Mutants of the phototrophic bacteria Rhodobacter sphaeroides sensitive to the mutagenic action of long-wave ultraviolet light

The mutagenic action of near ultraviolet (NUV, greater than or equal to 280) nm) on purple phototrophic soil bacteria Rhodobacter sphaeroides: wild strain 2R and 12 mutants obtained earlier sensitive to UV derivates (UVS) was investigated. The mutagenic action of NUV was measured by induction of resistance to tetracycline (Tet) and nalidixic acid (Nal) and reversion of pigment mutants to wild-type phenotype. The NUV light induces the mutations of resistance to Nal and Tet in wild-type strain 2R; the UVS mutants differed greatly in their NUV-induced mutability. Three UVS mutants were characterized by greatly increased mutability in all analysed loci; slight mutability was found in seven mutants. On the basis of the data obtained it has been concluded that the UVS mutants R. sphaeroides can be used as test organisms in estimation of mutagenic activity of NUV. The molecular mechanisms and genetic control of NUV-induced mutagenesis are discussed.     

The effect of morphology upon electrophysiological responses of retinal ganglion cells: simulation results

Retinal ganglion cells (RGCs) display differences in their morphology and intrinsic electrophysiology. The goal of this study is to characterize the ionic currents that explain the behavior of ON and OFF RGCs and to explore if all morphological types of RGCs exhibit the phenomena described in electrophysiological data. We extend our previous single compartment cell models of ON and OFF RGCs to more biophysically realistic multicompartment cell models and investigate the effect of cell morphology on intrinsic electrophysiological properties. The membrane dynamics are described using the Hodgkin - Huxley type formalism. A subset of published patch-clamp data from isolated intact mouse retina is used to constrain the model and another subset is used to validate the model. Two hundred morphologically distinct ON and OFF RGCs are simulated with various densities of ionic currents in different morphological neuron compartments. Our model predicts that the differences between ON and OFF cells are explained by the presence of the low voltage activated calcium current in OFF cells and absence of such in ON cells. Our study shows through simulation that particular morphological types of RGCs are capable of exhibiting the full range of phenomena described in recent experiments. Comparisons of outputs from different cells indicate that the RGC morphologies that best describe recent experimental results are ones that have a larger ratio of soma to total surface area.     

Morphological,molecular and biological evidence reveal two cryptic species in Mecinus janthinus Germar (Coleoptera,Curculionidae), a successful biological control agent of Dalmatian toadflax,Linaria dalmatica (Lamiales,Plantaginaceae)

A combined morphological, molecular and biological study shows that the weevil species presently named Mecinus janthinus is actually composed of two different cryptic species: M. janthinus Germar, 1821 and M. janthiniformis To?evski & Caldara sp.n. These species are morphologically distinguishable from each other by a few very subtle morphological characters. On the contrary, they are more readily distinguishable by both molecular and biological characters. A molecular assessment based on the mitochondrial DNA cytochrome oxidase subunit II gene revealed fixed differences between the two species with p‐distances between samples of both species ranging from 1.3 to 2.4%. In addition to this, the larvae of the two species are found to develop on different species within the genus Linaria (Plantaginaceae): M. janthinus is associated with yellow toadflax (L. vulgaris) and M. janthiniformis with broomleaf toadflax (L. genistifolia) and Dalmatian toadflax (L. dalmatica). Molecular and host use records further suggest the occurrence of a third species associated with L. vulgaris within M. janthinus, sampled from north Switzerland, central Hungary and east Serbia. The significance of these new findings is of particular importance because species of the M. janthinus group are used, or are potential candidates, for the biological control of invasive toadflaxes in North America.     

Lethal and mutagenic action of solar radiation on model microbiological test systems

Lethal, mutagenic and recombonogenic action of the solar radiation on the model microorganisms--phage T4, bacteria Escherichia coli and ascomycet Aspergillus nidulans--has been studied. A considerable lethal effect of the solar radiation on phage T4 and E. coli was found. An increasing of mutation frequency in E. coli and A. nidulans by sunlight was also revealed. Recombinogenic action of solar radiation has been demonstrated in the experiments with diploid A. nidulans strains. It was shown that the excision and postreplication repair systems took part in recovery of damages induced by sunlight. An important role of ultra-violet region (280-320 nm) solar radiation in induction of lethal and mutagenic effects was demonstrated for all investigated microorganisms.     

Synthesis and biological properties of D-homo-6-oxa-8α-analogues of steroid estrogens

Modifications of D-homo-6-oxa-8α-analogues of steroid estrogens were found to lead to a complete loss of the uterotropic and hypertriglyceridemic activities. These compounds may be promising for the design on their basis of inhibitors of the steroid hormone metabolism and transporters of other compounds to the estrogen target organs.     

Effect on the systemic hemodynamics of polymers that decrease hydrodynamic resistance

It has been shown that intravenous injections of drug-reducing polymers (at a dose of 2 x1 0(-6) g/ml) to rabbits produced a decrease in the total peripheral resistance with an increase in the cardiac output and simultaneous diminution of the mean blood pressure. These hemodynamic effects did not depend on vasodilatation as it had previously been shown. The alterations were retained for not less than 72 hours after one polymer injection; the effects were due to the influence of polymers on the flow structure.     

Host‐associated genetic divergence and taxonomy in the Rhinusa pilosa Gyllenhal species complex: an integrative approach

A combined taxonomic, morphological, molecular and biological study revealed that stem‐galling weevils from the genus Rhinusa associated with toadflaxes from the genus Linaria (Plantaginaceae) are composed of three different species: Rhinusa pilosa, Rhinusa brondelii and Rhinusa rara sp.n. The authentic field host plants are respectively, Linaria vulgaris, Linaria purpurea and Linaria genistifolia/ Linaria dalmatica. These weevil species can be distinguished from each other by a few subtle morphological characteristics, mainly in the shape of the rostrum and of the integument. An analysis of the mitochondrial [cytochrome oxidase subunit II gene (COII) and 16S ribosomal RNA gene (16S)] and nuclear (elongation factor‐1α, EF‐1α) sequence data revealed high genetic divergence among these species. Uncorrected pairwise distances on mtCOII gene were 14.3% between R. pilosa and R. brondelii, 15.7% between R. pilosa and R. rara, while R. brondelii and R. rara were approximately 11% divergent from each other. Divergences obtained on 16S and nuclear EF‐1α genes were congruent. However, substantial intraspecific mitochondrial divergence was recorded for all studied populations of R. pilosa s.s. showing two mtDNA lineages, with estimated COII and 16S divergences of 4% and 1.6%, respectively. Nuclear pseudogenes (Numts) and Wolbachia influence, although recorded within both lineages, were excluded as possible causatives of the mtDNA divergence, while EF‐1α indicated absence of lineage sorting. Species from the R. pilosa complex are estimated to have diverged from each other approximately 7.2 million years ago (mya; late Miocene), while R. brondelii and R. rara diverged from each other about 4.7 mya (early Pliocene). This published work has been registered in ZooBank, http://zoobank.org/urn:lsid:zoobank.org:pub:EEDD6248‐01DB‐4B4A‐B79D‐C5606393E3AA .