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Biomedical subjects

J S Choi

Publications and source records attributed to J S Choi.

At least 55 records · Page 3Linked to original sources

Radiolabeling brachytherapy sources with Re-188 through chelating microfilms: stents.

Rhenium-188 (Re-188, T(1/2) = 17 h) emits beta particles (E(max) = 2. 12 MeV) having an ideal range for intravascular brachytherapy and certain cancer brachytherapies. Re-188 was attached to metal wafers and stents via a chelating microfilm, and these brachytherapy sources characterized in vitro and in vivo. To prepare the sources, a siloxane film containing reactive amines was plasma deposited on the metal, a chelating microfilm conjugated to the amines, and the chelating microfilm used to attach Re-188. Re-188 was selectively bound to materials coated with the chelating microfilm. Binding correlated with the amount of radionuclide used. Wafers (1 cm(2)) bound up to 62.9 MBq (1.7 mCi) of Re-188 with yields generally near 30%. Stents bound up to 26.6 MBq (720 microCi). Typically, stents were labeled to bind 4-12 MBq and deposit 10-30 Gy at 2 mm in the arterial wall. In phantom studies, the longer nitinol stents deposited doses of 2.3 Gy/MBq (0.085 Gy/microCi), while shorter stainless steel stents deposited 4.62 Gy/MBq (0.171 Gy/microCi). After placement in arteries of pigs, only the Re-188-stents were detected by scintigraphy at times up to 24 h. Scintigraphy did not detect activity in other organs. Blood sampling (0.1-24 h) detected maximum radioactivity (up to 388 cpm/mL/100micro Ci) at 6 h. We conclude that on-demand radiolabeling of stents and other brachytherapy sources with Re-188 can be performed routinely.

Biocompatible Materials↗

Intraobserver and interobserver measurements of the anorectal angle and perineal descent in defecography.

PURPOSE: Anorectal angle and perineal descent can be measured either by drawing a line defined by the impression of the puborectalis muscle and the tangential of the posterior rectal wall (Method A) or by drawing a straight line at the level of the posterior rectal wall parallel to the central longitudinal axis of the rectum (Method B). The aim of this study was to assess the reproducibility of measuring anorectal angle and perineal descent by two different methods according to intraobserver and interobserver measurement and to evaluate which method yields more consistent results. METHODS: Five physicians who have had an average of 1.3 years (range, 6 months to 1.5 years) experience in defecographic measurement drew both lines on 63 randomly selected defecographic films and measured anorectal angle and perineal descent by the two methods. The defecographic parameters were measured twice by each observer during a three-week interval. To avoid potential bias, one physician who did not participate in either measurement of perineal descent or anorectal angle performed all data collection. Intraobserver and interobserver agreement was quantified using Shrout and Fleiss intraclass correlation coefficients. RESULTS: The mean and range of intraclass correlation coefficients for intraobserver agreement of measuring anorectal angle and perineal descent by Method A were 0.71 (0.6-0.78) and 0.89 (0.74-0.97), respectively, whereas with Method B the coefficients were 0.81 (0.73-0.89) and 0.93 (0.89-0.99), respectively. Regarding the interobserver agreement of the five observers, the mean coefficients for measurement of both anorectal angle and perineal descent by both methods showed similar agreement levels (0.88 and 0.98 by Method A and 0.89 and 0.97 by Method B). The mean (+/- standard deviation) values of anorectal angle and perineal descent found by Method B were significantly larger than those found by Method A (103.3 degrees +/- 19.6 and 6.56+/-3.20 cm and 91.1 degrees +/- 25.6 and 5.64+/-3.42 cm, respectively; P<0.001). CONCLUSION: Intraobserver and interobserver intraclass correlation coefficients of anorectal angle and perineal descent, which were measured by both methods, were more than 0.60, indicating that both methods are reliable and consistent for measurement of anorectal angle and perineal descent. However, centers should consistently use the same line for measurement of anorectal angle and perineal descent because of the statistically significant differences between the two methods and the possibility of inconsistent results.

Adult↗

Functional outcomes in patients with mucosal ulcerative colitis after ileal pouch-anal anastomosis by the double stapling technique: is there a relation to tissue type?

PURPOSE: The aim of this study was to evaluate any differences in functional outcome in patients with mucosal ulcerative colitis after restorative proctocolectomy and ileal pouch-anal anastomosis with use of the double stapling technique relative to the type of tissue in the stapled doughnut. METHODS: Between September 1988 and June 1997, the pathology of all patients with mucosal ulcerative colitis who underwent ileal pouch-anal anastomosis with use of the double stapling technique were reviewed. Information was obtained regarding the tissue types in the distal tissue rings (doughnuts) obtained from the stapled ileal pouchanal anastomosis. The level of anastomosis was classified according to the type of tissue in the distal doughnut: Group I- patients in whom the anal transitional zone was removed and the distal doughnut included squamous epithelium or transitional epithelium and Group II- patients in whom the anal transitional zone was preserved because the distal doughnut revealed only columnar epithelium. Functional outcomes were assessed and compared by detailed questionnaires mailed to all patients at least one year after ileal pouch-anal anastomosis surgery. RESULTS: Distal doughnuts were obtained from the stapled ileal pouch-anal anastomosis in 222 patients with mucosal ulcerative colitis. Follow-up data at a mean of 38 (range, 12-132) months were obtained in 138 (62.2 percent) patients, including 72 males, with a mean age of 46.9 (range, 13-79) years. Group I consisted of 40 patients (29 percent; 35 (25.4 percent) who had squamous epithelium and 5 (3.6 percent) who had transitional epithelium in the distal tissue rings). Group II consisted of 98 patients (71 percent) with columnar epithelium in the distal tissue rings. Age at diagnosis and operation, duration of disease, length of follow-up, and stage of pouch surgery were similar in the two groups. Incontinence scores, frequency of bowel movement, use of a protective pad, discrimination between gas and stool, use of antidiarrheals, life-style alteration, and patient satisfaction showed similar functional results between the two groups. CONCLUSIONS: The tissue type in the stapler distal doughnut did not greatly influence functional outcome. Failure to identify a relationship may attest to the variable height and composition of the anal transitional zone.

Adolescent↗

Use of bioresorbable membrane (sodium hyaluronate + carboxymethylcellulose) after controlled bowel injuries in a rabbit model.

PURPOSE: Patients in whom enterolysis is performed are at high risk for recurrence of adhesions and for injury during adhesiolysis. Therefore, the aim of this study was to assess the safety of sodium hyaluronate-based bioresorbable membrane (Seprafilm) after myotomy and enterotomy. METHODS: A total of 60 rabbits underwent laparotomy with equal distribution to one of three groups: creation of either three repaired, or three unrepaired myotomies, or three repaired enterotomies. Thus, a total of 180 defects were created in the same anatomic positions. One-half of the animals in each group had the surface of the myotomies or enterotomies covered by Seprafilm. Fourteen days later, after complete absorption of Seprafilm, the presence of intra-abdominal abscess, adhesions, and the integrity of the suture line were evaluated by a surgeon blinded to the use of Seprafilm and by a standard radiographic isobaric contrast study. Statistical analysis was done by use of Fisher's exact test; significance was set at P < 0.05. RESULTS: The incidence of adhesions in the repaired myotomy group were 2 (6.6 percent) and 9 (30 percent) in the Seprafilm and control (nonSeprafilm) groups, respectively (P < 0.05); in the unrepaired myotomy group, 2 (6.6 percent) and 10 (33 percent) in the Seprafilm and control groups, respectively (P < 0.05); and in the enterotomy group, 28 (94 percent) and 29 (97 percent) in the Seprafilm and control groups, respectively (P = not significant). A single phlegmon occurred in the myotomy group at a Seprafilm site (1.6 (1/60) vs. 0 percent, P = not significant). There were no leaks in this group. In the enterotomy group, the incidence of phlegmons was 33 percent (10/30) in the Seprafilm group, whereas it was 27 percent (8/30) in the nonSeprafilm group (P = not significant). The incidence of leaks was 6.6 (2/30) and 10 percent (3/30) in the Seprafilm and nonSeprafilm group, respectively (P = not significant). CONCLUSION: The use of Seprafilm at the sites of myotomies significantly reduced the incidence of adhesions. Effectiveness at the enterotomy site may have been attenuated by a greater inflammatory response. Importantly, Seprafilm did not increase septic mortality in any group.

Absorbable Implants↗

Isolation of luteolin 7-O-rutinoside and esculetin with potential antioxidant activity from the aerial parts of Artemisia montana.

The antioxidant activity of Artemisia montana was determined by measuring the radical scavenging effect on 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical and inhibitory activity against free radical generation of hepatocytes (AC2F). The methanol extract of A. montana showed strong radical scavenging activity at a concentration of 10.1 microg/ml, and thus fractionated by solvent extraction. Esculetin and luteolin 7-O-rutinoside (scolymoside) were isolated as the active principles from the EtOAc and Interphase fractions, respectively. The antioxidant activity of these compounds were comparable to that of L-ascorbic acid.

Antioxidants↗

Comparative evaluation of antioxidant potential of alaternin (2-hydroxyemodin) and emodin.

The antioxidant activities of alaternin (2-hydroxyemodin) and emodin were compared for their respective potentials to inhibit lipid peroxidation in the linoleic acid system by the thiocyanate method, to inhibit total reactive oxygen species generation in kidney homogenates using 2',7'-dichlorodihydrofluorescein diacetate, to inhibit peroxynitrite formation by the 3-morpholinosydnonimine system, which generates superoxide radical and nitrogen monooxide, and to scavenge authentic peroxynitrites. Both alaternin and emodin were found to inhibit the peroxidation of linoleic acid by the thiocyanate method in a dose-dependent manner. Whereas the former shows inhibitory activities in reactive oxygen- and nitogen-mediated reactions, the latter does not. These results indicate that alaternin is a potentially effective and versatile antioxidant and can be used to protect biological systems and functions against various oxidative stresses.

Antioxidants↗

New acetylenic compounds from the stony coral Montipora sp.

Six new acetylenic compounds (1-6) with cytotoxic activities against human solid tumor cell lines (SK-OV-3, SK-MEL-2, XF498, and HCT15) have been isolated from the stony coral Montipora sp. Structures of the compounds 1-6 were elucidated based on analysis of the NMR and MS data.

Animals↗

A cyclohexanonyl bromophenol from the red alga Symphyocladia latiuscula.

From an extract of the red alga Symphyocladia latiuscula, a bromophenol (1) was isolated and characterized as (2R)-2-(2,3, 6-tribromo-4,5-dihydroxybenzyl)-cyclohexanone based on the spectroscopic evidence. The bromophenol was found to be a scavenger of 1,1-diphenyl-2-picrylhydrazyl radical.

Bromine↗

Direct block by bisindolylmaleimide of rat Kv1.5 expressed in Chinese hamster ovary cells.

The interaction of bisindolylmaleimide (BIM), widely used as a specific protein kinase C (PKC) inhibitor, with rat brain Kv1.5 (rKv1.5) channels stably expressed in Chinese hamster ovary cells was investigated using the whole-cell patch-clamp technique. BIM (I) and its inactive analog, BIM (V), inhibited rKv1.5 currents at +50 mV in a reversible concentration-dependent manner with an apparent K(d) value of 0.38 and 1.70 microM, respectively. BIM (I) accelerated the decay rate of inactivation of rKv1.5 currents but did not significantly modify the kinetics of current activation. Other specific PKC inhibitors, chelerythrine and PKC 19-36, had no effect on rKv1.5 and did not prevent the inhibitory effect of BIM (I). The inhibition of rKv1.5 by BIM (I) and BIM (V) was highly voltage-dependent between -30 and 0 mV (voltage range of channel opening), suggesting that both drugs interact preferentially with the open state of the channel. The additional inhibition by BIM (I) displayed a voltage dependence (delta = 0.19) in the full activation voltage range positive to 0 mV, but was not shown in BIM (V) (delta = 0). The rate constants of association and dissociation for BIM (I) were 9.63 microM(-1) s(-1) and 5.82 s(-1), respectively. BIM (I) increased the time constant of deactivation of tail currents from 26. 35 to 45.79 ms, resulting in tail crossover phenomenon. BIM (I) had no effect on the voltage dependence of steady-state inactivation. BIM (I) produced use-dependent inhibition of rKv1.5, which was consistent with the slow recovery from inactivation in the presence of drug. These results suggest that BIM (I) directly inhibits rKv1.5 channels in a phosphorylation-independent, and state-, voltage-, time-, and use-dependent manner.

Algorithms↗

Circadian changes in the pharmacokinetics of triamcinolone acetonide in rabbits.

Circadian changes in the pharmacokinetics of triamcinolone acetonide were investigated in rabbits after a single intravenous administration of the drug, 1.0 mg/kg, at 08:00 and 20:00. At 20:00 hrs, the area under the plasma concentration-time curve from time zero to time infinity was significantly greater (46% increase), and this could be due to significantly slower total body clearance (31% decrease) than that at 08:00. The terminal half-life was significantly longer (82%) at 20:00. However, the apparent volume of distribution at steady state and total amount of unchanged drug excreted in 12 hr urine were not significantly different between two groups of rabbits.

Animals↗

Cadmium inhibits albumin endocytosis in opossum kidney epithelial cells.

Chronic exposure to cadmium results in proteinuria. To gain insights into the mechanism by which cadmium inhibits the protein transport in the renal proximal tubule, we investigated the effects of cadmium on the receptor-mediated endocytosis of albumin, using fluorescein isothiocyanate-labeled bovine serum albumin (FITC-albumin) as a model substrate and opossum kidney cell line (OK cell) as a proximal tubular cell model. Cell monolayers grown to confluence were treated with 100 microM CdCl(2) for 60 min at 37 degrees C, washed, and tested for FITC-albumin uptake (37 degrees C) and surface binding (4 degrees C). The amounts of FITC-albumin uptake and binding were quantified by fluorimetrically determining the cell-adherent fluorescence. Both the binding and uptake of FITC-albumin by OK cells appeared to be saturable and inhibitable by unlabeled albumin in the medium, indicating that specific receptor sites were involved. The uptake of FITC-albumin was inhibited by agents that interfere with the formation of endocytotic vesicle (hypertonic mannitol), endosomal acidification (NH(4)Cl), and vesicular trafficking (cytochalasin D and nocodazole), confirming that the uptake occurred via the process of receptor-mediated endocytosis. In cells treated with cadmium, the specific FITC-albumin uptake was significantly attenuated, and this was due to a reduction in V(max) and a rise in K(m). These changes in kinetic parameters were similar to those induced by NH(4)Cl. The binding of FITC-albumin to the apical surface of OK cells was inhibited by cadmium treatment, and this was attributed to a reduction in B(max). The values of K(d) and its pH dependency were not altered by cadmium treatment. The formation of endocytotic vesicles, as judged by fluid phase endocytosis of FITC-inulin, was not changed by cadmium treatment. These results indicate that the receptor-mediated endocytosis of albumin is impaired in cadmium-treated OK cells most likely due to a defect in endosomal acidification and the attendant fall in ligand-receptor dissociation, which impairs receptor recycling and the overall efficiency of endocytosis.

Ammonium Chloride↗

Characterization of a targeted gene carrier, lactose-polyethylene glycol-grafted poly-L-lysine and its complex with plasmid DNA.

The physicochemical properties and gene transfer ability of lactose-polyethylene glycol-grafted poly-L-lysine (Lac-PEG-PLL) were investigated. A dye displacement assay showed that plasmid DNA self-assembled with Lac-PEG-PLL, and condensation began at a <1:1 charge ratio of plasmid DNA to polymer. In atomic force microscopy, spontaneously assembled Lac-PEG-PLL/DNA complexes revealed a compact structure, with a size of about 100-200 nm. Circular dichroism spectra of Lac-PEG-PLL/DNA complexes revealed that the secondary structure of DNA was altered by complex formation and was similar to that of the poly-L-lysine/DNA complex. Lac-PEG-PLL was shown to protect DNA against nuclease action in a DNase I protection assay. The cytotoxicity test demonstrated that the complex composed of plasmid DNA and Lac-PEG-PLL had little influence on the viability of HepG2 cells, especially in comparison with that of poly-L-lysine/DNA complexes. In conclusion, our copolymer, Lac-PEG-PLI, formed complexes with plasmid DNA (on average, 150 nm), gave little cytotoxicity, and showed increased efficiency of gene transfer into hepatoma cells in vitro. Lactose-polyethylene glycol was grafted to poly-L-lysine to be used as a gene carrier for hepatoma cell targeting and to improve the solubility of the polyplexes. The average size of the carrier/DNA complexes was about 150 nm. The complexes also proved to have high resistance against nuclease attack and little cytotoxicity. The polymer also delivered plasmid DNA efficiently into a HepG2 cell line. Lac-PEG-PLL was more efficient than Lipofectin or galactose-PEG-PLL in transfection efficiency.

Biological Assay↗

Improved cycle sequencing of GC-rich DNA template.

Even when DNA sequencing of purified DNA template failed under the optimal condition, it can be generally contributed to high GC content. GC-rich region of template causes a secondary structure to produce shorter readable sequence. To solve this problem, the sequencing reaction was modified by using dimethyl sulfoxide (DMSO). It was found that 5% (v/v) of DMSO in the reaction mixture recovers sequencing signal intensity with reduced frequency of ambiguous bases. When DMSO was added to sequencing reaction of DNA template with normal GC content, it did not show any adverse effect. Sequencing accuracy and unambiguous base frequency were significantly improved at concentration of 2% to 5% (v/v) DMSO in GC-rich DNA template. DMSO has been empirically introduced to enhance the efficiency of PCR in GC-rich templates. However, the underlying mechanism of improved cycle sequencing by DMSO is unknown. Thus, cycle sequencing reaction was remodified with other additives such as N-methyl imidazole, N-methyl2-pyrrolidone, N-methyl-2-pyridone and glycerol, possessing the similar chemical properties as DMSO. Most of methyl nitrogen ring-containing chemicals did not improve sequencing accuracy, whereas only glycerol mimicked the positive effect of DMSO by the same extent. In the present study, we suggest that the treatment of DMSO improve cycle sequencing by the alteration of structural conformation of GC-rich DNA template.

Base Composition↗

Structural identification of glycerolipid molecular species isolated from cyanobacterium Synechocystis sp. PCC 6803 using fast atom bombardment tandem mass spectrometry.

Our previous works have demonstrated that fast atom bombardment tandem mass spectrometry can be a valuable tool in determining the complete structure of glycoglycerolipids and glycerophospholipids. Collision-induced dissociation of sodium-adducted molecular ions ([M + Na]+ or [M - H + 2Na]+) generates diverse product ions informative on the double-bond position in fatty acyl groups as well as the polar head group and fatty acid composition. Here we report that this direct and rapid method can be applied to the structural determination of individual molecular species of each glycerolipid class purified from the total lipid extract of cyanobacterium Synechocystis sp. PCC 6803. Especially, based on the preference for the loss of the fatty acyl group positioned at the sn-2, it was proved that all of the molecular species of diacylglycerolipids contained a palmitoyl group exclusively at the sn-2 position. Additionally, lysoglycerolipids, monoacyl forms of four major membrane diacylglycerolipids, were first isolated together from a fresh extract. Using fast atom bombardment mass spectrometry and tandem mass spectrometry, it was found that each lysoglycerolipid had a molecular species with only palmitic acid as a fatty acyl group. Thus, these compounds could be synthesized by specific enzyme-catalyzed hydrolysis of the sn-1 fatty acyl group of the corresponding diacylglycerolipids.

Cyanobacteria↗

Inhibition by fluoxetine of voltage-activated ion channels in rat PC12 cells.

The effects of fluoxetine (Prozac) on voltage-activated K+, Ca2+ and Na+ channels were examined using the whole-cell configuration of the patch clamp technique in rat pheochromocytoma (PC12) cells. When applied to the external bath solution, fluoxetine (1, 10, 100 microM) decreased the peak amplitude of K+ currents. The K+ current inhibition by fluoxetine (10 microM) was voltage-independent and the fraction of current inhibition was 39.7-51.3% at all voltages tested (0 to +50 mV). Neither the activation and inactivation curves nor the reversal potential for K+ currents was significantly changed by fluoxetine. The inhibition by fluoxetine of K+ currents was use- and concentration-dependent with an IC50 of 16.0 microM. The inhibition was partially reversible upon washout of fluoxetine. The action of fluoxetine was independent of the protein kinases, because the protein kinase C or A inhibitors (H-7, staurosporine, Rp-cAMPS) did not prevent the inhibition by fluoxetine. Intracellular infusion with GDPbetaS or pretreatment with pertussis toxin did not block the inhibitory effects of fluoxetine. The inhibitory action of fluoxetine was not specific to K+ currents because it also inhibited both Ca2+ (IC50 = 13.4 microM) and Na+ (IC50 = 25.6 microM) currents in a concentration-dependent manner. Our data indicate that when applied to the external side of cells, fluoxetine inhibited voltage-activated K+, Ca2+ and Na+ currents in PC12 cells and its action on K+ currents does not appear to be mediated through protein kinases or G proteins.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

Antioxidant flavonoids and chlorogenic acid from the leaves of Eriobotrya japonica.

The antioxidant activity of Eriobotrya japonica was determined by measuring the radical scavenging effect on DPPH (1,1-diphenyl-2-picrylhydrazyl) radical and lipid peroxidation produced when mouse liver homogenate was exposed to the air at 37 degrees C, using 2-thiobarbituric acid (TBA). The methanol extract and its fractions of Eriobotrya japonica leaves showed strong antioxidant activity. The antioxidant activity of EtOAc and n-BuOH soluble fractions were stronger than the others, and were further purified by repeated silica gel, MCl gel CHP-20P, and Sephadex LH-20 column chromatography. Antioxidant chlorogenic acid, quercetin-3-sambubioside from n-BuOH fraction, and methyl chlorogenate, kaempferol- and quercetin-3-rhamnosides, together with the inactive ursolic acid and 2 alpha-hydroxyursolic acid from EtOAc fraction were isolated. Antioxidant flavonoids and chlorogenic acid also showed prominent inhibitory activity against free radical generation in dichlorofluorescein (DCF) method.

Animals↗

Staurosporine directly blocks Kv1.3 channels expressed in Chinese hamster ovary cells.

The effects of staurosporine (ST), a widely used protein kinase C (PKC) inhibitor, were examined on Kv1.3 channels stably expressed in Chinese hamster ovary (CHO) cells using the whole-cell and excised inside-out configurations of the patch clamp technique. In whole-cell recordings, ST, at external concentrations from 300 nM to 10 microM, accelerated the rate of inactivation of Kv1.3 currents and thereby reduced the current at the end of the depolarizing pulse in a concentration-dependent manner with an IC50 of 1.2 microM. The actions of ST were unaffected by pretreatment with another selective PKC inhibitor, chelerythrine, or by including the PKC pseudosubstrate peptide inhibitor, PKC 19-36, in the intracellular solution. Rp-cAMPS, a specific protein kinase A inhibitor, included in intracellular solution did not affect the effects of ST. Furthermore, the same effects of ST on Kv1.3 were also observed in excised inside-out patches when applied to the internal face of the membrane. These effects were completely reversible upon washing. Current-voltage relations for Kv1.3 currents at the end of voltage steps indicated that ST reduced Kv1.3 currents over a wide voltage range. The blockade exhibited a shallow voltage dependence between -10 mV and +40 mV, increasing at more positive potentials. ST had no effect on the voltage dependence of steady-state inactivation. It reduced the tail current amplitude and slowed the deactivation time course, resulting in a crossover phenomenon. These results suggest that the action of ST on Kv1.3 is independent of PKC and PKA inhibition. ST blocks the open state of Kv1.3 channels to produce an apparent acceleration of the inactivation rate.

Alkaloids↗

Identification of acylated glycoglycerolipids from a cyanobacterium, Synechocystis sp., by tandem mass spectrometry.

Acylated glycoglycerolipids were identified in the total lipid extract from cyanobacterium Synechocystis sp. PCC 6803. These compounds have a palmitoyl group esterified to the hydroxyl group at the C-6 position of the terminal glycosyl moiety of digalactosyl monoacylglycerol and digalactosyl diacylglycerol. Their structural elucidation was accomplished by tandem mass spectrometry coupled with fast atom bombardment ionization. Acylated digalactosyl monoacylglycerol has a structure of 1-hydroxy-2-palmitoyl-3-O-[(6-O-palmitoyl)-alpha-D-galactopyranosyl -(1-->6)-beta-D-galactopyranosyl]-sn-glycerol. This compound has not been reported previously.

Acylation↗