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Biomedical subjects

K S Cho

Publications and source records attributed to K S Cho.

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

Blood cadmium levels in the populations of Masan, Korea, and Miyagi, Japan: an inter-regional comparison.

Blood samples were collected from factory workers (with no occupational exposure to metals including cadmium) in Masan (167 subjects), Korea, in 1986, and Miyagi prefecture (270 subjects) Japan, in 1987. The samples were analyzed for cadmium in a single laboratory by flameless atomic absorption spectrophotometry under strict quality control. The effect of aging was detected in Masan and possibly also in Miyagi. The effect of smoking was evident among male smokers in Miyagi. Comparison with findings in a sister study on blood cadmium levels in China (taking the effects of smoking and aging into account) showed regional differences: the levels were lower in China, higher in Korea and probably highest in Japan. The smoking-associated increase in blood cadmium level per cigarette was 2-3 times higher in China than in Japan. The blood cadmium levels in the study regions appeared to be associated with the cadmium content of local rice as well as with local rice-eating habits.

Adult↗
PubMed1989

Hepatitis B virus infection among women in a shoe factory in Korea.

One hundred and sixty five Korean women in a shoe factory in Masan, Korea were evaluated on hepatitis B virus infection by solid-phase radioimmunoassay in 1986. The participants were women of child-bearing ages, mostly in 20's and 30's. About two thirds (105/165) of the subjects had serological evidence of past or present hepatitis B virus infection, and 17% (28/165) were HBsAg-positive. In view of possible risk of vertical transmission of hepatitis B virus, further epidemiological study was considered necessary to establish preventive measures.

Adolescent↗
PubMed1989

Profile of the Billings Ovulation Method acceptors and use-effectiveness of the method in Korea.

Data from a survey of 200 Billings Ovulation Method acceptors in Korea were used to describe a profile of these natural family planning acceptors, and to calculate use effectiveness rates for twelve months of use among women using the method for avoiding an unplanned pregnancy. The majority of acceptors were women of proven fertility who wanted to limit their family size, and many of them (79%) had previously used a family planning method. Fifty-six percent were Catholics, and those study subjects were above middle income group by Korean annual household income estimates. The mean number of living children the NFP acceptors had was 2.3 +/- 1.4 and the number of children they desired to have was 2.4 +/- 1.4. The cumulative life table rate for unplanned pregnancies at the end of 12 months of use was 7 (+/- 2.5 S.E.) per 100 women, and women ever attending the learning sessions as couples experienced relatively less unplanned pregnancies compared to those women attending the sessions alone.

Adult↗
PubMed1987

Purification and characterization of two immunologically distinct phosphoinositide-specific phospholipases C from bovine brain.

We previously reported (Ryu, S. H., Cho, K. S., Lee, K. Y., Suh, P. G., and Rhee, S. G. (1986) Biochem. Biophys. Res. Commun. 141, 137-144) that cytosolic fractions of bovine brain contain two phosphoinositide-specific phospholipase C (PLC), PLC-I and PLC-II. In this paper purification procedures and properties of these two forms of enzyme are presented. The two enzymes exhibit similar substrate specificity. Both PLC-I and PLC-II catalyze the hydrolysis of phosphatidylinositol (PI), phosphatidylinositol-4-phosphate (PIP), and phosphatidylinositol-4,5-bisphosphate (PIP2). Yet, they respond differently to activators such as Ca2+ and nucleotides and to inhibitory divalent metal ions such as Hg2+ and Cd2+. In addition, they are immunologically distinct as evidenced by the fact that monoclonal antibodies directed against either enzyme do not cross-react with the other. Their activities are Ca2+ concentration-dependent. PIP and PIP2 are better substrates than PI for both PLC-I and PLC-II when the concentration of Ca2+ is in the micromolar range. Study of the effect of nucleotides, such as GTP, guanosine 5'-(3-O-thio)triphosphate, guanyl-5'-yl imidodiphosphate, and ATP, on the activities of both isozymes with PIP2 as substrate revealed that (i) in the absence of Ca2+, PLC-I activity is enhanced by 400% by either GTP or ATP. In the presence of Ca2+ (a condition in which PLC-I exhibits much higher activity), the activation factor by nucleotides is diminished to approximately 140%. (ii) without Ca2+, PLC-II activity is too low to measure with or without added nucleotides. The effect of nucleotides on PLC-II activity is trivial in the presence of Ca2+. In addition, studies on the effect of metal ions on PI hydrolysis showed that the activities of both PLC-I and PLC-II are not affected by 50 microM of Mg2+, Mn2+, Ca2+, or Ni2+. However, Hg2+, Zn2+, and Cu2+ inhibited both PLC-I and PLC-II, with PLC-II exhibiting much higher sensitivity to these metal ions than PLC-I. For example, the value of I0.5 for Hg2+ inhibition is 0.2 microM for PLC-II and 1 microM for PLC-I. Cd2+ selectively inhibits PLC-II with a I0.5 value of 5 microM. Most of these metal ions' inhibition can be overcome by either dithiothreitol or EDTA.

Animals↗
PubMed1987

Bovine brain cytosol contains three immunologically distinct forms of inositolphospholipid-specific phospholipase C.

We previously reported that cytosolic fractions of bovine brain contain two immunologically distinct forms of phospholipase C (PLC), PLC-I and PLC-II. We now report the purification of another form of inositolphospholipid-specific phospholipase C from bovine brain cytosol, designated PLC-III, and the comparison of the catalytic properties of the three isozymes. Approximately 450 micrograms of pure PLC-III was obtained from 36 bovine brains, and it had a final specific activity of 30-40 mumol of phosphatidylinositol hydrolyzed per min per mg of enzyme in the presence of 0.1% deoxycholate. PLC-III exhibited an apparent Mr of 85,000 in NaDodSO4/PAGE, which is considerably smaller than the Mr of 150,000 for PLC-I and 145,000 for PLC-II. Neither of the two mixtures of monoclonal antibodies nor the rabbit polyclonal antibodies directed against either PLC-I or PLC-II cross-reacted with PLC-III. The catalytic properties of the three isozymes were studied by using small unilamellar vesicles prepared from either phosphatidylinositol (PtdIns) or phosphatidylinositol 4,5-bisphosphate (PtdInsP2) as substrates. Hydrolysis of both PtdIns and PtdInsP2 by the three enzymes was dependent on Ca2+. However, at low Ca2+ concentration, PtdInsP2 was the preferred substrate for all three enzymes. When PtdIns was the substrate, the three enzymes exhibited similar specific activities at their optimum pH, which was 4.8 for PLC-I, 5.0 for PLC-II, and 5.5 for PLC-III. But at neutral pH, the order of specific activity was PLC-III greater than PLC-II greater than PLC-I. In contrast, the order of specific activity was PLC-I greater than PLC-III greater than PLC-II for PtdInsP2 hydrolysis, which means that PLC-I is the most specific for PtdInsP2. The three enzymes were affected differently by bovine serum albumin: inhibition of PLC-I and activation of PLC-III were observed, whereas PLC-II was unaffected. This observation suggests that any putative protein effectors for PLC should be critically scrutinized.

Animals↗
PubMed1986

Two forms of phosphatidylinositol-specific phospholipase C from bovine brain.

Two immunologically distinct forms of phosphoinositide-specific phospholipase C were purified to near homogeneity from bovine brain. Their molecular weights determined by SDS-PAGE are 150,000 (enzyme I) and 145,000 (enzyme II), respectively. Under a nondenaturing condition, purified enzyme I exists mainly in dimeric form and as tetramer to a small extent, while enzyme II is predominantly in monomer, to a small extent as dimer and to a very small extent as trimer. Multiple forms of phosphoinositide-specific phospholipase C in brain tissue described in the literature might be, therefore attributed to the oligomerization of the two independent forms.

Animals↗