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Biomedical subjects

T C Chen

Publications and source records attributed to T C Chen.

At least 217 records · Page 12Linked to original sources
PubMed1988

A space-resolved fluorometer and its application to immunoassay.

A metal surface has been added into a fluorometer to reflect the excited light and to reduce the light scattering. Due to the total separation of the fluorescent signal and the noise by directing them into different spaces, the resolution could be improved by several orders of magnitude. The same metal surface could also be used for immunoassays. The detection of alpha-fetoprotein in normal rat serum and human standard serum are given as examples. The results indicate that the apparatus and the method have significant advantages.

Antibodies, Anti-Idiotypic↗
PubMed1988

Inhibitory effects of volume expansion performed in vivo on transport in the isolated rabbit proximal tubule perfused in vitro.

To examine the renal tubular sites and mechanisms involved in the effects of hypooncotic volume expansion (VE) on renal electrolyte excretion, we performed clearance and isolated tubular perfusion studies using intact and thyroparathyroidectomized (TPTX) rabbits. We also examined the effect of VE on luminal brush border transport. In the microperfusion studies, proximal convoluted (PCT) and straight (PST) tubules were taken from rabbits without prior VE or after 30 min of 6% (body wt) VE. Acute VE increased the percentage excretion of Na, Ca, and P in TPTX animals and the percentage and absolute excretions of these ions in intact rabbits. In PST from VE animals, fluid flux (Jv) was depressed compared with Jv in PST from nonVE rabbits: Jv = 0.18 +/- 0.03, (VE) vs. 0.31 +/- 0.03 nl/mm.min, (nonVE) P less than 0.02. Phosphate transport (Jp) in the PST from VE animals was also depressed: JP = 1.58 +/- 0.10 (VE) vs. 2.62 +/- 0.47 pmol/mm.min, (nonVE) P less than 0.05. Similar results were obtained with TPTX animals. In the PCT from VE animals, Jv was decreased (0.49 +/- 0.10 (VE) vs. 0.97 +/- 0.14 nl/mm.min, (nonVE) P less than 0.02), but JP was not affected significantly. Transport inhibition was stable over approximately 90 min of perfusion. In the brush border vesicle studies, sodium-dependent phosphate transport was inhibited compared with that in control animals, at the 9-, 30-, and 60-s time points. These findings indicate that the inhibition of renal ionic transport by VE occurs in both PCT and PST and is, in part, the result of a direct effect of VE on tubular transport mechanisms.

Animals↗
PubMed1988

Hyperparathyroidism and 1,25-dihydroxyvitamin D deficiency in mild, moderate, and severe renal failure.

It has been postulated that hyperparathyroidism in chronic renal failure results from hypocalcemia, occurring, in part, from phosphate retention and/or deficient 1,25-dihydroxyvitamin D3 [1,25-(OH)2D3] synthesis. However, many studies have failed to demonstrate hyperphosphatemia or low 1,25-(OH)2D levels in patients with mild renal failure. We measured creatinine clearance (CCr), fractional excretion of phosphorus (FEP), and serum phosphorus, ionized calcium, and plasma N-terminal PTH, and 1,25-(OH)2D concentrations in 21 normal subjects and 51 patients with renal failure. Patients with mild renal failure (Ccr, greater than 40 mL/min.1.73 m2) had normal mean serum phosphorus and ionized calcium and decreased mean 1,25-(OH)2D levels compared with those in normal subjects. In patients with moderate renal failure (CCr, 20-40), the mean ionized calcium level was normal, plasma PTH levels and FEP were elevated, and the decrement in 1,25-(OH)2D was more pronounced. The mean ionized calcium level was decreased only in the group of patients with severe renal failure (CCr, less than 20). The 1,25-(OH)2D values correlated positively with CCr and negatively with the log of plasma PTH and serum phosphorus concentrations. Log of plasma PTH correlated negatively with CCr and positively with FEP. The ionized calcium concentration correlated very weakly with CCr and the log of the plasma PTH level. These data demonstrate the presence of hyperparathyroidism, normocalcemia, and 1,25-(OH)2D deficiency in renal failure and are consistent with a role for 1,25-(OH)2D in the suppression of parathyroid activity through as yet unidentified mechanisms.

Adult↗
PubMed1987

Volume expansion-induced changes in renal tubular membrane protein phosphorylation.

The influence of volume expansion (VE) on the in vitro phosphorylation of membrane protein in the proximal brush border membrane (BBM) of the thyroparathyroidectomized (TPTX) rat was studied in the presence and absence of cyclic AMP and the results were compared to those obtained in control TPTX and intact animals. The results indicate that the cyclic AMP-independent phosphorylation of a protein band (Mr = 72,000) was stimulated both by VE and by the presence of parathyroid hormone in the circulation, whereas the cyclic AMP-dependent phosphorylation of membrane proteins (Mr = 40,000, 52,000 and 87,000) was inhibited by the same maneuvers. These findings, taken together with data previously available, which demonstrate inhibition of BBM phosphate transport following VE, may provide a link between alterations in phosphate transport in renal BBM vesicles and the phosphorylation of membrane proteins. The results further suggest that membrane protein phosphorylation may be a common mechanism by which a number of agents and maneuvers induce an inhibition of renal tubular phosphate transport.

Animals↗
PubMed1987

Migraine and other diseases in women of reproductive age. The influence of smoking on observed associations.

From among the pregnant women in the Collaborative Perinatal Project of the National Institute of Neurological and Communicative Disorders and Stroke, we identified 508 who had migraine, and 3192 who had no history of migraine, of taking headache medication during the previous 12 months, and of headaches during the pregnancy. Migraineurs smoked more heavily and had a longer smoking history than their headache-free peers. Among migraineurs, smokers were not more likely to consume analgesics than nonsmokers. Regardless of smoking classification, more migraineurs consumed tranquilizers, amphetamines, and sleeping pills than headache-free women. Among smokers only, migraine was associated with heart disease, thrombosis/phlebitis, asthma, peptic ulcer, and pneumonia. In nonsmokers, migraine was associated with drug sensitivity and other allergies.

Adolescent↗
PubMed1987

Anti-HBc IgM in cases of hepatocellular carcinoma and cirrhosis in Taiwan.

The sera of apparently healthy carriers of hepatitis B virus surface antigen enrolled in the Taiwan Prospective Study were tested retrospectively for anti-HBc IgM, to determine whether this test would be useful in predicting the development of hepatocellular carcinoma (HCC) and/or cirrhosis. In comparison with men who did not develop HCC or cirrhosis, the relative risk of those with anti-HBc IgM elevations was 3.4 and 5.6, respectively. Each of these factors was highly statistically significant, although the difference between them was not. Demonstration of anti-HBc IgM titers of greater than 1:1000 in serum probably reflects ongoing low level viral replication but not recent infection. Anti-HBc IgM appears to be a useful prognostic indicator for the future development of HCC and/or cirrhosis.

Adult↗
PubMed1986

Quantification and immunolocalization of apolipoprotein E in experimental atherosclerosis.

We developed a radioimmunoassay for rabbit apolipoprotein E (apo E) for studying their plasma apo E levels and its accumulation in the aorta of rabbits fed a cholesterol diet. Delipidation of plasma did not increase the apo E immunoreactivity and this immunoreactivity was indistinguishable from that in an apo E-phospholipid complex. The antigenic determinants of apo E in lipoprotein particles were therefore fully reacted with our goat anti-apo E antibodies. In our assay system, the non-ionic detergent Tween-20 was found to be necessary to significantly reduce the non-specific binding of 125I-labeled apo E to polystyrene tubes, and yet not interfere with the assay. In rabbits (n = 6) fed a high cholesterol (1%) diet, plasma apo E increased at least 10-fold above baseline levels and reached maximal levels within 17-20 days after the onset of cho-diet feeding. These levels were sharply reduced only 10 days after resuming a normal diet. Plasma total cholesterol levels went through a similar pattern. Thus, the plasma cholesterol concentration can simply be used to monitor the increase of apo E in cholesterol-fed rabbits. All the cholesterol-fed rabbits developed atherosclerotic fatty streak lesions and apo E located mostly in the thoracic region and was significantly correlated with the accumulation of lipids in the areas of lesion. In addition, the apo E deposition was limited to the aortic areas where lipids were present. On the other hand, apo A-I was not detectable in any lesion area. Our data suggest that apo E or apo E-containing lipoproteins, may be involved in the development of atherosclerosis in cholesterol-fed rabbits.

Animals↗
PubMed1985

Genetic markers of an aboriginal Taiwanese population.

A group of Taiwan aborigines, the Toroko, was typed for 21 classical genetic loci. This is part of an ongoing program aimed at a comprehensive study of Taiwan aborigines. In this first paper a short summary of historical, archeological, and anthropological data in the literature is made, and results of the present survey are compared with older results from other aborigine tribes. An analysis of other neighboring populations from southeast Asia has also been carried out in order to give a preliminary answer to the question of origin of Taiwanese aborigines. Fifteen populations were studied for 13 loci by tree analysis, principal components, and isolation by distance. Tree analysis and principal component analysis gave results in fairly good agreement and indicate three major population clusters: a northeast cluster (Ainu, Korea, Japan, and Ryukyu); a southeast cluster (south China, Thailand, Vietnam, Philippines, Taiwan, and Toroko); and a third cluster including Malaya and Borneo. The positions of Polynesia, Micronesia, and Melanesia are somewhat peripheral. Analysis of the tree shows some potential cases of convergence, perhaps owing to admixture, and of divergence. The analysis of isolation by distance shows that geographic propinquity is a reasonably good predictor of general similarity in this area.

Humans↗
PubMed1985

Occupational radiation exposures in Taiwan, 1962-1983.

This paper presents an updated compilation of occupational radiation exposures in Taiwan, Republic of China, for the years 1962-1983. The highest collective dose equivalent occurred in 1981 and was estimated to be 535.318 man-rem, and the average measurable dose equivalent per worker is about 0.25 rem in the same year. All data analyzed were plotted on log-probability paper. A brief prospectus on the health implications of the annual occupational dose equivalents is also provided, using the year 1981 as an example.

Environmental Exposure↗
PubMed1985

The outcome of pregnancy after chemotherapy for gestational trophoblastic disease.

Thirteen pregnancies in 11 women previously treated with cytotoxic chemotherapy for GTD were studied. There were 11 live full-term babies (84.6%), 2 blighted ova (15.4%), 1 placenta accreta (7.7%) and 1 fetal anomaly (7.7%). Unlike other series, 69% of the pregnancies occurred within 1 year after the termination of chemotherapy. The rate of successful pregnancy was not different from that reported by others. Prenatal elimination of abnormal embryos after conception rather than wastage of damaged oocyte before conception might explain this observed low incidence of abnormal birth in GTD patients treated with cytotoxic chemotherapy.

Abortion, Spontaneous↗
PubMed1984

Modulation of 1,25-dihydroxyvitamin D3 receptor by phospholipids and fatty acids.

The structural relationship between several lipids and their respective capacities to inhibit the specific binding of [3H]-1,25 (OH)2 vitamin D3 to chick intestinal cytosol preparations was investigated. The lipids investigated were: synthetic 3-sn-phosphatidylcholine and 3-sn-phosphatidic acid, egg yolk 3-sn-phosphatidylcholine and its corresponding phosphatidic acid, and free unsaturated fatty acids and their esters. The results indicate that at least three structural elements in the phospholipid molecule appear to be important; these are: 1) the structure of the fatty acid, 2) the anionic properties of the phospholipid phosphate group, and 3) the glycerol phosphate portion of the molecule. Our data also demonstrate that the position (1 or 2) and the amount (single vs. double) of unsaturated fatty acids in the phospholipid molecule do not play a major role in the receptor-1,25 (OH)2 vitamin D3 interaction. Furthermore, under equilibrium conditions, kinetic and Scatchard analysis suggest that phospholipids or free fatty acids may bind at a site different from the 1,25 (OH)2 vitamin D3 binding site, and therefore inhibit the hormone binding via a noncompetitive conformational change in the receptor molecule. A model for this phospholipid/free fatty acid binding site is proposed.

Animals↗
PubMed1984

Prostaglandin E2 and parathyroid hormone: comparisons of their actions on the rabbit proximal tubule.

Recent studies demonstrated that prostaglandin E2 (PGE2) participates in the regulation of glomerular and distal tubular function. A functional role for PGE2 on the proximal tubule has only recently been explored. Thus, we reported that PGE2 antagonizes the phosphaturic effect of PTH in the dog, which suggests that PGE2 may influence the transport functions of the mammalian proximal tubule. The present studies were designed to examine the direct effect of parathyroid hormone (PTH) and PGE2 on the fluxes of fluid (Jv) and phosphate (Jl-b PO4) in the rabbit proximal convoluted and straight tubules (PCT and PST). The activation of adenylate cyclase by the two agents was also examined. Finally, the combined effects of PTH and PGE2 on Jv and Jl-b PO4 were also studied in the PST. In the PCT, PTH (1 microgram/ml) inhibited Jv by 31% (P less than 0.05) but did not alter Jl-b PO4. PGE2 (10(-5) M) failed to act on either Jv or Jl-b PO4. In this segment, PTH stimulated adenylate cyclase but PGE2 did not. In the PST, PTH (1 microgram/ml) inhibited Jv and Jl-b PO4 by 34 and 20%, respectively (P less than 0.01). PGE2 (10(-5) M) also inhibited Jv and Jl-b PO4, by 33 and 12%, respectively (P less than 0.02). In contrast, PGF2 alpha, a related prostanoid, failed to influence these transport parameters. In the PST, PTH activated adenylate cyclase but PGE2 failed to do so. When both PTH (1 microgram/ml) and PGE2 (10(-7) M) were present simultaneously, Jv and Jl-b PO4 were comparable to that seen during control collections.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed1984

Microsurgical reconstruction of the amputated hand.

Fourteen successful results in 16 cases of microsurgical reconstruction of uni- and bilateral hand amputations are reported. Metacarpal reconstruction included the use of titanium alloy for artificial metacarpi, autogenous metatarsals, and autogenous iliac bone grafts. Uni- and bilateral single and multiple donor toes were used in various combinations. Basic hand function and functional sensibility were restored in 14 of 16 cases. There was minimal donor site functional impairment.

Amputation, Traumatic↗