Orienting reflex: "targeting reaction" and "searchlight of attention"

The concept of orienting reflex based on the principle of vector coding of cognitive and executive processes is proposed. The orienting reflex to non-signal and signal stimuli is a set of orienting reactions: motor, autonomic, neuronal, and subjective emphasizing new and significant stimuli. Two basic mechanisms can be identified within the orienting reflex: a "targeting reaction" and a "searchlight of attention". In the visual system the first one consists in a foveation of a target stimulus. The foveation is performed with participation of premotor neurons excited by saccadic command neurons of the superior colliculi. The "searchlight of attention" is based on the resonance of gamma-oscillations in the reticular thalamus selectively enhancing responses of cortical neurons (involuntary attention). The novelty signal is generated in novelty neurons of the hippocampus, which are selectively tuned to a repeatedly presented standard stimulus. The selective tuning is caused by the depression of plastic synapses representing a "neuronal model" of the standard stimulus. A mismatch of the novel stimulus with the established neuronal model gives rise to a "novelty signal" enhancing the novel input. The novelty signal inhibits current conditioned reflexes (external inhibition) contributing to redirecting the behavior. By triggering the expression of early genes the novelty signal initiates the formation of the long-term memory connected with neoneurogenesis.     

Slow Relaxation Process in DNA

A dynamic transition at temperatures 200–230K is observed in manyhydrated bio-polymers. It shows up as a sharp increase of the mean-squaredatomic displacements above this temperature range. We present neutronscattering data of DNA at different levels of hydration. The analysis showsthat the dynamic transition in DNA is related to a slow relaxation processin the MHz-GHz frequency range. This slow relaxation process iscompletely suppressed in the dry DNA sample where no dynamic transitionwas observed. The nature of the slow process is discussed. We ascribe it toa global relaxation of DNA molecule that involves cooperative motion ofmany base-pairs and backbone.     

alpha(1C) (Ca(V)1.2) L-type calcium channel mediates mechanosensitive calcium regulation

Smooth muscle exhibitsmechanosensitivity independent of neural input, suggesting thatmechanosensitive pathways reside within smooth muscle cells. The nativeL-type calcium current recorded from human intestinal smooth muscle ismodulated by stretch. To define mechanosensitive mechanisms involved inthe regulation of smooth muscle calcium entry, we cloned the_1C L-type calcium channel subunit (Ca_V1.2)from human intestinal smooth muscle and expressed the channel in aheterologous system. This channel subunit retained mechanosensitivitywhen expressed alone or coexpressed with a ₂ calciumchannel subunit in HEK-293 or Chinese hamster ovary cells. Theheterologously expressed human cardiac _1C splice formalso demonstrated mechanosensitivity. Inhibition of kinase signalingdid not affect mechanosensitivity of the native channel. Truncation of the _1C COOH terminus, which containsan inhibitory domain and a proline-rich domain thought to mediatemechanosensitive signaling from integrins, did not disruptmechanosensitivity of the expressed channel. These data demonstratemechanical regulation of calcium entry through molecularly identifiedL-type calcium channels in mammalian cells and suggest that themechanosensitivity resides within the pore forming_1C-subunit.

     

Stability of microbial association in the process of industrial biofiltration cleaning of gaseous discharges

Results of industrial exploitation of a biofiltration plant tailored for purifying gaseous discharges of hazardous organic components such as toluene, cyclohexane, and xylene, are examined. Both numerical and compositional variations were monitored for a long-term (more than 1.5 years) utilization process in an association of microorganisms decomposing organic pollutants. A population of microbial association composed by one yeast and two bacterial strains in the biofilm on the surface of filtering sheets was abundant (10(8)-10(9) yeast cells/cm2 and 10(10)-10(11) bacterial cells/cm2) and stable during the whole period of monitoring. A microbial association in the culture medium averaging 10(6) yeast cells/l and 10(8) bacterial cells/l is more susceptible to technogenic impacts and seasonal fluctuations. Overall, the biofilter as an open and autonomic system maintained its microbial association, thereby providing a high-degree (93-98%) purification of industrial gaseous discharges from organic pollutants.     

Proton transfers in the photochemical reaction cycle of proteorhodopsin

The spectral and photochemical properties of proteorhodopsin (PR) were determined to compare its proton transport steps to those of bacteriorhodopsin (BR). Static and time-resolved measurements on wild-type PR and several mutants were done in the visible and infrared (FTIR and FT-Raman). Assignment of the observed C=O stretch bands indicated that Asp-97 and Glu-108 serve as the proton acceptor and donor, respectively, to the retinal Schiff base, as do the residues at corresponding positions in BR, but there are numerous spectral and kinetic differences between the two proteins. There is no detectable dark-adaptation in PR, and the chromophore contains nearly entirely all-trans retinal. Because the pK(a) of Asp-97 is relatively high (7.1), the proton-transporting photocycle is produced only at alkaline pH. It contains at least seven transient states with decay times in the range from 10 micros to 200 ms, but the analysis reveals only three distinct spectral forms. The first is a red-shifted K-like state. Proton release does not occur during the very slow (several milliseconds) rise of the second, M-like, intermediate, consistent with lack of the residues facilitating extracellular proton release in BR. Proton uptake from the bulk, presumably on the cytoplasmic side, takes place prior to release (tau approximately 2 ms), and coincident with reprotonation of the retinal Schiff base. The intermediate produced by this process contains 13-cis retinal as does the N state of BR, but its absorption maximum is red-shifted relative to PR (like the O state of BR). The decay of this N-like state is coupled to reisomerization of the retinal to all-trans, and produces a state that is O-like in its C-C stretch bands, but has an absorption maximum apparently close to that of unphotolyzed PR.     

Direct interaction of dermaseptin S4 aminoheptanoyl derivative with intraerythrocytic malaria parasite leading to increased specific antiparasitic activity in culture

Antiplasmodial activity of the dermaseptin S4 derivative K(4)S4(1-13) (P) was shown to be mediated by lysis of the host cells. To identify antiplasmodial peptides with enhanced selectivity, we produced and screened new derivatives based on P and singled out the aminoheptanoylated peptide (NC7-P) for its improved antiplasmodial properties. Compared with P, NC7-P displayed both increased antiparasitic efficiency and reduced hemolysis, including against infected cells. Antiplasmodial activity of P and its derivative was time-dependent and irreversible, implying a cytotoxic effect. But, whereas the dose dependence of growth inhibition and hemolysis of infected cells overlapped when treated with P, NC7-P exerted more than 50% growth inhibition at peptide concentrations that did not cause hemolysis. Noticeably, NC7-P but not P, dissipated the parasite plasma membrane potential and caused depletion of intraparasite potassium at nonhemolytic conditions. Confocal microscopy analysis of infected cells localized the rhodaminated derivative in association with parasite membranes and intraerythrocytic tubulovesicular structures, whereas in normal cells, the peptide localized exclusively at the plasma membrane. Overall, the data demonstrate that antimicrobial peptides can be engineered to act specifically on the membrane of intracellular parasites and support a mechanism whereby NC7-P crosses the host cell plasma membrane and disrupts the parasite membrane(s).     

Massive light-driven translocation of transducin between the two major compartments of rod cells: a novel mechanism of light adaptation

We report a new cellular mechanism of rod photoreceptor adaptation in vivo, which is triggered by daylight levels of illumination. The mechanism involves a massive light-dependent translocation of the photoreceptor-specific G protein, transducin, between the functional compartments of rods. To characterize the mechanism, we developed a novel technique that combines serial tangential cryodissection of the rat retina with Western blot analysis of protein distribution in the sections. Up to 90% of transducin translocates from rod outer segments to other cellular compartments on the time scale of tens of minutes. The reduction in the transducin content of the rod outer segments is accompanied by a corresponding reduction in the amplification of the rod photoresponse, allowing rods to operate in illumination up to 10-fold higher than would otherwise be possible.     

Overexpression of inhA,but not kasA,confers resistance to isoniazid and ethionamide in Mycobacterium smegmatis,M. bovis BCG and M. tuberculosis

The inhA and kasA genes of Mycobacterium tuberculosis have each been proposed to encode the primary target of the antibiotic isoniazid (INH). Previous studies investigating whether overexpressed inhA or kasA could confer resistance to INH yielded disparate results. In this work, multicopy plasmids expressing either inhA or kasA genes were transformed into M. smegmatis, M. bovis BCG and three different M. tuberculosis strains. The resulting transformants, as well as previously published M. tuberculosis strains with multicopy inhA or kasAB plasmids, were tested for their resistance to INH, ethionamide (ETH) or thiolactomycin (TLM). Mycobacteria containing inhA plasmids uniformly exhibited 20-fold or greater increased resistance to INH and 10-fold or greater increased resistance to ETH. In contrast, the kasA plasmid conferred no increased resistance to INH or ETH in any of the five strains, but it did confer resistance to thiolactomycin, a known KasA inhibitor. INH is known to increase the expression of kasA in INH-susceptible M. tuberculosis strains. Using molecular beacons, quantified inhA and kasA mRNA levels showed that increased inhA mRNA levels corre--lated with INH resistance, whereas kasA mRNA levels did not. In summary, analysis of strains harbouring inhA or kasA plasmids yielded the same conclusion: overexpressed inhA, but not kasA, confers INH and ETH resistance to M. smegmatis, M. bovis BCG and M. tuberculosis. Therefore, InhA is the primary target of action of INH and ETH in all three species.     

Scaleable and efficient synthesis of 2'-deoxy-2'-N-phthaloyl nucleoside phosphoramidites for oligonucleotide synthesis

2'-Deoxy-2'-N-phthaloyl nucleosides were prepared from arabino nucleosides by triflate displacement with phthalimide in the presence of DBU. The corresponding phosphoramidites suitable for automated oligonucleotide synthesis were also synthesized. The scalability of described procedures was demonstrated on a 100-g scale preparation of 2'-deoxy-2'-amino-C phosphoramidite.     

Genes and environment in arthritis: can RA be prevented?

Understanding of how interactions between genes and environment contribute to the development of arthritis is a central issue in understanding the etiology of rheumatoid arthritis (RA), as well as for eventual subsequent efforts to prevent the disease. In this paper, we review current published data on genes and environment in RA as well as in certain induced animal models of disease, mainly those in which adjuvants only or adjuvants plus organ-specific autoantigens are used to induce arthritis. We refer to some new data on environmental and genetic factors of importance for RA generated from a large case-control study in Sweden (1200 patients, 1200 matched controls). We found an increased risk of seropositive but not of seronegative RA in smokers, and there are indications that this effect may be due to a gene-environment interaction involving MHC class II genes. We also found an increased risk of RA in individuals heavily exposed to mineral oils. This was of particular interest because mineral oils are strong inducers of arthritis in certain rodent strains and because polymorphisms in human genetic regions syntenic with genes predisposing for oil-induced arthritis in rats have now been shown to associate with RA in humans. Taken together, our data support the notion that concepts and data on gene-environment interactions in arthritis can now be taken from induced animal models of arthritis to generate new etiological hypotheses for RA.