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M M Lee

Publications and source records attributed to M M Lee.

At least 73 records · Page 4Linked to original sources
PubMed1997

Characterization and expression of two members of the S-adenosylmethionine decarboxylase gene family in carnation flower.

S-adenosylmethionine decarboxylase (SAMDC; EC 4.1.4.50) is one of the key enzymes in polyamine biosynthesis, and the product of its catalytic reaction, decarboxylated S-adenosylmethionine (dcSAM), serves as an aminopropyl donor in the biosynthesis of spermidine and spermine. In order to provide information on the structure and regulation of SAMDC, we have isolated and sequenced two different SAMDC cDNA clones from carnation petals. The nucleotide sequences of CSDC9 and CSDC16 show 78.3% identity, and the deduced amino acid sequences show 81.7% identity and 86.5% similarity [12]. There are several regions with highly conserved sequences among SAMDC cDNAs of potato, spinach, periwinkle, man and yeast. These conserved regions include a cleavage site for the processing of SAMDC proenzyme and a putative PEST sequence that may be relevant to the rapid degradation of SAMDC protein. Carnation SAMDC cDNAs have long transcript leaders of 472 bp and 502 bp for CSDC9 and CSDC16, respectively. Both sequences contain short upstream open reading frames (uORFs) in their 5'-untranslated regions. The CSDC9 uORF is 54 amino acids from 152 to 317 while the corresponding sequence in CSDC16 is 52 amino acids located from 156 to 314 in each 5'-untranslated region. The nucleotide sequences of uORFs in CSDC9 and CSDC16 were 89.9% identical. In vitro transcription/translation experiments showed: (1) each proenzyme of both cDNAs of SAMDC was converted to two polypeptides consisting of a large subunit (calculated as 31,544 Da and 32,537 Da, respectively) and a small subunit (calculated as 9704 and 9041 Da, respectively) after 20 min of translation; (2) the processing occurs rapidly during the translation of protein. But once the translation process is stopped accumulation of the subunits slows and never reaches completion even after 300 min. The processing of carnation SAMDC enzyme is not stimulated by putrescine in in vitro transcription/translation reaction.

Adenosylmethionine Decarboxylase↗
PubMed1997

Characterization of a highly conserved gene (OS4) amplified with CDK4 in human sarcomas.

Amplification and overexpression of genes involved in cellular growth control occur frequently in human cancers. Here, we report characterization of the full length OS4 cDNA derived from 12q13-q15 (Su et al., Proc. Natl. Acad. Sci. USA, 91: 9121-9125, 1994), a region frequently amplified in sarcomas and brain tumors. This cDNA consists of 4833 base pairs (bp) encoding an open reading frame (ORF) of 283 amino acids. The ORF predicts a water-soluble acidic (pI 5.50) polypeptide with a molecular weight of 31759. Database searches revealed highly significant similarity between OS4 and eight proteins predicted from genomic sequences of Caenorhabditis elegans, Schizosaccaharomyces pombe, and Saccharomyces cerevisiae. Thus, OS4 defines a novel evolutionarily conserved gene superfamily. Northern and database analyses revealed OS4 transcripts in numerous human tissues demonstrating its ubiquitous expression. We also observed overexpression of OS4 in three cancer cell lines with amplification of this gene. Furthermore, we detected OS4 amplification in 5/5 primary sarcomas with known amplification of the closely linked marker CDK4. These results demonstrate that the highly conserved OS4 gene is frequently included in the 12q13-q15 amplicon and may contribute to the development of a subset of sarcomas.

Amino Acid Sequence↗
PubMed1997

Angiotensin I converting enzyme gene polymorphism and insulin resistance in patients with hypertension.

BACKGROUND: The homozygote deletion (DD) genotype of the angiotensin I converting enzyme (ACE) gene has been shown to be associated with an increased risk of coronary heart disease independent of other risk factors. OBJECTIVE: To investigate the possible association of the insertion/deletion (I/D) polymorphism of the ACE gene with insulin resistance in a Chinese population with and without hypertension. SUBJECTS AND METHODS: The I/D polymorphism of the ACE gene was determined for 361 Chinese including 148 women and 96 men with normal blood pressures and 64 male and 53 female patients with mild-to-moderate hypertension. Insulin resistance was estimated by the insulin suppression test and glucose intolerance evaluated with an oral glucose-tolerance test for all of the subjects. RESULTS: Three hypertensive subgroups with DD, DI and II genotypes having similar ages and body mass indexes presented insignificantly different degrees of glucose intolerance and insulin resistance both among men and among women. Similar results were found for normotensive subjects. In addition, ACE genotypes were not significant predictors of insulin resistance and glucose intolerance either among men or among women after adjustment for age, body mass index, and hypertension. CONCLUSION: The present data indicated that the I/D polymorphism of the ACE gene was not related to insulin resistance for Chinese hypertensive and normotensive subjects. The increased risk of coronary heart disease associated with the DD genotype need not be mediated through the mechanism of insulin resistance and glucose intolerance for Chinese patients with hypertension.

Adult↗
PubMed1997

Temperature-guided radiofrequency catheter ablation of accessory pathway.

OBJECTIVES: This study was performed to evaluate the usefulness of temperature-guided radiofrequency catheter ablation for the elimination of accessory pathway conduction in patients with Wolff-Parkinson-White syndrome. METHODS: Temperature-guided radiofrequency catheter ablation was attempted in 138 patients with 144 accessory pathways (88 pathways along the left free wall, 5 in the anteroseptal region, 2 in the midseptal region, 19 in the posteroseptal region and 30 along the right free wall). The energy source was a HAT 200S which regulated the power automatically to the set temperature of 70 degrees C. Radiofrequency current was delivered through a thermocatheter to the atrial or ventricular side of mitral or tricuspid annulus. RESULTS: Accessory pathway conduction was eliminated in 130 of 144 pathways (90.3%). The mean power outputs of the successful ablations at the atrial side of the annulus were higher than those at the ventricular side (34.0 +/- 8.9W versus 20.0 +/- 7.6W, p < 0.01), but the maximum temperatures were lower at the atrial side of the annulus than those at the ventricular side (66.4 +/- 14.0 degrees C versus 77.2 +/- 6.4 degrees C, p < 0.01). There were 3 non-fatal complications (2.1%), 2 patients with hemopericardium and 1 with femoral artery thrombus, during or after ablation procedures. Recurrences of AV re-entrant tachycardia or delta wave on the electrocardiogram occurred in 4 patients (2.8%) who had successful second procedures. There were no late complications during a mean follow-up period of 41 +/- 25 months (range, 3 to 55). CONCLUSION: We conclude that 1) temperature-guided radiofrequency catheter ablation can be performed reliably and safely in eliminating accessory pathway conduction in patients with WPW syndrome, and 2) temperature monitoring and adjustment of the power to the set temperature during ablation would be useful for the avoidance of impedance rises and coagulum formation.

Adolescent↗
PubMed1996

Schwann cells stimulated by axolemma-enriched fractions express cyclic AMP responsive element binding protein.

Both axolemma-enriched fractions (AEF) and cyclic AMP have been shown to regulate the proliferation and differentiation of cultured primary Schwann cells (SC). We have evaluated the role of CREB, a transcription factor that binds to the cAMP-responsive element, in mediating the AEF-stimulated SC proliferation and differentiation. We detected CREB in nuclear extracts derived from SC stimulated with 40 micrograms/ml of AEF for 16, 24, 48, 72, and 96 hr, using a DNA-electrophoretic mobility shift assay. Unstimulated quiescent SC contained low levels of CREB which increased to a maximal level after 48 hr of AEF treatment. Using anti-CREB antibodies and Western blot analysis, after 24 hr of AEF treatment we first detected CREB as a 45 kDa protein which reached a maximal level of expression after 72 hr. Double labeled immunocytochemistry using anti-CREB and anti-5-bromo-2'-deoxy-uridine antibodies demonstrated maximal CREB expression after 72 hr of AEF treatment, closely coinciding with the temporal expression of SC proliferation. At all times examined, all AEF-treated SC labeled by anti-CREB antibodies were also labeled with anti-BrdU antibodies. These observations are consistent with the view that CREB could play an important role in the induction of SC proliferation by AEF.

Animals↗
PubMed1996

Influence of calcium channel blocker treatment on the mechanical properties of diabetic rat myocardium.

The objective of this investigation was to determine whether calcium channel blocker (CCB) treatment effectively restores normal baseline mechanical function in diabetic myocardium and to evaluate its effect on the interval-strength relationship. Wistar rats were made diabetic with streptozotocin (55 mg/kg, IV). Left-ventricular papillary muscles from normal and diabetic (10 weeks) rats were superfused with Tyrode's solution at 30 degrees C. A subgroup of diabetic and normal animals received daily injections of verapamil or nifedipine (10 mg/kg, IP; 8 weeks) to compare the effectiveness of a phenylalkylamine to a dihydropyridine in reversing diabetes-induced contractile dysfunction in vitro. Muscles were electrically stimulated at 0.5 Hz with suprathreshold stimuli, and the following parameters were measured: peak tension developed, time to-peak tension, time-to-90% relaxation, and the maximum velocities of tension development and decay. Experimental diabetes was characterized by: severe hyperglycemia, hepatomegaly, reduced body weight gain, cardiomegaly, and increased plasma phospholipid levels. In addition, baseline values of peak tension developed, time to-peak tension, and time-to-90% relaxation were significantly greater in muscles from diabetic animals. Chronic nifedipine treatment reduced hyperglycemia and plasma phospholipid levels, normalized body weight gain, and reduced both heart and liver sizes in diabetic animals. Nifedipine treatment completely reversed diabetes-induced prolongation in both time-to-peak tension and time-to-90% relaxation. In diabetic myocardium, a slightly positive component was present in the interval-strength relationship between 0.01 and 1 Hz, resulting in a rightward shift in the entire curve across a wide range of stimulation frequencies (0.01-5 Hz). This positive component was absent in muscles from diabetic animals treated with both CCBs, and verapamil produced a leftward shift in the frequency response curve. The results of this study suggest that chronic nifedipine treatment may be more effective than verapamil in restoring normal baseline myocardial mechanical function, reducing hyperglycemia and hyperlipidemia, as well as attenuating both cardiac and liver enlargement in experimental diabetes. In contrast, verapamil treatment tended to normalize more effectively the inotropic response to changes in stimulation frequency in diabetic myocardium.

Analysis of Variance↗
PubMed1996

Differential effects of chronic calcium channel blocker treatment on the inotropic response of diabetic rat myocardium to acute ethanol exposure.

Cardiomyopathy is a consistent feature of diabetic myocardium as well as in prolonged alcohol consumption. Diabetes-induced myocardial dysfunction has been attributed, in part, to calcium overload within individual myocytes. The present study compares the effectiveness of the calcium channel blocker nifedipine (dihydropyridine-type) with verapamil (phenylalkylamine-type) in reversing myocardial dysfunction and diminishing the negative inotropic effect of ethanol on diabetic rat myocardium. Wistar rats were made diabetic with streptozotocin (55 mg/kg, i.v.) and isolated electrically stimulated papillary muscles were studied under isometric conditions in the absence and presence of clinically relevant concentrations of ethanol (80-240 mg/dl, i e., 17.4-52.1 mM). Subgroups of diabetic and normal animals received daily injections of verapamil or nifedipine 2 weeks after induction of diabetes for 8 weeks. Untreated diabetic animals exhibited hyperglycemia, hyperlipidemia, reduced growth, cardiomegaly, and hepatomegaly. Compared to verapamil chronic nifedipine treatment normalized or reversed the effects of diabetes on myocardial mechanical function. The negative inotropic effect of ethanol was attenuated only in muscles from verapamil-treated diabetic animals. Thus, chronic nifedipine treatment may be more effective than verapamil in reducing hyperglycemia, attenuating both cardiac and liver enlargement, and restoring myocardial mechanical function, in experimental diabetes. However, chronic verapamil therapy is more effective in diminishing the negative inotropic effect of ethanol on diabetic myocardium. These findings may have clinical significance among diabetic patients who consume alcoholic beverages while receiving long-term calcium blocker therapy.

Animals↗
PubMed1996

Airway surfactant, a primary defense barrier: mechanical and immunological aspects.

Epidemiologic studies have shown strong associations between mortality and morbidity from respiratory and cardiac causes and exposure to fine (PM10), but not coarse, particulates. A plausible mechanistic explanation for these associations is lacking. It has been shown that particles may be retained for an extended period of time in the airways, and that their clearance is inversely proportional to particle size. Such particles are localized in close association with the airway epithelium, and if they consist of low surface energy material, will be coated with an osmiophilic layer, consistent with surfactant. Particles are displaced into this position by surface and line tension forces exerted by the surfactant film at the air-aqueous interface. Particle displacement due to line tension is much greater for smaller particles in the micrometer range. The surface forces acting on the particles leave deep indentations on the epithelial cells. During the displacement process they may come into contact with airway macrophages in the mucous layer and/or dendritic cells situated in the airway epithelium. The smallest particles may even penetrate the mucosa to enter the interstitial compartment. In addition to altering the physical properties of particles, surfactant coatings reduce particle toxicity and enhance phagocytosis by opsonization. We speculate that surfactant acts as a primary defense barrier and plays a role in antigen presentation and elimination at the air-mucus interface of the airways.

Air Pollutants↗
PubMed1996

Developmental expression of a candidate müllerian inhibiting substance type II receptor.

We have isolated a candidate Müllerian inhibiting substance (MIS) type II receptor complementary DNA from an embryonic rat urogenital ridge library and have studied its binding to MIS, its developmental pattern of expression and tissue distribution. By in situ hybridization with a full-length riboprobe, the receptor is expressed in the mesenchymal cells surrounding the Müllerian duct at embryonic days 14, 15, and 16 and in tubular and follicular structures of the rat fetal gonads. Expression of the messenger RNA was also seen in the granules cells and seminiferous tubules of pubertal gonads. Northern analysis revealed that the MIS type II receptor messenger RNA is highly expressed in embryonic, pubertal, and adult testes and ovaries, as well as in the gravid uterus. The timing of expression in the gonads of both sexes was also analyzed by Northern analyses that showed high levels of expression at the time of Müllerian duct regression, much lower levels neonatally and prepubertally and then increased expression again with sexual maturation. The tissue and developmental specificity of expression of this receptor, which make it likely that this is the functional MIS type II receptor, can be used to advantage in therapeutic targeting strategies and to decipher the function of MIS in the gonads.

Aging↗
PubMed1996

Mullerian inhibiting substance in humans: normal levels from infancy to adulthood.

Mullerian-inhibiting substance (MIS) is a gonadal hormone synthesized by Sertoli cells of the testis and granulosa cells of the ovary. To facilitate the use of MIS for the evaluation of intersex disorders and as a tumor marker in women with MIS-expressing ovarian tumors, we measured MIS in 600 serum samples from males and females. These data show that mean MIS values for males rise rapidly during the first year of life and are highest during late infancy, then gradually decline until puberty. In contrast, MIS values in females are lowest at birth and exhibit a minimal increase throughout the prepubertal years. Whereas MIS is uniformly measurable in all prepubertal boys studied, it is undetectable in most prepubertal female subjects. These data reveal an easily discernible sexually dimorphic pattern of expression and confirm that MIS can be used as a testis-specific marker during infancy and early childhood. MIS values that are above the upper limits for females are discriminatory for the presence of testicular tissue or ovarian tumor, and those below the lower limits for males are consistent with dysgenetic or absent testes or the presence of ovarian tissue. These data will enable normal and abnormal levels of MIS to be differentiated with higher precision and will facilitate the use of MIS in the management of gonadal disorders.

Adolescent↗
PubMed1996

Stimulatory influence of soy protein isolate on breast secretion in pre- and postmenopausal women.

Soy foods have been reported to have protective effects against premenopausal breast cancer in Asian women. No studies have been reported on potential physiological effects of dietary soy consumption on breast gland function. We evaluated the influence of the long-term ingestion of a commercial soy protein isolate on breast secretory activity. We hypothesized that the features of nipple aspirate fluid (NAF) of non-Asian women would be altered so as to resemble those previously found in Asian women. At monthly intervals for 1 year, 24 normal pre- and postmenopausal white women, ages 30 to 58, underwent nipple aspiration of breast fluid and gave blood and 24-h urine samples for biochemical studies. No soy was administered in months 1-3 and 10-12. Between months 4-9 the women ingested daily 38 g of soy protein isolate containing 38 mg of genistein. NAF volume, gross cystic disease fluid protein (GCDFP-15) concentration, and NAF cytology were used as biomarkers of possible effects of soy protein isolate on the breast. In addition, plasma concentrations of estradiol, progesterone, sex hormone binding globulin, prolactin, cholesterol, high density lipoprotein-cholesterol, and triglycerides were measured. Compliance was assessed by measurements of genistein and daidzein and their metabolites in 24-h urine samples. Excellent compliance with the study protocol was obtained. Compared with NAF volumes obtained in months 1-3, a 2-6-fold increase in NAF volume ensued during months 4-9 in all premenopausal women. A minimal increase or no response was found in postmenopausal women. No changes were found in plasma prolactin, sex hormone binding globulin, cholesterol, high density lipoprotein cholesterol, and triglyceride concentrations. Compared with concentrations found in months 1-3 (no soy), plasma estradiol concentrations were elevated erratically throughout a "composite" menstrual cycle during the months of soy consumption. No significant changes were seen in plasma progesterone concentrations. No significant changes were found in plasma estrogen levels in postmenopausal women. A moderate decrease occurred in the mean concentration of GCDFP-15 in NAF in premenopausal women during the months of soy ingestion. Of potential concern was the cytological detection of epithelial hyperplasia in 7 of 24 women (29.2%) during the months they were consuming soy protein isolate. The findings did not support our a priori hypothesis. Instead, this pilot study indicates that prolonged consumption of soy protein isolate has a stimulatory effect on the premenopausal female breast, characterized by increased secretion of breast fluid, the appearance of hyperplastic epithelial cells, and elevated levels of plasma estradiol. These findings are suggestive of an estrogenic stimulus from the isoflavones genistein and daidzein contained in soy protein isolate.

Adult↗
PubMed1995

Evolution of left atrial thrombus with anticoagulant therapy-follow-up by transesophageal echocardiography.

OBJECTIVES: Atrial fibrillation is an important risk factor for systemic embolism. A number of clinical studies demonstrated the beneficial effect of anticoagulant therapy for the prevention of embolism. But there has been no study on the fate of left atrial thrombus demonstrated by transesophageal echocardiography in the course of anticoagulation therapy. METHODS: Thirteen patients, demonstrated to have left atrial thrombus by transesophageal echocardiography were followed with anticoagulation therapy. Repeated transesophageal echocardiography was done 15 months after 1st study. RESULTS: Among 9 patients with adequate anticoagulation effect (INR > 2.0), left atrial thrombus disappeared in 3 patients. The size of thrombus decreased from 2.2 +/- 0.8cm to 0.9 +/- 1.0cm (p < 0.05 by paired Student's t-test). CONCLUSIONS: Left atrial thrombus could dissolve or decrease in size with adequate anticoagulation.

Coronary Thrombosis↗
PubMed1994

Targeted deletion of the TGF-beta 1 gene causes rapid progression to squamous cell carcinoma.

To study the contribution of autocrine and paracrine TGF-beta 1 to tumor progression in a well-defined system of multistage carcinogenesis, keratinocytes with a targeted deletion of the TGF-beta 1 gene were initiated in vitro with the v-rasHa oncogene and their in vivo tumorigenic properties were determined by skin grafting initiated cells onto athymic mice in combination with either wild-type or null dermal fibroblasts. Grafts of v-rasHa-initiated null keratinocytes progressed rapidly to multifocal squamous cell carcinomas within dysplastic papillomas irrespective of the fibroblast genotype, whereas the initiated control genotypes formed well-differentiated papillomas. Malignant progression was not associated with mutations in the c-rasHa gene, alterations in p53 protein, or loss of responsiveness to TGF-beta 1. The tumor cell labeling index was elevated in grafts of initiated null keratinocytes with wild-type fibroblasts compared to tumors of other genotypes. However, labeling index in all tumors was reduced when TGF-beta 1 null fibroblasts formed the stroma. The null tumor cells could not accumulate TGF-beta 1 from the host, but grafts of uninitiated null keratinocytes, which formed a normal epidermis, became TGF-beta 1 positive even though they did not express TGF-beta 1 mRNA. These results demonstrate that autocrine TGF-beta 1 suppresses the frequency and rate of malignant progression, and that autocrine and paracrine TGF-beta 1 can have opposing effects on tumor cell proliferation. The lack of paracrine inhibition of tumor cell progression appears to result from the inability of tumor cells to localize host-derived TGF-beta 1 by a mechanism that operates in normal cells.

Animals↗
PubMed1994

Cell-substrate adhesion and metastatic potential of cultured mesothelioma cells induced by asbestos.

Cell-substrate adhesion was quantified for two cultured mesothelioma cell lines (epitheliomatous and sarcomatous) on glass, fibronectin and laminin substrates. Interference reflection microscopy (IRM) was used to image the adhesion patterns of cells and a grey level analysis was employed to quantify adhesion. Sarcomatous cells demonstrated marked adhesion to glass and fibronectin-coated substrates but not to laminin-coated substrate, with the greatest adhesion occurring on the fibronectin-coated surface. This adhesion was accompanied by cytoplasmic spreading. By contrast, epitheliomatous cells showed little tendency to adhere to any of the substrates and only showed significant spreading when in contact with the laminin substrate (P < 0.01). A bioassay was used to determine the metastatic potential of each of the cell lines. Via the intravenous route, the sarcomatous cells killed the host rats in 24.7 +/- 1.5 (S.D.) days compared to 27.3 +/- 0.9 (S.D.) days for the epitheliomatous cells (P < 0.01). After subcutaneous inoculation of tumour cells, the sarcomatous cells killed the host rats in 54.7 +/- 0.7 (S.D.) days compared to 48.5 +/- 0.5 (S.D.) days for the epitheliomatous cells (P < 0.01). We conclude that the results of the metastasis bioassays were consistent with the predicted behavior of these cell lines based on their ability to adhere to substrates in the in vitro adhesion assays.

Animals↗
PubMed1994

The interrelationship between impaired glucose tolerance and other risk factors for cardiovascular disease: is it a predictor for cardiovascular disease?

Glucose intolerance and cardiovascular risk factors were assessed among 215 subjects aged 27-86 years in Ho-long, Taiwan. An oral glucose tolerance test (OGTT) was normal in 107 subjects, impaired in 41 subjects, and abnormal in 67 subjects (as noninsulin dependent diabetes mellitus, NIDDM). Body fatness, blood pressure, carbohydrate and lipid metabolic factors were examined. One-way ANCOVA was used to compare age- and/or BMI-adjusted differences among these groups. Male subjects with NIDDM and impaired glucose tolerance (IGT) had higher systolic (SBP) and diastolic (DBP) blood pressures, plasma insulin (fasting and 1-hour after OGTT), serum triglycerides (TG), heavier body weight, and larger BMI than normal. IGT subjects were also found to have higher TG, insulin (2-hour) and larger insulin area under curve (IAUC) after OGTT than NIDDM. In females, subjects with NIDDM had higher TG, insulin (fasting and 1-hour after OGTT), and larger IAUC than normal. Moreover, female IGT subjects were also found to have significantly higher SBP, DBP, insulin (1-and 2-hour after OGTT), and larger IAUC than both normal and NIDDM subjects. These results suggest that adverse cardiovascular risk factors are present not only in NIDDM subjects, but also in IGT subjects.

Adult↗
PubMed1994

A semiquantitative dietary history questionnaire for Chinese Americans.

An 84-item, semiquantitative dietary history questionnaire was developed for epidemiologic studies of diet and diseases in Chinese Americans. The questionnaire is a 30-minute, face-to-face administered instrument designed especially for assessing mixed dishes; it consists of a food list and requires information on frequency of consumption and portion estimation. A nutrient database was compiled from many sources, but mostly from US Department of Agriculture publications. The relative validity of this food frequency questionnaire was tested among 74 Chinese women between the ages of 30 and 60 years living in the San Francisco Bay area against a 1-day recall deemed a typical day's diet. Correlation coefficients of nutrients from both methods ranged from 0.2 for total fat to 0.7 for calcium and were all statistically significant at less than the 0.001 level. Agreement between these two methods was assessed by the percentage of misclassification of quartile distributions. Around 10% were grossly misclassified and 50% were correct estimates of intake in the same highest quartile, while 73% were correctly placed in the two highest quartiles. This food frequency questionnaire can reasonably estimate the usual dietary intakes among Chinese Americans for epidemiologic studies, but further validation would be needed.

Adult↗