Evolutionary genetics: what is driving male mutation?

In mammals, most new mutations occur in males. But a study of the evolution of a human X to Y chromosomal translocation has revealed a sex bias much lower than previous estimates. Patterns of substitution suggest that differential methylation between male and female germ lines is a key determinant of the mutation rate.     

Actin in the nucleus: what form and what for?

Actin is an abundant protein in most nonmuscle cells. It has often been observed in isolated nuclei, yet cytoplasmic contamination was of course initially regarded as the most plausible origin. Numerous studies on nuclear actin appeared in the 1970s and 1980s, but the picture remained rather muddy. The viewpoint at that time was that actin-shown to move freely between cytoplasm and nucleus-was a mere "thermodynamic wanderer," transiently occupying the nucleus. More recently, evidence has been mounting that actin's presence in the nucleus is not simply governed by the laws of diffusion. The same holds true for the finding of various actin-related proteins in the nucleus, and the case for nuclear myosin, specifically myosin I, is now quite convincing. Moreover, the first intimations of functional roles of nuclear actin are now emerging. Here we examine the overall subject from cell biological and chemical perspectives. The major issue is no longer the presence of actin in the nucleus but rather its supramolecular organization, intranuclear locations, and, of course, functions. These issues interface with recent findings that reveal a surprisingly diverse repertoire of actin conformations and oligomer and polymer forms beyond monomeric G-actin and polymeric F-actin. We present ideas for advancing the nuclear actin field and call for a renewed attack on this major problem in cell biology.     

The optimal strategy for brood-parasitism: how many eggs should be laid in the host's nest?

We consider the optimal strategy for intra-specific brood-parasitism, especially with respect to the number of eggs laid by the parasitic individual in the nest of non-parasitic individual, in particular, a host that does not reject the parasite's eggs. With a fundamental mathematical model, assuming that the survival probability of the parasite's offspring in the nest of the host is significantly smaller than that in parasite's own nest, we determine the optimal number of eggs laid in the nest of host that maximizes the expected reproductive fitness of the parasite. We show that the invasion success of brood-parasitism could significantly depend on the total number of eggs laid by the parasite in a breeding season, and that the successfully invading brood-parasitism could realize maximum fitness with a specific number of parasite's eggs laid in the nest of the host.     

Meningitis in tropics--what is the optimal initial therapy?

Risk factors, etiology, epidemiology and initial therapy of community acquired meningitis in tropics is briefly reviewed.     

What is the optimal vitamin D status for health?

The most objectively substantiated health-related reason for tanning is that it improves vitamin D status. The serum 25-hydroxyvitamin D concentration (25(OH)D) is the measure of vitamin D nutrition status. Human biology was probably optimized through natural selection for a sun-rich environment that maintained serum 25(OH)D higher than 100 nmol/L. These levels are now only prevalent in people who spend an above-average amount of time outdoors, with the sun high in the sky. The best-characterized criteria for vitamin D adequacy are based on randomized clinical trials that show fracture prevention and preservation of bone mineral density. Based upon these studies, 25(OH)D concentrations should exceed 75 nmol/L. This concentration is near the upper end of the 25(OH)D reference ("normal") range for populations living in temperate climates, or for people who practice sun-avoidance, or who wear head coverings. Officially mandated nutrition guidelines restrict vitamin D intake from fortified food and supplements to less than 25 mcg/day, a dose objectively shown to raise serum 25(OH)D in adults by about 25 nmol/L. The combined effect of current nutrition guidelines and current sun-avoidance advice is to ensure that adults who follow these recommendations will have 25(OH)D concentrations lower than 75 nmol/L. Therefore, advice to avoid UVB light should be accompanied by encouragement to supplement with vitamin D in an amount that will correct for the nutrient deficit that sun-avoidance will cause.     

Pituitary hormones in the brain: what is their function?

Data concerning the presence in the central nervous system of the anterior and intermediate lobe hormones ACTH, beta-lipotropin, alpha-melanocyte stimulating hormone, beta-endorphin, prolactin, growth hormone, gonadotrophic hormone, and thyrotropin stimulating hormone are reviewed. Available evidence for the ACTH-lipotropin family of peptides indicates that synthesis can occur in brain as well as in pituitary. Although behavioral effects have been described for some of these peptides and their fragments (ACTH, alpha-MSH, beta-endorphin, prolactin), the physiological relevance and the mechanisms of such effects, the nature of the biosynthetic pathways involved, and the factors regulating the brain concentrations of these peptides remain to be explored.     

Quantitative modeling in cell biology: what is it good for?

Recently, there has been a surge in the number of pioneering studies combining experiments with quantitative modeling to explain both relatively simple modules of molecular machinery of the cell and to achieve system-level understanding of cellular networks. Here we discuss the utility and methods of modeling and review several current models of cell signaling, cytoskeletal self-organization, nuclear transport, and the cell cycle. We discuss successes of and barriers to modeling in cell biology and its future directions, and we argue, using the field of bacterial chemotaxis as an example, that the closer the complete systematic understanding of cell behavior is, the more important modeling becomes and the more experiment and theory merge.     

Coxiella burnetii: what is the reality?

After the Second World War, in Italy Q Fever or Coxiellosis has been shown a significant relevance, a recrudescence with an epidemic state for over ten years. Later, the infectious disease occurred as endemic since the 80s, the outbreaks were just isolated. Workflows analysis of some authors has demonstrated the spread out of the infection throughout Italian herds with a prevalence ranging from 1.2 per cent to 10 per cent. Our survey carried out throughout Campania area in cattle has shown a real positivity over 14 per cent performing the IFAT for the detection of IgG antibodies for Coxiella burnetii. Therefore, it has been so important to stress the influence of cattle farming management in stables as a real risk of Coxiellosis. For example, the Relative Risk (RR) has been registrated about 6.84 (2.18相似文献   

What is signal and what is noise in the brain?

The response of a cortical neuron to a stimulus can show a very large variability when repeatedly stimulated by exactly the same stimulus. This has been quantified in terms of inter-spike-interval (ISI) statistics by several researchers (e.g., [Softky, W., Koch, C., 1993. The highly irregular firing of cortical cells is inconsistent with temporal integration of random EPSPs. J. Neurosci. 13(1), 334-350.]). The common view is that this variability reflects noisy information processing based on redundant representation in large neuron populations. This view has been challenged by the idea that the apparent noise inherent in brain activity that is not strictly related or temporally coupled to the experiment could be functionally significant. In this work we examine the ISI statistics and discuss these views in a recently published model of interacting cortical areas [Knoblauch, A., Palm, G., 2002. Scene segmentation by spike synchronization in reciprocally connected visual areas. I. Local effects of cortical feedback. Biol. Cybernet. 87(3), 151-167.]. From the results of further single neuron simulations we can isolate temporally modulated synaptic input as a main contributor for high ISI variability in our model and possibly in real neurons. In contrast to alternative mechanisms, our model suggests a function of the temporal modulations for short-term binding and segmentation of figures from background. Moreover, we show that temporally modulated inputs lead to ISI statistics which fit better to the neurophysiological data than alternative mechanisms.     

Artificial refuges for wildlife conservation: what is the state of the science?

Artificial refuges are human-made structures that aim to create safe places for animals to breed, hibernate, or take shelter in lieu of natural refuges. Artificial refuges are used across the globe to mitigate the impacts of a variety of threats on wildlife, such as habitat loss and degradation. However, there is little understanding of the science underpinning artificial refuges, and what comprises best practice for artificial refuge design and implementation for wildlife conservation. We address this gap by undertaking a systematic review of the current state of artificial refuge research for the conservation of wildlife. We identified 224 studies of artificial refuges being implemented in the field to conserve wildlife species. The current literature on artificial refuges is dominated by studies of arboreal species, primarily birds and bats. Threatening processes addressed by artificial refuges were biological resource use (26%), invasive or problematic species (20%), and agriculture (15%), yet few studies examined artificial refuges specifically for threatened (Vulnerable, Endangered, or Critically Endangered) species (7%). Studies often reported the characteristics of artificial refuges (i.e. refuge size, construction materials; 87%) and surrounding vegetation (35%), but fewer studies measured the thermal properties of artificial refuges (18%), predator activity (17%), or food availability (3%). Almost all studies measured occupancy of the artificial refuges by target species (98%), and over half measured breeding activity (54%), whereas fewer included more detailed measures of fitness, such as breeding productivity (34%) or animal body condition (4%). Evaluating the benefits and impacts of artificial refuges requires sound experimental design, but only 39% of studies compared artificial refuges to experimental controls, and only 10% of studies used a before-after-control-impact (BACI) design. As a consequence, few studies of artificial refuges can determine their overall effect on individuals or populations. We outline a series of key steps in the design, implementation, and monitoring of artificial refuges that are required to avoid perverse outcomes and maximise the chances of achieving conservation objectives. This review highlights a clear need for increased rigour in studies of artificial refuges if they are to play an important role in wildlife conservation.     

Unusual signals in a halo catheter: what is the mechanism?

In this "featured arrhythmia" article we present a set of unusual intracardiac electrode tracings that were recorded in a patient with typical clockwise flutter but a very dilated right atrium. The potential mechanism underlying this phenomenon is discussed with reference to the current literature.