Effect of lipid alkyl chain perturbations on the assembly of bacteriophage PM2

Antiphage activity of natural and synthetic substances: a new age for antivirals?

Viruses are considered biological entities that possess a genome and can adapt to the environment of living organisms. Since they are obligate intracellular parasites, their cycle of replication can result in cell death, and consequently, some viruses are harmful to mammalian cells and can cause disease in humans. Therefore, the search for substances for the treatment of viral diseases can be accomplished through the use of bacteriophages as models for eukaryotic cell viruses. Thus, this review highlights the main studies identifying substances with antiphage activity in comparison assays involving phages and eukaryotic viruses, in order to explore the potential of these substances as antivirals. As a future perspective, this approach may help at the beginning of an Antiviral Age.

Short-term storage sperm of coho salmon (Oncorhynchus kisutch) at 4 °C: Effect of sperm: Extender dilution ratios and antioxidant butyl-hydroxytoluene (BHT) on sperm function

Short-term storage of semen is a necessary key procedure in fish; it allows maximizing the use of gametes. Nevertheless, sperm quality decreases during storage has been associated with oxidative stress damage due to an increase in reactive oxygen species (ROS) during storage. This study was designed to optimize a short-term storage protocol for Coho salmon (Oncorhynchus kisutch) spermatozoa, evaluating the effect of extender dilution and the addition of butyl-hydroxytoluene (BHT) antioxidant on sperm function parameters. In the first experiment, fresh semen was diluted in Storfish®: extender dilution (1:2 and 1:3) and a control sample undiluted and stored at 4 °C for 7-days. In both experiments motility (MO), viability and integrity of plasma membrane, mitochondrial membrane potential (MMP) and superoxide anion level (O₂^-) were evaluated at 0, 3 and 7 days. Result shows that, 1:3 dilution maintained a higher sperm function for a longer period time. In the second experiment, spermatozoa were suspended in Storfish® (1:3) supplemented with two different concentrations of BHT (1.0 mM and 2.0 mM) and a control sample without antioxidant and stored at 4 °C for 7 days. The results demonstrated that, antioxidant-supplemented samples greater MO than control samples (P < 0.05). The viability remained >75% during storage in all groups. MMP was higher in 2.0 mM BHT compared to 1.0 mM and control (P < 0.05), in addition, this concentration reduced O₂^- level (P < 0.05). In conclusion, sperm: extender dilution 1:3 and adding of 2.0 mM BHT in sperm storage extender may enhance protection sperm function in Oncorhynchus kisutch against effects harmful of the oxidative stress during the in vitro storage.

Partitioning and localization of spin-labeled amantadine in lipid bilayers: an EPR study

EPR was used to study the distribution of the spin-labeled amantadine (AA-SL) between the bulk hydrophobic-hydrocarbon solvent, light paraffin oil, and water and between hydrophobic-hydrocarbon chain region of lipid membranes and water. The AA-SL molecules were soluble in both hydrophobic and polar regions of investigated systems. It was shown that the partition coefficient of AA-SL between the hydrocarbon region of the L-alpha-dimyristoylphosphatidylcholine fluid-phase membrane and water is much higher than between bulk hydrocarbon solvent and water. Furthermore, the partitioning of AA-SL into membranes of multilamellar liposomes made of L-alpha-dimyristoylphosphatidylcholine, L-alpha-dipalmitoylphosphatidylcholine, and L-alpha-distearoylphosphatidylcholine was studied as a function of temperature, indicating no abrupt change at the main phase transition of these membranes. It is also clear from our data that AA-SL can penetrate into the gel-phase membrane practically with the same partitioning as into the fluid-phase membrane. Furthermore, it was shown that at least part of the AA-SL molecule is deeply buried in the hydrocarbon chain region of the membrane.

An approach to AIDS therapy using hyperthermia and membrane modification

Altering the biophysical characteristics of cell membranes by diet and membrane perturbing agents markedly influences thermosensitivity of cells. Likewise, manipulation of viral envelopes either by altering their lipid composition by diet or by the use of agents that perturb the lipid envelope influence infectivity of enveloped viruses and the progression of viral disease. The use of hyperthermia and envelope modification as a combined approach to treat AIDS has until now neither been suggested nor attempted. On the basis of my previous work and a review of the literature, I theorize that the combination of hyperthermia with procedures designed to alter the viral envelope will likely result in an increased viral sensitivity and be useful clinically for treatment of patients with enveloped viral diseases such as AIDS.

The influence of the antiviral drugs amantadine and rimantadine on erythrocyte and platelet membranes and its comparison with that of tetracaine

The influence of the antivirus drugs amantadine and rimantadine and of the anionic analogue 1-adamantane-carboxylic acid on a range of properties of human erythrocyte membrane and of thrombocytes has been compared with the effect of the local anaesthetic tetracaine. At low antiviral drug concentrations the abilities of the drugs to induce erythrocyte shape change and suppress osmotic haemolysis were quantitatively proportional to their clinical potency (rimantadine more effective than amantadine at the same concentration). Rimantadine was also more effective than amantadine in suppressing influenza virus-erythrocyte fusion and viral induced haemolysis. The antiviral drug effects were qualitatively similar to those induced by tetracaine. At the quantitative level, tetracaine was more efficient than the antiviral drugs in inhibiting osmotic haemolysis, virus membrane fusion and platelet aggregation. In the absence of any specificity of the antiviral drug effects we argue for a lysosomotropic mode of drug action, i.e. that the drugs modify virus-membrane interactions by changing the endosomal or lysosomal pH.

Spectroscopic characterization of vesicle formation on heated human erythrocytes and the influence of the antiviral agent amantadine

EPR investigations on the vesiculation process of heated human erythrocytes were performed, using different fatty acid spin labels. Spectrin denaturation and vesiculation do not influence the fluidity of the lipid phase of the remaining membrane of human erythrocytes: Vesicles released differ in chemical composition as well as in the lipid fluidity of their membrane from the intact human erythrocyte membrane. A reduced cholesterol-to-phospholipid ratio and a depletion of spectrin was found. By changing the ionic concentration of the suspension medium an effect on membrane spectra and on vesicle release was established. The adamantane derivative amantadine causes fluidization of the human erythrocyte membrane and inhibits vesicle release. Based on these results, a model for the mechanism by which adamantane-like molecules could interact with membranes is proposed.

Effect of butanol on lipid composition and fluidity of Clostridium acetobutylicum ATCC 824

Butanol, at sub-growth-inhibitory levels, caused a ca. 20 to 30% increase in fluidity of lipid dispersions from Clostridium acetobutylicum. When grown in the presence of butanol or into stationary phase, C. acetobutylicum synthesized increased levels of saturated acyl chains at the expense of unsaturated chains.

Adamantyl nitroxide: a spin label for probing membrane surfaces

In an effort to understand more about the perturbing properties of adamantane-like molecules on biological membranes, the spin probe adamantyl nitroxide (2,2'-dimethyl-5-adamantyl oxazolidine-N-oxyl) was synthesized, purified and characterized. Electron paramagnetic resonance (EPR) spectra were then obtained from 1:50 and 1:200 mixtures of adamantyl nitroxide with dipalmitoyl and dipalmityl phosphatidylcholine multibilayers. Above the phase transition temperature of these lipids (41 degrees C for dipalmitoyl phosphatidylcholine and 43 degrees C for dipalmityl phosphatidylcholine) the spectra of adamantyl nitroxide are similar to control spectra obtained in liquid oleic acid. Below the phase transition temperatures, however, spectral differences were observed depending on: (1) the concentration of the spin probe in the lipid; (2) the linkage between the polar head group and the hydrocarbon tails of the phospholipid; (3) the temperature of the sample. Partitioning of adamantyl nitroxide between the aqueous and hydrocarbon phases of the sample is most prominent at probe-to-lipid ratios of 1:200 and at temperatures below the pre-transition temperature of the lipid (around 33 degrees C). Computer simulations of the above results, as well as additional experiments performed at 35 GHz, show that the results arise from true partitioning and not from asymmetric probe motion. Two conclusive results of these experiments are that spectra of adamantyl nitroxide in phospholipid multibilayers are sensitive to probe concentration and to the physical characteristics of the phospholipid which they probe. The spectral differences which arise when adamantyl nitroxide is used with ether- and ester-linked phospholipids indicate that it is a sensitive probe of membrane surfaces. Employment of this molecule in membrane research should prove to be useful in obtaining additional information about membrane surface events.

Distribution of metabolism of the potential anti-parkinson drug memantine in the human

GC-MS of tissue extracts obtained from a parkinsonian patient who died from secondary causes during memantine (1-amino-3.5-dimethyladamantane) treatment showed the drug to be largely unmetabolized. In the kidney and liver a second peak corresponded to less than 1% of the main temporal lobe, hypothalamus and pons. Thus treatment with 2 X 10 mg memantine/day reveals an accumulation of the drug in microM concentrations in the brain. This is probably high enough to explain the ameliorating effect of memantine treatment in patients suffering from Parkinson's disease.

In vitro studies on the possible effects of 1-aminoadamantanes on the serotonergic system in M. Parkinson

Synaptosomes, synaptic vesicles, and membranes were isolated from rat brain homogenates by differential and density gradient centrifugation in sucrose. Synaptosomes incorporated serotonin (5-HT) with two different uptake mechanisms, high affinity: Kt1 = 47 nM and low affinity: Kt2 = 660 nM. Both uptake mechanisms are non-competitively inhibited by the potential antiparkinson drugs 1-aminoadamantane (amantadine, D 1: Ki1 = 57 microM, Ki2 = 96 microM) and 1-amino-3,5-dimethyladamantane (memantine, D 145: Ki1 = 97 microM, Ki2 = 150 microM). The incorporated 5-HT is released from synaptosomes on incubation with high concentrations (0.5--5 mM) of the drugs or on electrical stimulation with rectangular pulses of alternating polarity. Subthreshold concentrations of these drugs (5--50 microM) which are too low to liberate 5-HT increase the electrically stimulated release of 5-HT.--The effect of D 1, D 145, and electrical stimulation on DA release parallels the results observed with 5-HT. The uptake of 5-HT into isolated synaptic vesicles and the binding to isolated nerve ending membranes is non-competitively inhibited by 1-aminoadamantanes. D 145 inhibits the binding of 5-HT to membranes more effectively (Ki = 0.95 mM) than its uptake into vesicles (Ki = 1.2 mM) contrasting with D 1 which is a weaker inhibitor affecting vesicular uptake (Ki = 2.5 mM) slightly more than membrane binding (Ki = 3.1 mM). The results obtained suggest that, in addition to other mechanisms like receptor stimulation, 1-aminoadamantanes may act in parkinsonian patients by enriching the transmitter content in the synaptic cleft.

Localization of the membrane perturber adamantylsulfate in sarcoplasmic reticular vesicles

The properties of a new membrane perturbing agent, adamantyl sulfate (A-1-S) are described. Lobster sarcoplasmic reticular vesicles (SRV) were used as a test membrane system and the activity of the Ca2+--Mg2+-dependent ATPase in conjunction with spin label data was used to determine the location of A-1-S in the membrane. The results suggest that A-1-S perturbs only the polar region of the SRV and that this causes loss of ATPase function. Thus, ATPase activity requires integrity of the membrane polar region.

Effect of double-bonds on bimolecular films in membrane models

The effect of unsaturation (especially by cis-bonds) is studied on bimolecular films of saturated and unsaturated alkylammonium ions and alkanols between silicate surfaces as model systems for lipid layers in membranes. Three types of structures are observed: all-trans-blocks, kink-blocks and gauche-blocks. The knowledge of the sequence of these phases and their thermal transitions provides detailed deductions about the role of double-bonds. cis-Unsaturated chains are taken up in bimolecular films as isomers with cis-trans-gauche conformation. This conformation makes the shape of the chain similar to that of kinked chains (chains with gauche-trans-gauche (--) conformation) and enables the incorporation into the film without greater sterical hindrance. The experimental results are in good agreement with X-ray measurements on biological membranes by Engelman (Engelman, D.M., J. Mol. Biol. 47, 115--117 (1970) and 58, 153--165 (1971)). Increasing the concentration of cis-chains decreases the transition temperature of the kink-blocks into gauche-blocks. The variation of the transition temperature with concentration of cis-unsaturated chains in the model system is similar to that observed for Escherichia coli membranes. It is suggested that phase changes in biomembranes are of the same nature: transition of kink-block analogues as ordered phases into gauche-block assemblies as less ordered phases.

Inactivation and inhibition of replication of the enveloped bacteriophage phi6 by fatty acids

The enveloped bacteriophage phi6 has been shown to be an interesting model system for the study of chemical agents that might have specific antiviral effects against lipid-containing mammalian viruses. In this report, we describe two types of antiviral activity exhibited by several fatty acids against bacteriophage phi6. Oleic acid (18:1) and palmitoleic acid (16:1) were potent inactivators of the virus. Treatment with either fatty acid at 50 mug/ml at 25 or 0 degrees C for 30 min reduced the virus titer to about 0.1% of the initial titer. Oleic acid at a concentration as low as 3 mug/ml ( approximately 10(-2) mM) reduced the virus titer to <1% of the initial titer within 30 min. Ultracentrifugation analyses of (14)C-amino acid- and (32)P-labeled virus treated with oleic acid indicated that the virion is largely disassembled by the treatment. Myristic acid (14:0) and palmitic acid (16:0) did not inactivate phi6 at 50 mug/ml, but nevertheless did prevent phi6 plaque production. Single-step virus growth experiments in which fatty acid was added at various times before or after infection indicated that it was an early stage of the phi6 replication cycle that was inhibited by the presence of myristic acid and that the inhibition occurred only if the myristic acid concentration in the extracellular growth medium was greater, similar10 mug/ml. phi6 could attach to its host cell in the presence of myristic acid at 50 mug/ml. We conclude that the fatty acids that prevent phi6 replication probably do so by interfering with the entry of the viral genome into the host cell.

Phase transition in a lipid bilayer. II. Influence of adamantane derivatives

The influence of thirty-four adamantane, protoadamantane, and homoadamantane derivatives on the phase transition characteristics of the bilayer in dipalmitoyl lecithin liposomes has been determined by differential scanning calorimetry. Each of these compounds induces a broadening of the phase transition profile of the lipid bilayer that is dependent upon the concentration of the solute and its molecular structure. The concentration--response curves obtained for these solutes suggest that the cage compound derivatives modify the phase properties and under some conditions may induce a phase separation in the doped bilayer. The relative activity sequences obtained for the compounds examined cannot be accounted for by simple considerations of lipid/water partition coefficients, substitution constants based on free energy relationships, or the relative polarities or sizes of substituent groups. The observations are consistent with the hypothesis that the position and orientation of a solute within the bilayer are critical factors in determining its relative potency. The position of a solute within the bilayer is significantly controlled by the presence of polar substituents and by the relative geometric relationships of these groups. For a given substituent group, the shape and size of the hydrocarbon cage becomes increasingly important. It is apparent that seemingly minor modifications in the structure of a solute can significantly alter its influence on the phase transition behavior of a bilayer.