Establishment of the Meyer-Overton correlation in an artificial membrane without protein.

Background: The potency of anesthetics with various structures increases exponentially with lipophilicity, which is the Meyer-Overton (MO) correlation discovered over 120 years ago. The MO correlation was also observed with various biological effects and chemicals, including alcohols; thus, the correlation represents a fundamental relationship between chemicals and organisms. The MO correlation was explained by the lipid and protein theories, although the principle remains unknown because these are still debating.

A rapid and simple spectroscopic method for the determination of yeast cell viability using methylene blue.

Determination of cell viability is important in various microbiological studies. The microscopic method, counting dead cells stained by methylene blue (MB), has often been used for the determination of viability, although it is not efficient for the measurement of a large number of samples. Alternatively, some spectroscopic methods have been proposed to avoid tedious cell counting.

Escaping from the Cutoff Paradox by Accumulating Long-Chain Alcohols in the Cell Membrane.

The mechanism for the cutoff, an activity cliff at which long-chain alcohols lose their biological effects, has not been elucidated. Highly hydrophobic oleyl alcohol (C) exists as a mixture of monomers and aggregated droplets in water. C did not inhibit the yeast growth but inhibited the growth of the slime mold without a cell wall.

Antimalarial Quinacrine and Chloroquine Lose Their Activity by Decreasing Cationic Amphiphilic Structure with a Slight Decrease in pH.

Quinacrine (QC) and chloroquine (CQ) have antimicrobial and antiviral activities as well as antimalarial activity, although the mechanisms remain unknown. QC increased the antimicrobial activity against yeast exponentially with a pH-dependent increase in the cationic amphiphilic drug (CAD) structure. CAD-QC localized in the yeast membranes and induced glucose starvation by noncompetitively inhibiting glucose uptake as antipsychotic chlorpromazine (CPZ) did.

Physicochemical Solubility of and Biological Sensitivity to Long-Chain Alcohols Determine the Cutoff Chain Length in Biological Activity.

The cutoff phenomenon associated with the effectiveness of long-chain alcohols in the induction of anesthesia is also observed for various antimicrobial activities, although the mechanism has remained unknown for over eight decades. The minimum inhibitory concentrations at 25°C for budding yeast growth exponentially decreased with increasing chain length of -alcohols (C-C), whereas alcohols ≥C lost the inhibitory effect. Thus, growth inhibition by alcohols obeys the Meyer-Overton correlation up to C and exhibits a cutoff phenomenon.

Local Anesthetics and Antipsychotic Phenothiazines Interact Nonspecifically with Membranes and Inhibit Hexose Transporters in Yeast.

Action mechanisms of anesthetics remain unclear because of difficulty in explaining how structurally different anesthetics cause similar effects. In Saccharomyces cerevisiae, local anesthetics and antipsychotic phenothiazines induced responses similar to those caused by glucose starvation, and they eventually inhibited cell growth. These drugs inhibited glucose uptake, but additional glucose conferred resistance to their effects; hence, the primary action of the drugs is to cause glucose starvation.

Tetracaine, a local anesthetic, preferentially induces translational inhibition with processing body formation rather than phosphorylation of eIF2α in yeast.

It is unclear whether local anesthetics, such as tetracaine, and antipsychotics, such as phenothiazines, act on lipids or proteins. In Saccharomyces cerevisiae, these drugs inhibit growth, translation initiation, and actin polarization, and induce cell lysis at high concentrations. These activities are likely due to the cationic amphiphilic structure common to these agents.

Effects of elevated CO2 on levels of primary metabolites and transcripts of genes encoding respiratory enzymes and their diurnal patterns in Arabidopsis thaliana: possible relationships with respiratory rates.

Elevated CO2 affects plant growth and photosynthesis, which results in changes in plant respiration. However, the mechanisms underlying the responses of plant respiration to elevated CO2 are poorly understood. In this study, we measured diurnal changes in the transcript levels of genes encoding respiratory enzymes, the maximal activities of the enzymes and primary metabolite levels in shoots of Arabidopsis thaliana grown under moderate or elevated CO2 conditions (390 or 780 parts per million by volume CO2, respectively).

Mih1/Cdc25 is negatively regulated by Pkc1 in Saccharomyces cerevisiae.

Mitotic cyclin-dependent kinase (CDK) is activated by Cdc25 phosphatase through dephosphorylation at the Wee1-mediated phosphorylation site. In Saccharomyces cerevisiae, regulation of Mih1 (Cdc25 homologue) remains unclear because inactivation/degradation of Swe1 (Wee1 homologue) is the main trigger for G2/M transition. By deleting all mitotic cyclins except Clb2, a strain was created where Mih1 became essential for mitotic entry at high temperatures.

Nitrate addition alleviates ammonium toxicity without lessening ammonium accumulation, organic acid depletion and inorganic cation depletion in Arabidopsis thaliana shoots.

When ammonium is the sole nitrogen (N) source, plant growth is suppressed compared with the situation where nitrate is the N source. This is commonly referred to as ammonium toxicity. It is widely known that a combination of nitrate and ammonium as N source alleviates this ammonium toxicity (nitrate-dependent alleviation of ammonium toxicity), but the underlying mechanisms are still not completely understood.

Structural analysis of compounds with actions similar to local anesthetics and antipsychotic phenothiazines in yeast.

Local anesthetics and antipsychotic phenothiazines cause a rapid shutdown of both actin polarization and translation initiation in yeast cells, like some environmental stresses. These compounds all have an amphiphilic structure, surfactant activity and the ability to lyse yeast cells. To elucidate the structures responsible for the shutdown activity and cell lysis, we investigated a variety of amphiphiles.

Ammonium-dependent respiratory increase is dependent on the cytochrome pathway in Arabidopsis thaliana shoots.

Oxygen uptake rates are increased when concentrated ammonium instead of nitrate is used as sole N source. Several explanations for this increased respiration have been suggested, but the underlying mechanisms are still unclear. To investigate possible factors responsible for this respiratory increase, we measured the O₂ uptake rate, activity and transcript level of respiratory components, and concentration of adenylates using Arabidopsis thaliana shoots grown in media containing various N sources.

Effects of AOX1a deficiency on plant growth, gene expression of respiratory components and metabolic profile under low-nitrogen stress in Arabidopsis thaliana.

Expression of alternative oxidase (AOX) and cyanide (CN)-resistant respiration are often highly enhanced in plants exposed to low-nitrogen (N) stress. Here, we examined the effects of AOX deficiency on plant growth, gene expression of respiratory components and metabolic profiles under low-N stress, using an aox1a knockout transgenic line (aox1a) of Arabidopsis thaliana. We exposed wild-type (WT) and aox1a plants to low-N stress for 7 d and analyzed their shoots and roots.

Environmental stresses and clinical drugs paralyze a cell.

Cells respond and adapt to various extracellular changes. Environmental stresses, such as high osmolarity and acute glucose deprivation, rapidly and transiently shut down translation initiation and actin polarization in the yeast Saccharomyces cerevisiae. Certain clinical drugs, such as local anesthetics and antipsychotic phenothiazines, and cationic surfactants also cause shutdowns similar to those triggered by environmental stresses.

Local anesthetics, antipsychotic phenothiazines, and cationic surfactants shut down intracellular reactions through membrane perturbation in yeast.

High osmolarity and glucose deprivation cause rapid shutdowns of both actin polarization and translation initiation in yeast. Like these stresses, administration of local anesthetics and of antipsychotic phenothiazines caused similar responses. All these drugs have amphiphilic structures and formed emulsions and permeabilized the cell membrane, indicating that they have the same features as a surfactant.

LAS24/KOG1, a component of the TOR complex 1 (TORC1), is needed for resistance to local anesthetic tetracaine and normal distribution of actin cytoskeleton in yeast.

It is known that some local anesthetics inhibit the growth of budding yeast cells. To investigate the pathway of local anesthetics' action, we isolated and characterized mutants that were hyper-sensitive to tetracaine, and at the same time, temperature-sensitive for growth. They were collectively called las (local anesthetic sensitive) mutants.

Simultaneous yet independent regulation of actin cytoskeletal organization and translation initiation by glucose in Saccharomyces cerevisiae.

Acute glucose deprivation rapidly but transiently depolarizes the actin cytoskeleton and inhibits translation initiation in Saccharomyces cerevisiae. Neither rapid actin depolarization nor translation inhibition upon glucose removal occurs in a reg1 disruptant, which is defective in glucose repression, or in the tpk1(w) mutant, which has weak cAPK activity. In the absence of additional glucose, recovery of either actin polarization or translation initiation relies upon respiration, the Snf1p protein kinase, and the transcription factors Msn2p and Msn4p.

Transient inhibition of translation initiation by osmotic stress.

Cells respond and adapt to changes in the environment. In this study, we examined the effect of environmental stresses on protein synthesis in the yeast Saccharomyces cerevisiae. We found that osmotic stress causes irreversible inhibition of methionine uptake, transient inhibition of uracil uptake, transient stimulation of glucose uptake, transient repression of ribosomal protein (RP) genes such as CYH2 and RPS27, and the transient inhibition of translation initiation.