13C-NMR study of CO2-fixation during the heterotrophic growth in Chlorobium thiosulfatophilum

The functioning of the biosynthetic pathways of the amino acids alanine, glycine, aspartic acid, glutamic acid and tyrosine, and of nucleosides in the photosynthetic bacterium Chlorobium thiosulfatophilum during heterotrophic growth on ¹³CO₂ and unlabelled acetate was investigated using ¹³C-NMR as the method for determination of the labelling patterns of the separated substances. On the basis of the analysis of the multiplet structure of the spectra of the tightly-coupled systems, the conclusion was drawn that the Calvin cycle does not function in the experimental conditions used. The labelling pattern of the glutamic acid indicated that about 30% of the amino acid molecules were synthesized through the reactions of the reductive carboxylic acid cycle, the remaining 70% being derived from oxaloacetate and exogenous acetate through the reactions of the Krebs cycle. Labelling patterns of the nucleosides were in agreement with their known biosynthetic pathways.     

Nerve growth factor-induced rapid reorganization of microfilaments in PC12 cells: Possible roles of different second messenger systems

Nerve growth factor (NGF) induces in 2 to 10 min the redistribution of F-actin in rat pheochromocytoma PC12 cells. The NGF specificity of this phenomenon was shown by blocking it with anti-NGF antibodies. We used the rapid F-actin redistribution as an assay to study NGF second messenger systems and their inhibition or activation by specific agents. The results show that the NGF-induced effect on the microfilament system of PC12 cells can be specifically inhibited by lithium chloride and neomycin, inhibitors of the phosphoinositol system, but cannot be mimicked by TPA and acetylcholine, the activators of the phosphoinositol system. An increase in the intracellular concentration of cyclic AMP by addition of dBcAMP (but not dBcGMP) caused rapid F-actin redistribution that nonetheless differed from the NGF-induced effect. Changes in the intracellular calcium level did not have any influence on the microfilament system of PC12 cells. The specificity of the inhibition of NGF-induced effects by methylase inhibitors was questionable, since MTA- or SAH-treated PC12 cells acquired an altered morphology even in the absence of NGF or dBcAMP. Using the microfilament- and microtubule-disrupting drugs cytochalasin B and colchicine, we showed that the microtubule system in PC12 cells is required for the initiation of neurite outgrowth and that microfilament-associated filopodial activity does not appear to be necessary.     

Host ant use of the Alcon blue butterfly at the northern range margin

In myrmecophilous insects, interactions with ants are often a key factor determining persistence of their populations. Regional variation in host ant use is therefore an essential aspect to consider to provide adequate conservation practices for such species. In this study, we examined this important facet of species’ ecology in an endangered myrmecophilous butterfly Phengaris (=Maculinea) alcon (Lepidoptera, Lycaenidae). The investigations conducted in peripheral populations in Estonia allowed us to expand the knowledge of its host ant use to the northern distribution limit of the species. Our data indicate that in its northernmost populations, the xerophilous ecotype of Phengaris alcon is primarily parasitizing a single host ant species, Myrmica schencki. The data collected are in line with the emerging evidence suggesting that peripheral and core populations of P. alcon use different host ants, and peripheral populations tend to display higher host ant specificity. We also show that, at its northern range margin, P. alcon might be more limited by the availability of its sole larval food plant in the region, Gentiana cruciata, than the densities of its host ant. Finally, we found a strong negative correlation between Myrmica spp. and Lasius spp. colony densities, suggesting that interspecific competition between ants could have a substantial influence on host ant availability of Phengaris butterflies, and thus should be taken into account in conservation plans of these species.     

Effect of stress pretreatment on survival of probiotic bacteria in gastrointestinal tract simulator

The effect of stress pretreatment on survival of probiotic Lactobacillus acidophilus La-5, Lactobacillus rhamnosus GG, and Lactobacillus fermentum ME-3 cultures was investigated in the single bioreactor gastrointestinal tract simulator (GITS). The cultures were pregrown in pH-auxostat, subjected to temperature, acid, or bile stress treatment, fast frozen in liquid nitrogen (LN₂), and tested for survival in GITS. After LN₂ freezing the colony forming ability of L. rhamnosus GG and L. fermentum ME-3 nonstressed and stressed cells was well retained (average survival of 75.4 ± 18.3% and 88.0 ± 7.2%, respectively). L. acidophilus La-5 strain showed good survival of auxostat nonstressed cells after fast freezing (94.2 ± 15.0), however the survival of stress pretreated cells was considerably lower (30.8 ± 8.5%). All LN₂ frozen auxostat cultures survived well in the acid phase of the GIT simulation (survival 81 ± 21%); however, after the bile phase, the colony formation ability of L. acidophilus La-5, L. rhamnosus GG, and L. fermentum ME-3 decreased by approximately 1.4 ± 0.2, 3.8 ± 0.3, and 3.5 ± 1.2 logarithmic units, respectively. No statistically relevant positive effect of stress pretreatments on survival of LN₂ frozen L. acidophilus La-5, L. rhamnosus GG, and L. fermentum ME-3 in GITS was observed.     

Age and size at maturity: A quantitative review of diet‐induced reaction norms in insects

Optimality models predict that diet‐induced bivariate reaction norms for age and size at maturity can have diverse shapes, with the slope varying from negative to positive. To evaluate these predictions, we perform a quantitative review of relevant data, using a literature‐derived database of body sizes and development times for over 200 insect species. We show that bivariate reaction norms with a negative slope prevail in nearly all taxonomic and ecological categories of insects as well as in some other ectotherm taxa with comparable life histories (arachnids and amphibians). In insects, positive slopes are largely limited to species, which feed on discrete resource items, parasitoids in particular. By contrast, with virtually no meaningful exceptions, herbivorous and predatory insects display reaction norms with a negative slope. This is consistent with the idea that predictable resource depletion, a scenario selecting for positively sloped reaction norms, is not frequent for these insects. Another source of such selection—a positive correlation between resource levels and juvenile mortality rates—should similarly be rare among insects. Positive slopes can also be predicted by models which integrate life‐history evolution and population dynamics. As bottom‐up regulation is not common in most insect groups, such models may not be most appropriate for insects.     

Novel guanidine-based inhibitors of inosine monophosphate dehydrogenase

A series of novel guanidine-based small molecule inhibitors of inosine monophosphate dehydrogenase (IMPDH) was explored. IMPDH catalyzes the rate determining step in guanine nucleotide biosynthesis and is a target for anticancer, immunosuppressive and antiviral therapy. The synthesis and the structure-activity relationships (SARs), derived from in vitro studies, for this new series of inhibitors is given.     

A "Copernican" reassessment of the human mitochondrial DNA tree from its root

Mutational events along the human mtDNA phylogeny are traditionally identified relative to the revised Cambridge Reference Sequence, a contemporary European sequence published in 1981. This historical choice is a continuous source of inconsistencies, misinterpretations, and errors in medical, forensic, and population genetic studies. Here, after having refined the human mtDNA phylogeny to an unprecedented level by adding information from 8,216 modern mitogenomes, we propose switching the reference to a Reconstructed Sapiens Reference Sequence, which was identified by considering all available mitogenomes from Homo neanderthalensis. This “Copernican” reassessment of the human mtDNA tree from its deepest root should resolve previous problems and will have a substantial practical and educational influence on the scientific and public perception of human evolution by clarifying the core principles of common ancestry for extant descendants.