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Main Explanation (main + explanation)
Selected AbstractsInsulin analogues: have they changed insulin treatment and improved glycaemic control?DIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue S1 2002Sten Madsbad Abstract To improve insulin therapy, new insulin analogues have been developed. Two fast-acting analogues with a more rapid onset of effect and a shorter duration of action combined with a low day-to-day variation in absorption rate are now available. Despite this favourable time,action profile most studies have not been able to show any improvement in overall glycaemic control with the fast-acting analogues. A reduced post-prandial increase in blood glucose has been found in all studies, whereas between 3 and 5,h after the meal and during the night an increased blood glucose level is the normal course. This is probably the main explanation for the absence of improvement in overall glycaemic control when compared with regular human insulin. A tendency to a reduction in hypoglycaemic events during treatment with fast-acting analogues has been observed in most studies. Recent studies have indicated that NPH insulin administered several times daily at mealtimes can improve glycaemic control without increasing the risk of hypoglycaemia. The fast-acting analogues are now also available as insulin mixed with NPH. Insulin glargine is a new long-acting insulin which is soluble and precipitates after injection, resulting in a long half-life with a residual activity of about 50% 24,h after injection. Insulin glargine is a peakless insulin and studies in both type 1 and type 2 diabetic patients indicate that glargine improves fasting blood glucose control and reduces the incidence of nocturnal hypoglycaemia. Surprisingly, the new fast,acting analogues have not achieved the expected commercial success, which emphasises the need for new strategies for basal insulin supplementation, exercise, diet and blood glucose monitoring. Copyright © 2002 John Wiley & Sons, Ltd. [source] 3352: The effects of high altitude on central corneal thicknessACTA OPHTHALMOLOGICA, Issue 2010H BASMAK Purpose A large number of people are exposed to long-term hypobaric hypoxic conditions via mountaineering, skiing and trekking. Other people such as aviators and high-altitude parachutists are exposed to short-term hypobaric hypoxic conditions. It is known that hypobaric conditions alter physiological and morphological status of the eye including the central corneal thickness (CCT). Our aim is to review the results of the influences of high altitude on CCT. We will also add our experience on the influences of short-term hypobaric hypoxia on CCT. Methods Reports covering this topic will be discussed. The possible mechanisms for the alterations in CCT will be included. Hypobaric hypoxic conditions simulate high altitudinal environments, which was the basis of our study covering 70 eyes of 35 healthy men exposed to hypobaric hypoxic condition. We measured the CCT via ultrasound pachmetry at local ground (792 m above sea level) and then during short-term hypobaric hypoxic exposure (equivalent 9144 m above). Results CCT has been found to be increased at high altitudes. We also found that hypobaric hypoxic condition increased the CCT significantly. The mechanism of increased CCT is not clear, although the alterations in corneal endothelial cells function seem to be the main explanation. Systemic delivery of oxygen to the anterior chamber can possibly be an important contributing factor based on a recent study. Conclusion CCT has been reported to be increased at high altitude. The possible underlying mechanisms are altered endothelial function and metabolic activity. [source] The evolutionary ecology of senescenceFUNCTIONAL ECOLOGY, Issue 3 2008P. Monaghan Summary 1Research on senescence has largely focused on its underlying causes, and is concentrated on humans and relatively few model organisms in laboratory conditions. To understand the evolutionary ecology of senescence, research on a broader taxonomic range is needed, incorporating field, and, where possible, longitudinal studies. 2Senescence is generally considered to involve progressive deterioration in performance, and it is important to distinguish this from other age-related phenotypic changes. We outline and discuss the main explanations of why selection has not eliminated senescence, and summarise the principal mechanisms thought to be involved. 3The main focus of research on senescence is on age-related changes in mortality risk. However, evolutionary biologists focus on fitness, of which survival is only one component. To understand the selective pressures shaping senescence patterns, more attention needs to be devoted to age-related changes in fecundity. 4Both genetic and environmental factors influence the rate of senescence. However, a much clearer distinction needs to be drawn between life span and senescence rate, and between factors that alter the overall risk of death, and factors that alter the rate of senescence. This is particularly important when considering the potential reversibility and plasticity of senescence, and environmental effects, such as circumstances early in life. 5There is a need to reconcile the different approaches to studying senescence, and to integrate theories to explain the evolution of senescence with other evolutionary theories such as sexual and kin selection. [source] Release from foliar and floral fungal pathogen species does not explain the geographic spread of naturalized North American plants in EuropeJOURNAL OF ECOLOGY, Issue 3 2009Mark Van Kleunen Summary 1During the last centuries many alien species have established and spread in new regions, where some of them cause large ecological and economic problems. As one of the main explanations of the spread of alien species, the enemy-release hypothesis is widely accepted and frequently serves as justification for biological control. 2We used a global fungus,plant host distribution data set for 140 North American plant species naturalized in Europe to test whether alien plants are generally released from foliar and floral pathogens, whether they are mainly released from pathogens that are rare in the native range, and whether geographic spread of the North American plant species in Europe is associated with release from fungal pathogens. 3We show that the 140 North American plant species naturalized in Europe were released from 58% of their foliar and floral fungal pathogen species. However, when we also consider fungal pathogens of the native North American host range that in Europe so far have only been reported on other plant species, the estimated release is reduced to 10.3%. Moreover, in Europe North American plants have mainly escaped their rare, pathogens, of which the impact is restricted to few populations. Most importantly and directly opposing the enemy-release hypothesis, geographic spread of the alien plants in Europe was negatively associated with their release from fungal pathogens. 4Synthesis. North American plants may have escaped particular fungal species that control them in their native range, but based on total loads of fungal species, release from foliar and floral fungal pathogens does not explain the geographic spread of North American plant species in Europe. To test whether enemy release is the major driver of plant invasiveness, we urgently require more studies comparing release of invasive and non-invasive alien species from enemies of different guilds, and studies that assess the actual impact of the enemies. [source] | |||||||||||||