Sodium iodide symporter (NIS) gene expression in human placenta

The placenta must allow the passage of iodide from the maternal to the fetal circulation for synthesis of thyroxine by the fetal thyroid. The thyroid sodium iodide symporter (NIS) was cloned in 1996 and, although widely distributed among epithelial tissues, early studies failed to detect it in placenta. We demonstrated NIS mRNA in human placenta and in the human choriocarcinoma cell line, JAr. NIS protein was localized to trophoblasts, with a tendency to apical distribution, in sections of human placenta immunostained with a monoclonal antibody against hNIS. We conclude that NIS is expressed in placenta and may mediate placental iodide transport. (C) 2001 Harcourt Publishers Ltd.

The BeWo choriocarcinoma cell line as a model of iodide transport by placenta

Cultured human choriocarcinoma cells of the BeWo line exhibited saturable accumulation of radioiodide. Inhibition by competing anions followed the affinity series perchlorate >= iodide >= thiocyanate, consistent with uptake through the thyroid iodide transporter, NIS, whose messenger RNA was found in BeWo cells, and whose protein was distributed towards the apical pole of the cells. Efflux obeyed first order kinetics and was inhibited by DIDS, an antagonist of anion exchangers including pendrin, whose messenger RNA was also present. In cultures where iodide uptake through NIS was blocked with excess perchlorate, radiolodide accumulation was stimulated by exposure to medium in which physiological anions were replaced by 2-morpholinoethanesulfonic acid (MES), consistent with the operation of an anion exchange mechanism taking up iodide. Chloride in the medium was more effective than sulfate at inhibiting this uptake, matching the ionic specificity of pendrin. These studies provide evidence that the trophoblast accumulates iodide through NIS and releases it to the fetal compartment through pendrin. (c) 2004 Elsevier Ltd. All rights reserved.

Methimazole and propylthiouracil equally cross the perfused human term placental lobule

Propylthiouracil (PTU) is widely believed to cross the placenta less freely than methimazole (MMI) and is therefore regarded as the preferred drug for treatment of hyperthyroidism in pregnancy. Clinical studies comparing the two drugs show, however, no differences in maternal or fetal thyroid function. We investigated transfer from the maternal to the fetal circuit in the isolated perfused term human placental lobule of low and high doses of PTU (4 mu g/mL and 40 mu g/mL) and MMI(1.5 mu g/mL and 15 mu g/mL) in protein-free perfusate and low doses of both drugs with addition of 40 g/L of bovine albumin. Both drugs readily crossed the placenta, reaching equilibrium in all experiments in about 2 h. Drug concentrations in the two circuits fitted a two compartmental model. Transfer kinetics for the two drugs were similar, nonsaturable, and unaffected by addition of albumin. Clearances (mL.min(-1).g(-1), means +/- SD) of PTU from maternal to fetal circuits were: 0.229 +/- 0.110, 0.216 +/- 0.065, and 0.170 +/- 0.032; and for transfer of MMI: 0.165 +/- 0.025, 0.232 +/- 0.153, and 0.174 +/- 0.009 (for low doses without, low doses with, and high doses without albumin, respectively). Clearances of PTU from fetal to maternal circuits were: 0.147 +/- 0.072, 0.109 +/- 0.014, and 0.116 +/- 0.028; and for transfer of MMI: 0.095 +/- 0.029, 0.122 +/- 0.088, and 0.12 +/- 0.005 (in the same experiments). There was no significant difference between drugs or drug doses and no effect of addition of albumin. We conclude that PTU and MMI have similar placental transfer kinetics.

An isolated perfused human placental lobule model for multiple indicator dilution studies

We describe a method for multiple indicator dilution studies in the isolated perfused human placental lobule developed to investigate the relationships between changes in pressure and flow and solute clearance. A peripheral lobule of a human placenta is perfused with a tissue culture-based medium and the perfusate oxygen tension, arterial and venous pressures, pH and perfusion temperature continuously monitored by a computerized system. Flow rates are readily changed. Bolus injections of vascular, extracellular and water space markers, and study compounds can be made into either maternal or fetal circulations, and precisely timed outflow fractions can be collected with computer-controlled fraction collectors, allowing simultaneous determination of concentration-time profiles of each marker. (C) 1997 Elsevier Science Inc.

The pathogenesis of oral lichen planus

Both antigen-specific and non-specific mechanisms may be involved in the pathogenesis of oral lichen planus (OLP). Antigen-specific mechanisms in OLP include antigen presentation by basal keratinocytes and antigen-specific keratinocyte killing by CD8(+) cytotoxic T-cells. Non-specific mechanisms include mast cell degranulation and matrix metalloproteinase (MMP) activation in OLP lesions. These mechanisms may combine to cause T-cell accumulation in the superficial lamina propria, basement membrane disruption, intra-epithelial T-cell migration, and keratinocyte apoptosis in OLP. OLP chronicity may be due, in part, to deficient antigen-specific TGF-beta1-mediated immunosuppression. The normal oral mucosa may be an immune privileged site (similar to the eye, testis, and placenta), and breakdown of immune privilege could result in OLP and possibly other autoimmune oral mucosal diseases. Recent findings in mucocutaneous graft-versus-host disease, a clinical and histological correlate of lichen planus, suggest the involvement of TNF-alpha, CD40, Fas, MMPs, and mast cell degranulation in disease pathogenesis. Potential roles for oral Langerhans cells and the regional lymphatics in OLP lesion formation and chronicity are discussed. Carcinogenesis in OLP may be regulated by the integrated signal from various tumor inhibitors (TGF-beta1, TNF-alpha, IFN-gamma, IL-12) and promoters (MIF, MMP-9). We present our recent data implicating antigen-specific and non-specific mechanisms in the pathogenesis of OLP and propose a unifying hypothesis suggesting that both may be involved in lesion development. The initial event in OLP lesion formation and the factors that determine OLP susceptibility are unknown.

Placental growth hormone is not suppressed by oral glucose loading in normal human pregnancy

Placental growth hormone (PGH) progressively replaces pituitary growth hormone in the maternal circulation from mid-gestation onwards in human pregnancy. Our previous investigations have shown that placental growth hormone concentrations correlate well with foetal growth. Despite the apparent correlation between PGH and birthweight, the physiology of its secretion during pregnancy has not been well defined. We investigated the response of maternal serum PCH to oral glucose loading in pregnant women (n = 24) who demonstrated normal glucose tolerance at a mean gestation of 29 weeks. Mean (SEM) fasting PGH concentrations were high (36.9 [6.4] ng/ml). No suppression of PGH was noted at one, two or three hours after a 75 g oral glucose load. Similarly, no changes were noted in growth hormone binding protein or in calculated free PGH over the course of the glucose tolerance test. As expected, insulin concentrations rose sixfold and insulin like growth factor binding protein 1 concentrations fell by 20% with glucose loading. Cot-relation analysis showed maternal weight, BMI, fasting serum glucose serum insulin to be significantly correlated with the babies' birthweight. Our results support the proposition that PGH concentrations in maternal serum are not Suppressed by oral glucose loading in non-diabetic mothers.

Identification of residues which regulate activity of the STE20-related kinase hMINK

Activity of the STE20-related kinase hMINK was investigated. hMINK was expressed widely, though not ubiquitously, in human tissues: highest levels being found in haematopoietic tissues but also in brain, placenta, and lung. Mutagenesis revealed that T-191. and Y-193 in the substrate recognition loop of the catalytic domain were critical for kinase activity against exogenous substrates and autophosphorylation. A mutation on T-187 showed reduced enzymatic activity against exogenous substrates but retained autophosphorylationactivity. Phosphorylation was confirmed by the use of a phospho-specific T-187 antibody. hMINK activated the JNK signal transduction pathway and optimal JNK activation occurred when the C-terminus was deleted. In addition, overexpression of the C-terminal domain devoid of kinase activity also resulted in significant activation of the JNK pathway. These data suggest that hMINK requires an activation step that dissociates the C terminal, thereby freeing the catalytic domain to interact with substrates. Models for receptor-mediated activation of hMINK are discussed. (C) 2002 Elsevier Science (USA). All rights reserved.

Relationships of Efficiency to Reproductive Disorders in Danish Milk Production: A Stochastic Frontier Analysis

Relationships of various reproductive disorders and milk production performance of Danish dairy farms were investigated. A stochastic frontier production function was estimated using data collected in 1998 from 514 Danish dairy farms. Measures of farm-level milk production efficiency relative to this production frontier were obtained, and relationships between milk production efficiency and the incidence risk of reproductive disorders were examined. There were moderate positive relationships between milk production efficiency and retained placenta, induction of estrus, uterine infections, ovarian cysts, and induction of birth. Inclusion of reproductive management variables showed that these moderate relationships disappeared, but directions of coefficients for almost all those variables remained the same. Dystocia showed a weak negative correlation with milk production efficiency. Farms that were mainly managed by young farmers had the highest average efficiency scores. The estimated milk losses due to inefficiency averaged 1142, 488, and 256 kg of energy-corrected milk per cow, respectively, for low-, medium-, and high-efficiency herds. It is concluded that the availability of younger cows, which enabled farmers to replace cows with reproductive disorders, contributed to high cow productivity in efficient farms. Thus, a high replacement rate more than compensates for the possible negative effect of reproductive disorders. The use of frontier production and efficiency/ inefficiency functions to analyze herd data may enable dairy advisors to identify inefficient herds and to simulate the effect of alternative management procedures on the individual herd's efficiency.

Adherence of Plasmodium falciparum infected erythrocytes to CHO-745 cells and inhibition of binding by protein A in the presence of human serum

Adhesion of erythrocytes infected with the malaria parasite Plasmodium falciparum to human host receptors is a process associated with severe malarial pathology. A number of in vitro cell lines are available as models for these adhesive processes, including Chinese hamster ovary (CHO) cells which express the placental adhesion receptor chondroitin-4-sulphate (CSA) on their surface. CHO-745 cells, a glycosaminoglycan-negative mutant CHO cell line lacking CSA and other reported P. falciparum adhesion receptors, are often used for recombinant expression of host receptors and for receptor binding studies. In this study we show that P. falciparum-infected erythrocytes can be easily selected for adhesion to an endogenous receptor on the surface of CHO-745 cells, bringing into question the validity of using these cells as a tool for P. falciparum adhesin expression studies. The adhesive interaction between CHO-745 cells and parasitized erythrocytes described here is not mediated by the known P. falciparum adhesion receptors CSA, CD36, or ICAM-1. However, we found that CHO-745-selected parasitized erythrocytes bind normal human IgM and that adhesion to CHO-745 cells is inhibited by protein A in the presence of serum, but not in its absence, indicating a non-specific inhibitory effect. Thus, protein A, which has been used as an inhibitor for a recently described interaction between infected erythrocytes and the placenta, may not be an appropriate in vitro inhibitor for understanding in vivo adhesive interactions. (c) 2005 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.

The rat Na+-sulfate cotransporter rNaS2: functional characterization, tissue distribution, and gene (slc13a4) structure

Inorganic sulfate is essential for numerous functions in mammalian physiology. In the present study, we characterized the functional properties of the rat Na+-sulfate cotransporter NaS2 (rNaS2), determined its tissue distribution, and identified its gene (slc13a4) structure. Expression of rNaS2 protein in Xenopus oocytes led to a Na+-dependent transport of sulfate that was inhibited by phosphate, thiosulfate, tungstate, selenate, oxalate, and molybdate, but not by citrate, succinate, or DIDS. Transport kinetics of rNaS2 determined a K-M for sulfate of 1.26 mM. Na+ kinetics determined a Hill coefficient of n=3.0 +/- 0.7, suggesting a Na+:SO42- stoichiometry of 3:1. rNaS2 mRNA was highly expressed in placenta, with lower levels found in the brain and liver. slc13a4 maps to rat chromosome 4 and contains 17 exons, spanning over 46 kb in length. This gene produces two alternatively spliced transcripts, of which the transcript lacking exon 2 is the most abundant form. Its 5' flanking region contains CAAT- and GC-box motifs and a number of putative transcription factor binding sites, including GATA-1, SP1, and AP-2 consensus sequences. This is the first study to characterize rNaS2 transport kinetics, define its tissue distribution, and resolve its gene (slc13a4) structure and 5' flanking region.

Functional characterization and genomic organization of the human Na+-sulfate cotransporter hNaS2 gene (SLC13A4)

Sulfate plays an essential role in human growth and development. Here, we characterized the functional properties of the human Na+-sulfate cotransporter (hNaS2), determined its tissue distribution, and identified its gene (SLC13A4) structure. Expression of hNaS2 protein in Xenopus oocytes led to a Na+-dependent transport of sulfate that was inhibited by thiosulfate, phosphate, molybdate. selenate and tungstate, but not by oxalate, citrate, succinate, phenol red or DIDS. Transport kinetics of hNaS2 determined a K, for sulfate of 0.38 mM, suggestive of a high affinity sulfate transporter. Na+ kinetics determined a Hill coefficient of 1.6 +/- 0.6, suggesting a Na: SO42- stoichiometry of 2:1. hNaS2 mRNA was highly expressed in placenta and testis, with intermediate levels in brain and lower levels found in the heart, thymus, and liver. The SLC13A4 gene contains 16 exons, spanning over 47 kb in length. Its 5'-flanking region contains CAAT- and GC-box motifs, and a number of putative transcription factor binding sites, including GATA-1, AP-1, and AP-2 consensus sequences. This is the first study to characterize hNaS2 transport kinetics, define its tissue distribution, and resolve its gene (SLC13A4) structure and 5' flanking region. (C) 2004 Elsevier Inc. All rights reserved.

Population pharmacokinetics of metformin in late pregnancy

The pharmacokinetic disposition of metformin in late pregnancy was studied together with the level of fetal exposure at birth. Blood samples were obtained in the third trimester of pregnancy from women with gestational diabetes or type 2 diabetes, 5 had a previous diagnosis of polycystic ovary syndrome. A cord blood sample also was obtained at the delivery of some of these women, and also at delivery of others who had been taking metformin during pregnancy but from whom no blood had been taken. Plasma metformin concentrations were assayed by a new, validated, reverse-phase HPLC method, A 2-compartment, extravascular maternal model with transplacental partitioning of drug to a fetal compartment was fitted to the data. Nonlinear mixed-effects modeling was performed in'NONMEM using FOCE with INTERACTION. Variability was estimated using logarithmic interindividual and additive residual variance models; the covariance between clearance and volume was modeled simultaneously. Mean (range) metformin concentrations in cord plasma and in maternal plasma were 0.81 (range, 0.1-2.6) mg/L and 1.2 (range, 0. 1-2.9) mg/L, respectively. Typical population values (interindividual variability, CV%) for allometrically scaled maternal clearance and volume of distribution were 28 L/h/70 kg (17.1%) and 190 L/70 ka (46.3%), giving a derived population-wide half-life of 5.1 hours. The placental partition coefficient for metformin was 1.07 (36.3%). Neither maternal age nor weight significantly influenced the pharmacokinetics. The variability (SD) of observed concentrations about model-predicted concentrations was 0.32 mg/L. The pharmacokinetics were similar to those in nonpregnant patients and, therefore, no dosage adjustment is warranted. Metformin readily crosses the placenta, exposing the fetus to concentrations approaching those in the maternal circulation. The sequelae to such exposure, ea, effects on neonatal obesity and insulin resistance, remain unknown.

Molecular cloning and characterization of the mouse Na+ sulfate cotransporter gene (Slc13a4): structure and expression

Sulfate is an essential ion required for numerous functions in mammalian physiology. Due to its hydrophilic nature, cells require sulfate transporters on their plasma membranes to allow entry of sulfate into cells. In this study, we identified a new mouse Na+-sulfate cotransporter (mNaS2), characterized its tissue distribution and determined its cDNA and gene (Slc13a4) structures. mNaS2 mRNA was expressed in placenta, brain, lung, eye, heart, testis, thymus and liver. The mouse NaS2 cDNA spans 3384 nucleotides and its open frame encodes a protein of 624 amino acids. Slc13a4 maps to mouse chromosome 6131 and contains 16 exons, spanning over 40 kb in length. Its 5'-flanking region contains CART- and GC-box motifs and a number of putative transcription factor binding sites, including GATA-1, MTF-1, STAT6 and HNF4 consensus sequences. This is the first study to define the tissue distribution of mNaS2 and resolve its cDNA and gene structures, which will allow us to investigate mNaS2 gene expression in vivo and determine its role in mammalian physiology.