PubMed Health⌕ Search

Biomedical subjects

S Ro

Publications and source records attributed to S Ro.

At least 19 recordsLinked to original sources
PubMed2001

A novel class of highly potent, selective, and non-peptidic inhibitor of Ras farnesyltransferase (FTase).

Design, synthesis and structure-activity relationship of a class of aryl pyrroles as farnesyltransferase inhibitors are described. In vitro and in vivo evaluation of a panel of these inhibitors led to identification of 2 (LB42908) as a highly potent (IC(50)=0.9 nM against H-Ras and 2.4 nM against K-Ras) antitumor agent that is currently undergoing preclinical studies.

Alkyl and Aryl Transferases↗
PubMed2001

TREK-1 regulation by nitric oxide and cGMP-dependent protein kinase. An essential role in smooth muscle inhibitory neurotransmission.

Potassium channels activated by membrane stretch may contribute to maintenance of relaxation of smooth muscle cells in visceral hollow organs. Previous work has identified K(+) channels in murine colon that are activated by stretch and further regulated by NO-dependent mechanisms. We have screened murine gastrointestinal, vascular, bladder, and uterine smooth muscles for the expression of TREK and TRAAK mRNA. Although TREK-1 was expressed in many of these smooth muscles, TREK-2 was expressed only in murine antrum and pulmonary artery. TRAAK was not expressed in any smooth muscle cells tested. Whole cell currents from TREK-1 expressed in mammalian COS cells were activated by stretch, and single channel recordings showed that the stretch-dependent conductance was due to 90 pS channels. Sodium nitroprusside (10(-6) or 10(-5) m) and 8-Br-cGMP (10(-4) or 10(-3) m) increased TREK-1 currents in perforated whole cell and single channel recordings. Mutation of the PKG consensus sequence at serine 351 blocked the stimulatory effects of sodium nitroprusside and 8-Br-cGMP on open probability without affecting the inhibitory effects of 8-Br-cAMP. TREK-1 encodes a component of the stretch-activated K(+) conductance in smooth muscles and may contribute to nitrergic inhibition of gastrointestinal muscles.

Animals↗
PubMed2001

Novel voltage-dependent non-selective cation conductance in murine colonic myocytes.

1. Two components of voltage-gated, inward currents were observed from murine colonic myocytes. One component had properties of L-type Ca(2+) currents and was inhibited by nicardipine (5 x 10(-7) M). A second component did not 'run down' during dialysis and was resistant to nicardipine (up to 10(-6) M). The nicardipine-insensitive current was activated by small depolarizations above the holding potential and reversed near 0 mV. 2. This low-voltage-activated current (I(LVA)) was resolved with step depolarizations positive to -60 mV, and the current rapidly inactivated upon sustained depolarization. The voltage of half-inactivation was -65 mV. Inactivation and activation time constants at -45 mV were 86 and 15 ms, respectively. The half-recovery time from inactivation was 98 ms at -45 mV. I(LVA) peaked at -40 mV and the current reversed at 0 mV. 3. I(LVA) was inhibited by Ni(2+) (IC(50) = 1.4 x 10(-5) M), mibefradil (10(-6) to 10(-5) M), and extracellular Ba(2+). Replacement of extracellular Na(+) with N-methyl-D-glucamine inhibited I(LVA) and shifted the reversal potential to -7 mV. Increasing extracellular Ca(2+) (5 x 10(-3) M) increased the amplitude of I(LVA) and shifted the reversal potential to +22 mV. I(LVA) was also blocked by extracellular Cs(+) (10(-4) M) and Gd(3+) (10(-6) M). 4. Warming increased the rates of activation and deactivation without affecting the amplitude of the peak current. 5. We conclude that the second component of voltage-dependent inward current in murine colonic myocytes is not a 'T-type' Ca(2+) current but rather a novel, voltage-gated non-selective cation current. Activation of this current could be important in the recovery of membrane potential following inhibitory junction potentials in gastrointestinal smooth muscle or in mediating responses to agonists.

Action Potentials↗
PubMed2001

Torsion angle based design of peptidomimetics: a dipeptidic template adopting beta-I turn (Ac-Aib-AzGly--NH(2)).

We have attempted to design a model dipeptide (acetyl dipeptide amide, Ac-CA1-CA2--NH(2)) that can adopt specifically typical torsion angles of the beta-I turn (phi(i+1), psi(i+1), phi(i+2), psi(i+2)=-60 degrees, -30 degrees, -90 degrees, 0 degrees ). The key of the design is the combination of constrained amino acids that prefer to adopt the desired torsion angles. We chose Aib (aminoisobutyric acid) as the first residue of which phi and psi angles must be -60 degrees and -30 degrees, respectively. Then, we selected an azaamino acid as the second residue since previous studies have indicated that they prefer to adopt +/-90 degrees of phi angle and 0 degrees or 180 degrees of psi angle. The conformational preference of the resulting Ac-Aib-AzGly--NH(2) is investigated using ab initio methods. The conformations implying beta-I and beta-I' turns are energetically most favorable, as we expected. Thus, we synthesized the designed molecule on the solid phase considering the future generation of combinatorial libraries using an automatic peptide synthesizer. Then, NMR spectroscopy was carried out to confirm their conformational preference in solution was carried out. The results indicated that the Ac-Aib-AzGly--NH(2) adopt beta-I or beta-I' turns in solution forming an intramolecular hydrogen bonding between Ac--C(O) and terminal NH(2). We believe that such a small peptidomimetic template is highly useful for the design of drug candidates and molecular devices.

Dipeptides↗
PubMed2001

Molecular properties of small-conductance Ca2+-activated K+ channels expressed in murine colonic smooth muscle.

Small-conductance Ca2+-activated K+ (SK) channels are important participants in inhibitory neurotransmission in gastrointestinal smooth muscles. Three isoforms of an SK channel family were cloned from murine proximal colon smooth muscle. The transcripts encoding these subunits (SK1, SK2, and SK3) were detected in murine proximal colon and other peripheral tissues. The mRNA of each subunit was expressed at different levels in murine and canine colonic smooth muscles. The mRNA quantitative ratio of SK transcriptional expression in murine proximal colon is SK2 > SK3 > SK1; transcriptional expression of SK isoforms in canine proximal colon is minimal. SK3 immunohistochemical localization in murine small intestine (jejunum) and proximal colon showed immunoreactivity in circular and longitudinal muscularis. In transversely sectioned muscularis, staining was localized at the cell membrane in smooth muscle cells. Immunoreactivity was more intense in myenteric ganglia between longitudinal and circular muscularis and neuronal processes in circular and longitudinal muscularis. Transient expression of mSK1, mSK2, and mSK3 in COS cells resulted in Ca2+-activated voltage-independent channels. mSK1 is less sensitive to apamin compared with SK2 and showed intracellular Ca2+ sensitivity (10(-8) to 10(-6) M) in asymmetrical K+ (5/140 mM K+) gradients. Our results suggest that SK channel expression varies in colonic myocytes from different species and may contribute differentially to inhibitory junction potentials.

Amino Acid Sequence↗
PubMed2000

Dynamic hemicarcerands and hemicarceplexes.

The reversible nature of the imine bond formation in CDCl(3) solution has been exploited to exchange substituted for unsubstituted m-phenylenediamine (MPD) units in hemicarcerand octaimines. Moreover, acid-catalyzed imine exchange has been shown to provide a novel mechanism whereby ferrocene (Fc) can be released as an entrapped guest from the hemicarceplex C(2)B(4)&crcldt;Fc dissolved in CDCl(3) to give the hemicarcerand C(2)B(4) when excess of both MPD and trifluoroacetic acid are present.

Ethers, Cyclic↗
PubMed2000

Role of azaamino acid residue in beta-turn formation and stability in designed peptide.

The structural perturbation induced by C(alpha)-->N(alpha) exchange in azaamino acid-containing peptides was predicted by ab initio calculation of the 6-31G* and 3-21G* levels. The global energy-minimum conformations for model compounds, For-azaXaa-NH2 (Xaa=Gly, Ala, Leu) appeared to be the beta-turn motif with a dihedral angle of phi= +/- 90 degrees, psi=0 degrees. This suggests that incorporation of the azaXaa residue into the i+2 position of designed peptides could stabilize the beta-turn structure. The model azaLeu-containing peptide, Boc-Phe-azaLeu-Ala-OMe, which is predicted to adopt a beta-turn conformation was designed and synthesized in order to experimentally elucidate the role of the azaamino acid residue. Its structural preference in organic solvents was investigated using 1H NMR, molecular modelling and IR spectroscopy. The temperature coefficients of amide protons, the characteristic NOE patterns, the restrained molecular dynamics simulation and IR spectroscopy defined the dihedral angles [ (phi i+1, psi i+1) (phi i+2, psi i+2)] of the Phe-azaLeu fragment in the model peptide, Boc-Phe-azaLeu-Ala-OMe, as [(-59 degrees, 127 degrees) (107 degrees, -4 degrees)]. This solution conformation supports a betaII-turn structural preference in azaLeu-containing peptides as predicted by the quantum chemical calculation. Therefore, intercalation of the azaamino acid residue into the i+2 position in synthetic peptides is expected to provide a stable beta-turn formation, and this could be utilized in the design of new peptidomimetics adopting a beta-turn scaffold.

Aza Compounds↗
PubMed2000

Water extract of Helicobacter pylori stimulates interleukin-8 secretion by a human gastric epithelial cell line (JR-St) through protein tyrosine phosphorylation.

BACKGROUND: Infection by Helicobacter pylori induces cytokine production in gastric mucosal cells. Production of interleukin-8 (IL-8) is known to be markedly increased and is believed to play an important role in gastric mucosal inflammation. The aim of this study was to elucidate the effects of soluble factors of H. pylori on IL-8 production in a gastric epithelial cell line, JR-St. METHODS: JR-St cells were cocultured with a H. pylori water extract, live H. pylori or culture medium supernatant for 24 h, then the IL-8 secreted into the culture medium was assayed. The effects of three different inhibitors; (i) an inhibitor of protein kinase C (PKC); (ii) an inhibitor of PKC and protein kinase A (PKA); and (iii) an inhibitor of protein tyrosine kinase (PTK) were also compared. Specific induction of IL-8 mRNA was also examined. RESULTS: Water extract of H. pylori increased IL-8 secretion 7.72-fold, more than the control. The increase was concentration dependent. Live bacteria, supernatant and water extract significantly stimulated IL-8 secretion. Addition of live bacteria increased IL-8 secretion most strongly, while the effect of water extract was small (22% that of live bacteria). Secretion was not inhibited by the PKC inhibitor staurosporine or the inhibitors of PKA and PKC H7. However, secretion was significantly reduced by the PTK inhibitor herbimycin in a dose-dependent manner. Furthermore, 24 h exposure to water extract increased IL-8 mRNA expression, suggesting water extract increased production of IL-8. CONCLUSIONS: Some soluble factors of H. pylori can stimulate IL-8 production by JR-St cells. Stimulation was not dependent on PKA or PKC but was, at least partially, dependent on protein tyrosine phosphorylation. This suggests that soluble factors of H. pylori can play an important role in mediating the inflammatory response of H. pylori gastritis.

Bacterial Proteins↗
PubMed2000

[Drug sensitivity, conjugative R plasmids and plasmid profiles of Salmonella isolated from humans with infectious enteritis].

Using 92 Salmonella strains isolated from patients suspected of having infectious diseases of the intestinal tract who visited 13 hospitals in Japan during the six years between 1991 and 1996, we investigated the drug susceptibility, prevalence of conjugative R plasmid, and the plasmid profiles. 1) Of the bacterial isolates tested, 52.2% showed drug-resistance. Regarding the drug-resistance patterns, 70.8% of the isolates were resistant to a single drug, while 29.2% were multi drug-resistant. 2) Dividing the resistance patterns by the serotypes, among Salmonella Enteritidis isolates, single-drug resistance to SM was the most frequent, being detected in 27 isolates. Single-drug resistance to NA and two-drug resistance to SM/TC were the second-most frequent, each being detected in isolates. Among Salmonella Hadar isolates, four isolates showed two-drug resistance to SM/TC, and one isolate showed single-drug resistance to TC. Among Salmonella Typhimurium isolates, one isolate each showed three-drug resistance to ABPC/CER/KM and KM/TC/CP. Among Salmonella Agona isolates, one isolate each showed two-drug resistance to SM/TC and single-drug resistance to SM. Among Salmonella Derby isolates, two isolates showed single-drug resistance to SM. 3) The prevalence of conjugative R plasmid was investigated in 48 drug-resistant isolates, and six isolates (12.5%) contained the plasmid. 4) The prevalence of the plasmid was investigated in 29 drug-resistant S. Enteritidis isolates, and 22 isolates (75.9%) contained the plasmid. These isolated were classified by the plasmid profiles into types H1 to H7. 5) Regarding the plasmid profiles of the S. Enteritidis isolates, a position corresponding to 60 Kbp was the most frequently detected in 90.5%.

Anti-Bacterial Agents↗
PubMed1999

Increased serum levels and sinusoidal expression of thrombomodulin in acute liver damage.

Thrombomodulin (TM) is a surface glycoprotein of endothelial cells involved in both anticoagulation and antifibrinolysis. In this study, we assessed the clinical significance of TM in acute liver damage by using a rat model induced by intraperitoneal injection of D-galactosamine (Gal-N). Serum TM levels were measured with enzyme immunoassay utilizing rabbit anti-rat TM antibody. Simultaneously, immunohistochemical examination was performed using the same antibody. Serum TM levels increased significantly after the injection of Gal-N compared with preinjection levels, peaking from 48 to 72 hours after injection and normalizing by 168 hours. Changes in parenchymal damage were synchronized with changes of TM, and changes of TM levels mirrored changes of liver weight. In immunohistochemical examination, TM immunoreactivity was observed only on the endothelial surfaces of both the artery and portal vein within Glisson's sheath in controls. After injection of Gal-N, TM immunoreactivity was gradually intensified, especially around the necrotic area and the central veins. These findings disappeared with improvement of parenchymal damage. Both the increase of serum TM levels and intensified TM immunoreactivity in the liver were synchronized with acute liver parenchymal damage induced by Gal-N. These findings on TM are related to endothelial damage with parenchymal necrosis and liver regeneration interacting with both homeostasis of microcirculation and healing of parenchymal damage.

Acute Disease↗
PubMed1999

Stimulatory effect of growth in the presence of alcohols on biotransformation of penicillin G into cephalosporin-type antibiotics by resting cells of Streptomyces clavuligerus NP1.

Growth of Streptomyces clavuligerus NP1 in the presence of methanol or ethanol resulted in a marked increase in production of cephalosporin(s) from penicillin G by resting cells. The mycelium produced in alcohol-supplemented medium was fragmented and dispersed as compared with growth in control medium. HPLC analysis showed that at least two products were present in the biotransformation supernatant fluid after 1 h incubation. One of them has been identified as deacetoxycephalosporin G (DAOG).

Alcohols↗
PubMed1999

Concentrations of C-reactive protein in normal monkeys (Macaca irus) and in monkeys inoculated with Bordetella bronchiseptica R-5 and measles virus.

The concentrations of C-reactive protein (CRP) in serum from normal crab-eating monkeys (Macaca irus) were measured by means of a monkey-specific turbidimetric immunoassay (TIA), and the changes in the serum CRP concentrations in crab-eating monkeys inoculated with Bordetella bronchiseptica R-5 and measles virus (Ichinose or NK 3 strain) were also examined. The CRP concentrations in sera from 54 normal crab-eating monkeys ranged from 0 to 8.3 microg/ml (mean 2.2 +/- 1.9). No significant difference was found in the CRP concentrations between males and females (p > 0.05). The concentrations of CRP in the sera from four crab-eating monkeys inoculated intrabronchially with 10(9) live B. bronchiseptica increased gradually to a peak at 2 days after inoculation. The peak concentrations of CRP were from 102.4 to 313.2 microg/ml, 54-96 times the preinoculative values of 1.9-5.6 microg/ml. When the same four crab-eating monkeys were inoculated intrabronchially with measles virus 34 days after inoculation of B. bronchiseptica, the serum CRP concentrations did not increase. Monitoring of CRP is useful for assessing monkeys with acute B. bronchiseptica infection and will probably be of value in the diagnosis of other bacterial infections.

Animals↗
PubMed1999

Conformational studies of irreversible HIV-1 protease inhibitors containing cis-epoxide as an amide isostere.

We have carried out NMR and molecular modeling studies of peptidomimetic HIV-1 protease inhibitors, LB71116: Qc-Asn-Phepsi[(1R,2S)-cis-epoxide]Gly-NH-CH(isopropyl)2 where Qc stands for quinaldic acid and LB71148: Qc-(SMe)Pen(O)2-Phepsi[(1R,2S)-cis-epoxide]Gly-NH-CH(isoprop yl)2 where (SMe)Pen(O)2 stands for S-methyl-S-dioxo-penicillamine. Through conformational calculations and NMR data analysis, we have obtained preferred conformations of the two inhibitors in solution. To our knowledge, this work is one of the first extensive conformational studies of peptidomimetics containing cis-epoxide amide isostere. The resulting preferred conformations contain extended structures. In these conformations, the psi of Phe(cep) is maintained about 130 degrees and the phi angle of (cep)Gly prefers +/- 150 degrees [where Phe(cep) and (cep)Gly are the residues generated by the replacement of the Phe-Gly peptide bond with cis-epoxide]. Two conformations were commonly observed in the preferred conformations of each inhibitor. Through restrained molecular dynamics simulating the hydrogen bond formation between our inhibitor and a water molecule ('flap water'), one of the conformations is assumed as the conformation which can bind to the enzyme without large conformational changes. Recently, we had the opportunity to compare the selected preferred conformation with the binding conformation of LB71116 observed from the X-ray studies of the complex between LB71116 and HIV-1 protease. These two conformations are surprisingly similar to each other. Thus, we can explain high activity and selectivity of our inhibitors to the HIV-1 protease by the similarity between the preferred conformations in solution and the binding conformation.

Amides↗
PubMed1998

Solution and solid phase combinatorial synthesis of peptidomimetic library containing diversified alpha-methylated amino acids.

A combinatorial peptidomimetic library containing diversified alpha-methylated amino acids was generated by the Ugi four component condensation (4cc) reaction from acids, amines, isocyanides and ketones in both solution and solid phase synthetic procedures. This one-pot methodology overall gave fair to good yields, which compare well with multi-step syntheses.

Amino Acids↗
PubMed1998

Interleukin-8 enhances tetragastrin-stimulated acid secretion in vivo.

Recent studies have demonstrated a relationship between cytokines and gastric acid secretion. However, details of the mechanism underlying that relationship have not been elucidated. For this study, an in vivo experiment was undertaken to investigate the possibility that IL-8 would be involved in the mechanism of gastric acid secretion. Gastric lumen-perfused rats were prepared and the stomachs were perfused with a saline solution. The effluent was collected at 15-min intervals and assayed for titratable acid against 0.01 M NaOH. IL-8 (200 ng/rat) given intravenously did not influence basal acid output in rats. However, when IL-8 was administered by injection during continuous tetragastrin infusion (4 microg/kg/hr) acid output increased significantly (P < 0.01). The acid output during the first hour following IL-8 injection was 43.6% higher than prior to the injection. Acid output during the second hour was lower than during the first hour. However, successive injection of IL-8 again increased tetragastrin-stimulated acid output by 23.4% (P < 0.05). IL-8 injection did not change histamine-stimulated acid output. The results indicate that IL-8 has the effect of enhancing gastrin-stimulated acid secretion and might have an important role in the pathophysiology of gastric acid secretion in vivo.

Animals↗