Improved Performance of Transgenic Fructan-Accumulating Tobacco under Drought Stress.

Fructans are polyfructose molecules produced by approximately 15% of the flowering plant species. It is possible that, in addition to being a storage carbohydrate, fructans have other physiological roles. Owing to their solubility they may help plants survive periods of osmotic stress induced by drought or cold. To investigate the possible functional significance of fructans, use was made of transgenic tobacco (Nicotiana tabacum) plants that accumulate bacterial fructans and hence possess an extra sink for carbohydrate. Biomass production was analyzed during drought stress with the use of lines differing only in the presence of fructans. Fructan-producing tobacco plants performed significantly better under polyethylene-glycol-mediated drought stress than wild-type tobacco. The growth rate of the transgenic plants was significantly higher (+55%), as were fresh weight (+33%) and dry weight (+59%) yields. The difference in weight was observed in all organs and was particularly pronounced in roots. Under unstressed control conditions the presence of fructans had no significant effect on growth rate and yield. Under all conditions the total nonstructural carbohydrate content was higher in the transgenic plants. We conclude that the introduction of fructans in this non-fructan-producing species mediates enhanced resistance to drought stress

Cost effectiveness of national hepatitis B vaccination: interim report

In the Netherlands vaccination against hepatitis B has up to now targeted risk groups such as homosexual men, prostitutes, injecting drug users and persons working in the medical professions. At present, there is a discussion going on about whether to introduce hepatitis B vaccination into the national immunisation programme, as advised by the WHO in 1992. The RIVM has been asked to support decision makers by providing a cost-effectiveness analysis of such a programme, based on current knowledge of the epidemiology of hepatitis B infection and the consequent health-care costs. We collected information on hepatitis B epidemiology from various sources, ranging from notification data to preliminary results of an ongoing case-control study on hepatitis B transmission. After consulting on the prevalence of HBV carriers in the various risk groups and the impact of demographic factors, such as immigration of carriers from highly endemic regions, we simulated hepatitis B infection in an age-structured population with a dynamic transmission model. We also investigated the effects of universal vaccination using this model. The incidences computed by the model were then used as a basis for a cost-effectiveness analysis that resulted in estimates for the costs per life year gained. One of the major conclusions was that circulation of the virus is kept up only within small risk groups; therefore the prevalence of HBV carriage in the Netherlands is mainly determined by immigration of carriers. As a consequence, the effects of national vaccination on the prevalence of HBV will be marginal and the cost per life year gained high. However, our estimates on the cost per life year gained depend heavily on future costs of vaccination and on discounting of future effects. When future effects are not discounted, a national vaccination campaign will be more cost-effective.In Nederland wordt momenteel overwogen om alle pasgeborenen tegen hepatitis B in te enten. Het RIVM heeft een onderzoek verricht waarin de kosten en effecten van vaccinatie van pasgeborenen vergeleken wordt met het huidige beleid. Dit is gericht op het vaccineren van risicogroepen, zoals homoseksuele mannen en medewerkers in de gezondheidszorg, en op het screenen van zwangeren. Een van de belangrijkste conclusies van het onderzoek is dat het aantal dragers van het virus in Nederland vooral door immigratie van dragers uit het buitenland bepaald wordt. Na invoering van algemene vaccinatie zal het aantal dragers van het virus in Nederland voorlopig niet erg sterk afnemen. De kosten per gewonnen levensjaar van algemene vaccinatie zijn relatief hoog in vergelijking met andere preventieve gezondheidszorgvoorzieningen. Als de kosten van het vaccin in de toekomst echter gaan dalen zal de kosten-effectiviteit van algemene vaccinatie gunstiger worden

Cost effectiveness of national hepatitis B vaccination: interim report

In Nederland wordt momenteel overwogen om alle pasgeborenen tegen hepatitis B in te enten. Het RIVM heeft een onderzoek verricht waarin de kosten en effecten van vaccinatie van pasgeborenen vergeleken wordt met het huidige beleid. Dit is gericht op het vaccineren van risicogroepen, zoals homoseksuele mannen en medewerkers in de gezondheidszorg, en op het screenen van zwangeren. Een van de belangrijkste conclusies van het onderzoek is dat het aantal dragers van het virus in Nederland vooral door immigratie van dragers uit het buitenland bepaald wordt. Na invoering van algemene vaccinatie zal het aantal dragers van het virus in Nederland voorlopig niet erg sterk afnemen. De kosten per gewonnen levensjaar van algemene vaccinatie zijn relatief hoog in vergelijking met andere preventieve gezondheidszorgvoorzieningen. Als de kosten van het vaccin in de toekomst echter gaan dalen zal de kosten-effectiviteit van algemene vaccinatie gunstiger worden.In the Netherlands vaccination against hepatitis B has up to now targeted risk groups such as homosexual men, prostitutes, injecting drug users and persons working in the medical professions. At present, there is a discussion going on about whether to introduce hepatitis B vaccination into the national immunisation programme, as advised by the WHO in 1992. The RIVM has been asked to support decision makers by providing a cost-effectiveness analysis of such a programme, based on current knowledge of the epidemiology of hepatitis B infection and the consequent health-care costs. We collected information on hepatitis B epidemiology from various sources, ranging from notification data to preliminary results of an ongoing case-control study on hepatitis B transmission. After consulting on the prevalence of HBV carriers in the various risk groups and the impact of demographic factors, such as immigration of carriers from highly endemic regions, we simulated hepatitis B infection in an age-structured population with a dynamic transmission model. We also investigated the effects of universal vaccination using this model. The incidences computed by the model were then used as a basis for a cost-effectiveness analysis that resulted in estimates for the costs per life year gained. One of the major conclusions was that circulation of the virus is kept up only within small risk groups; therefore the prevalence of HBV carriage in the Netherlands is mainly determined by immigration of carriers. As a consequence, the effects of national vaccination on the prevalence of HBV will be marginal and the cost per life year gained high. However, our estimates on the cost per life year gained depend heavily on future costs of vaccination and on discounting of future effects. When future effects are not discounted, a national vaccination campaign will be more cost-effective.VW

Performance Characteristics of Long-Track Speed Skaters: A Literature Review

Speed skating is an intriguing sport to study from different perspectives due to the peculiar way of motion and the multiple determinants for performance. This review aimed to identify what is known on (long-track) speed skating, and which individual characteristics determine speed skating performance. A total of 49 studies were included. Based on a multidimensional performance model, person-related performance characteristics were categorized in anthropometrical, technical, physiological, tactical, and psychological characteristics. Literature was found on anthropometry, technique, physiology, and tactics. However, psychological studies were clearly under-represented. In particular, the role of self-regulation might deserve more attention to further understand mechanisms relevant for optimal performance and for instance pacing. Another remarkable finding was that the technically/biomechanically favourable crouched skating technique (i.e. small knee and trunk angle) leads to a physiological disadvantage: a smaller knee angle may increase the deoxygenation of the working muscles. This is an important underlying aspect for the pacing tactics in speed skating. Elite speed skaters need to find the optimal balance between obtaining a fast start and preventing negative technical adaptations later on in the race by distributing their available energy over the race in an optimal way. More research is required to gain more insight into how this impacts on the processes of fatigue and coordination during speed skating races. This can lead to a better understanding on how elite speed skaters can maintain the optimal technical characteristics throughout the entire race, and how they can adapt their pacing to optimize all identified aspects that determine performance