Know Little (know + little)

Distribution by Scientific Domains

Selected Abstracts

The spatio-temporal and subcellular expression of the candidate Down syndrome gene Mnb/Dyrk1A in the developing mouse brain suggests distinct sequential roles in neuronal development

Barbara Hämmerle
Abstract It is widely accepted that the neurological alterations in Down syndrome (DS) are principally due to modifications in developmental processes. Accordingly, a large part of the research on DS in recent years has focused on chromosome 21 genes that influence brain development. MNB/DYRK1A is one of the genes on human chromosome 21 that has raised most interest, due to its relationship with the brain functions that are altered in DS. Although a number of interesting experimental mouse models for DS are being developed, we still know little about the expression of Mnb/Dyrk1A during mouse brain development. Here, we report that Mnb/Dyrk1A displays a rather dynamic spatio-temporal expression pattern during mouse central nervous system development. Our data indicate that Mnb/Dyrk1A is specifically expressed in four sequential developmental phases: transient expression in preneurogenic progenitors, cell cycle-regulated expression in neurogenic progenitors, transient expression in recently born neurones, and persistent expression in late differentiating neurones. Our results also suggest that the subcellular localization of MNB/DYRK1A, including its translocation to the nucleus, is finely regulated. Thus, the MNB/DYRK1A protein kinase could be a key element in the molecular machinery that couples sequential events in neuronal development. This rich repertoire of potential functions in the developing central nervous system is suitable to be linked to the neurological alterations in DS through the use of mouse experimental models. [source]

Host reproduction and a sexually transmitted disease: causes and consequences of Coccipolipus hippodamiae distribution on coccinellid beetles

K. Mary Webberley
Summary 1We know that sexually transmitted parasites and pathogens have extremely deleterious effects in human and domesticated animal populations, but know little of sexually transmitted diseases (STDs) in natural populations. 2One previously reported natural system is the sexually transmitted mite, Coccipolipus hippodamiae, on the eastern European coccinellid, Adalia bipunctata. Our aims were to determine how widespread this parasite is in terms of incidence and prevalence across host species, to identify the causes of the prevalence pattern and whether the parasite reduces fertility in all host species. 3Coccipolipus hippodamiae was present on four of 19 European species examined. The wide distribution and high prevalence of C. hippodamiae on A. bipunctata indicates that this is the major host. The mite was also present at substantial prevalence on Adalia decempunctata and at lower prevalence on Synharmonia (=Oenopia) conglobata and Calvia quatuordecimguttata. 4Laboratory studies on mite development time and transmission efficiency revealed that although physiological factors may affect incidence, they do not explain prevalence variation between hosts, but characteristics of host life history and reproductive behaviour are important in this context. Adalia bipunctata is more promiscuous than the less commonly infected A. decempunctata and S. conglobata. Diapause is needed before breeding will occur in C. quatuordecimguttata, leading to a lack of the consistent sexual activity between generations, which is needed for STD maintenance. Calvia quatuordecimguttata is probably periodically reinfected through hybrid matings with other host species. 5Coccipolipus hippodamiae infection has similar strong deleterious effects on female reproduction in A. decempunctata and S. conglobata as have previously been demonstrated in A. bipunctata. 6The results indicate that STDs may play a profound role in the ecology of promiscuous insect populations with overlapping generations. Here they may reach significant prevalence whilst exhibiting extreme virulence. [source]

Hunting for large carnivore conservation

Adrian Treves
Summary 1. Carnivores are difficult to conserve because of direct and indirect competition with people. Public hunts are increasingly proposed to support carnivore conservation. This article reviews scientific evidence for the effectiveness of public hunts of large carnivores in attaining three common policy goals: stable carnivore populations, preventing conflict with carnivores (property damage and competition over game) and building public support for carnivore conservation. 2. Sustainable exploitation of stable wildlife populations has a solid, scientific foundation but the theory and its predictions must be adapted to complex patterns of carnivore behavioural ecology and population dynamics that demand years of landscape-level monitoring to understand fully. 3. A review of the evidence that hunting prevents property damage or reduces competition for game reveals large gaps in our understanding. Reducing the number of large carnivores to protect hunters' quarry species seems straightforward but we still know little about behavioural and ecological responses of the contested prey and sympatric meso-predators. For reducing property damage, the direct effect , numerical reduction in problematic individual carnivores , presents numerous obstacles, whereas the indirect effect , behavioural avoidance of humans by hunted carnivores , holds more promise. 4. Scientific measures of public support for carnivore-hunting policies are almost completely lacking, particularly measures of attitudes among hunters before and after controversial wildlife is designated as legal game species. Moreover, illegal killing of carnivores does not appear to diminish if they are designated as game. 5.Synthesis and applications. Sustainable hunting to maintain stable populations is well understood in theory but complex life histories of carnivores, and behavioural changes of hunters and the carnivores they stalk may result in unsustainable mortality for carnivores. The direct impact of hunting on carnivore damage to property is unclear and even doubtful given the inability or unwillingness of hunters to remove specific individuals selectively. However, hunters may indirectly deter carnivores from people and their property. The assumption that hunters will steward carnivores simply because they have in the past helped conserve other game species requires more study as preliminary results suggest it is incorrect. Policy-makers may achieve support for policy if they mesh utilitarian and preservationist values held by the general public. A number of opposed hypotheses should be disentangled before researchers confidently inform policy on sustainable hunting to prevent conflicts and build public support for carnivore conservation. [source]

The ontogeny of cross-sex genetic correlations: an analysis of patterns

Abstract The independent evolution of males and females is typically constrained by shared genetic variance. Despite substantial research, we still know little about the evolution of cross-sex genetic covariance and its standardized measure, the cross-sex genetic correlation (rMF). In particular, it is unclear if rMF tend to vary with age. We compiled 28 traits for which ontogenetic trends in rMF were documented. Decreases in rMF with age were observed significantly more often than increases and the mean effect size for the relationship between rMF and age was large and negative. This suggests that sexual dimorphism (SD) may typically evolve more readily for phenotypes expressed later in ontogeny and that evolutionary inferences related to the evolution of SD should be limited to the ontogenetic stage at which rMF was estimated. Knowledge about ontogenetic variation in rMF should help improving our understanding of evolutionary patterns related to SD and the resolution of intralocus sexual conflicts. [source]

Religion, Pledging, and the Premarital Sexual Behavior of Married Young Adults

Jeremy E. Uecker
Social scientists know little about the effect of religion and abstinence pledging on premarital sex beyond adolescence. Evidence from a sample of married young adults in the National Longitudinal Study of Adolescent Health (N = 2,079) reveals that premarital sex is widespread even among religious Americans and abstinence pledgers. Nevertheless, these individuals are much more likely than their counterparts to avoid premarital sex entirely. When they do have premarital sex, pledgers are more likely to restrict the behavior to their future spouse. Though contextual, exposure, and social control effects explain some of the influence of religion and abstinence pledging, religion and abstinence pledging appear to exert robust, direct effects on premarital sexual behavior. [source]

Part-time workers and economic expansion: comparing the 1980s and 1990s with U.S. state data,

Mark D. Partridge
Part-time employment; involuntary part-time; regional labor markets; labor shortages Abstract. Economics know little about how the role of part-time workers affect regional labor market dynamics during economic expansion. This study examines this issue using U.S. state data from the 1980s and 1990s. Compared to the 1980s, the labor market during the late 1990s is associated with widespread labor shortages, making this an excellent comparison of how part-time employment responds to economic growth. One key finding is that part-time employment was less responsive to job growth during the 1990s than the 1980s, especially for women. Several explanations are put forth, including firm responses to labor shortages, employer perceptions of inferior part-time worker characteristics and welfare reform. [source]

A Critical Assessment of the Theoretical and Empirical Research on German Works Councils

Carola M. Frege
The article reviews the existing English- and German-speaking literature on the German works council. Three major research topics are discussed: the ontology and typologies of works councils; their current practice and transformation; and their economic outcomes. Although much research has been conducted on the internal functioning of the works council,management relationship, it is clear that we still know little about the determinants of different workplace relations and their outcomes. The article concludes by advocating a reviving research interest in the link between codetermination and political democracy. [source]