and a TM3 residue within rho1 subunits confers diazepam sensitivity on homo-oligomeric rho1-receptor channels that are otherwise insensitive to BZs. Thus, specific and distinct residues contribute to a previously unresolved component (micromolar) of diazepam action, indicating that diazepam can modulate the GABAA-receptor channel through two separable mechanisms.

Suppression of luteal angiogenesis in the primate after neutralization of vascular endothelial growth factor

Manipulation of angiogenesis may have a profound effect on female reproductive function, but this has not yet been demonstrated by direct experiment in species with ovulatory cycles similar to those in women. To investigate whether angiogenesis could be inhibited in the primate corpus luteum, and the consequences of such inhibition on luteal function, marmosets were treated with an antibody to vascular endothelial growth factor (VEGF). Treatment commenced at the time of ovulation and was continued for 3 days (early luteal group) or 10 days (midluteal group). Bromodeoxyuridine was used to label proliferating cells, being administered 1 h before collecting ovaries from control and treated animals in the early or midluteal phase. Ovarian sections were stained using an antibody to bromodeoxyuridine, and a proliferation index was obtained; endothelial cell quantification was performed using factor VIII as an endothelial cell marker. Intense proliferation in the early luteal phase was suppressed by anti-VEGF treatment. This resulted in blockade of development of the normally extensive capillary bed, as in the animals treated until the mid-luteal phase the numbers of endothelial cells were reduced. The hormone-producing cells remained largely unaltered in the posttreatment corpus luteum, although the presence of lipid accumulation, and small pockets of cells showing basophilia and nuclear condensation were observed. Significantly, luteal function, as judged by secretion of progesterone, was markedly compromised by the treatment, being reduced by 60% in comparison with controls. It is concluded that VEGF-mediated angiogenesis is an essential component of luteal function in primates and therefore has the potential to be regulated.

The status and conservation of native rodents in Western Australia

This paper examines the conservation status of Western Australia’s native rodent fauna using IUCN criteria and compares this with their current status under State and Commonwealth legislation, as well as that recommended in the Rodent Action Plan. Of the 35 native rodent taxa known in Western Australia, four (11%) are currently listed as extinct, and six (17%) as threatened under Western Australian legislation. Nine are listed as threatened under Commonwealth legislation. It is proposed that two, currently unlisted, island sub-species should be regarded as threatened. Some decreases in conservation status are also proposed. Predation by feral cats, habitat destruction and the use of surface shelter structures are suggested as primary factors in the decline of native rodents. Conservation programs are underway for most threatened taxa in Western Australia, including the implementation of recovery plans for the Shark Bay mouse and greater stick-nest rat. The heath rat is the only threatened rodent lacking a conservation program in Western Australia. The work planned or required for rodent conservation is presented and includes survey for the critically endangered central rock-rat, and translocation programs for other threatened taxa. The distribution of most taxa is relatively well known; however, there is a need to commence, or complete, taxonomic assessment of some.

Differential modulation of the gamma-aminobutyric acid type C receptor by neuroactive steroids

Gamma-aminobutyric acid type C receptor channels (GABA(C)Rs) composed of rho subunits are pharmacologically distinct from GABA(A) receptor channels (GABA(A)Rs). This difference is illustrated by the insensitivity of homo-oligomeric rho(1) receptor channels to many known modulators of GABA(A)Rs, such as barbiturates and benzodiazepines. A number of endogenous metabolites of corticosterone and progesterone, known as neuroactive steroids, compose yet another class of compounds that can modulate GABA(A)Rs. Here, several neuroactive steroids are shown to also modulate the rho(1) receptor channel. 5alpha-Pregnane-3alpha,21-diol-20-one (allotetrahydrodeoxycorticosterone), 5alpha-pregnane-3alpha-ol-11, 20-dione (alphaxalone), and 5alpha-pregnane-3alpha-ol-20-one (allopregnanolone) potentiated the GABA-evoked currents from rho(1) receptor channels and concomitantly altered the deactivation kinetics by prolonging the decay time. In contrast, 5beta-pregnane-3alpha-ol-20-one (pregnanolone), 5beta-pregnane-3, 20-dione (5beta-dihydroprogesterone), and 5beta-pregnane-3alpha, 21-diol-20-one (tetrahydrodeoxycorticosterone), all potentiators of GABA(A)Rs, inhibited the GABA-elicited currents of the rho(1) receptor channel. In comparison to GABA(A)Rs, the modulation of rho(1) receptor channels by these neuroactive compounds occurred with relatively high concentrations of the neuroactive steroids and was more prominent in the presence of low concentrations of GABA, equivalent to fractions of the EC(50) value of the rho(1) receptor channel. Structural comparison of these six neuroactive steroids reveals that the key parameter in determining the mode of modulation for the rho(1) receptor channel is the position of the hydrogen atom bound to the fifth carbon, imposing a trans- or cis-configuration in the backbone structure. This is the first demonstration of isomeric compounds that can differentially modulate the activity of the rho(1) receptor channel.

The effect of the angiogenesis inhibitor TNP-470 on luteal establishment and function in the primate

Angiogenesis during luteal development is probably essential for normal lutein cell function. Since the angiogenesis inhibitor TNP-470 inhibits pregnancy in mice, the current study investigated its effects on the establishment and function of the primate corpus luteum. Regularly ovulating macaques were treated with TNP-470 (6 mg/kg), i.v. in three doses, 48 h apart. Serum progesterone concentrations, as indicators of treatment effect, were normal in four macaques where treatment commenced at the onset of the ovulatory progesterone rise, and in five of eight in which treatment commenced a few days before ovulation. In the other three the normal progesterone rise was absent. To investigate the direct effect on luteal angiogenesis of a daily dose over a longer period, four marmosets received 18 mg/kg/day of TNP-470 i.v. for 9 days starting at ovulation. On day 10, luteal cell proliferation was determined by nuclear bromodeoxyuridine incorporation. Luteal microvasculature was examined using immunocytochemical factor VIII staining, and endothelial cell and luteal function assessed by in-situ hybridization of insulin-like growth factor binding protein-3 mRNA and plasma progesterone concentrations respectively. None of these parameters were affected by the TNP-470 treatment. The results show that, with the treatment regimens employed, TNP-470 had no significant effect on the expression of the differentiated state of the primate corpus luteum.

Evaluation of the contraceptive potential of recombinant human ZP3 and human ZP3 peptides in a primate model: their safety and efficacy

PROBLEM

The unique recognition events that result in the avid binding of mammalian spermatozoa to the surface of the zona pellucida (ZP) are being exploited in the development of contraceptive vaccines. In this study, the safety and efficacy of a vaccination strategy based on the induction of active immunity against purified, glycosylated, recombinant human ZP3 (rhZP3) has been evaluated in a primate model, Callithrix jacchus.

METHOD OF STUDY

Long-term infertility was established after immunization with rhZP3 and the resulting immune sera reacted with rhZP3 on an enzyme-linked immunosorbent assay (ELISA) and immunolocalized exclusively to the outer surface of native ZP on marmoset ovarian sections. However, this contraceptive effect was inevitably associated with the eventual appearance of an ovarian pathology characterized by a depletion of primordial follicles. In an attempt to circumvent this side effect, human ZP3 (hZP3) was epitope mapped and four continuous, immunodominant B-cell epitopes (hZP3(45-64), hZP3(93-110), hZP3(172-190) and hZP3(341-360) were evaluated for contraceptive efficacy in vivo. Using peptide-tetanus toxoid (TT) conjugates to enhance immunogenicity, antipeptide antibodies were raised against these immunogens, which also cross-reacted with rhZP3 on ELISA. In addition, antibodies against hZP3(45-64) and hZP3(172-190) recognized native ZP on marmoset ovarian sections when a microwave technique was used to enhance epitope presentation.

RESULTS

No ovarian pathology was observed after the long-term administration of these peptide immunogens, and fertility was suppressed when compared with TT controls but could not be correlated to the antibody titer.

CONCLUSION

Clearly, further research is required to identify optimal B-cell epitopes that will reliably induce infertility, free from any ovarian pathology.

Initiation of high dose gonadotrophin-releasing hormone antagonist treatment during the late follicular phase in the macaque abolishes luteal function irrespective of effects upon the luteinizing hormone surge

The determination of the efficacy of gonadotrophin-releasing hormone (GnRH) antagonists in blocking the luteinizing hormone (LH) surge and luteal function is important for our understanding of the control of the menstrual cycle and for clinical application. GnRH antagonists have failed to block the LH surge reliably in the non-human primate. The aim of the study was to utilize high dose GnRH antagonist treatment administered during the late follicular phase of the menstrual cycle to block the pre-ovulatory LH surge. It was postulated that the LH surge would be prevented in all animals, but if this failed subsequent luteal function would be blocked by continued suppression of LH, since the early corpus luteum is susceptible to inhibition by GnRH antagonist treatment. A group of 16 adult female stumptailed macaques (Macaca arctoides) with regular menstrual cycles were selected. The GnRH antagonist [N-Ac-D-Nal(2)1,D-pCl-Phe2,D-Pal(3)3,D-(Hci)6, Lys(iPr)8,D-Ala10]GnRH (Antarelix) (concentration 10 mg/ml) was administered as three daily s.c. injections, at a dose of 1 mg/kg on days 11, 12 and 13 of the follicular phase of the menstrual cycle. Of nine macaques in which it was judged that the treatment was commenced within 1 day of the expected LH surge (serum oestradiol >400 pmol/l), six demonstrated a decline in serum oestradiol concentrations, a total block of the LH/follicle stimulating hormone (FSH) surge and inhibition of ovulation as judged by an absence of a rise in progesterone concentrations. In the three other animals in this category, a partial LH surge occurred, but this failed to result in a functional corpus luteum. In a further three animals treatment was initiated on the day of the LH surge, and again there was absence of a subsequently functional corpus luteum. These results show that GnRH is involved at the time of the mid-cycle LH/FSH surge in the non-human primate. Initiation of high dose GnRH antagonist treatment during the periovulatory period abolishes luteal function irrespective of its effects upon the LH surge because of its long-term action and resultant withdrawal of luteal support.

Field Metabolism and Turnover in the Golden Bandicoot (Isoodon-Auratus) and Other Small Mammals From Barrow Island, Western-Australia

Barrow Island, which lies about 90 km north of Onslow off the arid Western Australian Pilbara coast, experienced its driest year on record in 1990 with a total of only 122.4 mm of rain. Golden bandicoots captured in November 1990 evidenced poor condition and mean body mass was a low 242.6 +/- 10.9 g with-a total body water content (TBW) of 76.3 +/- 1.4%. Despite this substantial loss of body water and solids, the animals maintained water and electrolyte balance during the period of turnover [water influx 79.5 +/- 6.9 v. efflux 83.3 +/- 5-7 mL (kg0.82 day)-1 and sodium influx 4.9 +/- 0.7 v. efflux 5.3 +/- 0.7 mmol (kg day)-1]. By April 1991, although only a further 37.4 mm of rain had been recorded on Barrow Island, the condition of the bandicoots had improved markedly, as a result of exploitation of insect resources, and their mean body mass had increased to 306.5 +/- 22.6 g and TBW decreased to 62.5 +/- 1.4% (both P < 0.001), the latter reflecting enhanced fat stores. This general improvement in condition of the bandicoots was in marked contrast to that of other herbivorous marsupials on the island. Rates of water and sodium turnover of the golden bandicoots were, however, not significantly different from those measured in the previous November, Field Metabolic Rates (FMRs), measured with doubly labelled water ((HHO))-H-3-O-18, were extremely low, averaging only 0.45 +/- 0.26 mL CO2 (g h)-1, which is very close to laboratory estimates of 0.35 +/- 0.09 mL O2(g h)-1 for the basal metabolic rate of this species. A major cyclone struck Barrow Island on 3 March 1992, with 162 mm of rain falling in 24 h, and turnover measurements in May of that year revealed a substantial increase in rates of water flux. Mean body mass further increased to 332.6 +/- 8.5 g and TBW averaged 61.8 +/- 1.1%. Water turnover rates were significantly elevated when compared with April of the previous year with an influx of 112.5 +/- 7.3 and an efflux of 119.0 +/- 7.6 mL (kg0.82 day)-1 respectively (both P = 0.001). Rates of sodium turnover, however, were only slightly lower at 3.6 +/- 0.5 and 4.1 +/- 0.5 mmol (kg day)-1 for influx and efflux respectively (P = 0.056 for influx only), suggesting a slight decrease in the average sodium content of the diet. The volume of water required to maintain hygric balance was estimated by regression analysis at 26.7 mL day-1 [=88.3 mL (kg0.82 day)-1] in November 1990, and 33-9 mL day-1 [=85.2 mL (kg0.82 day)-1] in May 1992, following rain. The FMR of eight bandicoots was very significantly elevated to 1.39 +/- 0.23 mL CO2 (g h)-1 after rain, which is substantially higher than even the FMR of 0.91 +/- 0.07 mL CO2(g h)-1, or 644 kJ day-1, reported for the closely related southern brown bandicoot (Isoodon obesulus) studied in the region of Perth by Nagy et al. (1991). Turnover rates of water and sodium for two rodent species, the Barrow Island mouse (Pseudomys nanus) and the rock rat (Zyzomys argurus), were very similar to those recorded for golden bandicoots in the dry period, but FMRs were a little higher at 0.80 +/- 0.26 and 0.59 +/- 0-36 mL CO2(g h)-l respectively. The FMR of Barrow Island mice increased very significantly to a mean of 2.73 +/- 0.50 mL CO2(g h)-l after rain, but rock rats were not caught at this time. The data document the impressive ability of these mammals to avail themselves of extremely limited resources and maintain physiological homoiostasis under conditions of extreme aridity.

Analysis of the contraceptive potential of antibodies against native and deglycosylated porcine ZP3 in vivo and in vitro

We have undertaken a comparative analysis of the contraceptive activity of antibodies directed against the porcine sperm receptor zona pellucida antigen (ZP3) and its Mr = 32,000 polypeptide core (DGZP-32). The strategies employed for this analysis included the induction of active immunity in a primate, the common marmoset, and an in vitro fertilization protocol involving the use of viable human ova. In both experimental situations, antibodies against ZP3 were shown to exhibit contraceptive activity, leading respectively to the induction of long-term infertility in the primate model and to the complete inhibition of human fertilization in vitro. The in vivo studies also revealed that the induction of high titer antibodies against ZP3 was inevitably associated with the appearance of an ovarian pathology characterized by the progressive depletion of the primordial follicle pool within one to two years. This side effect could not be alleviated by the use of DGZP-32 as antigen since the induction of immunity against this polypeptide was also associated with the eventual appearance of an ovarian pathology identical to that observed with ZP3. Furthermore, the DGZP-32 peptide was less effective than ZP3 in inducing the formation of antibodies capable of inhibiting the fertilization of human ova in vitro. We conclude that significant problems remain with the use of deglycosylated zona peptides for the development of contraceptive vaccines and that their potential will not be realized until the epitopes responsible for the induction of infertility and the primordial follicle depletion have been identified and segregated.

Influence of the gonad on the degree of suppression induced by an LHRH agonist implant in the marmoset monkey

In a previous study pituitary-testicular function was shown to be maintained in a New World primate after the administration of an LHRH agonist implant. In the present study the mechanism of action of the same LHRH agonist (buserelin) on pituitary-gonadal function in the marmoset was investigated and a comparison made between the effects of treatment in three intact males, six adult cyclic females with regular ovulatory cycles, and six long-term ovariectomized animals. These were injected s.c. with an LHRH agonist implant (1.5 mg buserelin in a rod 0.5 cm long). In both the males and intact females, basal plasma LH concentrations were maintained within the normal range throughout the expected duration of agonist action (at least 3 months). Despite this, an absence of response to an LHRH challenge indicated that pituitary desensitization had occurred. In the intact females, ovulation was inhibited in five of six animals, plasma progesterone concentrations initially being maintained but subsequently remaining suppressed until 136 +/- 18 (S.E.M.) days after treatment. Responsiveness to administered LHRH returned prior to onset of return to ovarian cycles. In contrast, in ovariectomized marmosets, plasma LH was markedly suppressed to concentrations which were at or below the limit of detection of the assay and were therefore less than those observed in the buserelin-implanted intact animals. These results show that apparently normal pituitary-gonadal function in this species disguises an underlying pituitary desensitization to LHRH. This allows continuation of testosterone secretion in the male, but in the female ovulation is prevented, presumably as a result of failure of the desensitized pituitary to produce an LH surge.(ABSTRACT TRUNCATED AT 250 WORDS)

Field Metabolic Rates, Water Fluxes, and Feeding Rates of Quokkas, Setonix-Brachyurus, and Tammars, Macropus-Eugenii, in Western-Australia

Field metabolic rates (FMRS) and water influx rates were measured by means of doubly labelled water in free-ranging quokkas living on Rottnest I, and free-ranging tammar wallabies living on Garden I. Feeding rates were estimated from energy requirements. Quokkas ranging in body mass from 1.44 to 2.83 kg (mean 1.90 kg) had FMRS averaging 0.574 mL C02 (g.h)-', which is equivalent to 548 kJ d-'. Their rates of total water intake averaged 47.3 mL (kg.d)-', or 90.5 mL d-'. Estimated feeding rate was 54.8 g (dry matter) per day, and water ingested as part of the food (preformed and metabolically produced) can completely account for total water intake. We believe that quokkas did not drink water during our field measurements. Tammars ranging in body mass from 3.20 to 6.35 kg (mean 4.38 kg) had FMRS averaging 0.518 mL CO2 (g.h)-', which is equivalent to 1150 kJ d-'. Their rates of water influx averaged 57.5 mL (kg.d)-', or 270 mL d-', and their estimated feeding rate was 115 g (dry matter) per day. Tammars also probably did not drink free-standing water during our study. FMRs of quokkas averaged 1 .80 x basal metabolic rate (BMR), and FMRS of tammars averaged 1.87 x BMR; this difference is not significant. We estimate that the 5000 quokkas on Rottnest I. consume at least 100 000 kg of plant matter (dry mass) per year, and the 2173 tammars on Garden I. ingest more than 90 000 kg. Measurements of food availability are needed to permit evaluation of the relationship between food supply and demand for these two populations of macropod marsupials.

A restraint system for the common marmoset (Callithrix jacchus)

A method for restraining the marmoset in a primate chair is described. The device is inexpensive to construct, is reliable, and the majority of animals can be habituated to its use. The chair has been used in neurobiological studies employing electrophysiological recordings, with or without concurrent collection of serial blood samples.

Water and Sodium Turnover in Coastal and Inlnad Populations of the Ash-Grey Mouse, in Western Austrlia

The water and sodium turnovers of a coastal and an inland population of P. albocinereus were studied seasonally. Although the inland habitat receives considerably less rain and sodium than the coastal habitat, water turnover rates were significantly lower only in May and sodium turnover lower only in August. Water influx rates were lowest at both locations during the summer months, positively correlated with the water content of the vegetation and positively correlated with the amount of rain received in the 30 days before each sampling period. Water efflux rates were negatively correlated with urine osmolality. Sodium influx rates were highest during the summer months and were correlated with the sodium content of the vegetation but not with the sodium deposited in the study areas. Sodium efflux rates were positively correlated with the urine sodium concentration. During the dry months, water and sodium influxes are linked; this is not apparent during the wetter months. The utilization of arthropods for food during the summer months is seen as contributing to the maintenance of water balance during a period when the vegetation is low in water. Both populations breed in late spring, with young animals growing during the summer months, and water and sodium influx rates exceed efflux rates during this period.