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Biomedical subjects

S H Cheon

Publications and source records attributed to S H Cheon.

At least 19 recordsLinked to original sources
PubMed2001

A whole blood bactericidal assay for tuberculosis.

The bactericidal activity of orally administered antituberculosis (anti-TB) drugs was determined in a whole blood culture model of intracellular infection in which microbial killing reflects the combined effects of drug and immune mechanisms. Rifampin (Rif) was the most active compound studied and reduced the number of viable bacilli by >4 logs. Isoniazid (INH), 2 quinolones, and pyrazinamide (PZA) showed intermediate levels of activity. Ethambutol exerted only a bacteristatic effect; amoxicillin/clavulanate was inactive. The combination of INH-Rif-PZA showed strong activity against 11 drug-sensitive isolates (mean, -3.8 log) but no activity against 12 multidrug-resistant (MDR) strains. The combination of levofloxacin-PZA-ethambutol had intermediate bactericidal activity against MDR isolates (mean, -1.2 log) but failed to equal that of INH-Rif-PZA against sensitive isolates (P<.001). The whole blood BACTEC method (Becton Dickinson) may be useful for the early clinical evaluation of new anti-TB drugs and in the management of individual patients.

Anti-Infective Agents↗
PubMed2001

Thermal inactivation kinetics and application of phospho- and galactolipid-degrading enzymes for evaluation of quality changes in frozen vegetables.

Lipid-acyl hydrolases (LAHases) play significant roles in lipid degradation during the storage of vegetables. In particular, spinach contains a large portion of galactolipids (59.5%) and phospholipids (22.4%) among its fat-soluble components, which are used as substrates for LAHases. Thermal inactivation of various LAHases, including phospholipases A, C, and D, phosphatase, and galactolipase, from spinach and carrot was investigated to optimize the blanching process prior to the frozen storage of vegetables. Thermostability of phospholipase C or galactolipase was greatest among the LAHases from both spinach and carrot. Galactolipase from spinach exhibited a D value of 3.39 x 10(2) s at 80 degrees C and a z value of 8.21 degrees C, whereas phospholipase C from spinach showed D(80) of 1.72 x 10(2) s with a z value of 9.26 degrees C. In the case of LAHases from carrot, the D(65) and z values of galactolipase were 6.66 x 10(2) s and 8.69 degrees C, respectively, whereas phospholipase C displayed D(85) of 3.12 x 10(2) s and a z value of 15.8 degrees C. Highly active and thermostable galactolipase and phospholipase C in spinach and carrot made it possible for them to be used as indicator enzymes for the determination of quality deterioration of the stored vegetables.

Food Handling↗
PubMed2000

Effect of dietary linoleate/alpha-linolenate balance on the brain lipid composition, reproductive outcome and behavior of rats during their prenatal and postnatal development.

The effect of the dietary linoleate (LA)/alpha-linolenate (LNA) balance during development on the brain lipid composition, reproductive outcome and behavior of rats was studied. Female rats were fed on experimental diets during pregnancy and the resulting pups for 16 weeks. The dietary LA/LNA ratios were 1.07 (LA1), 2.64 (LA2), 4.45 (LA3), 7.68 (LA4) and 10.35 (LA5). The relative content of docosahexaenoate (DHA) in the brain of pups tended to increase with decreasing LA/LNA ratio at 0 and 3 weeks, while the level of DHA was maintained constant at 16 weeks regardless of the dietary LA/LNA ratio. The learning ability was measured at 12 weeks of age, and there was no difference among the groups. In an open field test, the exploratory index was significantly lower in the LA1 group than in the LA2 group. The LA1 group had a smaller litter size and lower survival rate than the other groups. We conclude that if the diet contained appropriate amounts and balance of LA and LNA, it was possible for rats to synthesize an appropriate amount of DHA and have normal behavioral activity without DHA supplementation.

Animals↗
PubMed2000

Inflammatory pseudotumor of the urinary bladder in a child.

The inflammatory pseudotumor of the urinary bladder is rare, especially in children. It is a benign proliferative lesion of the submucosal stroma easily mistaken for a sarcoma clinically, so it should be differentiated from a malignant neoplasm. We report the case of bladder inflammatory pseudotumor in a 7-year-old girl.

Child↗
PubMed1999

Synthesis of sesquiterpene derivatives as potential antitumor agents; elemane derivatives.

Derivatives of elema-1,3-diene were synthesized in several steps as polar analogs of beta-elemene, antitumor agent under clinical phase. The lactone ring of compound 1 was opened by LiAlH4 to give diol 2 which was selectively protected by TBDPSCl. After acetylation of the secondary alcohol, the acetylated product was ozonolyzed and reduced to give elemane derivative 4 which was converted to diolefin 8 via selenides subsequent deprotection by tetrabutylammonium fluoride gave two compounds 9, 10.

Antineoplastic Agents↗
PubMed1999

Studies on the synthesis and in vitro antitumor activity of the isoquinolone derivatives.

3-Arylisoquinolin-1(2H)-ones (2) are possible bioisosteres of the 5-[4'-(piperidinomethyl)phenyl]-2,3-dihydroimidazo[2,1-a]iso quinoline (1) which is in clinical evaluation for the treatment of cancer. Structure-activity relationship studies of 3-arylisoquinolin-1(2H)-ones (2) led to the synthesis of 3-arylquinolin-2(1H)-ones (3). A number of 3-phenyl substituted quinolin-2(1H)-ones were synthesized and tested for their in vitro antitumor activity against four different human tumor cell lines and 3-phenyl-N-benzyl-3,4-dihydroquinolin-2(1H)-one (12) showed the most potent activity.

Antineoplastic Agents↗
PubMed1999

Drug tolerance in Mycobacterium tuberculosis.

Although Mycobacterium tuberculosis is eradicated rapidly during therapy in some patients with pulmonary tuberculosis, it can persist for many months in others. This study examined the relationship between mycobacterial drug tolerance (delayed killing in vitro), persistence, and relapse. It was performed with 39 fully drug-susceptible isolates from a prospective trial of standard short-course antituberculous therapy with sputum smear-positive, human immunodeficiency virus-uninfected subjects with pulmonary tuberculosis in Brazil and Uganda. The rate of killing in vitro was determined by monitoring the growth index (GI) in BACTEC 12B medium after addition of drug to established cultures and was measured as the number of days required for 99% sterilization. Drugs differed significantly in bactericidal activity, in the following order from greatest to least, rifampin > isoniazid-ethambutol > ethambutol (P < 0.001). Isolates from subjects who had relapses (n = 2) or in whom persistence was prolonged (n = 1) were significantly more tolerant of isoniazid-ethambutol and rifampin than isolates from other subjects (P < 0.01). More generally, the duration of persistence during therapy was predicted by strain tolerance to isoniazid and rifampin (P = 0.012 and 0.026, respectively). Tolerance to isoniazid-ethambutol and tolerance to rifampin were highly correlated (P < 0.001). Tolerant isolates did not differ from others with respect to the MIC of isoniazid; the rate of killing of a tolerant isolate by isoniazid-ethambutol was not increased at higher drug concentrations. These observations suggest that tolerance may not be due to drug-specific mechanisms. Tolerance was of the phenotypic type, although increased tolerance appeared to emerge after prolonged drug exposure in vivo. This study suggests that drug tolerance may be an important determinant of the outcome of therapy for tuberculosis.

Antitubercular Agents↗
PubMed1998

Substituted tetrahydropyrrolo[2,1-b]oxazol-5(6H)-ones and tetrahydropyrrolo[2,1-b]thiazol-5(6H)-ones as hypoglycemic agents.

A series of substituted tetrahydropyrrolo[2,1-b]oxazol-5(6H)-ones and tetrahydropyrrolo[2,1-b]thiazol-5(6H)-ones was synthesized from amino alcohols or amino thiols and keto acids. A pharmacological model based on the results obtained with these compounds led to the synthesis and evaluation of a series of isoxazoles and other monocyclic compounds. These were evaluated for their ability to enhance glucose utilization in cultured L6 myocytes. The in vivo hypoglycemic efficacy and potency of these compounds were evaluated in a model of type 2 diabetes mellitus (non-insulin-dependent diabetes mellitus), the ob/ob mouse. 25a(2S) (SDZ PGU 693) was selected for further pharmacological studies.

Animals↗
PubMed1998

Synthesis of antineoplaston A10 analogs as potential antitumor agents.

Several aniline mustard analogues were obtained by introducing N,N-bis(2-chloroethyl)amino moiety to phenyl ring of A10 analogues in order to increase reactivity of A10 analogs and selectivity into DNA. The in vitro antitumor activity of synthesized compounds was evaluated using five different solid tumor cell lines by SRB method. Aniline mustard analogues exhibited more potent antitumor activity than A10 analogs. Especially, m-aniline mustard of benzoyl analogue displayed remarkable antitumor activity.

Antineoplastic Agents↗
PubMed1998

Synthesis and structure-activity relationship studies of substituted isoquinoline analogs as antitumor agent.

A number of substituted isoquinolin-1-ones, possible bioisosteres of the 5-aryl substituted 2,3-dihydroimidazo[2,1-a]isoquinolines, were synthesized and tested for their antitumor activity against five different human tumor cell lines. O-(3-hydroxypropyl) substituted compound (15) exhibited the best antitumor activity which is 3-5 times better than 5-[4'-(piperidinomethyl) phenyl]-2,3-dihydroimidazo[2,1-a]isoquinoline (1).

Antineoplastic Agents↗
PubMed1998

Studies of structure activity relationship of flavonoids for the anti-allergic actions.

The structure activity relationship of flavonoids for anti-allergic actions was studied by determining the IC50 values for the degranulation. The hexosaminidase release from RBL-2H3 cells (degranulation marker) was employed as an estimate for the anti-allergic actions. Among 22 flavonoid compounds tested, luteolin, apigenin, diosmetin, fisetin, and quercetin were found to be most active with IC50 values less than 10 microM.

Animals↗
PubMed1998

Synthesis and comparative molecular field analysis (CoMFA) of antitumor 3-arylisoquinoline derivatives.

In this study a series of 3-arylisoquinoline derivatives were synthesized and cytotoxicity against human melanoma tumor cell evaluated, and a three dimensional quantitative structure-activity relationship was investigated using the comparative molecular field analysis (CoMFA). The results suggested that the electrostatic, steric and hydrophobic factors of 3-arylisoquinolines were strongly correlated with the antitumor activity. Considerable predictive ability (cross-validated r2 as high as 0.721) was obtained through CoMFA.

Antineoplastic Agents↗
PubMed1995

Antitumor activity of 5-aryl-2,3-dihydroimidazo[2,1-a]isoquinolines.

A series of 5-aryl-2,3-dihydroimidazo[2,1-a]isoquinolines previously reported to be platelet activating factor (PAF) receptor antagonists were evaluated for potential antitumor activity. Several compounds, such as the 5-(4'-tert-butylphenyl) (65), 5-[4'-(trimethylsilyl)phenyl] (69), and 5-(4'-cyclohexylphenyl) (71) analogs showed very good cytotoxicity against several tumor cell lines. 5-[4'-(Piperidinomethyl)phenyl]-2,3-dihydroimidazo[2,1- a]isoquinoline (SDZ 62-434, 53) was more effective on a milligram per kilogram basis than the clinical cytostatic agent edelfosine (1) in increasing survivors and decreasing tumor volume in the oral mouse Meth A fibrosarcoma assay. It was selected for further development and is currently in phase I clinical trials in cancer patients.

Animals↗
PubMed1994

Differential effects of intrathecally injected galanin on antinociception induced by beta-endorphin and morphine administered intracerebroventricularly in mice.

The effects of intrathecal (i.t.) and intracerebroventricular (i.c.v.) treatments with galanin on inhibition of the tail-flick and paw-licking hot-plate responses induced by beta-endorphin and morphine administered i.c.v. were studied in ICR mice. Galanin (100 ng) given i.t. effectively antagonized inhibition of the tail-flick response induced by i.c.v. administered beta-endorphin (1 microgram) but not morphine (1 microgram). However, the same dose of galanin given i.t. did not affect inhibition of the hot-plate response induced by beta-endorphin and morphine administered i.c.v. Intrathecal treatment with various doses of galanin (0.1-100 ng) dose-dependently antagonized the inhibition of the tail-flick response induced by beta-endorphin administered i.c.v. Galanin (100 ng) in combination with beta-endorphin (1 microgram) or morphine (1 microgram) given i.c.v. did not affect beta-endorphin- or morphine-induced inhibition of the tail-flick and hot-plate responses. It is concluded that galanin given i.t. selectively attenuates i.c.v. beta-endorphin-induced inhibition of the tail-flick response by inhibiting descending epsilon-opioid system activated by supraspinally applied beta-endorphin.

Animals↗
PubMed1993

Structural modification of 5-aryl-2,3-dihydroimidazo[2,1-a]isoquinoline platelet activating factor receptor antagonists.

In an effort to determine the effect of modification of the imidazo[2,1-a]isoquinoline portion of the PAF-receptor antagonist SDZ 64-412 (1), several new analogs were prepared and evaluated in vitro and in vivo. One of these, 5-[4-[2-(3,4,5-trimethoxyphenyl)ethyl]phenyl]-2,3-dihydroimidazo [1,2-a]thieno[2,3-c]pyridine (6) was 4-5 times more potent than 1 in inhibiting PAF-induced bronchoconstriction and hemoconcentration when administered po to the guinea pig.

Animals↗