Biomedical subjects

B Thilaganathan

Publications and source records attributed to B Thilaganathan.

82 records · Page 5Linked to original sources

PubMed1992

Erythroblastosis in birth asphyxia.

The pH and erythroblast count in umbilical venous blood were measured in 27 term neonates with normal birth weights. In seven cases, infants were admitted to the neonatal intensive care unit because of birth asphyxia, and the findings in these cases were compared to the values of the 20 non-asphyxiated neonates that were delivered either vaginally (n = 10) or by elective Cesarean section (n = 10). The umbilical venous blood pH in the asphyxiated group was significantly lower than that in the control group of infants that were delivered by Cesarean section, but not significantly different from the controls that were delivered vaginally. In contrast, the erythroblast count in the asphyxiated group was significantly higher than that in the controls, irrespective of the mode of delivery. These findings suggest that cord blood erythroblast count at delivery may provide a better measure of fetal tissue hypoxia than umbilical venous pH.

Journal Article↗

PubMed1992

Fetal plasma erythropoietin concentration in red blood cell-isoimmunized pregnancies.

OBJECTIVE: The aim of this study was to investigate the relationship between fetal anemia, plasma erythropoietin concentration, and erythroblastosis in red blood cell-isoimmunized pregnancies. STUDY DESIGN: Fetal plasma erythropoietin concentration in umbilical venous blood samples from 68 red blood cell-isoimmunized pregnancies at 18 to 35 weeks' gestation was measured. Measurements were compared with the appropriate reference range with gestation, and associations with blood pH, erythroblast count, and hemoglobin concentration were examined. RESULTS: The mean fetal plasma erythropoietin concentration and erythroblast count in red blood cell-isoimmunized pregnancies were significantly increased only in severe fetal anemia (hemoglobin deficit > 7 gm/dl). Furthermore, some severely anemic fetuses were hydropic and acidemic. The degree of increase in plasma erythropoietin was significantly associated with both fetal acidemia and, more strongly, fetal erythroblastosis. CONCLUSION: These findings suggest that in fetuses from red blood cell-isoimmunized pregnancies the ability to prevent tissue hypoxia is present until anemia becomes severe, presumably by an increase in cardiac output and tissue perfusion. In severe anemia tissue hypoxia occurs, and the data indicate that fetuses respond by increasing erythropoietin production from at least 20 weeks' gestation. Furthermore, more accurate assessment of tissue oxygenation may be obtained by measuring the erythroblast count rather than the blood pH.

Anemia↗

PubMed1992

Fetal and maternal erythropoietin levels in normal pregnancy.

In a cross-sectional study of 120 pregnancies undergoing cordocentesis for prenatal diagnosis (n = 90) or elective caesarean section (n = 30), the umbilical cord and maternal venous plasma erythropoietin (Epo) concentrations were measured. Fetal Epo levels increased from a mean of 4 mU/ml at 16 weeks to 13 mU/ml at 40 weeks' gestation. There were no significant associations between fetal plasma Epo concentration and fetal blood gases, haemoglobin concentration, oxygen content or erythroblast count. The maternal plasma Epo concentration (mean = 14 mU/ml, range 1-77 mU/ml) did not change with gestation but was significantly higher than levels in non-pregnant females (mean = 6.6 mU/ml, range 1-25 mU/ml).

Erythroblasts↗

PubMed1992

Fetal T-lymphocyte subpopulations in normal pregnancies.

Peripheral blood T lymphocyte subpopulations were measured, using a fluorescence-activated cell sorter, in fetal blood samples obtained either by cordocentesis (n = 118) or at elective caesarean section (n = 14). Both the numbers and percentages of the total T lymphocytes (CD3+) and T-helper lymphocytes (CD4+) increased exponentially with gestation from respective means of 46% (1.15 x 10(9)/l) and 29% (0.70 x 10(9)/l) at 16 weeks to a plateau of 75% (3.11 x 10(9)/l) and 54% (2.10 x 10(9)/l) at 34 weeks. Similarly, the number of suppressor/cytotoxic T lymphocytes (CD8+) increased linearly with gestation from a mean of 22% (0.55 x 10(9)/l) at 16 weeks to 24% (0.96 x 10(9)/l) at 40 weeks; there were no natural cytotoxic T lymphocytes (CD3+CD56+) in any of the fetal blood samples. The helper-to-suppressor T lymphocyte ratio (CD4/CD8) increased exponentially with gestation from a mean of 1.22 at 16 weeks to 2.57 at 28 weeks. The alterations in T lymphocyte subpopulations were accompanied by changes in the expression of CD45RA, L-selectin, CD25 and HLA-DR. These alterations in T lymphocyte subpopulations with gestation reflect the pattern of maturation and development of the fetal cell-mediated immune system.

Antigens, Differentiation, T-Lymphocyte↗

PubMed1989

Cordocentesis in the investigation of fetal erythropoiesis.

Fetal blood hemoglobin concentration and erythrocyte, reticulocyte, and erythroblast counts were determined in umbilical cord samples obtained from 194 pregnancies at 17 to 40 weeks' gestation. The fetuses sampled were undergoing prenatal diagnosis and were subsequently found not to be affected by the condition investigated. The hemoglobin concentration and erythrocyte count increased linearly with gestation from respective means of 11 gm/dl and 2.5 x 10(12)/L at 17 weeks to 15.5 gm/dl and 4.5 x 10(12)/L at 40 weeks. The erythroblast count decreased exponentially from a mean of 83/100 leukocytes at 17 weeks to 4/100 leukocytes at 40 weeks. The reticulocyte count decreased linearly from a mean of 27.5 x 10(9)/L or 10/100 red blood cells at 17 weeks to 17.5 x 10(9)/L or 4/100 red blood cells at 40 weeks.

Blood Specimen Collection↗

PubMed1988

Erythroblastosis and reticulocytosis in anemic fetuses.

The fetal blood erythroblast and reticulocyte counts were determined in umbilical cord samples obtained at 17 to 36 weeks' gestation from 127 pregnancies complicated by red blood cell isoimmunization. The reticulocyte count increased linearly with fetal anemia, and the erythroblast count increased exponentially. Significant erythroblastosis was observed only when the hemoglobin concentration deficit was greater than 7 gm/dl. Of the 52 fetuses with a hemoglobin concentration deficit greater than 7 gm/dl, 35 had ultrasonographic evidence of hydrops. These data suggest that medullary hematopoiesis is stimulated by mild anemia and that recruitment of extramedullary sites occurs when anemia is severe. Extensive hepatic erythropoiesis may be the cause of fetal hydrops in red blood cell isoimmunization.

Anemia↗

PubMedDate not supplied

Fetal B lymphocyte subpopulations in normal pregnancies.

In 190 pregnancies undergoing cordocentesis for prenatal diagnosis (n = 174) or elective caesarean section (n = 16), fetal peripheral blood B lymphocyte subpopulations were measured using a fluorescence-activated cell sorter (FACScan). The total number of B lymphocytes and polyreactive CD5+ B cells increased exponentially with gestation from respective means of 0.33 x 10(9)/l and 0.25 x 10(9)/l at 17 weeks to a plateau of 0.66 x 10(9)/l and 0.54 x 10(9) at 36 weeks, remaining at that level thereafter. The number of mature CD10- and active CD23+ B lymphocytes increased linearly from a mean of 0.07 x 10(9)/l and 0.11 x 10(9)/l at 17 weeks to 0.24 x 10(9)/l and 0.37 x 10(9)/l, respectively, at 40 weeks. As expected, all B lymphocytes expressed the HLA-DR antigen from as early as 16 weeks gestation. These alterations in specific B lymphocyte subpopulations reflect the pattern of maturation and development of the fetal humoral immune system.

Antigens, CD↗

PubMedDate not supplied

Fetal blood mononuclear cell division in normal and pathological pregnancies.

Fetal blood mononuclear cell division was measured using flow cytometry in 53 normal pregnancies and 51 pathological pregnancies complicated either by anaemia due to red blood cell isoimmunisation (RCI: n = 21), intrauterine growth retardation (SGA: n = 13) or abnormal karyotype (n = 17). In normal pregnancy, mononuclear cell division rates decreased with gestational age from a mean of 1.8% at 18 weeks to 1% at 40 weeks. Furthermore, there was a significant association between cell division and erythroblast count. The rates of cell division and erythroblast count were significantly increased in the chromosomally abnormal fetuses, and significantly decreased in the transfused RCI fetuses compared to the controls. Although the erythroblast count was elevated in the SGA fetuses, the mononuclear cell division was not significantly different from the controls. Fetal blood mononuclear cell division is elevated in early pregnancy and in chromosomally abnormal fetuses, probably as a consequence of increased numbers of circulating haemopoietic precursors. Mononuclear cell division is decreased in transfused RCI fetuses as a consequence of suppressed erythropoiesis. In SGA fetuses, despite the increased erythropoietic stimulation and erythroblastosis, cell division is not increased.

Anemia↗

PubMedDate not supplied

Maternal peripheral blood lymphocyte subpopulations in normal and pathological pregnancies.

Flow cytometry was used to determine lymphocyte subpopulations in maternal blood from 143 pathological pregnancies: 50 with fetal aneuploidy; 32 with missed abortions; 12 with ectopic pregnancies; 20 with multi-fetal pregnancies, and 29 with pregnancies complicated by intrauterine growth retardation (IUGR). The values were compared to those of 240 women with normal singleton pregnancies at 8-40 weeks of gestation and 20 non-pregnant controls. In early pregnancy (8-10 weeks), compared to non-pregnant values, there was a decrease in the percentage of CD4+ cells and CD4+ to CD8+ ratio and an increase in the percentage of CD8+ cells. In later pregnancy, the CD4+ cell percentage and CD4+ to CD8+ ratio increased and the CD8+ cell percentage decreased to reach non-pregnant values at term. The percentage of natural killer (CD3- and CD16/56+) cells decreased with gestation, while the percentage of B (CD19+) cells did not change significantly. In IUGR, the percentage of CD4+ cells and CD4+ to CD8+ ratio were decreased, while the percentage of CD8+ cells was increased. In contrast, in the groups of missed abortions and ectopic pregnancies, the CD4+ to CD8+ ratio was increased. In multifetal pregnancies and those with fetal aneuploidies there were no significant differences in maternal lymphocyte subpopulations from normals.

Abortion, Missed↗

PubMedDate not supplied

Fetal blood natural killer cells in human pregnancy.

Flow cytometry was used to determine the number of circulating natural killer (NK) cells in 170 pregnancies undergoing cordocentesis for prenatal diagnosis at 17-38 weeks gestation and 16 undergoing cardiocentesis before social termination of pregnancy at 13-17 weeks. The number of NK cells decreased exponentially with gestation from a mean of 0.26 x 10(9)/l at 13 weeks to 0.09 x 10(9)/l at 38 weeks (r = -0.356, p < 0.001). When expressed as a percentage of the total number of lymphocytes, the proportion of NK cells decreased from a mean of 29% at 13 weeks to 6% at 38 weeks (r = 0.680, p < 0.0001). These data suggest that in early pregnancy the fetal immune response is dependent on innate rather than adaptive mechanisms.

Cordocentesis↗