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Biomedical subjects

T C Aw

Publications and source records attributed to T C Aw.

At least 91 records · Page 5Linked to original sources
PubMed1989

The Bio-Rad Diamat Analyser: an automated liquid chromatography system for haemoglobin A 1c (HbA 1c) determination.

The measurement of glycosylated haemoglobin is a relatively new clinical tool, the assays for their determination having become increasingly available since their introduction in the late seventies. The clinical usefulness of these assays in the long-term monitoring of diabetics, especially the pregnant diabetics, appears to be generally accepted. There remains, however, considerable confusion amongst clinicians as to their reliability and interpretation. This is largely engendered by the diversity of the diagnostic methods in current usage, many of which are not specific for the HbA1c moiety, which is the subfraction comprising haemoglobin molecules with attached glucose molecules at the amino terminal valine sites, and which has been shown to be increased in the blood of diabetic patients. This paper describes an evaluation of one of the most specific methods currently available, using state-of-the-art technology. In addition to specificity, the method appears attractive in being precise, automatable (and thus operator-independent), and rapid.

Adult↗
PubMed1988

Altered fibrinolysis in DVT: influence of site of sampling.

Alteration of the fibrinolytic system is considered to be important in the development of deep venous thrombosis (DVT). Using specific assays for tissue plasminogen activator (t-PA) activity, t-PA inhibitor (PAI) and t-PA antigen, we measured these activities in 16 women who developed DVT during their pregnancies. A group of 24 healthy females of comparable age was studied as controls. PAI was increased in 87% of these patients compared to the healthy controls. In some of these patients a defect in release of t-PA from vascular endothelium was found as well. The site at which blood was sampled for analysis appeared to be an important criterion in the ex vivo assessment of functional t-PA reserve and PAI levels, though relatively less so for the latter measurement. The unaffected lower limbs, relative to the unaffected upper limbs, showed an increase in PAI and a demonstrable decrease in t-PA release, both representing increased risk factors for rethrombosis. The affected lower limbs showed similar but more accentuated changes in these parameters.

Adult↗
PubMed1988

Vitamin D uptake and metabolism by perfused rat liver: influences of carrier proteins.

Several blood proteins have been associated with the transport of vitamin D sterols. Vitamin D is synthesized in the skin or absorbed from the intestine, and there is evidence for different rates of transfer to the liver from these sources. To evaluate the influences of various plasma proteins on the hepatic accumulation of vitamin D3, human plasma albumin, D-binding protein, chylomicrons, chylomicron remnants, low density lipoprotein (LDL) and high density lipoprotein were isolated and incubated with [3H]vitamin D3 before single-pass perfusions of the isolated, vitamin D-deficient rat liver. Hepatic uptake of sterol was greatest when vitamin D3 was presented on LDL or chylomicron remnants, whereas D-binding protein permitted the least uptake. Silicic acid chromatography revealed greater amounts of 25-hydroxyvitamin D3 when substrate was presented on carriers known to have hepatic receptors. After iv administration of tracer amounts of vitamin D3 to fasting rats, gradient gel electrophoretic analyses of plasma revealed most of the [3H] associated with the vitamin D-binding protein, and smaller amounts associated with LDL and high density lipoprotein. Our results suggest a major role for chylomicron remnants in the hepatic presentation of ingested vitamin D3 and support the possibility that hepatic delivery from cutaneous sites may involve lipoprotein carriers.

Animals↗
PubMed1987

Occupational asthma from inhaled egg protein.

We evaluated workers and performed an industrial hygiene assessment at a plant where raw eggs are processed into powdered egg yolk and whole egg. Egg dust levels in the packaging room straddled the American Conference of Governmental Industrial Hygienists' (ACGIH) exposure guideline of 10 mg/m3 for nuisance dust. We obtained medical histories from 25 workers, and performed physical examinations, spirometry, and serial determinations of peak expiratory flow rate (PEFR) by portable meter every 3 hrs (while awake) for 7 days. We defined symptomatic bronchial lability to be a decrement in PEFR on any one day of 20% or more of the day's maximum, with concurrent symptoms. Skin-prick tests and serum assays for specific IgE by the radioallergosorbent (RAST) method were performed to assess sensitivity to commercial egg proteins, egg protein fractions, and freshly prepared extracts of whole egg powder and yolk. We classified participants as definite cases of asthma if both the examining physician diagnosed asthma and symptomatic bronchial lability was demonstrated by serial PEFR determinations. Definite noncases of asthma were those participants in whom the physician did not diagnose asthma and in whom symptomatic bronchial lability was not demonstrated by PEFR. All five definite cases, compared to three of 16 definite noncases of asthma, had one or more positive skin-prick tests to egg proteins. Four of five cases, compared to 0 of 14 noncases, who had serum determinations, had an elevated RAST to one or more of the egg proteins. This study demonstrates that occupational asthma associated with IgE-mediated allergy to egg proteins occurs among workers exposed to inhaled egg proteins.

Air Pollutants, Occupational↗
PubMed1987

Clinical and immunologic studies among egg-processing workers with occupational asthma.

Twenty-five workers in an egg-processing factory were evaluated for respiratory sensitization to inhaled egg proteins by a physician evaluation, serial peak expiratory flow rate (PEFR) measurements for a 1-week period, and immunologic tests. Immunologic studies included skin prick tests, serum-specific IgE (RAST), and specific IgG (ELISA) to solutions prepared from commercial food allergens: factory-powdered egg white and yolk products and purified egg white fractions, including ovalbumin, ovomucoid, lysozyme, and conalbumin. Six workers had significant daily PEFR lability (greater than 20%) of whom five had associated cutaneous reactivity to at least one egg allergen. A diagnosis of "definite asthma" was established in five workers suspected by the physician of having asthma. These five workers exhibited significant decrements in daily PEFR that were accompanied by bronchial symptoms. Occupational asthma was diagnosed by the physician in four of the five latter workers. Definite asthma was significantly associated with both cutaneous reactivity to egg allergens (p less than 0.01) and RAST binding (p less than 0.01). Of eight workers with cutaneous reactivity to at least one egg reagent, four workers (50%) were positive to only purified egg white fractions. The highest levels of RAST binding were detected in four workers, and the best binding activity was to ovomucoid and ovalbumin fractions. Elevated specific IgG responses were significantly higher in egg-factory workers to whole egg (p less than 0.005), lysozyme (p less than 0.002), and conalbumin (p less than 0.002) allergens compared to responses of nonexposed control subjects. However, no differences in specific IgG were detected between symptomatic and asymptomatic workers.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Pseudohyponatremia.

Pseudohyponatremia should be distinguished from true hyponatremia lest injudicious therapy be instituted. Pseudohyponatremia is caused by a displacement of serum water by elevated concentrations of serum lipids or proteins. Only two (flame photometry and indirect potentiometry) of the three current methods available for measuring serum sodium involve sample dilution and may consequently produce spuriously low sodium values. The third method (direct potentiometry) involves no sample dilution, and sodium measurements are unaffected by hyperlipidemia and hyperproteinemia. As all three methods for sodium measurements may coexist in a clinical laboratory, it is important for the physician to be aware not only of the serum value but also the method employed.

Blood Proteins↗
PubMed1985

Comparison of the performance of serum and urine hCG immunoassays in the evaluation of gynecologic patients.

We conducted a study to compare the performance of serum and urine pregnancy tests in the evaluation of gynecologic patients presenting to our ED. The overall efficiency of the two tests was very similar: 99.5% for the serum test, and 97.6% for the urine test. In patients proven to have ectopic pregnancies, however, the serum test was positive in 100%; the urine test was positive in only 60%. The serum test misclassified (gave false-negative or false-positive results) in three of 607 patients (0.5%). The urine test misclassified 14 of 607 patients (2.3%). Moreover there were 18 inconclusive or invalid urine test results. Thus the urine test provided misinformation or no information in 32 of 607, or 5.3%, of the total study population.

Chorionic Gonadotropin↗
PubMed1983

Normal rabbit intestinal cytosol as a source of binding protein for the 1,25-dihydroxyvitamin D3 assay.

Cytosol prepared from small intestine of vitamin D-sufficient rabbits contains a specific high-affinity binding protein for 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). This binding protein sediments at 3.0-3.5 S in sucrose density gradients containing 0.3 M KCl. Scatchard analysis using intestinal cytosol demonstrated a Kd of 0.05 nM and a maximum binding capacity of 92 fmol/mg cytosol protein for 1,25(OH)2D3 at 4 degrees C. Competitive binding studies with various metabolites of vitamin D showed a relative binding affinity of this protein for 1,25(OH)2D3 greater than 25-hydroxyvitamin D3 greater than vitamin D3. With 200 micrograms of rabbit intestinal cytosol protein, as little as 1.0-2.5 pg of 1,25(OH)2D3 reproducibly displaced the tracer sterol from the binding protein. Analyses of human plasma 1,25(OH)2D3 content yielded values consistent with published results. The vitamin D-replete rabbit provides a convenient, plentiful, and inexpensive source of binding protein for 1,25(OH)2D3 assays.

Animals↗
PubMed1982

Thyrotoxicosis and thyroid cancer.

It is generally held that thyroid cancer is uncommonly associated with thyrotoxicosis. We report here nine patients with thyroid cancer amongst 720 patients with thyrotoxicosis. Three patients presented with features of malignancy together with thyrotoxicosis (Group A), one of whom had triiodothyronine (T3)-toxicosis. The remaining six patients were diagnosed following histological examination of tissues removed during subtotal thyroidectomies for hyperthyroidism (Group B). Two patients in Group A had follicular carcinoma; the rest were papillary in type. All the patients were rendered euthyroid initially, followed by ablative therapy for two patients in Group A and four patients in Group B. All but one are alive after one to nine years (mean of 3 . 4 years). The diagnosis of thyroid carcinoma is infrequently considered in the presence of thyrotoxicosis. The association is not clinically apparent in the majority of patients. The optimum management of such occult malignancies in thyrotoxicosis remains to be defined.

Adenocarcinoma↗