Transport protein synthesis in non-growing yeast cells

Addition of a metabolizable substrate (glucose, ethanol and, to a degree, trehalose) to non-growing baker's yeast cells causes a boost of protein synthesis, reaching maximum rate 20 min after addition of glucose and 40–50 min after ethanol or trehalose addition. The synthesis involves that of transport proteins for various solutes which appear in the following sequence: H⁺, l-proline, sulfate, l-leucine, phosphate, α-methyl-d-glucoside, 2-aminoisobutyrate. With the exception of the phosphate transport system, the K_t of the synthesized systems is the same as before stimulation. Glucose is usually the best stimulant, but ethanol matches it in the case of sulfate and exceeds it in the case of proline. This may be connected with ethanol's stimulating the synthesis of transport proteins both in mitochondria and in the cytosol while glucose acts on cytosolic synthesis alone. The stimulation is often repressed by ammonium ions (leucine, proline, sulfate, H⁺), by antimycin (proline, trehalose, sulfate, H⁺), by iodoacetamide (all systems tested), and by anaerobic preincubation (leucine, proline, trehalose, sulfate). It is practically absent in a respiration-deficient petite mutant, only little depressed in the op₁ mutant lacking ADP/ATP exchange in mitochondria, but totally suppressed (with the exception of transport of phosphate) in a low-phosphorus strain. The addition of glucose causes a drop in intracellular inorganic monophosphate by 30%, diphosphate by 45%, ATP by 70%, in total amino acids by nearly 50%, in transmembrane potential (absolute value) by about 50%, an increase of high-molecular-weight polyphosphate by 65%, of total cAMP by more than 100%, in the endogenous respiration rate by more than 100%, and a change of intracellular pH from 6.80 to 7.05. Ethanol caused practically no change in ATP, total amino acids, endogenous respiration, intracellular pH or transmembrane potential; a slight decrease in inorganic monophosphate and diphosphate and a sizeable increase in high-molecular-weight polyphosphate. The synthesis of the various transport proteins thus appears to draw its energy from different sources and with different susceptibility to inhibitors. It is much more stimulated in facultatively aerobic species (Saccharomyces cerevisiae, Endomyces magnusii) than in strictly aerobic ones (Rhodotorula glutinis, Candida parapsilosis) where an inhibition of transport activity is often observed after preincubation with metabolizable substrates.     

Allogibberic acid: An inhibitor of flowering in Lemna perpusilla

Allogibberic acid (I) has been identified as the compound responsible for the inhibition of flowering, increase in frond multiplication rate and decrease in frond size produced in Lemna perpusilla 6746 by autoclaved, unbuffered aqueous solutions of gibberellic acid (VII). 13-Deoxyallogibberic acid (IV), a product of autoclaving aq. GA₇ (VIII) solutions, also inhibits flowering in L. perpusilla and is about 10 times more active than allogibberic acid.     

Synthesis and bioevaluation of new tacrine-cinnamic acid hybrids as cholinesterase inhibitors against Alzheimer’s disease

Small molecule cholinesterases inhibitor (ChEI) provides an effective therapeutic strategy to treat Alzheimer’s disease (AD). Currently, the discovery of new ChEI with multi-target effect is still of great importance. Herein, we report the synthesis, structure–activity relationship study and biological evaluation of a series of tacrine-cinnamic acid hybrids as new ChEIs. All target compounds are evaluated for their in vitro cholinesterase inhibitory activities. The representatives which show potent activity on cholinesterase, are evaluated for the amyloid β-protein self-aggregation inhibition and in vivo assays. The optimal compound 19, 27, and 30 (human AChE IC₅₀?=?10.2?±?1.2, 16.5?±?1.7, and 15.3?±?1.8?nM, respectively) show good performance in ameliorating the scopolamine-induced cognition impairment and preliminary safety in hepatotoxicity evaluation. These compounds deserve further evaluation for the development of new therapeutic agents against AD.     

Novel derivatives of usnic acid effectively inhibiting reproduction of influenza A virus

Influenza virus is serious human pathogen leading to high morbidity and mortality all over the world. Due to high rate of mutation, it is able to fast development of drug resistance that makes necessary to search novel antivirals with broad range and alternative targets. In the present study we describe synthesis and anti-viral activity of novel derivatives of usnic acid (2,6-diacetyl-7,9-dihydroxy-8,9b-dimethyl-1,3(2H,9bH)-dibenzo-furandione). It is shown that anti-viral activity of usnic acid can be increased by side moieties introduction. The modification with chalcones appeared to be the most effective. Our study revealed that (−)-usnic acid exhibited higher antiviral activity than its (+)-enantiomer, but in the pairs of enantiomer derivatives such as enamines, pyrazoles and chalcones, the (+)-enantiomers were more potent inhibitors of the virus. For other groups of compounds the inhibiting activities of the enantiomers were comparable. Further optimization of the structure could therefore result in development of novel anti-influenza compound with alternative target and mechanism of virus-inhibiting action.     

Upregulation of amphiregulin by retinoic acid and Wnt signalling promotes liver cancer cell proliferation

Activated hepatic stellate cells promote hepatocellular carcinoma (HCC) progression. Hepatic stellate cells play a key role in retinoid metabolism, and activation of stellate cells increases retinoic acid (RA) in the liver. However, the role of RA in HCC proliferation remains unclear. We aimed to analyse the mechanism of RA in HCC proliferation. Thirty-eight patients who had undergone hepatic resection for HCCs were recruited. Paired non-tumour tissues, adjacent and distal to HCCs, were collected, and the RA levels in the tissues were analysed. The mechanisms of RA and HCC proliferation were assessed in liver cancer cell lines by protein and gene expression analyses. Early recurrence of HCC was significantly higher in patients with a higher RA concentration than in those with a lower RA concentration in tissues adjacent to HCCs (61.1% vs. 20%, p = .010). RA promoted HCC cell proliferation and activated the expression of Amphiregulin, a growth factor in hepatocarcinogenesis. The promoter of Amphiregulin contained the binding sites of the RA receptor, RXRα. Wnt signalling also activated the expression of Amphiregulin, and the RA and Wnt pathways acted synergistically to increase the expression of Amphiregulin. Furthermore, RXRα interacted with β-catenin and then translocated to the nucleus to activate Amphiregulin. An increased RA concentration in the tissues adjacent to the tumour was associated with an early recurrence of HCC. RA activated the expression of Amphiregulin, and then promoted HCC proliferation, which might partly contribute to early recurrence of HCC after hepatic resection.     

The effect of buffers and chelators on the reaction of luminol with Fenton's reagent near neutral pH

The chemiluminescence of the system luminol +Fe²⁺ + H₂O₂ was measured in aqueous buffer at pH 7.2. In veronal (5,5-diethybarbiturate) buffer, the luminescence is strongly quenched by ethanol and mannitol, but only weakly by t-butanol, benzoate and superoxide dismutase (SOD); complexing Fe²⁺ with 1,10-phenanthroline or 2,2′-dipyridyl causes a decrease of light production that can be partially obviated by the simultaneous addition of SOD. In phosphate buffer, the luminescence is higher than in veronal and it is efficiently quenched by all four OH · quenchers and by SOD. In Tris buffer, no light production is observed as long as the Fe²⁺ is not complexed. When Fe²⁺ is complexed by pyrophosphate or phytate, there is a strong chemiluminescence in all three buffers, which is quenched by all four OH · quenchers and by SOD. When Fe²⁺ is complexed by EDTA or DTPA, very little luminescence is observed. The luminol analogue phthalhydrazide, which was suggested by Merényi and Lind as a reliable OH · detector, can replace luminol only in phosphate buffer, and thus turns out to be very specific indeed for free OH ·.