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Biomedical subjects

S E Aw

Publications and source records attributed to S E Aw.

At least 37 records · Page 2Linked to original sources
PubMed1990

Use of radionuclides in clinical endocrinology.

Radionuclides provide sensitive reporter molecules for labeling pharmaceuticals. Hormone measurements using radioimmunoassays are commonplace today, increasing our understanding of the pathophysiology of endocrine disease. In turn, hormones tagged with radionuclides are opening studies on new fields of receptor defects both at the receptor site and beyond. Common disorders such as diabetes mellitus, hyperthyroidism and acromegaly have been the first to benefit. Tracer methods to study secretory and clearance rates and the size of metabolic pools are mainly based on the use of radionuclides. DNA probes are useful in unravelling endocrine defects at the genome level. Originally using radioiodine but now an increasing number of newly synthesised radiopharmaceuticals, the individual organs are being visualised more specifically. Among these agents are labelled monoclonal antibodies hunting for neoplasias and analogs of adrenal medullary hormones such as metaiodobenzylguanidine (MIBG). From these studies the therapy of endocrine disorders will ultimately benefit.

Adrenal Glands↗
PubMed1990

TRH stimulation in non-toxic goitres in children and adolescence.

Non-toxic goitres are commonly encountered in clinical practice, but in the majority the aetiology is unknown. Possible aetiological factors include iodine deficiency, biosynthesis defects, immunologic factors or goitrogens. The consequential effect on thyroid function may be clinically undetectable. In this study, serum thyrotrophin (TSH) response to thyrotrophin-releasing hormone (TRH) stimulation was studied in a group of school children with non-toxic goitres to delineate those who may benefit from treatment. Evaluation of possible aetiological factors responsible for goitrogenesis was made by assessment of thyroid autoantibodies and history of exposure to goitrogens.

Adolescent↗
PubMed1990

Tumour markers--a diagnostic and therapeutic perspective.

A number of chemically diverse substances is associated with the malignant transformation of cells. Though none of these can be said to be wholly specific they are operationally useful and this paper is a selective review of some of them. They arise from exposure of previously cryptic epitopes in membranes and secreted molecules and the amplification of normally small quantities of cellular components, such as oncogenes in chromosomes. Antibodies directed to these tumour markers are opening up new avenues of research, diagnosis and therapy of cancer patients. The use of radioisotope labelled antibodies has become sufficiently sensitive and specific to be useful for decision-making in their clinical management.

Biomarkers, Tumor↗
PubMed1990

Significance of tissue polypeptide antigen (TPA) levels in nasopharyngeal cancer.

Serum levels of tissue polypeptide antigen (TPA) were measured in 233 patients at the time of initial diagnosis of nasopharyngeal carcinoma (NPC). Staging of NPC was done using Ho's recommendations together with computerised tomography (CT) of skull findings. The upper limit of normal serum TPA levels in our population was noted to be 112 U/1. In 126 patients with N0 and N1 lymph node staging, the mean level of TPA was 90 U/1 +/- 9 (standard error of mean, sem), while in 107 patients with N2 and N3 nodal disease the mean was 193 U/1 +/- 25.6 (p less than 0.001). Similarly, in 162 patients with T1 and T2 disease, the average TPA level was 119 +/- 13.4 while in 71 patients with T3 disease, the mean TPA was 179 U/1 +/- 29.8 (p less than 0.03). Of 200 patients without metastases, the mean TPA level was 112 +/- 12 U/l whereas in 33 patients with known metastases in liver, lung, bone or brain, the mean TPA level was 290 +/- 51 (p less than 0.001) with liver metastases producing the highest levels. The present study indicates rising values of TPA with advancing nodal and tumour stage in NPC, with high values in metastatic disease. There is a highly significant correlation between nodal stage and TPA levels. TPA is a useful marker in the staging and follow-up of NPC patients.

Adolescent↗
PubMed1986

Autoimmune disease--pathogenesis through molecular mimicry at the tripeptide level.

Increasingly it is being discovered that short segments of proteins can provoke an immune response. Sequential determinants are as important as conformational determinants. It is the thesis of this paper that a string of three amino acid residues (a tripeptide) is antigenic when it is located on a large carrier, that is, when it is part of a protein. Conceptually this has great explanatory power in understanding (a) autoimmune phenomena (b) the intriguing finding that monoclonal antibodies which are supposed to be exquisitely specific cross-react with disparate, non-homologous proteins. Clinical syndromes such as the neuropathies of myeloma, hepatitis and multiple sclerosis are discussed in the light of this concept by computer analysis of the putative antigenic sites of myelin basic protein, hepatitis B and A proteins and measles peptides.

Amino Acid Sequence↗
PubMed1986

99mTechnetium(V) dimercaptosuccinic acid (99mTc(v) DMSA) as a tumour seeking agent in nasopharyngeal carcinoma.

We prepared 99mTechnetium(V) DMSA (pentavalent form) as an imaging agent for eighteen patients with proven nasopharyngeal carcinoma. The head, neck, chest and abdomen were scanned. The nasopharyngeal tumour showed tracer accumulation in only 5 out of the 18 patients (28%). The study indicates that 99mTechnetium(V) DMSA is not a useful radiopharmaceutical for visualising nasopharyngeal tumours although it may have other useful properties.

Carcinoma, Squamous Cell↗
PubMed1986

Postmortem endocrine levels in the vitreous humor.

The vitreous humor and sera from 51 autopsy cases were assayed for progesterone, estradiol, thyroxine, triiodothyronine, TSH, FSH, LH and prolactin. The results indicate that the blood retinal barrier has unique properties of its own. All hormones were measurable in the sera. Progesterone, estradiol, T3 and T4 were not detected despite their lipid solubility and their small molecular size while the larger glycoprotein hormones were easily measureable.

Blood-Retinal Barrier↗
PubMed1986

Tissue polypeptide antigen (TPA) and beta 2-microglobulin (beta 2-MG) as tumour markers in nasopharyngeal cancer.

The levels of tissue polypeptide antigen (TPA) and beta 2 microglobulin (beta 2-MG) were measured in the serum of 38 patients with nasopharyngeal carcinoma (NPC). Using sera from 35 normal volunteers and blood donors, a normal range for these two tumour markers was established. The normal range for TPA was 40-148 IU/L (mean = 93), while that for beta 2-microglobulin was 0.9-2.0 mg/L (mean = 1.3). In the patients with NPC but without known metastases the range was 63-178 IU/L for TPA (mean = 111) and for beta 2-MG, the range was 1.0-3.1 mg/L (mean = 1.7). For those NPC patients with metastases to bone or liver, the mean TPA was 464 IU/L and the mean beta 2-MG was 4.3 mg/L. It appears that TPA and beta 2-MG are useful markers for the monitoring of NPC patients for metastatic disease, particularly TPA.

Adult↗
PubMed1986

Estradiol binding capacity of breast cancer cell line in correlation with cell cycle.

The specific estrogen binding capacity of the MCF-7 cells has been studied throughout the cell cycle. Two days after plating 1-4 X 10(5) cells per well, we observed that cell number, protein concentration and DNA level began to rise but the estrogen binding capacity was lowered. At logarithmic phase the binding increased gradually then sharply to just before confluency. When the cells reached the quiescent phase the estrogen binding capacity fell rapidly. Since estrogen binding capacity of the intact MCF-7 cells varies with different phases in the cell cycle as well as the incubation temperature and time and the plating density, all these factors should be taken into consideration when this cell line is used for hormone studies.

Breast↗
PubMed1986

Quality control of estrogen and progesterone receptor assays.

The intra-laboratory QC materials for estrogen and progesterone receptor assays were prepared using different methods. The most convenient and economical method was found to be the use of lyophilized rat uterine cytosol. The level of receptors remained stable for 12 months when stored at -70 degrees C with the inclusion of 10 mM phenylmethyl sulfonyl-fluoride in the cytosol extraction buffer. For inter-laboratory comparison, we received QC materials from Dr E D Ryan (McMaster University, Canada) monthly and our results fell within +/- 1SD of the mean value of 15 centres from North America and Europe participating in this program.

Animals↗
PubMed1986

Serum thyroglobulin (Tg) and thyroglobulin antibodies (TgAb) in thyroid cancer.

Serum thyroglobulin antibodies (TgAb) and serum thyroglobulin (Tg) levels were measured in 28 normal controls and 32 patients with differentiated thyroid cancer. The TgAb and Tg levels were measured in the patients when they were on replacement thyroxine therapy prior to the whole body radioiodine I-131 scan (WBS), using immunoradiometric assay kits. The TgAb level in normal controls was from 0-4.8 micrograms/ml, with a mean of 0.6 microgram/ml, while the Tg level in these controls was from 0.0-48.0 ng/ml, with a mean of 4.2 ng/ml. In the patients with thyroid cancer, the TgAb levels were normal except for a few patients who had residual thyroid or tumour in the neck and had raised levels of TgAb. Their Tg levels were normal except for 7 patients who had elevated values. 2 of these 7 had no evidence of disease on X-ray, bone scan, or WBS (I-131) while the other 5 had evidence of metastases. However, 4 patients had metastatic disease with normal Tg levels, and 2 of these patients had residual thyroid in the neck and raised TgAb levels, while in the remaining 2 patients, both Tg and TgAb were low. Serum Tg is a useful tumour marker for recurrent or metastatic thyroid cancer, but the presence of residual normal thyroid would interfere with the results.

Adenocarcinoma↗
PubMed1985

Correlation of steroid receptors with histologic differentiation in mammary carcinoma. A Singapore experience.

Cancer of the breast is the most common tumor in females in Singapore, with the rate of 20.7 per 100,000 per year (1977 estimate), which is predicted to increase to 29.8 per 100,000 women per year by 1995. A detailed histopathologic review of 50 primary breast cancer tumors analyzed for estrogen receptor (ER) level was carried out and a variety of morphologic features correlated with ER results to identify any factors that will improve the management and prognosis for breast cancer. Cytosol was incubated with 3H-estradiol in the presence and absence of cold diethylstilbestrol, and bound and free hormone were separated by Dextran-coated charcoal method. Tumors binding more than 5 fmol/mg cytosol protein were classified as ER-positive. Progesterone receptor (PR) level was analyzed in some specimens with the use of a similar method. Most of the patients were Chinese (90%). Three patients were Malays, one was Indian, and one was European in this series. Results indicated that there was strong correlation between ER level, age, and histologic grade of the tumors. No correlation existed between absence or presence of lymph node metastases and ER. Although there was a trend for ER-positive tumors to have a low-grade lymphocytic infiltration, the difference was not statistically significant.

Adult↗
PubMed1985

Glucose tolerance test and insulin levels in children with transfusion-dependent thalassaemia.

Blood glucose and serum immunoreactive insulin levels were measured following an oral glucose load in 20 unrelated children with multiple transfused thalassaemia. Results suggest that even though overt diabetes and glucose intolerance are uncommon before the age of 13 years, the presence of insulin resistance is evident, especially in those who have been splenectomized.

Adolescent↗