bluuebunny/crossref_metadata_2025 huggingface dataset:
Maturational effects of cortisol on the exocrine abomasum and pancreas in fetal sheep
Authors: Sangild PT , Westrom BR , Silver M , Fowden AL
Published: October 2005

The role of cortisol in the prenatal development of digestive enzymes in the abomasum (prochymosin and pepsinogen) and pancreas (amylase, trypsin, chymotrypsin) has been investigated in the fetal lamb during late gestation. The abomasum and pancreas were collected from 22 unoperated control fetuses (99-145 days gestation; term, 145 +/- 2 days), from seven pairs of twins infused with either saline or cortisol for five days preceding delivery at 127-133 days, and from four 139-143-day-old fetuses adrenalectomized at 120-123 days. Developmental increases (2-8-fold) occurred in protease concentrations in the fetal abomasum and in amylase and chymotrypsin contents in the fetal pancreas. These increases paralleled the normal prepartum rise in fetal plasma cortisol. In addition, the enzyme values were significantly higher in cortisol-infused than in saline-infused fetuses (with the exception of pancreatic amylase) and were significantly lower in adrenalectomized fetuses than in control fetuses at term. The pH of abomasal fluid remained neutral (pH 6.8-8.0) during late gestation and was not affected by cortisol treatment or adrenalectomy. The results suggest that cortisol stimulates the development of the exocrine abomasum and pancreas in fetal sheep and may, thereby, increase the digestive capacity in neonatal lambs. Compared with the pig, another long-gestation species, the sheep has an early development of gastric pepsinogen but a late development of gastric acidity and pancreatic protease activities.
Genetic control of mitosis, meiosis and cellular differentiation during mammalian spermatogenesis
Authors: Wolgemuth DJ , Rhee K , Wu S , Ravnik SE
Published: October 2005

Gametogenesis in both the male and female mammal represents a specialized and highly regulated series of cell cycle events, involving both mitosis and meiosis as well as subsequent differentiation. Recent advances in our understanding of the genetic control of the eukaryotic cell cycle have underscored the evolutionarily-conserved nature of these regulatory processes. However, most of the data have been obtained from yeast model systems and mammalian cell lines. Furthermore, most of the observations focus on regulation of mitotic cell cycles. In the present paper: (i) aspects of gametogenesis in mammals that represent unique cell-cycle control points are highlighted; (ii) current knowledge on the regulation of the germ cell cycle, in the context of what is known in yeast and other model eukaryotic systems, is summarized; and (iii) strategies that can be used to identify additional cell cycle regulating genes are outlined.
A model for understanding gene regulation during spermatogenesis: the mouse testis Pdha-2 promoter
Authors: Iannello RC , Young J , Sumarsono S , Tymms M , Kola I
Published: October 2005

Spermatogenesis is a complex process requiring the coordinate expression of a number of testis-specific genes. How these genes are regulated during spermatogenesis is poorly understood. However, the elucidation of these mechanisms has significant implications for both medicine and the primary livestock industry. The delineation of this process is of particular interest and, in this study, Pdha-2, a gene which codes for the murine testis-specific isoform of the E1 alpha subunit of the pyruvate dehydrogenase complex, has been used as a model. This review focuses on current knowledge about its expression and regulation during spermatogenesis.
The sperm centrosome during fertilization in mammals: implications for fertility and reproduction
Authors: Navara CS , Simerly C , Zoran S , Schatten G
Published: October 2005

This article reviews the recent discoveries that: (1) nearly all mammals, including humans, inherit their centrosomes from their fathers; and (2) some sperm are ineffective in organizing the microtubules essential for effecting genomic union during fertilization, leading to the speculation that these sperm have centrosome defects. In addition, the molecular dissection and reconstitution of the human sperm centrosome in vitro is presented.
Sperm antigens and immunocontraception
Authors: Kerr LE
Published: October 2005

The development of novel forms of contraception is one way in which the world population crisis is being tackled. The concept of a contraceptive vaccine based on gamete-specific antigens is a particularly attractive approach. Much research has been carried out to identify sperm antigens which could be used as the immunogen. The most encouraging leads have come from groups using monoclonal antibodies to identify and characterize sperm antigens important for fertility (e.g. SP-10, PH-20 and PH-30). Identification of these molecules will also enable the development of specific tests for the diagnosis of immune infertility.
Regulation of sperm motility at the axonemal level
Authors: Gagnon C
Published: October 2005

With very few exceptions, the basic structure of the 9+2 axoneme has been well preserved over a very long period of evolution from protozoa to mammais. This stability indicates that the basic structural components of the axoneme visible by electron microscopy, as well as most of the other unidentified components, have withstood the passage of time. It also means that components of the 9+2 axoneme have sufficient diversity in function to accommodate the various types of motility patterns encountered in different species of flagella. Several of the 200 polypeptides that constitute the axoneme have been identified as components of the dynein arms, radial spokes etc. but many more remain to be identified and their function(s) remain to be determined.
Because this review deals with the regulation of flagellar movement at the axonemal level, it does not include regulation of flagella by extracellular factors unless these factors have a direct action on axonemal components. In this context, it is very important firstly to understand the structural components of the axoneme and how they influence and regulate axonemal movement. Different primitive organisms are mentioned in this review since major breakthroughs in our understanding of how an axoneme generates different types of movement have been made through their study. Despite some variations in structure and function of axonemal components, the basic mechanisms involved in the regulation of flagella from Chlamydomonas or sea urchin spermatozoa should also apply to the more evolved mammalian species, including human spermatozoa.
Synchronous multispecific spawning on coral reefs: potential for hybridization and roles of gamete recognition
Authors: Babcock R
Published: October 2005

Problems of gamete recognition in corals and other mass-spawning invertebrates are potentially great. In 'mass spawnings', closely-related species or genera commonly spawn at the same time, or within 1 or 2 h of each other, increasing the potential for hybridization. Among mass-spawning corals, most of the species involved are hermaphrodites that package the gametes in buoyant bundles that float to the sea surface before breaking up. Local hydrodynamic features frequently act to aggregate gametes from many different species into slicks where both eggs and sperm can be viable for extended periods. Other mass-spawning invertebrate taxa, such as molluscs, polychaetes and various echinoderms, do not have buoyant gametes but also spawn with a high level of synchrony. Gametes of organisms participating in these spawning events must be able to successfully recognize conspecifics. If they cannot do this, either through sperm chemotaxis or by mechanisms at the level of sperm binding and penetration, there may be high levels of gamete wastage through hybridization. Alternatively, viable hybrids may be formed, a factor that could have contributed to the evolutionary history of mass-spawning taxa, as well as to the taxonomic difficulties that have plagued the taxonomy of groups such as reef-building corals. Within some mass-spawning taxa, pre-zygotic barriers to fertilization suggest relatively recent molecular evolution at gamete recognition loci.
Workshop report: clinical CASA--the quest for consensus
Authors: Mortimer D , Aitken RJ , Mortimer ST , Pacey AA
Published: October 2005

The goals of the Workshop were to establish the current state-of-the-art in the clinical use of computer-aided sperm analysis (CASA), to identify areas of contention or confusion in the use of CASA technology, and to reach consensus on these matters to facilitate the wider use, and usefulness, of these instruments in clinical and research applications. CASA assessments of sperm morphology were not considered as they were discussed in a separate Workshop (Advanced Techniques in Sperm Preparation and Imaging) on analytical techniques. Four topics were considered: (a) CASA and semen analysis; (b) the diagnostic value of sperm kinematics in semen; (c) human sperm hyperactivation; and (d) CASA and fertility prediction. In all, 17 specific consensus points were identified.
Reproductive research on farm animals for Australia--some long-distance goals
Authors: Martin GB
Published: October 2005

In Australia, much of the research on the reproduction of farm animals has emphasised the technological manipulation of the reproductive tract, gametes and embryos. However, most of the animal production in Australia is still based on sheep and beef cattle enterprises that are managed on an extensive scale; the managers need technologies that can be easily and cheaply implemented on a large scale, and that are aimed at extensive control rather than intensive manipulation. For example, for synchronizing oestrus in the wool flocks the 'ram effect' has, and probably always will have, far more impact on extensive grazing systems than technologies based on exogenous prostaglandins or progestagens. This can also apply to the newer animal industries (such as emu farming), to human problems (such as population control), and to environmental problems (such as control of feral animals). Moreover, under the pressure of public opinion, the industries that are currently intensive are going 'free range'. In addition, surgical managerial tools (such as castration) will probably have to be abandoned or replaced. To cope with such profound influences, new types of reproductive management systems will be needed. This paper is an attempt to broaden our research horizons by developing the concept of 'control systems technologies', aimed at controlling reproductive performance rather than simply improving it. Ideas for such technologies already exist and are evident in the responses to environmental factors that our farm animals developed under the pressure of natural selection (before domestication). Stress, nutrition, photoperiod, lactation, and socio-sexual cues (e.g. pheromones) can all exert profound effects on reproductive activity. We already have a good grasp of the final common pathway through which the brain responses to these factors affect gonadal activity, namely the hypothalamic system that generates pulses of gonadotrophin-releasing hormone. All we need to do is learn how the major environmental cues exert their impact on the systems that control the final common pathway. When we understand them, we shall be able to manipulate them. This is not too speculative; we already have several technologies that take advantage of this approach, including steroid-based contraceptives, the 'ram effect', a vaccine-based antifertility treatment for rangeland cattle and the melatonin formulation used to control seasonal breeding in sheep. These and the other pathways linking environmental inputs to reproductive output are waiting to be explored, explained and exploited.
From uncommitted to committed embryonic cells: opportunities for their study and manipulation
Authors: Wales RG
Published: October 2005

This paper offers a broad review of the methodologies used for the study of embryonic development and for the manipulation of embryonic cells. It was written in the context of the silver anniversary of the Australian Society for Reproductive Biology and places particular emphasis on the achievements of Australian scientists in this field. It has attempted to place recent advancements in some historical perspective, to examine the present 'state of the art' in reproductive technologies and to consider future directions.
DNA synthesis and prostaglandin secretion by bovine endometrial cells as regulated by interleukin-1
Authors: Davidson JA , Tiemann U , Betts JG , Hansen PJ
Published: October 2005

Interleukin-1 (IL-1) is a pleiotropic cytokine which has been implicated in the regulation of endometrial function through alterations in proliferation, protein synthesis, and prostaglandin secretion. The objectives of this study were to determine if recombinant bovine interleukin-1 beta (rbIL-1 beta) stimulated prostaglandin secretion and altered the proliferation of bovine endometrial epithelial and stromal cells. Uterine flushes were also evaluated by enzyme-linked immunosorbent assay (ELISA) to determine if IL-1 beta was present in the bovine uterus. Effects of rbIL-1 beta (1-1000 ng mL-1) on DNA synthesis by endometrial epithelial and stromal cells prepared from cows at Days 11, 14 and 17 after oestrus were determined by monitoring uptake of [3H]thymidine into DNA. Incorporation of [3H]thymidine by epithelial cells was not affected by IL-1, but rbIL-1 beta inhibited [3H]thymidine incorporation by stromal cells. Secretion of prostaglandin E2 (PGE2), PGF2 alpha, and 13,14-dihydro 15-keto PGF2 alpha (PGFM) by epithelial and stromal cells was increased by rbIL-1 beta. Uterine flushes collected on Days 11, 14 and 17 after oestrus were positive for IL-1 regardless of pregnancy status, whereas flushes from pregnant cows on Day 25 and Day 30 did not have any detectable IL-1. In conclusion, IL-1 can be considered as a local regulatory factor of the bovine endometrium because of its presence within the uterus and its ability to alter DNA synthesis and prostaglandin secretion of endometrial cells.
Effects of prostaglandins and oestradiol-17 beta on oxytocin binding in cultured bovine luteal cells
Authors: Okuda K , Uenoyama Y , Miyamoto A , Okano A , Schweigert FJ , Schams D
Published: October 2005

The aim of the investigation was to evaluate the possible action of prostaglandins (PGs) and oestradiol-17 beta (oestradiol) on the specific binding for oxytocin in bovine luteal cells. Cultured cells of bovine corpora lutea at the mid-luteal stage (Day 8-12 of the oestrous cycle) were examined for the presence of oxytocin receptors by a radioreceptor assay using the 125I-labelled oxytocin antagonist [d(CH2)5,Tyr(Me)2,Thr4,Tyr-NH29]-vasotocin (125I-OVT) as a ligand. The cells were cultured for 48 h in total. In the final 15 h of culture, the luteal cells were exposed to varying concentrations of PGF2 alpha, PGE2 and/or oestradiol. After culture, the cells were incubated with 37,000 dpm (0.5 nM) 125I-OVT with or without 100 nM of unlabelled oxytocin. PGF2 alpha, at 10(-8) M and 10(-7) M, stimulated the specific binding for oxytocin to levels as high as 128% of controls (P < 0.01); by contrast, PGE2, PGI2 or oestradiol had no effect on oxytocin binding. Scatchard analysis revealed that the concentration of oxytocin receptors was increased (P < 0.05) from 6.7 fmol micrograms-1 DNA to 8.4 fmol micrograms-1 DNA by stimulation with 10(-7) M of PGF2 alpha without changing the binding affinity. No further increase in the specific binding was observed when PGF2 alpha was used in combination with PGE2, PGI2 or oestradiol at a concentration of 10(-7) M. Addition of indomethacin (28 microM) resulted in the inhibition of PGF2 alpha secretion, coinciding with a significant decrease in oxytocin binding (P < 0.01). However, addition of arachidonic acid (100 microM) caused a significant increase in the secretion of PGF2 alpha and the specific binding for oxytocin concomitantly (P < 0.05). When the protein kinase C (PKC) activity of the luteal cells was inactivated by preincubating cells for 13 h with 1 microM phorbol 12-myristate 13-acetate before PGF2 alpha stimulation, the specific binding for oxytocin was not affected by PGF2 alpha stimulation (10(-7) M) in the final 15 h of culture. These data suggest that PGF2 alpha may be one of the potent regulators for luteal oxytocin receptors in a paracrine and/or autocrine manner, and that its action is mediated by PKC.
Sulfated glycoprotein-1 (SGP-1) expression in ovine endometrium during the oestrous cycle and early pregnancy
Authors: Spencer TE , Graf GH , Bazer FW
Published: October 2005

This study determined effects of day of oestrous cycle and early pregnancy on sulfated glycoprotein-1 (SGP-1) expression in ovine endometrium. A 364-bp clone of the ovine SGP-1 mRNA was amplified from reverse transcribed Day-15 cyclic endometrial mRNA using the polymerase chain reaction (PCR) and primers specific for the rat SGP-1 mRNA sequence. Nucleotide sequence of the ovine SGP-1 cDNA shared significant identity with rat SGP-1 and human prosaposin. Ewes (n = 40) were hysterectomized on either Day 1, 6, 11, 13 or 15 of the oestrous cycle or on Day 11, 13, 15, 17 or 25 of early pregnancy. Total cellular RNA was isolated from endometrium and subjected to Northern and slot blot hybridization analyses using an antisense cRNA probe transcribed from the ovine SGP-1 cDNA clone. A single 2.6-kb mRNA transcript was detected by Northern hybridization analyses. Slot blot hybridization analyses indicated that steady-state levels of endometrial SGP-1 mRNA varied during the oestrous cycle (cubic, P < 0.02) and increased between Day 11 and Day 25 of early pregnancy (linear, P < 0.01). On Days 11, 13 and 15, endometrial SGP-1 mRNA levels were greater in pregnant ewes than in cyclic ewes (day x pregnancy status, P < 0.01). Immunohistochemical localization of SGP-1 in uterine tissues with rabbit anti-rat SGP-1 antibody revealed intense immunoreactivity associated primarily with the endometrial epithelium. These results indicate that the ovine endometrium expresses SGP-1, a prosaposin, and that SGP-1 expression varies during the oestrous cycle and is enhanced by the conceptus. The presence of SGP-1 in the endometrium suggests intracellular and extracellular roles for this protein in glycosphingolipid metabolism or transport in the uterine environment.
Effect of glucose in the culture medium on development of horse oocytes matured and microfertilized in vitro
Authors: Azuma T , Choi YH , Hochi S , Oguri N
Published: October 2005

The development of in-vitro matured and microfertilized horse oocytes was examined in vitro. Fertilized oocytes were produced by 20-h insemination of in-vitro matured and partially zona-removed oocytes with frozen spermatozoa that had been treated with caffeine/calcium ionophore A23187 (fertilization rate 34.2%, monospermy rate 76.9%). Embryonic development was assessed by the number of nuclei stained with Giemsa solution. In Experiment 1, a continuous 8-day culture of the microfertilized oocytes in TCM199 or modified synthetic oviduct fluid (m-SOF) supplemented with 10% fetal bovine serum or 0.1% polyvinyl alcohol (PVA) in 5% O2, 5% CO2 and 90% N2 resulted in very few embryos developing beyond the 8-cell stage. In Experiment 2, the effects of different glucose concentrations (0, 0.5, 5.5 mM) in m-SOF/PVA during Days 1-4 and Days 5-8 of culture were examined. Proportions of oocytes having more than one nucleus ranged from 17.7% to 44.7% among the combinations of glucose concentrations. Supplementation with glucose at 0.5 mM during Days 1-4 followed by 5.5 mM during Days 5-8 resulted in the best embryo development; 12/55 (21.8%) nuclei-positive oocytes developed to the 8-16-cell stage, 11 (20.0%) developed to the 17-50-cell stage, and 5 (9.1%) comprised more than 50 cells and were assumed to be at the morula stage.
Uterine receptivity to the artificial deciduogenic agent, concanavalin A, in pseudopregnant QS mice
Authors: Sakoff JA , Murdoch RN
Published: October 2005

The present study was undertaken to define the 'window' of uterine receptivity in the Quackenbush Special (QS) mouse as gauged by the capacity of the uterus to mount a decidual cell reaction (DCR) in response to the lectin Concanavalin A (Con A). Con A failed to induce a DCR when administered into the uterine lumen on Day 3 of pseudopregnancy (Day 1, copulatory plug). However, it was partially effective between 0600 hours and 0900 hours on Day 4, totally effective between 1200 hours on Day 4 and 1500 hours on Day 5, and virtually ineffective from this time onwards. When uteri were examined at specific time intervals after stimulation with the lectin at 1200 hours on either Day 4 or Day 5, uterine weights were significantly greater in animals stimulated on Day 5. The greatest rate of uterine growth began on Day 6 irrespective of whether Con A was administered on Day 4 or Day 5. Animals stimulated on Day 5 of pseudopregnancy produced a significantly larger oedema response and an earlier vascular permeability response than those stimulated on Day 4. The results indicate that: (i) Con A is deciduogenic in pseudopregnant QS mice; (ii) uterine receptivity in these animals spans a minimum period of 27 h beginning at midday on Day 4 of pseudopregnancy; and (iii) the uterus displays different patterns of growth, oedema, and vascular permeability following stimulation at different times during the receptive period.
Acute and short-term actions of serotonin administration on the pituitary-testicular axis in the adult rat
Authors: Hedger MP , Khatab S , Gonzales G , de Kretser DM
Published: October 2005

In this study, adult male rats were injected intraperitoneally with a single dose of serotonin (5-hydroxytryptamine, 5HT; 10 mg kg-1 bodyweight) for 2 h or 18 h, or daily with graded doses of 5HT (0.1-10 mg kg-1) for four days before being killed. Serum and testicular interstitial fluid (IF) concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone and immunoreactive-inhibin were measured by radioimmunoassay, and one testis was removed for histological examination. At 2 h after a single injection, 5HT caused a significant inhibition of serum concentrations of LH and inhibin, recovered IF volume and intratesticular testosterone concentrations; testis weight and serum concentrations of testosterone and FSH were unaffected. At 18 h after injection, all parameters had returned to normal, with the exception of intratesticular testosterone concentration which remained lower than normal. The lowest 5HT dose (0.1 mg kg-1) had no effect on any parameter following four daily injections. At a dose of 1.0 mg kg-1 5HT, there was a four-fold increase in the concentration of serum LH, but testis weight, recovered IF volume, testosterone and inhibin concentrations and serum concentrations of FSH were not significantly affected. At the highest dose of 5HT (10 mg kg-1) after four daily injections, testis weight decreased, and IF volume increased nearly three-fold. Testis concentrations of inhibin and serum testosterone were reduced, whereas serum concentrations of both LH and FSH were elevated; intratesticular testosterone concentrations did not differ from controls. Only at the highest dose of 5HT was disruption to the seminiferous epithelium observed, with focal damage ranging in severity from increased degeneration of spermatogenic cell profiles, to complete loss of the germinal epithelium; however, many tubule profiles displayed completely normal spermatogenesis. The acute IF volume reduction and spermatogenic disruption in 5HT-treated rats were consistent with localized ischaemia due to constriction of the testicular arterial supply. The eventual increase in IF volume observed after 5HT treatment appeared to be secondary to the loss of germ cells. Although 5HT also inhibited pituitary LH release and Leydig cell steroidogenesis, these effects appeared to play only a minor role in the induction of spermatogenic damage.
Ultrastructure and motility of spermatozoa in macropodid and potoroidid marsupials
Authors: Taggart DA , Leigh CM , Schultz D , Breed WG
Published: October 2005

In order to gain some understanding of the significance of the morphological features of spermatozoa within the Macropodoidea, the motility of spermatozoa from two macropodids (Petrogale xanthopus and Dendrolagus matschiei) and the motility, number and distribution of spermatozoa from three potoroidids (Aepyprymnus rufescens, Bettongia penicillata and Potorous tridactylus) were examined. Sperm were collected by electro-ejaculation or from the cauda epididymides. Epididymides from the potoroidids were divided into 12 regions. One epididymidis per animal was fixed for light and transmission electron microscopy and, on the contralateral side, the number of sperm, their distribution and motility were determined. In general, spermatozoa of all five species differed markedly from one another in head and flagella dimensions. Spermatozoa from B. penicillata and P. tridactylus were significantly longer and broader and had a smaller acrosome relative to head length, and there was a radial displacement of dense fibres. They also progressed more rapidly in standard culture media. Spermatozoa from at least three species were able to alter their motility pattern in vitro as media viscosity increased. Sperm movement in all species appeared to be restricted to one plane and showed no evidence of rotation, whereas lateral head displacement was often pronounced; there was no evidence of a sinusoidal mode of progressive motility. Testicular and epididymal sperm numbers in A. rufescens and P. tridactylus were relatively high (approximately 17.5-50 x 10(6)). In A. rufescens, approximately 69% of all epididymal sperm were located in the cauda epididymidis compared with approximately 40% in P. tridactylus. This study demonstrated that marked radial displacement of the dense fibres is probably closely associated with the ability to develop a sinusoidal mode of progressive movement, and that this feature of the sperm tail structure is not just linked with sperm size. Sperm size, however, is associated with sperm velocity.
Metabolic assessment of wallaby blastocysts during embryonic diapause and subsequent reactivation
Authors: Spindler RE , Renfree MB , Gardner DK
Published: October 2005

The metabolism of tammar wallaby (Macropus eugenii) blastocysts was analysed by means of quantitative fluorescence microscopy during embryonic diapause and 2, 3, 4, 5, 8 and 10 days after reactivation to determine nutrient preferences during metabolic reactivation of the blastocyst. The surface area of quiescent blastocysts was 0.16 +/- 0.02 mm2 (mean +/- s.e.m.), and increased to 0.44 +/- 0.04 mm2 (P < 0.05) by Day 8 after removal of the sucking stimulus of the pouch young (RPY). Day-10 blastocysts, analysed over two successive breeding seasons, were significantly different in size from each other (Group A, 1992: 4.44 +/- 1.47 mm2; Group B, 1993: 18.87 +/- 4.62 mm2; P < 0.01), and both groups were significantly different in size from diapausing blastocysts (P < 0.01). There was no significant difference in carbohydrate uptake or production by blastocysts during the first five days after RPY. Glucose uptake by blastocysts recovered 8 days after RPY (61.9 +/- 30.0 pmol embryo-1 h-1) was significantly greater than that by Day-0 blastocysts (17.9 +/- 5.5 pmol embryo-1 h-1) and glucose uptake by both groups of Day-10 blastocysts (Group A, 174.0 +/- 28.4 pmol embryo-1 h-1; Group B, 616.0 +/- 239.0 pmol embryo-1 h-1) was significantly different from that by Day-0 blastocysts (P < 0.01). Pyruvate uptake by Day-10 blastocysts (Group A, 46.0 +/- 32.2 pmol embryo-1 h-1; Group B, 250.0 +/- 136.0 pmol embryo-1 h-1; P < 0.01) increased significantly compared with that by Day-0 blastocysts (6.4 +/- 1.6 pmol embryo-1 h-1; P < 0.01). Lactate production by Day-10 blastocysts (Group A, 186.7 +/- 30.3 pmol embryo-1 h-1; Group B, 285 +/- 129 pmol embryo-1 h-1; P > 0.01) was also significantly different from that by quiescent blastocysts (41.20 +/- 9.6 pmol embryo-1 h-1). There was a linear relationship between surface area and glucose uptake and surface area and pyruvate uptake (r2 = 0.965 and r2 = 0.971 respectively). Despite increases in carbohydrate uptake, there was a proportional decrease in lactate production indicating an increase in oxidative metabolism during reactivation. This suggests that there may be a metabolic switch at, or around, Day 5 after RPY.
Late fetal development and selective resorption in Saccostomus campestris (cricetidae)
Authors: Westlin LM , Soley JT , van der Merwe NJ , van Dyk YJ
Published: October 2005

When female Saccostomus campestris are stressed during pregnancy they may resorb part of the litter. Resorption can take place on more than one occasion during the same pregnancy without affecting the development of the rest of the litter. The last resorption may be initiated as late as 72-48 h before parturition. No other rodents with a similar gestation appear to resorb at this stage. Resorbing fetuses are isolated within uterine compartments from viable fetuses. Ossification occurs at a comparatively late stage of pregnancy in Saccostomus campestris, and there is a lag-period in fetal growth exactly 72-48 h before parturition. These factors may facilitate late resorption in this species. Factors that may cause stress in this species are most likely environmental; in the present study, dipping of the animal colony to treat for a mite infestation may have induced resorption in some of the females.
Ova recovery, and in vivo and in vitro fertilization of ova from RU486-treated PMSG/hCG-primed mice
Authors: Juneja SC , Dodson MG
Published: October 2005

In this study, the effect of preovulatory treatment with RU486, for different lengths of time and combinations of days, was shown in terms of the ova recovery, in vitro fertilization of recovered ova, in vivo fertilization and quality of fertilized ova in PMSG/hCG-primed mice. Female mice were injected with PMSG followed 48 h later by hCG to induce superovulation. Mice received RU486 (20 mg kg-1 body wt) for 1, 2, 3 and 4 preovulatory days (in different combinations). Ovulation, as judged by the number of ova recovered at 14 to 14.5 h post-hCG, was depressed (P < 0.001), and the total number of embryos recovered at 40 h post-hCG was low (P < 0.001), in mice receiving a minimum of two consecutive days' treatment (day before PMSG + day of PMSG; or day before hCG + day of hCG) of RU486 under study. Quality of ova recovered from RU486-treated animals was not affected as determined by their ability to become fertilized in vitro. In vivo fertilization, as determined by the recovery of 2-cell embryos, was suppressed significantly in mice treated with RU486 for four consecutive preovulatory days (P < 0.001). A varied degree of premature compaction was observed in 2-cell embryos immediately upon retrieval from the oviduct of RU486-treated animals, the effect being most marked in mice receiving RU486 for a minimum of two consecutive preovulatory days under study. It is suggested that premature compaction of early embryos was under the continuous influence of the luminal environment of treated animals and might be the reason for their degeneration at later stages in the reproductive tract and for a low pregnancy rate as shown by other studies. Compacted embryos decompacted within 15-30 min in vitro and led to normal blastocyst formation in vitro in RU486-free culture medium.
Circulatory responses to acute asphyxia in intact and chemodenervated fetal sheep near term
Authors: Jensen A , Hanson MA
Published: October 2005

The study concerned the role of the carotid sinus nerves in the effects of acute asphyxia on the fetal circulation. Fetal sheep (n = 12) were instrumented at approximately 130 days' gestation for placement of fetal vascular catheters and an occluder around the maternal descending aorta below the renal arteries. In 7 fetuses the carotid sinus nerves were cut. On the third post-operative day, asphyxia was produced by occluding the maternal aorta for 2 min and fetal blood flows were determined by the radio-labelled microsphere technique. In control, there were no differences between intact and denervated fetuses in blood gases, cardiovascular variables or blood flows, with the exception of lower blood flows to the cerebrum, caudate nucleus, kidney, skeletal muscle and scalp in the denervated group (P < 0.01). Fetal heart rate, cardiac output, stroke volume and the rate-pressure product were similar in asphyxia, with the exception that mean arterial pressure was lower in denervated fetuses after 2 min of asphyxia. Noradrenaline and adrenaline concentrations peaked at 2 min, then declined, the increase being smaller (P < 0.01) in denervated fetuses. Regional blood flows were similar in the two groups. Vascular resistance was lower in the placenta and abdominal aorta at 2 min in denervated fetuses. There were few differences in organ blood flows between intact and denervated fetuses, and the differences in flow in normoxia for the kidney, skeletal muscle and scalp (but not cerebrum, caudate nucleus and hippocampus) disappeared in asphyxia. This study confirms that section of the carotid sinus nerves has little effect on arterial blood pressure and fetal heart rate in normoxia but produces small differences in the responses to acute severe asphyxia, e.g. in arterial blood pressure and catecholamines, giving evidence for the operation of chemoreflexes. The lower blood flow to cerebrum, caudate nucleus, kidney, skeletal muscle and scalp in denervated fetuses in normoxia suggests a tonic vasodilatation, part of the drive for which comes from carotid chemo- or baroreceptors.
Identification of and developmental changes in transient outward current in embryonic chick cardiomyocytes
Authors: Satoh H
Published: October 2005

Identification and developmental changes in the transient outward current (I(to)) in isolated embryonic chick ventricular cells (3, 10 and 17 days old) were examined using a whole-cell voltage clamp technique. Experiments were performed at room temperature (22 degrees C). Test pulses were applied between -40 and +50 mV from a holding potential of -60 mV. The I(to) was present (but small) and increased during development; the current density of I(to) at +40 mV was 3.5 +/- 0.5 pA/pF (n = 7) in 3-day cells, 4.2 +/- 0.9 pA/pF (n = 5) in 10-day cells, and 17.1 +/- 1.6 pA/pF (n = 5) in 17-day-old cells. The average capacitances also changed with developmental age; 12.0 +/- 2.0 pF (n = 8) in 3-day cells, 10.8 +/- 2.2 pF (n = 7) in 10-day cells, and 8.6 +/- 2.3 pF (n = 7) in 17-day cells. The I(to) was not always observed in all the prepared cells, and the number of cells possessing I(to) increased during development. The threshold potential was -30 mV in 17-day cells, and appeared to be displaced to more negative potential with developmental age. The time to peak decreased during development: 10.6 +/- 1.1 ms (n = 4) in 3-day cells, 6.7 +/- 0.5 ms (n = 5) in 10-day cells, and 5.4 +/- 0.6 ms (n = 5) in 17-day cells. The time decay of the inactivation phase for the I(to) had two exponentials; the fast component was increased by about 3-fold in 17-day cells, and the slow component was decreased by about 14% in both 10- and 17-day cells, as compared to 3-day cells. Addition of 3 mM 4-aminopyridine (4-AP) inhibited I(to) at +50 mV by 81.9 +/- 2.3% (n = 4, P < 0.001). These results indicate that the I(to), voltage-dependent and 4-AP-sensitive, exists even in young embryonic cardiomyocytes (but not in all cells), and increases during development, resulting in modulation of the action potential configuration.
Concentration-dependent effects of cocaine on monoamine-induced constriction of cannulated, pressurized cerebral arteries from fetal sheep
Authors: Schreiber MD , Madden JA , Covert RF , Hershenson MB , Torgerson LJ
Published: October 2005

Drugs, such as cocaine, which may alter monoamine neurotransmitter responsiveness, could adversely affect the regulation of cerebral vasculature. Cocaine exhibits at least two mechanisms that may alter vascular responsiveness: synaptic uptake inhibition, which may augment response to stimulation, and Na+ channel inhibition, which may attenuate response. To help elicit the concentration-dependent effects of cocaine, the effects of cocaine on monoamine neurotransmitter responsiveness were studied in vitro on fetal sheep cerebral arteries (120 days gestation). The changes in diameter of segments of cannulated, pressurized fetal sheep cerebral artery were measured with a videomicroscaler system. Cumulative concentration-response curves (10(-10) to 10(-4)M) were generated for two monoamines, norepinephrine and serotonin, alone and in the presence of cocaine (10(-5) or 10(-4)M). Cocaine caused concentration-dependent alteration of response. At 10(-4)M, cocaine attenuated mean maximal norepinephrine-induced vasoconstriction 46.2% (P < 0.05). At 10(-5)M, cocaine increased sensitivity to norepinephrine (log EC50 decreased -6.63 +/- 0.09 to -7.11 +/- 0.03) and to serotonin (log EC50 decreased -7.24 +/- 0.04 to -7.81 +/- 0.09) (P < 0.05). The higher concentration of cocaine (10(-4)M) did not significantly decrease log EC50 norepinephrine. Cocaine (10(-4)M) also attenuated the response to single doses of norepinephrine (10(-6)M) and serotonin (10(-6)M) by 26.5% and 40.0%, respectively (P < or = 0.05). It is concluded that cocaine has concentration-dependent effects on vasoconstriction of the fetal sheep cerebral artery in vitro. This cocaine-induced alteration of cerebral vascular responsiveness to monoamines may be important in the regulation of fetal cerebral blood flow.
Regulation of human placental fetal vessel tone: role of nitric oxide
Authors: King RG , Gude NM , Di Iulio JL , Brennecke SP
Published: October 2005

Factors affecting fetal vessel resistance have been studied in vitro in bilaterally perfused lobules of human placentae. Potent and efficacious constrictors in this preparation (in order of potency) include endothelin-1 > the thromboxane mimetic U46619 > endothelin-3 > prostaglandin F2 alpha. Inhibitors of eicosanoid synthesis did not affect fetal vessel basal perfusion pressure, nor did they potentiate the effects of the vasoconstrictor U46619. In contrast, the nitric oxide inhibitors N omega-nitro-L-arginine (NOLA), haemoglobin and methylene blue all increased fetal vessel basal perfusion pressure and also increased U46619-induced constriction. Similarly, NOLA markedly potentiated the constrictor effects of endothelin-1, angiotensin II, 5-hydroxytryptamine and bradykinin. These studies therefore provide evidence that NO is important in the maintenance of low basal fetal vessel impedance and also reduces the effects of a number of vasoconstrictor autacoids. Nitric oxide synthase (NOS) activity of human placental homogenates has been measured and shown to be mainly calcium-dependent. Human placental NOS activity was not affected by labour state but was reduced in pre-eclampsia. No evidence was found that in pre-eclampsia raised concentrations of the endogenous NOS inhibitor asymmetric dimethylarginine were responsible for the reduced placental NOS activity. Hence, these studies provide evidence that NO is an important endogenous dilator of the fetal vessels of the human placenta and that reduced NOS activity could contribute to the pathogenesis and/or effects of pre-eclampsia.
Interaction between pregnancy-induced bioactive peptides and the placental proteases
Authors: Mizutani S , Goto K , Mizuno K , Itakura A , Kurauchi O , Kikkawa F , Tomoda Y
Published: October 2005

Studies have shown that placental proteases metabolize vasoactive peptides, possibly derived from the fetus, and protect the exchange of peptide hormones across the placenta in order to maintain feto-placental homeostasis. Changes in maternal serum protease activities were useful for monitoring pre-eclampsia and predicting the onset of labour. The study showed that possible role of oxytocinase in the maintenance of gestation and the possible involvement of angiotensinase in the attenuated pressor responses to angiotensin II during pregnancy, respectively. In addition, the ratio of peak systolic over least diastolic pressure (S/D) of uterine or umbilical artery assessed by the Doppler technique was closely correlated with the concentrations of maternal serum proteases in pre-eclampsia, which suggested that placental proteases might control utero-placental circulation via the regulation of concentrations of vasoactive peptides in uteroplacental circulation.
Oxytocin in human intrauterine tissues at parturition
Authors: Mauri A , Argiolas A , Ticconi C , Piccione E
Published: October 2005

The recent detection of oxytocin (OT) mRNA in human gestational tissues suggests that OT may be locally synthesized and released to act on the uterus as a local mediator in the mechanism of parturition. In order to investigate this possibility the OT immunoreactive (I.R.) content was examined directly in placental decidua and amniochorial membranes after term and preterm delivery and in their culture media at term gestation. I.R.OT concentrations were also measured in maternal, retroplacental and umbilical plasma as well as in amniotic fluid in the presence or the absence of labour. Low I.R.OT concentrations (below 15 fmol g-1 wet tissue) were found in both amniochorial membranes and placental decidua. Moreover, whereas in amniochorion they were higher (P < 0.05) after preterm than term spontaneous parturition, in decidua they were higher (P < 0.05) after term than preterm vaginal delivery. Detectable amounts (below 15 fmol g-1 wet tissue per h) of I.R.OT were also found in culture media from explants of the above tissues. Among all the examined maternal and fetal fluids a rise in I.R.OT content at parturition was detected only in the amniotic liquor (P < 0.05). These findings suggest that I.R.OT concentrations in intrauterine tissues are very low; however, considering that OT is the most potent endogenous uterotonic agent, OT as such concentrations might play a paracrine function in the biochemical events leading to human parturition. Therefore, a role for amniotic OT in parturition can not be excluded.
Parathyroid hormone-related protein (PTHrP) concentrations in human amniotic fluid during gestation and at the time of labour
Authors: Wlodek ME , Ho PW , Rice GE , Moseley JM , Martin TJ , Brennecke SP
Published: October 2005

To establish the changes associated with gestational age and labour status in parathyroid hormone-related protein (PTHrP) concentrations in the amniotic fluid, human amniotic fluid was collected from non-labouring and labouring women at < 37 weeks of gestation (preterm) and at term (> or = 37 weeks). PTHrP was assayed by a specific N-terminal radioimmunoassay. PTHrP concentrations in amniotic fluid obtained from non-labouring women were significantly lower at preterm (15-36 weeks; 14.1 +/- 2.5 pmol L(-1); n = 11) than at term (37-42 weeks; 39.3 +/- 7.6 pmol L(-1); n = 16; P < 0.0009). Concentrations of PTHrP in amniotic fluid obtained from labouring women were also significantly lower at preterm (27-36 week; 12.2 +/- 4.7 pmol L(-1); n = 4; P < 0.01) than at term (37-42 weeks; 63. 8 +/- 19.6 pmol L(-1); n = 9). There were no significant changes in concentration associated with labour status, either at preterm or at term. The physiological significance of elevated amniotic fluid concentrations of PTHrP has yet to be established, but the data are consistent with the suggestion that PTHrP plays a role in fetal membrane function during late gestation.
Umbilical venous guanosine 3',5'-cyclic phosphate (cGMP) concentration increases in asphyxiated newborns
Authors: Itoh H , Sagawa N , Hasegawa M , Mori T , Suga S , Mukoyama M , Yoshimasa T , Itoh H , Nakao K
Published: October 2005

Guanosine 3',5'-cyclic phosphate (cGMP) is known to be the second messenger of natriuretic peptides and nitric oxide (NO). To investigate the involvement of natriuretic peptides in the regulation of the feto-placental circulation, specific radioimmunoassays were used to measure the concentrations of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP) and cGMP in the umbilical venous plasma of normal and asphyxiated newborns. The plasma concentrations of ANP, BNP and cGMP in asphyxiated newborns were 48.3 +/- 12.9 pm, 24.5 +/- 9.4 pm and 4.4 +/- 1.6 nM (mean +/- s.e.m., n = 10), respectively. These values were significantly higher than those in the normal newborns (17.4 +/- 1.9 pm, 4.7 +/- 1.0 pm, and 0.78 +/- 0.14 nM, respectively). Moreover, the expression of both ANP-A and ANP-B receptor, biologically active receptors for natriuretic peptides, was detected in term human placenta by Northern bolt analysis. The expression of natriuretic peptide receptors was further confirmed by binding assay using [125I]-labelled ANP and solubilized crude membrane preparations of placental tissue. These findings suggest that cGMP is produced in the placenta, at least partly, by the action of ANP and BNP secreted from fetal heart, in pathophysiological conditions such as fetal hypoxia.
Placental nitric oxide metabolism
Authors: Sooranna SR , Morris NH , Steer PJ
Published: October 2005

There is increasing evidence that nitric oxide (NO) has a role in pregnancy. NO is synthesized from L-arginine by NO synthase (NOS), which can exist either as a calcium-dependent or a calcium-independent isoform of the enzyme. Both isoforms are present in placental villi and the authors have measured NOS activities in tissues from early and term normal, pre-eclamptic and growth-retarded pregnancies. Higher activities were seen in first trimester placental villi than at term. An impairment of NO metabolism occurred in placental villi from pre-eclamptic and growth-retarded pregnancies. Smoking also results in decreased NOS activities in the placental villi, suggesting that problems attributed to smoking during pregnancy could be linked to NO metabolism. Polyamines arginine and citrulline (all of which are important metabolites in the NO pathway) were also measured in placental villous tissues. The data presented in this review article are from work carried out in the authors' laboratories and suggest that alterations in the placental arginine-NO pathway may not only play a role in the physiological changes of advancing gestation but may also contribute to the pathophysiology of pre-eclampsia and fetal growth retardation.
Transfer of immunoglobulin G across the isolated perfused human placental lobule
Authors: Duncan JI , Armstrong-Fisher SS , Urbaniak SJ , Abramovich DR , Whiting PH , Page KR
Published: October 2005

This study demonstrates that IgG transfer in vitro across the isolated perfused human placental lobule can be successfully studied by using natural forms of IgG. The transfer of anti-RhD IgG (anti-D) was measured in the presence and absence of intravenous immunoglobulin (IVIgG). When anti-D and IVIgG were present alone each crossed the placenta at about the same rate, but when both forms were present at the same time the movement of one interfered with the movement of the other. This pattern of transfer is consistent with receptor-mediated transcytosis. The interactions of IgG with trophoblastic transporters may therefore be studied without the complications that might arise from the use of conventionally labelled molecules.