Press releases – July 2017

 

Jul 20 2017
15:01

SMART study reveals changes in brain metabolism

How physical exercise prevents dementia

FRANKFURT.Numerous studies have shown that physical exercise seems beneficial in the prevention of cognitive impairment and dementia in old age. Now researchers at Goethe University Frankfurt have explored in one of the first studies worldwide how exercise affects brain metabolism.

In order to further advance current state of knowledge on the positive influence of physical activity on the brain, gerontologists and sports physicians at Goethe University Frankfurt have examined the effects of regular exercise on brain metabolism and memory of 60 participants aged between 65 and 85 in a randomised controlled trial. Their conclusion: regular physical exercise not only enhances fitness but also has a positive impact on brain metabolism.

As the researchers report in the current issue of the medical journal “Translational Psychiatry”, they thoroughly examined all the participants in the SMART study (Sport and Metabolism in Older Persons, an MRT Study) by assessing movement-related parameters, cardiopulmonary fitness and cognitive performance. In addition, magnetic resonance tomography (MRT) and magnetic resonance spectroscopy (MRS) were used to measure brain metabolism and brain structure. Following this examination, the participants mounted an exercise bike three times a week over a period of 12 weeks. The 30-minute training sessions were individually adapted to each participant’s performance level. The participants were examined again after the end of the programme in order to document the effects of this physical activity on brain metabolism, cognitive performance and brain structure. The researchers also investigated to what extent exercise had led to an improvement in the participants’ physical fitness. The study was conducted by the Gerontology Department of the Institute of General Medicine (headed by Professor Johannes Pantel) and the Department of Sports Medicine (led by Professor Winfried Banzer).

As expected, physical activity had influenced brain metabolism: it prevented an increase in choline. The concentration of this metabolite often rises as a result of the increased loss of nerve cells, which typically occurs in the case of Alzheimer’s disease. Physical exercise led to stable cerebral choline concentrations in the training group, whereas choline levels increased in the control group. The participants’ physical fitness also improved: they showed increased cardiac efficiency after the training period. Overall, these findings suggest that physical exercise not only improves physical fitness but also protects cells.

The study was sponsored by the Else Kröner-Fresenius Foundation, the Cronstetten Foundation and the Schambach Family Foundation.

 

Publication: S Matura, J Fleckenstein, R Deichmann, T Engeroff, E Füzéki, E Hattingen, R Hellweg, B Lienerth, U Pilatus, S Schwarz, V A Tesky, L Vogt, W Banzer, J Pantel (2017) Effects of aerobic exercise on brain metabolism and grey matter volume in older adults: results of the randomised controlled SMART trial. Translational Psychiatry; doi:10.1038/tp.2017.135;
online: http://www.nature.com/tp/journal/v7/n7/full/tp2017135a.html

Further information: Dr. Dipl.-Psych. Silke Matura, Clinic for Psychiatry, Psychotherapy and Psychosomatics, Faculty of Medicine, Niederrad Campus, Tel.: +49(0)69-6301-84501, Silke.Matura@kgu.de

Dr.Johannes Fleckenstein, Preventive and Rehabilitative Sports Medicine, Faculty of Medicine, Ginnheim Campus, Tel.: +49(0)69-6301-24484; johannes.fleckenstein@sport.uni-frankfurt.de.

Goethe University is a research-oriented university in the European financial centre Frankfurt The university was founded in 1914 through private funding, primarily from Jewish sponsors, and has since produced pioneering achievements in the areas of social sciences, sociology and economics, medicine, quantum physics, brain research, and labour law. It gained a unique level of autonomy on 1 January 2008 by returning to its historic roots as a "foundation university". Today, it is among the top ten in external funding and among the top three largest universities in Germany, with three clusters of excellence in medicine, life sciences and the humanities. Together with the Technical University of Darmstadt and the University of Mainz, it acts as a partner of the inter-state strategic Rhine-Main University Alliance.

Current news about science, teaching, and society in GOETHE-UNI online (www.aktuelles.uni-frankfurt.de)

Publisher: The President of Goethe University

Editor: Dr. Anke Sauter, Science Editor, International Communication, Tel: +49(0)69 798-12477, Fax +49(0)69 798-761 12531, sauter@pvw.uni-frankfurt.de

Internet: www.uni-frankfurt.de

 

 

 

Jul 19 2017
11:59

A group of scientists has put together the puzzle pieces of a riboswitch-based regulatory process in the bacterium Bacillus subtilis

Pause to read the traffic sign: regulation of DNA transcription in bacteria

The survival of the cell is - apart from other important aspects - a question of timing: Scientists of Goethe University together with colleagues from other universities have now identified the different parts of this mechanism and introduced a model of the process.

One of the central tenets of biology is that information flows from DNA to RNA in order to encode proteins, which function in the cell. Arguably just as critical as the genetic code is the timing of this information flow. By producing the right RNA and right proteins at the right time, a cell can effectively strategize its survival and success. One such regulatory element, the riboswitch, has excited interest as a potential target for antibiotics. After over 10 years of research, Prof. Harald Schwalbe's research group at the Goethe University, in collaboration with the Landick group at the University of Wisconsin, Prof. Jens Wöhnert from Goethe-University’s Biology Department and the Süß group at the Technische Universität Darmstadt, has put together the puzzle pieces of a riboswitch-based regulatory process in the bacterium Bacillus subtilis, presenting the most extensive model of the timing of riboswitch action to date.

A riboswitch is a short piece of RNA that can fold into different structures, depending on whether or not a small messenger molecule is binds to it. In transcriptional riboswitches, these different structures signal the nearby RNA polymerase to continue producing RNA or to stop. In their recent publication in ELife, the Schwalbe group and their collaborators released molecular structures of the xpt-pbuX riboswitch in the off-position after synthesis and in the on-position upon binding by the small messenger molecule guanine. They also demonstrated that this switch to the on-position takes a certain amount of time. This sets a certain requirement on this regulatory process.

As RNA polymerase flies along a DNA strand, producing the corresponding RNA, it reaches the code for the xpt-pbuX switch, makes the riboswitch, and continues on. If guanine is not around, the RNA polymerase would detect the default off-position and halt synthesis. However, if guanine were to bind the riboswitch, the riboswitch would need to refold into the on-position, and RNA polymerase would have to wait long enough to detect the new conformation. Otherwise, it would always read "off", and that gene would never be read. Schwalbe and coworkers found that just such a pause does exist, and it's encoded into the DNA. After producing the xpt-pbuX switch, the RNA polymerase encounters this "pause site" on the DNA code and slows down, allowing the right amount of time for the riboswitch to refold.

This work provides the most in-depth kinetic model of riboswitch function to date and underscores the importance of pause sites in our understanding of riboswitches. As researchers consider using riboswitches as tools in synthetic biology applications, they will do well do keep the speed of the RNA polymerase in mind.

Publication: Steinert H, Sochor F, Wacker A, Buck J, Helmling C, Hiller F, Keyhani S, Noeske J, Grimm S, Rudolph MM, Keller H, Mooney RA, Landick R, Suess B, Fürtig B, Wöhnert J, Schwalbe H.; Pausing guides RNA folding to populate transiently stable RNA structures for riboswitch-based transcription regulation.; Elife; 2017; doi: 10.7554/eLife.21297.

 

Further Information: Prof. Dr. Harald Schwalbe, Institute for Organic Chemistry, email: schwalbe@nmr.uni-frankfurt.de.

 

Jul 12 2017
13:21

Machos are only welcome when female mosquitofish are in a group

Female fish prefer averagely active lovers

FRANKFURT.In evolution, a high sex drive does not always pay off. Female mosquitofish swim away from over-impetuous lovers because they leave them hardly any time to feed and also tend to injure their genitalia more often.

In some species, males invest virtually nothing in their offspring apart from sperm. So far, biologists believed that the most sexually active males in such species had an evolutionary advantage. But the ‘more mating, more offspring’ equation does not always hold in the case of the eastern mosquitofish (a small, livebearing freshwater fish) because the females also have a say, as behavioural researchers at Goethe University Frankfurt have now discovered.

“The starting point for our studies was the question why males in some animal species differ pronouncedly and consistently in their sexual activity levels even when they are exposed to identical environmental conditions and don’t need to compete”, explains Carolin Sommer-Trembo, who is dealing with the topic in her doctoral thesis. “We wanted to know how this variation in male behavioural types is maintained, although selection ought to oust males which display low or average levels of sexual activity.”

She chose the small and inconspicuous mosquitofish (Gambusia holbrooki) as a study object because they have sex and give birth to live offspring. Males have a penis-like mating organ on their underside which is long in comparison to their overall body size. To copulate, they swim up to the female from underneath in order to remain undiscovered for as long as possible.

To find out which males are interesting for female mosquitofish and whether the level of male sexual activity plays any role at all in their choice of partner, Carolin Sommer-Trembo and her colleagues Dr. David Bierbach (Leibniz Institute of Freshwater Ecology and Inland Fisheries, Berlin) and Professor Martin Plath (Northwest A&F University, Yangling) let females choose between males which displayed different levels of sexual activity. To exclude the possibility that specific males were chosen because of their appearance (morphology) or other behavioural characteristics and to control precisely the degree of sexual activity of the males, the researchers worked with computer-animated stimulus males which were presented to the females on monitors.

The result was that females preferred males which displayed a moderate level of sexual activity whilst they clearly avoided males with a greater sex drive. The researchers assume that this is due to cost-benefit considerations, since females who find themselves in the close vicinity of sexually very active males often not only suffer injuries to their genitalia but also scarcely have an opportunity to feed as they are constantly busy avoiding the males’ advances.

The situation is different when a group of females encounters a rampant male determined to mate. “Under natural conditions, female mosquitofish often form shoals to protect themselves from male harassment, just like other fish do to protect themselves from predators”, explains Carolin Sommer-Trembo. In the group, females showed far greater acceptance towards sexually very active males, since the cost-benefit ratio shifts under these circumstances.

The dependency of female choice on social context could explain why variation in male behavioural types is maintained amongst mosquitofish. And the experiments show that females include male sexual activity as a criterion in their choice of partner.

By the way: That swimming away from tempestuous lovers is a good idea when out on your own as a female mosquitofish does not appear to be instinctive but based on experience. When Sommer-Trembo conducted additional tests with virgin females, they were equally open to all types of male.

Publication:
Sommer-Trembo, C., Plath, M., Gismann, J., Helfrich, C. & Bierbach, D.
Context-dependent female mate choice maintains variation in male sexual activity.
Royal Society Open Science; DOI: 10.1098/rsos.170303
Online: http://rsos.royalsocietypublishing.org/content/4/7/170303

A picture with a Creative Commons licence can be downloaded under:
http://fishesofaustralia.net.au/images/image/GambusiaHolbrookiGSchmida.jpg 

The picture shows a female mosquitofish which is being pursued by a male in a typical manner. The male’s reproductive organ, what is referred to as the gonopod, is already extended and ready to “attack”. He swims up to the female from underneath in order to remain undiscovered for as long as possible.

Further information: Carolin Sommer Trembo, Institute of Ecology, Evolution and Diversity, Faculty of Biological Sciences, Riedberg Campus, Tel.: +49(0)69-798-42172, sommer-trembo@gmx.de.