I M Doughty

The University of Manchester, Manchester, England, United Kingdom

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Publications (16)43.94 Total impact

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    ABSTRACT: To compare lactate uptake in the microvillous plasma membrane (maternal facing [MVM]) in term and preterm placentas in intrauterine growth restriction (IUGR) and appropriate weight for gestational age (AGA) controls, and in the basal plasma membrane (fetal facing [BM]) at term. In addition, we examine the expression of monocarboxylate transporters (MCT1 and MCT4). We measured [14C] L-lactate uptakes into vesicles prepared from MVM and BM, stimulated by an inwardly directed H+ gradient. MCT expression was examined by Western blotting. In term placentas, mean (+/- SE) [14C] L-lactate uptake into MVM vesicles of the IUGR (n = 6) and AGA (n = 11) groups at initial rate was similar (15.4 +/- 2.3 versus 15.0 +/- 1.1 pmol/mg protein/20 s). In preterm placentas, in IUGR (n = 3) and AGA (n = 3) groups, [14C] l-lactate uptake into MVM was also not significantly different. In BM vesicles from term placentas, [14C] L-lactate uptake was significantly lower in IUGR (n = 5) than in AGA (n = 6) controls (3.6 +/- 0.4 versus 5.6 +/- 0.6 pmol/mg protein/20 s, P <.05). MCT1 and MCT4 were expressed in BM vesicles, but there was no difference in expression between the IUGR and AGA groups. These findings suggest that in IUGR placental lactate transport capacity in the BM is reduced, which may adversely affect placental lactate clearance.
    Journal of the Society for Gynecologic Investigation 08/2006; 13(5):357-63. · 2.26 Impact Factor
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    ABSTRACT: We investigated the polarization of l-lactate transport in human syncytiotrophoblast by measuring uptake of [(14)C] l-lactate by both microvillous (maternal-facing; MVM) and basal (fetal-facing; BM) plasma membranes. [(14)C] l-lactate uptake by MVM and BM was stimulated in the presence of an inwardly directed H(+)gradient, with a significantly higher uptake in MVM than in BM at initial rate (15.4+/-2.3 vs 5.6+/-0.6 pmol/mg protein/20 sec). Stereospecific inhibition was observed in MVM, with a higher affinity for l-lactate compared with d-lactate. In BM, there was no difference in the inhibition by these two stereoisomers. Inhibition of lactate uptake in both MVM and BM by 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS), an inhibitor of monocarboxylate transporter (MCT) activity, indicated MCT-mediated mechanisms across both membranes. Kinetic modelling supported a two-transporter model as the best fit for both MVM and BM, the K(m)of the major component being 6.21 mm and 25.01 mm in MVM and BM respectively. Western blotting and immunolocalization examining the distribution of MCT1 and MCT4, showed that MCT expression was polarized, MCT1 being predominantly localized to BM and MCT4 showing greater abundance on MVM. CD147, a chaperone protein for MCT1 and MCT4, was equally expressed by both membranes. These studies demonstrate that the opposing plasma membranes of human syncytiotrophoblast are polarized with respect to both MCT activity and expression.
    Placenta 08/2004; 25(6):496-504. · 3.12 Impact Factor
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    ABSTRACT: The effect of gestational age, low birth weight, and umbilical plasma pH on the activity and expression of the Na(+)/H(+) exchanger in the microvillous plasma membrane (MVM) of the placental syncytiotrophoblast was investigated. MVM were isolated from placentas of fetuses delivered in the first and second trimesters and from appropriately grown for gestational age (AGA) and small for gestational age (SGA) babies born at term. Na(+)/H(+) exchange activity (amiloride-sensitive Na(+) uptake) was higher (p<0.05) in second trimester and term AGA MVM versus first trimester MVM (median [range]: 1.80 [1.01-3.03], 1.72 [1.16-3.15] versus 1.48 [0.92-1.66] nmol/mg protein/30s, respectively, n = 6, 12, and 9). As regards exchanger isoforms, Western blotting showed that NHE1 expression did not change across gestation, but NHE2 and NHE3 expression were lower (p<0.01) in the first and second trimesters than in term AGA MVM. There were no differences in Na(+)/H(+) exchanger activity or in NHE1-3 expression in term AGA MVM versus SGA (n = 11) MVM. There was no correlation between exchanger activity and umbilical artery or vein plasma pH, although with a relatively small number of samples (n = 12 and 15, respectively). We conclude that there is differential regulation of the activity and expression of Na(+)/H(+) exchanger isoforms in the MVM over the course of gestation in normal pregnancy; this is not affected in pregnancies resulting in SGA babies at term.
    Pediatric Research 12/2000; 48(5):652-9. · 2.67 Impact Factor
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    ABSTRACT: There are significant changes in the activity of some placental transporters between first trimester and term. However, chloride transport has previously been studied only in the term placenta. Therefore. in this study, we investigated chloride transport mechanisms in syncytiotrophoblast microvillous membrane (MVM) vesicles from first trimester human placentas and compared them with those in vesicles from term placentas. 36Cl- uptake into MVM vesicles was linear up to 45 s and had reached equilibrium by 1 h for both first trimester and term vesicles. In first trimester MVM at 0 mV, 0.1 mM diisothiocyano-2,2'-disulfonic stilbene (DIDS) blocked 25+/-3% (n=8) of 36Cl- uptake at 30 s (initial rate), which was similar to the 30+/-7% (n=6) inhibition by DIDS in term MVM. In the presence of a 25 mV inside-positive electrical potential difference, induced by imposition of a K+ gradient after preincubation with 200 microM valinomycin, 0.5 mM diphenylamine-2-carboxylate (DPC) significantly blocked 30+/-4% of 36Cl- uptake at 30 s by first trimester MVM (p < 0.01); 18+/-5% (n=8) of total uptake was inhibited by DPC but not by DIDS. There was a similar 15+/-3% (n=6) component of 36Cl- uptake by term MVM, which was inhibited by DPC but not by DIDS. Using Western blotting, it was shown that the anion exchanger-1 protein was expressed in first trimester MVM in quantitatively similar amounts to that in term MVM. This study suggests that there is both an anion exchanger and a DPC-sensitive conductance in MVM of first trimester placenta with activity similar to that of term human placenta.
    Pediatric Research 08/1998; 44(2):226-32. · 2.67 Impact Factor
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    I Doughty, Z Mughal, S D'Souza
    Archives of Disease in Childhood 06/1998; 78(5):500. · 3.05 Impact Factor
  • Biochemical Society Transactions 06/1998; 26(2):86-91. · 2.59 Impact Factor
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    ABSTRACT: Chloride transport mechanisms in isolated plasma membrane vesicles were studied to characterize pathways for transcellular transport of chloride. Microvillous membrane (MVM) and basal membranes (BM) vesicles were isolated from term placentae. Western blot analysis of the anion exchanger isoform 1 (AE1) demonstrated that the density of AE1 was 12-fold higher on the MVM compared to the BM. At 30 sec, the Cl- uptake in the absence of a potential difference (p.d.) was 457.3 +/- 69.7 and 111.0 +/- 29.1 pmol/mg protein in MVM and BM, respectively (mean +/- SEM, n=6). Chloride transport pathways were characterized using diisothiocyano-2'2-disulphonic stilbene. (DIDS, 0.1 mM) and diphenylamine-2-carboxylate (DPC, 0.5 mM) in the absence or presence of inside positive membrane potentials. Anion exchange (DIDS-sensitive uptake at zero mV) was found in the MVM only. Both MVM and BM showed increased chloride uptake in the presence of inside positive potentials, suggesting the presence of chloride conductance pathways. The chloride uptake with a 25-mV inside positive p.d. could be inhibited by both DIDS and DPC in MVM and BM. However greater potentials (50 mV) showed no significant inhibition by DIDS or DPC in BM. In conclusion, the anion exchanger is unlikely to contribute significantly to chloride fluxes across BM. The data also suggest the presence of Cl- conductance pathways in both the MVM and BM which are sensitive to both DIDS and DPC.
    Placenta 06/1998; 19(4):315-21. · 3.12 Impact Factor
  • Archives of Disease in Childhood - ARCH DIS CHILD. 01/1998; 78(5):500-500.
  • I Doughty
    Placenta 10/1997; 18(7):609-10. · 3.12 Impact Factor
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    ABSTRACT: To determine the relative contribution of the paracellular and transcellular routes to Cl-transfer, unidirectional maternofetal clearance (Kmf) of 36Cl was compared with Kmf of 51Cr-EDTA and creatinine across the human placenta perfused in vitro. The effect of C1-transport inhibitors 4,4'-diisothiocyanostilbene-2,2-disulfonic acid (DIDS) and diphenylamine-2-carboxylate (DPC) was also investigated. The diffusion coefficient (D) was estimated for each solute by use of an agar diffusion method. At steady state, Kmf/D for 36Cl (0.070 +/- 0.003 cm, n = 23) was not different from that for 51Cr-EDTA (0.070 +/- 0.003 cm, n = 23), and Kmf/D was significantly higher for creatinine than for 36Cl and 51Cr-EDTA (0.087 +/- 0.003 cm, n = 20, P < 0.001). Addition of the inhibitors DIDS and DPC to the perfusates resulted in a small but significant rise in Kmf of 51Cr-EDTA (0.41 +/- 0.03 vs. 0.49 +/- 0.02 ml/min, n = 16, P < 0.0001) and creatinine (0.66 +/- 0.05 vs. 0.74 +/- 0.04 ml/min, n = 13, P < 0.001), but Kmf of 36Cl was unchanged (1.11 +/- 0.07 vs. 1.13 +/- 0.05 ml/min, n = 16). There was no change in Kmf of any solute with time in control experiments. From these data, DIDS- and DPC-inhibitable fractions of Kmf for 36Cl were estimated and together accounted for 16% of total clearance. This study suggests that maternofetal flux of 36Cl across the in vitro perfused human placenta occurs predominantly, but not solely, via paracellular routes.
    The American journal of physiology 01/1997; 271(6 Pt 2):R1701-6. · 3.28 Impact Factor
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    Journal of the Royal Society of Medicine 06/1996; 89(5):289P-90P. · 1.72 Impact Factor
  • Placenta 01/1996; 17(5). · 3.12 Impact Factor
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    ABSTRACT: Cystic fibrosis patients (children and young adults) with Pseudomonas spp. chest infections were treated with meropenem or ceftazidime. This study was the first to investigate the use of meropenem in cystic fibrosis. Meropenem was well tolerated with only transient elevations of serum transaminases. No patient experienced nausea and vomiting, even when meropenem was administered as a bolus injection. This allowed home therapy to be used. Meropenem appeared to be at least as active as ceftazidime even at the low doses used. Patients showed a greater improvement in respiratory function on meropenem than ceftazidime. Only one patient (out of 60 courses) failed to respond to meropenem (98% success rate) compared with two failures out of 21 episodes with ceftazidime (90% success rate). There was little emergence of resistance to meropenem even though some patients were treated up to eight times over a 2 year period.
    Journal of Antimicrobial Chemotherapy 08/1995; 36 Suppl A:135-43. · 5.34 Impact Factor
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    I M Doughty, I Ward, M Schwarz, T J David
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    ABSTRACT: The sweat test, if properly performed, is a reliable tool to assist in the diagnosis of cystic fibrosis. In practice, most errors arise from false positive results. This case serves as a reminder that false negatives may also occur.
    Journal of the Royal Society of Medicine 08/1995; 88(7):417P-418P. · 1.72 Impact Factor
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    Placenta 08/1995; 16(5):469-70. · 3.12 Impact Factor
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    I M Doughty, T J David
    Archives of Disease in Childhood 06/1994; 70(5):451. · 3.05 Impact Factor