Mechanism of Candida albicans transformation in response to changes of pH

Hyphal growth of Candida albicans was observed at neutral condition, whereas the yeast growth was increased below pH 5. Eight out of 12 strains of C. albicans grow in hyphal form at pH 7, and hyphal formation was inhibited in all strains at pH 4. The addition of GMP, an alternative oxidase (AOX) activator, induced the hyphal growth at pH 4. Although C. albicans grew in hyphal form in pH 7, SHAM, an AOX inhibitor, enhanced the yeast proliferation at this pH. The relative expression level of RAS1 mRNA was higher at pH 7 than at pH 4, indicating that the hyphal formation signal was defective under acidic conditions. Based on these findings, we concluded that AOX-RAS1 signal transduction is the main pathway of hyphal formation of C. albicans, and that the signal was controlled by pH condition.     

Effects of antifungal drugs on proliferation signals in Candida albicans

The sensitivity of Candida albicans to antifungal drugs when cultured under aerobic and anaerobic conditions was measured. Ciclopirox olamine and siccanin were more effective under aerobic than under anaerobic conditions. Terbinafine, neticonazole and amphotericin B showed the same antifungal activity under both aerobic and anaerobic conditions. None of these antifungal activities were affected by the pH conditions. Terbinafine inhibited the elongation of hyphae, while neticonazole and amphotericin B induced proliferation of the yeast form. The expression of RAS1, EFG1 and CPH1 mRNAs was inhibited by these drugs. These results suggested that the inhibition of hyphal formation might be caused by disruption of the RAS1-signal pathway.     

Analysis of the factors associated with drugs remaining in the Diskhaler following inhalation of fluticasone propionate

Because it is well known that drug remains in the fluticasone propionate Diskhaler (FP-DH) following a single inhalation, the following patient information is recommended. "Please inhale more than once or twice if any drug remains in the device after inhalation". It is believed the inspiratory flow rate of the individual patient has an influence on the amount of drug that remains in the device. If the dosing performance of FP-DH is dependent on inspiratory effort, establishment of a method of inhalation that makes it independent of inspiratory flow rate is important in clinical practice. In the present study, we investigated the influence of various methods of inhalation of drug remaining in the FP-DH. No significant differences were observed regarding the drug remaining in the device among the inhalation times examined (range, 0.5-2.5 s) or the number of inhalations (range, 1-3 times). On the other hand, the amount of drug remaining in the device did decrease by tapping the device before the second inhalation. The results suggest that the amount of drug remaining in the device can be decreased by tapping the device after the first inhalation if the patient's inspiratory flow rate is low.     

Cholinesterase activity of motor end plate in human skeletal muscle

The activity and properties of cholinesterase of the motor end plate in human intercostal muscle were studied in the isolated muscle membrane. This preparation was used because cholinesterase activity of the membrane preparation was localized in the motor end plate without contamination of cholinesterase of other muscle components. Under the experimental conditions, cholinesterase in a human end plate hydrolyzed 1.21 x 10(8) molecules of acetylcholine per msec, which is smaller than hydrolysis of 2.69 x 10(8) by a motor end plate of rat intercostal muscle. Studies with cholinesterase inhibitors and specific substrates indicated that about 90% of cholinesterase of human motor endplates is acetylcholinesterase, and about 10% is pseudocholinesterase. The end plate cholinesterase had an optimal pH of 7.8 and a Michaelis-Menten constant of 4.15 mmoles/liter, and was stable at 4 degrees C for at least 4 wk. Motor end plates were estimated to contain only about 2% of the total cholinesterase activity of human intercostal muscle, compared with about 20% in rat tibialis anterior muscle. The difference is due to the lower cholinesterase activity of the motor end plate and higher cholinesterase activity of non-end plate components in human muscle than in rat muscle. The isolated muscle membrane provides a useful preparation for the study of the properties of motor end plate in human skeletal muscle.     

Theoretical consideration of drug distribution kinetics in a noneliminating organ: Comparison between a “homogeneous (well-stirred)” model and “nonhomogeneous (tube)” model

Drug distribution kinetics in a noneliminating organ or tissue has been mathematically examined. The homogeneous (well-stirred) model regards the noneliminating organ or tissue as a homogeneous compartment in which the drug is equilibrated with that in the blood leaving the organ or tissue. The nonhomogeneous (tube) model views the noneliminating organ or tissue as comprising a number of parallel cylindrical tubes containing binding sites distributed homogeneously along these tubes. These two models are examined, considering the pseudo-distribution equilibrium phase after bolus injection and a linear binding condition. Although both models predict a similar tissue distribution under a variety of conditions, significant differences exist in the predictions of various pharmacokinetic parameters as a function of the drug distribution, such as blood flow, organ volume, slope of the terminal phase, and the tissue-to-blood partition coefficients. The predictability and limitations of these two models are explored. Distribution characteristics of the two models are also examined for adriamycin, actinomycin D, tetrachlorobiphenyl, hexachlorobiphenyl, digoxin, and ethoxybenzamide; no difference is observed. It is concluded that the assumption of a homogeneous (well-stirred) compartment is suitable for describing the drug distribution kinetics of these drugs.Abstracted in part from a dissertation submitted by T.T. to the Graduate School, Division of Pharmaceutical Sciences, University of Tokyo, Tokyo, Japan, in partial fulfillment of the Doctor of Philosophy degree requirements.     

Enhancing effect of thoracotomy and/or laparotomy on the development of the lung metastases in rats after intravenous inoculation of tumor cells

To evaluate the effect of operative stress on the tumor growth, thoracotomy and/or laparotomy were performed 48 hours after the inoculation of Sato lung cancer cells in Donryu rats. The survival time, the number of metastatic foci on the surface of the lung and the per cent-area of metastatic foci in the frontal section through the pulmonary hilus were observed. Thoracotomy and laparothoracotomy reduced significantly the survival time as compared with the control but no significant difference was found between the two test groups subjected to operative stress. The number and percent-area of metastatic foci found were inversely related to the length of the survival time. Supported in part by Grants-in Aid from the Ministry of Education, Science and Culture and the Ministry of Health and Welfare.     

Involvement of Ras/extracellular signal-regulated kinase, but not Akt pathway in risedronate-induced apoptosis of U937 cells and its suppression by cytochalasin B

Although risedronate, a nitrogen containing bisphosphonate (BPs), strongly inhibits bone resorption by enhanced apoptosis of osteoclasts, its mechanism remained unclear. In this study, we investigated the molecular mechanism of risedronate-induced apoptosis of U937 cells, with a focus on extracellular signal-regulated kinase 1/2 (ERK 1/2) and protein kinase B (Akt) pathways, mitochondria-mediated apoptosis, and the effect of disruption of the actin cytoskeleton. Risedronate facilitated the relocation of Ras from membrane to cytosol through inhibited isoprenylation. Accordingly, risedronate suppressed the phosphorylation of ERK 1/2, a downstream survival signaling kinase of Ras, affected the intracellular distribution of Bcl-xL, and induced the mitochondrial membrane depolarization, cytochrome c release, activated caspase cascade and DNA fragmentation. The risedronate-induced apoptosis was effectively suppressed with cyclosporine A plus trifluoperazine, potent inhibitors of mitochondrial membrane permeability transition (MPT). The risedronate-induced apoptosis was independent of Akt, another cAMP-dependent survival signaling kinase. Risedronate facilitated dephosphorylation of Bad at Ser112, an ERK phosphorylation site, but not at Ser136, an Akt phosphorylation site. All of these apoptosis-related changes induced by risedronate were strongly suppressed by cytochalasin B, an inhibitor of actin filament polymerization. These results indicate that risedronate-induced apoptosis in U937 cells involves Ras/ERK, but not Akt signaling pathway, and is dependent on MPT, and that disruption of the actin cytoskeleton inhibits the risedronate-induced apoptosis at its early step.     

Correlations between health status and OralChroma™-determined volatile sulfide levels in mouth air of the elderly

Dimethyl sulfide (DMS), a volatile sulfur compound (VSC) found in mouth air, is thought to be associated with systemic diseases; this in contrast to the two other VSCs found in mouth air: hydrogen sulfide and methyl mercaptan (MM). This study aimed to validate the relationship between DMS in mouth air and oral and systemic factors. The subjects were 393 elderly Japanese volunteers participating in an oral and systemic health survey. They were surveyed for the concentration of VSC components in their mouth air and for their oral and systemic health status. Using logistic regression models, the prevalence of DMS in mouth air above the organoleptic threshold level (OTL) was found to be significantly associated with high-density lipoprotein (HDL) cholesterol level, medical history of colon polyps and asthma, being female, and the presence of MM in mouth air above the OTL. Our data suggest that systemic factors, such as a high serum HDL cholesterol level and a medical history of asthma and colon polyps, might be more prominent in subjects with elevated DMS. The differences, although statistically significant, are quite small. They also indicate that an oral factor, such as a high MM mouth-air level also influences the DMS mouth-air level in addition to systemic factors.     

Hyphal formation of Candida albicans is inhibited by salivary mucin

When mucin was added to Candida albicans under hyphal growth conditions, the hyphal formation was inhibited. After the 24 h incubation, the ratio of hyphal cells was 95.7+/-1.13% in the absence of mucin and no hyphal cells were observed in the presence of 1000 microg/ml mucin. The ratio of hyphal cells began to decreases at 6 h in the mucin addition group. Although mucin has antifungal activity, the concentration of mucin used in this assay did not inhibit the growth of C. albicans, indicating that the inhibition of hyphal formation was not due to the inhibition of germination by its antifungal activity. Expression of RAS1mRNA in C. albicans was inhibited by mucin. These results suggest that the inhibition of hyphal formation by mucin was caused by interruption of the hyphal formation signal of C. albicans.