Investigation of erythrocyte shape, plasma membrane fluidity and conformation of haemoglobin haemoporphyrin under the influence of long-term space flight

The investigation of long-term space flight (SF) effect on the blood cells function is of great importance for modern space biology and medicine. We established that the number of discocytes decreased in the period of early rehabilitation after long-term SF. After SF plasma membrane fluidity and phospholipid content decreased and cholesterol content increased. After SF the amount of haemoglobin decreased and the parameters characterizing haemoglobin haemoporyphyrin (HH) conformation changed. We suppose that erythrocyte shape, membrane fluidity and HH conformation are among factors affecting oxygen transfer during and after space flight.     

Resource density regulates the foraging investment in higher termite species

1. Resource density can regulate the area that animals use. At low resource density, there is a conflict in terms of balance between costs of foraging and benefits acquired. The foraging of the higher termite Nasutitermes aff. coxipoensis consists of searching throughout trails and a building galleries phase. 2. In this study, a manipulative field experiment was used to test the hypothesis that colonies of N. aff. coxipoensis forage towards a more profitable balance between the establishment of trails and gallery construction at low resource density. 3. The experiment was conducted in north‐eastern Brazil. Seven experimental plots were established with a continuous increase in resource density (sugarcane baits). Entire colonies of N. aff. coxipoensis were transplanted from their original sites to the experimental plot, totalling 35 nests. The number, branches and total length of trails and galleries were quantified. 4. The results show that N. aff. coxipoensis optimises its foraging output, intensifying the establishment of trails at the cost of gallery construction when resource density is low. The number of trails, the number of trail branches and the total length of trails decreased with increasing resource density. Interestingly, at low resource density, the search effort was concentrated on forming longer and a greater number of trails, a small proportion of which were converted into galleries. The opposite relationship was observed at high resource density. 5. These results suggest an optimisation of search efforts during foraging depending on resource density, a mechanism that may help researchers to understand the use of space by higher termite species.     

The effect of melatonin and epiphysectomy on the function of the mono-oxygenase system in rat liver

After chronic melatonin administration (1 mg/kg, 14 days) the content of cytochrome P-450 and activity of NADPH: cytochrome c-reductase in rat microsomes were increased. Pinealectomized rats had opposite directed shifts in microsomal oxidation. In these animals activated effect of melatonin was absent.     

Base pair conformation-dependent excision of benzo[a]pyrene diol epoxide-guanine adducts by human nucleotide excision repair enzymes.

Human nucleotide excision repair processes carcinogen-DNA adducts at highly variable rates, even at adjacent sites along individual genes. Here, we identify conformational determinants of fast or slow repair by testing excision of N2-guanine adducts formed by benzo[a]pyrene diol epoxide (BPDE), a potent and ubiquitous mutagen that induces mainly G x C-->T x A transversions and frameshift deletions. We found that human nucleotide excision repair processes the predominant (+)-trans-BPDE-N2-dG adduct 15 times less efficiently than a standard acetylaminofluorene-C8-dG lesion in the same sequence. No difference was observed between (+)-trans- and (-)-trans-BPDE-N2-dG, but excision was enhanced about 10-fold by changing the adduct configurations to either (+)-cis- or (-)-cis-BPDE-N2-dG. Conversely, excision of (+)-cis- and (-)-cis- but not (+)-trans-BPDE-N2-dG was reduced about 10-fold when the complementary cytosine was replaced by adenine, and excision of these BPDE lesions was essentially abolished when the complementary deoxyribonucleotide was missing. Thus, a set of chemically identical BPDE adducts yielded a greater-than-100-fold range of repair rates, demonstrating that nucleotide excision repair activity is entirely dictated by local DNA conformation. In particular, this unique comparison between structurally highly defined substrates shows that fast excision of BPDE-N2-dG lesions is correlated with displacement of both the modified guanine and its partner base in the complementary strand from their normal intrahelical positions. The very slow excision of carcinogen-DNA adducts located opposite deletion sites reveals a cellular strategy that minimizes the fixation of frameshifts after mutagenic translesion synthesis.     

Polycationic amphiphiles based on triethylenetetramine and their transfection efficacy

Novel polycationic amphiphiles derived from triethylenetetramine, a spermine analogue, containing cholesterol or dialkylglycerol residues as hydrophilic domains were synthesized. The amphiphiles and a helper lipid 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine) served for the preparation of cationic liposomes, physicochemical properties of which were evaluated. A comparative study of cytotoxicity and transfection efficiency demonstrated that the replacement of spermine by triethylenetetramine decreased transfection activity of cationic liposomes.     

Interaction of nonelectrolytes, the derivatives of 5-hydroxybenzimidazole, with erythrocyte membrane

The method of spin probe and scanning electron microscopy were used to study the effects of some new synthetic antioxidants and bioregulators, the derivatives of 5-hydroxybenzimidazole, on the membrane structure and morphology of erythrocytes. Analysis of EPR spectra and electron micrographs revealed that the derivatives with various side substituents affect the membrane structure and shape of erythrocytes in a concentration-dependent manner, the effect correlating with the hydrophobic properties of the side derivatives. It was shown that all the compounds in the concentration range 1.10(-7) - 1.10(-3) M exhibit the echinocytogenic action, the most profound effect being found in the compound with benzyl- and ethoxygroup in sites 2 and 5, respectively. Our data suggest that nonelectrolytes, the derivatives of 5-hydroxybenzimidazole, are located in the outer monolayer of erythrocyte membrane.     

Features of organic nonelectrolyte binding to the erythrocyte membrane

The capacity of erythrocyte membranes for organic nonelectrolytes from different chemical groups of chemical compounds was studied by the spin probe method and scanning electron microscopy. Hydrophobic spin-labeled derivatives of gamma-carbolin and stearic acid and the screened phenol antioxidant fenozan-1 were used as nonelectrolytes. Based on the analysis of electron spin resonance spectra of the hydrophobic spin-labeled nonelectrolytes and electron micrographs of erythrocytes, differences in the capacity of distribution regions in the intramembrane space of the derivative of gamma-carbolin and fenozan-1, on the one hand, and the spin-labeled derivative of fatty acid, on the other hand, were found. The first group has at least two membrane distribution regions, whereas in the second case only one type of distribution was found. The influence of limited membrane capacity on the realization of biological activity of organic nonelectrolytes is discussed.     

Donor activity of methicillin resistant staphylococci in transduction experiments]

Antibiotic resistance gene transmission from methicillin resistant strains of Staphylococcus aureus (MRSA), isolated in a burn care unit, was studied in transduction experiments with type phages 29, 52, 52A and in experiments with prophage induction. The results of the experiments demonstrated high donor activity of MRSA. Recombinants with different antibiotic resistance phenotypes were revealed, but there were no methicillin resistant staphylococci among them. Stability of cloramphenicol resistance gene transmission in the experiments on specific transduction with the prophage induction could be indicative of the prophage localization near the chloramphenicol resistance genes. Variety of the antibiotic resistance combinations in the transductants from the clinical strains of MRSA could prove heterogeneity of the strains even under conditions of one hospital.     

Structure of a high fidelity DNA polymerase bound to a benzo[a]pyrene adduct that blocks replication

Of the carcinogens to which humans are most frequently exposed, the polycyclic aromatic hydrocarbon benzo[a]pyrene (BP) is one of the most ubiquitous. BP is a byproduct of grilled foods and tobacco and fuel combustion and has long been linked to various human cancers, particularly lung and skin. BP is metabolized to diol epoxides that covalently modify DNA bases to form bulky adducts that block DNA synthesis by replicative or high fidelity DNA polymerases. Here we present the structure of a high fidelity polymerase from a thermostable strain of Bacillus stearothermophilus (Bacillus fragment) bound to the most common BP-derived N2-guanine adduct base-paired with cytosine. The BP adduct adopts a conformation that places the polycyclic BP moiety in the nascent DNA minor groove and is the first structure of a minor groove adduct bound to a polymerase. Orientation of the BP moiety into the nascent DNA minor groove results in extensive disruption to the interactions between the adducted DNA duplex and the polymerase. The disruptions revealed by the structure of Bacillus fragment bound to a BP adduct provide a molecular basis for rationalizing the potent blocking effect on replication exerted by BP adducts.