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PubMed2002

The stability of cooperation involving variable investment.

In this paper, we attempt to reconcile the results of several studies which have investigated the evolution of cooperation between non-relatives in systems where investment in partners can vary. In contrast to previous proposals, we show for the first time that variable-investment cooperation can be readily maintained in inter-species mutualistic relationships even in the absence of spatial structure, but that the stability of this interaction is dependent on the particular investment-response rule that is employed. By allowing the evolution of investment-response parameters in both inter- and intra-specific versions of the continuous variable-investment Prisoners' Dilemma we show that, in the absence of further factors, the raise-the stakes (RTS) strategy is likely to evolve into a simpler, variable investment form of Give-as-Good-as-you-Get that initially offers a high fixed amount and subsequently matches its partner's investment. Nevertheless, we demonstrate that genuine RTS-like strategies will still be selected if two intuitively reasonable conditions hold: if individuals are limited in terms of the total they can invest in cooperative actions over their lifetimes, and if there are always some individuals in a population that cannot cooperate.

Animals↗

PubMed2004

Cell wall metabolism during maturation, ripening and senescence of peach fruit.

Cell wall changes were examined in fruit of a melting flesh peach (Prunus persica L.) allowed to ripen on the tree. Three phases to softening were noted, the first of which began prior to the completion of flesh colour change and an increase in ethylene evolution. Softening in young mature fruit, prior to ripening, was associated with a depolymerization of matrix glycans both loosely and tightly attached to cellulose and a loss of Gal from all cell wall fractions. After the initiation of ripening, but before the melting stage, softening was associated with continuing, progressive depolymerization of matrix glycans. A massive loss of Ara from the loosely bound matrix glycan fraction was observed, probably from side chains of glucuronoarabinoxylan, pectin, or possibly arabinogalactan protein firmly bound into the wall and solubilized in this extract. An increase in the solubilization of polyuronides also occurred during this period, when softening was already well advanced. The extensive softening of the melting period was marked by substantial depolymerization of both loosely and tightly bound matrix glycans, including a loss of Ara from the latter, an increase in matrix glycan extractability, and a dramatic depolymerization of chelator-soluble polyuronides which continued during senescence. Depolymerization of chelator-soluble polyuronides thus occurred substantially after the increase in their solubilization. Ripening-related increases were observed in the activities of exo- and endo-polygalacturonase (EC 3.2.1.67; EC 3.2.1.15), pectin methylesterase (EC 3.1.1.11), endo-1,4-beta-glucanase (EC 3.2.1.4), endo-1,4-beta-mannanase (EC 3.2.1.78), alpha-arabinosidase (EC 3.2.1.55), and beta-galactosidase (EC 3.2.1.23), but the timing and extent of the increases differed between enzymes and was not necessarily related to ethylene evolution. Fruit softening in peach is a continuous process and correlated closely with the depolymerization of matrix glycans, which proceeded throughout development. However, numerous other cell wall changes also took place, such as the deglycosylation of particular polymers and the solubilization and depolymerization of chelator-soluble polyuronides, but these were transient and occurred only at specific phases of the softening process. Fruit softening and other textural changes in peach appear to have a number of stages, each involving a different set of cell wall modifications.

Aging↗

PubMed1990

Evolution of the P450 gene superfamily: animal-plant 'warfare', molecular drive and human genetic differences in drug oxidation.

Drug-metabolizing enzymes, such as those encoded by the cytochrome P450 genes, are noted for their high degree of interspecies and intraspecies variability. We believe that much of this diversity is the result of continuous molecularly driven coevolution of plants producing phytoalexins and animals responding with new enzymes to detoxify these chemicals. One consequence of human P450 gene evolution is polymorphism in drug metabolism, leading to marked differences in the response of individuals to the toxic and carcinogenic effects of drugs and other environmental chemicals.

Animals↗

PubMed2000

ACTH-producing pituitary cancer: experience at the King Faisal Specialist Hospital & Research Centre.

Pituitary gland is an uncommon site of a primary cancer. Of more than 600 cases of pituitary tumors seen at the KFSH&RC between 1975 to 1998 only 3 patients had primary pituitary cancer. We have previously reported a case of pituitary fibrosarcoma arising as a rare complication of external radiotherapy (ERT) for GH-secreting pituitary adenoma (PA) [1]. We report now 2 cases of ACTH-producing primary pituitary carcinoma (ACTH-PPC); their follow-up data provide information on the natural history of this cancer. Patient #1; a 46 year old lady with Cushing's disease (CD) presented with an enlarged right cervical lymph node (LN) 2 years after having undergone a partial hypophysectomy through transsphenoidal surgery (PHYPX/TSS) and ERT for an invasive pituitary tumor. Patient #2; a 26 year old man presented with CD and underwent bilateral adrenalectomy (ADx) and pituitary ERT. Thirty-nine months later he developed Nelson's syndrome and a PHYPX/TSS was performed. Incidentally discovered hepatic metastases in this patient and an excisional biopsy of the LN in patient #1 showed histological features very similar to the pituitary tumor, and they stained strongly positive for ACTH. Perinuclear spherical hyalinized cytoplasmic inclusions were seen in the LN biopsy that corresponded to bundles of type 1 microfilaments (specific for pituitary ACTH-producing cells) seen by electron microscopy. A whole body 18-Fluoro-2-Deoxy-D-Glucose positron emission (FDG-PET) scanning, showed an intense uptake in the neck mass. A trial of octreotide did not change the exceedingly high levels of ACTH in patient #2, further supporting the diagnosis of ACTH-PPC. The clinical course of 102 months prior to his demise showed continued progression of the primary and the metastatic tumor. Patient #1, is alive at 15 months follow-up; hypercortisolemia is controlled using ketoconazole. ACTH-PPC should be entertained in a patient with CD presenting with persistent cervical lymphadenopathy. The clinical course in our patients suggests that the emergence of PC may involve a proliferative continuum from a pre-existing PA to an invasive tumor, culminating in a carcinoma. Adjunctive events such as ERT/ADx may predispose to the evolution of PC in genetically susceptible individuals. Because ERT is an effective treatment for PA its use will continue; it is important to be aware of the possible complication of primary pituitary carcinoma.

Adrenocorticotropic Hormone↗

PubMed2004

Thermal force approach to molecular evolution.

Recent experiments are discussed where temperature gradients across mesoscopic pores are shown to provide essential mechanisms for autonomous molecular evolution. On the one hand, laminar thermal convection can drive DNA replication as the molecules are continuously cycled between hot and cold regions of a chamber. On the other hand, thermophoresis can accumulate charged biopolymers in similar convection settings. The experiments show that temperature differences analogous to those across porous rocks present a robust nonequilibrium boundary condition to feed the replication and accumulation of evolving molecules. It is speculated that similar nonequilibrium conditions near porous submarine hydrothermal mounds could have triggered the origin of life. In such a scenario, the encapsulation of cells with membranes would be a later development. It is expected that detailed studies of mesoscopic boundary conditions under nonequilibrium conditions will reveal new connecting pieces in the fascinating puzzle of the origins of life.

Biophysical Phenomena↗

PubMedDate not supplied

Oscillatory CO2 evolution in glycolysing yeast extracts.

The rate of formation of carbon dioxide in cytoplasmic yeast extracts in an open system with continuous infusion of glucose was measured by membrane inlet mass spectrometry during glycolytic oscillations. The rate of CO2 production rose in the first third of each cycle to a maximum of about 100 mumol per ml yeast extract per hour and subsequently diminished to a final level of about 50 mumol per h. Measurements of the NADH light absorption under the same conditions revealed oscillations of relaxation type. The phase of high CO2 production could be related to the phase of the high NADH level, giving evidence that the flux in glycolysis is increased during the phase of high NADH concentration. Only half of the amount of injected glucose was metabolized to CO2 during the sustained oscillation, although free glucose did not accumulate.

Carbon Dioxide↗

PubMed1990

Angina: evolution of the role of nitrates.

In recent years, concern has been expressed over attenuation of therapeutic effect in patients receiving continuous nitroglycerin therapy for the treatment of angina. Studies have shown that exercise tolerance time does not improve with continuous nitroglycerin regimens, although the frequency of anginal attacks may decrease. Intermittent therapy, which incorporates a nitrate-free interval, improves both exercise time and clinical angina. The optimal duration of the nitrate-free interval has yet to be determined. Future research is likely to focus more on supply-side factors in angina. Of the available antianginal drugs, nitrates have been shown to be highly effective coronary vasodilators, particularly in areas of stenosis.

Angina Pectoris↗

PubMed2005

Evolution of fluorescein as a platform for finely tunable fluorescence probes.

Fluorescence imaging is the most powerful technique currently available for continuous observation of dynamic intracellular processes in living cells. Suitable fluorescence probes are naturally of critical importance for fluorescence imaging, but only a very limited range of biomolecules can currently be visualized because of the lack of flexible design strategies for fluorescence probes. At present, design is largely empirical. Here we show that the carboxylic group of traditional fluorescein dyes, formerly considered indispensable, has been replaced with other substituents, affording various kinds of new fluoresceins. Further, by breaking out of the traditional structure of fluorescein, we developed the first and totally rational design strategy for novel fluorescence probes based on a strict photochemical basis. The value of this approach is exemplified by its application to develop a novel, highly sensitive, and membrane-permeable fluorescence probe for beta-galactosidase, which is the most widely used reporter enzyme.

Biosensing Techniques↗

PubMed2002

Sequence analysis of the ly49 cluster in C57BL/6 mice: a rapidly evolving multigene family in the immune system.

The cytotoxic activity of murine natural killer cells is controlled in part through the action of genes belonging to the Ly49 family. Members of this multigene family are found in a region on mouse chromosome 6 termed the natural killer gene complex. Using data available through public databases, we performed sequence analysis of a 620-kb region in C57Bl/6 (B6) mice that contains the Ly49 genes. The contiguous genomic sequence has allowed us to describe the complete B6 Ly49 gene repertoire, which includes two recently described genes as well as three partial genes. We have shown that the genes in the cluster have evolved through a series of large duplication events involving units of one or more genes and we have attempted to characterize the nature of the duplication end points. Finally, we have used information regarding gene sequence relationships and insertion of repetitive elements to construct a model for the evolution of the gene cluster. Our study illustrates that the Ly49 cluster represents an example of a rapidly evolving gene family, and continued analysis of this region in other strains will undoubtedly provide further insight into mechanisms for generating genomic diversity.

Animals↗

PubMed2005

Entanglement invariants and phylogenetic branching.

It is possible to consider stochastic models of sequence evolution in phylogenetics in the context of a dynamical tensor description inspired from physics. Approaching the problem in this framework allows for the well developed methods of mathematical physics to be exploited in the biological arena. We present the tensor description of the homogeneous continuous time Markov chain model of phylogenetics with branching events generated by dynamical operations. Standard results from phylogenetics are shown to be derivable from the tensor framework. We summarize a powerful approach to entanglement measures in quantum physics and present its relevance to phylogenetic analysis. Entanglement measures are found to give distance measures that are equivalent to, and expand upon, those already known in phylogenetics. In particular we make the connection between the group invariant functions of phylogenetic data and phylogenetic distance functions. We introduce a new distance measure valid for three taxa based on the group invariant function known in physics as the "tangle". All work is presented for the homogeneous continuous time Markov chain model with arbitrary rate matrices.

Evolution, Molecular↗

PubMed1998

Helicobacter pylori: molecular evolution of a bacterial quasi-species.

Helicobacter pylori persists chronically within individuals and as they spread the mutating bacteria migrate with them. The continuous selection and microevolution generates a population of closely related but different bacteria that behave like a quasi-species. Within this heterogeneity, H. pylori strains fall into distinct types, into the virulent (type I) and less virulent (type II) strains, based on the presence of a pathogenicity island (cag) that encodes a specialized secretion machinery. We propose that during chronic infection a dynamic equilibrium between bacteria expressing a disparate degree of virulence is established, and that diverse forms prevail at different times.

Animals↗

PubMed2002

Putting language back in the body: speech and gesture on three time frames.

This article investigates the role that nonverbal actions play in language processing over 3 different time frames. First, we speculate that nonverbal actions played a role in how formal language systems emerged from our primate ancestors over evolutionary time. Next, we hypothesize that if nonverbal behaviors played a foundational role in the emergence of language over evolution, these actions should influence how children learn language in the present. Finally, we argue that nonverbal actions continue to play a role for adults in the moment-to-moment processing of language. Throughout, we take an embodied view of language and argue that the neural, cognitive, and social components of language processing are firmly grounded in bodily action.

Animals↗

PubMed2003

[Information transfer between health structures. How and to whom is the information transferred?].

The evolution of the French health-care system is based on the development of patient management in the health-care system. The public services associate nurses with alternatives to hospitalization in order to favor the emergence of such facilities. This evolution changes the habits and the needs of professionals. Communication between the nurses is the basis of this function. In order to assure the continuity of health-care, both private and hospital nurses need information. However this is either not the case, or is inadequate to the expectations and needs of the nurses. The motives will be analyzed and some proposals offered. In recording and analyzing liaison records, interesting accounts were revealed which foresees the possibilities of an evolution at the information network level between the hospital and the extra-hospital sector. Some propositions will be put forth in order to assure a greater coherence in the endeavor for health-care continuity.

Attitude of Health Personnel↗

PubMed2002

Cryptic designs on the peppered moth.

In a provocative recent book, Jonathan Wells (2000) decries what he discerns as a systematic pattern in how introductory biology textbooks "blatantly misrepresent" ten routinely cited examples offered as evidence for evolution. Each of these examples, according to Wells, is fraught with interpretive problems and, as such, textbooks that continue to use them should at the very least be accompanied by warning labels. The following essay critiques his reasoning with reference to one of these examples, the phenomenon of industrial melanism. After criticizing Wells's specific argument, the essay draws several conclusions about the nature of science lost in his account.

Adaptation, Physiological↗

PubMed2005

Evolution of mechanoregulation of bone growth will lead to non-optimal bone phenotypes.

Mechanical forces acting on the bones during growth affect their final shape and strength. Mechanoregulation of bone growth may be recognized in embryogenesis, and also in the adaptation of the adult skeleton to changes in mechanical loading. Mechanoregulatory responses for tissues have arisen during evolution, but does evolution give rise to responses that produce optimal skeletal phenotypes? In this paper, we investigate the emergence of an optimal mechanoregulation response in a population. By combining equations describing long bone growth with a genetic algorithm to describe evolutionary change, we created a computational model to simulate the evolution of mechanoregulation in bone growth. A population of individuals is created where each individual is assigned a diploid gene set which controls the growth and remodelling of the bone. At maturity, each bone is assessed and its 'fitness' calculated; fitness is quantified as bone strength relative to bone mass. The simulation continues for many generations, and includes mutations and a varying environment. The genes present in the population are tracked and the evolution of parameters governing mechanoregulation is calculated. The results indicate that a population may converge to one bone growth algorithm but, more usually, a range of mechanoregulation algorithms for different individuals will persist after many generations. Even if the population converges to one mechanoregulation law, convergence to the 'optimum' bone was never found. Although many researchers propose that natural selection has pushed skeletal structure towards an optimum, our computational model suggests that this is unlikely to be the case.

Adaptation, Physiological↗

PubMed1996

Structure and function of insect olfactory sensilla.

Olfactory sensilla show a large diversification of sensillum types even in the same species. Thus, double-walled and single-walled sensilla with highly different wall pores are usually found on the same antenna, and these may appear in the form of long slender hairs, pore plates or pit pegs. The selective constraints leading to this diversification are evident only in a few cases, e.g. the demand for extreme sensitivity in moth pheromone communication supported the evolution of long sensilla trichodea with high efficiency of capturing odour molecules. The structural diversity continues with the odorant-binding proteins (OBPs) in the sensillum lymph surrounding the sensory dendrites. These proteins may be subdivided into pheromone-binding proteins and two classes of general odorant-binding proteins according to their primary sequence. Different sensilla of the same morphological type may contain different OBPs of the same or of different subclasses. However, OBPs of different subclasses are not co-localized in the same individual sensory hair. The presence of a given OBP is related more to the functional specificity of the receptor cells than to the morphological type of the sensillum, suggesting a role of OBPs in stimulus recognition.

Animals↗

PubMed2005

Male sex drive and the masculinization of the genome.

Charles Darwin remarked that "males, with their superior strength, pugnacity, armaments, unwieldly passion and love songs, are almost always the more active and most often, the initiators of sexual interactions". Here, we propose that such male sex drive directly impacts the genome by leading to its progressive masculinization--genes that possess sex-specific effects on male fitness accumulate to a much greater extent and are generally more diverged. The larger proportion of male versus female fitness modifiers in combination with stronger sexual selection may generate evolutionary signatures such as a greater sensitivity to male sterility and a paucity of X-linked male-specific genes. Male sex-drive theory complements the female-choice theory of sexual selection and allows for the genetic variation of costly sexual traits to be continuously replenished.

Animals↗

PubMed1993

Involvement of acceptor side components of PSII in the regulatory mechanism of Plectonema boryanum grown photoautotrophically under diazotrophic condition.

Alternating peaks of photosynthetic activity (P-phase) and nitrogen fixing activity (N-phase) were shown in Plectonema boryanum grown under diazotrophic condition in continuous light. In N-phase photosystem I activity increased by 35-45% and oxygen evolution decreased by 70-80% which was partially restored to 45-55% in the presence of 2,6-dichloro-p-benzoquinone. Thermoluminescence glow curve in P-phase consists of a major band at 25 degrees C which was shifted to 10 degrees C in N-phase. Both these bands are sensitive to DCMU and tetranitromethane. Flash excitation studies with major thermoluminescence band in P and N-phase showed oscillations with same periodicity of four having maxima at 2nd and 6th flashes. On the basis of these observations it is suggested that photosynthetic electron transport under diazotrophic growth condition is regulated by the redox levels of the secondary quinone acceptor QB.

Benzoquinones↗