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Biomedical subjects

B S Lee

Publications and source records attributed to B S Lee.

At least 37 records · Page 2Linked to original sources
PubMed2001

Inducible macrolide resistance in Corynebacterium jeikeium.

Corynebacterium jeikeium is an opportunistic pathogen primarily of immunocompromised (neutropenic) patients. Broad-spectrum resistance to antimicrobial agents is a common feature of C. jeikeium clinical isolates. We studied the profiles of susceptibility of 20 clinical strains of C. jeikeium to a range of antimicrobial agents. The strains were separated into two groups depending on the susceptibility to erythromycin (ERY), with one group (17 strains) representing resistant organisms (MIC > 128 microg/ml) and the second group (3 strains) representing susceptible organisms (MIC < or = 0.25 microg/ml). The ERY resistance crossed to other members of the macrolide-lincosamide-streptogramin B (MLSb) group. Furthermore, this resistance was inducible with MLSb agents but not non-MLSb agents. Expression of ERY resistance was linked to the presence of an allele of the class X erm genes, erm(X)cj, with >93% identity to other erm genes of this class. Our evidence indicates that erm(X)cj is integrated within the chromosome, which contrasts with previous reports for the plasmid-associated erm(X) genes found in C. diphtheriae and C. xerosis. In 40% of C. jeikeium strains, erm(X)cj is present within the transposon, Tn5432. However, in the remaining strains, the components of Tn5432 (i.e., the erm and transposase genes) have separated within the chromosome. The rearrangement of Tn5432 leads to the possibility that the other drug resistance genes have become included in a new composite transposon bound by the IS1249 elements.

Amino Acid Sequence↗
PubMed2001

Human leiomyoma smooth muscle cells show increased expression of transforming growth factor-beta 3 (TGF beta 3) and altered responses to the antiproliferative effects of TGF beta.

Transforming growth factor-betas (TGF betas) are multifunctional peptides that regulate growth and differentiation in a variety of cells. The goals of this study were to compare expression of the TGF beta isoforms in normal myometrium and benign leiomyoma tumors of the uterus and to examine the effects of TGF betas on cell proliferation and collagen production by these cells in vitro. Myometrium and leiomyoma tissues were obtained from patients undergoing elective hysterectomies. Tissues were processed for ribonucleic acid (RNA) and were also established as primary cell cultures. Northern blot analysis showed that the levels of TGF beta 1 messenger RNAs (mRNAs) were similar between leiomyoma and myometrium, whereas leiomyoma showed 5-fold higher levels of expression of TGF beta 3 mRNA than autologous myometrium. Expression of TGF beta 3 protein detected by immunohistochemistry was much more intense in leiomyoma tissues than in corresponding myometrium. Levels of both TGF beta 1 and TGF beta 3 increased with increasing cell density for leiomyoma and myometrium smooth muscle cells cultured in vitro. Effects of TGF beta 1 and TGF beta 3 on cell proliferation were assessed by measuring changes in DNA synthesis with the tritiated thymidine incorporation assay. The doses of TGF betas tested were 0, 0.1, 1.0, and 10.0 ng/mL. All three doses of TGF beta 1 and TGF beta 3 inhibited DNA synthesis in myometrium smooth muscle cells by 31--54%. Concomitant treatment with an immunoneutralizing antibody to TGF beta 1--3 reversed this inhibitory effect. In contrast, TGF beta 1 had no effect on leiomyoma smooth muscle cells, whereas TGF beta 3 increased DNA synthesis by leiomyoma cells. Combined treatment with the immunoneutralizing antibody prevented this increase. Treatment of leiomyoma and myometrial cells with the TGF beta immunoneutralizing antibody for 24 h caused a 45--60% reduction in collagen type I and type III mRNA levels, suggesting that endogenous TGF betas are important for collagen production. These results support the hypothesis that alterations in the TGF beta system produce loss of sensitivity to the antiproliferative effects of TGF beta, and increased expression of TGF beta 3 may contribute to the growth of these tumors.

Cell Division↗
PubMed2001

Is cholecystectomy necessary after ERCP for bile duct stones in patients with gallbladder in situ?

BACKGROUND: The requirement for subsequent cholecystectomy in patients with gallbladder in situ after endoscopic removal of stones from the common bile duct (CBD) is controversial. The aims of this study were to assess the requirement for subsequent cholecystectomy for gallbladder-related symptoms, and to identify the patients who develop symptoms after the endoscopic removal of CBD stones. METHODS: Of 241 patients with gallbladder in situ following endoscopic removal of stones from the CBD, 146 patients (78 men and 68 women; mean age 69 +/- 13 years, range 20-93) with a follow-up time of more than three months without elective cholecystectomy were enrolled in the study. Fifty-nine patients had gallbladder stones (single stones in 27 and multiple stones in 32) and 87 patients had gallbladder in situ without stones. The time from entry to the occurrences of death or cholecystectomy was evaluated retrospectively. Cox regression analysis was used to evaluate the risk factors associated with these events. RESULTS: The mean duration of follow-up was 24.1 +/- 18.0 months (range 3-70 months). During follow-up, seven patients (4.8%) underwent cholecystectomy, on average 18.4 months after CBD stone removal, as the result of acute cholecystitis in four cases, biliary pain in two cases and acute pancreatitis in one case. Laparoscopic cholecystectomy was performed in four patients and open cholecystectomy in three patients. Post-operative morbidity occurred in two patients, with improvement after conservative management. Nine patients (6.2%) died as the result of unrelated biliary disease. Age, sex, presence of gallbladder stones, multiplicity of gallbladder stones and underlying disease did not correlate with subsequent cholecystectomy by Cox regression analysis. CONCLUSION: Elective cholecystectomy is not warranted in patients with bile duct stones when the common duct can be cleared of stones by endoscopic sphincterotomy. We could not find any clinical predictors of further symptoms or complications arising from the retained gallbladder.

Adult↗
PubMed2001

Modulation of N-type Ca2+ currents by A1-adenosine receptor activation in male rat pelvic ganglion neurons.

Modulation of voltage-activated Ca2+ channels by adenosine was investigated in male rat major pelvic ganglion (MPG) neurons by using the whole-cell variant of the patch-clamp technique. Adenosine inhibited high voltage-activated (HVA) Ca2+ currents in a concentration-dependent manner with an EC50 of 313 nM and a maximal inhibition of 36%, respectively. Inhibition of HVA Ca2+ currents in adrenergic and cholinergic MPG neurons was similar. Adenosine did not modulate T-type Ca2+ channels present in adrenergic MPG neurons. Reverse transcription-polymerase chain reaction analysis indicated that MPG neurons express mRNAs encoding A1 and A2a receptors. Ca2+ current inhibition by adenosine was mimicked by N6-cyclopentyladenosine, an A1-selective agonist (EC50 = 63 nM) and prevented by 100 nM 8-cyclopentyl-1,3-dipropylxanthine, an A1-selective antagonist. Conversely, CGS 21680, an A2a-selective agonist, displayed a relatively low potency (EC50 = 2200 nM) for inhibiting Ca2+ currents. The action of adenosine was significantly attenuated by 2 mM guanosine-5'-thiodiphosphate or 500 ng/ml pertussis toxin. The voltage dependence of adenosine-induced current inhibition was evident by 1) a bell-shaped profile between the current inhibition and test potentials, 2) kinetic slowing in the presence of agonist, and 3) relief of the current inhibition by a conditioning prepulse to +80 mV. Finally, 1 microM omega-conotoxin GVIA occluded adenosine-induced current inhibition. Taken together, we concluded that adenosine inhibits N-type Ca2+ currents by activation of A1 receptors via a voltage-dependent and PTX-sensitive pathway in rat MPG neurons. Our data may explain how adenosine acts as an inhibitory modulator of ganglionic and neuromuscular transmission in the pelvic plexus.

Adrenergic Fibers↗
PubMed2000

Beta-poly(L-malate) production by non-growing microplasmodia of Physarum polycephalum. Effects of metabolic intermediates and inhibitors.

The production of beta-poly(L-malate) (PMLA) by non-growing microplasmodia of Physarum polycephalum was investigated. Growth was minimal in culture medium devoid of nitrogen source, but PMLA production occurred at a substantial rate. The addition of metabolic intermediates, malate, fumarate, succinate, and oxaloacetate, and the omission of hematin showed considerable growth inhibition in the presence of the nitrogen source, while PMLA production per unit biomass increased significantly. The results indicated that PMLA production was dissociated from biomass production under these conditions. The stimulating effect of carbonate on PMLA production was independent on growth. Cultivation in the absence of the nitrogen source and hematin or in the presence of the metabolites may be a useful technique for efficient PMLA production at a minimum of biomass production.

Animals↗
PubMed2000

The amino-terminal domain of the B subunit of vacuolar H+-ATPase contains a filamentous actin binding site.

Vacuolar H(+)-ATPase (V-ATPase) binds actin filaments with high affinity (K(d) = 55 nm; Lee, B. S., Gluck, S. L., and Holliday, L. S. (1999) J. Biol. Chem. 274, 29164-29171). We have proposed that this interaction is an important mechanism controlling transport of V-ATPase from the cytoplasm to the plasma membrane of osteoclasts. Here we show that both the B1 (kidney) and B2 (brain) isoforms of the B subunit of V-ATPase contain a microfilament binding site in their amino-terminal domain. In pelleting assays containing actin filaments and partially disrupted V-ATPase, B subunits were found in greater abundance in actin pellets than were other V-ATPase subunits, suggesting that the B subunit contained an F-actin binding site. In overlay assays, biotinylated actin filaments also bound to the B subunit. A fusion protein containing the amino-terminal half of B1 subunit bound actin filaments tightly, but fusion proteins containing the carboxyl-terminal half of B1 subunit, or the full-length E subunit, did not bind F-actin. Fusion proteins containing the amino-terminal 106 amino acids of the B1 isoform or the amino-terminal 112 amino acids of the B2 isoform bound filamentous actin with K(d) values of 130 and 190 nm, respectively, and approached saturation at 1 mol of fusion protein/mol of filamentous actin. The B1 and B2 amino-terminal fusion proteins competed with V-ATPase for binding to filamentous actin. In summary, binding sites for F-actin are present in the amino-terminal domains of both isoforms of the B subunit, and likely are responsible for the interaction between V-ATPase and actin filaments in vivo.

Actin Cytoskeleton↗
PubMed2000

Inhibition of intracellular transport of B cell antigen receptor complexes by Kaposi's sarcoma-associated herpesvirus K1.

The B cell antigen receptor (BCR) is a large complex that consists of a disulfide-linked tetramer of two transmembrane heavy (mu) chains and two light (lambda or kappa) chains in association with a heterodimer of Igalpha and Igbeta. Kaposi's sarcoma-associated herpesvirus (KSHV) encodes a transforming protein called K1, which has structural and functional similarity to Igalpha and Igbeta. We demonstrate that K1 downregulates the expression of BCR complexes on the surface. The NH(2)-terminal region of K1 specifically interacts with the mu chains of BCR complexes, and this interaction retains BCR complexes in the endoplasmic reticulum, preventing their intracellular transport to the cell surface. Thus, KSHV K1 resembles Igalpha and Igbeta in its ability to induce signaling and to interact with mu chains of the BCR. However, unlike Igalpha and Igbeta, which interact with mu chains to direct BCR complexes to the cell surface, K1 interacts with mu chains to block the intracellular transport of BCR complexes to the cell surface. These results demonstrate a unique feature of the K1 transforming protein, which may confer virus-infected cells with a long-term survival advantage.

Binding Sites↗
PubMed2000

Effects of Nd:YAG laser irradiation on cultured human gingival fibroblasts.

BACKGROUND AND OBJECTIVE: The Nd:YAG laser has been proposed to apply in minor soft tissue surgery, including various periodontal procedures. However, little information is available regarding the direct effect of Nd:YAG laser on gingival fibroblasts, which play an important role in the early healing processes of periodontal repair. STUDY DESIGN/MATERIALS AND METHODS: Nd:YAG laser irradiation was performed in pulsed mode on human gingival fibroblasts, which was derived from healthy human gingiva by an explant method. The size of laser diode was 400 microm in diameter. The parameters in laser delivery were pulse energy (50-150 mJ), power output (1.0-3.0 W), pulse rate (10-30 pps), and fixed duration of irradiation (10 seconds). The cell cultures were analysed by cytomorphologic examination under phase-contrast and scanning electron microscope. The vitality was also examined with the help of MTT staining. RESULTS: The area of laser damage on cell culture was circular in shape, with diameter beyond the size of laser diode. By scanning electron microscopy, we observed the cellular damage of cultured gingival fibroblasts induced by Nd:YAG laser irradiation, comparable with the progressive increased power settings. The cytomorphologic changes ranged from disappearance of cellular boundary, loss of identifiable cellular nucleus, and finally cell contraction and vacuolization. Significant decrease in cellular vitality (14% approximately 44%) after laser treatment with irradiation distance of nearly contact was noted. However, 2 mm defocusing irradiation with the same power settings did not significantly decrease cellular vitality. CONCLUSION: Our study demonstrated the cell damaging effects of Nd:YAG laser, ranging from degeneratively cytomorphologic change to cell death, on the cultured human gingival fibroblasts. It provided the dentist a chance to understand the potential hazard of laser application in periodontal treatment. If the energy output is enough for the clinical purposes, Nd:YAG laser with lower pulse energy and corresponding pulse rate should be selected to minimize the damage on adjacent soft tissue.

Cell Survival↗
PubMed2000

Sarcoplasmic reticulum Ca(2+)ATPase and cell contraction in developing rabbit heart.

The purpose of the present study was to determine whether age-related changes in the expression and function of the cardiac isoform of the sarcoplasmic reticulum Ca(2+)-ATPase (SERCA2a) play a role in SR Ca(2+)release and cell contraction. SERCA2a protein levels and subcellular localization were compared between fetal, neonatal, juvenile and adult New Zealand White rabbits. Studies of SERCA function in isolated myocytes were performed in situ by examining the rate of reloading of the SR Ca(2+)stores following caffeine-induced depletion. We found that significant quantities of SERCA2a were present early in immature heart and that SERCA2a expression reached adult levels within 15-30 days after birth. Furthermore, SERCA2a protein is present as a series of transverse striations within the cell as early as 1 day of age. In contrast to previous studies of SERCA in vitro, the SERCA protein function in situ was found to be comparable between neonatal and adult myocytes in maintaining SR Ca(2+)stores. These results indicate that the paucity of SR Ca(2+)release in immature ventricular cardiac myocytes is not the result of immaturity in SERCA2a expression.

Age Factors↗
PubMed2000

Implementation of an emergency department triage procedure for the detection and isolation of patients with active pulmonary tuberculosis.

STUDY OBJECTIVES: To investigate the ability of an emergency department screening protocol to initiate respiratory isolation of patients with pulmonary tuberculosis at ED triage before chest radiography. METHODS: We conducted a prospective cohort study with retrospective medical record review of adult patients who presented for care to an urban, university-affiliated hospital in Los Angeles County over a 4-month period. Ambulatory patients were administered a triage screening protocol that used patient-reported tuberculosis risk factors and symptoms in combination with selective chest radiography to screen patients at ED triage for active pulmonary tuberculosis. RESULTS: A total of 10,674 patients were screened; 2, 218 were isolated at triage and underwent chest radiography, and 378 were kept in isolation in the ED. The respiratory isolation of pulmonary tuberculosis (RIPT) protocol detected 17 of 27 visits made by patients with unsuspected pulmonary tuberculosis, yielding a sensitivity of 63% (95% confidence interval [CI] 42% to 81%). The estimated specificity was 78%. For each patient with tuberculosis who was detected by the RIPT protocol, 624 patients were screened at triage, 130 chest radiographs were taken, and 22 patients were placed in respiratory isolation in the ED. Patients with undetected pulmonary tuberculosis more commonly had nonpulmonary chief complaints (76% versus 20%; odds ratio [OR] 13, 95% CI 2.1 to 78.3), and only 60% (95% CI 26% to 88%) were ultimately isolated in the hospital. Among RIPT screen-positive patients, radiographic findings predictive of pulmonary tuberculosis were cavitary lesions (OR 84.3, 95% CI 22.6 to 315), upper lobe infiltrates (OR 24.2, 95% CI 9.1 to 64.4), pleural effusions (OR 8.9, 95% CI 2.5 to 31.8), diffuse/interstitial infiltrates (OR 5.7, 95% CI 1.8 to 17.9), and non-upper lobe infiltrates (OR 3.1, 95% CI 1.0 to 9.5). CONCLUSION: The RIPT screening protocol was only moderately sensitive for isolating patients with pulmonary tuberculosis at ED triage. Future studies should evaluate modified and abridged screening protocols, as well as the cost-effectiveness of triage screening.

Adult↗
PubMed2000

Inhibition of natural killer cell-mediated cytotoxicity by Kaposi's sarcoma-associated herpesvirus K5 protein.

Kaposi's sarcoma-associated herpesvirus (KSHV) K3 and K5 proteins dramatically downregulate MHC class I molecules. However, although MHC class I downregulation may protect KSHV-infected cells from cytotoxic T lymphocyte recognition, these cells become potential targets for natural killer (NK) cell-mediated lysis. We now show that K5 also downregulates ICAM-1 and B7-2, which are ligands for NK cell-mediated cytotoxicity receptors. As a consequence, K5 expression drastically inhibits NK cell-mediated cytotoxicity. Conversely, de novo expression of B7-2 and ICAM-1 resensitizes the K5-expressing cells to NK cell-mediated cytotoxicity. This is a novel viral immune evasion strategy where KSHV K5 achieves immune avoidance by downregulation of cellular ligands for NK cell-mediated cytotoxicity receptors.

Antigens, CD↗
PubMed2000

Treatment of tooth fracture by medium energy CO2 laser and DP-bioactive glass paste: thermal behavior and phase transformation of human tooth enamel and dentin after irradiation by CO2 laser.

Acute trauma or trauma associated with occlusal disharmony can produce tooth crack or fracture. Although several methods are proposed to treat the defect, however, the prognosis is generally poor. If the fusion of a tooth fracture by laser is possible it will offer an alternative to extraction or at least serve as an adjunctive treatment in the reconstruction. The responses of soft tissues to lasers of different wavelengths are fairly well known, but the reactions of hard tissues are still to be understood. The purpose of this research was to study the feasibility of using a medium energy continuous-wave CO(2) laser and a low melting-point bioactive glass to fuse or bridge tooth fractures. The present report is focused on the first part of the research, the analysis of changes in laser-irradiated human tooth enamel/dentin by means of X-ray diffractometer (XRD), Fourier-transforming infrared spectroscopy (FTIR), differential thermal analysis/thermogravimetric analysis (DTA/TGA), and scanning electron microscopy (SEM). After CO(2) laser irradiation, there were no marked changes in the X-ray diffraction pattern of the enamel when compared to that before laser treatment. However, a small peak belonging to alpha-TCP appeared at the position of 2theta=30.78 degrees C. After being treated with CO(2) laser, the dentin showed much sharper peaks on the diffraction patterns because of grain growth and better crystallinity. alpha-TCP and beta-TCP were identified after laser treatment. In the FTIR analysis, an HPO(4)(-2) absorption band was noted before laser treatment disappeared after the irradiation. No significant change in the absorption band of HPO(4)(-2) was found on the FTIR curves of enamel after laser treatment. The results of DTA/TGA indicated that loss of water and organic materials occurred in both enamel and dentin after laser treatment. Under SEM, melting and resolidification occurred in both enamel and dentin by medium energy of CO(2) laser. This implies that using a continuous-wave CO(2) laser of medium energy density to fuse a low melting-point bioactive glass to the enamel/dentin is possible. We believe these phase changes and thermal data can make a useful guide for future studies on the thermal interaction and bridging mechanism between the bioactive glass and enamel/dentin under CO(2) laser irradiation.

Journal Article↗
PubMed2000

Downregulation of major histocompatibility complex class I molecules by Kaposi's sarcoma-associated herpesvirus K3 and K5 proteins.

The T-cell-mediated immune response plays a central role in the defense against intracellular pathogens. To avoid this immune response, viruses have evolved elaborate mechanisms that target and modulate many different aspects of the host's immune system. A target common to many of these viruses is the major histocompatibility complex (MHC) class I molecules. Kaposi's sarcoma-associated herpesvirus (KSHV) encodes K3 and K5 zinc finger membrane proteins which remove MHC class I molecules from the cell surface. K3 and K5 exhibit 40% amino acid identity to each other and localize primarily near the plasma membrane. While K3 and K5 dramatically downregulated class I molecules, they displayed different specificities in downregulation of HLA allotypes. K5 significantly downregulated HLA-A and -B and downregulated HLA-C only weakly, but not HLA-E, whereas K3 downregulated all four HLA allotypes. This selective downregulation of HLA allotypes by K5 was partly due to differences in amino acid sequences in their transmembrane regions. Biochemical analyses demonstrated that while K3 and K5 did not affect expression and intracellular transport of class I molecules, their expression induced rapid endocytosis of the molecules. These results demonstrate that KSHV has evolved a novel immune evasion mechanism by harboring similar but distinct genes, K3 and K5, which target MHC class I molecules in different ways.

Animals↗
PubMed2000

Nucleotide excision repair/TFIIH helicases RAD3 and SSL2 inhibit short-sequence recombination and Ty1 retrotransposition by similar mechanisms.

Eukaryotic genomes contain potentially unstable sequences whose rearrangement threatens genome structure and function. Here we show that certain mutant alleles of the nucleotide excision repair (NER)/TFIIH helicase genes RAD3 and SSL2 (RAD25) confer synthetic lethality and destabilize the Saccharomyces cerevisiae genome by increasing both short-sequence recombination and Ty1 retrotransposition. The rad3-G595R and ssl2-rtt mutations do not markedly alter Ty1 RNA or protein levels or target site specificity. However, these mutations cause an increase in the physical stability of broken DNA molecules and unincorporated Ty1 cDNA, which leads to higher levels of short-sequence recombination and Ty1 retrotransposition. Our results link components of the core NER/TFIIH complex with genome stability, homologous recombination, and host defense against Ty1 retrotransposition via a mechanism that involves DNA degradation.

Adenosine Triphosphatases↗