Home About us Contact
|
Home About us Contact | ||
|
|
||
Review I (review + i)
Selected AbstractsA new dimension in combining data?ACTA ZOOLOGICA, Issue 1 2010The use of morphology, phylogenomic data in metazoan systematics Abstract Giribet, G. 2010. A new dimension in combining data? The use of morphology and phylogenomic data in metazoan systematics. ,Acta Zoologica (Stockholm) 91: 11,19 Animal phylogenies have been traditionally inferred by using the character state information derived from the observation of a diverse array of morphological and anatomical features, but the incorporation of molecular data into the toolkit of phylogenetic characters has shifted drastically the way researchers infer phylogenies. A main reason for this is the ease at which molecular data can be obtained, compared to, e.g., traditional histological and microscopical techniques. Researchers now routinely use genomic data for reconstructing relationships among animal phyla (using whole genomes or Expressed Sequence Tags) but the amount of morphological data available to study the same phylogenetic patterns has not grown accordingly. Given the disparity between the amounts of molecular and morphological data, some authors have questioned entire morphological programs. In this review I discuss issues related to the combinability of genomic and morphological data, the informativeness of each set of characters, and conclude with a discussion of how morphology could be made scalable by utilizing new techniques that allow for non-intrusive examination of large amounts of preserved museum specimens. Morphology should therefore remains a strong field in evolutionary and comparative biology, as it continues to provide information for inferring phylogenetic patterns, is an important complement for the patterns derived from the molecular data, and it is the common nexus that allows studying fossil taxa with large data sets of molecular data. [source] Drosophila melanogaster: the model organismENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 2 2006David B. Roberts Abstract In the 20th century, there were two decades during which Drosophila melanogaster was the most significant model organism and each decade led to the establishment of new scientific disciplines. The first decade was roughly from 1910 and during this period a small group at Columbia University, headed by Thomas Hunt Morgan, established the rules of transmission genetics with which we are all familiar. In the second decade, roughly from 1970, many of the principles and techniques of the earlier period were used to determine the genetic control of basic aspects of the biology of organisms, notably their development and their behaviour. In this review I will show that it was not only the genius of the research workers (five were awarded Nobel Prizes and it has been argued, with justification, that at least one more should have been awarded) but also the special features of D. melanogaster that led to these advances. While Drosophila is still a significant model organism, the advent of molecular biology permits the investigation of organisms less amenable to genetic analysis, but the principles applied in these investigations were in the main principles laid down during the earlier work on Drosophila. [source] Variation in Individual Investment Strategies among Social AnimalsETHOLOGY, Issue 8 2006Jan Komdeur Invited Review Abstract Cooperation and conflict are ubiquitous features of life in the vast majority of animals and can occur over a wide range of functional contents and at various levels. In this review I describe known and less well-known proximate aspects of cooperation and conflict over reproductive behaviour in social animals, where individuals other than the genetic parents contribute to the provisioning of care (,alloparental care'). Traditionally the evolution of alloparental care is viewed as a two-step process: the decision to delay dispersal and independent breeding, usually as a consequence of the existence of constraints on independent breeding, and the decision to behave as alloparents by which individuals that have delayed dispersal gain a net fitness benefit. Behavioural ecological theory generally assumes that all individuals are similar in ,make-up' and that life history and behavioural decisions are facultative. However, there is probably more individual variation in the amount and type of social behaviour than originally anticipated. Here, I demonstrate that some of these differences in behaviours are because of environmental factors, which may be associated with ,reaction norms' or the genotype's quantitative phenotypic variation, or which may yield polyethisms. Most evolutionary models of animal cooperation are based on optimality approaches that do not consider individual genetic variation and maternal effects on the variation in the expression of social behaviour. Further research on the genetic basis of cooperations and subordinate,breeder interactions may be crucial for understanding the evolution of social behaviour. If we take individual differences into account our conclusions and explanations of social behaviour may change. Given the conceptual similarities between the various research disciplines addressing different types of cooperation and conflict over investment, the issues described here should lead to more mutual attraction between the different disciplines and stimulate further development in our understanding of cooperation strategies in general. [source] The neuronal MAP kinase cascade: a biochemical signal integration system subserving synaptic plasticity and memoryJOURNAL OF NEUROCHEMISTRY, Issue 1 2001J. David Sweatt The mitogen-activated protein kinase (MAP kinase, MAPK) cascade, as the name implies, was originally discovered as a critical regulator of cell division and differentiation. As further details of this signaling cascade were worked out, it became clear that the MAPK cascade is in fact a prototype for a family of signaling cascades that share the motif of three serially linked kinases regulating each other by sequential phosphorylation. Thus, a revised nomenclature arose that uses the term MAPK to refer to the entire superfamily of signaling cascades (comprising the erks, the JNKs and the p38 stress activated protein kinases), and specifies the prototype MAPK as the extracellular signal-regulated kinase (erk). The two erk MAPK isoforms, p44 MAPK and p42 MAPK, are referred to as erk1 and erk2, respectively. The erks are abundantly expressed in neurons in the mature central nervous system, raising the question of why the prototype molecular regulators of cell division and differentiation are present in these non-dividing, terminally differentiated neurons. This review will describe the beginnings of an answer to this question. Interestingly, the general model has begun to emerge that the erk signaling system has been co-opted in mature neurons to function in synaptic plasticity and memory. Moreover, recent insights have led to the intriguing prospect that these molecules serve as biochemical signal integrators and molecular coincidence detectors for coordinating responses to extracellular signals in neurons. In this review I will first outline the essential components of this signal transduction cascade, and briefly describe recent results implicating the erks in mammalian synaptic plasticity and learning. I will then proceed to outline recent results implicating the erks as molecular signal integrators and, potentially, coincidence detectors. Finally, I will speculate on what the critical downstream effectors of the erks are in neurons, and how they might provide a readout of the integrated signal. [source] INVITED REVIEW: Using genome scans of DNA polymorphism to infer adaptive population divergenceMOLECULAR ECOLOGY, Issue 3 2005JAY F. STORZ Abstract Elucidating the genetic basis of adaptive population divergence is a goal of central importance in evolutionary biology. In principle, it should be possible to identify chromosomal regions involved in adaptive divergence by screening genome-wide patterns of DNA polymorphism to detect the locus-specific signature of positive directional selection. In the case of spatially separated populations that inhabit different environments or sympatric populations that exploit different ecological niches, it is possible to identify loci that underlie divergently selected traits by comparing relative levels of differentiation among large numbers of unlinked markers. In this review I first address the question of whether diversifying selection on polygenic traits can be expected to produce predictable patterns of allelic variation at the underlying quantitative trait loci (QTL), and whether the locus-specific effects of selection can be reliably detected against the genome-wide backdrop of stochastic variability. I then review different approaches that have been developed to identify loci involved in adaptive population divergence and I discuss the relative merits of model-based approaches that rely on assumptions about population structure vs. model-free approaches that are based on empirical distributions of summary statistics. Finally, I consider the evolutionary and functional insights that might be gained by conducting genome scans for loci involved in adaptive population divergence. [source] INVITED REVIEW: Quantitative trait locus mapping in natural populations: progress, caveats and future directionsMOLECULAR ECOLOGY, Issue 2 2005JON SLATE Abstract Over the last 15 years quantitative trait locus (QTL) mapping has become a popular method for understanding the genetic basis of continuous variation in a variety of systems. For example, the technique is now an integral tool in medical genetics, livestock production, plant breeding and population genetics of model organisms. Ten years ago, it was suggested that the method could be used to understand continuous variation in natural populations. In this review I: (i) clarify what is meant by natural population in the QTL context, (ii) discuss whether evolutionary biologists have successfully mapped QTL in natural populations, (iii) highlight some of the questions that have been addressed by QTL mapping in natural populations, (iv) describe how QTL mapping can be conducted in unmanipulated natural populations, (v) highlight some of the limitations of QTL mapping and (vi) try to predict some future directions for QTL mapping in natural populations. [source] Rac and Rho: The Story Behind Melanocyte Dendrite FormationPIGMENT CELL & MELANOMA RESEARCH, Issue 5 2002Glynis Scott Melanocyte dendrites are hormonally responsive actin and microtubule containing structures whose primary purpose is to transport melanosomes to the dendrite tip. Melanocyte dendrites have been an area of intense interest for melanocyte biologists, but it was not until recently that we began to understand the mechanisms underlying their formation. In contrast with melanogenesis, for which numerous mutations in pigment producing genes and mouse models have been identified, a genetic defect resulting in impaired dendrite formation has not been found. Therefore, much of the insight into melanocyte dendrites has come from electron microscopy or in vitro culture systems of normal human and murine melanocytes as well as melanoma cell lines. The growth factors that regulate the formation of melanocyte dendrites have been thoroughly studied and it is clear that multiple signalling systems are able to stimulate, and in some cases inhibit, dendrite formation. Recent data points to the Rho family of small guanosine triphosphate (GTP)-binding proteins as master regulators of dendrite formation, particularly Rac and Rho. In this review I will summarize the progress scientists have made in understanding the structure, hormonal regulation and molecular mediators of melanocyte dendrite formation. [source] The ecology and evolutionary endocrinology of reproduction in the human femaleAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue S49 2009Virginia J. Vitzthum Abstract Human reproductive ecology (HRE) is the study of the mechanisms that link variation in reproductive traits with variation in local habitats. Empirical and theoretical contributions from biological anthropology, physiology, and demography have established the foundation necessary for developing a comprehensive understanding, grounded in life history theory (LHT), of temporal, individual, and populational variation in women's reproductive functioning. LHT posits that natural selection leads to the evolution of mechanisms that tend to allocate resources to the competing demands of growth, reproduction, and survival such that fitness is locally maximized. (That is, among alternative allocation patterns exhibited in a population, those having the highest inclusive fitness will become more common over generational time.) Hence, strategic modulation of reproductive effort is potentially adaptive because investment in a new conception may risk one's own survival, future reproductive opportunities, and/or current offspring survival. The hypothalamic-pituitary-ovarian (HPO) axis is the principal neuroendocrine pathway by which the human female modulates reproductive functioning according to the changing conditions in her habitat. Adjustments of reproductive investment in a potential conception are manifested in temporal and individual variation in ovarian cycle length, ovulation, hormone levels, and the probability of conception. Understanding the extent and causes of adaptive and non-adaptive variation in ovarian functioning is fundamental to ascertaining the proximate and remote determinants of human reproductive patterns. In this review I consider what is known and what still needs to be learned of the ecology of women's reproductive biology, beginning with a discussion of the principal explanatory frameworks in HRE and the biometry of ovarian functioning. Turning next to empirical studies, it is evident that marked variation between cycles, women, and populations is the norm rather than an aberration. Other than woman's age, the determinants of these differences are not well characterized, although developmental conditions, dietary practices, genetic variation, and epigenetic mechanisms have all been hypothesized to play some role. It is also evident that the reproductive functioning of women born and living in arduous conditions is not analogous to that of athletes, dieters, or even the lower end of the "normal range" of HPO functioning in wealthier populations. Contrary to the presumption that humans have low fecundity and an inefficient reproductive system, both theory and present evidence suggest that we may actually have very high fecundity and a reproductive system that has evolved to be flexible, ruthlessly efficient and, most importantly, strategic. Yrbk Phys Anthropol 52:95,136, 2009. © 2009 Wiley-Liss, Inc. [source] Practitioner Review: The Role of Direct Observation in the Assessment of Young ChildrenTHE JOURNAL OF CHILD PSYCHOLOGY AND PSYCHIATRY AND ALLIED DISCIPLINES, Issue 7 2001A. D. Pellegrini In this review I examine the role of play and assessment in the lives of young children. These two seemingly opposing constructs are first defined. Next, I address a particularly important form of assessment, "high stakes" assessment, and argue that if it must be used, we should use a variety of assessment methods. One such method that I discuss in great detail is the use of direct observations of children's play. Examples of reliable and valid inferences about children's social cognitive functioning made with this family of methods are provided. Two specific observational instruments (one for observing play in the classroom and one for observing play in the playground) are presented. Recommendations for their use by practitioners are made. [source] Supersoft X-ray sources and the progenitors of Type Ia supernovaeASTRONOMISCHE NACHRICHTEN, Issue 2 2010Ph. Podsiadlowski Abstract Supersoft X-ray sources have been proposed as one of the major channels to produce Type Ia supernovae (SNe Ia). However, the true nature of the progenitors has remained an unsolved problem. In this review I summarize the present status of our understanding of SN Ia progenitors, the main classes of progenitor models and recent observational constraints. At present, neither the single-degenerate nor the double-degenerate model can be ruled out, and indeed more than one channel may be required to explain the observed SN Ia diversity. Finally, I discuss the origin of the lightcurve peak , lightcurve width relation (the ,Phillips relation') and show that it is expected to depend on metallicity; this needs to be taken into account in high-precision cosmological applications (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] THE WEBSITE,GIRL': CONTEMPORARY THEORIES ABOUT MALE,FEMININITY'BRITISH JOURNAL OF PSYCHOTHERAPY, Issue 1 2005Marie Maguire ABSTRACT I explore a bisexual male patient's need to differentiate highly problematic,feminine'identifications - originating in childhood sexual abuse and impingement by men as well as women - from identifications with more admired aspects of his mother. My main focus is on the patient's sexual identity - the personal meaning he gave to being male - rather than on his bisexuality - his desire for both sexes. In psychoanalytic literature powerful opposite-sex identifications are usually associated either with psychotic confusion or celebrated as a source of psychic strength. The co-existence of problematic and highly valued cross-sex identifications is rarely discussed. I also look at how this patient re-negotiated his identity through the transference relationship with a female psychotherapist, given that his,masculinity'derived mainly from childhood experiences of 'stealing'his mother's phallic power. Through a wideranging theoretical review I conclude that we need to draw together opposing psychoanalytic perspectives about maternal and paternal power, opening up new ways of thinking about triangular relationships in the transference. [source] Non-solid oncogenes in solid tumors: EML4,ALK fusion genes in lung cancerCANCER SCIENCE, Issue 12 2008Hiroyuki Mano It is generally accepted that recurrent chromosome translocations play a major role in the molecular pathogenesis of hematological malignancies but not of solid tumors. However, chromosome translocations involving the e26 transformation-specific sequence transcription factor loci have been demonstrated recently in many prostate cancer cases. Furthermore, through a functional screening with retroviral cDNA expression libraries, we have discovered the fusion-type protein tyrosine kinase echinoderm microtubule-associated protein like-4 (EML4),anaplastic lymphoma kinase (ALK) in non-small cell lung cancer (NSCLC) specimens. A recurrent chromosome translocation, inv(2)(p21p23), in NSCLC generates fused mRNA encoding the amino-terminal half of EML4 ligated to the intracellular region of the receptor-type protein tyrosine kinase ALK. EML4,ALK oligomerizes constitutively in cells through the coiled coil domain within the EML4 region, and becomes activated to exert a marked oncogenicity both in vitro and in vivo. Break and fusion points within the EML4 locus may diverge in NSCLC cells to generate various isoforms of EML4,ALK, which may constitute ~5% of NSCLC cases, at least in the Asian ethnic group. In the present review I summarize how detection of EML4,ALK cDNA may become a sensitive diagnostic means for NSCLC cases that are positive for the fusion gene, and discuss whether suppression of ALK enzymatic activity could be an effective treatment strategy against this intractable disorder. (Cancer Sci 2008; 99: 2349,2355) [source] Photorhabdus: a model for the analysis of pathogenicity and mutualismCELLULAR MICROBIOLOGY, Issue 11 2008David J. Clarke Summary Photorhabdus are entomopathogenic members of the family Enterobacteriaceae. In addition to killing insects Photorhabdus also have a mutualistic association with nematodes from the family Heterorhabditidiae. Therefore, the bacteria have a complex life cycle that involves temporally separated pathogenic and mutualistic associations with two different invertebrate hosts. This tripartite Photorhabdus,insect,nematode association provides researchers with a unique opportunity to characterize the prokaryotic contribution to two different symbioses, i.e. pathogenicity and mutualism while also studying the role of the host in determining the outcome of association with the bacteria. In this review I will outline the life cycle of Photorhabdus and describe recent important advances in our understanding of the symbiology of Photorhabdus. Finally, the contribution made by this model to our understanding of the nature of symbiotic associations will be discussed. [source] | |||||||||||||