Biomedical subjects

M H Lee

Publications and source records attributed to M H Lee.

At least 91 records · Page 5Linked to original sources

PubMed2001

Dietary cholesterol absorption; more than just bile.

Absorption of dietary cholesterol from the intestine is an important part of cholesterol homeostasis and represents the first step that allows dietary cholesterol to exert its metabolic effects. Although the role of bile salts in the initial absorption of dietary cholesterol, by the formation of emulsions, is readily appreciated, the recognition that other molecular mechanisms might govern this process is only recently gaining momentum. Not only does the intestine regulate the amount of dietary cholesterol that enters the body; it is very selective with regard to the sterols that are allowed in. The human intestine is responsible for absorbing a significant amount of cholesterol each day. In addition to approximately 0.5 g d(-1) of dietary cholesterol, many other sterols are also present in almost equal abundance in the normal diet. Approximately 0.4 g of plant sterols, such as sitosterol, brassicasterol and avanesterol, are also present. However, the human body seems to allow only cholesterol to enter and remain in the body, with almost negligible amounts of plant sterols being retained. That specific molecular mechanisms are responsible for this behavior is supported by the identification of the genetic defect(s) in a rare disorder, beta-sitosterolemia (MIM 210250), where this process is disrupted. Such studies are now beginning to throw light on sterol absorption and excretion and elucidate the molecular mechanisms that govern these processes.

ATP Binding Cassette Transporter, Subfamily G, Mem↗

PubMed2001

Fertility outcome after tubal anastomosis by laparoscopy and laparotomy.

STUDY OBJECTIVE: To evaluate fertility outcome and benefit of laparoscopic tubal anastomosis compared with laparotomy. DESIGN: Retrospective study (Canadian Task Force classification II-2). SETTING: University hospital. PATIENTS: Eighty-one women requesting reversal of sterilization. Fertility outcome was analyzed in 76 patients for a minimum of 6 months. INTERVENTION: Laparoscopic tubal anastomosis in 37 women and abdominal tubal anastomosis in 44. MEASUREMENTS AND MAIN RESULTS: In both groups anastomosis was performed in two layers with four stitches using microsurgical technique. Overall pregnancy rates were 80.5% in the laparoscopy and 80.0% in the laparotomy group. The mean interval from operation to pregnancy was similar in the two groups (p = 0.9). Mean operating time was significantly longer for laparoscopy (201.9 +/- 33.8 min) than for laparotomy (148.7 +/- 32.5 min), including diagnostic laparoscopy. However, mean hospital stay was shorter for laparoscopy than for laparotomy (3.3 +/- 2.0 vs 6.1 +/- 0.6 days, p <0.05). CONCLUSION: Laparoscopic tubal anastomosis is less invasive and could be an alternative to laparotomy for reversal of tubal sterilization. Advanced laparoscopic equipment and much experience could enhance the pregnancy rate and reduce operating time.

Adult↗

PubMed2001

Differences in sensitization rates to outdoor aeroallergens, especially citrus red mite (Panonychus citri), between urban and rural children.

BACKGROUND: A recent investigation has suggested that citrus red mite (Panonychus citri, CRM) is the most important allergen in citrus-cultivating farmers with asthma and allergic rhinitis. OBJECTIVE: A cross-sectional survey was performed to evaluate the prevalence of asthma and chronic rhinitis symptoms and sensitization to common indoor and outdoor aeroallergens, including CRM and Japanese cedar pollen, in rural and urban Korean children. METHODS: A total of 2,055 children (1,055 subjects living in rural areas with citrus farms and 1,000 controls in urban areas without citrus farms) were enrolled. They were evaluated by a questionnaire, and by skin prick tests with 13 common indoor and outdoor aeroallergens, including CRM and Japanese cedar pollen. RESULTS: The prevalence of wheezing and chronic rhinitis symptoms during the last 12 months was 8.3% and 35.7% in the rural children and 10.5% and 22.4% in the control group. The most common sensitizing allergens in order of decreasing frequency were Dermatophagoides pteronyssinus (26.6%), Dermatoplagoides farinae (22.7%), CRM (14.2%), cockroach (11.3%), and Japanese cedar pollen (9.7%) among the rural children, but the sensitization rates to CRM and Japanese cedar pollen were 1.3% and 0.2% among the control children, respectively. The prevalence of wheeze during the last 12 months was not different between rural children with sensitization to CRM or Japanese cedar pollen and those without sensitization (5.4% vs 6.1%; 6.9% vs 5.9%). However, the prevalence of chronic rhinitis during the last 12 months was higher among those with sensitization to CRM or to Japanese cedar pollen than among those without sensitization (40.8% vs 34.4%; 51.5% vs 33.5%). CONCLUSIONS: CRM is a common sensitizing allergen in rural children, and the sensitization rates to outdoor aeroallergens, especially CRM and Japanese cedar pollen, are very different between children from rural and urban areas in Korea.

Adolescent↗

PubMed2001

Antioxidant activities of trypsin inhibitor, a 33 KDa root storage protein of sweet potato (Ipomoea batatas (L.) Lam cv. Tainong 57).

Trypsin inhibitors (TIs), root storage proteins, were purified from sweet potato (Ipomoea batatas[L.] Lam cv. Tainong 57) roots by trypsin affinity column according to the methods of Hou and Lin (Plant Sci. 1997, 126, 11-19 and Plant Sci. 1997, 128, 151-158). A single band of 33 kDa TI was obtained by preparative sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) gels. This purified 33 kDa TI had scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. There was positive correlation between scavenging effects against DPPH (2 to 22%) and amounts of 33 kDa TI (1.92 to 46 pmol). The scavenging activities of 33 kDa TI against DPPH were calculated from linear regression to be about one-third of those of glutathione between 5 and 80 pmol. Using electron paramagnetic resonance (EPR) spectrometry for hydroxyl radical detection, it was found that 33 kDa TI could capture hydroxyl radical, and the intensities of EPR signal were significantly decreased from 1.5 to 6 pmol of 33 kDa TI compared to those of the controls. It is suggested that 33 kDa TI, one of the sweet potato root storage proteins, may play a role as an antioxidant in roots and may be beneficial to health when it is consumed.

Antioxidants↗

PubMed2001

Antioxidant activities of dioscorin, the storage protein of yam (Dioscorea batatas Decne) tuber.

Dioscorin, the storage protein of yam (Dioscorea batatas Decne) tuber (which is different from dioscorine found in tubers of Dioscorea hirsuta), was purified to homogeneity after DE-52 ion exchange column according to the methods of Hou et al. (J. Agric. Food Chem. 1999, 47, 2168-2172). A single band of 32 kDa dioscorin was obtained on a sodium dodecyl sulfate-polyacrylamide gel electrophoresis gel with 2-mercaptoethanol treatment. This purified dioscorin was shown by spectrophotometric method to have scavenging activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical in a pH-dependent manner. There is a positive correlation between scavenging effects against DPPH (8-46%) and amounts of 32 kDa dioscorin (5.97-47.80 nmol) added in Tris-HCl buffer (pH 7.9), which are comparable to those of glutathione at the same concentrations. Using electron paramagnetic resonance (EPR) spectrometry for DPPH radical detection, it was found that the intensities of the EPR signal were decreased by 28.6 and 57 nmol of 32 kDa dioscorin in Tris-HCl buffer (pH 7.9) more than in distilled water compared to controls. EPR spectrometry was also used for hydroxyl radical detection. It was found that 32 kDa dioscorin could capture hydroxyl radical, and the intensities of the EPR signal were significantly decreased dose-dependently by 1.79-14.32 nmol of 32 kDa dioscorin (r = 0.975) compared to the control. It is suggested that 32 kDa dioscorin, the storage protein of yam tuber, may play a role as antioxidant in tubers and may be beneficial for health when people take it as a food additive or consume yam tubers.

Antioxidants↗

PubMed2001

Monoamine oxidase B and free radical scavenging activities of natural flavonoids in Melastoma candidum D. Don.

Monoamine oxidase type B (MAO-B) activity and free radicals are elevated in certain neurological diseases. Four natural flavonoids, quercitrin, isoquercitrin, rutin, and quercetin, were isolated for the first time from the leaves of Melastoma candidum D. Don. They exhibited an inhibitory effect on MAO-B. These potent flavonoids were purified using bioassay-guided fractionation and were separated by Diaion, Sephadex LH-20, and MCI CHP20P columns. The IC(50) values of the four potent flavonoids, quercitrin, isoquercitrin, rutin, and quercetin on monoamine oxidase were 19.06, 11.64, 3.89, and 10.89 microM and enzyme kinetics analysis revealed apparent inhibition constants (K(i)) of 21.01, 2.72, 1.83, and 7.95 microM, respectively, on the substrate, benzylamine. The four potent compounds also exhibited hydroxyl radical scavenging activity as determined using a spin trapping electron spin resonance method. This suggests that the four flavonoids from M. candidum possess both MAO-B inhibitory and free radical scavenging activities. These important properties may be used for preventing some neurodegenerative diseases in the future.

Chromatography, High Pressure Liquid↗

PubMed2001

Phase II study of high-dose lovastatin in patients with advanced gastric adenocarcinoma.

Lovastatin, an inhibitor of mevalonate synthesis, demonstrated in vitro antitumor activity against a variety of human cancer cells, especially in gastric adenocarcinoma cells at pharmacologically achievable concentrations. To determine the antitumor activity of this drug in advanced measurable gastric adenocarcinoma as well as to assess the toxicities and the pharmacokinetic features, we carried out a phase II study of high-dose lovastatin. Patients received lovastatin 35 mg/kg/day for 7 consecutive days, with ubiquinone (60 mg qid p.o.) to prevent rhabdomyolysis. The treatment was repeated every 28 days. From March 1996 to January 1997, 16 patients (median age, 57 years; range, 34-68) were entered into the study, 14 of whom were evaluated for response and toxicity. No patient achieved a response. A total of 28 cycles were administered. The median number of cycles was 2 (range, 1 to 4). Anorexia was the most common toxicity (64%), but decreased oral intake was observed only in 3 cycles. Two patients developed myalgia with elevated muscle enzyme. When used in this dosage and schedule, lovastatin does not appear to be effective for patients with advanced gastric adenocarcinoma.

Adenocarcinoma↗

PubMed2001

High signal intensity of the posterior pituitary gland on T1-weighted MR images. Correlation with plasma vasopressin concentration to water deprivation.

PURPOSE: To evaluate the effect of water deprivation on the signal intensity of the posterior pituitary gland on T1-weighted MR images and correlate the signal intensity with the plasma vasopressin concentration. MATERIAL AND METHODS: Fifteen rabbits were studied: Group 1 (n=10) was deprived of water for 9 days and Group 2 (n=5) was replenished water for 7 days after 7-day water deprivation. MR imaging and plasma vasopressin measurement by radioimmunoassay were made before and after water deprivation and replenishment. Sequential changes of the signal intensity ratio of the posterior lobe to the pons and plasma vasopressin concentration were correlated. RESULTS: Before water deprivation, the hyperintense posterior lobe was demonstrated in all rabbits. During water deprivation, the signal intensity ratio decreased and vasopressin concentration increased gradually. On the contrary, the signal intensity ratio increased and vasopressin concentration decreased with water replenishment. The signal intensity ratio correlated well with the plasma vasopressin concentration (p<0.05). CONCLUSION: There was a negative, linear correlation between the signal intensity ratio of the posterior pituitary gland on T1-weighted MR images and plasma vasopressin concentration to water deprivation. The results support that the high signal intensity of the posterior pituitary gland on T1-weighted MR images is attributed to the normal content of vasopressin-neurosecretory granules.

Animals↗

PubMed2001

Cytoplasmic localization of p21Cip1/WAF1 by Akt-induced phosphorylation in HER-2/neu-overexpressing cells.

Amplification or overexpression of HER-2/neu in cancer cells confers resistance to apoptosis and promotes cell growth. The cellular localization of p21Cip1/WAF1 has been proposed to be critical either in promoting cell survival or in inhibiting cell growth. Here we show that HER-2/neu-mediated cell growth requires the activation of Akt, which associates with p21Cip1/WAF1 and phosphorylates it at threonine 145, resulting in cytoplasmic localization of p21Cip1/WAF1. Furthermore, blocking the Akt pathway with a dominant-negative Akt mutant restores the nuclear localization and cell-growth-inhibiting activity of p21Cip1/WAF1. Our results indicate that HER-2/neu induces cytoplasmic localization of p21Cip1/WAF1 through activation of Akt to promote cell growth, which may have implications for the oncogenic activity of HER-2/neu and Akt.

3T3 Cells↗

PubMed2001

Identification of a gene, ABCG5, important in the regulation of dietary cholesterol absorption.

The molecular mechanisms regulating the amount of dietary cholesterol retained in the body, as well as the body's ability to exclude selectively other dietary sterols, are poorly understood. An average western diet will contain about 250-500 mg of dietary cholesterol and about 200-400 mg of non-cholesterol sterols. About 50-60% of the dietary cholesterol is absorbed and retained by the normal human body, but less than 1% of the non-cholesterol sterols are retained. Thus, there exists a subtle mechanism that allows the body to distinguish between cholesterol and non-cholesterol sterols. In sitosterolemia, a rare autosomal recessive disorder, affected individuals hyperabsorb not only cholesterol but also all other sterols, including plant and shellfish sterols from the intestine. The major plant sterol species is sitosterol; hence the name of the disorder. Consequently, patients with this disease have very high levels of plant sterols in the plasma and develop tendon and tuberous xanthomas, accelerated atherosclerosis, and premature coronary artery disease. We previously mapped the STSL locus to human chromosome 2p21 and further localized it to a region of less than 2 cM bounded by markers D2S2294 and D2S2291 (M.-H.L. et al., manuscript submitted). We now report that a new member of the ABC transporter family, ABCG5, is mutant in nine unrelated sitosterolemia patients.

ATP Binding Cassette Transporter, Subfamily G, Mem↗

PubMed2001

Supramolecular assembly and acid resistance of Helicobacter pylori urease.

Helicobacter pylori, an etiologic agent in a variety of gastroduodenal diseases, produces a large amount of urease, which is believed to neutralize gastric acid by producing ammonia for the survival of the bacteria. Up to 30% of the enzyme associates with the surface of intact cells upon lysis of neighboring bacteria. The role of the enzyme at the extracellular location has been a subject of controversy because the purified enzyme is irreversibly inactivated below pH 5. We have determined the crystal structure of H. pylori urease, which has a 1.1 MDa spherical assembly of 12 catalytic units with an outer diameter of approximately 160 A. Under physiologically relevant conditions, the activity of the enzyme remains unaffected down to pH 3. Activity assays under different conditions indicated that the cluster of the 12 active sites on the supramolecular assembly may be critical for the survival of the enzyme at low pH. The structure provides a novel example of a molecular assembly adapted for acid resistance that, together with the low Km value of the enzyme, is likely to enable the organism to inhabit the hostile niche.

Amino Acid Sequence↗

PubMed2001

Inhibition of interleukin-12 production by auranofin, an anti-rheumatic gold compound, deviates CD4(+) T cells from the Th1 to the Th2 pathway.

1. Interleukin-12 (IL-12) may play a central role in the development and progression of rheumatoid arthritis by driving the immune response towards T helper 1 (Th1) type responses characterized by high IFN-gamma and low IL-4 production. In this study we investigated the effect of auranofin (AF), an anti-rheumatic gold compound, on IL-12 production in mouse macrophages and dendritic cells, and studied whether AF-mediated inhibition of IL-12 production could regulate a cytokine profile of antigen (Ag)-primed CD4(+) Th cells. 2. Treatment with AF significantly inhibited IL-12 production in lipopolysaccharide (LPS)-stimulated macrophages and also in CD40L-stimulated dendritic cells. AF-pretreated macrophages reduced their ability to induce IFN-gamma and increased the ability to induce IL-4 in Ag-primed CD4(+) T cells. AF did not influence the cell surface expression of the class II MHC molecule and the costimulatory molecules CD80 and CD86. 3. Addition of recombinant IL-12 to cultures of AF-pretreated macrophages and CD4(+) T cells restored IFN-gamma production in Ag-primed CD4(+) T cells. 4. The in vivo administration of AF resulted in the inhibition of IL-12 production by macrophages stimulated in vitro with LPS or heat-killed Listeria monocytogenes (HKL), leading to the inhibition of Th1 cytokine profile (decreased IFN-gamma and increased IL-4 production) in Ag-primed CD4(+) T cells. 5. These findings may explain some known effects of AF including anti-rheumatic effects and the inhibition of encephalitogenicity, and point to a possible therapeutic use of AF in the Th1-mediated immune diseases such as autoimmune diseases.

Animals↗

PubMed2001

High-resolution physical and transcript map of human chromosome 2p21 containing the sitosterolaemia locus.

Sitosterolaemia (phytosterolaemia) is an autosomal recessive disorder characterised by the presence of tendon xanthomas in the face of normal or mildly elevated plasma cholesterol levels, premature atherosclerotic disease and has diagnostically elevated plasma and tissue plant sterol concentrations. Affected individuals show an increased absorption of both cholesterol and sitosterol from the diet, decreased bile clearance of these sterols and their metabolites resulting in markedly expanded whole body cholesterol and sitosterol pools. The defective gene is therefore hypothesised to play a crucial role in regulating dietary cholesterol absorption, and its elucidation may shed light on these molecular processes. We have previously localised the defective gene to human chromosome 2p21, between microsatellite markers D2S1788 and D2S1352, a distance of approximately 15 cM. Recently, the disease locus interval has been narrowed to lie between D2S2294 and D2S2291/D2S2174. We have constructed a high-resolution YAC and BAC contigs by using known STSs and generating novel STSs from the minimal interval. Eight previously identified genes and 60 ESTs were mapped to these contigs. The BAC contig contains 60 BAC clones and 108 STSs and encompasses a physical distance of approximately 2.0 cM between microsatellite markers D2S2294 and D2S2291. These results will not only facilitate cloning of the sitosterolaemia gene, but also other disease genes located in this region, and accelerate sequencing of the corresponding genomic clones.

Arteriosclerosis↗

PubMed2001

Fine mapping of a gene responsible for regulating dietary cholesterol absorption; founder effects underlie cases of phytosterolaemia in multiple communities.

Sitosterolaemia (also known as phytosterolaemia, MIM 210250) is a rare recessive autosomal inherited disorder, characterised by the presence of tendon and tuberous xanthomas, accelerated atherosclerosis and premature coronary artery disease. The defective gene is hypothesised to play an important role in regulating dietary sterol absorption and biliary secretion, thus defining a molecular mechanism whereby this physiological process is carried out. The disease locus was localised previously to chromosome 2p21, in a 15 cM interval between microsatellite markers D2S1788 and D2S1352 (based upon 10 families, maximum lodscore 4.49). In this study, we have extended these studies to include 30 families assembled from around the world. A maximum multipoint lodscore of 11.49 was obtained for marker D2S2998. Homozygosity and haplotype sharing was identified in probands from non-consanguineous marriages from a number of families, strongly supporting the existence of a founder effect among various populations. Additionally, based upon both genealogies, as well as genotyping, two Amish/Mennonite families, that were previously thought not to be related, appear to indicate a founder effect in this population as well. Using both homozygosity mapping, as well as informative recombination events, the sitosterolaemia gene is located at a region defined by markers D2S2294 and Afm210xe9, a distance of less than 2 cM.

Arteriosclerosis↗

PubMed2001

Screening and characterization of koji molds producing saline-tolerant protease.

Three mold strains isolated from soil in the Taipei area of Taiwan were compared with a commercial strain of Aspergillus oryzae for their proteolytic activities in an 18% NaCl aqueous solution system. Among these strains, the one subsequently identified and designated as Aspergillus sp. FC-10 produced protease with superior saline tolerance. In aflatoxin tests, this strain did not generate detectable aflatoxin after growing on steamed grain polished rice substrate for 24 days. Two types of extracellular proteases were preliminary fractionated by column chromatography on DEAE Sepharose CL-6B. Proteolytic activity of the nonadsorbed protease (P-I) was reduced to 9.4% in the 18% NaCl solution compared to its original activity determined in the buffer solution. However, the adsorbed protease (P-II) was particularly salt tolerant and stable, with 50% proteolytic activity retained throughout the 6-h stability test in 18% NaCl solution.

Aflatoxins↗

PubMed2001

Purification and characterization of a novel salt-tolerant protease from Aspergillus sp. FC-10, a soy sauce koji mold.

A novel salt-tolerant protease produced by Aspergillus sp. FC-10 was purified to homogeneity through anion-exchange chromatography, preparative isoelectric-focusing electrophoresis, and gel filtration chromatography, with an overall recovery of 12.7%. This protease demonstrated an optimum pH range of 7.0-9.0 for activity, with a stable pH range of 5.0-9.0. The optimum process temperature at pH 7.0 was 65 degrees C. The enzyme has a molecular mass of 28 kDa and was deduced as a monomer with an isoelectric point of 3.75. Enzyme activity was strongly inhibited by 5 mM of HgCl(2) and FeCl(3), and significantly inhibited by 5 mM of CuSO(4), FeSO(4), and MnCl(2). The activity of this purified protease was inhibited by Na(2).EDTA; however, leupeptin, pepstatin A, PMSF, and E-64 did not affect the activity. Based on the N-terminal amino acid sequence and amino acid composition, this purified protease should be classified as a member of the deuterolysin family.

Aspergillus↗

PubMed2001

Citrus red mite (Panonychus citri) may be an important allergen in the development of asthma among exposed children.

BACKGROUND: Recent investigations have demonstrated that spider mites are important allergens in the development of asthma in fruit-cultivating farmers. OBJECTIVE: The aim of this study was to evaluate the sensitization rate to the citrus red mite (Panonychus citri) in children living in rural areas, and to determine the allergenic cross-reactivity with other mites. METHODS: A total of 7254 children (ages 7-15 years) living in rural areas were enrolled, and each subject was evaluated by a questionnaire and a skin prick test. Allergenic cross-reactivity was evaluated by ELISA inhibition tests. RESULTS: The most common sensitizing allergens were house dust mites, followed by citrus red mite and cockroach. High serum-specific IgE bindings to the citrus red mite were detected in 21 of 100 randomly selected subjects. The prevalence of asthma was higher among those with positive skin responses to the citrus red mite than with negative skin responses to this mite. ELISA inhibition tests showed that IgE bindings to this mite were minimally inhibited with additions of domestic mites. CONCLUSION: Spider mites such as the citrus red mite may be important outdoor allergens among children living in rural areas, and spider mite-derived allergens have unique allergenic determinants compared with domestic mites.

Adolescent↗

PubMed2001

Regulation of gene expression, cellular localization, and in vivo function of Caenorhabditis elegans DNA topoisomerase I.

BACKGROUND: DNA topoisomerase I is dispensable in yeast, but is essential during the embryogenesis of Drosophila and mouse. In order to determine functions of the enzyme in the development of Caenorhabditis elegans, phenotypes resulting from the deficiency were observed and correlated with the expression of the gene. RESULTS: The transcriptional regulation of the C. elegans DNA topoisomerase I gene was investigated by mRNA localization and reporter gene expression in C. elegans. The mRNA was expressed in the gonad and in the early embryos, followed by a rapid decrease in its level during the late embryonic stage. A reporter gene expression induced by the 5'-upstream DNA sequence appeared at the comma stage of embryos, continued through the L1 larval stage, and began to decrease gradually afterwards. The DNA topoisomerase I protein was immuno-localized in the nuclei of meiotic gonad cells and interphase embryonic cells, and unexpectedly in centrosomes of mitotic embryonic cells. Double-stranded RNA interference of DNA topoisomerase I gene expression resulted in pleiotropic phenotypes showing abnormal gonadogenesis, oocyte development and embryogenesis. CONCLUSION: These phenotypes, along with expressional regulations, demonstrate that DNA topoisomerase I plays important roles in rapidly growing germ cells and embryonic cells.

Animals↗