The “Reservation Effect”: Implications for Background Comparisons

A difficult challenge in ecological risk assessment can be determining what constitutes the “background” or ground-state condition for a site. This is because off-site conditions may not reflect to any relevant degree the history of the site itself and may therefore not be appropriate as benchmarks. One of the more important concerns is that underestimates may be made regarding contaminant-related impacts on-site because observations may indicate that community or population quality on-site equals or surpasses that observed off-site. In other cases, overestimates of the degree of contaminant impact may be made if environmental resources on-site are highly managed or devoid of natural communities. As such, management decisions may be confounded by artifacts of non-toxicant-related human influence and will not necessarily appropriately address the contaminant-related issues. Examples of these conditions are discussed herein.     

Preliminary observation of blood cells and hematopoietic organs in Lutjanus herenbergi and Lutjanus flaviflammus

The morphology of differentiated and differentiating cells of the red and white series in Lutjanus herenbergi and in Lutjanus flaviflammus is described. Early stages of red and white blood cells may be found only in smears of hemopoietic organs. Polychromatic erythroblasts, myelocytes and lymphoblasts may also occasionally be found in blood smears. Mature blood cells may be found both in blood smears and in hemopoietic organs. Differential white cell counts seem to demonstrate that the granulocytic series elements are the most common leukocytes in blood smears. Almost all granulocytes may be classified in the first three Arneth classes. An analysis of hemopoietic organs in these species was also performed. It was found that the only organs carrying on a hemopoietic function are the kidney and the spleen. The kidney is essentially a site of granulocytic differentiation while the spleen is a lymphopoietic organ. An erythropoietic activity may generally be observed in the kidney although weak erythropoietic activity may at times be found in the spleen.     

Adaptive noise

In biology, noise implies error and disorder and is therefore something which organisms may seek to minimize and mitigate against. We argue that such noise can be adaptive. Recent studies have shown that gene expression can be noisy, noise can be genetically controlled, genes and gene networks vary in how noisy they are and noise generates phenotypic differences among genetically identical cells. Such phenotypic differences can have fitness benefits, suggesting that evolution can shape noise and that noise may be adaptive. For example, gene networks can generate bistable states resulting in phenotypic diversity and switching among individual cells of a genotype, which may be a bet hedging strategy. Here, we review the sources of noise in gene expression, the extent to which noise in biological systems may be adaptive and suggest that applying evolutionary rigour to the study of noise is necessary to fully understand organismal phenotypes.     

Gout. Imaging of gout: findings and utility

Imaging is a helpful tool for clinicians to evaluate diseases that induce chronic joint inflammation. Chronic gout is associated with changes in joint structures that may be evaluated with diverse imaging techniques. Plain radiographs show typical changes only in advanced chronic gout. Computed tomography may best evaluate bone changes, whereas magnetic resonance imaging is suitable to evaluate soft tissues, synovial membrane thickness, and inflammatory changes. Ultrasonography is a tool that may be used in the clinical setting, allowing evaluation of cartilage, soft tissues, urate crystal deposition, and synovial membrane inflammation. Also ultrasound-guided puncture may be useful for obtaining samples for crystal observation. Any of these techniques deserve some consideration for feasibility and implementation both in clinical practice and as outcome measures for clinical trials. In clinical practice they may be considered mainly for evaluating the presence and extent of crystal deposition, and structural changes that may impair function or functional outcomes, and also to monitor the response to urate-lowering therapy.     

The evolutionary stability of automimicry

Internal defences such as toxins cannot be detected from a distance by a predator, and are likely to be costly to produce and maintain. Populations of well-defended prey may therefore be vulnerable to invasion from rare 'cheater' mutants that do not produce the toxin themselves but obtain some protection from their resemblance to their better defended conspecifics (automimicry). Although it is well established that well-defended and weakly defended morphs may coexist stably in protected dimorphisms, recent theoretical work suggests that such dimorphisms would not be resistant to invasion by novel mutants with defence levels intermediate to those present. Given that most defences (including toxins) are likely to be continuous traits, this implies that automimicry may tend to be a transitory phenomenon, and thus less likely to explain variation in defence levels in nature. In contrast to this, we show that automimicry can also be evolutionarily stable for continuous traits, and that it may evolve under a wide range of conditions. A recently developed geometric method allows us to determine directly from a trade-off curve whether an evolutionarily stable defence dimorphism is at all possible, and to make some qualitative inferences about the ecological conditions that may favour it.     

Pheromonal blends: Certain components may only convey gross information

Certain insect secretions contain 3-octanone and 3-octanol, or 2-heptanone and 2-heptanol. It is shown that the vapour phase composition of each of these binary mixtures may be very different from the liquid phase composition with which it is in equilibrium. It is suggested that there may be little need for biosynthetic exactness in the ratio of some components of pheromone blends and, further more, that certain components of a pheromone blend may be able to convey only gross information rather than subtleties in communication.     

Perspectives on the formation of an interdisciplinary research team

As research funding becomes more competitive, it will be imperative for researchers to break the mentality of a single laboratory/single research focus and develop an interdisciplinary research team aimed at addressing real world challenges. Members of this team may be at the same institution, may be found regionally, or may be international. However, all must share the same passion for a topic that is bigger than any individual’s research focus. Moreover, special consideration should be given to the professional development issues of junior faculty participating in interdisciplinary research teams. While participation may be “humbling” at times, the sheer volume of research progress that may be achieved through interdisciplinary collaboration, even in light of a short supply of grant dollars, is remarkable.     

甜菜树属--我国云南产山柚子科一原始新属及其植物地理学意义

报道了我国云南红河流域山柚子科的一个原始新属－－甜菜树属,该属具大型圆锥花序,两性,是Ｌｅｐｉｏｎｕｒｕｓ,Ｍｅｌｉｅｎｔｈａ和Ｃｈａｍｐｅｕｅｉａ３个单型属的祖型,远远无疑起源于康滇古陆即今之云南高原,其发现对山柚子科的起源分化具重要意义。     

What else can green monkeys tell us about AIDS?

Although the development of an HIV vaccine may eventually provide a means of controlling AIDS in developed countries, more immediate and less sophisticated methods are going to have to be developed for use in the rural regions of Africa where AIDS may already have reached epidemic proportions. Evidence from several studies of wild primates suggests that plant secondary compounds may commonly act as control agents for a variety of different pathogens. Although studies of laboratory populations of green monkeys indicate that their resistance to AIDS is likely to be genetic, we argue that it may be worth screening some of the plants eaten by African primates in the hope of coming up with compounds that exhibit suitable anti-viral activity. Any compounds isolated in this way are likely to be much cheaper to manufacture than laboratory-produced drugs and may also have been already screened for unpleasant side-effects.     

Partnership

Individuals are called partners when it is in their best interest to help each other, if by doing so they increase the probability of being together in the future when, for similar reasons, they will continue to help each other. Kinsmen or individuals who often face (hedonic) situations in which helping is the dominating strategy are committed to help each other. Partnership may develop among them since the loss of the other means the loss of a guaranteed helper. Thus, they may be willing to take additional risks to help each other. Partnership may occur among unrelated individuals and with no hedonic situations. Partnership creates bonds between partners which may be much stronger than those between kinsmen; an individual may take more risks for his partner than he will ever take for a kin. Partnership may evolve without the sophistication and memory required for reciprocation altruism. Although kin selection, partnership and reciprocation are likely to appear fused as the causes for altruism, we argue that it may be possible to distinguish between them in some situations. We show that as the partners get older partnership may become less important to them. We also show that like cooperation, and for analogous reasons, malice may evolve among partners so that each will be willing to take additional risks in order to eliminate the other.     

Non-replication and inconsistency in the genome-wide association setting

Non-replication and inconsistency had been common features in the search for common variants of candidate genes affecting the risk of complex diseases. They may continue to require attention in the current era, when massive hypothesis-free testing of genetic variants is feasible. An empirical evaluation of the early experience with genome-wide association (GWA) studies suggests several examples where proposed associations have failed to be replicated by subsequent investigations. Non-replication and inconsistency is defined here in the framework of cumulative meta-analysis. Ideally, associations exist, GWA finds them, and subsequent investigations should replicate them. However, a number of other possibilities need to be considered. No common genetic variants may associate with the phenotype of interest and GWA may find nothing; or associations may exist, but GWA may miss them. Associations that do not exist may be falsely selected by the GWA and subsequent studies may appropriately refute them or falsely replicate them. Finally, GWA may find true associations that are nevertheless falsely non-replicated in the subsequent studies; or associations may be genuinely inconsistent across study populations. A list of options is presented for consideration in each of these scenarios.     

Applications of the Repeatability of Quantitative Imaging Biomarkers: A Review of Statistical Analysis of Repeat Data Sets

Repeat imaging data sets performed on patients with cancer are becoming publicly available. The potential utility of these data sets for addressing important questions in imaging biomarker development is vast. In particular, these data sets may be useful to help characterize the variability of quantitative parameters derived from imaging. This article reviews statistical analysis that may be performed to use results of repeat imaging to 1) calculate the level of change in parameter value that may be seen in individual patients to confidently characterize that patient as showing true parameter change, 2) calculate the level of change in parameters value that may be seen in individual patients to confidently categorize that patient as showing true lack of parameter change, 3) determine if different imaging devices are interchangeable from the standpoint of repeatability, and 4) estimate the numbers of patients needed to precisely calculate repeatability. In addition, we recommend a set of statistical parameters that should be reported when the repeatability of continuous parameters is studied.     

Physiological parameters in ecotoxicology.

1. Regulated physiological parameters are normally maintained at a constant level by regulatory mechanisms. Acute toxic effects develop whenever a pollutant causes a regulated parameter to be displaced beyond tolerated limits, and thus, regulated parameters may be convenient toxicity parameters. The present study indicates that delta mu Na+ across the adductor muscle membrane of Mytilus edulis is a regulated parameter, and that injuries develop whenever this parameter drops below -700 J/mole. 2. Regulatory physiological parameters may display quick and substantial changes when regulatory mechanisms are activated to counteract variations in the regulated parameters. Thus, regulatory parameters may be used as sensitive alarm parameters in environmental monitoring. The present results indicate that the phosphate index [(ATP x P-arginine)/(Pi)2], metabolic rate and strombine may be used as alarm parameters. 3. The combined response of all parameters may provide a pollutant-specific fingerprint in environmental monitoring.     

Gene conversion may aid adaptive peak shifts

Gene conversion is often viewed as a homogenizing force that opposes adaptive evolution. The objective of this study is to suggest a potential role for gene conversion in adaptive evolution of proteins through aiding the transfer of a population from one adaptive peak to another. Our hypothesis starts with the observation that a tandem gene duplication may result in an extra gene copy that is released from selective constraints. In such cases, individually deleterious mutations may accumulate on the extra copy of the gene, and through gene conversion these mutations may subsequently be presented to the functioning gene for selection en masse. Thus, groups of mutations that jointly confer a selective advantage may regularly be made available for selection. We present a mathematical model of this process and identify the range of rates of gene conversion, gene duplication and mutation under which it may operate. The results indicate that the process may be biologically feasible if the rate of appearance of the potentially beneficial mutations is not too small in relation to the rates of null mutation and of gene conversion. This process appears to be a possible mechanism for effecting adaptive peak shifts in large populations. We show that all the evolutionary steps in the proposed model may have occurred in the evolution of primate gamma -globin genes. We suggest that hide-and-release mechanisms for genetic variation may constitute a more general principal of evolvability.     

Pollen–pistil relationships and pollen size-number trade-off in species of the tribe Lycieae (Solanaceae)

Pollen volume may be involved in different associations with other floral traits. Particularly, the literature indicates that pollen volume can be implicated in a functional relationship with pistil length, and that it may be affected by a trade-off with pollen number because of the subdivision of limited resources. To assess these associations, pollen volume was subjected to correlation analyses with pollen number and pistil length in 20 Argentinean and Chilean taxa of the monophyletic tribe Lycieae. Depending on the mechanisms operating on pollen size and number, the variability of these traits may be different. Therefore, their coefficients of variation were compared. Pistil length and pollen volume showed a strong positive correlation. In contrast, pollen grain size and number were significantly correlated at neither inter- nor intraspecific levels. Results suggest that pollen size and pistil length may co-evolve. The central role of this interaction is discussed. The lack of a correlated variation in pollen size and number may be related to the similar constraints experienced by the species and/or because constraints are operating at the plant level and not at the species level. Lower variance in pollen size compared with pollen number denotes that pollen size may be the main trait subjected to natural selection. Electronic Publication     

Pathogen-induced programmed cell death in plants,a possible defense mechanism

As much as the definition of life may be controversial, the definition of death also may prove problematic. In recent years it became apparent that the death of a living cell may follow more than one possible scenario: it may result from an externally applied physical injury (an accidental death), or it may be the outcome of activating an internal pathway for cell suicide (a programmed death). That cells can participate in their own execution may indicate that certain types of cell deaths that were previously considered to be caused by foreign agents such as pathogens or drugs may actually result from the activation of a programmed cell death pathway that is normally latent in cells. Here, we describe the activation of such a cell suicide pathway in plant cells upon the recognition of an invading pathogen. We discuss the possible use of this pathway as a defense mechanism against infection and the possibility that in many ways the use of this type of cell death in plants is functionally analogous to that used by mammalian cells in response to infection by pathogens. Dev. Genet. 21:279–289, 1997. © 1997 Wiley-Liss, Inc.     

Paradigms in tick evolution

The study of tick evolution may be classified into disciplines such as taxonomy and systematics, biogeography, evolution and development (evo-devo), ecology, and hematophagy. These disciplines overlap and impact each other to various extents. Advances in one field may lead to paradigm shifts in our understanding of tick evolution not apparent to other fields. The current study considers paradigm shifts that occurred, are in the process, or may occur in future for the disciplines that study tick evolution. Some disciplines have undergone significant changes, while others may still be developing their own paradigms. Integration of these various disciplines is essential to come to a holistic view of tick evolution; however, maturation of paradigms may be necessary before this vision can be attained.     

Infanticide by male house sparrows: gaining time or manipulating females?

The killing of genetically unrelated young by males has been viewed as a strategy that forces victimized females to advance the onset of their next fertile period, thus infanticidal males gain a time advantage that may be crucial to maximize reproductive success. Among females that may raise several broods in a year, a failure occurring relatively earlier in the time-course of the previous breeding attempt may result in an increased investment in the next breeding attempt. This female strategy may be exploited by males in their own interest, and may strongly select for male infanticidal behaviour. I demonstrate that, in the house sparrow, females mated with infanticidal males re-laid earlier, initiated more breeding attempts and fledged more offspring than females mated with non-infanticidal males. These results suggest that both the time saving and the manipulation of female investment are independent mechanisms conferring advantages that may have selected for male infanticide in the studied population.     

Thermal bleaching of rhodopsin as a two stage process

We have suggested in a previous publication (1) that there may be two chromophores present in the rhodopsin molecule. The exact nature of these, or the difference between them is not clear, although there is an abundance of evidence available (2–6) to suggest that there may well be two retinal Schiff bases in native rhodopsin. In a purely thermal bleaching reaction in the dark, two clear reaction steps are shown to occur and while these may or may not involve the same chromophore, it will be shown that the reactions involve quite different activation energies and markedly different entropies of activation.     

Increased genetic variance after a population bottleneck

A conventional view holds that population bottlenecks cause massive losses of genetic variability, thus endangering the viability of the derived population. Although some alleles that were infrequent in the parent population may be lost new empirical evidence from Drosophila and housefly populations has demonstrated that genetic variance available to selection may actually increase following a single severe bottleneck. Several theoretical models support this view, and suggest that the increase may result from conversion of balanced epistatic variance to additive variance that becomes immediately available to selection. These effects appear to be greatest on the inheritance of quantitative characters, releasing new variance through the disruption of covariance matrices that underlie and interrelate quantitative traits. Thus, character change in adaptation and speciation may, in some instances, be promoted by founder events.