Structure-based specificity mapping of secreted aspartic proteases of Candida parapsilosis, Candida albicans, and Candida tropicalis using peptidomimetic inhibitors and homology modeling

Secreted aspartic proteases (Saps) of pathogenic Candida spp. represent a specific target for antifungal drug development. We synthesized a series of peptidomimetic inhibitors with different isosteric groups and modifications at individual positions and tested them with purified Saps from C. albicans (Sap2p), C. tropicalis (Sapt1p), and C. parapsilosis (Sapp1p). The kinetic parameters indicated that all three proteases prefer binding of inhibitors containing bulky hydrophobic residues between positions P3 and P3'. The most divergent specificity was found for Sapp1p. The sequence alignment of Sap2p, Sapt1p, and Sapp1p, and homology modeling of Sapp1p with the crystal structure of Sapt1p and the complex of Sap2p with a peptidomimetic inhibitor showed that the overall folds of Sap2p, Sapt1p, and Sapp1p are similar. However, the N- and C-terminal loops formed by disulfide bonds between residues 47-53 and 258-292 are significantly shorter in Sapp1p, and a unique insertion following Tyr 129 in Sapp1p results in the formation of a loop that can interact with inhibitor residues. These Sapp1p structural differences might lead to its altered susceptibility to inhibition.     

Molecular Analysis of Endoplasmic Reticulum Stress Response After Global Forebrain Ischemia/Reperfusion in Rats: Effect of Neuroprotectant Simvastatin

Simvastatin is a cholesterol-lowering agent whose functional significance and neuroprotective mechanism in ischemic brain injury is not yet solved. The purpose of this study is to evaluate the effect of simvastatin on ischemic brain injury. We examined the endoplasmic reticulum stress response (UPR/unfolded protein response), by measuring the mRNA and protein levels of specific genes such as ATF6, GRP78, and XBP1 after 15 min 4-VO ischemia and different times of reperfusion (1, 3, and 24 h). The results from the group of naïve ischemic rats were compared with results from the group of pre-treated animals with simvastatin. The results of the experiments showed significant increase in all genes at the mRNA level in ischemic phase (about 43% for XBP1, 58% for GRP78, and 39% for ATF6 more than control). The protein level of XBP1 was decreased in pre-treated animals at ischemic phase and first hour of reperfusion (about 15% less), and did not reach control levels. The protein levels of GRP78 were maximal at third hour of reperfusion in statin group with a small decrease at 24 h of reperfusion in both groups. The levels of ATF6 mRNA in statin-treated animals was higher in comparison to non-statin animals at the ischemic phase and the third hour of reperfusion (about 35% higher), which was also translated into the higher protein level. This could indicate that one of the main proteins targeted to enhance neuroprotective effect to ER during the first two hours of reperfusion was ATF6 protein, the levels of which were 60% higher than in non-treated animals. These data suggest that simvastatin, in addition to the proposed neuroprotective effect, exerts a neuroprotective role in the attenuation of ER stress response after acute ischemic/reperfusion insult.     

Neural network comparing two-rate-encoded inputs entering in parallel

Presented computational model of a neural network is able to compare two regular input frequencies. The comparison is based on detection of inter-spike interval differences of the two frequencies. This detection is continuous and the network dynamically changes its output according to the changes in the input frequencies. The entire network is composed of biologically plausible parts. A combination of such simple comparators might be involved in the information processing in the central nervous system.     

Quantitative relationships between structure and antimicrobial activity of new “Soft” bisquaternary ammonium salts

New surface-active bisquaternary ammonium salts derived from bis-(2-dimethylaminoethyl) ester of glutaric acid are highly effective against representatives of Gram-positive, Gram-negative bacteria and yeasts. Relationships between structure, lipophilicity and antimicrobial effectiveness were demonstrated by quantitative structure-activity methodology. The nonlinear dependence of biological activity on the structure as well as lipophilicity (expressed as critical micelle concentration—CMC) was shown using Kubinyi’s bilinear model. The most effective compounds were those with the alkyl chain of 11–12 carbon atoms and with the CMC values around 0.7−1.0 mmol/L. These derivatives possessed higher antimicrobial activity particularly to Gram-negative bacteria. Part 45 of the seriesQuaternary Ammonium Salts; part 44: Brádlerová A.et al., Pharmazie, in press.     

Degradation of bromoxynil by resting and immobilized cells of Agrobacterium radiobacter 8/4 strain

The Agrobacterium radiobacter 8/4 strain capable of degradation of bromoxynil, ioxynil and dichlobenil, arylnitrile herbicides was isolated from soil and cell entrapment was investigated. Three immobilization techniques was used: Caalginate, Ca-pectate and -carrageenan technique, and resting cells. The highest degradation rates were obtained with Ca-alginate and -carrageenan entrapped cells.     

Fungicides cytotoxicity expressed in male gametophyte development in Brassica campestris after in vitro application of converted field doses

A simple method to determine the toxicity of fungicides on male gametophyte in Brassica campestris subsp. oleiferae is described. The calculation of fungicide concentration used in the test is derived from doses used in field application. The expression of regression curves and calculation of regression equations require the logarithmic transformation of fungicide concentration. The range of the sensitivity of the method is very wide. The minimal concentration detected as significantly different from control ranges from 1.7 to 7.0 pg of the active compound. Fungicides declared as non-toxic for plants in field tests were cytotoxic for male gametophyte development. The synergistic action of more than one active compound resulted in higher toxicity.     

Some implications of the short-term synaptic plasticity for neuronal computation: a model study

Spikes arriving at the synaptic connection produce short-term plastic changes of the synaptic efficacy. Model experiments have shown that paired-pulse facilitation attaining its maximum after a specific interval between a pair of arriving spikes might turn a “weak” plastic synapse attached to an integrate-and-fire neuron to a frequency-tuned device. Resulting computational capabilities create biologically plausible mechanisms of information processing relating to: (i) real-time identification of temporal patterns in a stream of random spiking activity (a recognition problem); and (ii) codetermination of the specific activity routing among neurons (an addressing problem) resulting in definite spatio-temporal patterns of the output activity (an input-output pattern problem).     

Isoquinoline Alkaloids from Fumaria officinalis L. and Their Biological Activities Related to Alzheimer's Disease

Two new isoquinoline alkaloids, named fumaranine ( 2 ) and fumarostrejdine ( 10 ), along with 18 known alkaloids were isolated from aerial parts of Fumaria officinalis. The structures of the isolated compounds were elucidated on the basis of spectroscopic analyses and by comparison with literature data. The absolute configuration of the new compound 2 was determined by comparing its circular dichroism spectra with those of known analogs. Compounds isolated in sufficient amounts were evaluated for their acetylcholinesterase, butyrylcholinesterase, prolyl oligopeptidase (POP), and glycogen synthase kinase‐3β inhibitory activities. Parfumidine ( 8 ) and sinactine ( 15 ) exhibited potent POP inhibition activities (IC₅₀ 99±5 and 53±2 μM , resp.).