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Biomedical subjects

D B Lee

Publications and source records attributed to D B Lee.

At least 19 recordsLinked to original sources
PubMed2006

Electrochemical detection of pathogen infection using cell chip.

The immobilized cell using self-assembled synthetic oligopeptide was applied to the electrochemical detection of pathogen infection. Thin films based on cysteine-terminated synthetic oligopeptides were fabricated for the immobilization of HeLa cell on gold (Au) substrate. Layer formation and immobilization of the cell were investigated with surface plasmon resonance (SPR) and electrochemical impedance spectroscopy (EIS). Experimental results showed that the thin film of cysteine-terminated synthetic oligopeptide was successfully fabricated and it could be applied for the immobilization of HeLa cells. The adhered living cell was exposed to E. coli O157:H7, which induced the change of SPR angle and electrochemical impedance signal. The proposed cell immobilization method using self-assembly technique can be applied to construct the cell microarray for on-site pathogen monitoring.

Carcinoma↗
PubMed2003

An inhibitor of IkappaB kinase, BMS-345541, blocks endothelial cell adhesion molecule expression and reduces the severity of dextran sulfate sodium-induced colitis in mice.

OBJECTIVE: Inflammatory bowel diseases such as ulcerative colitis and Crohn's disease are characterized by chronic relapsing inflammation. The transcription of many of the proteins which mediate the pathogenesis in inflammatory bowel disease (e.g., TNFalpha, ICAM-1, VCAM-1) is NF-kappaB-dependent. IkappaB kinase is critical in transducing the signal-inducible activation of NF-kappaB and, therefore, represents a potentially promising target for the development of novel agents to treat inflammatory bowel disease and other inflammatory diseases. RESULTS: Here we show that BMS-345541, a highly selective inhibitor of IkappaB kinase, inhibited the TNFalpha-induced expression of both ICAM-1 and VCAM-1 in human umbilical vein endothelial cells at the same concentration range as cytokine expression is inhibited in monocytic cells (IC(50) congruent with 5 microM). Against dextran sulfate sodium-induced colitis in mice, BMS-345541 administered orally at doses of 30 and 100 mg/kg was effective in blocking both clinical and histological endpoints of inflammation and injury. CONCLUSION: This represents the first example of an inhibitor of IkappaB kinase with anti-inflammatory activity in vivo and indicates that inhibitors of IkB kinase show the promise of being highly efficacious in inflammatory disorders such as inflammatory bowel disease.

Animals↗
PubMed1998

Erythropoietin upregulates angiotensin receptors in cultured rat vascular smooth muscle cells.

OBJECTIVE: Plasma renin is not elevated in recombinant human erythropoietin (rhEPO)-induced hypertension but angiotensin converting enzyme inhibitors reduce blood pressure in both human and animal studies. Since rhEPO elevates renin and angiotensinogen messenger RNAs in angiotensin II target tissues such as the aorta, we explored the actions of rhEPO on renin-angiotensin system-related gene transcription of cultured rat vascular smooth muscle cells. DESIGN AND METHODS: To separate direct actions of rhEPO from those mediated secondarily by potential activation of the renin-angiotensin system, vascular smooth muscle cells were cultured with rhEPO and enalapril to inhibit the angiotensin converting enzyme and losartan to inhibit angiotensin II type 1 receptors. RESULTS: Vascular smooth muscle cells cultured with rhEPO (6-8 units/ml) demonstrated elevations (40-120%) in messenger RNAs of the renin-angiotensin system (renin, angiotensinogen, angiotensin receptor types 1 and 2) and increased levels of several messenger RNAs known to respond to angiotensin II (transforming growth factor-beta, insulin-like growth factor-II, epidermal growth factor, c-fos and platelet-derived growth factor). In contrast, cells cultured in the presence of rhEPO and enalapril or losartan showed elevations of messenger RNA for only the two types of angiotensin II receptor. This increase was higher than that obtained when cells were cultured with rhEPO or either antagonist alone. The increase in specific binding of angiotensin II to cells cultured in the presence of rhEPO and enalapril or rhEPO and losartan paralleled the changes in receptor messenger RNA. CONCLUSIONS: rhEPO exerts its primary action on vascular smooth muscle cells via an increase in angiotensin receptor messenger RNA, resulting in a parallel increase in angiotensin II receptor expression. We suggest that increased receptor expression secondarily mediates the expression of other renin-angiotensin system messenger RNAs, which leads to angiotensin II-responsive gene transcription. The elevation in angiotensin II receptors, as observed in response to rhEPO, may provide a mechanism by which other forms of renin-dependent hypertension are initiated.

Animals↗
PubMed1998

Variants of N-acetyltransferase NAT1 and a case-control study of colorectal adenomas.

N-acetyltransferase NAT1, together with enzymes CYP1A2 and NAT2, helps convert heterocyclic amines to mutagens. Epidemiologic studies of the association of variants of these enzymes with colorectal cancer may provide indirect support for a heterocyclic amine mechanism. We used single strand conformation polymorphism and heteroduplex analysis to screen fro mutations in the NAT1 coding region in a case-control study (n = 932) of colorectal adenomas, which are precursors to cancer. Thirteen different single-base mutations were found: C97T, C190T, T402C, G445A-G459A-T640G ( a combination of three mutations), C559T, G560A, A613G, A752T, T777C, G781A, and A787G. Function of novel mutations was tested by bacterial production of enzymes and measurements of Km, Vmax, and stability. However, on 24-control individuals and 18 cases carried an inactivating NAT1 mutation. When combined with our data on the NAT2 acetylation polymorphism, we saw no evidence for an association between N-acetyltransferases and prevalence of adenomas. Larger sample sizes are required for further evaluation.

Acetyltransferases↗
PubMed1998

Prevalence and disease experience rates in Korean physicians.

This study aimed to find out the morbid status of Korean physicians living in Korea, as one part of a feasibility study on the Korean physician cohort. It was performed by mail survey using a self-administered questionnaire from Jan. 1, 1995 through Dec. 31, 1995. Study subjects were 21,552 including 17,877 (81.1%) males and 3,384 (15.5%) females. Person based prevalence rate of disease was 17.7% (18.3% for males and 13.8% for females) with the rate increasing with age. The disease group showing the highest prevalence rate was circulatory diseases (5.16%) for males, and respiratory disease (3.13%) for females. The individual disease showing the highest prevalence rates was hypertension (3.77%) for males and allergic rhinitis (2.25%) for females. The person based disease experience rate was 36.2% (36.9% for males, 32.7% for females) with the rate increasing with age. The disease group showing the highest disease experience rate was digestive disease for both sexes (10.05% for males, 7.42% for females). Individual disease showing the highest disease experience rate was hypertension (5.00%) for males and allergic rhinitis (4.08%) for females. There were different ranks of both prevalence and disease experience rate depending on age in both sexes.

Adult↗
PubMed1997

Prognostic significance of chemotherapy dosage characteristics in children with osteogenic sarcoma.

High-dose methotrexate (HDMTX), adriamycin (ADR), and cisplatinum (CDDP) are effective agents in the treatment of osteogenic sarcoma (OS). Individual patient doses are determined by prior successful clinical trials but may be reduced due to ongoing toxicities. It is unknown whether individualized dose reductions of these drugs influence disease outcome. We retrospectively studied 27 consecutively enrolled children treated with HDMTX, ADR, and CDDP as adjuvant chemotherapy for OS, for correlations between disease outcome and several characteristics of drug dosings the cumulative MTX, CDDP, and ADR doses administered and the mean MTX blood levels for each patient. With a median follow-up of 59 months, the actuarial overall and disease-free survival rates were 70% and 59%, respectively. Factors which favorably influenced prognosis on univariate analysis were a cumulative ADR dose of > 300 mg/m2 (P = 0.0002) and a cumulative MTX dose > 114 gm/m2 (P = 0.0048). By multivariate analysis only the cumulative ADR dose > 300 mg/m2 retained prognostic value. We conclude that adjuvant chemotherapy dosages may need to be adjusted for therapeutic efficacy in addition to adjustments made for toxicity. The effect of different cumulative HDMTX and ADR dosages on prognosis in osteosarcoma patients needs to be evaluated in a prospective trial.

Adolescent↗
PubMed1997

Paracellular phosphate absorption in rat colon: a mechanism for enema-induced hyperphosphatemia.

The mechanism of colonic phosphate absorption is not well defined. We measured unidirectional phosphate fluxes across rat distal colon epithelium in the absence of transepithelial electrochemical gradients. Steady-state mucosal-to-serosal flux (Jms) was not different from the serosal-to-mucosal flux (Jsm), generating no net flux (Jnet = Jms - Jsm, was not different from "0'). Simultaneous fluxes of mannitol, a paracellular probe, exhibited an identical flux pattern, suggesting that phosphate flux across the colonic epithelium may be mediated through the paracellular pathway. Tight junction permeability was increased with mucosal addition of taurodeoxycholate (TDC, 2 mM) which caused a prompt increase in transepithelial conductance from 7.03 +/- 0.35 to 13.88 +/- 0.35 mS/cm2 (p < 0.001). This was associated with an increase in Jsm, but no change in Jms, for mannitol, resulting in a net flux in the secretary direction. Identical TDC-induced changes were observed in phosphate fluxes, again suggesting phosphate permeation through the intercellular, mannitol pathway. A significant correlation was observed between the permeability of phosphate and the permeability of mannitol, measured both in the mucosal-to-serosal and the serosal-to-mucosal directions and under both control and experimental (mucosal TDC) conditions. Thus, colonic phosphate transport is mediated through the paracellular pathway and enema with high phosphate concentrations (1,760 times blood concentration), can trigger rapid and massive phosphate absorption through this diffusive pathway.

Animals↗
PubMed1995

Angiotensin-converting enzyme inhibition in the treatment of renal transplant erythrocytosis. Clinical experience and observation of mechanism.

Recent observations indicate that angiotensin-converting enzyme (ACE) inhibition corrects renal transplant erythrocytosis (RTE). The mechanism for this association is not known. We examined the effect of ACE inhibition on hematocrit, erythropoietin (EPO), and renin substrate. ACE inhibition has been reported to suppress renin substrate, which is known to stimulate EPO and erythropoiesis. In 15 patients with RTE, hematocrit dropped from 52.8 +/- 0.6 (SEM) to 45.8 +/- 1.4% after 8 weeks of treatment with Enalapril, 2.5-20 mg/day. Serum EPO (normal range: 9-30 mU/ml) was high in one, normal in seven, and low in seven patients. ACE inhibition reduced EPO in patients with initial high or normal levels but induced no change in patients with initial low levels. ACE inhibition had no significant effect on renin substrate. In one patient who rejected his first graft, erythrocytosis recurred following a second, successful transplant. Treatment was discontinued because of cough in two patients and symptomatic drop in blood pressure in one patient. We conclude RTE is not caused by hypererythropoietinemia. In patients with normal circulating EPO, erythrocytosis may result from an increase sensitivity to EPO, and ACE inhibition lowered hematocrit by further reduction of this hormone. However, the finding of erythrocytosis in half our patients with suppressed EPO, suggests the participation of non-EPO-mediated mechanism(s). The recurrence of RTE in a patient after a second transplant raises the additional possibility of patient-specific factors in the pathogenesis of this disorder. In contrast to other reports, we documented side-effects (cough, hypotension) in three (20%) of our patients. Our clinical experience, coupled with prior reports of spontaneous resolution of RTE in some patients, suggests that intermittent courses of ACE-inhibition may be the optimal strategy in the use of this form of therapy for RTE.

Adult↗
PubMed1995

Acetylation polymorphism and prevalence of colorectal adenomas.

Polymorphic N-acetyltransferase (NAT2), an enzyme present in the colon, may effect incidence of colon cancer. Individuals with NAT2 fast acetylator genotypes may have higher colon cancer risks due to faster conversion of certain carcinogens to mutagens. We determined NAT2 genotypes in 447 subjects with distal colon adenomas and in 487 controls. No significant increase in adenoma prevalence among fast acetylators was observed. However, there was a suggestion of ethnic differences in NAT2 effects. For example, white fast acetylators potentially had slightly increased risks for adenomas (odds ratio, 1.29; 95% confidence interval, 0.90-1.84), whereas fast acetylation was potentially protective among blacks (odds ratio, 0.64; 95% confidence interval, 0.32-1.28). The apparent difference between blacks and whites may simply reflect random variation around an overall null effect, or it could represent a real difference. There was preliminary evidence for a possible interaction between NAT2 and the glutathione transferase M1 null genotype. Smokers' adenoma prevalence was 10-fold higher for fast acetylators with the null genotype compared to slow acetylators without the null genotype. Large, multiethnic populations and analysis of combinations of genes for carcinogen metabolism may be needed to further assess the role of NAT2 in colorectal tumorigenesis.

Acetylation↗
PubMed1995

Glutathione transferase (GSTM1) null genotype, smoking, and prevalence of colorectal adenomas.

Colorectal cancer is caused by environmental exposures and genetic predisposition. However, little is known of hereditary factors that influence development of common, non-Mendelian forms of this cancer. Interactions among carcinogen exposure, hereditary variants of enzymes involved in carcinogen metabolism, and other host factors may play a role. Genetic polymorphisms of carcinogen metabolism, such as the glutathione transferase M1 (GSTM1) null genotype, are thus possibly related to cancer risk. The GSTM1 enzyme detoxifies mutagens formed from polycyclic aromatic hydrocarbons which are found in tobacco smoke. We analyzed GSTM1 genotypes and smoking among 488 controls and 446 individuals with a first time diagnosis of colorectal adenomas which are precursors to cancer. Subjects were from two Kaiser Permanente sigmoidoscopy clinics in southern California. We observed no overall effect of the GSTM1 null genotype on the risk for colorectal adenomas (odds ratio, 0.85; 95% confidence interval = 0.65-1.10). The odds ratio for smokers with the null genotype was 2.07 (95% confidence interval = 1.14-3.77) when compared to "never smokers" without the null genotype. Using this same reference group, the odds ratio for smokers without the null genotype was 1.73 (95% confidence interval = 1.03-2.90). These two odds ratios were not significantly different (P = 0.30).

Adenoma↗
PubMed1995

Parathyroid hormone-induced retraction of MC3T3-E1 osteoblastic cells is attenuated by the calpain inhibitor N-Ac-Leu-Leu-norleucinal.

Parathyroid hormone (PTH) binding to its osteoblastic receptors stimulates cytoplasmic retraction within minutes. We hypothesized that the calpains (calcium-activated papain-like enzymes) contribute to PTH-induced osteoblastic retraction by catalyzing regulatory hydrolysis of cytoskeletal structural proteins or enzymes important in cytokinesis. N-Ac-Leu-Leu-norleucinal (ALLN), a reversible calpain inhibitor, was tested for its ability to inhibit PTH-induced retraction in murine MC3T3-E1 osteoblastic cells. ALLN inhibited PTH-induced retraction for 30 minutes in cells cultured on polystyrene cultureware or gelatin-coated glass cover slips, supporting the hypothesis that PTH-induced activation of the calpains contributes to short-term changes in MC3T3-E1 cell shape. Inhibition of PTH-induced retraction occurred on two substrata, suggesting that interactions between the extracellular matrix and cell surface proteins are not the sole determinants of morphology. Intracellular events, such as hydrolysis of focal adherens junction proteins on the cytoplasmic face of the plasma membrane, may contribute to PTH-induced retraction.

Animals↗
PubMed1995

PTH-mediated osteoblast retraction: possible participation of the calpain pathway.

Parathyroid hormone (PTH)-induced osteoblast retraction may play a pivotal role a role in bone resorption by providing osteoclasts direct access to mineralized bone surface. We have been working on the hypothesis that the calpains participate in this retractile response through a calcium-dependent process. We have first demonstrated the presence of calpain activities in MC3T3-E1 osteoblastic cells and that these activities can be stimulated by PTH. Second, we have demonstrated that the PTH-induced osteoblast retraction is dramatically attenuated by two different cysteine protease inhibitors. Finally, initial immunofluorescent cytochemical studies suggest that this PTH-induced osteoblastic retraction is mediated through a calpain-dependent, proteolytic modification of the cytoskeletal organization.

Amino Acid Sequence↗
PubMed1994

PTH and PTH-rP elicit dissimilar retractile responses in murine MC3T3-E1 osteoblasts.

Parathyroid hormone (PTH) and PTH-related peptide (PTH-rP) bind to a common receptor and initiate second-messenger cascades that stimulate bone turnover and hypercalcemia. However, PTH is more potent than PTH-rP in inducing bone resorption and coupled bone metabolism in intact tissue, suggesting that these proteins elicit dissimilar postreceptor responses. We compared the effects of PTH and PTH-rP on osteoblastic retraction, an early event that must occur before the osteoclast can achieve access to the underlying bone mineral and begin resorption. MC3T3-E1 mouse osteoblasts were incubated in vehicle or 4.8 nM PTH or PTH-rP with or without 1 mM dibutyryl cAMP (Bt2cAMP). Morphologic changes were observed from 0 to 120 min. PTH caused marked retraction within minutes, which was not enhanced by Bt2cAMP. PTH-rP or Bt2cAMP induced slower, more modest retraction than PTH. The combined effect of PTH-rP plus Bt2cAMP was greater than that of PTH-rP, but less than that of PTH. PTH-rP and PTH had similar effects on cAMP generation. Thus, compared to PTH, PTH-rP induces less osteoblastic retractile response, exposing less bone surface to osteoclastic resorption. This may account for its lower hypercalcemic potency in vivo and contribute to its relative inability to stimulate coupled bone resorption and formation.

Animals↗
PubMed1993

IFN-alpha induces homotypic adhesion and Leu-13 expression in human B lymphoid cells.

IFN-alpha influences the recirculation and growth of normal and malignant B lymphocytes, although the mechanisms involved are not currently known. Lymphocyte recirculation is fundamentally dependent on cell-to-cell interactions that are mediated by cell surface adhesion molecules. In this report, we examined the relationship between the effect of IFN-alpha on cell-to-cell adhesion processes and induction of the Leu-13 cell surface protein in established human Daudi B lymphoid cell lines that are either sensitive or resistant to the antiproliferative activity of IFN-alpha. IFN-alpha directly triggered homotypic adhesion of IFN-sensitive Daudi B cells in a time- and dose-dependent manner. In contrast, IFN-alpha had no effect on the cell-to-cell adhesion of IFN-resistant Daudi B cells. The capacity of IFN-alpha to trigger homotypic aggregation correlated directly with the level of induction of the cell surface protein Leu-13 and could be potentiated by anti-Leu-13 mAb. Other cytokines also known to influence the proliferation, differentiation, or recirculation of B lymphocytes such as IFN-gamma, IL-2, IL-4, IL-6, TNF-alpha, and low molecular weight B cell growth factor did not induce either Leu-13 expression or homotypic aggregation of Daudi B cells. The adhesion pathway triggered by the IFN-inducible protein Leu-13 required metabolic energy and an intact cytoskeleton but was not dependent on: 1) new protein synthesis; 2) protein kinase C, protein kinase A, or tyrosine kinase activities; or 3) the function of known adhesion molecules including LFA-1, ICAM-1, CD44, or VLA-4. Taken together, these studies demonstrate a fundamental role for IFN-alpha and the IFN-inducible protein Leu-13 in regulating a novel homotypic adhesion pathway in B lymphocytes, and provide insight into the possible mechanisms by which IFN-alpha regulates biologic processes including recirculation.

Antibodies, Monoclonal↗
PubMed1993

PTH-induced osteoblast contraction is mediated by cysteine proteases.

E-64d, a membrane-permeable cysteine protease inhibitor, was tested for its ability to inhibit PTH-induced contraction in intact mouse MC-3T3-E1 osteoblastic cells. Incubation of MC-3T3-E1 cells with vehicle (DMSO) or E-64c, a nonpermeant cysteine protease inhibitor, in the presence or in the absence of PTH had no effects on cAMP production or on morphology from 0 to 90 minutes after addition. In contrast, treatment with E-64d markedly attenuated PTH-induced contraction in these cells. These findings suggest that cysteine proteases, such as the calcium-activated neutral proteases (calpains), are involved in PTH-induced osteoblastic contraction. The observation that cysteine protease activity mediates PTH-induced osteoblastic contraction also suggests that endogenous inhibitors, such as calpastatin, may also be present in the osteoblast and play a role in the regulation of stimulus-response coupling in bone. This mechanism may provide another regulatory point at which bone cells may be pharmacologically manipulated in clinical situations characterized by excessive bone resorption.

Animals↗
PubMed1993

Bile salts and ileal calcium transport in rats: a neglected factor in intestinal calcium absorption.

Ileum displays little active transcellular calcium (Ca2+) absorption but is credited with the bulk of Ca2+ absorbed in vivo. We examined the effect of taurodeoxycholic acid (TDC, 2 mM), a bile salt, on mannitol (MN, a marker of intercellular solute traffic) and Ca2+ fluxes in rat ileum. In the absence of electrochemical gradients between the mucosal (M) and serosal (S) bathing media in an Ussing chamber, net flux (Jnet) was observed in the S-to-M direction for both MN and Ca2+, i.e., the unidirectional secretory S-to-M flux (Js-->m) exceeded the absorptive M-to-S flux (Jm-->s). Mucosal TDC caused simultaneous increase in transepithelial conductance and Js-->m for both MN and Ca2+. This was followed by even greater increases in MN and Ca2+ Jm-->s, so that ultimately Jm-->s equaled Js-->m in each case. In control tissue, Js-->m for Ca2+ appeared to permeate exclusively through the intercellular MN pathway while part of Jm-->s for Ca2+ appeared to traverse through a non-MN route. After the TDC-induced increase in intercellular solute permeability, both Ca2+ fluxes appeared to traverse through the aqueous MN conduit. During the postprandial state, the presence of bile salts and the relative abundance of Ca2+ in ileal lumen can cause bulk Ca2+ absorption through the intercellular pathway.

Absorption↗
PubMed1993

Analysis of segmental phosphate absorption in intact rats. A compartmental analysis approach.

Available information supports the dominance of the proximal intestine in inorganic phosphate (Pi) absorption. However, there is no strategy for analyzing segmental Pi absorption from a spontaneously propelled meal in an intact animal. We propose a solution using compartmental analysis. After intragastric administration of a 32P-labeled Pi liquid meal containing a nonabsorbable marker, [14C]polyethylene glycol (PEG), rats were killed at 2, 10, 20, 30, 60, 120, and 240 min. The gastrointestinal tract was removed and divided into seven segments, from which 32P and [14C]PEG were recovered. Data was expressed as a percentage of the dose fed, i.e., (32P[in segment] divided by 32P[fed]) and [14C]PEG[in segment] divided by [14C]PEG[fed]), respectively. A compartmental model was constructed and the rate constants for intersegmental transit and segmental absorption were estimated. The "goodness of fit" between the simulated model and the actual data indicates the estimated rate constants reflect in vivo events. The duodenum, with the highest transit and absorption rates, accounted for a third of the total absorption. However, the terminal ileum, with a lower absorption rate but a longer transit time, absorbed an equal amount of Pi. This approach allows the analysis of the mechanism and the regulation of Pi absorption under more authentic in vivo conditions.

Animals↗