Neuronal synchrony during anesthesia: a thalamocortical model

There is growing evidence in favor of the temporal-coding hypothesis that temporal correlation of neuronal discharges may serve to bind distributed neuronal activity into unique representations and, in particular, that θ (3.5-7.5 Hz) and δ (0.5 < 3.5 Hz) oscillations facilitate information coding. The θ- and δ-rhythms are shown to be involved in various sleep stages, and during anesthesia, they undergo changes with the depth of anesthesia. We introduce a thalamocortical model of interacting neuronal ensembles to describe phase relationships between θ- and δ-oscillations, especially during deep and light anesthesia. Asymmetric and long-range interactions among the thalamocortical neuronal oscillators are taken into account. The model results are compared with experimental observations. The δ- and θ-activities are found to be separately generated and are governed by the thalamus and cortex, respectively. Changes in the degree of intraensemble and interensemble synchrony imply that the neuronal ensembles inhibit information coding during deep anesthesia and facilitate it during light anesthesia.     

A revision of the species of <Emphasis Type="Italic">Saturnius</Emphasis> Manter, 1969 (Digenea: Hemiuridae), parasites of mullets (Teleostei: Mugilidae)

The genus Saturnius Manter, 1969 is defined, its species re-examined and a key to the species presented. S. overstreeti n. sp. is described from Mugil soiuy Basilewsky and M. cephalus L. from the Russian coast of the Sea of Japan and distinguished from the morphologically related S. papernai Overstreet, 1977 and S. maurepasi Overstreet, 1977. S. segmentatus Manter, 1969 is redescribed on the basis of the type- and newly collected material from M. cephalus on the Russian coast of the Sea of Japan. The morphometric variation of S. papernai is studied based on newly collected material from Liza aurata (Risso) in the Ebro Delta and off Santa Pola, Spain. The comparisons reveal lower ranges of most metrical features than previously known. A principal component analysis, carried out after adding the new data to those of Blasco-Costa et al. (2006), confirms the species identification. Other valid species recognised are S. mugilis (Yamaguti, 1970), S. maurepasi, S. belizensis Fischthal, 1977, S. dimitrovi Blasco-Costa et al., 2006 and S. minutus Blasco-Costa et al., 2006. Forms considered species inquirendae are S. valamugilis Rekharani & Madhavi, 1984, Bunocotyle constrictus Domnich & Sarabeev, 1999 [=S. papernai of Domnich & Sarabeev (2000a, b, c, d)], B. mugilis Yamaguti, 1970 of Solonchenko (1976) and S. mugilis of Dmitrieva & Gaevskaya (2001). Host and locality information is given in detail for all species. Lisa ramado (Risso) and Chelon labrosus (Cuvier) are new host records for S. papernai (sensu stricto) and S. dimitrovi. L. aurata is a new host record for S. dimitrovi and S. minutus, and L. saliens (Risso) is a new host record for S. minutus.     

Role of ionization of the phosphate cosubstrate on phosphorolysis by purine nucleoside phosphorylase (PNP) of bacterial (<Emphasis Type="Italic">E. coli</Emphasis>) and mammalian (human) origin

Kinetics of the reactions of purine nucleoside phosphorylases (PNP) from E. coli (PNP-I, the product of the deoD gene) and human erythrocytes with their natural substrates guanosine (Guo), inosine (Ino), a substrate analogue N(7)-methylguanosine (m⁷Guo), and orthophosphate (P_i, natural cosubstrate) and its thiophosphate analogue (SP_i), found to be a weak cosubstrate, have been studied in the pH range 5–8. In this pH range Guo and Ino exist predominantly in the neutral forms (pK_a 9.2 and 8.8); m⁷Guo consists of an equilibrium mixture of the cationic and zwitterionic forms (pK_a 7.0); and P_i and SP_i exhibit equilibria between monoanionic and dianionic forms (pK_a 6.7 and 5.4, respectively). The phosphorolysis of m⁷Guo (at saturated concentration) with both enzymes exhibits Michaelis kinetics with SP_i, independently of pH. With P_i, the human enzyme shows Michaelis kinetics only at pH ∼5. However, in the pH range 5–8 for the bacterial enzyme, and 6–8 for the human enzyme, enzyme kinetics with P_i are best described by a model with high- and low-affinity states of the enzymes, denoted as enzyme-substrate complexes with one or two active sites occupied by P_i, characterized by two sets of enzyme-substrate dissociation constants (apparent Michaelis constants, K _m1 and K _m2) and apparent maximal velocities (V _max1 and V _max2). Their values, obtained from non-linear least-squares fittings of the Adair equation, were typical for negative cooperativity of both substrate binding (K _m1 < K _m2) and enzyme kinetics (V _max1/K _m1 > V _max2/K _m2). Comparison of the pH-dependence of the substrate properties of P_i versus SP_i points to both monoanionic and dianionic forms of P_i as substrates, with a marked preference for the dianionic species in the pH range 5–8, where the population of the P_i dianion varies from 2 to 95%, reflected by enzyme efficiency three orders of magnitude higher at pH 8 than that at pH 5. This is accompanied by an increase in negative cooperativity, characterized by a decrease in the Hill coefficient from n _H ∼1 to n _H ∼0.7 for Guo with the human enzyme, and to n _H ∼0.7 and 0.5 for m⁷Guo with the E. coli and human enzymes, respectively. Possible mechanisms of cooperativity are proposed. Attention is drawn to the substrate properties of SP_i in relation to its structure.     

Intracellular Staphylococcus aureus employs the cysteine protease staphopain A to induce host cell death in epithelial cells

Staphylococcus aureus is a major human pathogen, which can invade and survive in non-professional and professional phagocytes. Uptake by host cells is thought to contribute to pathogenicity and persistence of the bacterium. Upon internalization by epithelial cells, cytotoxic S. aureus strains can escape from the phagosome, replicate in the cytosol and induce host cell death. Here, we identified a staphylococcal cysteine protease to induce cell death after translocation of intracellular S. aureus into the host cell cytoplasm. We demonstrated that loss of staphopain A function leads to delayed onset of host cell death and prolonged intracellular replication of S. aureus in epithelial cells. Overexpression of staphopain A in a non-cytotoxic strain facilitated intracellular killing of the host cell even in the absence of detectable intracellular replication. Moreover, staphopain A contributed to efficient colonization of the lung in a mouse pneumonia model. In phagocytic cells, where intracellular S. aureus is exclusively localized in the phagosome, staphopain A did not contribute to cytotoxicity. Our study suggests that staphopain A is utilized by S. aureus to exit the epithelial host cell and thus contributes to tissue destruction and dissemination of infection.     

The Equilibria of Lipid–K<Superscript>+</Superscript> Ions in Monolayer at the Air/Water Interface

The effect of K⁺ ion interaction with monolayers of phosphatidylcholine (lecithin, PC) or cholesterol (Ch) was investigated at the air/water interface. We present surface tension measurements of lipid monolayers obtained using a Langmuir method as a function of K⁺ ion concentration. Measurements were carried out at 22°C using a Teflon trough and a Nima 9000 tensiometer. Interactions between lecithin and K⁺ ions or Ch and K⁺ ions result in significant deviations from the additivity rule. An equilibrium theory to describe the behavior of monolayer components at the air/water interface was developed in order to obtain the stability constants and area occupied by one molecule of lipid–K⁺ ion complex (LK⁺). The stability constants for lecithin–K⁺ ion (PCK⁺) complex, \( K_{{{\text{PCK}}^{ + } }} = { 3}. 2 6\times 10^{ 2} {\text{dm}}^{ 3} \,{\text{mol}}^{ - 1} \), and for cholesterol–K⁺ ion (ChK⁺) complex, \( K_{{{\text{ChK}}^{ + } }} = { 1}.00 \times 10^{ 3} {\text{dm}}^{ 3} \,{\text{mol}}^{ - 1} \), were calculated by inserting the experimental data. The value of area occupied by one PCK⁺ complex is 60 Å² molecule^?1, while the area occupied by one ChK⁺ complex is 40.9 Å² molecule^?1. The complex formation energy (Gibbs free energy) values for the PCK⁺ and ChK⁺ complexes are ?14.18 ± 0.71 and ?16.92 ± 0.85 kJ mol^?1, respectively.     

Legionella pneumophila in Thermal Spa – Methodological Aspects of Sampling and Analysis

The aim of the study was to check the occurrence of Legionella pneumophila in thermal water and to compare different analytical methods of its determination and/or quantification used in different laboratories. The research has shown that there are noticeable differences between results from culture method, qPCR, and FISH. Significant influence on the results has got analysts qualification, samples preparation, and equipment parameters. Very important is also the homogeneousness of the samples. qPCR or FISH method can be used as a preliminary, quick study, for identification of Legionella in water samples but the results obtained should be confirmed by culture method.     

Rhipidocotyle genovi n. sp. (Digenea: Bucephalidae) from the intestine ofGaidropsarus mediterraneus (L.) (Gadiformes: Gadidae) from the Black Sea

Rhipidocotyle genovi n. sp. is described from the fishGaidropsarus mediterraneus (L.) (Gadiformes: Gadidae) in the Black Sea. Morphological features characteristic of this species include: an anterior sucker with seven prominent muscular appendages; a pharynx rather posterior in position; ovary and testes relatively anterior in position, usually anterior to the pharynx; a long (in relation to body length) sucker, cirrus-sac and excretory vesicle; the presence of a pre-oral lip; and contiguous vitelline fields which form an arch. The new species is distinguished fromR. galeata, R. lamberti andBucephalus marinum. This is the first member of the genus whose adults are recovered from Black Sea marine fishes. Metacercariae, which encyst in large numbers in the musculature and fins of the blenniid fishesBlennius tentacularis, B. sanguinolentus, B pavo, B. sphinx andB. zvonimiri and exhibit a similar morphology to the adult, are described.     

Avian malaria is associated with increased reproductive investment in the blue tit

Haemosporidians causing avian malaria are very common parasites among bird species. Their negative effects have been repeatedly reported in terms of deterioration in survival prospects or reproductive success. However, a positive association between blood parasites and avian fitness has also been reported. Here, we studied a relationship between presence of malaria parasites and reproductive performance of the host, a hole‐breeding passerine – the blue tit Cyanistes caeruleus. Since the malaria parasites might affect their hosts differently depending on environmental conditions, we performed brood size manipulation experiment to differentiate parental reproductive effort and study the potential interaction between infection status and brood rearing conditions on reproductive performance. We found individuals infected with malaria parasites to breed later in the season in comparison with uninfected birds, but no differences were detected in clutch size. Interestingly, infected parents produced heavier and larger offspring with stronger reaction to phytohemagglutinin. More importantly, we found a significant interaction between infection status and brood size manipulation in offspring tarsus length and reaction to phytohemagglutinin: presence of parasites had stronger positive effect among birds caring for experimentally enlarged broods. Our results might be interpreted either in the light of the parasite‐mediated selection or terminal investment hypothesis.     

Enantiospecific Effects of Ketoconazole on Aryl Hydrocarbon Receptor

Azole antifungal ketoconazole (KET) was demonstrated to activate aryl hydrocarbon receptor (AhR). Since clinically used KET is a racemic mixture of two cis-enantiomers (2R,4S)-(+)-KET and (2S,4R)-(−)-KET, we examined the effects of KET enantiomers on AhR signaling pathway. (+)-KET dose-dependently activated AhR in human gene reporter cell line AZ-AHR, and displayed 5–20× higher agonist activity (efficacy), as compared to (−)-KET; both enantiomers were AhR antagonists with equal potency (IC₅₀). Consistently, (+)-KET strongly induced CYP1A1 mRNA and protein in human HepG2 cells, while (−)-KET exerted less than 10% of (+)-KET activity. In primary human hepatocytes, both enantiomers preferentially induced CYP1A2 over CYP1A1 mRNA and protein, and the potency of (+)-KET was slightly higher as compared to (−)-KET. Ligand binding assay with guinea pig liver cytosols revealed that both (+)-KET and (−)-KET are weak ligands of AhR that displaced [³H]-TCDD with comparable potency. Similarly, both enantiomers weakly transformed AhR to DNA-binding form with similar potency, as showed by EMSA, in guinea pig liver cytosolic extracts and nuclear extracts from mouse Hepa-1 cells. We also examined effects of KET on glucocorticoid receptor (GR), a regulator of AhR activity. Both KET enantiomers antagonized GR with similar potency, as revealed by gene reporter assay in AZ-GR cell line and down-regulation of tyrosine aminotransferase mRNA in human hepatocytes. Finally, we demonstrate enantiospecific antifungal activities of KET enantiomers in six Candida spp. strains. In conclusion, the significance of current study is providing the first evidence of enatiospecific effects of cis-enantiomers of ketoconazole on AhR-CYP1A pathway.