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Biomedical subjects

D Chia

Publications and source records attributed to D Chia.

At least 37 records · Page 2Linked to original sources
PubMed1994

A new simplified method of gene typing.

SSP-PCR (sequence-specific primer) DNA typing was performed in Terasaki trays using 1.5 microliters of DNA, and the ethidium-stained PCR product was measured by direct fluorometric reading. Elimination of the gel electrophoresis step greatly simplified the SSP method. 17 serological DR specificities were discriminated for 239 DNA samples utilizing the new method, standard SSP, sequence-specific oligonucleotide probe (SSOP), and restriction fragment length polymorphism (PCR-RFLP). Results showed 98% concordance between the SSP-PCR assay and conventional methods. DRB1 alleles were determined by PCR-RFLP in 59 samples, by SSP in 110 samples, and by consensus (all methods) in the remaining samples.

Base Sequence↗
PubMed1993

A new microcellular cytotoxicity test based on calcein AM release.

We present a microtest for cell-mediated immunity, based on the use of the Tarasaki tray and calcein AM vital dye. The number of target cells needed has been reduced to 500 per test with a corresponding tenfold reduction in the number of effector cells needed. Results were read at the rate of 1 second per test using a fluorimeter attached to a microscope. Each reaction was also confirmed visually with the use of ethidium bromide as a counterstain for dead cells. The calcein AM dye used to stain the living cells was shown to have a low spontaneous leakage rate--less than 15% in 4 hours at 37 degrees C. Dilutions of targets stained by calcein AM had a linear relationship with measured fluorescence values. NK cells, LAKs, and CTLs were readily detectable by this microtest. Quantitation of killing and kinetic analysis was readily performed with this test system. A significant positive correlation to 51Cr-release results was found. We conclude that the microtest should find wide application in studies of cell-mediated immunity.

Cell Line↗
PubMed1993

In vitro studies to explain high renal allograft survival in IgA nephropathy patients.

The pretransplant sera of 27 IgA nephropathy (N) kidney transplant patients were investigated for antibodies to the HLA molecule, together with 104 sera from non-IgA N patients and 60 controls. IgA antibodies to HLA were found in 61% of IgA N patients and 2% of non-IgA N patients. IgA N patients with IgA antibodies to HLA had a 100% 2-year cadaver donor graft survival rate compared with 70% in those without IgA antibodies. Patients with IgG antibodies to HLA without accompanying IgA antibodies had the worst graft survival rates. We propose that IgA anti-HLA contributes to the high kidney graft survival in IgA N patients by blocking IgG antibodies or inhibiting cellular immune response.

Adult↗
PubMed1993

The role of IgA anti-HLA class I antibodies in kidney transplant survival.

The unusually high 88% one-year cadaver kidney graft survival rate in patients with IgA nephropathy (IgAN) prompted us to investigate the influence of IgA anti-HLA class I antibodies on subsequent graft survival. We found that patients with various original diseases with IgA antibodies to the HLA molecule had high 91% one-year graft survival compared with 58% one-year survival for those who did not have preformed IgA antibodies against the HLA molecule prior to transplantation (P < 0.0005). The IgA antibodies were detected by reaction with class I HLA molecules isolated by capture with monoclonal antibody and detected with an enzyme-linked immunosorbent assay. In contrast, IgG antibodies to the HLA molecule resulted in a lower one-year graft survival rate (74%) than in those patients without IgG antibodies (87%) (p = 0.08). IgA antibodies to the HLA molecule, when present, tended to react at a high frequency on a random lymphocyte panel. These findings suggest that sensitization resulting in IgA anti-HLA antibodies may counteract the deleterious effect of an IgG antibody response in clinical kidney transplantation.

Cells, Cultured↗
PubMed1993

Development and characterization of a novel anti-fucosylated antigen monoclonal antibody YB-2 and its usefulness in the immunohistochemical diagnosis of colorectal cancer.

A novel monoclonal antibody, YB-2 was obtained after immunization of mice with fucosylated antigens isolated from human saliva. The antibody was demonstrated to react with Y (Fuc alpha 1-->2Gal-beta 1-->4[Fuc alpha 1-->3]GlcNAc beta),Leb (Fuc alpha 1-->2Gal beta 1-->3[Fuc alpha 1-->4]GlcNAc beta) and H type 2 (Fuc alpha 1-->2Gal-beta 1-->4GlcNAc beta) antigens, but not with H type 1 (Fuc alpha 1-->2Gal beta 1-->3GlcNAc beta), Lea (Gal beta 1-->3[Fuc alpha 1-->4]GlcNAc beta), X (Gal beta 1-->4[Fuc alpha 1-->3]GlcNAc beta) or with non-fucosylated antigens. Inhibition assays of YB-2 antibody with such reactive antigens showed that YB-2 antibody preferentially reacted with Y antigen. Formalin-fixed and paraffin-embedded sections prepared from normal and malignant colorectal tissues were examined immunohistochemically with YB-2. The positive rates of staining with YB-2 antibody were 88.6% in malignant and 12.0% in normal tissues. The expression of fucosylated antigens detected by YB-2 antibody seemed to be correlated with survival among patients with primary colorectal cancer. Therefore, YB-2 antibody could be useful as an immunochemical tool for diagnosis and evaluation of the prognosis of colorectal cancer.

Antibodies, Monoclonal↗
PubMed1993

Direct detection of PCR products for HLA class II typing.

Direct detection of the PCR, or DD-PCR is proposed as an efficient method for performing PCR assays. Following the PCR reaction, ethidium homodimer dye is added to the reaction mixture and read by fluorescence. The dye step circumvents the necessity of running reactions on agarose gel electrophoresis, which is the current standard. This simple modification should find wide application for assays utilizing the PCR reaction. Here we show the ready detection of HLA class II polymorphism.

Base Sequence↗
PubMed1993

Fetal blood sampling and its complications related to the indications for fetal blood sampling.

A prospective study on fetal blood sampling (FBS) was conducted in the Fetomaternal Medicine Division of the Department of Obstetrics and Gynaecology at the National University Hospital, Singapore. FBS was performed on 159 occasions in 156 women between January, 1988 and December, 1991. The aim of this study was to identify the factors that were associated with an adverse outcome following the procedure. Twenty four abnormal pregnancies were terminated; of the remaining 132 desired pregnancies the overall pregnancy loss was 44 (33.3%), which included those within 2 weeks and those after 2 weeks of the procedure and neonatal deaths. Fetal loss occurring within 2 weeks of the procedure is considered a procedure-related loss which occurred in 19 (14.3%) of the 132 pregnancies. When the fetal loss occurred within 2 weeks of the procedure 89% had a major abnormality on ultrasonographic scanning. The conclusion from our study is that the risks of FBS were increased in abnormal pregnancies, most likely due to the underlying pathology.

Blood Specimen Collection↗
PubMed1992

Appearance of the tumor marker CA 19-9 in liver transplant patients during rejection episodes.

The tumor marker CA 19-9 was shown to be elevated in liver transplant patients, particularly during rejection. Serial serum samples taken from 24 patients after liver transplantation were examined for tumor markers CA 19-9, SLEX, CEA, and TNF-alpha. During rejection, 85% of the patients had elevated levels of CA 19-9. Patients with early rejection had persistently higher levels than patients without rejection. The serum levels were low in nonrejecting patients compared with those with rejection. Thus, the CA 19-9 marker cannot be considered a specific tumor marker. It may, however, be an indicator of an immune response or it may be a byproduct of an inflammatory reaction to a tumor or a transplant.

Antigens, Tumor-Associated, Carbohydrate↗
PubMed1992

Accuracy in diagnosis of ectopic pregnancy by transvaginal ultrasonography.

Forty patients suspected to have ectopic pregnancy by transvaginal ultrasonography had surgery. 77.5% were confirmed to have ectopic pregnancy and 10% had other abnormal pelvic findings. The transvaginal approach appears to enable us to diagnose ectopic pregnancy at an earlier date, with the earliest diagnosis made at 4 weeks 0 days of amenorrhoea. In cases of confirmed ectopic pregnancy, the presence of a complex adnexal mass was the most common feature seen on transvaginal ultrasound and its predictability of ectopic pregnancy is enhanced by a concomitant finding of an empty uterus (95%) or free fluid in the Pouch of Douglas (94%) in the presence of a positive hCG test. The significance of transvaginal ultrasound features, and the advantages of transvaginal over transabdominal ultrasound, are discussed.

Female↗
PubMed1992

A case report: vesico-rectal fistula with ano-urethral atresia.

Vesico-rectal fistula is a rare congenital abnormality causing severe early second trimester oligohydramnios. Prenatal diagnosis of such a case is reported here. Ultrasound diagnosis could be aided by transabdominal amnio-infusion and, if necessary, fetal intraperitoneal saline installation. In a karyotypically normal fetus with normal somatic growth, demonstration of normal fetal kidneys together with a functioning urinary bladder, in presence of severe oligohydramnios, is very suggestive of the diagnosis. Since pulmonary hypoplasia is the major cause of neonatal mortality in these cases, restoration of normal amniotic fluid volume by serial amnio-infusion was attempted. Although amnio-infusion is an important diagnostic aid in the evaluation of severe midtrimester oligohydramnios, the role of multiple therapeutic amnio-infusion in improving lung growth remains to be evaluated.

Abnormalities, Multiple↗
PubMed1992

Amniocentesis and its complications.

This study was conducted in order to evaluate whether the performance of an experienced operator had any significant influence in reducing the incidence of complications in amniocentesis; 1,459 women had amniocentesis performed under ultrasound guidance; 1,324 were performed by experienced operators and 135 cases by less experienced operators. Complications like fetal loss, blood-stained amniotic fluid, culture failure, multiple needle puncture, leaking liquor, fetal trauma and error in results were compared in the 2 groups. This study demonstrated that amniocentesis performed by an experienced operator decreased the various complications associated with amniocentesis.

Amniocentesis↗
PubMed1992

Umbilical artery blood flow in intra-uterine growth retarded fetuses and fetal outcome: a study of 102 cases.

The 102 fetuses diagnosed by ultrasound to be asymmetrically growth-retarded had blood flow velocity waveforms of the umbilical artery studied. Sixty-two cases had normal blood flow, 28 had abnormal blood flow but with present end-diastolic flow, 8 had absent end-diastolic flow, and 4 had reversal of end-diastolic flow. Comparison was made between the blood flow status and other biophysical methods of antenatal surveillance and perinatal outcome. There is a strong correlation between abnormal blood flow and abnormalities detected by other biophysical methods of antenatal surveillance. Our study shows that fetuses with severe blood flow impairment tend to be more severely growth-retarded and to be delivered earlier. Our results also show abnormal blood flow to be associated with a poor perinatal outcome. Those fetuses with severe impairment of blood flow suffered a high incidence of operative delivery for fetal distress, acidosis at birth, perinatal mortality and morbidity. The association between abnormal blood flow and the 5-minute Apgar score is significant only in those with the severest impairment of blood flow. Our results are in close agreement with similar studies recorded in the literature.

Apgar Score↗
PubMed1991

Binding of IgG to B cell via HLA molecules.

Binding of immunoglobulins to major histocompatibility complex (MHC) molecules was demonstrated by two different assays: the binding of IgG to B cells by flow cytometry, and purified MHC antigens with an Elisa assay. Fc fragment from immune-complex binds to the Fc receptor on B lymphocytes. Here, Fab was also shown to bind to B cells. This binding was inhibited by specific human allo anti-HLA Class I and II sera directed at the polymorphic sites. Thus, in addition to the Fc receptor, MHC can also serve as a binding site for IgG. In an Elisa assay using purified antigens, IgG was shown to bind to HLA Class I and II molecules. Other proteins such as transferrin, human serum albumin, gelatin, etc., did not bind to the MHC proteins. Immunoglobulins bound to MHC molecules by sites on the Fab fragment independent of the hypervariable region. This was demonstrated by the retention of antibody activity even after binding of antibody (anti-lactoferrin) to MHC. The relative avidity between Fab and HLA Class I and II was 4-8 x 10(5) M-1.

B-Lymphocytes↗
PubMed1990

The role of tumor necrosis factor in allograft rejection. I. Evidence that elevated levels of tumor necrosis factor-alpha predict rejection following orthotopic liver transplantation.

Plasma levels of tumor necrosis factor-alpha were measured in 50 adult patients following orthotopic liver transplantation. The mean (+/- SEM) plasma concentration of TNF-alpha was significantly higher in patients experiencing a rejection episode (941 +/- 83 pg/ml) than in those with a stable clinical course (240 +/- 6 pg/ml; P = 0.0001). Peak levels of TNF-alpha were usually found at the time of clinically diagnosed rejection, although elevated levels were observed 1-2 days earlier. First-week peak TNF-alpha levels were significantly higher in patients who suffered graft loss (2146 +/- 788 pg/ml) than in those who were discharged from the hospital without clinical evidence of rejection (581 +/- 93 pg/ml; P = 0.004). TNF-alpha levels were not correlated with white blood cell count (r2 = 0.004), cyclosporine levels (0.01), serum creatinine (0.002), serum bilirubin (0.05), serum SGOT (0.03), or SGPT (0.05). TNF-alpha levels were not elevated in four cases of viral hepatitis occurring after transplantation. We conclude that circulating levels of TNF-alpha are elevated during liver allograft rejection and may precede clinical manifestations. First-week TNF-alpha levels are also useful predictors of long-term graft outcome. Further investigation is required to determine whether this monokine is important in the actual pathogenesis of allograft rejection.

Adolescent↗
PubMed1989

Influence of antimucin antibody in kidney transplantation.

A protein in saliva that is resistant to boiling and has a molecular weight greater than 400,000 daltons was found. Antibody against this antigen occurred naturally in about 20% of 92 normal and 334 dialysis patients. This antibody was associated with an early graft failure in studies of 201 first and 133 multiple graft patients. The effect was strong in male patients and absent in female patients. This antimucin antibody may explain some early graft failure in negative crossmatches.

Antibodies↗
PubMed1988

The second histocompatibility locus in humans.

Even when HLA is completely matched in sibling donor transplants, as many as one third of the transplants are lost in 10 years. This means that a second or third histocompatibility locus plays some role in rejection of kidney grafts. We postulate that the second locus is Lewis. First, because among 18 second cadaver donor transplant patients having Lewis antibodies, the 1-year graft survival rate was 32% compared to 61% in 37 patients without Lewis antibodies (P = .02). The Lewis antibodies presumably were produced in the course of rejection of the first graft and had an effect on the success of the second graft. As indirect evidence, Lewis mismatching would be expected to occur more frequently in black patients than white, and correspondingly, a lower graft survival rate was noted in black patients receiving sibling, parent, and cadaver donor grafts.

Graft Survival↗
PubMed1987

Low kidney graft survival in Lewis negative patients after regrafting and newer matching schemes for Lewis.

Le-cadaver donor kidney transplant recipients regrafted had a 1-year graft survival rate of 0%. This was statistically significantly lower than survival rates in Lea or Leb patients of 60% and 64%, respectively, at 1 year (P = .01 and P = .009). We conclude that if Le- patients had rejected an Le+ graft, a repeated incompatibility should be avoided since the recipients had already demonstrated immunoreactivity against this epitope. Recipients being confronted with an Le group mismatch in the first graft often have successful grafts and the difference in 1-year graft survival of Lea (75%), Leb (76%), and Le- (68%) patients was not statistically significant different. We suggest that the matching scheme for the Le groups be reevaluated. The older method of matching on the basis of Le+ and Le- is probably no longer justified. According to chemical structure, it would appear that Leb should be a universal recipient and Lec a universal donor. This scheme, however, has failed to correspond to interracial transplants between whites and blacks. A matching scheme that requires identity between donor and recipient showed a remarkable correlation with the results between black-to-black, black-to-white, white-to-black and white-to-white transplants.

Blood Group Incompatibility↗