Annamalai,Loganath
Email Address
obgannam@nus.edu.sg
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Publication Over-expression and secretion of angiogenin in intrauterine growth retardation placenta(2003-04-01) Rajashekhar, G.; Loganath, A.; Roy, A.C.; Wong, Y.C.; OBSTETRICS & GYNAECOLOGYHuman angiogenin is a potent inducer of neovascularization. There is a strong evidence to suggest that it might be involved in morphological and angiogenic changes in the placenta, that are necessary for a successful fetal outcome during pregnancy. However, its precise role in the pathogenesis of abnormal pregnancies is yet unknown. Intrauterine growth retardation (IUGR), an abnormal pregnancy is not a specific disease entity per se, but rather a manifestation of many possible fetal and maternal disorders. In this study, we demonstrated, for the first time, that placental explants in vitro secrete significantly elevated levels of angiogenin in placental tissues from patients with IUGR. We also observed enhanced mRNA expression in placenta from these patients. In addition, using the immunohistochemical methods, we observed identical staining of angiogenin to villous syncytiotrophobalst and fetal endothelial cells in both IUGR and normal placenta. Functionally active placental explants were used to detect immunoreactive angiogenin in conditioned media of all the samples from IUGR placenta and normal term group. The mean levels of angiogenin secreted by IUGR placenta were 1.4-, 1.6-, and 1.3-fold higher (P < 0.01) than normal term samples at 24, 48, and 72 hr of culture, respectively. Expression profiles of angiogenin from term and IUGR cases are in agreement with its mRNA levels and immunoblot analysis. In conclusion, the significant elevated levels of angiogenin in IUGR placenta may provide a molecular mechanism for the abnormal placental development. © 2003 Wiley-Liss, Inc.Publication Evidence for de novo cholesterol synthesis by term human fetal amnion and chorion: A comparative study using the reverse-isotope dilution technique(2000) Loganath, A.; Peh, K.L.; Wong, Y.C.; Ng, S.C.; OBSTETRICS & GYNAECOLOGYThe cholesterol biosynthetic activity was assessed using [2-14C]-acetate as substrate in the homogenates of amnion and chorion obtained from women (n = 6, age 26-39 years) after spontaneous labour at term (37-40 weeks of gestation) having uncomplicated pregnancies. Reverse-isotope dilution analysis gave positive identification of [14C]-cholesterol acetate in all incubations of viable tissues. This metabolite was not evident in heat-denatured homogenates which served as controls. The extent of enzymic conversion for amnion at 2.6 x 10-3 to 0.19% was persistently higher than that of the chorion at 1.7 x 10-3 to 9.0 x 10-3%. The results indicate that human term fetal membranes possess the full complement of enzymes to catalyze the transformation of acetate to cholesterol. This study provides evidence that fetal membranes possess the capacity for de novo cholesterol biosynthesis, the sterol being essential for steroidogenesis as well as in embryo viability during pregnancy. Copyright (C) 2000 S. Karger AG, Basel.Publication Determination and occurrence of polybrominated diphenyl ethers in maternal adipose tissue from inhabitants of Singapore(2005) Li, Q.Q.; Loganath, A.; Chong, Y.S.; Obbard, J.P.; CHEMICAL & BIOMOLECULAR ENGINEERING; OBSTETRICS & GYNAECOLOGYPolybrominated diphenyl ethers (PBDEs), as a specific group of brominated flame retardants (BFR), are used in a variety of consumer products including electronics and household furnishings. In recent years, a marked increase in the levels of PBDEs in human biological tissues and fluids, especially breast milk, has been reported in several countries. However, few data are available from countries in the Asia-pacific region, including Singapore. This study presents a validated method procedure and the first available data of the concentrations of PBDE congeners: PBDE-47 (2,2,4,4-Tetrabromodiphenyl ether), PBDE-99 (2,2′,4,4′,5-Pentabromodiphenyl ether), PBDE-100 (2,2′,4,4′,6-Pentabromodiphenyl ether), PBDE-153 (2,2′,4,4′,5,5′-Hexabromodiphenyl ether), PBDE-154 (2,2′,4,4′,5,6′-Hexabromodiphenyl ether) in maternal adipose tissue collected from inhabitants of Singapore. Microwave-assisted extraction (MAE) of PBDEs spiked adipose tissues coupled with GC-MS analysis achieved comparable recoveries to a conventional Soxhlet Extraction (SE) procedure of between 70 and 130%. MAE also yielded comparable precision data (variance less than 13%) relative to the SE procedure. Spiked Carbon-13 PBDE congeners were also used as surrogates for MAE quality assurance and confirmed the efficiency of the procedure. PBDE congeners were detected in all of 16 maternal adipose tissues collected in Singapore, where levels were comparable to available data from Belgium. © 2005 Elsevier B.V. All rights reserved.Publication Cord plasma α-fetoprotein values and neonatal jaundice(1984) Tan, K.L.; Loganath, A.; Roy, A.C.; Goh, H.H.; Karim, S.M.; Ratnam, S.S.; PAEDIATRICS; OBSTETRICS & GYNAECOLOGYPublication Expression of 3β-hydroxysteroid dehydrogenase-5,4-en isomerase activity by infiltrating ductal human breast carcinoma in vitro(1998) Gunasegaram, R.; Peh, K.L.; Loganath, A.; Ratnam, S.S.; OBSTETRICS & GYNAECOLOGYPublication Upper genital tract fluid oestradiol-17 beta, progesterone and testosterone concentrations during the menstrual cycle.(1989-11) Chew, P.C.; Loganath, A.; Peh, K.L.; Gunasegaram, R.; Ratnam, S.S.; OBSTETRICS & GYNAECOLOGYThis study was to obtain evidence whether a cyclical pattern in the concentrations of oestradiol-17 beta, progesterone and testosterone exists in the upper genital tract fluid of women with normal menstrual cycles. The steroid concentrations at proliferative and luteal phases were n = 20 vs 17, 54.5-190.0 vs 44.2-827.1 pg/ml; 0.27-3.3 vs 3.4-46.5 ng/ml and 41.9-734.8 vs 85.7-991.2 pg/ml, respectively. The results were analysed according to Mann-Whitney U test. Significantly higher concentrations of oestradiol-17 beta (p = 0.0036) and progesterone (p = 0.0001) were found. The results suggest the existence of a cyclical variation and point to the ovary as the main source of output of the steroids.Publication Comparison of AFP and β-hCG levels in infiltrating duct mammary carcinoma at different stages of malignancy(1988) Loganath, A.; Peh, K.L.; Gunasegaram, R.; Thiagaraj, D.; Cheah, E.; Kottegoda, S.R.; Ratnam, S.S.; OBSTETRICS & GYNAECOLOGYPublication Mitochondrial gene mutations in gestational diabetes mellitus(2000) Chen, Y.; Liao, W.X.; Roy, A.C.; Loganath, A.; Ng, S.C.; OBSTETRICS & GYNAECOLOGYMitochondrial DNA mutations have been implicated in many diseases including diabetes mellitus. Although gestational diabetes mellitus (GDM) has been suggested to have genetic determinant and to be etiologically indistinct with non-insulin-dependent diabetes mellitus (NIDDM), its association with mitochondrial gene mutations is still unknown. In this study, 137 patients with GDM and 292 non-diabetic pregnant controls were examined for mitochondrial DNA mutations from the nucleotide 3130-4260 encompassing tRNA- Leu gene and adjacent NADH dehydrogenase 1 gene by polymerase chain reaction, single-stranded conformation polymorphism, restriction fragment length polymorphism and DNA sequencing. One heteroplasmic mutation at the position of 3398 (T-C), which changed a highly conserved methionine to threonine in NADH dehydrogenase subunit 1, was identified in 2.9% GDM patients but not in the controls, indicating its association with GDM (P = 0.01). Two novel mutations, a heteroplasmic C3254A and a homoplasmic A3399T, were also found in GDM subjects, the functional meaning of which merits further investigation. G3316A and T3394C mutations implicated in NIDDM, were seen at higher frequencies in patients with GDM than the controls. Our results suggest that mitochondrial DNA mutations may contribute to the development of GDM in some patients. (C) 2000 Elsevier Science Ireland Ltd.Publication Paternal contribution of HLA-G*0106 significantly increases risk for pre-eclampsia in multigravid pregnancies(2008) Tan, C.Y.; Ho, J.F.V.; Chong, Y.S.; Loganath, A.; Chan, Y.H.; Ravichandran, J.; Lee, C.G.; Chong, S.S.; PAEDIATRICS; BIOCHEMISTRY; OBSTETRICS & GYNAECOLOGYPublication Enzymatic transformation in vitro of 1,2,6,7,16,17-[3H]-progesterone to [3H]-testosterone by human umbilical cord(1991) Gunasegaram, R.; Loganath, A.; Peh, K.L.; Chow, W.P.; Chew, P.C.T.; Ratnam, S.S.; OBSTETRICS & GYNAECOLOGY