John Falconer

Intrauterine Growth Retardation: Clinical and Experimental

ABSTRACT. Intrauterine growth retardation is a common and potentially hazardous problem for the fetus. Despite this, the obstetric factors associated with growth retardation have changed little in the last twenty years. Some of the other factors, the so‐called behavioural factors should be amenable to correction through education or changing social circumstances. Experimental studies presented here support the clinical observations that the growth retarded fetus is often malnourished and/or hypoxaemic. Restriction of placental growth results in fetal growth failure and these fetuses are chronically hypoxaemic and hypoglycaemic. Furthermore the apparent margin of safety between the delivery to and consumption by the fetus is less for the small fetuses. We suggest that this reduction in supply results in the endocrine changes and that these in turn, modulate the pattern of fetal growth.

Oral Epidermal Growth Factor Is Trophic for the Stomach in the Neonatal Rat

The stomach of the naturally suckled rat pup was shown to grow rapidly during the first 24 h following delivery. Both absolute weight (p less than 0.001) and weight in proportion to body weight (p less than 0.001) increased. The stomachs of pups fed formula containing epidermal growth factor (EGF) were larger than those of their control littermates (p less than 0.05). These data support a role for milk EGF in the regulation of neonatal gut growth.

Differential processing of corticotrophin-releasing hormone by the human placenta and hypothalamus.

The molecular forms of corticotrophin-releasing hormone (CRH) in human placentae and hypothalami were investigated by gel permeation chromatography of water extracts. Hypothalamic extracts produced one peak of immunoreactivity which coeluted with human CRH at Kd = 0.53. Placental extracts, however, had in addition to that peak, two other peaks eluting earlier at the void and at Kd = 0.35-0.38. Tryptic digestion of the middle peak produced immunoreactivity which coeluted with the standard. Larger forms were also found in plasma of women in the third trimester of pregnancy and during labour but not in eluates from superfused placental fragments which had only CRH41-sized material. These data indicate that tissue-specific post-translational processing occurs for CRH, and suggests that the link between synthesis and secretion is more immediate in the placenta than hypothalamus.

Secretion of corticotropin-releasing hormone by superfused human placental fragments

Corticotropin-releasing hormone (CRH) immunoreactivity (IR) is present in the blood of women in the 3rd trimester of pregnancy and in placental extracts. We have used a placental fragment superfusion system to investigate the release of CRH from fresh placental tissue. Fragments of normal term placenta were mixed with Biogel P2, packed into minicolumns and superfused with carbogen-gassed Earles buffer at 37 degrees C. The rheology of the superfusion system was determined and the oxygen consumption of the superfused placental fragments indicated viability of the tissue preparation over a 5-hour time span. CRH IR in the eluate was measured by radioimmunoassay (RIA) using the 41 residue synthetic peptide human, rat CRH-41 (h, r CRH-41) as the standard, 125I labelled Tyr- h, r CRH as the tracer and rabbit anti-ovine CRH as the antibody. The sensitivity of the assay is 2 pM. Size exclusion chromatography on Sephadex G-50 of the placental column eluate displayed one major peak of CRH IR which co-eluted with that of h, r CRH. Placental fragment superfusate displayed potent CRH bioactivity as assessed by beta-endorphin secretion from ovine pituitary cells. Replacing the superfusing medium of the placental fragments with 45 mM KCl resulted in a prompt increase in the release of CRH IR. These results indicate that placental cells in vitro secrete a molecule of similar molecular weight, immunoreactivity and bioactivity to h, r CRH and that the rate of secretion may be regulated.

Desensitization of Superfused Isolated Ovine Anterior Pituitary Cells to Human Corticotropin‐Releasing Factor

We have employed an in vitro system to study the time‐course of β‐endorphin (β‐EP) immunoreactivity release from anterior pituitary cells stimulated with corticotropin‐releasing factor (CRF) and whether exposure to CRF desensitizes the cells to subsequent stimulation. Ovine anterior pituitaries were enzymatically disrupted into single cells, mixed with Siegel P2 and superfused in mini‐columns with carbogen‐gassed medium at 37 °C. Superfusate fractions were collected at 5‐min intervals and β‐EP immunoreactivity in the eluate was measured by radioimmunoassay. Peaks of β‐EP release that rose significantly above baseline noise were detected using the PULSAR algorithm.

Recurrent pregnancy losses and the role of immunotherapy

Abstract Post implantation pregnancy losses are psychologically and economically stressful to the childbearing population. The etiology in the vast majority of cases is unknown but is partly thought to result from a breakdown of the maternal tolerance to the fetoplacental unit. Immunologically based therapy remains controversial but no alternative therapy is available at the moment. This article reviews the conceived immunological basis of recurrent pregnancy losses, discussing the controversies arising, and recommending the use of intravenous immunoglobulin, IVIg, in well controlled experiments for further clinical trials.

Plasma F2α-isoprostane levels are lowered in pigs fed an (n-3) polyunsaturated fatty acid supplemented diet following occlusion of the left anterior descending coronary artery

Abstract F 2α -isoprostanes, produced non-enzymatically from arachidonic acid are potent vasoconstrictors. Dietary supplementation with (n-3) polyunsaturated fatty acids has been shown to reduce arachidonic acid levels in the body. In the present study, alterations in plasma levels of the F 2α -isoprostane, 8-iso-prostaglandin F 2α , were assessed by enzyme immunoassay in pigs following (n-3) polyunsaturated fatty acid supplementation and during occlusion of the left anterior descending coronary artery. Pigs were fed diets supplemented with either fish oil (rich in n-3 polyunsaturated fatty acids) or beef tallow (high content of saturated fatty acids) for a 6 week period. The animals were then anesthetised and plasma samples were collected. The coronary artery was occluded and the blood samples were collected during the following 10 minutes. While plasma 8-iso-prostaglandin F 2α levels were generally lower in pigs fed the (n-3) fatty acid supplemented diet as compared with those fed the diet high in saturated fats, this response only reached statistical significance (P 2α remained unchanged in both dietary groups once occlusion was initiated. Significant differences (P 2α levels in the porcine circulation in comparison with animals fed beef tallow, particularly after coronary occlusion. This effect compliments the well established action of (n-3) fatty acids in reducing the production of vasoconstrictive eicosanoids.

Elution and partial characterization of immunoglobulins bound to ovine placenta

Immunoglobulins were eluted from ovine placentae and characterized by immunoprecipitation, electrophoresis, western blotting and ELISA. IgG was shown to comprise the bulk of placental‐bound immunoglobulins while smaller amounts of IgM and only trace amounts of IgA were demonstrated. Results suggest that ovine placental IgG eluted by surgical cannulation of the uterine blood vessels in situ is similar to that eluted from postpartum placentae in vitro, implying that there may be some transfer of antibodies across the maternal side of the placental barrier to the trophoblast. These antibodies are rich in IgG, and IgG2, have a relative molecular weight of 158 kDa, and bind to an 80 kDa peptide prepared from pre‐acidified ovine placental cotyledons.

Reverse haemolytic plaque assay study of corticotropin-releasing hormone and arginine vasopressin interaction in ovine corticotropes.

Corticotropin‐releasing hormone and arginine vasopressin are known to interact in stimulating secretion of adrenocorticotropin‐related peptides from corticotropes. However, the mechanism mediating this interaction is uncertain. Recently, evidence has been provided using a reverse haemolytic plaque assay that in rat pituitary cells, arginine vasopressin potentiates the effects of corticotropin‐releasing hormone by increasing the percentage of target cells that secrete adrenocorticotropin. To determine whether a similar mechanism also operates in the sheep corticotrope, which is reportedly more sensitive to arginine vasopressin than that of the rat, a reverse haemolytic plaque assay for β‐endorphin secretion was used to study the response of ovine corticotropes to stimulation by increasing doses of corticotropin‐releasing hormone or arginine vasopressin (0.1 nM to 10.0 nM) alone or in combination.

Intracellular mechanisms governing the acute phase of β-endorphin secretion from the corticotrope in vitro

It is not certain which protein kinase (A, C or both) is involved in the acute phase of beta-endorphin (beta-EP) release stimulated in the corticotrope by vasopressin (VP) and corticotropin-releasing factor (CRF). We have employed an isolated ovine anterior pituitary cell superfusion system to determine the dynamic effects of forskolin, a protein kinase A (PKA) stimulator, and phorbol 12-myristate 13-acetate (PMA), a protein kinase C (PKC) activator. Both secretagogues stimulated beta-EP release within 5 min and therefore both PKA and PKC are potential mediators of the acute phase of hormonal stimulation of the corticotrope. Pretreatment with PMA specifically desensitized the pituitary cell columns to subsequent PMA exposure while not significantly altering sensitivity to forskolin or 50 mM KCl.