bluuebunny/crossref_metadata_2025 huggingface dataset:
The epididymis and sperm maturation: a perspective
Authors: Amann RP , Hammerstedt RH , Veeramachaneni DN
Published: October 2005

In common mammals, sperm leaving the testis are incapable of fertilizing a female gamete. Sperm have limited biosynthetic capability and need to minimize demand for ATP. Hence, modification of sperm to achieve their maturation requires pre-programmed cleavage of integral molecules (planned self-modification) and remodelling by action of molecules found in the suspending fluids. Most of these biocatalysts are secreted by a series of specialized regions in the epididymal epithelium, but some are provided in seminal plasma. The role of the epididymis in sperm maturation is postulated to be 'setting a series of triggers' each capable of initiating cellular changes either at emission or near or in the oocyte, and 'setting a safety' for each trigger to prevent premature occurrence of the event. The attributes required in a spermatozoon for in vitro fertilization and natural mating are different, and their expression is dependent on the site of sperm sampling. Some attributes needed for fertility are probably like an on-off switch, whereas others probably allow a gradually reduced probability of success before going to the off position (analogous to a conventional light switch and a dimmer-type light switch). All essential attributes of a spermatozoon must be expressed in a 'combined effective amount' for that cell to be fertile. Because of mixing, in any segment of the epididymal duct the population of sperm is heterogeneous in age and biological status. Thus, when assessing sperm maturation it is necessary to establish the proportion of sperm that has completed and retained all steps of maturation necessary to achieve fertilization of oocytes under the conditions imposed. In a normal animal, most sperm leaving the epididymis have a 'combined effective amount' of attributes, and the population has a high fertilizing potential.
Metabolism of glucose by vesicles derived from sheep trophoblast and embryonic discs
Authors: Du ZF , Wales RG
Published: October 2005

Samples of trophoblast recovered from the sheep conceptus on Day 13 of pregnancy formed spherical vesicles during culture in medium 199. These continued to expand and increase in dry weight over the next 6 days in vitro. After 6 days' culture, the metabolism of glucose by these vesicles was compared with that of Day-13 and Day-19 fresh trophoblastic tissue. The production of CO2 and lactate by vesicles was similar, although not identical, to production by Day-13 fresh tissue and did not exhibit the marked decrease in glucose catabolism seen in Day-19 trophoblast. The tissue from vesicles reacted to reduction in oxygen tension in a manner similar to the reaction of fresh tissue, with decreased glucose oxidation and increased glycolysis. The activity of the pentose phosphate pathway in vesicles was higher, and the activity in Day-19 fresh tissue was much lower, than that in Day-13 fresh trophoblast. Incorporation of glucose into the intracellular biochemical pools by vesicles was similar to incorporation into Day-13 fresh tissue. Limited observations were also made with vesicles derived from embryonic disc. Production of CO2 by these vesicles was intermediate between that detected in fresh Day-13 and Day-19 embryonic tissue. There were not significant differences in lactate production between fresh and cultured samples of embryonic tissue. These results show that vesicles formed in vitro remain metabolically active but do not mimic the biochemical changes seen in the tissue during development in vivo.
Metabolism of pyruvate by pre-elongation sheep embryos and effect of pyruvate and lactate concentrations during culture in vitro
Authors: Thompson JG , Bell AC , Pugh PA , Tervit HR
Published: October 2005

In the first of two experiments, utilization of [1-14C]pyruvate by 8-cell and blastocyst-stage embryos derived in vivo was examined during a 3-h incubation in HEPES-buffered synthetic oviduct fluid (SOF) medium in the presence or absence of other substrates. In the second, a factorial design examined the effect of pyruvate (0, 0.33, 1.0 and 3.3 mM) and lactate (3.3, 10 and 33 mM) on development of 1- and 2-cell sheep embryos cultured in vitro in a modified SOF medium (containing glucose, glutamine and modified Eagle's medium non-essential amino acids). Peak utilization of [1-14C]pyruvate was unaffected by the presence or absence of other energy substrates. In contrast, rate of utilization was affected by the addition of other energy substrates, with half maximal utilization occurring at either 0.4 +/- 0.2 mM or 1.2 +/- 0.2 mM for 8-cells and either 0.2 +/- 0.2 mM or 1.3 +/- 0.3 mM for blastocysts when incubated in the absence or presence of other energy substrates respectively. In the second experiment the proportion of embryos developing to blastocysts was inhibited by high lactate levels (P < 0.001), but was generally not affected by pyruvate concentration. However, there was a significant interaction (P < 0.001) between pyruvate and lactate when both were present in the medium. At 0.33 mM pyruvate, 3.3 mM lactate supported good development (83 +/- 8% blastocysts) whereas 10 mM lactate supported less development (50 +/- 11%). However, at the higher levels of pyruvate this effect was lost.(ABSTRACT TRUNCATED AT 250 WORDS)
The placenta as hypothalamus and pituitary: possible impact on maternal and fetal adrenal function
Authors: Waddell BJ
Published: October 2005

The human placenta appears capable of providing trophic support for the maternal and fetal adrenal cortices. This effect could be mediated both directly, through placental secretion of ACTH1-39 and other peptides, and indirectly via placental CRH1-41 stimulation of pituitary ACTH1-39 secretion. Thus, the placenta is likely to influence the progressive changes that occur in the maternal HPA axis during pregnancy and to promote the developmental changes that occur in the fetal HPA axis. These effects are likely to be of particular importance near term, when the maternal and fetal HPA axes are maximally active and the fetus is dependent upon elevated glucocorticoid levels for maturation of organ systems. Finally, evidence from a variety of studies implicates placental CRH1-41 and ACTH1-39 in the cascade of events involving glucocorticoids and prostaglandins that culminates in parturition.
Maintenance of bioenergetic balance in sperm and prevention of lipid peroxidation: a review of the effect on design of storage preservation systems
Authors: Hammerstedt RH
Published: October 2005

Effective use of encapsulated sperm requires careful review of: (a) the conditions under which the procedure can be effectively used; (b) assessment of the effect of storage conditions on sperm survival; (c) description of the environment of the female tract before, during and after capsule deposition; and (d) economic evaluation of impact and costs of the putative technology. Sperm survival depends on successful sustenance over two periods of storage (at subambient temperatures after collection and extension, then at body temperature when placed in the female tract) and one period of action (after release and until fertilization). The bioenergetic requirements of cauda epididymal and ejaculated bull and ram sperm are reviewed in terms of absolute ATP needs and are discussed in terms of storage needs. In addition, sperm inactivation by lipid peroxidation is discussed and suggestions are provided to minimize the process. Two general types of containers are possible. An open porous form allows free passage of nutrients and metabolic products; the entrapped sperm are thus subjected to the changing environment in the female tract. The other form is a sealed capsule that opens to release sperm before ovulation; it provides a sperm storage environment independent of female tract chemistry but introduces problems of nutrient supply and metabolite release. Potential experimental approaches to evaluate each type of system are discussed.
Early sperm-egg interaction after sperm microinjection
Authors: Sathananthan AH , Ng SC , Liow SL , Ho J , Bongso A , Ratnam SS
Published: October 2005

The early events of sperm-egg interaction occurring 1-3 h after multiple sperm injection into the perivitelline space (PVS) and after direct injection into the ooplasm of human oocytes are reported. The sperm acrosome reaction occurred in the PVS but was not detected within the ooplasm. Sperm in the PVS were incorporated into the ooplasm in the usual manner described in vitro, after completion of the acrosome reaction, and a block to polyspermy was evident at the oolemma. However, sperm incorporation into the ooplasm was not clearly defined and requires further investigation. Sperm were also incorporated into oolemma-bound vacuoles within the ooplasm and breaches in the ooplasm were seen after intracytoplasmic injection. Both normal and abnormal sperm were found in the PVS and ooplasm, even though sperm from donors with normal semen parameters were used. The effect of freezing in liquid nitrogen on demembranation of sperm for microinjection is also reported.
Structure-function relationships and mechanism of action of pituitary and placental gonadotrophins
Authors: Apparailly F , Laurent-Cadoret V , Lecompte F , Chopineau M , Maurel MC , Guillou F , Combarnous Y
Published: October 2005

Data from the author's laboratory on relationships between structure and function of equine luteinizing hormone, follicle-stimulating hormone and choriogonadotrophin as well as their mechanisms of action are reviewed and compared with their human counterparts. Polymorphism of these hormones and problems associated with their purification are discussed as well as the association and dissociation of their alpha- and beta-subunits. The affinity of receptor binding, the superactivity of membrane transduction and homologous desensitization of target cells by non-stimulatory doses of the gonadotrophins are also reviewed.
Oxytocin stimulates uterine prostaglandin F2 alpha secretion in red deer Cervus elaphus
Authors: Flint AP , Jabbour HN , Loudon AS
Published: October 2005

The prostaglandin F2 alpha analogue cloprostenol stimulates ovarian secretion of oxytocin in red deer hinds and Pere David's deer hinds, as in cattle and sheep, but the response of the uterus to administered oxytocin has not been studied in deer. In the present experiment, oxytocin administered intravenously caused an increase in circulating concentrations of 13,14-dihydro-15-keto prostaglandin F2 alpha from 186 +/- 35 to 404 +/- 34 pmol L-1 within 5 min; concentrations in saline-treated hinds were unchanged (150 +/- 12 and 164 +/- 12 pmol L-1 before and after treatment respectively). This suggest that in red deer as in other ruminants, a positive feedback relationship between the corpus luteum and the uterus may operate to stimulate luteolytic episodes of prostaglandin F2 alpha.
Virus-vectored immunocontraception of feral mammals
Authors: Tyndale-Biscoe CH
Published: October 2005

The potential value of immunosterilization as a means to control species of wildlife that are widespread, numerous and undesirable is assessed. Key questions about the efficacy of fertility control and the means for delivering antigens expressed in recombinant viral vectors are discussed and the legal and social concerns that relate to its possible future use are raised.
The potential of murine cytomegalovirus as a viral vector for immunocontraception
Authors: Shellam GR
Published: October 2005

Wild populations of house mice (Mus domesticus) regularly undergo population eruptions in the cereal growing regions of S.E. Australia, causing significant damage to crops. Rodenticides are costly and are of limited usefulness, and the need for a biological control agent is widely recognized. The options for the use of an infectious agent to control mouse populations are considered. The three main types are: infectious agents which establish lethal infection; those which directly interfere with fertility; and recombinant virus vectors encoding fertility-associated proteins such as zona pellucida or sperm antigens in order to induce immunocontraceptive responses in infected mice. Ectromelia, a murine pox virus, has the potential for reducing mouse populations by lethal infection but it is not present in wild mice in Australia. The disadvantages of using ectromelia are that it would pose a significant threat to colonies of laboratory mice, there appears to be substantial innate resistance in Australian wild mice and it may not be entirely mouse-specific, thus placing native rodents at risk. A number of factors influencing the selection of a virus as a vector for immunocontraception are discussed. The mouse-specific murine cytomegalovirus (MCMV) fits most of these criteria. Infection with MCMV is already widespread in Australia with 80-90% of Mus domesticus tested being seropositive. It is a large DNA virus which establishes persistent, non-lethal infection, it is a suitable vector for the insertion of foreign genes and has a number of properties, including the capacity for superinfection, that should assist the recombinant virus to persist in wild mouse populations and induce an immunocontraceptive effect.
Interactions of sperm and the reproductive ducts of the male tammar wallaby, Macropus eugenii (Macropodidae: Marsupialia)
Authors: Jones RC , Clulow J
Published: October 2005

This review compares sperm production in the tammar wallaby and eutherian mammals, particularly the rat. The capacity of sperm to fertilize an ovum when they leave the testis and the changes they undergo in the epididymidis are considered. The structural differentiation and regulation of the extratesticular duct system is assessed and related to the reabsorption and secretion of water, inorganic ions and proteins, and the interaction of sperm and proteins synthesized and secreted by the epididymidis. Adaptations of the cauda epididymidis for storing spermatozoa are also considered. It is suggested that the tammar may be a good animal model to study the suppression of sperm motility and metabolism in the cauda epididymidis as it is possible to collect from them luminal samples of sperm which are initially immotile and then spontaneously activate during incubation in vitro.
Male-induced oestrus and ovulation in female brush-tailed bettongs (Bettongia penicillata) suckling a young in the pouch
Authors: Smith MJ
Published: October 2005

Female brush-tailed bettongs isolated from males usually do not come into oestrus or ovulate. Individuals isolated during pregnancy and at parturition do not ovulate post partum and are in the unusual condition for a macropodoid of suckling a pouch young but lacking a quiescent corpus luteum or a diapause embryo. Females in this condition were tested for their ability to come into oestrus and to ovulate after re-introduction to the male. When returned to the male on Day 1 of lactation, females generally mated before Day 2 and ovulated; at all later stages of lactation, six or seven days after being returned to the male > or = 50% of females came into oestrus, mated and ovulated. The vaginal smears of most females in isolation were typical of post oestrus on Day 2; after being returned to the male on Day 11, these females came into oestrus in seven days, mated and ovulated. The results show that suckling a young in the pouch does not suppress ovulation in this species provided that an adult male is present. Moreover, the results indicate that the mechanism of male-induced ovulation 24 h post partum differs from that of the remainder of the pouch suckling period.
HPRT activity in embryos of a South American opossum Monodelphis domestica
Authors: Johnston PG , Dean D , VandeBerg JL , Robinson ES
Published: October 2005

Marsupial females show preferential paternal X-inactivation. However, the time at which X-inactivation occurs in early development has not yet been determined. A double microassay which measures the activities of X-linked hypoxanthine phosphoribosyl transferase (HPRT) and the autosomally-coded adenine phosphoribosyl transferase (APRT) from the same sample was performed on a collection of embryos from a South American opossum Monodelphis domestica. The embryos ranged in age from the 2-cell stage to the bilaminar blastocyst stage. The results indicate that their embryonic HPRT and APRT are not expressed until just before the unilaminar blastocyst stage in M. domestica. This is at a later stage of development than that in the mouse where embryonic HPRT and APRT expression first occurs at the 4-8-cell stage. It is concluded that HPRT is an uniformative enzyme for assessing X chromosome activity in cleaving embryos of M. domestica. The widespread distribution of HPRT:APRT ratios after the unilaminar blastocyst stage also makes it difficult to draw conclusions about the state of X chromosome activity in early marsupial development.
Mouse testis Pdha-2 promoter upstream sequences confer tissue-and temporal-specific activity in transgenic mice
Authors: Iannello RC , Young JC , Sumarsono S , Tymms MJ , Kola I
Published: October 2005

Spermatogenesis is a complex process requiring the coordinate expression of a number of testis-specific genes. One of these, Pdha-2, codes for the murine testis-specific isoform of the E1 alpha subunit of the pyruvate dehydrogenase complex. To elucidate the mechanisms regulating its expression in vivo, we have begun to investigate the Pdha-2 promoter in transgenic mice. In this paper, a construct containing 3.0 kb of promoter and upstream sequences is reported to be sufficient for directing the testis-specific expression of a CAT reporter gene in mice harbouring the transgene. Similarly to the endogenous Pdha-2, the CAT gene is expressed in testis in a stage-specific manner. However, the 3.0-kb Pdha-2 promoter is not active in somatic tissue suggesting that repressor elements may be present within these sequences.
Progress and emerging problems in livestock transgenesis: a summary perspective
Authors: Seamark RF
Published: October 2005

The creation of transgenic livestock is a complex multistep procedure the successful execution of which demands a high level of skill and application. Useful animals have been generated by transfer of genes to zygotes by microinjection, but further extension to livestock breeding is severely limited by the present low efficiency and lack of precision in gene transfer procedures. There are major developments in alternative approaches to gene transfer and those based on embryonic stem (ES) cell lines show particular promise as a broadly adaptable means of allowing precise manipulation of specific genes within the animal genome. Rapid progress is being made in adapting ES cell technology to livestock species but as yet no one has demonstrated the totipotency of the putative cell lines so far generated. The demonstration of the feasibility of the chimaeric route for reinstating an ES cell genome into the germ line of the pig is a major advance. For other livestock breeds, particularly those with long generation times and bearing single young where the chimaeric route is much less useful, there are encouraging developments in nucleus transfer (cloning) technology which could provide practical solutions. Overall, there are now good reasons to be optimistic that transgenesis will eventually be available to all livestock breeders with the proviso that there are no further unanticipated phenomena such as the effect of tissue culture on imprinting, to be discovered to threaten the predictability of outcome of ES cell-derived pregnancies and further limit the potential usefulness of this futuristic technology to the livestock industry.
Temporal changes to uterine collagen types I, III and V in relation to early pregnancy in the rat
Authors: Hurst PR , Gibbs RD , Clark DE , Myers DB
Published: October 2005

Uterine tissues of pregnant rats were extracted to define any changes to the proportions of collagens types I, III and V. The total concentration of extracted collagen was determined in tissue samples from implant and adjacent non-implant (NI) sites. Extracts were also subjected to polyacrylamide gel electrophoresis (PAGE), immunoblotting and gel densitometry to define the collagen types and to determine their relative proportions. By relating the proportions to the collagen concentrations in the extracts, type I was found to be the predominant collagen in both tissue regions although the concentration in the implant sites was lower than that in the NI sites. The concentration of Type I collagen decreased significantly over the period of observation in both implant and NI sites. Although the concentrations of collagen type III and type V also decreased in the implant sites, they did not alter in the NI sites. The results demonstrate that shortly after the initiation of implantation the uterus responds to the presence of the implanting embryo by decreasing the concentration of all three types of collagen. This indicates that their metabolism may, in part, be regulated by similar mechanisms. Furthermore, it was evident that a decrease in the concentration of collagen type I was initiated in uterine areas that, at the time of sampling, were not directly involved with implantation. During the study, it was found that the alpha 1 chain of collagen type V separated into two distinct bands when run on gels containing 3.8 M urea.(ABSTRACT TRUNCATED AT 250 WORDS)
Stimulatory and inhibitory factors of Leydig cell steroidogenesis are secreted simultaneously by the rat seminiferous tubules and do not affect Leydig cell inhibin production in vitro
Authors: McFarlane JR , de Kretser DM , Risbridger GP
Published: October 2005

The effect of conditioned medium from rat seminiferous tubules (at Stages VII-VIII and Stages IX-VI) cultured with or without follicle-stimulating hormone (FSH) on the production of testosterone and immunoactive inhibin by Leydig cells was examined. Low doses of conditioned medium from unstimulated tubules at Stages VII-VIII significantly (P < 0.05) increased the mean testosterone production to greater than 31 +/- 11% over that achieved with luteinizing hormone (LH) alone. At the highest dose, the conditioned medium significantly inhibited (P < 0.05) LH-stimulated testosterone production by 13 +/- 7%. Low doses of conditioned medium from unstimulated tubules at Stages IX-VI increased the mean testosterone production to 22 +/- 10%, whereas at higher doses, a significant reversal in the stimulation occurred although not to the same extent as that found with medium from tubules at Stages VII-VIII. Conditioned medium from FSH-stimulated tubules at Stages VII-VIII and Stages IX-VI, significantly increased testosterone production to 39 +/- 7% and 31 +/- 13% respectively. Immunoactive inhibin production by the Leydig cells remained unaffected by exposure to conditioned medium from FSH stimulated and unstimulated tubules at Stages VII-VIII and Stages IX-VI. The data demonstrate that tubule culture medium contains FSH-modulated activities which can specifically stimulate and inhibit testosterone synthesis by adult rat Leydig cells in vitro and therefore explains the contradictory reports in the literature.
Low MHC class II variability in a marsupial
Authors: McKenzie LM , Cooper DW
Published: October 2005

The major histocompatibility complex (MHC) loci have been shown to be highly polymorphic in most eutherian ('placental') species studied. Several hypotheses have been advanced for the maintenance of this exceptional level of genetic variation, one of which suggests that it is necessary for successful eutherian reproduction. Marsupials (metatherians) and eutherians are the only two groups of viviparous mammals, but their modes of reproduction are quite distinct. Although marsupials have placentae, they are generally shorter lived and less invasive than in eutherians. Other investigations have shown that genetic variation at marsupial MHC class I loci is probably high. Weak or non-existent mixed lymphocyte culture responses previously reported in several marsupial species have suggested a lack of class II variation. Data have therefore been collected on the level of restriction fragment length polymorphism at MHC class II beta-chain encoding loci of a marsupial, Macropus eugenii (the tammar wallaby). This level is shown to be low, between the level of MHC variation found in cheetahs and a population of lions with a restricted genetic base. Attention is drawn to the need to collect more data on the level of class II variability in both eutherians and marsupials, and to the potential of marsupials for understanding the relation, if any, between mode of reproduction and MHC variability.
Intracytoplasmic sperm injection (ICSI) versus high insemination concentration (HIC) for human conception in vitro
Authors: Fishel S , Lisi F , Rinaldi L , Lisi R , Timson J , Green S , Hall J , Fleming S , Hunter A , Dowell K , et al
Published: October 2005

The use of high insemination concentration (HIC) for in vitro fertilization (IVF) was compared with intracytoplasmic sperm injection (ICSI) in cases of male factor infertility. Sibling oocytes (n = 252) from 24 patients were used, 123 for HIC and 129 for ICSI. Although the incidence of fertilization was decreased with HIC (48% v. 61%), this treatment was nevertheless a viable option for many patients, especially when ICSI was not available. However, there was a higher incidence of cytoplasmic fragmentation of embryos after HIC compared with ICSI (36% v. 10%, P = 0.003) and the outcome was significantly affected by the severity of teratozoospermia. Using a cut-off of 5% normal forms, the incidence of fertilization with HIC for the group with < 5% normal forms was 37% compared with 72% for the group with > 5% normal forms; there was also a significant decrease in cleavage rate (P = 0.05) and the number of regular embryos (P = 0.005), and an increase in cytoplasmic fragmentation (P = 0.006) in patients with < 5% normal forms. No distinction was made between cases of teratozoospermia when ICSI was used. The present study confirms the value of HIC as a first line treatment for male infertility, as long as ICSI remains significantly more expensive and concerns on safety are mooted. However, the use of sibling oocytes for ICSI is recommended, especially in cases with < 5% normal sperm morphology.
Development and implementation of intracytoplasmic sperm injection (ICSI)
Authors: Palermo GD , Cohen J , Alikani M , Adler A , Rosenwaks Z
Published: October 2005

The purpose of this paper is to elucidate the experimental steps that led to the development of intracytoplasmic sperm injection (ICSI) and its application in the human. ICSI has become the most successful micromanipulation procedure for treating male infertility. A total of 355 in vitro fertilization (IVF) cycles utilizing ICSI are described; 180 couples were previously treated in 509 IVF cycles but achieved no fertilization and 175 couples could not be treated by IVF because of extremely poor semen parameters. Of the 3063 metaphase II (M II) oocytes retrieved, 2970 were injected with a survival rate of 93.6%, yielding 1917 bipronuclear zygotes (64.5%). In 148 patients, a foetal heart was evidenced by ultrasound; 11 of these patients miscarried between 7 and 13 weeks of gestation. The ongoing pregnancy rate was 38.6% (137/355) per retrieval and 40.5% (137/338) per embryo replacement. At the time of writing, there were 22 deliveries and one therapeutic abortion for a trisomy 21 chromosomal abnormality. In addition, 66 singleton, 37 twin, 10 triplet and 1 quadruplet pregnancies were ongoing. The concentration of motile spermatozoa in the ejaculate only slightly influenced the fertilization rate (P < 0.001) and the pregnancy outcome (P < 0.01). A preliminary injection procedure utilizing intracytoplasmic injection of isolated sperm heads was performed in 35 M II human oocytes with resultant fertilization and cleavage rates of 74% and 73% respectively. Skills in ICSI were acquired by injecting hamster and unfertilized human oocytes with human sperm. ICSI can be used to successfully treat couples who have failed IVF or who have too few spermatozoa for conventional in vitro insemination.(ABSTRACT TRUNCATED AT 250 WORDS)
Placental and fetal hepatic growth are selectively inhibited by prolonged reductions of uterine blood flow in pregnant sheep
Authors: McLellan KC , Bocking AD , White SE , Han VK
Published: October 2005

Experiments were conducted in eight pregnant sheep to determine the effect on fetal growth of mechanical restriction of uterine blood flow (RUBF) between 120 days and 134 days gestation. Uterine blood flow measured in the middle uterine arteries was 40% less in RUBF animals compared with control animals at the end of the experimental period. There was no change in fetal blood gases, bodyweights, or organ weights between the two groups of animals. The rate of DNA synthesis in the right lobe of the liver was significantly less in RUBF animals (581 +/- 34 dpm micrograms-1 DNA) compared with control animals (845 +/- 44 dpm microgram-1 DNA). There was no difference in the rate of DNA synthesis in the left lobe of the liver or in any of the other organs examined. Autoradiographic examination of the placental cotyledons demonstrated that most DNA synthesis in the placenta was occurring in fetal trophoblastic cells and there was a 40% reduction in the nuclear-labelling index of placental trophoblast cells. These studies show that mild mechanical reductions in uterine blood flow in pregnant sheep results in the selective inhibition of growth in the right lobe of the fetal liver and the placental trophoblastic cells. The mechanism underlying this close association remains to be determined.
Thyrotrophin-releasing hormone (TRH) and lung maturation
Authors: Liggins GC
Published: October 2005

Clinical trials of thyrotrophin-releasing hormone (TRH) in conjunction with antepartum glucocorticoid treatment in the prevention of respiratory distress syndrome is based on experimental evidence that fetal lung maturation is accelerated by exposure to raised concentrations of triiodothyronine (T3) in fetal plasma. Studies of fetal rat and rabbit lung in vitro show an inconsistent increase in surfactant synthesis in response to T3 and potentiation of the response to corticosteroid. Experiments with fetal rodents in vivo are difficult to interpret because of confounding effects of the procedures and the responses to T3 are variable. In fetal sheep, very high concentrations of T3 are without effect on lung maturation. These observations suggest that the action of TRH on the lung may be mediated at least in part by one of the numerous, non-hormonal pathways known to be stimulated by TRH, particularly the autonomic nervous system. Experiments in rats and sheep lend support to this possibility. It is concluded that available evidence is inadequate to determine the mechanism of action of TRH.
Blood pressure and cardiovascular reflex development in fetal sheep. Relation to hypoxaemia, weight, and blood glucose
Authors: Crowe C , Bennet L , Hanson MA
Published: October 2005

We measured mean arterial blood pressure (MAP), fetal heart rate (FHR), the baroreflex, weight, blood gases, blood glucose and lactate in chronically instrumented fetal sheep for 14 days from Day 105 to Day 109 gestation, with or without daily administration of 1 h of acute isocapnic hypoxaemia (arterial O2 partial pressure, PaO2, 11-13 mm Hg; 1 mm Hg = 133 Pa). Fetuses subjected to hypoxia showed no significant differences in MAP or FHR v. control fetuses. However, examination of all fetuses together revealed that there were two distinct groups: those showing a rise in MAP over the 14 days ('pressure up' group, PU), and those in which blood pressure did not increase or showed only a slight decrease ('pressure down' group, PD). PU fetuses were proportionately larger than PD fetuses. In contrast to PU fetuses, PD fetuses had lower blood glucose concentration, arterial O2 saturation (SaO2), PaO2, total haemoglobin, haematocrit and oxygen content, and higher lactate concentration, pH and PaCO2. PU fetuses showed a shift of the baroreflex MAP/R-R interval curve to the right, however, the PD group showed a shift upwards from Day 1 to Day 14. The PD group responded to hypoxia with a greater increase in MAP than the PU group. Thus, repeated acute moderate isocapnic hypoxia does not affect development of MAP or FHR in late gestation fetal sheep. However, MAP follows different trajectories in individual fetuses, related to fetal size and the availability of oxygen and/or glucose. Cardiovascular chemoreflexes and baroreflexes are also different, depending on the MAP trajectory. These data indicate an important association between growth and blood pressure development, and also show that differences in growth are associated with changes in cardiovascular control.
Neuronal damage in the developing brain following intrauterine asphyxia
Authors: Mallard EC , Williams CE , Johnston BM , Gluckman PD
Published: October 2005

Perinatal asphyxia is thought to be a significant cause of still birth and neurological sequelae. Although several different patterns of neuronal injury are seen in the newborn, previously little was known about the precise cause and effect relationships. This brief review summarizes recent research which has identified how prenatal factors such as recurrent episodes of asphyxia, gestational age, growth retardation and cerebral temperature may influence the severity and regional distribution of neuronal loss.
The molecular biology of SRY and its role in sex determination in mammals
Authors: Koopman P
Published: October 2005

SRY is the gene that initiates the genetic cascade leading to testis development in mammals. Since its discovery in 1990 and the direct demonstration of its male-determining role in transgenic mice, attention has turned to understanding the biochemical mode of action of the SRY gene product, and to the identification of other genes in the sex-determining pathway. Recent progress in these efforts is summarized in this review.
Three-probe fluorescence in situ hybridization to assess chromosome X, Y, and 8 aneuploidy in sperm of 14 men from two healthy groups: evidence for a paternal age effect on sperm aneuploidy
Authors: Robbins WA , Baulch JE , Moore D , Weier HU , Blakey D , Wyrobek AJ
Published: October 2005

The method of simultaneous three-chromosome fluorescence in situ hybridization (FISH) was developed using repetitive DNA sequence probes for chromosomes 8, X and Y and applied to semen of 14 men from two healthy groups who differed in their average ages (46.8 +/- 3.1 years, n = 4 v. 28.9 +/- 5.0 years, n = 10). The frequencies of disomic sperm determined by FISH compared well with frequencies obtained using the hamster-egg technique for human-sperm cytogenetics and with the frequencies of disomic and diploid sperm reported in previous FISH studies in this laboratory. The two groups of men did not differ in their baseline frequencies of sperm disomic for chromosome 8 (approximately 6.5 per 10(4) sperm), sperm with XY8 aneuploidy (approximately 9.5 per 10(4) sperm), or sperm with autodiploidy XX88 or YY88 (approximately 2 per 10(4) sperm). However, the older group had statistically higher frequencies of sperm carrying sex chromosomal disomy than the younger group (5.1 v. 2.2 per 10(4) sperm for XX8; 5.9 v. 2.0 per 10(4) sperm for YY8; P < 0.005). A recent report from this laboratory of sex-chromosomal aneuploidy in sperm of aged mice provides inter-species corroborating evidence for this preliminary finding of a paternal age effect on sperm aneuploidy in human males.
Sex preselection by flow cytometric separation of X and Y chromosome-bearing sperm based on DNA difference: a review
Authors: Johnson LA
Published: October 2005

Recent research on the flow cytometry of sperm for the purpose of predetermining gender of offspring has led to a validated method to separate X from Y chromosome-bearing sperm for use with in vitro fertilization and embryo transfer, intratubal insemination or intracytoplasmic sperm injection. The basis for the method is the sex chromosome-specific marker, DNA, which is present in greater amounts in X-bearing sperm than in Y-bearing sperm of mammals. Sperm are exposed to the vital dye Hoechst 33342 which binds to the minor groove of the DNA helix. Flow cytometric sorting of the sperm using a laser as the excitation source results in populations of Y- or X-bearing sperm that are 85-90% pure. Several hundred offspring have been produced from swine, rabbits, sheep and cattle that confirm the predicted sex. The method is currently being applied to the commercial embryo market. The method is not likely to be used in conjunction with standard cattle or swine artificial insemination practice in its current form since only about 4 x 10(5) sorted sperm can be produced per hour of sorting. The technology has also been applied to human sperm for use by couples that are at risk to sex-linked disease expression in their offspring. Populations of human sperm have been sorted with X and Y purities of about 80% as confirmed by DNA probe technology and fluorescence in situ hybridization.
Influence of fetal death and fetectomy on gestation and the initiation of parturition in the ewe
Authors: Rueda BR , Dunn TG , Anthony RV , Moss GE
Published: October 2005

Depressed function of the fetal hypothalamic-pituitary-adrenal axis results in prolonged gestation, and fetal death causes premature parturition. The objective of this experiment was to determine effects of death in utero of a sibling, or its removal, on the duration of gestation and concomitant changes in maternal serum concentrations of oestradiol (E) and progesterone (P). Ovine placental lactogen (oPL) was also determined as an index of placental viability. Blood samples were collected in the morning, beginning 3 days prior to surgery on Day 115 +/- 3 of gestation and continuing daily until 3 days post partum. Surgeries were performed via mid-ventral laparotomy to induce fetal death or to remove the fetus. Fetal death was induced by ligating the umbilicus. Duration of gestation was similar (P > 0.05) in control (C, n = 6) and sham-operated (S, n = 3) ewes (148 +/- 1.0 and 148.6 +/- 0.7 days, respectively). On the day of parturition, concentrations of P, E and oPL were 5.2 +/- 1.9 ng mL-1, 135 +/- 22 pg mL-1 and 153 +/- 54 ng mL-1, respectively, in ewes from combined C and S groups. Total fetectomy (n = 3) resulted in a rapid decrease (P < 0.05) in maternal serum concentrations of P, E, and oPL. Ligation of the umbilicus of both fetus(es) in utero (n = 4) induced fetal death, decreased (P < 0.05) length of gestation to 118.8 +/- 1.8 days and decreased (P < 0.05) serum concentrations of P and oPL prior to parturition and oPL on the day of parturition. In addition, maternal serum concentrations of E failed (P > 0.05) to increase at parturition. Length of gestation and concentrations of P, E and oPL at parturition were not affected (P > 0.05) by removal of one fetus when its sibling was undisturbed (n = 4) compared to control ewes. In contrast, death of one fetus with its sibling undisturbed (n = 5) decreased (P < 0.01) length of gestation (139.2 +/- 2.8 days), but did not affect P, E and oPL (P > 0.05) on all days tested. In conclusion, death of one fetus reduced the duration of gestation, but changes prepartum in maternal serum concentrations of P and oPL were similar to ewes delivering only live fetuses. The increase in maternal concentrations of E that normally occur at parturition was absent in ewes giving birth to only dead fetuses and, therefore, was not a prerequisite to parturition.
Stimulation of gastric proteases in the neonatal pig by a rise in adrenocortical secretion at parturition
Authors: Sangild PT
Published: October 2005

In many species adrenocortical activity and glucocorticoid secretion increase in late gestation and reach a peak at birth. In this study, we investigated the hypothesis that glucocorticoids stimulate the synthesis of gastric protease zymogens in the perinatal period of pigs. Pigs were delivered by Caesarean section 3-4 days prior to term (to circumvent the natural cortisol surge) and treated daily with either saline (n = 11), metyrapone (an inhibitor of cortisol synthesis, n = 12), adrenocorticotropic hormone (ACTH, n = 14) or cortisol-acetate (n = 6). The pigs were killed at 3 or 6-7 days of age and concentrations of protease zymogens in gastric mucosal extracts determined by electroimmunoassay. Zymogen contents were also determined in control (untreated) pigs from one week before birth to four weeks after birth. In control pigs, concentration of prochymosin increased rapidly before term, peaked at birth, and decreased in the postnatal period; concentrations of pepsinogen A, pepsinogen B and progastricsin were low in newborn pigs and increased in the weeks after birth. Caesarean-delivered pigs injected with saline had lower concentrations of prochymosin and pepsinogen A at 6-7 days than vaginally delivered pigs of the same postnatal age. The concentrations of these zymogens were further reduced after metyrapone treatment (depressed cortisol secretion) but were increased after treatment with ACTH (stimulated cortisol secretion) or cortisol-acetate (exogenous glucocorticoid). No consistent effects were observed for the two minor gastric protease zymogens in the pig, pepsinogen B and progastricsin. The results suggest that the normal pre-partum surge in circulating cortisol stimulates the development of the major gastric protease zymogens in the pig, prochymosin and pepsinogen A.
Liquid movements in ventilated and perfused isolated lungs of fetal sheep at 0.87, 0.90, and 0.95 of term
Authors: Schmolling J , Seeger W , Jensen A
Published: October 2005

To study lung liquid movements, an isolated lung model, adapted from adult physiology, was developed to measure pulmonary weight changes after the onset of artificial ventilation of lungs from 16 fetal sheep at 0.87 (n = 5), 0.90 (n = 6), and 0.95 (n = 5) of gestation. The fetuses were delivered by Caesarean section. After tracheotomy and thoracotomy under general anaesthesia, a blocked air-free tracheal cannula and a pulmonary arterial catheter were inserted and secured to ensure in situ perfusion of the pulmonary circulation (Krebs-Henseleit buffer) without ventilation before the lungs were removed from the chest and mounted in a specially designed apparatus. Lung weight and pulmonary perfusion pressure were recorded continuously before, during and after the onset of ventilation. After 50 min of ventilation the perfusate was allowed to recirculate and samples were taken at 10-min intervals to determine the concentrations of sodium and the activity of lactate dehydrogenase (LDH) as a marker for cell destruction. In all lungs studied there was a significant removal of lung liquid after the onset of ventilation as assessed by lung weight loss. However, there was a positive correlation between lung weight loss and gestational age of the donor fetuses. These changes were accompanied by a rise in sodium concentrations in the perfusate, possibly suggesting that active sodium transport across the pulmonary epithelium facilitates alveolar liquid removal. As the experiments progressed the lungs regained weight while LDH concentrations increased, indicating that lung cell destruction causing pulmonary oedema may be involved. This pulmonary weight gain was inversely related to gestational age. It is concluded that in isolated ventilated and perfused lungs from fetal sheep, lung liquid removal is an age-related phenomenon that might involve an active sodium transport mechanism. It is further concluded that the development of pulmonary oedema during ventilation is also age related.
Cellular localization of glucose transporter messenger RNA in human placenta
Authors: Jansson T , Cowley EA , Illsley NP
Published: October 2005

High levels of expression of the glucose transporter (GLUT) isoforms 1 and 3 have been demonstrated in the human placenta by Northern blotting. However, the cellular localization of placental GLUT mRNA has not been described. Furthermore, recent preliminary kinetic data indicate that GLUT 2 might be present in syncytiotrophoblast. Human placental tissue from preterm (16-22 weeks) and term pregnancies was collected for identification and localization of glucose transporter mRNA. Following paraffin embedding, sections were cut and in situ hybridization was performed with fluorescein-labelled cRNA. In addition, immunoblotting and immunocytochemistry were carried out using an anti-GLUT 2 antibody. GLUT 1 mRNA was highly expressed in syncytiotrophoblast cells at term. GLUT 1 expression was much less abundant in non-syncytial cells. In contrast, GLUT 3 mRNA was present in lower amounts and more evenly distributed between syncytial and other placental cells. GLUT 1 mRNA was also highly abundant in preterm syncytiotrophoblast. The cellular distributions of GLUT 1 and GLUT 3 mRNA in the preterm placentas were similar to those in term tissue. With regard to GLUT 1, these findings correlate well with cellular localization and gestational development of GLUT 1 protein. No GLUT 2 protein was detected. It is concluded that GLUT 1 is the main isoform involved in transplacental glucose transport in the human.
Influence of organic cations on basic amino-acid uptake by human placental villi
Authors: Krishna RB , Dancis J , Levitz M
Published: October 2005

Human placental chorionic villi were incubated for 30 min with [3H]lysine or [3H]arginine and the distribution ratios (intracellular:extracellular concentrations) were determined. The ratios remained unchanged when Na+ in Earle's buffered salt solution was replaced with Li+. When Na+ was replaced with choline there was a significant increase is distribution ratios (lysine 1.34 +/- 0.33 v. 3.99 +/- 0.15, arginine 1.95 +/- 0.37 v. 5.05 +/- 1.16). Leucine, a neutral amino acid with a Na(+)-independent transport system, was unaffected by choline substitution. The distribution ratio for alanine, which is Na(+)-dependent, was reduced (2.50 +/- 0.41 v. 1.45 +/- 0.20). Two other quarternary amines, acetyl-beta-methylcholine and tetraethylammonium chloride (TEA) caused similar increases in the distribution ratios of the basic amino acids. Hordenine, a tertiary amine, was less effective and there was little or no effect with ephedrine, a secondary amine. The choline effect was first observable at concentrations of 105 mM. With TEA, there was a progressive increase in distribution ratios beginning at 29 mM. Lysine efflux was measured after incubation of villi with lysine in Earle's buffer or choline buffer. Lysine was rapidly released to the fresh medium with 25% more retained in choline-exposed villi. The amines may cause alterations in the kinetics of basic amino-acid transporters or may modify other aspects of placental physiology permitting an increase retention of the basic amino acids.
Lack of effect of cocaine on lysine and alanine uptake in human placental villi or transfer in perfused human placenta
Authors: Krishna RB , Levitz M , Dancis J
Published: October 2005

The effect of cocaine on lysine and alanine uptake in human placental villi and transfer across the dually perfused placenta was studied. Uptake (in terms of the intracellular to extracellular distribution ratio) of alanine and lysine was 2.81 +/- 0.30 (n = 5) and 1.45 +/- 0.24 (n = 5) respectively and was unaffected by cocaine (50-500 ng mL(-1) in the incubation medium. In the dually perfused placenta, the clearance index (ratio of amino acid to antipyrine clearance) was 0.35 +/- 0.03 and 0.30 +/- 0.05 and the transfer index (ratio of amino acid to L-glucose clearance) was 2.20 +/- 0.07 and 1.89 +/- 0.29 for lysine and alanine respectively. Cocaine at concentrations of 100 ng mL(-1) or 250 ng mL(-1) had no effect on the clearance of either amino acid. The results of this study indicate that concentrations of cocaine likely to be encountered in vivo do not affect uptake of lysine or alanine by placental villi or transfer across the perfused placental lobule, in contrast with the report that cocaine reduces uptake of alanine by placental vesicles. Experimental models must be critically evaluated before accepting the results as pertinent to a clinical situation.