Biomedical subjects

M K Lee

Publications and source records attributed to M K Lee.

At least 37 records · Page 2Linked to original sources

PubMed2001

Mutations at the arginine residues in alpha8 loop of Bacillus thuringiensis delta-endotoxin Cry1Ac affect toxicity and binding to Manduca sexta and Lymantria dispar aminopeptidase N.

The functional role of the alpha8 loop residues in domain II of Bacillus thuringiensis Cry1Ac toxin was examined. Alanine substitution mutations were introduced in the residues from 275 to 293. Among the mutant toxins, substitutions at R281 and R289 affected toxicity to Manduca sexta and Lymantria dispar. Loss of toxicity by these mutant toxins was well correlated with reductions in binding affinity for brush border membrane vesicles and the purified receptor, aminopeptidase N (APN), from both insects. These data suggest that the two arginine residues in the alpha8 loop region are important in toxicity and APN binding in L. dispar and M. sexta.

Amino Acid Substitution↗

PubMed2001

Generation of macrophages from early T progenitors in vitro.

Early T progenitors in the thymus have been reported to have the capacity to develop into B cells, thymic dendritic cells, and NK cells. Here we describe conditions that induce early T progenitors to develop into macrophages. Initially, we observed that early T progenitors could be induced to develop into macrophages by cytokines produced from a thymic stromal cell line, TFGD, and later we found that the cytokine mixture of M-CSF plus IL-6 plus IL-7 also induced macrophage differentiation from pro-T cells. M-CSF by itself was unable to induce macrophage differentiation from early T progenitors. To correlate this observation with the developmental potential of early T progenitors, mouse embryonic thymocytes were sorted into four populations, pro-T1 to pro-T4, based on the expression of CD44 and CD25, and then cultured with TFGD culture supernatant. We found that pro-T1 and pro-T2 cells, but not pro-T3 and pro-T4 cells, generate macrophages. Limiting dilution analysis of the differentiation capability of sorted pro-T2 cells also confirmed that pro-T2 cells could generate macrophages. These results suggest that T cells and thymic macrophages could originate from a common intrathymic precursor.

Animals↗

PubMed2001

Duration of hospitalization as a measure of cost on Children's Cancer Group acute lymphoblastic leukemia studies.

PURPOSE: We used duration of hospitalization as a surrogate for cost and event-free survival as a measure of effectiveness to estimate the cost-effectiveness ratios of various treatment regimens on Children's Cancer Group trials for acute lymphoblastic leukemia. PATIENTS AND METHODS: The analyses included 4,986 children (2 to 21 years of age) with newly diagnosed acute lymphoblastic leukemia enrolled onto risk-adjusted protocols between 1988 and 1995. Analyses were based on a model of 100 patients. The marginal cost-effectiveness ratio (hospital days per additional patient surviving event-free) was the difference in total duration of hospitalization divided by the difference in number of event-free survivors at 5 years for two regimens. Relapse-adjusted marginal cost of frontline therapy was the difference in total duration of hospitalization for frontline therapy plus relapse therapy divided by the difference in number of event-free survivors at 5 years on the frontline therapy for two regimens. RESULTS: One or two delayed intensification (DI) phases, augmented therapy, and dexamethasone all improved outcome. Marginal cost-effectiveness of these regimens compared with the control regimens was 133 days per patient for DI, 117 days per patient for double DI, and 41 days per patient for augmented therapy. Dexamethasone resulted in 17 fewer days per patient. Relapse-adjusted marginal costs were 68 days per patient for DI and 52 days for double DI. Augmented therapy and dexamethasone-based therapy resulted in 16 and 82 fewer hospital days, respectively. The estimated cost-effectiveness for treating any first relapse was 250 days per patient. CONCLUSION: DI, double DI, augmented therapy, and dexamethasone-based therapy are cost-effective strategies compared with current treatment of first relapse.

Adolescent↗

PubMed2001

A novel sodium bicarbonate cotransporter-like gene in an ancient duplicated region: SLC4A9 at 5q31.

BACKGROUND: Sodium bicarbonate cotransporter (NBC) genes encode proteins that execute coupled Na+ and HCO3- transport across epithelial cell membranes. We report the discovery, characterization, and genomic context of a novel human NBC-like gene, SLC4A9, on chromosome 5q31. RESULTS: SLC4A9 was initially discovered by genomic sequence annotation and further characterized by sequencing of long-insert cDNA library clones. The predicted protein of 990 amino acids has 12 transmembrane domains and high sequence similarity to other NBCs. The 23-exon gene has 14 known mRNA isoforms. In three regions, mRNA sequence variation is generated by the inclusion or exclusion of portions of an exon. Noncoding SLC4A9 cDNAs were recovered multiple times from different libraries. The 3' untranslated region is fragmented into six alternatively spliced exons and contains expressed Alu, LINE and MER repeats. SLC4A9 has two alternative stop codons and six polyadenylation sites. Its expression is largely restricted to the kidney. In silico approaches were used to characterize two additional novel SLC4A genes and to place SLC4A9 within the context of multiple paralogous gene clusters containing members of the epidermal growth factor (EGF), ankyrin (ANK) and fibroblast growth factor (FGF) families. Seven human EGF-SLC4A-ANK-FGF clusters were found. CONCLUSION: The novel sodium bicarbonate cotransporter-like gene SLC4A9 demonstrates abundant alternative mRNA processing. It belongs to a growing class of functionally diverse genes characterized by inefficient highly variable splicing. The evolutionary history of the EGF-SLC4A-ANK-FGF gene clusters involves multiple rounds of duplication, apparently followed by large insertions and deletions at paralogous loci and genome-wide gene shuffling.

Adult↗

PubMed2001

Role of alpha-helix seven of Bacillus thuringiensis Cry1Ab delta-endotoxin in membrane insertion, structural stability, and ion channel activity.

Domain I of the Cry1Ab insecticidal toxic protein has seven alpha-helices and is considered to be involved in the ion channel activity. While other alpha-helices, particularly alpha-4 and alpha-5, have been extensively explored, the remaining alpha-helices have been slightly studied. Site-directed mutagenesis was used to generate mutations throughout sequences encoding the alpha-helix 7 to test its role in ion channel function. Every amino acid residue in alpha-helix 7 was mutated to alanine. Most resultant proteins, e.g., D225A, W226A, Y229A, N230A, R233A, R234A, D242A, and F247A yielded no protoxin or were sensitive to degradation by trypsin or Manduca sexta midgut juice. Other mutant proteins, R224A, R228A, and E235A, were resistant to degradation to the above proteases but were 8, 30, and 12 times less toxic to M. sexta, respectively, than the wild-type Cry1Ab. Circular dichroism spectroscopy indicated a very small change in the R228A spectrum, while R224A and E235A display the same spectrum as the wild-type protein. These three mutant proteins showed little differences from Cry1Ab when analyzed by saturation binding and competition binding kinetics with (125)I-labeled toxin or by surface plasmon resonance to M. sexta brush border membrane vesicles. More conservative amino acid substitutions were introduced into alpha-helix 7 residues: R228K, F232Y, E235Q, and F247Y. In comparison with wild-type Cry1Ab, mutant proteins R228K, F232Y, E235A, and E235Q selectively discriminate between K+ and Rb+, while R224A and R228A had reduced inhibition of short-circuit current for both ions, when analyzed by voltage clamping of M. sexta midguts.

Amino Acid Substitution↗

PubMed2001

Usefulness of diabetic retinopathy as a marker of risk for thallium myocardial perfusion defects in non-insulin-dependent diabetes mellitus.

Among 236 non-insulin-dependent diabetics with clinically suspected coronary artery disease, the rate of thallium-201 myocardial perfusion defects was significantly higher in subjects with (40.6%) than without (22.1%) diabetic retinopathy. Retinopathy was associated with a higher risk of perfusion defects in subjects with cardiac and noncardiac chest pain, and may thus be a useful marker for selecting patients in whom thallium scintigraphy screening is warranted.

Chi-Square Distribution↗

PubMed2001

Identification of two proteins, S14 and UIP1, that interact with UCH37.

By the use of the yeast two-hybrid screen we have identified two proteins that interacted with UCH37: S14, which is a subunit of PA700 and a novel protein, UIP1 (UCH37 interacting protein 1). The interaction of UCH37 with S14 or UIP1 was confirmed by in vitro binding assay and in vivo co-immunoprecipitation analysis. The C-terminal extension of UCH37 is essential for interaction with S14 or UIP1 as shown by the yeast two-hybrid assay and the in vitro binding assay. Furthermore, UIP1 blocked the interaction between UCH37 and S14 in vitro.

Amino Acid Sequence↗

PubMed2001

Isolation and partial characterization of gypsy moth BTR-270, an anionic brush border membrane glycoconjugate that binds Bacillus thuringiensis Cry1A toxins with high affinity.

BTR-270, a gypsy moth (Lymantria dispar) brush border membrane molecule that binds Bacillus thuringiensis (Bt) Cry1A toxins with high affinity, was purified by preparative gel electrophoresis. Rabbit antibodies specific for the Bt toxin-binding molecule were raised. Attempts to label BTR-270 by protein-directed techniques were futile, but it was degraded by proteases with broad specificity indicating the presence of a peptide. Carbohydrate was detected by labeling with digoxigenin hydrazide following periodate oxidation. Mild alkaline hydrolysis destroyed toxin and antibody binding, suggesting O-linked glycans are involved in the activity. GC/MS composition analysis showed that the predominant sugars were galactose, glucose, and N-acetyl galactosamine with lesser amounts of N-acetyl glucosamine, glucuronic acid, xylose, and fucose. The carbohydrate moiety accounted for 73% of its total mass. Amino acid analysis showed a high content of aspartic/asparagine, threonine, and serine residues in the protein moiety. The purified glycoconjugate was not visualized using Coomassie or silver staining procedures, but stained "blue" using the cationic dye Stains-all. BTR-270 was labeled with biotin and used as a diagnostic probe for screening and identifying toxins that bind to the receptor. Toxin-binding kinetics obtained using a biosensor demonstrated that the receptor binds Cry1Aa and Cry1Ab toxins with high affinity, and displays a weaker affinity for Cry1Ac, in correlation with the toxicity of these toxins towards gypsy moth. Arch.

Amino Acids↗

PubMed2001

Inhibitory effects of sanguinarine on monoamine oxidase activity in mouse brain.

The effects of benzophenanthridine alkaloids, such as sanguinarine and chelidonine, on monoamine -oxidase (MAO) activity in mouse brain were investigated. Sanguinarine showed an inhibitory effect on MAO activity in a concentration dependent manner (53.4% inhibition at 25 microM). However, chelidonine did not inhibit MAO activity. The IC(50) value of sanguinarine was 24.5 microM. Sanguinarine inhibited non-competitively MAO activity using kynuramine as a substrate. The K(i) value for sanguinarine was 22.1 microM. These results suggest that sanguinarine partially contributes to the regulation of catecholamine content.

Alkaloids↗

PubMed2001

Inhibition of baclofen on morphine-induced hyperactivity, reverse tolerance and postsynaptic dopamine receptor supersensitivity.

The effects of baclofen on the development of reverse tolerance and postsynaptic dopamine receptor supersensitivity induced by morphine were examined in mice. A single administration of morphine induced hyperactivity and the morphine-induced hyperactivity was inhibited dose dependently by the administration of a GABA(B)receptor agonist, baclofen (1.25, 2.5 and 5 mg kg(-1), i.p.). Daily repeated administration of morphine developed reverse tolerance to the hyperactivity of morphine. The concomitant administration of baclofen inhibited the morphine-induced hyperactivity and the baclofen administration prior to and during the chronic administration of morphine in mice inhibited the development of reverse tolerance to the hyperactivity of morphine (10 mg kg(-1), s.c.). Postsynaptic dopamine receptor supersensitivity was also developed in reverse-tolerant mice that had received the same morphine. The development of postsynaptic dopamine receptor supersensitivity was evidenced by the enhanced ambulatory activity of apomorphine (2 mg kg(-1), s.c.). Baclofen also inhibited the development of postsynaptic dopamine receptor supersensitivity induced by the chronic administration of morphine. These results suggest that the hyperactivity, reverse tolerance and postsynaptic dopamine receptor supersensitivity induced by morphine may be modulated via the activation of GABA(B)receptors induced by baclofen.

Animals↗

PubMed2001

Inhibitory effects of MK-801 on contextual sensitization to climbing behavior and on development of tolerance to hypothermia induced by a single high dose of apomorphine.

A single high dose of apomorphine (10 mg x kg(-1)) produced not only contextual sensitization to and conditioning of climbing behavior, but also context-independent tolerance to hypothermia. MK-801 (0.15 and 0.3 mg x kg(-1)) inhibited contextual sensitization to and conditioning of climbing behavior. Development of tolerance to hypothermia was also inhibited by MK-801. Dopamine D1 antagonist, SCH23390 (0.5 mg x kg(-1)), but not D2 antagonist, sulpiride, inhibited sensitization to and conditioning of climbing behavior. D2 antagonist, sulpiride (50 mg x kg(-1)), but not D1 antagonist, SCH23390, inhibited development of tolerance to hypothermia. These results suggest that MK-801 inhibited contextual sensitization to climbing behavior and development of tolerance to hypothermia through glutamatergic modulation of dopaminergic functions at dopamine receptors.

Animals↗

PubMed2001

Recombinant expression of biologically active rat leptin in Escherichia coli.

Leptin is a 16-kDa nonglycosylated hormone that is produced in mature adipocytes and which acts primarily in the hypothalamus to reduce food intake and body weight. While the rat is a representative laboratory animal model in obesity research, so far recombinant rat leptin was not available. In the present study, rat leptin was recombinantly expressed in Escherichia coli and purified in a bioactive form to provide a further tool for the analysis of leptin functions in rats. Leptin cDNA was cloned by RT-PCR from total RNA of SD rat adipocytes, and overexpression was achieved by subcloning the leptin cDNA into the pET-29a vector, which enabled the recombinant expression of rat leptin as an S-peptide-tagged fusion protein. Since the fusion proteins were expressed in inclusion bodies, after purification of the insoluble fraction, leptin proteins were refolded by sequential dialysis into physiological buffers. The biological activity of this recombinant protein was confirmed in proliferation assays using leptin-sensitive rat insulinoma cells as well as a newly developed leptin-sensitive luciferase assay system. The specific binding of the S-tagged leptin to leptin-receptor-expressing cells was further shown by flow cytometry using fluorescence-conjugated S-proteins.

Adipocytes↗

PubMed2001

Lignan and neolignan glycosides from Ulmus davidiana var. japonica.

Four lignan xylosides and two neolignan glycosides were isolated from the stem and root barks of Ulmus davidiana var. japonica. Their structures were identified as lyoniside, nudiposide, 5'-methoxyisolariciresinol-9'-O-beta-D-xylopyranoside, isolariciresinol-9'-O-1-D-xylopyranoside, rel-trans-dihydrodehydroconiferyl alcohol 4'-O-alpha-L-rhamnopyranoside and icariside E3 by comparison of their spectral data with those reported in the literatures, respectively.

Chromatography, Ion Exchange↗

PubMed2001

Pain after laparoscopic cholecystectomy: the effect and timing of incisional and intraperitoneal bupivacaine.

PURPOSE: To examine the combined preemptive effects of somatovisceral blockade during laparoscopic cholecystectomy (LC). METHODS: One hundred fifty-seven patients under general anesthesia receiving local infiltration and/or topical peritoneal local anesthesia were studied. Patients were randomized to receive a total of 150 mg (0.25% 60 mL) bupivacaine via periportal (20 mL) and intraperitoneal (40 mL with 1:200,000 epinephrine) administration of each. Group A received preoperative periportal bupivacaine before incision and intraperitoneal bupivacaine immediately after the pneumoperitoneum. Group B received periportal and intraperitoneal bupivacaine at the end of the operation. Group C (preoperative) and Group D (postoperative) received only periportal bupivacaine and Group E (preoperative) and Group F (post-operative) received only intraperitoneal bupivacaine. The control group received no treatment. Pain and nausea were recorded at one, two, three, six, nine, 12, 24, 36, and 48 hr postoperatively. RESULTS: Throughout the postoperative 48 hr, incisional somatic pain dominated over other pain localizations in the control group (P <0.05). The incisional pain of groups A, B, C and D was significantly lower than that of the control group in the first and second hours. The incisional pain of groups A and C was significantly lower than that of the control group in the first three hours. CONCLUSION: Incisional pain dominated during the first two post-operative days after LC. Preoperative somato-visceral or somatic local anesthesia reduced incisional pain during the first three post-operative hours. A combination of somato-visceral local anesthetic treatment did not reduce intraabdominal pain, shoulder pain or nausea more than somatic treatment alone. Preoperative incisional infiltration of local anesthetics is recommended.

Adult↗

PubMed2001

Lipid-lowering and antioxidative activities of 3,4-di(OH)-cinnamate and 3,4-di(OH)-hydrocinnamate in cholesterol-fed rats.

BACKGROUND: Polyphenols appear to have antioxidant activities and may mediate lipid lowering. METHODS: Four groups of rats, a high-cholesterol control (HC), HC+lovastatin, HC+3,4-di(OH)-cinnamate, and HC+3,4-di(OH)-hydrocinnamate, were given a semi-synthetic diet. The cinnamate derivative or lovastatin (0.1 g/100 g) supplements were given for 6 weeks. RESULTS: The plasma total cholesterol concentration was significantly lowered by the 3,4-di(OH)-cinnamate supplement compared to the control or lovastatin group. The 3,4-di(OH)-cinnamate and 3,4-di(OH)-hydrocinnamate supplements significantly lowered both the hepatic cholesterol and triglyceride levels, while lovastatin only lowered the hepatic cholesterol. The hepatic HMG-CoA reductase activities were significantly lower in the 3,4-di(OH)-cinnamate and 3,4-di(OH)-hydrocinnamate groups than in the control or lovastatin group. The ACAT activity was only significantly lower in the lovastatin group compared to the other groups. With regards the hepatic antioxidant enzyme system, the CAT activity was significantly higher in the 3,4-di(OH)-cinnamate and 3,4-di(OH)-hydrocinnamate groups compared to the control or lovastatin group. The two cinnamate derivatives resulted in an increased hepatic GSH-Px activity. Meanwhile, all the supplements significantly lowered the hepatic thiobarbituric acid reactive substances (TBARS) content. However, the 3,4-di(OH)-cinnamate and 3,4-di(OH)-hydrocinnamate supplements did not alter the neutral sterol and total fecal sterol. CONCLUSIONS: Both cinnamate derivatives were potent in lipid-lowering and altering the antioxidative enzyme. Furthermore, these results also suggest that 3,4-di(OH)-cinnamate is more effective than 3,4-di(OH)-hydrocinnamate in its lipid-lowering action.

Animals↗

PubMed2001

The effects of dexamethasone on insulin release and biosynthesis are dependent on the dose and duration of treatment.

Complex results concerning the effect of glucocorticoids on insulin secretion have been reported. The aim of this study is to clarify the direct effects of glucocorticoids on pancreatic islets and to determine whether the effect of glucocorticoids on insulin biosynthesis or release is dependent on the dose and duration of treatment with glucocorticoid. Studies on insulin secretion and biosynthesis were performed with different concentrations (0, 1, 10, 100 nmol/l) and durations (1 and 6 h) of treatment with dexamethasone (dexa) in rat pancreatic islets. (1) One nmol/l dexa had no inhibitory effect on insulin secretion and biosynthesis. Ten and 100 nmol/l had an inhibitory effect on insulin secretion, which was mainly due to suppression of the first phase of insulin secretion. (2) Insulin content was significantly increased regardless of the concentration in 1-h treated islets. However, insulin content was markedly diminished with 100 nmol/l dexa in 6-h treated islets. (3) The preproinsulin mRNA expression of 6-h treated islets was suppressed in a dose-dependent manner. Our data revealed that, in the condition of short-term and low-dose glucocorticoid exposure, insulin secretion and biosynthesis are not affected. The secretory process of insulin seems to be the initial step of the inhibitory action of glucocorticoid. Both insulin release and biosynthesis are inhibited by chronic exposure to high dose dexamethasone. It can be concluded that glucocorticoid might be involved in the multisteps of insulin release and biosynthesis.

Animals↗

PubMed2001

Trauma experience of North Korean refugees in China.

OBJECTIVES: We examined trauma experience and mental health conditions among North Korean migrants in China. METHODS: Personal interviews of 170 North Korean "food refugees" in China were conducted in 1999. Structured questionnaires were used to identify specific trauma experience and symptoms of post-traumatic stress, anxiety, and depression. RESULTS: All participants surveyed reported trauma exposure, with food and water shortage (93%) and illness without access to medical care (89%) being the most frequently cited events. Post-traumatic stress disorder was suspected in 56% of the respondents. Above-threshold scores on anxiety and depression were found in 90% and 81% of the cases, respectively. CONCLUSIONS: The burden on the part of North Korean migrants in China who experience trauma appears to be very high. An international call for action is warranted to monitor and safeguard the mental health status of this vulnerable segment of people and respond to their urgent psychiatric and medical care needs.

Adult↗

PubMed2001

Acemannan purified from Aloe vera induces phenotypic and functional maturation of immature dendritic cells.

Acemannan, a major carbohydrate fraction of Aloe vera gel, has been known to have antiviral and antitumoral activities in vivo through activation of immune responses. The present study was set out to define the immunomodulatory activity of acemannan on dendritic cells (DCs), which are the most important accessory cells for the initiation of primary immune responses. Immature DCs were generated from mouse bone marrow (BM) cells by culturing in a medium supplemented with GM-CSF and IL-4, and then stimulated with acemannan, sulfated acemannan, and LPS, respectively. The resultant DCs were examined for phenotypic and functional properties. Phenotypic analysis for the expression of class II MHC molecules and major co-stimulatory molecules such as B7-1, B7-2, CD40 and CD54 confirmed that acemannan could induce maturation of immature DCs. Functional maturation of immature DCs was supported by increased allogeneic mixed lymphocyte reaction (MLR) and IL-12 production. The differentiation-inducing activity of acemannan was almost completely abolished by chemical sulfation. Based on these results, we propose that the adjuvant activity of acemannan is at least in part due to its capacity to promote differentiation of immature DCs.

Adjuvants, Immunologic↗