Chimera,spandrel, or adaptation

In every known human society, some kind—usually many kinds—of art is practiced, frequently with much vigor and pleasure, so that one could at least hypothesize that “artifying” or “artification” is a characteristic behavior of our species. Yet human ethologists and sociobiologists have been conspicuously unforthcoming about this observably widespread and valued practice, for a number of stated and unstated reasons. The present essay is a position paper that offers an overview and analysis of conceptual issues and problems inherent in viewing art and/or aesthetics as adaptive, and it presents a speculative account of a human behavior of art. Ellen Dissanayake is an independent scholar who has straddled the abyss between biology and art for more than twenty years. She is currently a Visiting Fellow at the Institute for Advanced Studies in the Humanities, University of Edinburgh.     

Adaptation, redundancy or resilience

Diversity creates resilience both in ecosystems and living organism. Yet, although genetic diversity protects organisms from many diseases and disorders, it also makes it much harder for geneticist to identify the risk factors that lead to common diseases.The study of the natural environment teaches us that ecological systems rich in biodiversity have greater resilience than less diverse systems, and that resource-poor ecosystems tend to have greater biodiversity to buffer against environmental change. The African savannah, a huge ecosystem, contains an abundance of grasses and other plants, herbivores and their predators. The loss of one species might be compensated for by the presence of others, but if species are relentlessly removed, one after another, the continuing loss will weaken the system until it changes its steady state and eventually collapses.To use another illustrative example of the protection conferred by diversity: modern agriculture uses only six cereal crops as the main basic staples of the human diet. If even one crop were threatened—perhaps by a plant virus or other pathogen—the consequences for humanity would probably be catastrophic. To avoid such a scenario, breeders have created hundreds of cultivars, each with minor phenotypic changes that confer resistance to a biotic or abiotic stressor. Thus, humans too create resilience by increasing biodiversity.In order to improve our understanding of complex diseases, we can extend this notion of diverse ecosystems to organisms. Similarly to the disappearance of one species in an ecosystem with abundant biodiversity, the loss of one gene function might not be immediately apparent, because many such changes can be compensated for, at least partly, by changes in other genes. However, a series of small, cumulative changes in many genes could lead to the breakdown of the phenotype of the organism, rendering it less resilient and more susceptible to disease, especially when it is under environmental or infectious stress. It is like throwing a stone in a pond, which generates small waves; throwing many stones at once causes a more complex disturbance, whereby waves combine to create bigger waves or attenuate each other by interference. Thus, even inherited disorders such as hypertrophic cardiomyopathy show several phenotypes as other genes modify the action of the affected gene.Geneticists have found many genes or whole genomic regions that have multiplied throughout the genome by duplication (Eisenstein, 2010). The repeated sequences might be identical, nearly identical or related, and they can be functional or non-functional, as is the case with pseudogenes. In terms of diversity, repeats have apparently given rise to multigene families, such as the collagens, which encode several structural proteins. Even microorganisms, such as Mycobacterium tuberculosis, have extended gene families or several insertions.It was assumed previously that pseudogenes are unnecessary gene copies and therefore inactivated. Yet, there is increasing evidence that they perform a regulatory role, by influencing the function of the parent gene. The variation in copy number also seems to be as, or even more, important than the number of polymorphisms, particularly in complex diseases or phenotypic traits. One negative example is the gene that codes for glutathione transferase, GSTM1. Roughly half of the population carries a deletion of GSTM1, which reduces their ability to neutralize isothiocyanates. Clearly then, many individuals will have two null alleles and an increased risk of xenobiotic-induced disease. Another fascinating example is that preference for a high-starch diet is associated with multiple copies of the salivary amylase gene, which increases production of this enzyme.Humans show a range of vulnerabilities to complex or infectious diseases, such as pulmonary tuberculosis. Despite an exhaustive search, no obvious, major resistance or susceptibility genes for tuberculosis have been found, although many genes—each with minor effects—have a role in disease susceptibility. Further support for the argument that resilience comes from diversity is found in the confusion around genetic association studies in many complex diseases, in which a given gene might be significantly associated with a condition in one population, but not in others. I suspect that many of these reports can be explained by the fact that susceptibility is caused by cumulative functional changes in many genes along different routes in different groups of humans or animals. In fact, susceptibility to a common disease conferred by a single, major locus would make the organism extremely vulnerable—which is exactly what we see with autosomal-dominant inherited diseases. Thus, it is unlikely that complex diseases are caused by a solitary gene defect, as evolution would select against the high risk of a single dominant effect. Instead, we see a range of conditions and phenotypes, owing to the large number of genes involved.This diversity of genetic factors is a blessing for humanity, as it has equipped us with enormous resilience against many common diseases, from cancer to coronary heart disease, to infectious diseases. But, it is also a bane for the geneticist and the clinical scientists who search for genetic factors that can be used to predict disease susceptibility, or the condition or progress of disease. Complexity and diversity make things far more unpredictable and messy—and therefore more difficult for scientific analysis—but both also ensure our survival against a daily assault of biotic and abiotic stressors.     

Flatfishes, Turtles, and Bolyerine Snakes: Evolution by Small Steps or Large, or Both?

Step size in evolution is rapidly becoming a major subject of interest to biologists. Traditionally, small changes alone were seen as significant in evolution, and any large differences between an ancestor and its descendant could be explained entirely by the accumulation of many small steps. Whether the evolution of major adaptations is mainly a matter of amassing such small increments of change, or if a significant proportion occurs through the inclusion of one or more large steps, is vital to the understanding of how evolution works. This paper begins by examining four “classic” examples of animals—flatfishes, turtles, bolyerine snakes, and gastropod molluscs—each of which has seemed difficult to interpret as resulting from a continuous series of tiny increments. Recently, however, arguments have appeared to contradict those views, and to propose instead that each of these animal groups arose through continuous adaptive modifications. While some of these arguments are more plausible than others, the view of the present author is that in none of them is there convincing evidence to conclude that the groups arose solely through gradual changes. More specifically, there is no basis to reject an evolutionary origin of the major traits in each group that included at least one principal inovation, occurring in a large, discontinuous step, preceded and followed by relatively small, more gradual changes. The broader question of how discontinuous evolution may occur is addressed through several means. These include considerations of epigenetic (sensu Waddington) development, comparative embryology, population genetics, and other approaches. Overall the phenomenon of adaptive accommodation is seen as of major importance, and its implications for ameliorating possible deleterious attributes of novel phenotypes are discussed. In the course of these analyses the doctrine that all adaptive evolution is driven by external environmental change is reviewed. It is suggested that while small adaptive changes are often closely related to shifts in specific environmental facets, the modifications associated with more major adaptations may be less so.     

Detection of depolymerase isoenzymes after electrophoresis or electrofocusing, or in titration curves

The cup-plate technique makes it possible to detect enzyme activities after diffusion into buffered, substrate-containing agar gels. This technique has been used after nondenaturing blotting transfer in order to detect depolymerizing enzyme activities once analytical protein separation (e.g., by electrophoresis, electrofocusing, or titration curves) has been completed. This rapid and very sensitive method was successfully applied to the enzymes polygalacturonate lyase, polygalacturonate hydrolase, endoglucanase, and xylan hydrolase. Other possible applications are presented.     

Growth and ion uptake by wheat supplied nitrogen as nitrate,or ammonium,or both

Summary The effects of concentration and source (NH₄, NO₃, and NO₃ plus NH₄) of added N on the rate of growth, final yield, and content and rate of intake of N, P, K, Ca, Mg and S by wheat seedlings were evaluated. Rate of growth in dilute liquid cultures differed among the N sources giving yields relative to those of the all-NO₃ system of 92 per cent for the all-NH₄ system, and of 154 per cent for the NO₃ plus NH₄ system. At low rates of NH₄ intake in the all-NH₄ systems growth rates were equal to or slightly better than those of plants supplied equivalent concentrations of NO₃. Rates of NH₄ intake exceeding 100 mole g^–1 h^–1 resulted in reduced growth rates and incipient NH₄ toxicity. Yields at 95 per cent of maximum resulted with steady-state N concentrations of 80 M in all NO₃ systems, 30 M NH₄ in all-NH₄ systems, and in combined source systems when 200M NO₃ plus 30 M NH₄ were supplied. The rate of N intake and plant protein content, were maximal when both NO₃ and NH₄ were supplied. Increasing rates of NO₃ intake were associated with increases in the rates of Ca, Mg, and K intake; but with increasing rates of NH₄ absorption, intake of Ca and Mg decreased. The yield and growth rate enhancement observed from the addition of low concentrations of NH₄ to cultures supplying adequate NO₃ is suggested to result from the reduced energy requirement for utilization of NH₄, as compared to NO₃ in protein synthesis and from the increased photosynthetic capacity of the higher-protein NH₄-fed plants. In the all-NH₄ systems the maximum attainable growth rate was limited by NH₄ toxicity; whereas in the all-NO₃ systems the rate of NO₃ reduction was limiting.Contribution from the Department of Soils and Plant Nutrition, University of California, Davis, California 95616.     

Repairs in the lower abdomen, groin, or perineum with myocutaneous or omental flaps.

Our experiences with omental and myocutaneous flaps for the closure of the lower abdomen, groin, and perineum are outlined. The relative advantages and disadvantages of the various flaps are discussed.     

Development of tolerance to pethidine in rats, pretreated or not, with beta-naphtoflavone or SKF 525 A

Tolerance to the analgesic effect of pethidine (PD) in rats, treated with a dose of 15 mg/kg of the compound twice daily at 12 h intervals for 1-3 weeks, was assessed using both, heat and current irritating stimuli. Tolerance could be detected earlier by the current irritating method, than by the hot plate technique. Pretreatment with beta-naphtoflavone did only slightly affect the development of tolerance to the antinociceptive effect of PD. In contrast after one week of treatment with SKF 525 A PD retained its analgesic effect. The prolonged pretreatment with SKF 525 A did not prevent the development of tolerance to the analgesic effect of PD.