Cell Penetrating Peptides: How Do They Do It?

Cell penetrating peptides consist of short sequences of amino acids containing a large net positive charge that are able to penetrate almost any cell, carrying with them relatively large cargoes such as proteins, oligonucleotides, and drugs. During the 10 years since their discovery, the question of how they manage to translocate across the membrane has remained unanswered. The main discussion has been centered on whether they follow an energy-independent or an energy-dependent pathway. Recently, we have discovered the possibility of an energy-independent pathway that challenges fundamental concepts associated with protein-membrane interactions (Herce and Garcia, PNAS, 104: 20805 (2007) [1]). It involves the translocation of charged residues across the hydrophobic core of the membrane and the passive diffusion of these highly charged peptides across the membrane through the formation of aqueous toroidal pores. The aim of this review is to discuss the details of the mechanism and interpret some experimental results consistent with this view.     

Do Bumblebees Forage Optimally, and Does It Matter?

Foraging behavior of bumblebees has been in the past analyzedfrom two major perspectives. On the one hand, behavioral mechanismshave been studied to learn more about the animal. On the otherextreme, the animal has been used incidentally to examine optimalforaging theory (O.F.T.). Major problems have arisen when theorydesigned to answer evolutionary questions was used to determineproximal mechanisms. While O.F.T. could be highly useful inmaking predictions to point out useful problems, the bottleneckto our understanding at the present resides in the lack of experimentsthat test alternative hypotheses. Whether or not a bumblebee worker's foraging behavior is adaptive(enhances fitness), however, or is optimal (maximizes fitness)cannot yet be resolved by observations or experimentation onindividual bees. However, calculations can show the potentialenergy costs and payoffs of alternative potential foraging behaviors.Rapid progress could be made by examining the mechanisms offoraging behavior that act to enhance foraging returns, withoutworrying about whether or not the behavior is "optimal."     

When Do Metal Complexes Protect the Biological System from Superoxide Toxicity and When Do They Enhance It?

Many copper and iron complexes can be reduced by O^-₂ as well as by H₂O₂. According to the rates of reduction and the concentration of O^-₂ and H₂O₂, the metal complexes may serve either as catalyst of O^-₂ dismutation or as catalysts of the reaction between O^-₂ and H₂O₂ to form OH' radical (Haber-Weiss reaction). Various factors which influence whether metal complexes protect the biological systems from superoxide toxicity or enhance it are discussed.     

Response to comments by V. N. Manskikh: “Do external or internal factors lead to tumor development? It is still unknown”

The opinion is presented according to which the “bad luck” hypothesis (Tomasetti, C., and Vogelstein, B. (2015) Science, 347, 78–81), which has recently received experimental confirmation, has the right to exist, and its criticisms are largely unfounded.     

Do external or internal factors lead to tumor development? It is still unknown

Arguments supporting the “bad luck” hypothesis presented by C. Tomasetti and B. Vogelstein ((2015) Science, 347, 78–81) and A. V. Lichtenstein ((2017) Biochemistry (Moscow), 82, 75–80) are critically discussed. Those arguments are not sufficient for recognition of the “bad luck” hypothesis and the leading role of internal factors in spontaneous tumor development.     

More Productive Than Maize in the Midwest: How Does Miscanthus Do It?

In the first side-by-side large-scale trials of these two C₄ crops in the U.S. Corn Belt, Miscanthus (Miscanthus × giganteus) was 59% more productive than grain maize (Zea mays). Total productivity is the product of the total solar radiation incident per unit land area and the efficiencies of light interception (ε_i) and its conversion into aboveground biomass (ε_ca). Averaged over two growing seasons, ε_ca did not differ, but ε_i was 61% higher for Miscanthus, which developed a leaf canopy earlier and maintained it later. The diurnal course of photosynthesis was measured on sunlit and shaded leaves of each species on 26 dates. The daily integral of leaf-level photosynthetic CO₂ uptake differed slightly when integrated across two growing seasons but was up to 60% higher in maize in mid-summer. The average leaf area of Miscanthus was double that of maize, with the result that calculated canopy photosynthesis was 44% higher in Miscanthus, corresponding closely to the biomass differences. To determine the basis of differences in mid-season leaf photosynthesis, light and CO₂ responses were analyzed to determine in vivo biochemical limitations. Maize had a higher maximum velocity of phosphoenolpyruvate carboxylation, velocity of phosphoenolpyruvate regeneration, light saturated rate of photosynthesis, and higher maximum quantum efficiency of CO₂ assimilation. These biochemical differences, however, were more than offset by the larger leaf area and its longer duration in Miscanthus. The results indicate that the full potential of C₄ photosynthetic productivity is not achieved by modern temperate maize cultivars.     

Fine needle aspiration of borderline ovarian lesions. Is It useful?

Borderline ovarian tumors are a low grade form of epithelial ovarian carcinoma with a low rate of growth and a low potential to invade or metastasize. According to the new World Health Organization classification, these tumors are placed between clearly benign and obviously malignant tumors because they exhibit some, but not all, of the morphologic features of malignancy. For a distinction between borderline lesions and cystadenomas or carcinomas, 2 criteria are of the utmost importance: presence of nuclear atypia and absence of stromal invasion. The pathologic subtype ofperitoneal implants is probably one of the main prognosticfactors in patients with serous tumors of low malignant potential, while the prognostic value of micropapillary serous carcinoma in patients with noninvasive implants remains debatable. Although fine needle aspiration (FNA) is the most accurate diagnostic method in cytopathology, its value in the diagnosis of borderline lesions is limited, mainly because of its inability to establish the absence of stromal invasion. The diagnostic accuracy of RNA can be improved by supplementing cytologic examination with such diagnostic techniques as immunocytochemistry and cytometry.     

Source-sink partitioning. Do we need Münch?

The simulation of phloem translocation by the Münch theory commonly uses resistances from sources to sinks: the resistances are therefore regarded as important in partitioning. Although resistance is generally a set constant, it is in fact strongly affected by viscosity, and thus the concentration of the transported solute. In this paper, the model of partitioning proposed by Minchin et al. was first corrected for variations in viscosity. The model was further modified, with the source considered as an activity of solute production rather than as a compartment concentration. When so defined, the source cannot differ from the sum of sink activities, largely outdating the source- or sink-limitation concepts. The corrected model confined the effect of resistances on the partitioning to low source activities. In the example of wheat grain filling analysed, such activities would be so low that they would correspond only to pathological conditions. In that case, the use of resistances in modelling is therefore just a mathematical burden, not even easily quantifiable since they are related to anatomical traits that are difficult to access. Leaving out resistances, it becomes easy to calculate the sink activities directly from the source activities, using an intuitive, accessible parametrization. The conditions for such a simplification are discussed.     

Do species of Crataegus sect. Sanguineae occur in Iran?

Results of a revision of Iranian species of Crataegus section Sanguineae are presented here. Previously, two species of this section, C. sanguinea Pall. and C. babakhanloui Khat., were reported from Iran. However, detailed analyses of morphological and micro‐morphological characteristics, as well as phytogeographical data, could not confirm this information; herbarium specimens recognised as C. sanguinea appeared to be C. pentagyna Waldst. & Kit. (C. sect. Pentagynae), while C. babakhanloui should be included in the C. section Crataegus. The section Sanguineae is represented in Iran only by C. wattiana Hemsl. & Lace, the presence of which is reported here for the first time.     

Do pollinators influence seed-set in Banksia paludosa Sm. and Banksia spinulosa R. Br.?

The consequences of observed variations in pollinator activity for plant reproduction depend on the breeding system of the plant and also on whether pollination is a resource in short supply. These factors are frequently assumed rather than tested. In bagging experiments with Banksia paludosa in heath and B. spinulosa var. spinulosa in woodland, the present study demonstrated that seed-set does not occur by autogamy and that pollinators are indeed necessary. Experimental addition of outcrossed pollen to inflorescences failed to produce any increase in the mean number of seeds per inflorescence, measured for non-barren inflorescences, for either species. However, in B. paludosa, the addition of pollen increased the numbers of inflorescences that set seed from 20% (controls) to 45% (pollen-added treatment). This suggests either unusual patterns of pollen movement among and within plants or control of the pattern of seed-set within a plant. Pollen additions failed to alter seed-set in B. spinulosa. It is possible that a greater abundance of pollinators in the woodland ensures adequate pollination for these plants     

Populus: arabidopsis for forestry. Do we need a model tree?

Trees are used to produce a variety of wood-based products including timber, pulp and paper. More recently, their use as a source of renewable energy has also been highlighted, as has their value for carbon mitigation within the Kyoto Protocol. Relative to food crops, the domestication of trees has only just begun; the long generation time and complex nature of juvenile and mature growth forms are contributory factors. To accelerate domestication, and to understand further some of the unique processes that occur in woody plants such as dormancy and secondary wood formation, a 'model' tree is needed. Here it is argued that Populus is rapidly becoming accepted as the 'model' woody plant and that such a 'model' tree is necessary to complement the genetic resource being developed in arabidopsis. The genus Populus (poplars, cottonwoods and aspens) contains approx. 30 species of woody plant, all found in the Northern hemisphere and exhibiting some of the fastest growth rates observed in temperate trees. Populus is fulfilling the 'model' role for a number of reasons. First, and most important, is the very recent commitment to sequence the Populus genome, a project initiated in February 2002. This will be the first woody plant to be sequenced. Other reasons include the relatively small genome size (450-550 Mbp) of Populus, the large number of molecular genetic maps and the ease of genetic transformation. Populus may also be propagated vegetatively, making mapping populations immortal and facilitating the production of large amounts of clonal material for experimentation. Hybridization occurs routinely and, in these respects, Populus has many similarities to arabidopsis. However, Populus also differs from arabidopsis in many respects, including being dioecious, which makes selfing and back-cross manipulations impossible. The long time-to-flower is also a limitation, whilst physiological and biochemical experiments are more readily conducted in Populus compared with the small-statured arabidopsis. Recent advances in the development of large expressed sequence tagged collections, microarray analysis and the free distribution of mapping pedigrees for quantitative trait loci analysis secure Populus as the ideal subject for further exploitation by a wide range of scientists including breeders, physiologists, biochemists and molecular biologists. In addition, and in contrast to other model plants, the genus Populus also has genuine commercial value as a tree for timber, plywood, pulp and paper.