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Biomedical subjects

S C Chou

Publications and source records attributed to S C Chou.

At least 37 records · Page 2Linked to original sources
PubMed1995

Aging in rats is associated with an increase in adrenal apolipoprotein E.

Extrahepatic tissues including the adrenal cortex are capable of synthesizing apolipoprotein E (apoE). Locally synthesized apoE is believed to affect cellular uptake, transport and redistribution of cholesterol within that organ. We and another laboratory have previously reported that the adrenal cortex of aged rats has an elevated cholesteryl ester content. The aim of this work was to investigate whether this elevation is accompanied by increased adrenal apoE levels in aged rats. A Western blotting technique with polyclonal goat anti-human-apoE antiserum was employed as a probe for studies. The results showed that: (a) anti-human-apoE antiserum not only detected apoE in human plasma and adrenal homogenate, but also cross-reacted with a protein (or proteins) resembling apoE in rat plasma and adrenal homogenate (or supernatant) with a molecular weight of 34,000-36,000; (b) rat adrenal apoE concentration (per unit weight of protein) increased with age; (c) the increase did not result from blood trapped in the gland, because after organ perfusion the adrenal of aged rats persistently exhibited 58% more apoE than that of young animals. In conclusion, rat adrenal apoE concentration appears to increase with age. Whether this increase mechanistically causes the accumulation of cholesteryl esters in the aged rat adrenal remains to be investigated.

Adrenal Cortex↗
PubMed1995

Developmental regulation of the catalytic subunit of the apolipoprotein B mRNA editing enzyme (APOBEC-1) in human small intestine.

Apolipoprotein (apo) B mRNA editing is a site-specific cytidine deamination reaction responsible for the production of apoB-48 in mammalian small intestine. This process is mediated by an enzyme complex that includes the catalytic subunit, APOBEC-1. In the present study, it is shown that the developmental regulation of apoB mRNA editing in fetal human small intestine is closely mirrored by accumulation of APOBEC-1 mRNA. Similar results were obtained using Caco-2 cells, the data further suggesting that culture of these cells under conditions previously shown to promote differentiation produce an earlier and more marked induction of APOBEC-1 mRNA abundance. Complementary analysis of APOBEC-1 protein accumulation using immunocytochemical localization reveals its appearance to be temporally coordinated with the accumulation of APOBEC-1 mRNA and its distribution to be confined to villus-associated enterocytes. Previous studies demonstrated a close temporal association between the development of triglyceride synthesis and apoB mRNA editing in the rat liver and small intestine. Analysis of fatty acid CoA ligase, monoacylglycerol acyltransferase, and diacylglycerol acyltransferase activity in preparations of human liver and small intestine demonstrates activity of all three enzymes in the late first and early second trimester, suggesting that certain aspects of complex lipid biosynthesis in the human fetal small intestine and liver are regulated developmentally. The cues that modulate the post-transcriptional regulation of fetal human small intestinal apoB gene expression may thus include both temporal programming and events related to the emergence of lipid transport capability.

APOBEC-1 Deaminase↗
PubMed1995

Metabolism of fenbufen by cultured 3T3-L1 adipocytes: synthesis and metabolism of xenobiotic glycerolipids.

The storage of xenobiotic compounds as glycerolipids and their subsequent mobilization was studied using fenbufen and differentiated 3T3-L1 cells in culture. Fenbufen was taken up from the incubation medium and incorporated into triacylglycerol, diacylglycerol, and phospholipids. The triacylglycerol was susceptible to digestion by pancreatic lipase. The xenobiotic phospholipid contained three species, one of which behaved as fenbufenoyl phosphatidylcholine as judged by TLC, HPLC, choline analysis, and mass spectroscopy. After incubation with radioactive fenbufen for 18 h, the cells were transferred to a chase medium where radioactivity was lost from the cells and appeared in the medium. The rate was three times higher when 10 microM isoproterenol was present; insulin had no effect. Non-esterified fenbufen and analogues of mono- and di-acylglycerol were secreted. Monofenbufenoylglycerol was characterized by its ability to be used as a substrate by purified monoacylglycerol acyltransferase. When oleic acid was used in place of fenbufen, the majority of the radioactivity released in a chase experiment was the non-esterified acid (over 90%) and neither mono- nor di-acylglycerol was detected. These data indicate that 3T3-L1 adipocytes can synthesize fenbufen-containing lipids and release them into the medium on hormonal stimulation. The secretion of mono- and di-acylglycerols may have unforeseen pharmacological or toxicological implications.

3T3 Cells↗
PubMed1993

Characterization of choline metabolism and secretion by human placental trophoblasts in culture.

Choline is an essential nutrient for fetal development and may be utilized to form phospholipids such as phosphatidylcholine and sphingomyelin; to synthesize the neurotransmitter, acetylcholine; and to donate methyl groups after being oxidized to betaine. Since the majority of choline required for fetal growth must be transported by the placenta from the maternal circulation, we examined the ability of isolated human trophoblasts to metabolize choline and to release choline and its metabolites into culture medium. Cytotrophoblasts were isolated from normal, full-term human placentas and incubated with [14C]choline for 3 h; the cells were washed to remove extracellular radiolabel, and the changes in intracellular and medium choline pools were followed for an additional 24 h. During the incubation, choline rapidly reached steady state intracellularly and label was incorporated into betaine, phosphocholine, cytidylyldiphosphocholine, phosphatidylcholine, glycerophosphocholine, lysophosphatidylcholine, and sphingomyelin. All labeled choline metabolites in cells, except glycerophosphocholine, decreased at 6 and 27 h of incubation (3 and 24 h, respectively, after labeled choline was removed), and labeled metabolites appeared in media. By 24 h after labeled choline was removed, the major labeled metabolites in the media were choline (82%), betaine (11%), and glycerophosphocholine (5%). Small amounts of phosphatidylcholine (1%), and lysophosphatidylcholine (1%) were found. Acetylcholine was a very minor choline metabolite in these cells. When placental cells were incubated for 66 h after isolation, they formed syncytiotrophoblasts, which incorporated labeled choline into metabolites in a similar pattern to cytotrophoblasts. These data indicate that isolated trophoblast cells can metabolize choline to form all of its major metabolites and that several metabolites are released to the medium in significant amounts. Thus, our data suggest that the major metabolite supplied to the fetus may be choline, but that betaine and glycerophosphocholine may also be vehicles for transfer of choline equivalents from mother to fetus.

Betaine↗
PubMed1993

Seasonal changes in critical enzymes of lipogenesis and triacylglycerol synthesis in the marmot (Marmota flaviventris).

Fatty acid metabolism and triacylglycerol synthesis are critical processes for the survival of hibernating mammals that undergo a prolonged fasting period. Fatty acid synthase, fatty-acid-CoA ligase, diacylglycerol acyltransferase, and monoacylglycerol acyltransferase activities were measured in liver and in white and brown adipose tissue, in order to determine whether enzymes of lipogenesis and triacylglycerol synthesis vary seasonally during hibernation in the yellow-bellied marmot (Marmota flaviventris). Compared with mid-winter hibernation, fatty acid synthase activity was higher in all three tissues during early spring when marmots emerged from hibernation and in mid-summer when they were feeding, consistent with the synthesis of fatty acids from the carbohydrate-rich summer diet. Fatty-acid-CoA ligase and diacylglycerol acyltransferase activities were highest in summer in white adipose tissue when triacylglycerol synthesis would be expected to be high; diacylglycerol acyltransferase activity was also high in brown adipose tissue during spring and summer. In liver, however, diacylglycerol acyltransferase specific activity was highest during hibernation, suggesting that triacylglycerol synthesis may be prominent in liver in winter. Monoacylglycerol acyltransferase activity, which may aid in the retention of essential fatty-acids, was 80-fold higher in liver than in white or brown adipose tissue, but did not vary seasonally. Its dependence on palmitoyl-CoA suggests that a divalent cation might play a role in enzyme activation. The high hepatic diacylglycerol acyltransferase activity during hibernation suggests that the metabolism of very low density lipoprotein may be important in the movement of adipose fatty acids to brown adipose tissue and muscle during the rewarming that occurs periodically during hibernation.(ABSTRACT TRUNCATED AT 250 WORDS)

Acyltransferases↗
PubMed1991

Antileukemic activity of Viva-Natural, a dietary seaweed extract, on Rauscher murine leukemia in comparison with anti-HIV agents, azidothymidine, dextran sulfate and pentosan polysulfate.

An antileukemic activity of partially purified polysaccharide of an edible seaweed. Viva-Natural, against Rauscher murine retrovirus-induced erythroleukemia has been demonstrated. This antileukemic effect is compared with standard anti-human immunodeficiency virus (HIV) agents, azidothymidine (AZT), dextran sulfate and pentosan polysulfate. Pretreatment with Viva-Natural, as an immunomodulator, on day 3 prior to the virus inoculation demonstrated definite prophylactic activity, while pretreatment with the other three anti-HIV agents showed no prophylactic activity. The replication of Rauscher virus in BALB/3T3 cell cultures accompanied by direct cytopathic effect (syncytia formation) was suppressed in the presence of Viva-Natural or the other anti-HIV agents in the culture medium. In spite of the antiviral potentials of the four agents in vitro, only Viva-Natural and AZT demonstrated therapeutic efficacy against Rauscher leukemia in mice.

Animals↗
PubMed1990

Tropic effect of dexamethasone on goldfish melanocytoma cells: induction of calcium-dependent but protein synthesis-independent morphological changes.

Treatment of melanocytoma cells of goldfish origin with dexamethasone leads to rapid morphological changes, flattening of cell body and extension of dendrites. This effect is independent of protein synthesis but requires the presence of extracellular calcium, indicating that it is a "tropic effect" distinct from the typical "trophic effects" of steroid hormones that involve de novo protein synthesis.

Animals↗
PubMed1989

Isolation of melanized cell lines with stable phenotypes from a goldfish erythrophoroma cell line and cryopreservation of these cells by the use of autologous serum.

Cell lines with stable melanized phenotypes were isolated from a goldfish erythrophoroma cell line. These cell lines include several interesting phenotypes: a) reversible dedifferentiation and redifferentiation in response to withdrawal and addition of fish serum; b) irreversible dedifferentiation in response to withdrawal of fish serum; c) independence on fish serum for melanization; d) dependence on fish serum for growth; and e) pigment aggregation in response to epinephrine. We also report that cryopreservation of all the melanized cell lines, but not any of the unmelanized cell lines, requires the presence of fish serum. This raises the possibility that there may be advantages to use autologous serum for the cryopreservation of sensitive cell lines.

Animals↗
PubMed1989

Reversible dedifferentiation and redifferentiation of a melanized cell line from a goldfish tumor.

We reported previously the isolation of a melanized cell line that can undergo reversible dedifferentiation and redifferentiation. A heavily pigmented cell line, designated as P15, originally isolated by fish serum-induced melanization of some GEM 81 cells, cloned and serially passaged in fish serum medium, became noticeably less pigmented after several months in fetal calf serum medium and completely unpigmented after another year in the same medium. Addition of fish serum to the medium of this dedifferentiated cell line, designated P15D, induced pigmentation within a week. This re-induced pigmented cell line, designated as P15DI, became unpigmented when cultured in fetal calf serum medium for one month. We report here that the dedifferentiation of P15 occurs in two stages. One week after withdrawal of fish serum, the specific activity of tyrosinase of the culture dropped by approximately 70% and remained at this reduced level for at least one month. After one year, the specific activity of tyrosinase had dropped to a barely detectable level and the culture became completely unpigmented (P15D). Electron microscopic studies showed that the P15D cells have no melanosomes, probably no large vesicles for melanosome formation, but some dopa-positive trans-Golgi network (TGN). Addition of fish serum to the growth medium of P15 cultures led to a steady increase in the specific activity of tyrosinase, detectable after one day. There was also an increase in the amount of dopa-positive TGN within one day. Melanosomes first appeared after three days and became numerous after one week. Upon removal of fish serum, these re-induced cells (P15D1) underwent a rapid decrease in the specific activity of tyrosinase, reaching, after eight days, the basal level seen in P15D cells. We also report that a protein designated as p75 (Mr approximately 75,000), previously shown to be associated with melanosomes in two melanized cell types of goldfish origin, is present in all melanized cell lines, including P15 and P15DI but absent in unmelanized cell lines, including P15D.

Animals↗
PubMed1984

Effects of adriamycin on the macromolecular synthesis in rat myocardiocytes and KB cells.

Effects of adriamycin on cardiomyocytes and KB cells have been examined. Adriamycin inhibited DNA and RNA synthesis in both rat myocardial cells and KB cells. Protein synthesis was also inhibited but at a much higher dosage. In myocardiocytes, protein synthesis was dose-dependent with inhibition being almost complete at 100 microM. In contrast, inhibition of protein synthesis in KB cells leveled off at 50%.

Animals↗
PubMed1984

The effects of aspirin and acetaminophen on tetrahymena pyriformis GL growth and macromolecular synthesis.

The effect of aspirin and acetaminophen on Tetrahymena pyriformis GL is examined in this study. The concentration of drug which inhibited T. pyriformis GL growth in 24 hours, indicated as IC50, was 200 micrograms/ml and 580 micrograms/ml for aspirin and acetaminophen, respectively. Macromolecular incorporation study showed that aspirin at 100 micrograms to 400 micrograms/ml had essentially no effect on all parameters examined. Acetaminophen had a significant (P less than 0.01) suppression of 14C-thymidine, 14C-uridine and 14C-acetate uptake, but no effect on 14C-amino acid uptake at concentrations from 400 micrograms to 1200 micrograms/ml. T. pyriformis GL is a useful eukaryocytic single cell organism for drug action study.

Acetaminophen↗
PubMed1984

Inhibition of acetate incorporation into lipids by adriamycin.

Adriamycin (ADM) inhibits 14C-acetate incorporation into cardiomyocytes, with the ID50 being 0.9 microM. Incorporation into neutral lipids were inhibited except for cholesterol ester. Cholesterol and phospholipids demonstrated the strongest inhibition at 5 microM ADM.

Acetates↗
PubMed1982

Presence of prostaglandins (PGs) in Tetrahymena pyriformis, GL and the effect of aspirin.

Tetrahymena pyriformis GL appears to require prostaglandins, either B, E or F series for growth, as demonstrated by the deleterious effect of aspirin. The latter inhibits prostaglandin synthetase (cyclooxygenase). Aspirin inhibited 50% growth of a 24 hr culture of T. pyriformis at a dose of approximately 200 micrograms/ml and completely inhibited at 600 micrograms/ml. Extraction with acid ethyl acetate: isopropanol solvent of 2.8 x 10(8) cells yielded 41.3 mg of lipid of which 62.8% and 34.5% were PGE2 and PGB, respectively. It is suggested that PGs are important for the growth of T. pyriformis and that the organism may be a useful source of natural PGs. Additionally, T. pyriformis may be useful in studies of the PGs pathway.

Animals↗
PubMed1981

Colorectal cancer and schistosomiasis.

The risk of colorectal cancer is known to be increased in patients with long-standing schistosomal colitis. A retrospective review of clinical data and surgical specimens from 60 patients with schistosomal granulomatous disease of the large intestine but without carcinoma demonstrated that 36 of them had mild to severe grades of colonic epithelial dysplasia. This was either focal or diffuse in distribution and occurred in flat mucosa, in pseudopolyps, or in regenerating epithelium at the edges of ulcers. These dysplastic changes are regarded as the pathological basis for the malignant potential of schistosomal colitis, and they resemble the changes found in long-standing chronic ulcerative colitis.

Adolescent↗
PubMed1979

Chromatographic fractionation and characterization of the active platelet aggregation inhibitory factor from bromelain.

Isolation and characterization of the platelet aggregation inhibitory factor of bromelain have been presented in this study. Commercial bromelain consists of 3 major components as demonstrated by discontinuous sodium chloride gradient chromatography through carbixymethyl-sephadex column. Fraction I constituted approximately 19% of the total fraction. This fraction had no proteolytic activity or platelet aggregation inhibiting activity, but showed peroxidatic activity. Fraction II and III, which constituted the remainder of the fraction eluted with 135 mM and 800 mM NaCl concentrations, respectively, showed both proteolytic and inhibition of platelet aggregation, but no peroxidatic activity. Immunoelectrophoresis and polyacrylamide electrophoresis showed fraction I with beta-mobility while fraction II and III demonstrated gamma-mobility. It is suggested that the proteolytic activity is associated with the inhibition of platelet aggregation, since oxidation of fractions II and III with sodium tetrathionate abolished both activities. The mechanism of inhibition of platelet aggregation by bromelain is presently unknown but may involve its influence on the prostaglandin synthetic pathway of platelets.

Bromelains↗