Myrothecium roridum and M. verrucaria are two plant pathogenic species causing foliar spots in a large number of cultivated plants. This paper aims to study the causal agents of foliar spots in vegetable crops (sweet pepper, tomato, cucumber), ornamental plants (Spathiphyllum, Solidago canadensis, Anthurium,
Dieffenbachia) and a solanaceous weed plant (Nicandra physalodes). Most of the isolates were identified as M. roridum; only the isolate ‘Myr-02’ from S. canadensis was identified as M. verrucaria. All the isolates were pathogenic to their original plant hosts and also to some other plants. Some fungicides were tested in vitro against an isolate of M. roridum and the mycelial growth recorded after seven days. Fungicides with quartenary ammonium, Tebuconzole and copper were highly effective in inhibiting the mycelial growth of M. roridum. This paper confirms the first record of M. roridum causing leaf spots in sweet pepper, tomato, Spathiphyllum, Anthurium, Dieffenbachia and N. physalodes. We also report M. roridum as causal agent of cucumber fruit rot and also M. verrucaria in tango plants.
Myrothecium roridum; M. verrucaria; vegetable crops; quorum sensing; weeds; etiology
Qualitative methodologies are increasingly popular in medical research. Grounded theory is the methodology most-often cited by authors of qualitative studies in medicine, but it has been suggested that many 'grounded theory' studies are not concordant with the methodology. In this paper we provide a worked example of a grounded theory project. Our aim is to provide a model for practice, to connect medical researchers with a useful methodology, and to increase the quality of 'grounded theory' research published in the medical literature.
We documented a worked example of using grounded theory methodology in practice.
We describe our sampling, data collection, data analysis and interpretation. We explain how these steps were consistent with grounded theory methodology, and show how they related to one another. Grounded theory methodology assisted us to develop a detailed model of the process of adapting preventive protocols into dental practice, and to analyse variation in this process in different dental practices.
By employing grounded theory methodology rigorously, medical researchers can better design and justify their methods, and produce high-quality findings that will be more useful to patients, professionals and the research community.
qualitative research; grounded theory; methodology; methods; dental care
The lateral geniculate nucleus of the cat was explored with micropipettes having submicroscopic tips. The only reliably recorded intracellular activity was from axons. Following orthodromic stimulation, the potentials recorded by the extracellular electrodes registered the net flow of current across the soma-dendritic membrane of the principal cell bodies. The current has three phases of flow away from the soma-dendritic membrane followed by a flow of current toward this membrane. The first component is ascribed to synaptic activity. Subsequent components are ascribed to the activity of the initial segment of the axon and a limited area of high threshold membrane on the soma. The evidence is interpreted as suggesting that most of the soma-dendritic membrane is excited synaptically to produce a postsynaptic potential, but is not excited electrically and does not produce a propagating spike.
This paper examines the theoretical underpinning of the community based approach to health and safety programs. Drawing upon the literature, a theory is constructed by elucidating assumptions of community based programs. The theory is then put to test by analyzing the extent to which the assumptions are supported by empirical evidence and the extent to which the assumptions have been applied in community based injury prevention practice. Seven principles representing key assumptions of the community based approach to health and safety programs are identified. The analysis suggests that some of the principles may have important shortcomings. Programs overwhelmingly define geographical or geopolitical units as communities, which is problematic considering that these entities can be heterogeneous and characterized by a weak sense of community. This may yield insufficient community mobilization and inadequate program reach. At the same time, none of the principles identified as most plausible appears to be widely or fully applied in program practice. The implication is that many community based health and safety programs do not function at an optimum level, which could explain some of the difficulties in demonstrating effectiveness seen with many of these programs.
community‐based approach; characteristics; theory; assumptions; practice
Large volumes of morphological descriptions of whole organisms have been created as print or electronic text in a human-readable format. Converting the descriptions into computer- readable formats gives a new life to the valuable knowledge on biodiversity. Research in this area started 20 years ago, yet not sufficient progress has been made to produce an automated system that requires only minimal human intervention but works on descriptions of various plant and animal groups. This paper attempts to examine the hindering factors by identifying the mismatches between existing research and the characteristics of morphological descriptions.
This paper reviews the techniques that have been used for automated annotation, reports exploratory results on characteristics of morphological descriptions as a genre, and identifies challenges facing automated annotation systems. Based on these criteria, the paper proposes an overall strategy for converting descriptions of various taxon groups with the least human effort.
A combined unsupervised and supervised machine learning strategy is needed to construct domain ontologies and lexicons and to ultimately achieve automated semantic annotation of morphological descriptions. Further, we suggest that each effort in creating a new description or annotating an individual description collection should be shared and contribute to the "biodiversity information commons" for the Semantic Web. This cannot be done without a sound strategy and a close partnership between and among information scientists and biologists.
Those attempting to implement changes in health care settings often find that intervention efforts do not progress as expected. Unexpected outcomes are often attributed to variation and/or error in implementation processes. We argue that some unanticipated variation in intervention outcomes arises because unexpected conversations emerge during intervention attempts. The purpose of this paper is to discuss the role of conversation in shaping interventions and to explain why conversation is important in intervention efforts in health care organizations. We draw on literature from sociolinguistics and complex adaptive systems theory to create an interpretive framework and develop our theory. We use insights from a fourteen-year program of research, including both descriptive and intervention studies undertaken to understand and assist primary care practices in making sustainable changes. We enfold these literatures and these insights to articulate a common failure of overlooking the role of conversation in intervention success, and to develop a theoretical argument for the importance of paying attention to the role of conversation in health care interventions.
Conversation between organizational members plays an important role in the success of interventions aimed at improving health care delivery. Conversation can facilitate intervention success because interventions often rely on new sensemaking and learning, and these are accomplished through conversation. Conversely, conversation can block the success of an intervention by inhibiting sensemaking and learning. Furthermore, the existing relationship contexts of an organization can influence these conversational possibilities. We argue that the likelihood of intervention success will increase if the role of conversation is considered in the intervention process.
The generation of productive conversation should be considered as one of the foundations of intervention efforts. We suggest that intervention facilitators consider the following actions as strategies for reducing the barriers that conversation can present and for using conversation to leverage improvement change: evaluate existing conversation and relationship systems, look for and leverage unexpected conversation, create time and space where conversation can unfold, use conversation to help people manage uncertainty, use conversation to help reorganize relationships, and build social interaction competence.
While the concept of population growth rate has been of central importance in the development of the theory of population dynamics, few empirical studies consider the intrinsic growth rate in detail, let alone how it may vary within and between populations of the same species. In an attempt to link theory with data we take two approaches. First, we address the question 'what growth rate patterns does theory predict we should see in time-series?' The models make a number of predictions, which in general are supported by a comparative study between time-series of harvesting data from 352 red grouse populations. Variations in growth rate between grouse populations were associated with factors that reflected the quality and availability of the main food plant of the grouse. However, while these results support predictions from theory, they provide no clear insight into the mechanisms influencing reductions in population growth rate and regulation. In the second part of the paper, we consider the results of experiments, first at the individual level and then at the population level, to identify the important mechanisms influencing changes in individual productivity and population growth rate. The parasitic nematode Trichostrongylus tenuis is found to have an important influence on productivity, and when incorporated into models with their patterns of distribution between individuals has a destabilizing effect and generates negative growth rates. The hypothesis that negative growth rates at the population level were caused by parasites was demonstrated by a replicated population level experiment. With a sound and tested model framework we then explore the interaction with other natural enemies and show that in general they tend to stabilize variations in growth rate. Interestingly, the models show selective predators that remove heavily infected individuals can release the grouse from parasite-induced regulation and allow equilibrium populations to rise. By contrast, a tick-borne virus that killed chicks simply leads to a reduction in the equilibrium. When humans take grouse they do not appear to stabilize populations and this may be because many of the infective stages are available for infection before harvesting commences. In our opinion, an understanding of growth rates and population dynamics is best achieved through a mechanistic approach that includes a sound experimental approach with the development of models. Models can be tested further to explore how the community of predators and others interact with their prey.
The non-availability of reliable and standardized drugs, their high cost, and ambiguity in the identity of the ingredients used are a few of the major problems encountered today in the utilization of compound drugs in Ayurveda. There is thus an urgent need to reemphasize the use of single plant drug formulations recorded in the classical texts. The present study is an attempt to list out all the single plant drugs mentioned in the treatment of various Netrarogas from the classical texts of Ayurveda and to fix their proper botanical identity. The study of 7 classical texts has revealed that there are 41 single plant drugs in 80 preparations for treating 9 lakshanas and 29 rogas. They have been correlated with their botanical identities based on nomenclature correlation studies published over the last century. The drugs are arranged alphabetically with their botanical names, habit, indications, parts used, method of preparation, mode of administration and the reference, A primary analysis has also been made on the nomenclature, qualities and applications of the drugs.
The rich dynamical nature of neurons poses major conceptual and technical challenges for unraveling their nonlinear membrane properties. Traditionally, various current waveforms have been injected at the soma to probe neuron dynamics, but the rationale for selecting specific stimuli has never been rigorously justified. The present experimental and theoretical study proposes a novel framework, inspired by learning theory, for objectively selecting the stimuli that best unravel the neuron's dynamics. The efficacy of stimuli is assessed in terms of their ability to constrain the parameter space of biophysically detailed conductance-based models that faithfully replicate the neuron's dynamics as attested by their ability to generalize well to the neuron's response to novel experimental stimuli. We used this framework to evaluate a variety of stimuli in different types of cortical neurons, ages and animals. Despite their simplicity, a set of stimuli consisting of step and ramp current pulses outperforms synaptic-like noisy stimuli in revealing the dynamics of these neurons. The general framework that we propose paves a new way for defining, evaluating and standardizing effective electrical probing of neurons and will thus lay the foundation for a much deeper understanding of the electrical nature of these highly sophisticated and non-linear devices and of the neuronal networks that they compose.
Neurons perform complicated non-linear transformations on their input before producing their output - a train of action potentials. This input-output transformation is shaped by the specific composition of ion channels, out of the many possible types, that are embedded in the neuron's membrane. Experimentally, characterizing this transformation relies on injecting different stimuli to the neuron while recording its output; but which of the many possible stimuli should one apply? This combined experimental and theoretical study provides a general theoretical framework for answering this question, examining how different stimuli constrain the space of faithful conductance-based models of the studied neuron. We show that combinations of intracellular step and ramp currents enable the construction of models that both replicate the cell's response and generalize very well to novel stimuli e.g., to “noisy” stimuli mimicking synaptic activity. We experimentally verified our theoretical predictions on several cortical neuron types. This work presents a novel method for reliably linking the microscopic membrane ion channels to the macroscopic electrical behavior of neurons. It provides a much-needed rationale for selecting a particular stimulus set for studying the input-output properties of neurons and paves the way for standardization of experimental protocols along with construction of reliable neuron models.
Although the social situation for gay, lesbian, and bisexual people has improved over the last decades, lesbian women still face unique challenges when seeking healthcare services.
To explore lesbian women's healthcare experiences specifically related to sexual orientation to achieve knowledge which can contribute to increased quality of healthcare for lesbian women.
Qualitative study based on written stories, with recruitment, information, and data sampling over the internet. Data consisted of 128 anonymously written answers to a web-based, open-ended questionnaire from a convenience sample of self-identified lesbian women. Data were analysed with systematic text condensation. Interpretation of findings was supported by theories of heteronormativity.
Main outcome measures
Patients’ histories of experiences where a lesbian orientation was significant, when seeing a doctor or another healthcare professional.
Analysis presented three different aspects of healthcare professionals’ abilities, regarded as essential by our lesbian participants. First, the perspective of awareness was addressed – is the healthcare professional able to think of and facilitate the disclosure of a lesbian orientation? Second, histories pointed to the attitudes towards homosexuality – does the healthcare professional acknowledge and respect the lesbian orientation? Third, the impact of specific and adequate medical knowledge was emphasized – does the healthcare professional know enough about the specific health concerns of lesbian women?
To obtain quality care for lesbian women, the healthcare professional needs a persistent awareness that not all patients are heterosexual, an open attitude towards a lesbian orientation, and specific knowledge of lesbian health issues. The dimensions of awareness, attitude, and knowledge are interconnected, and a positive direction on all three dimensions appears to be a necessary prerequisite.
Attitude of health personnel; family practice; health services accessibility; homosexuality; female; minority health; prejudice; self-disclosure
The author probes in this paper the identity of ‘Kumbika’ multifaceted plant-species mentioned in the Ayurvedic literature and establishes its identity by interpreting various classical texts.
Semantic dementia is characterized by semantic deficits and behavioural abnormalities which occur in the wake of bilateral inferolateral and predominantly left-sided anterior temporal lobe atrophy. The temporal poles have been shown to be involved in theory of mind, namely the ability to ascribe cognitive and affective mental states to others that regulates social interactions by predicting and interpreting human behaviour. However, very few studies have examined theory of mind in semantic dementia. In this study, we investigated both cognitive and affective theory of mind in a group of semantic dementia patients, using separate objective and subjective assessment tasks. Results provided objective evidence of an impact of semantic dementia on cognitive and affective theory of mind, consistent with the patients’ atrophy in the left temporal lobe and hypometabolism in the temporal lobes and the medial frontal cortex. However, the subjective assessment of theory of mind suggested that awareness of the affective but not cognitive theory of mind deficit persists into the moderate stage of the disease.
Aged; Atrophy; pathology; psychology; Attention; Executive Function; Female; Frontotemporal Lobar Degeneration; pathology; psychology; Humans; Male; Memory; Middle Aged; Neuropsychological Tests; Temporal Lobe; pathology; Theory of Mind; semantic dementia; cognitive/affective theory of mind; objective/subjective assessment; imaging.
Individuals with autism spectrum disorders (ASD) have impairments in social interaction, communicative capacity, and behavioral flexibility (core triad). Three major cognitive theories (theory of mind deficit, weak central coherence, and executive dysfunction) seem to explain many of these impairments. Currently, however, the empathizing-systemizing (a newer version of the theory of mind deficit account) and mnesic imbalance theories are the only ones that attempt to explain all these core triadic symptoms of ASD On the other hand, theory of mind deficit in empathizing-systemizing theory is the most influential account for ASD, but its counterpart in the mnesic imbalance theory, faulty procedural memory, seems to occur earlier in development; consequently, this might be a better solution to the problem of the etiology of ASD, if it truly meets the precedence criterion. Hence, in the present paper I review the reasoning in favor of the theory of mind deficit but with a new interpretation based on the mnesic imbalance theory, which posits that faulty procedural memory causes deficits in several cognitive skills, resulting in poor performance in theory of mind tasks.
1. Senescence, the physiological decline that results in decreasing survival and/or reproduction with age, remains one of the most perplexing topics in biology. Most theories explaining the evolution of senescence (i.e. antagonistic pleiotropy, accumulation of mutations, disposable soma) were developed decades ago. Even though these theories have implicitly focused on unitary animals, they have also been used as the foundation from which the universality of senescence across the tree of life is assumed.
2. Surprisingly, little is known about the general patterns, causes and consequences of whole-individual senescence in the plant kingdom. There are important differences between plants and most animals, including modular architecture, the absence of early determination of cell lines between the soma and gametes, and cellular division that does not always shorten telomere length. These characteristics violate the basic assumptions of the classical theories of senescence and therefore call the generality of senescence theories into question.
3. This Special Feature contributes to the field of whole-individual plant senescence with five research articles addressing topics ranging from physiology to demographic modelling and comparative analyses. These articles critically examine the basic assumptions of senescence theories such as age-specific gene action, the evolution of senescence regardless of the organism's architecture and environmental filtering, and the role of abiotic agents on mortality trajectories.
Synthesis. Understanding the conditions under which senescence has evolved is of general importance across biology, ecology, evolution, conservation biology, medicine, gerontology, law and social sciences. The question ‘why is senescence universal or why is it not?’ naturally calls for an evolutionary perspective. Senescence is a puzzling phenomenon, and new insights will be gained by uniting methods, theories and observations from formal demography, animal demography and plant population ecology. Plants are more amenable than animals to experiments investigating senescence, and there is a wealth of published plant demographic data that enable interpretation of experimental results in the context of their full life cycles. It is time to make plants count in the field of senescence.
ageing; antagonistic pleiotropy; comparative plant demography; disposable soma; dormancy; longevity; mutation accumulation; oxidative stress; plant development and life-history traits; senescence
The objective of this study is to identify features and content that short message service (SMS) should have in order to motivate HIV testing among men who have sex with men (MSM) in Lima, Peru.
From October, 2010 to February, 2011, we conducted focus groups at two stages; six focus groups were conducted to explore and identify SMS content and features and two additional focus groups were conducted to tailor SMS content. The text messages were elaborated within the theoretical framework of the Information-Motivation-Behavioral Skills model and the Social Support Theory.
A total of 62 individuals participated in the focus groups. The mean age of participants was 28 years (range 18-39). We identified important features and content items needed for the successful delivery of text messages, including: a) the use of neutral and coded language; b) appropriate frequency and time of delivery; c) avoiding mass and repetitive messages; and d) use of short, concise and creative messages. Although in Peru receiving text messages is usually a free service, it is important to remind participants that receiving messages will be free of charge.
Text messages can be used to promote HIV testing among Peruvian MSM. It is important to consider adequate frequency, message content and cost when delivering messages to promote HIV testing in this population.
Cellular phone; men who have sex with men; HIV prevention; HIV testing; risk behaviors; text messaging.
Major intrinsic proteins (MIPs) also named aquaporins form channels facilitating the passive transport of water and other small polar molecules across membranes. MIPs are particularly abundant and diverse in terrestrial plants but little is known about their evolutionary history. In an attempt to investigate the origin of the plant MIP subfamilies, genomes of chlorophyte algae, the sister group of charophyte algae and land plants, were searched for MIP encoding genes.
A total of 22 MIPs were identified in the nine analysed genomes and phylogenetic analyses classified them into seven subfamilies. Two of these, Plasma membrane Intrinsic Proteins (PIPs) and GlpF-like Intrinsic Proteins (GIPs), are also present in land plants and divergence dating support a common origin of these algal and land plant MIPs, predating the evolution of terrestrial plants. The subfamilies unique to algae were named MIPA to MIPE to facilitate the use of a common nomenclature for plant MIPs reflecting phylogenetically stable groups. All of the investigated genomes contained at least one MIP gene but only a few species encoded MIPs belonging to more than one subfamily.
Our results suggest that at least two of the seven subfamilies found in land plants were present already in an algal ancestor. The total variation of MIPs and the number of different subfamilies in chlorophyte algae is likely to be even higher than that found in land plants. Our analyses indicate that genetic exchanges between several of the algal subfamilies have occurred. The PIP1 and PIP2 groups and the Ca2+ gating appear to be specific to land plants whereas the pH gating is a more ancient characteristic shared by all PIPs. Further studies are needed to discern the function of the algal specific subfamilies MIPA-E and to fully understand the evolutionary relationship of algal and terrestrial plant MIPs.
Bennett and Hacker use conceptual analysis to appraise the theoretical language of modern cognitive neuroscientists, and conclude that neuroscientific theory is largely dualistic despite the fact that neuroscientists equate mind with the operations of the brain. The central error of cognitive neuroscientists is to commit the mereological fallacy, the tendency to ascribe to the brain psychological concepts that only make sense when ascribed to whole animals. The authors review how the mereological fallacy is committed in theories of memory, perception, thinking, imagery, belief, consciousness, and other psychological processes studied by neuroscientists, and the consequences that fallacious reasoning have for our understanding of how the brain participates in cognition and behavior. Several behavior-analytic concepts may themselves be nonsense based on thorough conceptual analyses in which the criteria for sense and nonsense are found in the ways the concepts are used in ordinary language. Nevertheless, the authors' nondualistic approach and their consistent focus on behavioral criteria for the application of psychological concepts make Philosophical Foundations of Neuroscience an important contribution to cognitive neuroscience.
cognitive neuroscience; conceptual analysis; dualism; mereological fallacy; reductionism
Plant ecologists have proposed a variety of optimization theories to explain the adaptive behaviour and evolution of plants from the perspective of natural selection (‘survival of the fittest’). Optimization theories identify some objective function—such as shoot or canopy photosynthesis, or growth rate—which is maximized with respect to one or more plant functional traits. However, the link between these objective functions and individual plant fitness is seldom quantified and there remains some uncertainty about the most appropriate choice of objective function to use. Here, plants are viewed from an alternative thermodynamic perspective, as members of a wider class of non-equilibrium systems for which maximum entropy production (MEP) has been proposed as a common theoretical principle. I show how MEP unifies different plant optimization theories that have been proposed previously on the basis of ad hoc measures of individual fitness—the different objective functions of these theories emerge as examples of entropy production on different spatio-temporal scales. The proposed statistical explanation of MEP, that states of MEP are by far the most probable ones, suggests a new and extended paradigm for biological evolution—‘survival of the likeliest’—which applies from biomacromolecules to ecosystems, not just to individuals.
entropy production; natural selection; optimization; plants
This article describes the integrative model of behavioral prediction (IM), the latest formulation of a reasoned action approach. The IM attempts to identify a limited set of variables that can account for a considerable proportion of the variance in any given behavior. More specifically, consistent with the original theory of reasoned action, the IM assumes that intentions are the immediate antecedents of behavior, but in addition, the IM recognizes that environmental factors and skills and abilities can moderate the intention-behavior relationship. Similar to the theory of planned behavior, the IM also assumes that intentions are a function of attitudes, perceived normative pressure and self-efficacy, but it views perceived normative pressure as a function of descriptive as well as of injunctive (i.e., subjective) norms. After describing the theory and addressing some of the criticisms directed at a reasoned action approach, the paper illustrates how the theory can be applied to understanding and changing health related behaviors.
medical decision making; attitude; behavioral prediction; reasoned action; integrative model
In this paper the author attempts to trace the ancient man and his conceptualism of drugs and cosmology by interpreting various classical texts related to that field.
Classical Marr-Albus theories of cerebellar learning employ only cortical sites of plasticity. However, tests of these theories using adaptive calibration of the vestibulo–ocular reflex (VOR) have indicated plasticity in both cerebellar cortex and the brainstem. To resolve this long-standing conflict, we attempted to identify the computational role of the brainstem site, by using an adaptive filter version of the cerebellar microcircuit to model VOR calibration for changes in the oculomotor plant. With only cortical plasticity, introducing a realistic delay in the retinal-slip error signal of 100 ms prevented learning at frequencies higher than 2.5 Hz, although the VOR itself is accurate up to at least 25 Hz. However, the introduction of an additional brainstem site of plasticity, driven by the correlation between cerebellar and vestibular inputs, overcame the 2.5 Hz limitation and allowed learning of accurate high-frequency gains. This “cortex-first” learning mechanism is consistent with a wide variety of evidence concerning the role of the flocculus in VOR calibration, and complements rather than replaces the previously proposed “brainstem-first” mechanism that operates when ocular tracking mechanisms are effective. These results (i) describe a process whereby information originally learnt in one area of the brain (cerebellar cortex) can be transferred and expressed in another (brainstem), and (ii) indicate for the first time why a brainstem site of plasticity is actually required by Marr-Albus type models when high-frequency gains must be learned in the presence of error delay.
Our ability to learn skilled movements depends crucially on the cerebellum, hence understanding cerebellar plasticity is central to theories of motor learning. The adaptation of the vestibulo-ocular reflex (VOR) is often used to test these theories. This reflex stabilizes the retinal image by moving the eyes to compensate for head movements signaled by the vestibular system. There is a long-standing puzzle in that classical Marr-Albus theories of VOR adaptation only require sites of plasticity in cerebellar cortex whereas experiment reveals plasticity in both cerebellar cortex and brainstem. We resolve this puzzle by showing that unavoidable delays in processing retinal slip severely limit cerebellar performance at high frequencies but that introducing a second brainstem site of plasticity driven by the correlation between cerebellar and vestibular inputs overcomes this limitation. Hence a second site of plasticity is required by Marr-Albus models for high-frequency learning in the presence of delay. The plasticity mechanism we describe is of general interest because it provides a biologically plausible route by which motor information learnt in one brain area (cerebellar cortex) can be transferred to and expressed in another area (the brain stem).
As an epilogue to the themed papers on “Theories of Schizophrenia” in this issue of Schizophrenia Bulletin, this article reviews some basic philosophy of science principles in regard to the role of theories in the evolving state of a natural science discipline. While in early phases inductive and abductive logic are the primary vehicles for organizing observations and developing models, when a critical set of “facts” have been elucidated which can be explained by competing theoretical perspectives, hypothetico-deductive logic provides a more robust and efficient approach to scientific progress. The key principle is to determine where two or more theories predict different observations and then to devise studies that collect critical observations—correlations or experimental outcomes that are predicted differentially by the competing theories. To a large extent, current theories of schizophrenia (eg, focusing on aberrant dopaminergic signaling, neural dysconnectivity, and disrupted neural development) are not (and are not intended by their authors to be) mutually exclusive of each other. Rather, they provide explanations that differ in relative emphases, eg, on distal vs proximal causes and on broad vs narrow behavioral end points. It is therefore possible for all of them to be “right” at least in a general sense. This non-exclusivity is problematic when considered in light of the strong inferences principles characteristic of a mature natural science discipline. The contrast points are likely to be found in constructions that integrate influences across different levels of analysis, as in additive vs interactive models, direct effects vs mediation models, and developmental vs deteriorative models.
schizophrenia; theory; philosophy of science
Low and oscillatory wall shear stress is widely assumed to play a key role in the initiation and development of atherosclerosis. Indeed, some studies have relied on the low shear theory when developing diagnostic and treatment strategies for cardiovascular disease. We wished to ascertain if this consensus is justified by published data. We performed a systematic review of papers that compare the localization of atherosclerotic lesions with the distribution of haemodynamic indicators calculated using computational fluid dynamics. The review showed that although many articles claim their results conform to the theory, it has been interpreted in different ways: a range of metrics has been used to characterize the distribution of disease, and they have been compared with a range of haemodynamic factors. Several studies, including all of those making systematic point-by-point comparisons of shear and disease, failed to find the expected relation. The various pre- and post-processing techniques used by different groups have reduced the range of shears over which correlations were sought, and in some cases are mutually incompatible. Finally, only a subset of the known patterns of disease has been investigated. The evidence for the low/oscillatory shear theory is less robust than commonly assumed. Longitudinal studies starting from the healthy state, or the collection of average flow metrics derived from large numbers of healthy vessels, both in conjunction with point-by-point comparisons using appropriate statistical techniques, will be necessary to improve our understanding of the relation between blood flow and atherogenesis.
Atherosclerosis; Haemodynamics; Blood flow; Arterial disease; Shear stress
Key aspects of seed development in flowering plants are held to be under epigenetic control and to have evolved as a result of conflict between the interests of the male and female gametes (kinship theory). Attempts to identify the genes involved have focused on imprinted sequences, although imprinting is only one mechanism by which male or female parental alleles may be exclusively expressed immediately post-fertilization. We have studied the expression of a subset of endosperm gene classes immediately following interploidy crosses in maize and show that departure from the normal 2 : 1 ratio between female and male genomes exerts a dramatic effect on the timing of expression of some, but not all, genes investigated. Paternal genomic excess prolongs the expression of early genes and delays accumulation of reserves, while maternal genomic excess foreshortens the expression period of early genes and dramatically brings forward endosperm maturation. Our data point to a striking interdependence between the phases of endosperm development, and are consonant with previous work from maize showing progression from cell proliferation to endoreduplication is regulated by the balance between maternal and paternal genomes, and from Arabidopsis suggesting that this ‘phasing’ is regulated by maternally expressed imprinted genes. Our findings are discussed in context of the kinship theory.
endosperm; imprinting; interploidy crosses; kinship theory; maize (Zea mays); plant fertilization
Neuropsychological theories have traditionally attempted to provide a unifying account of the complex and diverse behavioral manifestations of autism in terms of their underlying psychological mechanisms and associated brain bases. This article reviews three competing neuropsychological theories of autism: the executive dysfunction hypothesis, the weak central coherence hypothesis, and the limbic system hypothesis. Each theory is evaluated critically with regard to the primary neuropsychological deficit hypothesized and the research findings that have been offered in support of it. In a concluding section, some of the metatheoretical assumptions informing attempts to identify a “core” neuropsychological impairment in autism are outlined and questioned, and new approaches to a neuropsychological understanding of autism are suggested.