Protection of neuronal cells against reactive oxygen species by carnosine and related compounds

Carnosine and related compounds were compared in terms of their abilities to decrease the levels of reactive oxygen species (ROS) in suspensions of isolated neurons activated by N-methyl-D-aspartic acid (NMDA) using both stationary fluorescence measurements and flow cytometry. Carnosine was found to suppress the fluorescent signal induced by ROS production and decreased the proportion of highly fluorescent neurons, while histidine showed opposite effects. N-Acetylated derivatives of both carnosine and histidine demonstrated weak (statistically indistinguishable) suppressive effects on the ROS signal. N-Methylated derivatives of carnosine suppressed intracellular ROS generation to the same extent as carnosine. This rank of effectiveness is distinct from that previously obtained for the anti-radical ability of CRCs (anserine>carnosine>ophidine). These differences suggest that the similar ability of carnosine and its N-methylated derivatives to protect neuronal cells against the excitotoxic effect of NMDA is not solely related to the antioxidant properties of these compounds.     

Developmental changes in regulation of mitochondrial respiration by ADP and creatine in rat heart in vivo

In saponin-skinned muscle fibers from adult rat heart and m. soleus the apparent affinity of the mitochondrial oxidative phosphorylation system for ADP (K_m = 200-400 M) is much lower than in isolated mitochondria (K_m = 10-20 M). This suggests a limited permeability of the outer mitochondrial membrane (OMM) to adenine nucleotides in slow-twitch muscle cells. We have studied the postnatal changes in the affinity of mitochondrial respiration for ADP, in relation to morphological alterations and expression of mitochondrial creatine kinase (mi-CK) in rat heart in vivo. Analysis of respiration of skinned fibers revealed a gradual decrease in the apparent affinity of mitochondria to ADP throughout 6 weeks post partum that indicates the development of mechanism which increasingly limits the access of ADP to mitochondria. The expression of mi-CK started between the 1st and 2nd weeks and reached the adult levels after 6 weeks. This process was associated with increases in creatine-activated respiration and affinity of oxidative phosphorylation to ADP thus reflecting the progressive coupling of mi-CK to adenine nucleotide translocase. Laser confocal microscopy revealed significant changes in rearrangement of mitochondria in cardiac cells: while the mitochondria of variable shape and size appeared to be random-clustered in the cardiomyocytes of 1 day old rat, they formed a fine network between the myofibrils by the age of 3 weeks. These results allow to conclude that in early period of development, i.e. within 2-3 weeks, the diffusion of ADP to mitochondria becomes progressively restricted, that appears to be related to significant structural rearrangements such as formation of the mitochondrial network. Later (after 3 weeks) the control shifts to mi-CK, which by coupling to adenine nucleotide translocase, allows to maximally activate the processes of oxidative phosphorylation despite limited access of ADP through the OMM.     

Longer life span is associated with elevated immune activity in a seasonally polyphenic butterfly

Seasonal polyphenism constitutes a specific type of phenotypic plasticity in which short‐lived organisms produce different phenotypes in different times of the year. Seasonal generations of such species frequently differ in their overall lifespan and in the values of traits closely related to fitness. Seasonal polyphenisms provide thus excellent, albeit underused model systems for studying trade‐offs between life‐history traits. Here, we compare immunological parameters between the two generations of the European map butterfly (Araschnia levana), a well‐known example of a seasonally polyphenic species. To reveal possible costs of immune defence, we also examine the concurrent differences in several life‐history traits. Both in laboratory experiments and in the field, last instar larvae heading towards the diapause (overwintering) had higher levels of both phenoloxidase (PO) activity and lytic activity than directly developing individuals. These results suggest that individuals from the diapausing generation with much longer juvenile (pupal) period invest more in their immune system than those from the short‐living directly developing generation. The revealed negative correlation between pupal mass and PO activity may be one of the reasons why, in this species, the diapausing generation has a smaller body size than the directly developing generation. Immunological parameters may thus well mediate trade‐offs between body size‐related traits.     

Searching for constraints by cross‐species comparison: reaction norms for age and size at maturity in insects

An evolutionary explanation should consider the balance between environmentally‐based selective pressures, and the resistance of the organism's phenotype to adaptive evolution, with the latter being captured by the concept of constraint. The limited attention to non‐adaptive explanations in evolutionary ecology is at least partly caused by methodological difficulties with respect to identifying and quantifying constraints. As an example of an experimental approach evaluating a constraint‐based explanation, we present a cross‐species comparison of the shape of reaction norms for size and age at maturity. Instar‐ and sex‐specific development times and final sizes were recorded for two distantly‐related species of insects (Lepidoptera), with larval growth rates being manipulated by means of refined starvation treatments. We found that (1) the ‘classical’ L‐shaped reaction norms for final size and development time are characteristic also of individual larval instars; (2) these responses show a high degree of quantitative similarity across the species, different larval instars, and sexes within species; and (3) the similarity among species and sexes is higher for the penultimate than for the final instar. The high degree of similarity suggests that some physiological mechanisms determining such reaction norms are evolutionarily conservative. An alternative explanation (i.e. quantitative similarity of ecologically based selective pressures) appears less likely. The results of a previous study on a third lepidopteran species not only support our general conclusions, but also provide a clear case of adaptive evolution in some aspects of such reaction norms. The present study shows one way how the data required to measure evolutionary conservatism in reaction norms for body size can be obtained empirically. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2015, 114 , 296–307.     

Tracing the Route of Modern Humans out of Africa by Using 225 Human Genome Sequences from Ethiopians and Egyptians

The predominantly African origin of all modern human populations is well established, but the route taken out of Africa is still unclear. Two alternative routes, via Egypt and Sinai or across the Bab el Mandeb strait into Arabia, have traditionally been proposed as feasible gateways in light of geographic, paleoclimatic, archaeological, and genetic evidence. Distinguishing among these alternatives has been difficult. We generated 225 whole-genome sequences (225 at 8× depth, of which 8 were increased to 30×; Illumina HiSeq 2000) from six modern Northeast African populations (100 Egyptians and five Ethiopian populations each represented by 25 individuals). West Eurasian components were masked out, and the remaining African haplotypes were compared with a panel of sub-Saharan African and non-African genomes. We showed that masked Northeast African haplotypes overall were more similar to non-African haplotypes and more frequently present outside Africa than were any sets of haplotypes derived from a West African population. Furthermore, the masked Egyptian haplotypes showed these properties more markedly than the masked Ethiopian haplotypes, pointing to Egypt as the more likely gateway in the exodus to the rest of the world. Using five Ethiopian and three Egyptian high-coverage masked genomes and the multiple sequentially Markovian coalescent (MSMC) approach, we estimated the genetic split times of Egyptians and Ethiopians from non-African populations at 55,000 and 65,000 years ago, respectively, whereas that of West Africans was estimated to be 75,000 years ago. Both the haplotype and MSMC analyses thus suggest a predominant northern route out of Africa via Egypt.     

High penetrance of sequencing errors and interpretative shortcomings in mtDNA sequence analysis of LHON patients

For identifying mutation(s) that are potentially pathogenic it is essential to determine the entire mitochondrial DNA (mtDNA) sequences from patients suffering from a particular mitochondrial disease, such as Leber hereditary optic neuropathy (LHON). However, such sequencing efforts can, in the worst case, be riddled with errors by imposing phantom mutations or misreporting variant nucleotides, and moreover, by inadvertently regarding some mutations as novel and pathogenic, which are actually known to define minor haplogroups. Under such circumstances it remains unclear whether the disease-associated mutations would have been determined adequately. Here, we re-analyse four problematic LHON studies and propose guidelines by which some of the pitfalls could be avoided.     

A study on growth characteristics and nutrient consumption of Lactobacillus plantarum in A-stat culture

Lactobacillus plantarum was grown in complex media containing glucose and yeast extract. The maximum growth yield based on yeast extract consumption was 0.5 g dwt g^-1. Growth yield Y_ATP 15–17 g dwt mol ATP^-1 was almost constant in the glucose limited A-stat experiment whereas in the yeast extract limited culture it increased with dilution rate. The maximum specific growth rate observed, 0.5 h^-1, was similar for both A-stat and batch cultures. Specific oxygen consumption, Q_O2, reached the value of 1.8 mmol O₂ h^-1 g dwt^-1. It was shown that Val, Ile, Leu, Tyr and Phe, were consumed mainly as free amino acids, while Asp, Pro, Lys and Arg were derived from peptides. Significantly more Asp, Ser, Glu, Val, Ile, Leu and Phe were consumed than needed to build up cell protein whereas some Pro, Gly, Ala and Lys was synthesized. A network of metabolic reactions in L. plantarum was proposed on the basis of the experimental data.