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PubMedDate not supplied

[Tumors of the soft parts of the extremities. Anatomoclinical and therapeutic aspects].

A total of 60 cases are presented, of patients with tumours of the soft parts of the limbs, from a total of 14,000 surgical interventions. Of the total 18 were malignant tumours, while the remaining 42 cases had benign tumours. Tumours of the soft parts of the limbs include a large variety of histologic forms, and this raises particular problems of diagnosis and treatment. In the case of benign tumours the treatment is better codified, and consists in the removal of the tumour by simple enucleation. Recidives are possible because of the infra-clinical peritumoral invasion. In the case of malignant tumors the treatment is more differentiated, depending on the histologic type, the degree of malignancy, the stage of evolution, and on evolutive characteristics. Surgery remains an essential part of the treatment, and either limited or radical surgical solutions (amputation) are used. Frequently radiation and chemical therapy are associated, with good results. Six clinical observations are presented: rhabdomyosarcoma of the recidivating type, multi-recidivating fibrosarcoma, fibromyxosarcoma, varicose ulcers with malignant evolution, and two cases of liposarcoma. The cooperation is stressed, which should exist between the surgeon, the pathologist, radiologist and oncologist, for the diagnosis and treatment of these affections.

Adult↗
PubMed2004

Insulin and its receptor: structure, function and evolution.

I present here a personal perspective on more than three decades of research into the structural biology of the insulin-receptor interaction. The solution of the three-dimensional structure of insulin in 1969 provided a detailed understanding of the insulin surfaces involved in self-assembly. In subsequent years, hundreds of insulin analogues were prepared by insulin chemists and molecular biologists, with the goal of relating the structure to the biological function of the molecule. The design of methods for direct receptor-binding studies in the 1970s, and the cloning of the receptor in the mid 1980s, provided the required tools for detailed structure-function studies. In the absence of a full three-dimensional structure of the insulin-receptor complex, I attempt to assemble the existing pieces of the puzzle generated by our and other laboratories, in order to generate a plausible mechanistic model of the insulin-receptor interaction that explains its kinetics and negative cooperativity.

Animals↗
PubMed2005

Genetics and adaptation in structured populations: sex ratio evolution in Silene vulgaris.

Theoretical models suggest that population structure can interact with frequency dependent selection to affect fitness in such a way that adaptation is dependent not only on the genotype of an individual and the genotypes with which it co-occurs within populations (demes), but also the distribution of genotypes among populations. A canonical example is the evolution of altruistic behavior, where the costs and benefits of cooperation depend on the local frequency of other altruists, and can vary from one population to another. Here we review research on sex ratio evolution that we have conducted over the past several years on the gynodioecious herb Silene vulgaris in which we combine studies of negative frequency dependent fitness on female phenotypes with studies of the population structure of cytoplasmic genes affecting sex expression. This is presented as a contrast to a hypothetical example of selection on similar genotypes and phenotypes, but in the absence of population structure. Sex ratio evolution in Silene vulgaris provides one of the clearest examples of how selection occurs at multiple levels and how population structure, per se, can influence adaptive evolution.

Adaptation, Biological↗
PubMed1996

Models of parasite virulence.

Several evolutionary processes influence virulence, the amount of damage a parasite causes to its host. For example, parasites are favored to exploit their hosts prudently to prolong infection and avoid killing the host. Parasites also need to use some host resources to reproduce and transmit infections to new hosts. Thus parasites face a tradeoff between prudent exploitation and rapid reproduction-a life history tradeoff between longevity and fecundity. Other tradeoffs among components of parasite fitness also influence virulence. For example, competition among parasite genotypes favors rapid growth to achieve greater relative success within the host. Rapid growth may, however, lower the total productivity of the local group by overexploiting the host, which is a potentially renewable food supply. This is a problem of kin selection and group selection. I summarize models of parasite virulence with the theoretical tools of life history analysis, kin selection, and epidemiology. I then apply the theory to recent empirical studies and models of virulence. These applications, to nematodes, to the extreme virulence of hospital epidemics, and to bacterial meningitis, show the power of simple life history theory to highlight interesting questions and to provide a rich array of hypotheses. These examples also show the kinds of conceptual mistakes that commonly arise when only a few components of parasite fitness are analysed in isolation. The last part of the article connects standard models of parasite virulence to diverse topics, such as the virulence of bacterial plasmids, the evolution of genomes, and the processes that influenced conflict and cooperation among the earliest replicators near the origin of life.

Animals↗
PubMed2005

Effects of information and group structure on evolution of altruism: analysis of two-score model by covariance and contextual analyses.

An altruistic individual has to gamble on cooperation to a stranger because it does not know whether the stranger is trustworthy before direct interaction. Nowak and Sigmund (Nature 393 (1998a) 573; J. Theor. Biol. 194 (1998b) 561) presented a new theoretical framework of indirect reciprocal altruism by image scoring game where all individuals are informed about a partner's behavior from its image score without direct interaction. Interestingly, in a simplified version of the image scoring game, the evolutionarily stability condition for altruism became a similar form of Hamilton's rule, i.e. inequality that the probability of getting correct information is more than the ratio of cost to benefit. Since the Hamilton's rule was derived by evolutionarily stable analysis, the evolutionary meaning of the probability of getting correct information has not been clearly examined in terms of kin and group selection. In this study, we applied covariance analysis to the two-score model for deriving the Hamilton's rule. We confirmed that the probability of getting correct information was proportional to the bias of altruistic interactions caused by using information about a partner's image score. The Hamilton's rule was dependent on the number of game bouts even though the information reduced the risk of cooperation to selfish one at the first encounter. In addition, we incorporated group structure to the two-score model to examine whether the probability of getting correct information affect selection for altruism by group selection. We calculated a Hamilton's rule of group selection by contextual analysis. Group selection is very effective when either the probability of getting correct information or that of future interaction, or both are low. The two Hamilton's rules derived by covariance and contextual analyses demonstrated the effects of information and group structure on the evolution of altruism. We inferred that information about a partner's behavior and group structure can produce flexible pathways for the evolution of altruism.

Altruism↗
PubMedDate not supplied

Variable subunit contact and cooperativity of hemoglobins.

Tertiary structures of proteins are conserved better than their primary structures during evolution. Quaternary structures or subunit organizations, however, are not always conserved. A typical case is found in hemoglobin family. Although human, Scapharca, and Urechis have tetrameric hemoglobins, their subunit contacts are completely different from each other. We report here that only one or two amino acid replacements are enough to create a new contact between subunits. Such a small number of chance replacements is expected during the evolution of hemoglobins. This result explains why different modes of subunit interaction evolved in animal hemoglobins. In contrast, certain interactions between subunits are necessary for cooperative oxygen binding. Cooperative oxygen binding is observed often in dimeric and tetrameric hemoglobins. Conformational change of a subunit induced by the first oxygen binding to the heme group is transmitted through the subunit contacts and increases the affinity of the second oxygen. The tetrameric hemoglobins from humans and Scapharca have cooperativity in spite of their different modes of subunit contact, but the one from Urechis does not. The relationship between cooperativity and the mode of subunit contacts is not clear. We compared the atomic interactions at the subunit contact surface of cooperative and non-cooperative tetrameric hemoglobins. We show that heme-contact modules M3-M6 play a key role in the subunit contacts responsible for cooperativity. A module was defined as a contiguous peptide segment having compact conformation and its average length is about 15 amino acid residues. We show that the cooperative hemoglobins have interactins involving at least two pairs of modules among the four heme-contact modules at subunit contact.

Animals↗
PubMed2004

Mating system and population structure of the primitively eusocial wasp Ropalidia revolutionalis: a model system for the evolution of complex societies.

Mating systems are important determinants of genetic structure in cooperative groups, and their effects can influence profoundly the interactions of group members. The primitively eusocial wasp, Ropalidia revolutionalis, has an interesting genetic and social structure that makes it an excellent model system for examining the evolution of more complex societies. In particular, its colonies sometimes have multiple queens, a key characteristic of more advanced wasp societies. In this study, we have characterized the mating system of the social wasp Ropalidia revolutionalis to understand better its colony genetic structure. R. revolutionalis females nearly always mate singly and they are unrelated to their mates. However, different females in the same colony do mate with males, on average, who are related as cousins. Single mating will help to maintain high relatedness, which should be important for continued cooperation in multiple queen societies, but it creates potential conflicts in single queen colonies over the production of males as well as over the timing of male production. We have also characterized the population structure of R. revolutionalis from Townsville, in tropical north Queensland, to Brisbane in the subtropics. Even at such a large scale, the population is remarkably unstructured with an average F(ST) of 0.0546. There is weak isolation by distance, and evidence for subtle differentiation between a southern region with no dry season, which extends as far north as Rockhampton, and a northern region with a severe to moderate dry season. This may reflect historical effects of extreme aridity on the population structure.

Analysis of Variance↗
PubMed2002

Recurrence quantification analysis reveals interaction partners in paramyxoviridae envelope glycoproteins.

The paramyxovirus envelope fuses with the host cell membrane by cooperative interaction of two transmembrane glycoproteins: the hemagglutinin neuraminidase (HN) and the fusion (F) glycoprotein. The interaction appears to be finely regulated, as both proteins must derive from the same viral species to obtain a functional interaction. Because HN and F do not form stable complexes, this interaction is poorly characterized. This article demonstrates that a modification of a classical bioinformatic method based on the co-evolution of interacting partners can detect the specificity of the HN and F interaction. The proposed approach relies on a relatively new nonlinear signal analysis technique, recurrence quantification analysis (RQA), applied to the hydrophobicity sequences of viral proteins. This technique is able to shed light on the interaction between HN and F proteins in the virus-cell fusion and, more generally, permits the quantitative comparison of nonhomologue protein systems. On the contrary, the same co-evolution approach, based on the classical sequence alignment procedure, was unable to discriminate interacting partners from the general strict correlation existing between the evolution of viral proteins as a whole. The cooperation between HN and F in the fusion process is thus demonstrated by a bioinformatic, purely sequence-dependent, perspective.

Computational Biology↗
PubMed2004

Pleiotropy as a mechanism to stabilize cooperation.

Most genes affect many traits. This phenomenon, known as pleiotropy, is a major constraint on evolution because adaptive change in one trait may be prevented because it would compromise other traits affected by the same genes. Here we show that pleiotropy can have an unexpected effect and benefit one of the most enigmatic of adaptations--cooperation. A spectacular act of cooperation occurs in the social amoeba Dictyostelium discoideum, in which some cells die to form a stalk that holds the other cells aloft as reproductive spores. We have identified a gene, dimA, in D. discoideum that has two contrasting effects. It is required to receive the signalling molecule DIF-1 that causes differentiation into prestalk cells. Ignoring DIF-1 and not becoming prestalk should allow cells to cheat by avoiding the stalk. However, we find that in aggregations containing the wild-type cells, lack of the dimA gene results in exclusion from spores. This pleiotropic linkage of stalk and spore formation limits the potential for cheating in D. discoideum because defecting on prestalk cell production results in an even greater reduction in spores. We propose that the evolution of pleiotropic links between cheating and personal costs can stabilize cooperative adaptations.

Animals↗
PubMed2000

Food chemical discriminations by an herbivorous lizard, Corucia zebrata.

Adjustment of chemosensory response to diet should be apparent in evolutionary changes corresponding to dietary shifts. Because most lizards are generalist predators of small animals, relationships between chemosensory behavior and diet are difficult to detect. Nevertheless, the evolution of herbivory by a small number of lizards provides an opportunity to detect any corresponding change in response to plant chemicals. I studied tongue-flicking and biting by the large, herbivorous scincid lizard Corucia zebrata in response to chemical cues from crickets, romaine lettuce, and control stimuli presented on cotton swabs. The skinks exhibited significantly stronger response to plant and animal chemicals than to controls for several variables: greater number of individuals that bit swabs, shorter latency to bite, greater rate of tongue-flicks, and greater tongue-flick attack score. The clearest differences were observed for tongue-flick attack score, a composite variable that combines the effects of tongue-flicking and biting. An insectivorous member of the same subfamily, Scincella lateralis, shows strong tongue-flicking and biting response to chemical prey cues, but not to plant chemicals. This suggests that response to plant chemicals by C. zebrata may have evolved in tandem with the incorporation of plants into the diet and that response to cricket chemicals has been retained, perhaps due to similarities between plant and animal food. The findings support the hypothesis that dietary shifts induce corresponding changes in chemosensory response, but provide only a single independent contrast for a study of correlated evolution between plant diet and chemosensory response to plants. J. Exp. Zool. 286:372-378, 2000.

Adaptation, Physiological↗
PubMed1989

[Recessive oncogene and loss of heterozygosity].

Recessive oncogene, which has been originally proposed for the retinoblastoma susceptibility gene, is linked to the development of cancer by missing its gene function followed by the loss of normal allele (often observed as a loss of heterozygosity of neighbouring heteromorphic loci). Recent studies on the loss of heterozygosity in cancers indicate that mutations of such genes are relatively common in human cancers, and play a significant role in the dedifferentiation, progression and evolution of cancers as well as the initiative role. Such initiative and cooperative role of recessive oncogene opened a new field relating to the research on the genetic origin of cancer, evolutional implications of cancer development, and molecular diagnosis for cancer prognosis.

Chromosome Deletion↗
PubMed1994

Kin selection and virulence in the evolution of protocells and parasites.

The evolution of parasite virulence and the origin of cooperative genomes in primitive cells are both problems that balance cooperative and competitive interactions among symbionts. I analyse the trade-off among three correlated traits: competitiveness against other genotypes for resources within hosts (protocells), damage to the host (virulence), and rate of horizontal transmission from one host to another. All three life-history components are strongly influenced by kin selection. For example, when genetic relatedness within hosts is high, each genotype is competing for resources with closely related genotypes. This competition among relatives favours increased horizontal transmission to colonize new hosts and compete against non-relatives. My analysis shows that many aspects of parasite and protocell evolution must be studied with the theoretical tools of social evolution. I discuss extensions that are required for a general theory of symbiosis.

Animals↗
PubMed2001

The evolution of social behavior in microorganisms.

Recent studies of microorganisms have revealed diverse complex social behaviors, including cooperation in foraging, building, reproducing, dispersing and communicating. These microorganisms should provide novel, tractable systems for the analysis of social evolution. The application of evolutionary and ecological theory to understanding their behavior will aid in developing better means to control the many pathogenic bacteria that use social interactions to affect humans.

Journal Article↗