The Imidazolium Ionic Liquids Toxicity is Due to Their Effect on the Plasma Membrane

Ionic liquids (ILs) are organic salts with a low melting point. This is due to the fact that their alkyl side chains, which are covalently connected to the ion, hinder the crystallization of ILs. The low melting point of ILs has led to their widespread use as relatively harmless solvents. However, ILs do have toxic properties, the mechanism of which is largely unknown, so identifying the cellular targets of ILs is of practical importance. In our work, we showed that imidazolium ILs are not able to penetrate model membranes without damaging them. We also found that inactivation of multidrug resistance (MDR) pumps in yeast cells does not increase their sensitivity to imidazolium ILs. The latter indicates that the target of toxicity of imidazolium ILs is not in the cytoplasm. Thus, it can be assumed that the disruption of the barrier properties of the plasma membrane is the main reason for the toxicity of low concentrations of imidazolium ILs. We also showed that supplementation with imidazolium ILs restores the growth of cells with kinetically blocked glycolysis. Apparently, a slight disruption of the plasma membrane caused by ILs can, in some cases, be beneficial for the cell.

Two Types of Survival Curves of Different Lines of Progeric Mice

For most of their lifespan, the probability of death for many animal species increases with age. Gompertz law states that this increase is exponential. In this work, we have compared previously published data on the survival kinetics of different lines of progeric mice. Visual analysis showed that in six lines of these rapidly aging mutants, the probability of death did not strictly depend on age. In contrast, ten lines of progeric mice have survival curves similar to those of the control animals, that is, in agreement with Gompertz law, similar to the shape of an exponential curve upside down. Interestingly, these ten mutations cause completely different cell malfunctions. We speculate that what these mutations have in common is a reduction in the lifespan of cells and/or an acceleration of the transition to the state of cell senescence. Thus, our analysis, similar to the conclusions of many previously published works, indicates that the aging of an organism is a consequence of the aging of individual cells.

Structural Role of Plasma Membrane Sterols in Osmotic Stress Tolerance of Yeast Saccharomyces cerevisiae

Yeast S. cerevisiae has been shown to suppress a sterol biosynthesis as a response to hyperosmotic stress. In the case of sodium stress, the failure to suppress biosynthesis leads to an increase in cytosolic sodium. The major yeast sterol, ergosterol, is known to regulate functioning of plasma membrane proteins. Therefore, it has been suggested that the suppression of its biosynthesis is needed to adjust the activity of the plasma membrane sodium pumps and channels. However, as the sterol concentration is in the range of thirty to forty percent of total plasma membrane lipids, it is believed that its primary biological role is not regulatory but structural. Here we studied how lowering the sterol content affects the response of a lipid bilayer to an osmotic stress. In accordance with previous observations, we found that a decrease of the sterol fraction increases a water permeability of the liposomal membranes. Yet, we also found that sterol-free giant unilamellar vesicles reduced their volume during transient application of the hyperosmotic stress to a greater extent than the sterol-rich ones. Furthermore, our data suggest that lowering the sterol content in yeast cells allows the shrinkage to prevent the osmotic pressure-induced plasma membrane rupture. We also found that mutant yeast cells with the elevated level of sterol accumulated propidium iodide when exposed to mild hyperosmotic conditions followed by hypoosmotic stress. It is likely that the decrease in a plasma membrane sterol content stimulates a drop in cell volume under hyperosmotic stress, which is beneficial in the case of a subsequent hypo-osmotic one.

Cytostatic effects of structurally different ginsenosides on yeast cells with altered sterol biosynthesis and transport

Triterpene glycosides are a diverse group of plant secondary metabolites, consisting of a sterol-like aglycon and one or several sugar groups. A number of triterpene glycosides show membranolytic activity, and, therefore, are considered to be promising antimicrobial drugs. However, the interrelation between their structure, biological activities, and target membrane lipid composition remains elusive. Here we studied the antifungal effects of four Panax triterpene glycosides (ginsenosides) with sugar moieties at the C-3 (ginsenosides Rg3, Rh2), C-20 (compound K), and both (ginsenoside F2) positions in Saccharomyces cerevisiae mutants with altered sterol plasma membrane composition. We observed reduced cytostatic activity of the Rg3 and compound K in the UPC2-1 strain with high membrane sterol content. Moreover, LAM gene deletion reduced yeast resistance to Rg3 and digitonin, another saponin with glycosylated aglycon in the C-3 position. LAM genes encode plasma membrane-anchored StARkin superfamily-member sterol transporters. We also showed that the deletion of the ERG6 gene that inhibits ergosterol biosynthesis at the stage of zymosterol increased the cytostatic effects of Rg3 and Rh2, but not the other two tested ginsenosides. At the same time, in silico simulation revealed that the substitution of ergosterol with zymosterol in the membrane changes the spatial orientation of Rg3 and Rh2 in the membranes. These results imply that the plasma membrane sterol composition defines its interaction with triterpene glycoside depending on their glycoside group position. Our results also suggest that the biological role of membrane-anchored StARkin family protein is to protect eukaryotic cells from triterpenes glycosylated at the C-3 position.

Manipulating Cellular Energetics to Slow Aging of Tissues and Organs

Up to now numerous studies in the field of gerontology have been published. Nevertheless, a well-known food restriction remains the most reliable and efficient way of lifespan extension. Physical activity is also a well-documented anti-aging intervention being especially efficient in slowing down the age-associated decline of skeletal muscle mass. In this review we focus on the molecular mechanisms of the effect of physical exercise on muscle tissues. We also discuss the possibilities of pharmacological extension of this effect to the rest of the tissues. During the exercise, the level of ATP decreases triggering activation of AMP-dependent protein kinase (AMPK). This kinase stimulates antioxidant potential of the cells and their mitochondrial respiratory capacity. The exercise also induces mild oxidative stress, which, in turn, mediates the stimulation via hormetic response. Furthermore, during the exercise cells generate activators of mammalian target of rapamycin (mTOR). The intracellular ATP level increases during the rest periods between exercises thus promoting mTOR activation. Therefore, regular exercise intermittently activates anti-oxidant defenses and mitochondrial biogenesis (via AMPK and the hormetic response) of the muscle tissue, as well as its proliferative potential (via mTOR), which, in turn, impedes the age-dependent muscle atrophy. Thus, the intermittent treatment with activators of (i) AMPK combined with the inducers of hormetic response and of (ii) mTOR might partly mimic the effects of physical exercise. Importantly, pharmacological activation of AMPK takes place in the absence of ATP level decrease. The use of uncouplers of respiration and oxidative phosphorylation at the phase of AMPK activation could also prevent negative consequences of the cellular hyper-energization. It is believed that the decline of both antioxidant and proliferative potentials of the cells causes the age-dependent decline of multiple tissues, rather than only the muscular one. We argue that the approach above is applicable for the majority of tissues in an organism.

The GAR domain integrates functions that are necessary for the proper localization of fibrillarin (FBL) inside eukaryotic cells

Fibrillarin (FBL) is an essential nucleolar protein that participates in pre-rRNA methylation and processing. The methyltransferase domain of FBL is an example of an extremely well-conserved protein domain in which the amino acid sequence was not substantially modified during the evolution from Archaea to Eukaryota. An additional N-terminal glycine–arginine-rich (GAR) domain is present in the FBL of eukaryotes. Here, we demonstrate that the GAR domain is involved in FBL functioning and integrates the functions of the nuclear localization signal and the nucleolar localization signal (NoLS). The methylation of the arginine residues in the GAR domain is necessary for nuclear import but decreases the efficiency of nucleolar retention via the NoLS. The presented data indicate that the GAR domain can be considered an evolutionary innovation that integrates several functional activities and thereby adapts FBL to the highly compartmentalized content of the eukaryotic cell.

The Role of LAM Genes in the Pheromone-Induced Cell Death of S. cerevisiae Yeast

Lam1-4 proteins perform non-vesicular transport of sterols from the plasma membrane to the endoplasmic reticulum. Disruption of their function leads to an increase in the content of sterols in the plasma membrane. In mammals, homologs of Lam proteins are responsible for the internalization of plasma cholesterol. The biological role of Lam proteins in yeast remains unclear, since the strains lacking individual LAM genes do not display any pronounced phenotype. Deletion of LAM1 (YSP1) gene inhibits the regulated death of Saccharomyces cerevisiae yeast cells induced by the mating pheromone. Here, we investigated whether LAM2 also plays a role in the cell death induced by the excess of mating pheromone and assessed genetic interactions between LAM2 and genes responsible for ergosterol biosynthesis. We have shown that LAM2 deletion partially prevents pheromone-induced death of yeast cells of the laboratory strain W303, while deletions of three other LAM genes - LAM1, LAM3, and LAM4 - does not provide any additional rescuing effect. The UPC2-1 mutation in the transcription factor UPC2 gene, which leads to the excessive accumulation of sterols in the cell, promotes cell survival in the presence of the pheromone and shows additivity with the LAM2 deletion. On the contrary, LAM2 deletion stimulates pheromone-induced cell death in the laboratory strain BY4741. We have found that the deletion of ergosterol biosynthesis genes ERG2 and ERG6 reduces the effect of LAM2 deletion. Deletion of LAM2 in the Δerg4 strain lacking the gene of the last step of ergosterol biosynthesis, significantly increased the proportion of dead cells and decreased the growth rate of the yeast suspension culture even in the absence of the pheromone. We suggest that the absence of the effect of LAM2 deletion in the Δerg6 and Δerg2 strains indicates the inability of Lam2p to transport some ergosterol biosynthesis intermediates, such as lanosterol. Taken together, our data suggest that the role of Lam proteins in the regulated death of yeast cells caused by the mating pheromone is due to their effect on the plasma membrane sterol composition.

Mitochondrial dynamics in yeast with repressed adenine nucleotide translocator AAC2

The mitochondrial network structure dynamically adapts to cellular metabolic challenges. Mitochondrial depolarisation, particularly, induces fragmentation of the network. This fragmentation may be a result of either a direct regulation of the mitochondrial fusion machinery by transmembrane potential or an indirect effect of metabolic remodelling. Activities of ATP synthase and adenine nucleotide translocator (ANT) link the mitochondrial transmembrane potential with the cytosolic NTP/NDP ratio. Given that mitochondrial fusion requires cytosolic GTP, a decrease in the NTP/NDP ratio might also account for protonophore-induced mitochondrial fragmentation. For evaluating the contributions of direct and indirect mechanisms to mitochondrial remodelling, we assessed the morphology of the mitochondrial network in yeast cells with inhibited ANT. We showed that the repression of AAC2 (PET9), a major ANT gene in yeast, increases mitochondrial transmembrane potential. However, the mitochondrial network in this strain was fragmented. Meanwhile, AAC2 repression did not prevent mitochondrial fusion in zygotes; nor did it inhibit mitochondrial hyperfusion induced by Dnm1p inhibitor mdivi-1. These results suggest that the inhibition of ANT, rather than preventing mitochondrial fusion, facilitates mitochondrial fission. The protonophores were not able to induce additional mitochondrial fragmentation in an AAC2-repressed strain and in yeast cells with inhibited ATP synthase. Importantly, treatment with the ATP synthase inhibitor oligomycin A also induced mitochondrial fragmentation and hyperpolarization. Taken together, our data suggest that ATP/ADP translocation plays a crucial role in shaping of the mitochondrial network and exemplify that an increase in mitochondrial membrane potential does not necessarily oppose mitochondrial fragmentation.

LAM Genes Contribute to Environmental Stress Tolerance but Sensibilize Yeast Cells to Azoles

Lam proteins transport sterols between the membranes of different cellular compartments. In Saccharomyces cerevisiae, the LAM gene family consists of three pairs of paralogs. Because the function of paralogous genes can be redundant, the phenotypes of only a small number of LAM gene deletions have been reported; thus, the role of these genes in yeast physiology is still unclear. Here, we surveyed the phenotypes of double and quadruple deletants of paralogous LAM2(YSP2)/LAM4 and LAM1(YSP1)/LAM3(SIP3) genes that encode proteins localized in the junctions of the plasma membrane and endoplasmic reticulum. The quadruple deletant showed increased sterol content and a strong decrease in ethanol, heat shock and high osmolarity resistance. Surprisingly, the quadruple deletant and LAM2/LAM4 double deletion strain showed increased tolerance to the azole antifungals clotrimazole and miconazole. This effect was not associated with an increased rate of ABC-transporter substrate efflux. Possibly, increased sterol pool in the LAM deletion strains postpones the effect of azoles on cell growth. Alternatively, LAM deletions might alleviate the toxic effect of sterols as Lam proteins can transport toxic sterol biosynthesis intermediates into membrane compartments that are sensitive to these compounds. Our findings reveal novel biological roles of LAM genes in stress tolerance and suggest that mutations in these genes may confer upregulation of a mechanism that provides resistance to azole antifungals in pathogenic fungi.

Triosephosphates as Intermediates of the Crabtree Effect

An increase in glucose concentration in the medium rapidly decreases respiration rate in many cell types, including tumor cells. The molecular mechanism of this phenomenon, the Crabtree effect, is still unclear. It was shown earlier that adding the intermediate product of glycolysis fructose-1,6-bisphosphate to isolated mitochondria suppresses their respiration. To study possible roles of glycolytic intermediates in the Crabtree effect, we used a model organism, the yeast Saccharomyces cerevisiae. To have the option to rapidly increase intracellular concentrations of certain glycolytic intermediates, we used mutant cells with glycolysis blocked at different stages. We studied fast effects of glucose addition on the respiration rate in such cells. We found that addition of glucose affected cells with deleted phosphoglycerate mutase (strain gpm1-delta) more strongly than ones with inactivated aldolase or phosphofructokinase. In the case of preincubation of gpm1-delta cells with 2-deoxyglucose, which blocks glycolysis at the stage of 2-deoxyglucosephosphate formation, the effect of glucose addition was absent. This suggests that triosephosphates are intermediates of the Crabtree effect. Apart from this, the incubation of gpm1-delta cells in galactose-containing medium appeared to cause a large increase in their size. It was previously shown that galactose addition did not have any short-term effect on respiration rate of gpm1-delta cells and, at the same time, strongly suppressed their growth rate. Apparently, the influence of increasing triosephosphate concentration on yeast physiology is not limited to the activation of the Crabtree effect.

Mitochondrial depolarization in yeast zygotes inhibits clonal expansion of selfish mtDNA

Non-identical copies of mitochondrial DNA (mtDNA) compete with each other within a cell and the ultimate variant of mtDNA present depends on their relative replication rates. Using yeast Saccharomyces cerevisiae cells as a model, we studied the effects of mitochondrial inhibitors on the competition between wild-type mtDNA and mutant selfish mtDNA in heteroplasmic zygotes. We found that decreasing mitochondrial transmembrane potential by adding uncouplers or valinomycin changes the competition outcomes in favor of the wild-type mtDNA. This effect was significantly lower in cells with disrupted mitochondria fission or repression of the autophagy-related genes ATG8, ATG32 or ATG33, implying that heteroplasmic zygotes activate mitochondrial degradation in response to the depolarization. Moreover, the rate of mitochondrially targeted GFP turnover was higher in zygotes treated with uncoupler than in haploid cells or untreated zygotes. Finally, we showed that vacuoles of zygotes with uncoupler-activated autophagy contained DNA. Taken together, our data demonstrate that mitochondrial depolarization inhibits clonal expansion of selfish mtDNA and this effect depends on mitochondrial fission and autophagy. These observations suggest an activation of mitochondria quality control mechanisms in heteroplasmic yeast zygotes.

How do yeast sense mitochondrial dysfunction?

Apart from energy transformation, mitochondria play important signaling roles. In yeast, mitochondrial signaling relies on several molecular cascades. However, it is not clear how a cell detects a particular mitochondrial malfunction. The problem is that there are many possible manifestations of mitochondrial dysfunction. For example, exposure to the specific antibiotics can either decrease (inhibitors of respiratory chain) or increase (inhibitors of ATP-synthase) mitochondrial transmembrane potential. Moreover, even in the absence of the dysfunctions, a cell needs feedback from mitochondria to coordinate mitochondrial biogenesis and/or removal by mitophagy during the division cycle. To cope with the complexity, only a limited set of compounds is monitored by yeast cells to estimate mitochondrial functionality. The known examples of such compounds are ATP, reactive oxygen species, intermediates of amino acids synthesis, short peptides, Fe-S clusters and heme, and also the precursor proteins which fail to be imported by mitochondria. On one hand, the levels of these molecules depend not only on mitochondria. On the other hand, these substances are recognized by the cytosolic sensors which transmit the signals to the nucleus leading to general, as opposed to mitochondria-specific, transcriptional response. Therefore, we argue that both ways of mitochondria-to-nucleus communication in yeast are mostly (if not completely) unspecific, are mediated by the cytosolic signaling machinery and strongly depend on cellular metabolic state.

Negative Feedback of Glycolysis and Oxidative Phosphorylation: Mechanisms of and Reasons for It

There are two main pathways of ATP biosynthesis: glycolysis and oxidative phosphorylation. As a rule, the two pathways are not fully active in a single cell. In this review, we discuss mechanisms of glycolytic inhibition of respiration (Warburg and Crabtree effects). What are the reasons for the existence of this negative feedback? It is known that maximal activation of both processes can cause generation of reactive oxygen species. Oxidative phosphorylation is more efficient from the energy point of view, while glycolysis is safer and favors biomass synthesis. This might be the reason why quiescent cells are mainly using oxidative phosphorylation, while the quickly proliferating ones - glycolysis.

[The clinical picture and specific microbiological features of acute otitis media]

The objective of the present work was to study the spectrum of bacterial pathogenic agents responsible for the development of acute otitis media under present conditions and to elucidate the relationship between the pathogen species and the clinical course of the inflammatory process in the middle ear. A total of 60 patients of either sex at the age varying from 18 to 64 patients were available for the examination. All of them complained of ear pain, purulent discharge from the ears, hearing impairment, and general weakness. The following methods were employed: the analysis of the patients' complaints and their medical histories, visualexamination of the ENT organs, tonal threshold audiometry, tympanometry, and the analysis of secretion from the tympanic cavity using the real-time PCR technique. The study has demonstrated some regular patterns of the clinical manifestations of the disease depending on its causative agent. Specifically, it turned out that acute otitis media associated with the infection by Streptоcoccus pneumoniae is characterized by the more reactive clinical symptoms and the greater amount of complications compared with acute otitis media caused by Haemophilus influenzae that is largely a subclinical pathology. However, the latter condition more frequently leads to chronization of the pathological process.

Dodecyltriphenylphosphonium inhibits multiple drug resistance in the yeast Saccharomyces cerevisiae

Multiple drug resistance pumps are potential drug targets. Here we asked whether the lipophilic cation dodecyltriphenylphosphonium (C12TPP) can interfere with their functioning. First, we found that suppression of ABC transporter gene PDR5 increases the toxicity of C12TPP in yeast. Second, C12TPP appeared to prevent the efflux of rhodamine 6G - a fluorescent substrate of Pdr5p. Moreover, C12TPP increased the cytostatic effects of some other known Pdr5p substrates. The chemical nature of C12TPP suggests that after Pdr5p-driven extrusion the molecules return to the plasma membrane and then into the cytosol, thus effectively competing with other substrates of the pump.

Mitochondrial signaling in Saccharomyces cerevisiae pseudohyphae formation induced by butanol

Yeasts growing limited for nitrogen source or treated with fusel alcohols form elongated cells--pseudohyphae. Absence of mitochondrial DNA or anaerobic conditions inhibits this process, but the precise role of mitochondria is not clear. We found that a significant percentage of pseudohyphal cells contained mitochondria with different levels of membrane potential within one cell. An uncoupler carbonyl cyanide p-(trifluoromethoxy) phenylhydrazone (FCCP), but not the ATP-synthase inhibitor oligomycin D, prevented pseudohyphal growth. Interestingly, repression of the MIH1 gene encoding phosphatase activator of the G2/M transition partially restores the ability of yeast to form pseudohyphal cells in the presence of FCCP or in the absence of mitochondrial DNA. At the same time, retrograde signaling (the one triggered by dysfunctional mitochondria) appeared to be a positive regulator of butanol-induced pseudohyphae formation: the deletion of any of the retrograde signaling genes (RTG1, RTG2, or RTG3) partially suppressed pseudohyphal growth. Together, our data suggest that two subpopulations of mitochondria are required for filamentous growth: one with high and another with low transmembrane potential. These mitochondria-activated signaling pathways appear to converge at Mih1p level.

Mitochondrially-encoded protein Var1 promotes loss of respiratory function in Saccharomyces cerevisiae under stressful conditions

Stressed Saccharomyces cerevisiae cells easily lose respiratory function due to deletions in mitochondrial DNA, and this increases their general stress resistance. Is the loss active? We found that erythromycin (an inhibitor of mitochondrial translation) prevents the loss in control cells but not in the ones expressing mitochondrially-encoded protein Var1 in the nucleus. Var1 is a component of mitochondrial ribosomes; it is hydrophilic, positively charged, and prone to aggregation. Addition of DNase altered Var1 content in a preparation of mitochondrial nucleoids. Our data indicate that Var1 physically interacts with mitochondrial DNA and under stress negatively regulates its maintenance.

Inactivation of Pmc1 vacuolar Ca(2+) ATPase causes G(2) cell cycle delay in Hansenula polymorpha

The vacuolar Ca(2+) ATPase Pmc1 is involved in maintenance of a low Ca(2+) concentration in cytosol in yeast cells. Here we observed that increase of Ca(2+) cytosolic concentration in yeast Hansenula polymorpha due to inactivation of Pmc1 resulted in sensitivity to sodium dodecyl sulfate (SDS). To elucidate the mechanisms of the observed effect, a screening for mutations suppressing SDS sensitivity of the H. polymorpha pmc1 mutant was performed. As a result, three genes were identified. Two of them, designated as their Saccharomyces cerevisiae orthologs CCH1 and HOG1 encoded the plasma membrane voltage-gated high-affinity calcium channel and the MAP kinase involved in osmoregulation, respectively. The third gene, designated as WEE1, coded for the ortholog of Wee1/Swe1 kinase involved in cell cycle regulation by inhibiting of the G(2)/M transition. Detailed analysis of this mutant demonstrated that suppression of pmc1 SDS sensitivity by the wee1 mutation depended on an accompanying chromosomal rearrangement, whereas inactivation of WEE1 in the absence of this rearrangement caused SDS sensitivity. Expression of a chimeric protein containing an N-terminal portion of Wee1 in the pmc1 mutant led to abnormal morphology characteristic of G(2) delay. Our data indicate that cytosolic Ca(2+) rise causes SDS sensitivity in H. polymorpha through the activation of the Wee1 kinase, which is mediated by the Hog1 kinase. Wee1 has a dual role in the manifestation of SDS sensitivity in the H. polymorpha pmc1 mutant. Mechanisms of influence of the obtained mutations on the G(2)/M transition are discussed.

Mitochondrial matrix fragmentation as a protection mechanism of yeast Saccharomyces cerevisiae

It was shown that separate fragments of the inner mitochondrial compartment (mitoplasts) can exist under a single non-fragmented outer membrane. Here we asked whether fragmentation of the inner mitochondria could prevent rupturing of the outer membrane and release of pro-apoptotic molecules from the mitochondrial intermembrane space into the cytoplasm during mitochondrial swelling. First, we showed that in Saccharomyces cerevisiae yeast addition of amiodarone causes formation of electrically separate compartments within mitochondrial filaments. Moreover, amiodarone treatment of Deltaysp2 mutant produced a higher proportion of cells with electrically discontinuous mitochondria than in the wild type, which correlated with the survival of cells. We confirmed the existence of separated mitoplasts under a single outer membrane using electron microscopy. Mitochondria with fragmented matrixes were also detected in cells of the stationary phase. Our data suggest that such fragmentation acts as a cellular protective mechanism against stress.

Unexpected link between anaphase promoting complex and the toxicity of expanded polyglutamines expressed in yeast

Protein aggregation is intimately linked to a number of neurodegenerative diseases. Expansion of the huntingtin polyglutamine-rich domain causes protein aggregation and neuronal degeneration. Recently we found that, similar to neurons, yeast expressing the expanded domain show markers of programmed cell death. Here we showed that deletion of yeast metacaspase gene YCA1 partly rescues the toxic effect of the domain overexpression. We also performed genetic screen for other genes deletions alleviating the toxic effect and found ASE1. Ase1 is a substrate of the Cdh1 form of anaphase promoting complex, APC/Cdh1. We tested Cdh1 overexpression and the deletion of CLB2 (mitotic cyclin, substrate of APC/Cdh1) and found that both mutations had a rescuing effect on the expanded polyglutamine toxicity. Our data suggest that the toxic effect of aggregated proteins is partly indirect. We speculate that cellular attempt to degrade the aggregates overloads the proteasome, and this leads to pathological accumulation of APC substrates.

Spectroradiometer with wedge interference filters (SWIF): measurements of the spectral optical depths at Mauna Loa Observatory

A spectroradiometer with wedge interference filters (SWIF) (the filters were produced by Carl Zeiss, Jena, Germany) and a CCD matrix (which was of Russian production) that functions as the sensor has been designed and built for use in ground-based optical sensing of the atmosphere and the Earth's surface in the spectral range of 0.35-1.15 µm. Absolute calibration of this instrument was performed through a series of observations of direct solar radiation at Mauna Loa Observatory (MLO) in Hawaii in May and June 1993. Spectral optical depth (SOD) measurements that were made during these field experiments provided detailed spectral information about both aerosol extinction (scattering plus absorption) and molecular absorption in the atmosphere above the site at MLO. The aerosol-SOD measurements were compared with narrow-band radiometer measurements at wavelengths of 380, 500, and 778 nm The SWIF and narrow-band radiometer measurements are in agreement to within the experimental error. At a wavelength of 500 nm, the aerosol SOD was found to be approximately 0.045. Adescription of the SWIF instrument, its absolute calibration, and the determination of atmospheric SOD's at MLO are presented.

[The effect of moderate doses of ethanol on the evoked neuronal activity of the sensorimotor cortex]

Influence of acute administration of ethanol in moderate doses (170-1200 mg/kg, intraperitoneally) on the evoked activity of sensorimotor cortical neurons in response to electrical stimulation of the contralateral forelimb was studied in outbred rats never earlier exposed to ethanol action. During the first 20-25 min of ethanol action whether augmentation or attenuation in the level of neuronal reactivity could occur as well which in both cases could be accompanied by significant variability of latencies in poststimulus discharges and destabilization of their patterns. Expressed modifications in neuronal patterns at the first stage of ethanol action suggest that ethanol destabilizes evoked reactions of sensorimotor cortical neurons to afferent stimulation. This underlines the need for more complete approach to investigation of primary CNS reactions to ethanol paying more attention to temporal succession of origin and flow of these effects. Possible relations between oppositely directed primary reactions of single cortical neurons and individual characteristics of perception of different animals are discussed.

[The effect of moderate doses of ethanol on the nature of the background neuronal impulse activity of the sensorimotor cortex in rats]

The influence of acute administration of moderate doses of ethanol (170-1200 mcg/kg, intraperitoneally) on the spontaneous impulse activity of motor cortex neurons was studied in outbred rats never earlier exposed to alcohol. Initial reactions of the cortical neurons were shown to be characterized by the changes in the frequency of spontaneous activity which could be increased or decreased during the first 20-25 min after the injection. The changes in the mean frequency of spontaneous discharges were accompanied by the changes in their patterns. Both increase and decrease of the mean frequency at the initial stage of ethanol action was accompanied by significant variability of interspike intervals. It is emphasized that examination of the initial reactions of the cortical neurons to ethanol administration demands studying their temporal duration.

[The single administration of ethanol and the amplitude of the action potentials of the neocortical neurons in rats: extracellular studies]

On outbred rats the influence was studied of acute administration of moderate dozes of ethanol (150 mg--1.2 g/kg, intraperitoneally) on the motor cortex neurones. It was shown that ethanol in the range of these dozes led to a change of the amplitude of extracellularly recorded action potentials, which could be directed to an increase or decrease. In the used range minimum as well as maximum dozes in various animals might elicit contrary effects, i.e. no dependence was observed of the direction of reaction of the studied neurones on the administrated doze. Possible mechanisms are discussed which may be the basis of the change of the amplitude of extracellular action potentials. Conclusion is made that use of moderate dozes of ethanol is a useful condition for studies directed to a search of mechanisms of initial reaction to alcohol action.

[Plasmapheresis in the treatment of critical stages of ischemia in diabetic angiopathy of the lower extremities]

The authors have used gravitation plasmapheresis in the treatment of 26 patients with diabetic angiopathies of lower extremities. It was established that continuous gravitation plasmapheresis facilitated the immediate correction of most of the altered biochemical and coagulation parameters of blood, in patients with diabetes mellitus. The use of rheopolyglucinum is followed by stable central hemodynamics and stabilization of the general state of the patients during continuous plasmapheresis which allows to recommend rheopolyglucinum as the main plasma-substituting solution for fractionation of blood in patients with diabetic angiopathies. The gravitation plasmapheresis used in the treatment of critical degrees of ischemia in patients with diabetic angiopathies of lower extremities is thought by the authors to allow to preserve the extremity or to make the level of its amputation lower in most patients.

[Electrical activity of the brain during behavior directed at elimination of a dominant]

The stage of dominant discontinuation (ending) was studied on the model of "polarization dominant". The dominant focus was created in rabbits at the site of forepaw projection in the cortex. On reaching the dominant optimum it was disrupted (DC was switched off) after summation (forepaw movement) in response to eye stimulation by an air puff. In the next tests the rabbit voluntarily disrupted the dominant by blinking of the corresponding eye after DC was switched on. The analysis of electrical brain activity by computer showed, that goal-directed blinking is preceded by the rise in the estimation of power spectra in the range of delta-frequencies of potentials in the neocortical frontal zones and in subcortical structures connected with blinking function. In the latter the potentials change earlier than in the cortex. Goal-directed blinking is preceded by the appearance of hemispheric asymmetry and of readiness potentials in the electrical activity of the neocortical frontal zones.

[Spectral-correlation analysis of high-frequency EEG components of the rabbit cerebral cortex during orienting and defensive responses]

A change was shown in the EEG power spectra of the sensorimotor, visual and auditory neocortical areas and the dorsal hippocampus, and corresponding coherence functions in the range of 14.6-110 c/s during an orienting reaction and the formation of a defensive conditioned reflex in rabbits. It was suggested that the rhythm of about 5 c/s appearing during formation of the conditioned reflex, serves for the functional integration of the brain structures which is specific for a certain functional state.