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Biomedical subjects

J Choi

Publications and source records attributed to J Choi.

At least 37 records · Page 2Linked to original sources
PubMed2005

Second allografts for relapsed hematologic malignancies: feasibility of using a different donor.

A second allogeneic hematopoietic stem cell transplant (HSCT) for relapsed hematologic malignancies is an option in select patients after an initial allograft has failed. If the original donor is not available, a different donor may have to be considered. We report our experience of performing a second allogeneic HSCT using a different donor in patients with relapsed leukemia and lymphoma. In a 5-year period, six patients underwent a second allograft with myeloablative conditioning using a different donor. Four of these were retransplanted using a matched-unrelated donor. Four of the patients (67%) remain progression-free at a median follow-up of 32 months (range 3-72). There were no cases of transplant-related mortality. We conclude that a second allogeneic HSCT using a different donor is a viable option for selected patients relapsing after an allograft if the original donor is not available.

Adolescent↗
PubMed2005

Black shale as a sorbent for trichloroethylene and Cr(VI).

Black shale was examined as a natural sorbent for organic and inorganic contaminants. Trichloroethylene (TCE) could be removed well from the water by sorption onto the locally available black shale because of the high organic carbon content (5.2%) of the black shale in this study. Hexavalent chromium Cr(VI) was mainly removed by ionic sorption and reduction in batch and column experiments. Amphiphilic humic acid was also sorbed onto the black shale and could facilitate the sorption of TCE at the same time. Humic acid also enhanced the removal of Cr(VI) by reduction and sorption, but the amount of Cr(VI) adsorbed (mg kg(-1)) was smaller than that of TCE. Considering that the black shale in this study was used without any modifications and has a small surface area, black shale can be a cost-effective natural geosorbent and additive to remove organic contaminants and heavy metals.

Adsorption↗
PubMed2005

An open-label study of alefacept plus ultraviolet B light as combination therapy for chronic plaque psoriasis.

BACKGROUND: Alefacept, a fully human LFA-3/IgG(1) fusion protein, is a selective biological agent approved in the United States for the treatment of chronic plaque psoriasis. In phase 3 trials, clinical improvement and prolonged off-treatment remission of psoriasis correlated with reductions in circulating memory T cells. Reductions in pathogenic epidermal T cells in psoriatic lesions also have been noted following phototherapy with ultraviolet B (UVB) light. Because alefacept and UVB target T cells in different ways, combination therapy with these two agents may lead to greater efficacy. OBJECTIVES: To determine the safety, tolerability, and efficacy trends of combination therapy with alefacept plus UVB light in patients with chronic plaque psoriasis. METHODS: In an open-label, parallel-group study conducted at two sites, one in France and one in the United States, patients with chronic plaque psoriasis who were candidates for phototherapy received 12-weekly intramuscular injections of alefacept, 15 mg. In addition, patients were randomized to one of three treatment arms: no UVB treatment, 6-week UVB treatment, and 12-week UVB treatment. UVB treatment consisted of narrowband (NB) UVB at the site in France and broadband (BB) UVB at the site in the United States. The 12-week treatment period was followed by a 12-week follow-up period. Clinic visits occurred weekly during treatment and every 2-4 weeks during follow-up. RESULTS: A total of 60 patients (n = 30/site) were enrolled in the study. Alefacept was well tolerated when administered in combination with UVB treatment and as monotherapy. There was no evidence of increased phototoxicity or photosensitivity with the combination. At each study site, alefacept/UVB provided a higher overall response rate and led to a more rapid onset of response compared with alefacept monotherapy. Of patients who achieved > or = 50% reduction from baseline Psoriasis Area Severity Index (PASI 50) at 2 weeks after the last dose of alefacept, 75-100% in the combination therapy groups maintained this response throughout follow-up in the absence of further psoriasis therapy. CONCLUSIONS: In patients with chronic plaque psoriasis, combination therapy with alefacept plus short-term (6-12 weeks) UVB treatment is well tolerated with a trend toward greater and more rapid efficacy than alefacept alone.

Adult↗
PubMed2005

Pesticide metabolism in humans, including polymorphisms.

Recent epidemiologic studies involving Gulf War veterans or agricultural workers suggest that pesticide-pesticide or pesticide-drug interactions may be related to Gulf-War-related illnesses or elevated cancer risks, respectively. Metabolic interactions are one of many potential mechanisms requiring exploration in humans. The goal of the studies is to characterize important metabolic profiles of selected pesticides and examine potential interactions to characterize human risks associated with exposure. Pesticides examined using human liver microsomes and cytosolic fractions included chlorpyrifos, carbaryl and permethrin. The metabolic pathways involved include cytochrome P450 monooxygenases (CYP), esterases, and alcohol and aldehyde dehydrogenases. Specific isoforms and some polymorphic enzymes were characterized. Pesticide-pesticide interactions with metabolizing enzymes were demonstrated. Exposure of human hepatocytes to chlorpyrifos and permethrin demonstrated their potential to induce CYP isoforms using the bDNA (branched deoxyribonucleic acid) assay [used to monitor mRNA (messenger ribonucleic acid) levels]. These studies suggest that knowledge of human metabolic pathways will provide information that can aid the risk assessment process.

Environmental Exposure↗
PubMed2004

Bose-Einstein correlations of charged pion pairs in Au + Au collisions at square root sNN = 200 GeV.

Bose-Einstein correlations of identically charged pion pairs were measured by the PHENIX experiment at midrapidity in Au + Au collisions at square root s(NN)=200 GeV. The Bertsch-Pratt radius parameters were determined as a function of the transverse momentum of the pair and as a function of the centrality of the collision. Using the standard core-halo partial Coulomb fits, and a new parametrization which constrains the Coulomb fraction as determined from the unlike-sign pion correlation, the ratio R(out)/R(side) is within 0.8-1.1 for 0.25< <1.2 GeV/c. The centrality dependence of all radii is well described by a linear scaling in N(1/3)(part), and R(out)/R(side) for approximately 0.45 GeV/c is approximately constant at unity as a function of centrality.

Journal Article↗
PubMed2004

Measurement of nonrandom event-by-event fluctuations of average transverse momentum in square root of (sNN)=200 GeV Au+Au and p+p collisions.

Event-by-event fluctuations of the average transverse momentum of produced particles near midrapidity have been measured by the PHENIX Collaboration in square root of (sNN)=200 GeV Au+Au, and p+p collisions at the Relativistic Heavy Ion Collider. The fluctuations are observed to be in excess of the expectation for statistically independent particle emission for all centralities. The excess fluctuations exhibit a dependence on both the centrality of the collision and on the pT range over which the average is calculated. Both the centrality and pT dependence can be well reproduced by a simulation of random particle production with the addition of contributions from hard-scattering processes.

Journal Article↗
PubMed2004

Somatotopy and attentional modulation of the human parietal and opercular regions.

The somatotopical organization of the postcentral gyrus is well known, but less is known about the somatotopical organization of area 2, the somatosensory association areas in the postparietal cortex, and the parietal operculum. The extent to which these areas are modulated by attention is also poorly understood. For these reasons, we measured the BOLD signal when rectangular parallelepipeds of varying shape were presented to the immobile right hand or right foot of 10 subjects either discriminating these or just being stimulated. Activation areas in each subject were mapped against cytoarchitectural probability maps of area 2, IP1, and IP2 along the intraparietal sulcus and the parietal opercular areas OP1-OP4. In area 2, the somatotopical representation of the hand and foot were distinctly separate, whereas there was considerable overlap in IP1 and no clear evidence of separate representations in OP1, OP4, and IP2. The overlap of hand and foot representations increased in the following order: area 3a, 3b, 1, 2, IP1, OP4, IP2, and OP1. There were significant foot representations but no hand representations in right (ipsilateral) areas 3a, 3b, and 1. Shape discrimination using the foot as opposed to stimulation enhanced the signal in OP4 bilaterally, whereas discrimination with the hand enhanced the signal bilaterally in area 2, IP1, and IP2. These results indicate that somatosensory areas in humans are arranged from strong somatotopy into no somatotopy in the following order: 3a, 3b, 1, 2, IP1, OP4, IP2, and OP1. Higher order areas such as IP1, IP2, and OP4 showed task-related attentional enhancement.

Adult↗
PubMed2004

J/psi production from proton-proton collisions at square root of s=200 GeV.

J/psi production has been measured in proton-proton collisions at square root of s=200 GeV over a wide rapidity and transverse momentum range by the PHENIX experiment at the Relativistic Heavy Ion Collider. Distributions of the rapidity and transverse momentum, along with measurements of the mean transverse momentum and total production cross section are presented and compared to available theoretical calculations. The total J/psi cross section is 4.0+/-0.6(stat)+/-0.6(syst)+/-0.4(abs) mu b. The mean transverse momentum is 1.80+/-0.23(stat)+/-0.16(syst) GeV/c.

Journal Article↗
PubMed2004

Robust motor speed control under time varying loads in moving actuator type artificial heart (AnyHeart).

The Moving Actuator type artificial heart(AnyHeart) as well as many other artificial hearts uses a motor as its power source. For controllability of control parameters such as pump rate, pump output, blood pressure profile and flow form, the precise motor speed control is important. However, because the implantable device has limited carrying capacity of hardware components in size and number, applying diverse motor control methods are not possible. In addition, the existing PI (Proportional-Integral) motor controller does not show satisfactory performance. A new controller that is sufficiently robust for the changes of load and physical system parameters has been designed and tested. The robust speed controller is based on the sliding mode control method that is applicable to a system of which the ranges of uncertainty in physical parameters are known. In a mock circulation system test, the actual speed showed good tracking characteristics in respect to the reference speed. Fast follow-up characteristics were also observed under high afterload and speed conditions. The speed error, current and power consumption were reduced by about 40%. The proposed control technique overcomes the limitations of the PI controller, and makes important improvements in both performance and stability.

Algorithms↗
PubMed2004

Home care artificial heart monitoring system via internet.

The availability of a remote management system, which provides both physiological-related information about the patient and device-related information about the implanted device, would be helpful during in vivo experiments or clinical trials involving artificial heart implantation. In order to be able to monitor the course of the in vivo experiment continuously regardless of the patient's location, an internet-based remote monitoring system was developed, which can monitor physiological-related information such as pressure (AoP, LAP, RAP, PAP) and flow data, as well as device-related information such as current, direction and pump operating conditions. The home care artificial heart monitoring system which we developed consists of four main components, which are the transcutaneous information transmission system (TITS), local monitoring station (LMS), data server station (DSS), and client monitoring station (CMS). The device-related information and physiological-related information can be transmitted in real time from a patient in a remote non-clinical environment to the specialist situated in a clinic depending on the current capabilities and availability of the internet. The local monitoring station situated at the remote site is composed of a data acquisition and preprocessing unit connected to a computer via its RS-232 port, and which communicate using a Java-based client-server architecture. The remote monitoring system so developed was used during an in vivo experiment of the artificial heart implantation for 2 months and performed successfully according to design specifications.

Animals↗
PubMed2004

Tertiary treatment of biologically treated piggery wastewater using vibratory shear-enhanced RO membrane.

This study presents a good example for the tertiary treatment of biologically treated piggery wastewater using vibratory shear enhanced RO membrane (VSEP RO). Through a simple process combination, utilizing Bioceramic SBR(BCS) and VSEP RO, at Gimhae plant livestock wastewater is treated excellently to meet the strict effluent standards. Application of RO membrane directly to the biologically treated effluent has been successful without any pretreatment to reduce high suspended solids. The combination of VESP UF followed by RO filtration processes produced a higher recovery rate in the 3-week pilot test.

Animals↗
PubMed2003

Midrapidity neutral-pion production in proton-proton collisions at square root s = 200 GeV.

The invariant differential cross section for inclusive neutral-pion production in p+p collisions at sqrt[s]=200 GeV has been measured at midrapidity (|eta|<0.35) over the range 1<p(T) less, similar 14 GeV/c by the PHENIX experiment at the Relativistic Heavy Ion Collider. Predictions of next-to-leading order perturbative QCD calculations are consistent with these measurements. The precision of our result is sufficient to differentiate between prevailing gluon-to-pion fragmentation functions.

Journal Article↗
PubMed2003

Elliptic flow of identified hadrons in Au+Au collisions at sqrt sNN =200 GeV.

The anisotropy parameter (v(2)), the second harmonic of the azimuthal particle distribution, has been measured with the PHENIX detector in Au+Au collisions at sqrt[s(NN)]=200 GeV for identified and inclusive charged particle production at central rapidities (|eta|<0.35) with respect to the reaction plane defined at high rapidities (|eta|=3-4 ). We observe that the v(2) of mesons falls below that of (anti)baryons for p(T)>2 GeV/c, in marked contrast to the predictions of a hydrodynamical model. A quark-coalescence model is also investigated.

Journal Article↗
PubMed2003

Scaling properties of proton and antiproton production in sqrt[s(NN)]=200 GeV Au+Au collisions.

We report on the yield of protons and antiprotons, as a function of centrality and transverse momentum, in Au+Au collisions at sqrt[s(NN)]=200 GeV measured at midrapidity by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider. In central collisions at intermediate transverse momenta (1.5<p(T)<4.5 GeV/c) a significant fraction of all produced particles are protons and antiprotons. They show a centrality-scaling behavior different from that of pions. The pmacr;/pi and p/pi ratios are enhanced compared to peripheral Au+Au, p+p, and e(+)e(-) collisions. This enhancement is limited to p(T)<5 GeV/c as deduced from the ratio of charged hadrons to pi(0) measured in the range 1.5<p(T)<9 GeV/c.

Journal Article↗
PubMed2003

Stability and ensemble inequivalence in a globally coupled system.

We consider a system of globally coupled rotors, described by a set of Langevin equations, and examine the stability of the incoherent phase. The corresponding Fokker-Planck equation, providing a unified description of microcanonical and canonical ensembles, bears a few solutions, depending upon the ensemble. It is found that the stability of each solution varies differently with the temperature, revealing the inequivalence between the two ensembles. This also suggests a physical explanation of the quasistationarity observed in recent numerical results.

Journal Article↗
PubMed2003

Suppressed pi(0) production at large transverse momentum in central Au+Au collisions at sqrt[s(NN)]=200 GeV.

Transverse momentum spectra of neutral pions in the range 1<p(T)<10 GeV/c have been measured at midrapidity by the PHENIX experiment at BNL RHIC in Au+Au collisions at sqrt[s(NN)]=200 GeV. The pi(0) multiplicity in central reactions is significantly below the yields measured at the same sqrt[s(NN)] in peripheral Au+Au and p+p reactions scaled by the number of nucleon-nucleon collisions. For the most central bin, the suppression factor is approximately 2.5 at p(T)=2 GeV/c and increases to approximately 4-5 at p(T) approximately 4 GeV/c. At larger p(T), the suppression remains constant within errors. The deficit is already apparent in semiperipheral reactions and increases smoothly with centrality.

Journal Article↗
PubMed2003

Ethanol-induced neuronal apoptosis in vivo requires BAX in the developing mouse brain.

A single episode of ethanol intoxication triggers widespread apoptotic neurodegeneration in the infant rat or mouse brain. The cell death process occurs over a 6-16 h period following ethanol administration, is accompanied by a robust display of caspase-3 enzyme activation, and meets ultrastructural criteria for apoptosis. Two apoptotic pathways (intrinsic and extrinsic) have been described, either of which may culminate in the activation of caspase-3. The intrinsic pathway is regulated by Bax and Bcl-XL and involves Bax-induced mitochondrial dysfunction and release of cytochrome c as antecedent events leading to caspase-3 activation. Activation of caspase-8 is a key event preceding caspase-3 activation in the extrinsic pathway. In the present study, following ethanol administration to infant mice, we found no change in activated caspase-8, which suggests that the extrinsic pathway is not involved in ethanol-induced apoptosis. We also found that ethanol triggers robust caspase-3 activation and apoptotic neurodegeneration in C57BL/6 wildtype mice, but induces neither phenomenon in homozygous Bax-deficient mice. Therefore, it appears that ethanol-induced neuroapoptosis is an intrinsic pathway-mediated phenomenon involving Bax-induced disruption of mitochondrial membranes and cytochrome c release as early events leading to caspase-3 activation.

Animals↗