Thursday, June 28, 2012
Wednesday, June 27, 2012
Snacking on Raisins Significantly Reduces Overall Post-Meal Blood Sugar Levels
New research debuted at the American Diabetes Association’s 72nd Annual Scientific Session suggests eating raisins three times a day may significantly lower postprandial (post-meal) glucose levels when compared to common alternative snacks of equal caloric value.
Raisins have a relatively low glycemic index and contain fiber and antioxidants.
The study was conducted at the Louisville Metabolic and Atherosclerosis Center (L-MARC) by lead researcher, Harold Bays, MD, medical director and president of L-MARC.
The study was conducted among 46 men and women who had not previously been diagnosed with diabetes mellitus, but who had mild elevations in glucose levels. Participants were randomly assigned to snack on raisins or pre-packaged commercial snacks that did not contain raisins or other fruits or vegetables, three times a day for 12 weeks. Findings included:
- Compared to control snacks, raisins significantly decreased mean post-meal glucose levels by 16 percent
- Compared to baseline within group paired analysis, raisins significantly reduced mean hemoglobin A1c by 0.12 percent
- Consumption of the control snacks in the study did not significantly reduce mean post-meal glucose or hemoglobin A1c
“Compared to the snacking control group, the group consuming raisins had a significant statistical reduction in their after-liquid meal blood sugar levels among study participants who had mean baseline fasting glucose levels between 90 and 100 mg/dl.,” said Dr. Bays. “This favorable glucose effect of raisins was further supported by the statistically significant reduction in hemoglobin A1c (a standard test for overall blood sugar control in diabetes mellitus) in the within group comparison to baseline. The within group comparisons from baseline with snacks did not demonstrate a reduction in hemoglobin A1c.”
VIDEO: Raisins and glucose a randomized controlled trial
The study was funded by the California Raisin Marketing Board through a grant to the L-MARC Research Center in Louisville, Kentucky.
“Raisins have a relatively low glycemic index and contain fiber and antioxidants, all factors which contribute to blood sugar control,” said James Painter, Ph.D., R.D., and nutrition research advisor for the California Raisin Marketing Board. “Decreasing blood sugar and maintaining normal hemoglobin A1c levels is important because it can prevent long-term damage to the heart and circulatory system.”
This research is part of a two-part study by L-MARC that looked at raisins and possible impacts to blood pressure and blood sugar levels. The first part of the study announced at the American College of Cardiology’s 61st Annual Scientific Session suggests eating raisins three times a day may significantly lower blood pressure among individuals with slightly higher than normal blood pressure, otherwise known as prehypertension.
Visit www.loveyourraisins.com for further information and summaries of California Raisins’ nutrition research.
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Courtesy MultiVu
Researchers develop new method for analyzing cell function
BioImageXD is a free open-source multi-purpose post-processing tool for bioimaging. The software can be used for simple visualization of multi-channel temporal image stacks to complex 3D rendering of multiple channels at once. Animations of 3D renderings can be created using flying paths or keyframes.
The work to develop the software has been funded by the Academy of Finland (through the FinNano Research Programme), the European Union and Tekes – the Finnish Funding Agency for Technology and Innovation. Version 1.0 of BioImageXD has been accepted for publication in Nature Methods, the top journal in the field.
Among other things, the BioImageXD software is a tool for analysing how molecules move on cell surfaces and how they bond together. With the software, scientists can analyse the composition of cell surfaces, study how cancer cells spread in a three-dimensional environment, or measure how effectively viruses and targeted drugs enter cells. Such calculations have not been possible before.
In recent years, cell and tissue imaging with new, specialised microscopes has considerably advanced research in bioscience and biomedicine. The new methods also allow for studies on living cells. However, the microscopic images are not displayable as such and need to be rendered into three-dimensional models. These 3D renderings carry significant weight as evidence already by themselves, but reliable scientific data also requires numerical values, which can then be used in mathematical calculations. In addition, these calculations must be feasible with extremely large datasets.
So far, the lack of suitable software has clogged up this development. To solve the problem, researchers in Turku, Jyväskylä and Dresden drew up precise specifications for software for processing of imaging data. A key criterion was that the software would be based on the principles of open source, freely available to all researchers.
The work resulted in BioImageXD, a software program that thanks to its versatile and open-source nature has received much positive feedback from hundreds of researchers around the world.
From extensive development to test success
One of the unique features of BioImageXD is that it can be used to create completely new analysis methods (and users do not even need programming skills), process thousands of images at the same time and analyse millions of molecules. Comparison tests have shown that BioImageXD is faster and more sensitive than other similar programs.
The development of the BioImageXD software began ten years ago in a University of Jyväskylä research team led by Jyrki Heino. Since then, the work has continued through active collaboration between Heino’s team, Varpu Marjomäki’s team and Daniel White from Max Planck Institute of Molecular Cell Biology and Genetics.
The main development has been led by Pasi Kankaanpää, who now works at Turku Centre for Biotechnology as Coordinator of the Cell Imaging Core.
The BioImageXD software will be featured in a special issue of Nature Methods, focusing on the processing of biomedical images.
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Courtesy Academy of Finland
For model images and videos on the BioImageXD software, and its use in visualising intracellular molecules, for instance, please contact Pasi Kankaanpää.
More information:
- Coordinator Pasi Kankaanpää (University of Turku), tel. +358 40 522 1090, pkanka@utu.fi
- Professor Jyrki Heino (University of Turku), tel. +358 50 523 8351,jyrki.heino@utu.fi
- Adjunct Professor Varpu Marjomäki (University of Jyväskylä), tel. +358 40 563 4422, varpu.s.marjomaki@jyu.fi
Article: P. Kankaanpää, L. Paavolainen, S. Tiitta, M. Karjalainen, J. Päivärinne, J. Nieminen, V. Marjomäki, J. Heino and D. White (2012). “BioImageXD: an open, general-purpose and high-throughput image-processing platform”. Nature Methods 9: 683-689.
Biologists reveal potential ‘fatal flaw’ in iconic sexual selection study
A classic study from more than 60 years ago suggesting that males are more promiscuous and females more choosy in selecting mates may, in fact, be wrong, say life scientists who are the first to repeat the historical experiment using the same methods as the original.
In 1948, English geneticist Angus John Bateman published a study showing that male fruit flies gain an evolutionary advantage from having multiple mates, while their female counterparts do not. Bateman’s conclusions have informed and influenced an entire sub-field of evolutionary biology for decades.
“Bateman’s 1948 study is the most-cited experimental paper in sexual selection today because of its conclusions about how the number of mates influences fitness in males and females,” said Patricia Adair Gowaty, a distinguished professor of ecology and evolutionary biology at UCLA. “Yet despite its important status, the experiment has never been repeated with the methods that Bateman himself used initially, until now.
“Our team repeated Bateman’s experiment and found that what some accepted as bedrock may actually be quicksand. It is possible that Bateman’s paper should never have been published.”
Gowaty’s study was published June 11 in the online edition of Proceedings of the National Academy of Sciences and is scheduled for publication in an upcoming print edition.
The original experiment on Drosophila melanogaster, also known as the common fruit fly, was performed by creating multiple, isolated populations with either five males and five females or three of each gender in a jar. The insects mated freely in the experimental populations, and Bateman examined the children that made it to adulthood. To count the number of adult offspring engendered by each of his original insect subjects, Bateman needed a reliable way to match parents with children.
Nowadays, modern geneticists would use molecular evidence to determine the genetic parentage of each child, but DNA analysis was not available in the 1940s. Instead, Bateman chose his initial specimens carefully, selectingD. melanogaster flies that each had a unique, visible mutation that could be transferred from parent to child, Gowaty said.
The mutations were extreme. Some of the flies had curly wings, others thick bristles, and still others had eyes reduced in size to narrow slits. The outward differences in each breeding subject allowed Bateman to work backward to determine the parentage of some of the fly progeny and to document each mating pair among the original insects. A child with curly wings and thick bristles, for example, could only have come from one possible pairing.
Yet Bateman’s method, which was cutting-edge for its time, had a “fatal flaw,” according to Gowaty.
Imagine the child of a curly-winged mother and an eyeless father. The child has an equal chance of having both mutations, only the father’s mutation, only the mother’s mutation or no mutation at all. In order to know who mated with whom, Bateman used only the children with two mutations, because these were the only ones for which he could specifically identify both the mother and father. But by counting only the children with two mutations, Bateman probably got a skewed sample, Gowaty said. In repeating Bateman’s experiment, she and her colleagues found that the flies with two severe mutations are less likely to survive into adulthood.
Flies use their wings not only to hover but also to sing during courtship, which is why curly wings present a huge disadvantage. Specimens with deformed eyes might have an even tougher time surviving. The 25 percent of children born with both mutations were even more likely to die before being counted by Bateman or Gowaty.
“It’s not surprising that the kids died like flies when they got one dramatic mutation from mom and another dramatic mutation from dad,” she said.
Gowaty found that the fraction of double-mutant offspring was significantly below the expected 25 percent, which means Bateman would have been unable to accurately quantify the number of mates for each adult subject. Further, his methodology resulted in more offspring being assigned to fathers than mothers, something that is impossible when each child must have both a father and a mother, Gowaty said.
Bateman concluded that male fruit flies produce many more viable offspring when they have multiple mates but that females produce the same number of adult children whether they have one mate or many. But Gowaty and her colleagues, by performing the same experiment, found that the data were decidedly inconclusive.
In their repetition — and possibly in Bateman’s original study — the data failed to match a fundamental assumption of genetic parentage assignments. Specifically, the markers used to identify individual subjects were influencing the parameters being measured (the number of mates and the number of offspring). When offspring die from inherited marker mutations, the results become biased, indicating that the method is unable to reliably address the relationship between the number of mates and the number of offspring, said Gowaty. Nonetheless, Bateman’s figures are featured in numerous biology textbooks, and the paper has been cited in nearly 2,000 other scientific studies.
“Here was a classic paper that has been read by legions of graduate students, any one of whom is competent enough to see this error,” Gowaty said. “Bateman’s results were believed so wholeheartedly that the paper characterized what is and isn’t worth investigating in the biology of female behavior.”
Repeating key studies is a tenet of science, which is why Bateman’s methodology should have been retried as soon as it became important in the 1970s, she said. Those who blindly accept that females are choosy while males are promiscuous might be missing a big piece of the puzzle.
“Our worldviews constrain our imaginations,” Gowaty said. “For some people, Bateman’s result was so comforting that it wasn’t worth challenging. I think people just accepted it.”
Shaking the foundation
Biologists studying sexual selection examine mating habits of organisms ranging from fruit flies to gorillas, both in the lab and in the wild, in order to better understand how certain traits or behaviors confer evolutionary advantages.
Sexual selection began as a discipline following Charles Darwin’s publication of “The Descent of Man, and Selection in Relation to Sex,” considered Darwin’s defense against critics of his theory of evolution through natural selection. He argued that while the unwieldy, colorful tails of peacocks hindered flight and made males easy targets for hungry tigers, the flamboyant plumage served a vital role in attracting potential mates. The overdressed birds had an unexpected evolutionary advantage that did not help when it came to escaping predators but did help when it came to producing offspring through sexual selection, said Gowaty.
Darwin, and later Bateman, cleaved to the notion that females of a species tended to be discriminating and passive while the far more promiscuous males competed for their attention. In the last few decades, however, evolutionary biologists have shown that the story is far more complicated. Gowaty, who has been interested in female mating habits in insects and birds since the beginning of her career, spent 30 years in the field studying Eastern bluebirds. She published the first molecular genetics study showing that females in a socially monogamous species mated outside their traditional pairs regularly.
Gowaty describes the benefits of multiple mates as an answer to the never-ending evolutionary struggle against what may be the world’s greatest predator: disease.
“Our pathogens have much shorter generation times than we do as the hosts, and they evolve offences much more rapidly than we can evolve defences,” she said. “One of the rules of nature is that our pathogens are going to get us.”
In this illness-driven arms race, organisms that produce offspring from multiple mates are more likely to produce some children with the right antibodies to survive the next generation of viruses, bacteria and parasites. Fruit fly males are likely to give females the additional variation in the genome that they need to build strong immune systems in their kids, Gowaty said.
For Gowaty, many open questions are remaining when it comes to female mating habits, whether in fruit flies or other organisms. Yet shaking the bedrock of the Bateman paradigm may help the field examine new perspectives.
“Paradigms are like glue, they constrain what you can see,” she said. “It’s like being stuck in sludge — it’s hard to lift your foot out and take a step in a new direction.”
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This study was federally funded by the National Science Foundation. Other co-authors included Wyatt Anderson, a professor of genetics at the University of Georgia and a member of the National Academy of Sciences, and Yong-Kyu Kim, a research scientist at Emory University.
Francois Gerome's (French painter) Paintings
Francois Gerome was a French painter born in Paris in 1895. He is best known for his paintings of women depicted at picturesque spots throughout Paris including the Place de la Concorde and in front of the Opéra. In these representations, the women usually engage the viewer with their frontal pose and direct gaze outward. Gerome used oils, typically on canvas or on board.
Gerome typically signed his paintings with his first initial and last name.
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