Synthesis of 9-deoxo-4''-deoxy-6,9-epoxyerythromycin derivatives: novel and acid-stable motilides

In our quest toward the discovery of highly potent and acid-stable motilides, novel 4"-deoxy derivatives of 9-deoxo-6, 9-epoxyerythromycin were designed, synthesized, and evaluated for their gastrointestinal prokinetic activities. These compounds, in their 9R configuration, were more potent than their 6,9-enol ether homologues in inducing well-coordinated smooth muscle contractions in an in vitro rabbit duodenal assay: e.g., (9R), (8S)-9-deoxo-4"-deoxy-3'-N-desmethyl-3'-N-ethyl-6, 9-epoxyerythromycin A (10) and (9R), (8S)-9-deoxo-4"-deoxy-3'-N-desmethyl-3'-N-ethanol-6, 9-epoxyerythromycin A (15) had a pED50 of 8.54 and 8.11 compared to a pED50 of 7.22 for compound 2 (ABT-229). Reduction of the 6,9-enol ether, which was aimed at improving the acid stability, afforded the most stable motilides to date with t1/2 of 5.5 h for 10 and 15. Compounds 10 and 15 bind specifically to rabbit antral smooth muscle motilin receptors with pIC50 values of 8.52 and 8.70.

Synthesis and evaluation of 2-amino-9-(3-hydroxymethyl-4-alkoxycarbonyloxybut-1-yl)purines as potential prodrugs of penciclovir

A series of 2-amino-9-(3-hydroxymethyl-4-alkoxycarbonyloxybut-1-yl)purines (4-10) and 2-amino-9-(2-(2-oxo-1,3-dioxan-5-yl)ethyl)purine (1) were synthesized as potential prodrugs of penciclovir and evaluated for their oral penciclovir bioavailability in mice and rats. Treatment of 2-(2-benzyloxyethyl)propane-1,3-diol (11) with 1,1'-carbonyldiimidazole in THF followed by hydrogenolytic removal of the benzyl group of the resulting cyclic carbonate 12 gave 5-(2-hydroxyethyl)-1,3-dioxan-2-one (13). Mesylation of the alcohol 13 and then a coupling reaction of the resulting mesylate 14 with 2-amino-6-chloropurine using anhydrous Cs2CO3 in DMF afforded 2-amino-6-chloro-9-(2-(2-oxo-1,3-dioxan-5-yl)ethyl)purine (16) after purification by flash column chromatography on silica gel using EtOAc/MeCN/Et3N as eluent. Hydrogenation of the 6-chloro cyclic carbonate 16 followed by a ring-opening reaction of the 6-deoxy cyclic carbonate 1 in a mixture of an appropriate alcohol and CHCl3 using activated SiO2 as a Lewis acid afforded the corresponding alkyl monocarbonate derivatives 3-10 in fair to good yields. Of the prodrugs tested in mice, the isopropyl monocarbonate 6 achieved the highest mean urinary recovery of penciclovir (53%), followed in order by the propyl monocarbonate 5 (51%), the isopentyl monocarbonate 10 (51%), the ethyl monocarbonate 4 (50%), and famciclovir (48%). In rats, the methyl monocarbonate 3, 4, 6, the n-butyl monocarbonate 7, and 10 (39-41%) showed levels of mean urinary recovery of penciclovir similar to that from famciclovir (40%). The alkyl monocarbonates 4-10 were found to be quite stable in the aqueous buffer solutions, and among them, 6 was the most stable with the half-lives (t1/2) of 88, >200, 61, and 26 days at pH 1.2, 6.0, 7.4, and 8.0, respectively. In addition, 6 was highly soluble in H2O (138.8 mg/mL, 20 degrees C).

Enhancement of the wavelength selectivity of a volume hologram by use of multimode optical fiber referencing

Wavelength multiplexing of a volume hologram was combined with multimode fiber referencing. A photorefractive volume hologram was recorded and probed by reference light diffracted from a multimode optical fiber. A tunable laser diode was used as a light source that was launched into the multimode fiber. As the wavelength of the source laser shifted, the speckle patterns from the multimode fiber changed. The wavelength selectivity of the volume hologram was enhanced by the combined effect of wavelength change and speckle change.

Obliteration of the pulmonary vein in lung cancer: significance in assessing local extent with CT

PURPOSE

The purpose of this study was to evaluate the significance of obliteration of the pulmonary vein in assessing local extent of lung cancer with CT, particularly in regard to intrapericardial extension of tumor through the vein.

METHOD

Preoperative CT scans of 325 patients, who underwent thoracotomy for primary lung cancer, were reviewed. Among them, CT scans of 19 patients showed obliteration of the pulmonary vein up to its entrance into the left atrium, without filling defect in the left atrium. Surgical records of these patients were then reviewed to investigate the extent of tumor growth through the pulmonary vein, with particular emphasis on intrapericardial extension.

RESULTS

The surgical records revealed extension of tumor through the pulmonary vein beyond the pericardial reflection in 14 or 19 patients. In 10 patients showing obliteration of either the left of the right superior pulmonary vein, all tumors extended beyond the pericardial reflection (100%). Intrapericardial extension occurred in four of nine patients showing obliteration of either the left or the right inferior pulmonary vein (44%). The difference was statistically significant (p < 0.05).

CONCLUSION

When assessing local extent of lung cancer with CT, obliteration of the superior pulmonary vein is a highly suggestive finding for intrapericardial extension of tumor through the pulmonary vein. On the contrary, obliteration of the inferior pulmonary vein is believed to be a less reliable finding for intrapericardial extension of lung cancer.

Characterization of tTA and its functional domain in tetracycline repressor-mediated gene repression system

To elucidate of role(s) of tTA as a repressor in the tTA-mediated gene repression system, we introduced mutations into the acidic domain of VP16 and examined the effects of such various mutations. In the transient repression experiment, a region containing 34 amino acids of the activation domain of VP16 (412-456) which interacts with TFIIB was found to be necessary and sufficient for the tTA-mediated repression of gene expression. However, in the experiment to investigate the fact that tTA-regulated repression is related to the activation function of VP 16, we found that the repression abilities of tTA derivatives did not correlate exactly with their activation abilities. Therefore, we conclude that increased mass of VP16 in tTA might be also important for efficient repression in addition to functional domain of VP16.

Pulse-amplitude-equalized output from a rational harmonic mode-locked fiber laser

We report, for the first time to our knowledge, the demonstration of amplitude equalization of high-repetition-rate pulses generated from a rational harmonic mode-locked Er-doped fiber laser. The output pulses are injected into another fiber laser with a nonlinear optical loop mirror. This scheme provides pulse-amplitude equalization up to the ninth rational harmonic mode-locked pulse train.

Benign solitary fibrous tumour of the pre-sacral space: MRI findings

Benign solitary fibrous tumour, a rare mesenchymal tumour of adults, usually arises from the pleura. Only a few cases have been reported in the retroperitoneum and, to our knowledge, there has been no report of its imaging features. We describe the MRI features of benign solitary fibrous tumour arising from the pre-sacral space.

Use of the Center for Epidemiologic Studies Depression (CES-D) Scale in Korea

We translated the Center for Epidemiologic Studies Depression (CES-D) Scale into Korean, paying careful attention to culturally different modes of expression of depressive feelings and thoughts. The final translated version (CES-D-K) was administered to 164 psychiatric patients and 464 normal subjects residing in the community. Reliability, validity, and the optimal cutoff point of this scale were estimated, including ROC analysis. The CES-D-K was reliable and valid for the Korean population. Two optimal cutoff points were suggested: 24/25, the point which best corresponded to the clinical diagnosis of depression, and 20/21, which most effectively detects and covers depressive symptoms during screening. The higher cutoff points than those in Western countries may be due to different ways of expression affect, especially the suppression of positive affect, in cultures based on Confucian ethics.

Role of nitric oxide in oxidative damage in isolated rabbit gastric cells exposed to hypoxia-reoxygenation

The present study aimed to investigate the role of nitric oxide on the oxidative damage in isolated rabbit gastric cells exposed to hypoxia-reoxygenation. Nitric oxide synthesis modulators such as L-arginine and NG-nitro-L-arginine methyl ester, a nitric oxide donor, sodium nitroprusside, and superoxide dismutase were used to treat the cells, and the synthesis and secretion of mucus, lipid peroxide production, and glutathione contents of the cells were determined. As a result, hypoxia-reoxygenation decreased nitric oxide production and the synthesis and secretion of mucus, as well as glutathione contents of gastric cells, but hypoxia-reoxygenation increased lipid peroxide production. Pretreatment with L-arginine, a substrate for nitric oxide synthase, sodium nitroprusside, and superoxide dismutase prevented the increase in lipid peroxide production and the decreases in glutathione contents, as well as the synthesis and secretion of mucus induced by hypoxia-reoxygenation. However, NG-nitro-L-arginine methyl ester, a nitric oxide synthase inhibitor, had no effect on these alterations. In conclusion, nitric oxide has an antioxidant defensive role on gastric cells by maintaining mucus and glutathione.

Expression of germ cell nuclear factor (GCNF/RTR) during spermatogenesis

Germ cell nuclear factor (GCNF/RTR), a novel orphan receptor in the nuclear receptor superfamily of ligand-activated transcription factors, is expressed predominantly in developing germ cells. In several mammalian species two GCNF/RTR mRNAs are present in the testis, with the smaller 2.3-kb transcript generally expressed at higher levels than the larger 7.4- or 8.0-kb transcript. In both the mouse and rat, the 2.3- and 7.4-kb GCNF/RTR transcripts were detected in isolated spermatogenic cells, but not in Sertoli cells. Expression of these transcripts is differentially regulated, with the larger 7.4-kb mRNA appearing earlier during testicular development. The major 2.3-kb transcript is expressed predominantly in round spermatids in the mouse and rat. In situ hybridization studies in the rat demonstrated that GCNF/RTR transcripts reach maximal steady-state levels in round spermatids at stages VII and VIII of the spermatogenic cycle, and then decline abruptly as spermatids begin to elongate. RNase protection assays were used to predict the 3' termination site of the 2.3-kb transcript. An alternative polyadenylation signal (AGUAAA) was identified just upstream of this termination site. These studies suggest that GCNF/RTR may regulate transcription during spermatogenesis, particularly in round spermatids just prior to the initiation of nuclear elongation and condensation.

Coupled column chromatography in chiral separation of salmeterol

A coupled achiral-chiral high-performance liquid chromatographic system has been developed for the determination of the enantiomers of salmeterol, S-(+)-salmeterol and R-(-)-salmeterol in urine. The salmeterol was separated from the interfering components in urine and quantified on the silica column, and the enantiomeric composition was determined on a Sumichiral OA-4700 chiral stationary phase. The two columns were connected by a switching valve equipped with a silica precolumn. The precolumn was used to concentrate the salmeterol in the eluent from the achiral column before backflushing onto the chiral phase. The coupled system was validated.

Resolution of salbutamol enantiomers in human urine by reversed-phase high performance liquid chromatography after derivatization with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate

A stereospecific HPLC method has been developed for the resolution of the enantiomers of salbutamol in human urine. After solid-phase extraction and derivatization with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate, the diastereomeric derivatives were resolved (Rs = 1. 83) on 5 microns octadecylsilan column using 35% acetonitrile in 0.05 M ammonium acetate buffer (pH = 6) as a mobile phase with electrochemical detection. The diastereomeric derivatives were formed within 30 min. The detection limit of each enantiomer was 20 ng/ml (S/N = 3).

delta-Endotoxin proteins associated with spherical parasporal inclusions of the four Lepidoptera-specific Bacillus thuringiensis strains

Four Lepidoptera-specific reference strains of Bacillus thuringiensis, belonging to serovars sumiyoshiensis (H3a:3d), fukuokaensis (H3a:3d:3e), darmstadiensis (H10a:10b) and japonensis (H23), which produce spherical parasporal inclusions, were examined for comparative characterization of delta-endotoxins. SDS-PAGE profiles of the alkali-solubilized parasporal inclusions revealed the presence of single major protein bands of 130 kDa in the four strains. Chymotrypsin and trypsin treatment of the proteins gave profiles different from those of the strains HD-1 (serovar kurstaki, H3a:3b:3c) and T84 A1 (serovar sotto, H4a:4b). Also, minor variations were observed in proteolysis profiles among the four strains. The LC50 values of purified parasporal inclusions for the silkworm (Bombyx mori) larvae were 7.35, 6.45, 3.08 and 2.63 micrograms g-1 diet, respectively, showing that their toxicity levels were 5-15 times lower than that of the strain HD-1 (0.49 microgram g-1 diet). Analysis by immunodiffusion and immunoblotting with polyclonal antisera revealed that parasporal inclusion proteins of the four strains are highly related, whereas they shared few or no common antigens with those of the strains HD-1, T84 A1 and Buibui (serovar japonensis).

Molecular and serologic survey of Orientia tsutsugamushi infection among field rodents in southern Cholla Province, Korea

Field rodents were collected from six areas in southern Cholla Province, Korea from October to December 1993. Twenty-eight (24%) of the 119 Apodemus agrarius were seropositive (> 1:10) for Orientia tsutsugamushi by the passive hemagglutination assay (PHA). Of the seropositive cases, 11 specimens had antibody titers greater than 1:80. No seropositive specimens were found among the eight Crocidura lasiura collected. On the other hand, the polymerase chain reaction (PCR) amplified about 520 basepairs of a gene encoding the 56-kD protein from the genomic DNA of 12 strains of O. tsutsugamushi tested. This target DNA sequence was amplified from the 11 (8.7%) blood specimens of A. agrarius, and one of the eight C. lasiura also showed evidence of O. tsutsugamushi infection by PCR. Only one of the PCR-positive samples was also PHA-positive. These results suggest that the PCR combined with a serologic assay more accurately detects the degree of infection of rodents with rickettsiae-causing scrub typhus in epidemiologic surveys.

Determination of encephalomyocarditis viral diabetogenicity by a putative binding site of the viral capsid protein

The molecular mechanism by which some, but not all, variants of encephalomyocarditis (EMC) virus selectively infect pancreatic beta-cells in mice and induce IDDM has been an enigma for more than a decade. We report here that the binding site of the EMC viral capsid protein VP1 determines viral diabetogenicity. Recombinant chimeric EMC viruses containing threonine, serine, proline, aspartic acid, or valine at position 152 of the major capsid protein VP1 bind poorly to beta-cells. In contrast, recombinant chimeric EMC viruses containing alanine or glycine at position 152 of the VP1 bind efficiently to and infect beta-cells, resulting in the development of diabetes. Three-dimensional molecular modeling reveals that the van der Waals interactions are greater and the residues surrounding position 152 of the VP1 are more closely packed in recombinant chimeric viruses containing threonine, serine, proline, aspartic acid, or valine at position 152 than in recombinant chimeric viruses containing alanine or glycine at the same position. Our studies reveal that the surface areas surrounding alanine or glycine at position 152 of the VP1 are more accessible, thus increasing the availability of the binding sites for attachment to beta-cell receptors and resulting in viral infection and the development of diabetes.

Expression, purification, and characterization of choline kinase, product of the CKI gene from Saccharomyces cerevisiae

In the yeast Saccharomyces cerevisiae, choline kinase (ATP:choline phosphotransferase, EC 2.7.1.32) is the product of the CKI gene. Choline kinase catalyzes the committed step in the synthesis of phosphatidylcholine by the CDP-choline pathway. The yeast enzyme was overexpressed 106-fold in Sf-9 insect cells and purified 71.2-fold to homogeneity from the cytosolic fraction by chromatography with concanavalin A, Affi-Gel Blue, and Mono Q. The N-terminal amino acid sequence of purified choline kinase matched perfectly with the deduced sequence of the CKI gene. The minimum subunit molecular mass (73 kDa) of purified choline kinase was in good agreement with the predicted size (66.3 kDa) of the CKI gene product. Native choline kinase existed in oligomeric structures of dimers, tetramers, and octomers. The amounts of the tetrameric and octomeric forms increased in the presence of the substrate ATP. Antibodies were raised against the purified enzyme and were used to identify choline kinase in insect cells and in S. cerevisiae. Maximum choline kinase activity was dependent on Mg2+ ions (10 mM) at pH 9.5 and at 30 degrees C. The equilibrium constant (0.2) for the reaction indicated that the reverse reaction was favored in vitro. The activation energy for the reaction was 6.26 kcal/mol, and the enzyme was labile above 30 degrees C. Choline kinase exhibited saturation kinetics with respect to choline and positive cooperative kinetics with respect to ATP (n = 1.4-2.3). Results of the kinetic experiments indicated that the enzyme catalyzes a sequential Bi Bi reaction. The Vmax for the reaction was 138.7 micromol/min/mg, and the Km values for choline and ATP were 0.27 mM and 90 microM, respectively. The turnover number per choline kinase subunit was 153 s-1. Ethanolamine was a poor substrate for the purified choline kinase, and it was also poor inhibitor of choline kinase activity. ADP inhibited choline kinase activity (IC50 = 0.32 mM) in a positive cooperative manner (n = 1.5), and the mechanism of inhibition with respect to ATP and choline was complex. The regulation of choline kinase activity by ATP and ADP may be physiologically relevant.

The bisbenzylisoquinoline alkaloids, tetrandine and fangchinoline, enhance the cytotoxicity of multidrug resistance-related drugs via modulation of P-glycoprotein

The occurrence of resistance to chemotherapeutic drugs is a major problem for successful cancer treatment and reducing drug accumulation by P-glycoprotein (P-gp) is one of the major mechanisms of multidrug resistance (MDR). The present study was performed to evaluate the MDR-reversal abilities of two bisbenzylisoquinoline alkaloids, tetrandine (TET) and fangchinoline (FAN), compared with verapamil (VER), a well-known P-gp modulator. TET (3.0 microM), FAN (3.0 microM) and VER (10.0 microM) reduced the paclitaxel (TAX) concentration required to achieve 50% inhibition of cell growth (EC50) to HCT15 (P-gp-positive) cells about 3100-, 1900- and 410-fold, and these compounds also reduced the EC50 value of actinomycin D (AMD) about 36.0-, 45.9- and 18.2-fold in the cells, respectively. Meanwhile, TET, FAN and VER had no effect on the cytotoxicity of the drugs to SK-OV-3 (P-gp-negative) cells. On the other hand, TET (3.0 microM), FAN (3.0 microM) and VER (10.0 microM) similarly enhanced the accumulation rates of rhodamine 123, a well known P-gp substrate, in HCT15 cells (200-250%). After efflux for 2 h with fresh medium, TET and FAN also enhanced the residual rate of rhodamine 123 about 5.0- and 2.6-fold in comparison with control, respectively. TET, FAN and VER could not affect the accumulation and residual rate of rhodamine 123 in SK-OV-3 cells. From the result, we conclude that TET and FAN enhanced the cytotoxicity of MDR-related drugs via modulation of P-gp.

Acoustic emission signals from gypsum-bonded dental casting molds during thermal processing

To develop a suitable heating program for the investments which affect the casting accuracy/defects of prostheses, a probable microstructural change of the gypsum-bonded investments related to the transition of refractory particles during thermal processing was inspected by the measurement of acoustic emission (AE) signals. Gypsum-bonded cristobalite and quartz investment molds were used. AE measurements were carried out for the specimens in an electric furnace that was heated/cooled at a constant rate. For the heating process of the cristobalite investment, high AE activities were detected in the temperature range where the cristobalite was transformed. However, the AE signals detected were low for the second run of the heating and cooling processes. Even in the heating process, significant AE signals were not detected for the quartz investment. For cristobalite investment molds, micro-cracks are initiated and developed in relation to the transition of cristobalite particles in the mold. This leads to deterioration of the mechanical properties of the cristobalite investment at high temperatures (melt-pouring), and may affect the fitness of cast prostheses.

Ligand-dependent regulation of retinoic acid receptor alpha in rat testis: in vivo response to depletion and repletion of vitamin A

Male animals are sterile due to testicular degeneration in the absence of retinoic acid (RA) or functional retinoic acid receptor-alpha (RAR alpha). This degeneration can be reversed by injecting retinol, a precursor of RA, into vitamin A-deficient (VAD) rats. To determine the relationship between this ligand-dependent testicular degeneration and regeneration and the expression levels of RAR alpha messenger RNA and protein, testes were depleted and then replenished with retinol in vivo. Results showed that RAR alpha messenger RNA and protein levels declined to VAD amounts after 7 weeks on a VAD diet. This decline was due to decreased RAR alpha levels in early meiotic spermatocytes and the loss of advanced germ cells. Interestingly, the advanced germ cells still contained RAR alpha, but the protein was primarily cytoplasmic instead of nuclear, indicating inactivity as a transcription factor. In VAD testis, RAR alpha levels were low and then increased primarily in Sertoli cells after retinol replenishment. TUNEL analyses showed that most germ cells at the basal aspect of seminiferous tubules were undergoing apoptosis during degeneration. These results indicate that RAR alpha is either down-regulated or inactivated in RA-deficient testis and coincident with that, testes degenerate by apoptosis or selective loss of germ cells.

Acidic polysaccharide from Panax ginseng, ginsan, induces Th1 cell and macrophage cytokines and generates LAK cells in synergy with rIL-2

We previously reported that an acidic polysaccharide from Panax ginseng named ginsan inhibits the incidence of benzo[a]pyrene-induced autochthonous lung tumors in mice. To elucidate the mechanism of antineoplastic activity, ginsan was tested for its ability to generate LAK cells and to produce cytokines. Spleen cells became cytotoxic to a wide range of tumor cells after 5 days of culture with ginsan in a non-major histocompatibility restricted manner and the activity of ginsan was 12 times higher than that of lentinan. The generation of killer cells by rIL-2 was neutralized only in the presence of anti-IL-2, whereas by ginsan it was neutralized in the presence of anti-IL-2 as well as anti-IFN gamma, or anti-IL-1 alpha. It was confirmed that ginsan induces the expression of mRNA for IL-2, IFN gamma, IL-1 alpha, and GM-CSF. Depletion of AsGM1+ cells from spleen cells reduced the generation of LAK by rIL-2. In contrast, depletion of AsGM1+ as well as Thy1+ cells, CD4+ cells, or DC8+ cells reduced the generation of LAK cells by ginsan. The serologic phenotype of rIL-2 induced LAK cells was CD8- cells, whereas the ginsan induced LAK cells, were CD8+ cells. Ginsan synergized with rIL-2 to generate LAK cells (2.0-15 fold) and the most dramatic synergy was seen at rIL-2 concentrations below 3 U/ml. Ginsan alone inhibited pulmonary metastasis of B16-F10 melanoma cells and enhanced the inhibition of lung colonies by rIL-2. These findings demonstrate that ginsan generates LAK cells from both NK and T cells through endogeneously produced multiple cytokines. This property may contribute to its effectiveness in the immunoprevention and immunotherapy of cancer.

Sonographic versus endoscopic retrograde cholangiographic measurements of the bile duct revisited: importance of the transverse diameter

OBJECTIVE

The purpose of this study was to investigate how frequently the cross section of the bile duct is oval versus round on sonography and whether the transverse diameter of the bile duct (DTRV) on sonography corresponds better than the conventional anteroposterior diameter (DAP) to measurements on endoscopic retrograde cholangiography (ERC).

SUBJECTS AND METHODS

In 44 consecutive patients with a DAP greater than or equal to 8 mm, DTRV was measured on short-axis sonograms. Diameter of the bile duct measured on ERC (DERC) was compared with DAP and DTRV in patients who underwent ERC shortly after sonography.

RESULTS

The cross section of the bile duct was oval in 31 patients (70%). In 20 patients who underwent ERC after sonography, mean DERC was statistically indistinguishable from mean DTRV but statistically different from mean DAP. Comparing both DAP and DTRV with DERC in each patient, we found no statistically significant difference between DERC and DTRV, but we did find a statistically significant difference between DERC and DAP.

CONCLUSION

An oval cross section is common in bile ducts with a DAP greater than or equal to 8 mm. The discrepancy between measurements of the bile duct made sonographically and those made on ERC is largely attributable to different cross-sectional diameters. Because DTRV correlates better than conventional DAP with DERC, measurement of DTRV can be helpful in confirming or excluding true biliary dilatation in patients with a DAP larger than normal.

Neuromuscular interactions between mivacurium and esmolol in rabbits

We compared the dose-response relationship and the neuromuscular blocking effects of mivacurium during infusions of esmolol in 40 anaesthetised rabbits. Train-of-four stimuli were applied every 10 s to the common peroneal nerve and the force of contraction of the tibialis anterior muscle was measured. Plasma cholinesterase activity decreased by 13% after esmolol infusion. The ED95 of mivacurium increased significantly from 29 (4.8) micrograms.kg-1 with placebo to 61 (9.8) micrograms.kg-1 during esmolol 100 micrograms.kg-1.min-1, 49 (8.2) micrograms.kg-1 during esmolol 300 micrograms.kg-1.min-1 and 54 (7.3) micrograms.kg-1 during esmolol 500 micrograms.kg-1.min-1, respectively (p < 0.001). The duration of neuromuscular block with mivacurium 0.16 mg.kg-1 was prolonged by 30% with esmolol due to diminished plasma cholinesterase activity (p < 0.05). Heart rate and mean arterial blood pressure decreased by 15% with esmolol (p < 0.05). The results of this study show that, in rabbits, esmolol decreased plasma cholinesterase activity, antagonised the neuromuscular blocking potency of mivacurium and prolonged its neuromuscular blocking effect.

Reversal of multidrug resistance by novel verapamil analogs in cancer cells

The present study was performed to evaluate the ability of KR-30032 and KR-30035 to overcome multidrug resistance (MDR) by measuring the cytotoxicity and the accumulation rate of rhodamine. Additionally, the adverse cardiac toxicity of KR-30032 and KR-30035 was evaluated by measuring the changes of tension in isolated rat aorta and left ventricular pressure (LVP) in guinea pig heart. KR-30035 potentiated the paclitaxel-induced cytotoxicity to HCT15 [P-glycoprotein (P-gp)-expressed cells] to over 15-fold greater than that of verapamil and KR-30032 was equipotent with verapamil (EC50: 0.07, 5.0 and 3.3 nM at 1.0 microg/ml). KR-30032 and KR-30035 were without effect on cytotoxicity to SK-OV-3 cells (P-gp-non-expressing cells), as well as to tamoxifen-induced cytotoxicity in the above cell types. Maximal rhodamine accumulation rates with KR-30032, KR-30035 and verapamil were 290, 291 and 271% in HCT15 cells; and 451, 970 and 440% in HCT15/CL02 cells, respectively. KR-30032 and KR-30035 were 20- to 25-fold less potent than verapamil in relaxing aorta (EC50: 8.13, 6.40 and 0.32 microM, respectively) and were 12- to 35-fold less potent than verapamil in decreasing LVP in isolated hearts (EC50: 41.8, 14.1 and 1.2 microM, respectively). The results of this study suggest that KR-30032 and KR-30035 are active modulators of MDR with potentially minimal cardiovascular toxicity.

The causative organisms of bacterial meningitis in Korean children, 1986-1995

Bacterial meningitis remains a serious cause of morbidity and mortality in childhood. Epidemiologic investigations have shown variability in disease risks among different populations and races. In Korea, however, basic epidemiologic information on bacterial meningitis in children is limited. The main purpose of this study was to analyze bacteriologically proven meningitis cases in terms of the relative frequency of causative organisms, mortality rate, and age distribution beyond the neonatal period. Data was obtained from the hospital records who had been diagnosed with bacterial meningitis at 13 general or university hospitals from 1986 through 1995. The patients had at least one positive CSF culture for bacteria. Of 140 cases of CSF culture-proven bacterial meningitis, 46.4% was < or =1 year, 62.1% was < or =2 years, 81.4% was < or =5 years cumulatively. Streptococcus pneumoniae was the most common bacteria responsible for 48 (35.0%) of all cases regardless of age, followed by Haemophilus influenzae for 48 (34.3%) and Neisseria meningitidis for 8 (6.4%) patients. The case fatality rate was 20.0%, 17.1%, and 16.7% for N. meningitidis, S. pneumoniae, and H. influenzae, respectively. In conclusion, the most common organisms of culture-proven bacterial meningitis in the last 10 years have been S. pneumoniae, H. influenzae, and N. meningitidis in order of frequency. Further study should be extended to nation-wide epidemiologic evaluation to show the incidence of bacterial meningitis caused by these three important organisms.

Effects of t-butyl hydrogen peroxide on single SR calcium release channels

Using lipid bilayer reconstitution technique, we investigated the oxidation effect of t-butyl hydrogen peroxide (tBHP) on the single channel activity of the sarcoplasmic reticulum (SR) calcium release channels isolated from canine latissimus dorsi muscles. When 0.7% tBHP was added in the cytosolic side, the channel activity became suppressed (n = 7), and it was recovered by changing the solution to the control solution. The suppression was due to the change in the gating mode of the channel: before tBHP the channel opened to four sub-conductance levels, but it opened to only one level after tBHP. These effects by tBHP were different from the previous finding using hydrogen peroxide (H2O2), which may be explained by different oxidation patterns between the two oxidants.