The role of mechanical resonance in the neural control of swimming in fishes

The bodies of many fishes are flexible, elastic structures; if you bend them, they spring back. Therefore, they should have a resonant frequency: a bending frequency at which the output amplitude is maximized for a particular input. Previous groups have hypothesized that swimming at this resonant frequency could maximize efficiency, and that a neural circuit called the central pattern generator might be able to entrain to a mechanical resonance. However, fishes swim in water, which may potentially damp out many resonant effects. Additionally, their bodies are elongated, which means that bending can occur in complicated ways along the length of the body. We review previous studies of the mechanical properties of fish bodies, and then present new data that demonstrate complex bending properties of elongated fish bodies. Resonant peaks in amplitude exist, but there may be many of them depending on the body wavelength. Additionally, they may not correspond to the maximum swimming speed. Next, we describe experiments using a closed-loop preparation of the lamprey, in which a preparation of the spinal cord is linked to a real-time simulation of the muscle and body properties, allowing us to examine resonance entrainment as we vary the simulated resonant frequency. We find that resonance entrainment does occur, but is rare. Gain had a significant, though weak, effect, and a nonlinear muscle model produced resonance entrainment more often than a linear filter. We speculate that resonance may not be a critical effect for efficient swimming in elongate, anguilliform swimmers, though it may be more important for stiffer carangiform and thunniform fishes.     

Cities and social participation: Social inequalities from children's and youth's point of view

Social participation, as far as children and youth are concerned, stands as one of the rights of children formalized by the Convention on the Rights of the Child. The present work is an attempt to contribute to the discussion on the ways whereby this right can be implemented, by raising the issue that children and youth constructively interpret social differences as a main feature of cities by providing explanations of social inequalities and their remedial mechanisms. Three case studies based on an action research invervention in three different institutions are presented. The analysis of focal group discussions with children and youth highlight their perspectives about life in the city: the city that they lived in and the city as they would like it to be demonstrating how children's and youth's views can provide a deep and critical understanding of their own society and the ways to change it.     

Biostructural theory of the living systems

Eugen Macovschi is among the few scientists who tried, and partly succeeded, to explain the differences between "dead" and "living" in biological sciences. He discovered and characterized the so-called biostructure of the living bodies and worked out a biostructural theory, which is the first supramolecular conception in biology. Nevertheless, complex biological systems are currently considered only from the molecular point of view, although they may be regarded as specific phenomena on highly structured bodies within the four-dimensional Universe. According to Macovschi, the biostructure provides organisms with life properties and controls their life processes and chemical changes. Nevertheless, plant cells or bacterial ones differ much from the animal or human cells. In fact, there are various biostructures which are related with cell properties. Hence, this theory creates confusions and cannot be easily used to explain all the properties of the biosystems. Consequently, it is our goal to highlight the principles, advantages, limitations, and applications of the biostructural theory, which might support new ideas and theories in modern life sciences.     

COMPOSITE TRAITS,SELECTION RESPONSE,AND EVOLUTION

It is very difficult to relate macroevolutionary patterns to the microevolutionary processes described by quantitative-genetic models. Quantitative-genetic parameters are statistical abstractions. Their long-term significance and evolution might be understood if they can be related to development, physiology, and other biological properties. Most continuous traits are composites of other traits that may contribute differentially to selection response and long-term divergence. The operation of selection on continuous traits can be indirect, with intermediate optima caused by correlated fitness components. Few realistic models are available, and heritable maternal effects can further complicate selection response. Examples involving allometry of brain and body size in mammals suggest that prenatal and postnatal growth have contributed differently to body-size evolution, with different correlated changes in brain size. Several different models could explain these patterns, and interpretation is further complicated by statistical difficulties in comparative biology. Quantitative-genetic models may become more informative and predictive if variation in their parameters can be explained by developmental and other biological processes that have been shaped by the previous history of the population.     

The Ethics of Fertility Preservation in Transgender Body Modifications

In some areas of clinical medicine, discussions about fertility preservation are routine, such as in the treatment of children and adolescents facing cancer treatments that will destroy their ability to produce gametes of their own. Certain professional organizations now offer guidelines for people who wish to modify their bodies and appearance in regard to sex traits, and these guidelines extend to recommendations about fertility preservation. Since the removal of testicles or ovaries will destroy the ability to have genetically related children later on, it is imperative to counsel transgender people seeking body modifications about fertility preservation options. Fertility preservation with transgender people will, however, lead to unconventional outcomes. If transgender men and women use their ova and sperm, respectively, to have children, they will function as a mother or father in a gametic sense but will function in socially reversed parental identities. There is nothing, however, about fertility preservation with transgender men and women that is objectionable in its motives, practices, or outcomes that would justify closing off these options. In any case, novel reproductive technologies may extend this kind of role reversal in principle to all people, if sperm and ova can be derived from all human beings regardless of sex, as has happened with certain laboratory animals.     

Intracellular sterol transport and distribution

Sterols are important components of many biological membranes, and changes in sterol levels can have dramatic effects on membrane properties. Sterols are transported rapidly between cellular organelles by vesicular and nonvesicular processes. Recent studies have identified transmembrane proteins that facilitate the removal of sterols from membranes as well as soluble cytoplasmic proteins that play a role in their movement through the cytoplasm. The mechanisms by which these proteins work are generally not well understood. Cells maintain large differences in the sterol:phospholipid ratio in different organelles. Recent theoretical and experimental studies indicate ways in which the lipid environment can alter the chemical potential of sterols, which may help to explain aspects of their transport kinetics and distribution.     

Eye-tracking women’s preferences for men’s somatotypes

Judging physical attractiveness involves sight, touch, sound and smells. Where visual judgments are concerned, attentional processes may have evolved to prioritize sex-typical traits that reflect cues signaling direct or indirect (i.e. genetic) benefits. Behavioral techniques that measure response times or eye movements provide a powerful test of this assumption by directly assessing how attractiveness influences the deployment of attention. We used eye-tracking to characterize women’s visual attention to men’s back-posed bodies, which varied in overall fat and muscle distribution, while they judged the potential of each model for a short- or long-term relationship. We hypothesized that when judging male bodily attractiveness women would focus more on the upper body musculature of all somatotypes, as it is a signal of metabolic health, immunocompetence and underlying endocrine function. Results showed that mesomorphs (muscular men) received the highest attractiveness ratings, followed by ectomorphs (lean men) and endomorphs (heavily-set men). For eye movements, attention was evenly distributed to the upper and lower back of both ectomorphs and mesomorphs. In contrast, for endomorphs the lower back, including the waist, captured more attention over the viewing period. These patterns in visual attention were evident in the first second of viewing, suggesting that body composition is identified early in viewing and guides attention to body regions that provide salient biological information during judgments of men’s bodily attractiveness.     

Telomeric DNA Mediates De Novo PML Body Formation

The cell nucleus harbors a variety of different bodies that vary in number, composition, and size. Although these bodies coordinate important nuclear processes, little is known about how they are formed. Among the most intensively studied bodies in recent years is the PML body. These bodies have been implicated in gene regulation and other cellular processes and are disrupted in cells from patients suffering from acute promyelocytic leukemia. Using live cell imaging microscopy and immunofluorescence, we show in several cell types that PML bodies are formed at telomeric DNA during interphase. Recent studies revealed that both SUMO modification sites and SUMO interaction motifs in the promyelocytic leukemia (PML) protein are required for PML body formation. We show that SMC5, a component of the SUMO ligase MMS21-containing SMC5/6 complex, localizes temporarily at telomeric DNA during PML body formation, suggesting a possible role for SUMO in the formation of PML bodies at telomeric DNA. Our data identify a novel role of telomeric DNA during PML body formation.     

Hypotheses and humility: Ideas do not have to be right to be useful

Hypotheses need not be completely right to be useful. A hypothesis that explains an important aspect of the world, but not all of the world, can stimulate new ideas and new experiments which take science forward. Phlogiston is a typical case study. While not universally accepted at the time, and subsequently proved to be wrong, the hypothesis that there was a ‘fire-giving’ substance in inflammable materials prompted the development of quantitative chemistry, and the subsequent discovery of oxygen. Hypotheses today do not have to explain all aspects of the world perfectly. But they should be honest about those aspects they do not explain, and demonstrate some humility in their limitations. It is very unlikely that a single idea explains everything in a biological system. Theorists should recognise this: if they do not, their readers will, and will discount their ideas because of their lack of awareness of their context. Humility may get you a hearing.     

Surface analysis of membrane dynamics

Cellular membranes change shape and composition in a controlled way in order for life to prosper. They are set apart from other cellular structures by their two-dimensional nature, which governs their properties and the processes happening in or on them. During the last decade, a boom of new techniques has allowed the study of the surface of biological membranes in unprecedented ways and has greatly advanced our understanding of its molecular organization. In this review, we first describe the principles of state-of-the-art microscopy methods and the suitable model membranes for the study of dynamic processes. Then, we explain how they can be used to investigate lipid dynamics, the lateral organization of membrane domains and the dynamic structure of cellular membranes.     

Horizontal transfer of microRNAs: molecular mechanisms and clinical applications

A new class of RNA regulatory genes known as microRNAs (miRNAs) has been found to introduce a whole new layer of gene regulation in eukaryotes. The intensive studies of the past several years have demonstrated that miRNAs are not only found intracellularly, but are also detectable outside cells, including in various body fluids (e.g. serum, plasma, saliva, urine and milk). This phenomenon raises questions about the biological function of such extracellular miRNAs. Substantial amounts of extracellular miRNAs are enclosed in small membranous vesicles (e.g. exosomes, shedding vesicles and apoptotic bodies) or packaged with RNA-binding proteins (e.g. high-density lipoprotein, Argonaute 2 and nucleophosmin 1). These miRNAs may function as secreted signaling molecules to influence the recipient cell phenotypes. Furthermore, secreted extracellular miRNAs may reflect molecular changes in the cells from which they are derived and can therefore potentially serve as diagnostic indicators of disease. Several studies also point to the potential application of siRNA/miRNA delivery as a new therapeutic strategy for treating diseases. In this review, we summarize what is known about the mechanism of miRNA secretion. In addition, we describe the pathophysiological roles of secreted miRNAs and their clinical potential as diagnostic biomarkers and therapeutic drugs. We believe that miRNA transfer between cells will have a significant impact on biological research in the coming years.     

REGULATION OF MICROTUBULES IN TETRAHYMENA : I. Electron Microscopy of Oral Replacement

The coupled resorption and redifferentiation of oral structures which occurs in Tetrahymena pyriformis under conditions of amino acid deprivation has been studied by transmission electron microscopy. Two patterns of ciliary resorption have been found, (a) in situ, and (b) after withdrawal into the cytoplasm. No autophagic vacuoles containing cilia or ciliary axonemes have been seen. Stomatogenic field basal bodies arise by a process of rapid sequential nucleation, with new ones always appearing next to more mature ones, even though the latter may not be fully differentiated. Accessory radial ribbons of microtubules develop immediately adjacent to oral field basal bodies as a late step in their maturation. It can be seen that the formation of basal bodies and their orientation within the oral complex are separate processes. This is true for about 130 of the approximately 170 oral basal bodies; the remaining 40 or so form within the patterned groups of ciliary units as a later event. Clusters of randomly oriented thin-walled microtubules are found surrounding oral basal bodies at all times during stomatogenesis. They may either represent stores of microtubule subunit protein, or serve as effectors of basal body movement during their orientation into pattern.     

ON THE INDEPENDENCE OF SYSTEMATICS

Abstract— Before the publication of On the Origin of Species the standing patterns of natural history—common plan, homology, ontogenetic parallelism, and the hierarchy of groups — were taken as indications of a biological order that had not yet been understood. Darwin covered all of these in chapter 13 of the Origin , arguing that his theory was the first to provide a reasonable explanation for the existence of such patterns. Since Darwin took these relations to be established by previous biology, and used them as evidence for the explanatory power of his theory, he was clearly of the opinion that they were independent of that theory. Although several modern figures have argued to the contrary, it seems that Darwin was right. The patterns listed above are recoverable from observation without reference to evolutionary theory, which theory may then be applied to provide an account of the processes by which they may have come about. That aspect of systematics concerned with the identification of the empirical patterns evidently constitutes a study prior to and independent of theories of process.     

A subpopulation of mushroom body intrinsic neurons is generated by protocerebral neuroblasts in the tobacco hornworm moth, Manduca sexta (Sphingidae, Lepidoptera)

Subpopulations of Kenyon cells, the intrinsic neurons of the insect mushroom bodies, are typically sequentially generated by dedicated neuroblasts that begin proliferating during embryogenesis. When present, Class III Kenyon cells are thought to be the first born population of neurons by virtue of the location of their cell somata, farthest from the position of the mushroom body neuroblasts. In the adult tobacco hornworm moth Manduca sexta, the axons of Class III Kenyon cells form a separate Y tract and dorsal and ventral lobelet; surprisingly, these distinctive structures are absent from the larval Manduca mushroom bodies. BrdU labeling and immunohistochemical staining reveal that Class III Kenyon cells are in fact born in the mid-larval through adult stages. The peripheral position of their cell bodies is due to their genesis from two previously undescribed protocerebral neuroblasts distinct from the mushroom body neuroblasts that generate the other Kenyon cell types. These findings challenge the notion that all Kenyon cells are produced solely by the mushroom body neuroblasts, and may explain why Class III Kenyon cells are found sporadically across the insects, suggesting that when present, they may arise through de novo recruitment of neuroblasts outside of the mushroom bodies. In addition, lifelong neurogenesis by both the Class III neuroblasts and the mushroom body neuroblasts was observed, raising the possibility that adult neurogenesis may play a role in mushroom body function in Manduca.     

Looking to the Future of Ecosystem Services

Ecosystem services—the benefits that people obtain from ecosystems—are essential to human existence, but demands for services often surpass the capacity of ecosystems to provide them. Lack of ecological information often precludes informed decision making about ecosystem services. The Millennium Ecosystem Assessment (MA) was conceived in part to provide the necessary ecological information to decision makers. To this end, the MA set out to address the stated needs and concerns of decision makers and examine the ecological dynamics and uncertainties underlying these concerns. To improve our understanding of their information needs and concerns, we interviewed 59 decision makers from five continents. The respondents indicated that although most people generally agree about the ideal state of the planet—free of poverty and extreme inequality, replete with cultural and biological diversity—they often disagree about the best way to achieve these goals. Further, although nonspecialists are generally concerned about the environment and may have a good understanding of some of issues, they often have a more limited grasp of the ecological dynamics that drive the issues of concern. We identify some of the principal uncertainties about ecosystem dynamics and feedbacks that underlie the concerns of decision makers. Each of the papers in this special feature addresses these ecological feedbacks from the perspective of a specific discipline, suggesting ways in which knowledge of ecological dynamics can be incorporated into the MA’s assessment and scenario-building process.     

Does wing reduction influence the relationship between altitude and insect body size? A case study using New Zealand's diverse stonefly fauna

Researchers have long been intrigued by evolutionary processes that explain biological diversity. Numerous studies have reported strong associations between animal body size and altitude, but insect analyses have often yielded equivocal results. Here, we analyze a collection database of New Zealand's diverse endemic stonefly fauna (106 species across 21 genera) to test for relationships between altitude and plecopteran body size. This insect assemblage includes a variety of wing‐reduced (26 spp) and fully winged (80 spp) taxa and covers a broad range of altitudes (0–2,000 m). We detected significant relationships between altitude and body size for wing‐reduced, but not fully winged, stonefly taxa. These results suggest that, while the maintenance of flight apparatus might place a constraint on body size in some fully winged species, the loss of flight may free insects from this evolutionary constraint. We suggest that rapid switches in insect dispersal ability may facilitate rapid evolutionary shifts across a number of biological attributes and may explain the inconsistent results from previous macroecological analyses of insect assemblages.