No abstract

Bovine preimplantation embryos develop more successfully when cultured in groups, proibably because of the increased production of, and exposure to, embryotrophic autocrine and paracrine factors. Using a novel embryo culture technique, this study had two aims: 1. to determine the distance over which potential paracrine interactions affect bovine embryo development in terms of blastocyst and hatching rates, cell counts and carbohydrate metabolism; 2. to investigate the effect of platelet-activating factor (PAF) supplementation on bovine embryo development and metabolism. Groups of 16 presumptive zygotes were attached to the bottom of a culture dish by the cell adhesive Cell-Tak in a 4 3 4 equidistant array. The distance between individual embryos in each group was 0-689 mm. Optimal blastocyst formation rate occurred when embryos were cultured 165 mm apart compared with control non-attached zygotes (Kruskal-Wallis followed by Mann-Whitney U test post-hoc; P < 0.05). Increasing the distance between embryos resulted in a further decline in blastocyst rate, which reached zero at 540 mm apart. Blastocyst cell number, pyruvate/glucose uptake and lactate production decreased as the interembryo distance increased from 240 to 465 mm (P < 0.05). Supplementation with PAF during conventional group culture enhanced blastocyst cell number, hatching rates and the oxidative metabolism of pyruvate and glucose. The data indicate that the distance between individual bovine embryos in culture influences preimplantation development, in particular blastocyst formation, cell number and metabolism. It is suggested that diffusible paracrine/autocrine factors, such as PAF, are in part responsible for the regulation of early embryo development.

The objective of this article is to review the role of matrix metalloproteinases (MMPs) in fetomaternal/neonatal complications of preterm birth. The function of MMPs as proteolytic enzymes involved in tissue remodeling/destruction is reviewed in preterm labor, preeclampsia, premature rupture of membranes, intrauterine growth restriction, chronic lung disease, necrotizing enterocolitis, intraventricular hemorrhage, cystic periventricular leukomalacia, and retinopathy of prematurity. Cytokines, steroid hormones, and reactive oxygen species all regulate MMP labor and expression/activity. In labor, activation follows an inflammatory response, which results in fetal membrane rupture and cervical dilation/ripening, particularly when premature. Expression/activation is elevated during parturition, particularly when premature. While fetal membrane rupture is preceded by increases in tissue-specific MMPs, neonatal complications also ensue from an imbalance between MMPs and their tissue inhibitors. These e fects implicate environmental triggers and a genetic predisposition. MMPs are involved in the perinatal complications of prematurity and are potential targets for therapeutic intervention. Functional MMP genetic polymorphisms may assist in identifying patients at risk of complications.

Bovine oocyte maturation in vitro frequently results in abnormal cytoplasmic maturation and failure to acquire developmental competence. This is, in part, likely to be due to the non-physiological nutritional milieu to which oocytes are exposed. Improvements in oocyte developmental potential may be achieved by modelling nutrient profiles on those of preovulatory follicular fluid (FF). However, little is known about fluctuations in FF nutrient levels according to follicle dominance and oestrous cyclicity. This study therefore characterised the carbohydrate and amino acid profile of FF according to these parameters, and compared preovulatory FF composition with that of maturation medium. Carbohydrate concentrations (n 5 121) were determined enzymatically whilst amino acid profiles (n 5 40) were determined by reverse-phase HPLC. Pyruvate and glucose concentrations were unaffected by follicle dominance, whereas Stage III -IV lactate profiles were higher in non-dominant FF (P < 0.01). While most dominant FF amino acid concentrations were affected by oestrous stage, only glutamate, alanine, leucine and lysine levels fluctuated in non-dominant FF. Glucose and lactate concentrations were significantly negatively correlated, whereas most amino acids were significantly positively correlated with each other. Maturation medium had higher pyruvate and lower lactate concentrations than preovulatory FF (P < 0.001), whereas glucose level was similar. All amino acid levels (except histidine, taurine, alanine and tryptophan) differed significantly between maturation medium and preovulatory FF. These data indicated that FF composition varies throughout the oestrous cycle. Preovulatory FF nutrient profile differed from that of maturation medium, perhaps accounting for the poor developmental competence of in vitro matured oocytes. These data may contribute to the formulation of a nutritionally more physiological maturation medium.

Seminal fluid is known to be responsible for orchestrating mating-induced immunomodulation. Central to this process are numerous cytokines that modulate uterine leukocyte recruitment and trafficking.