Scientific Research and Developments
Learn about the scientific research and developments that I'm following.
Bad vibrations control insect pests
Effect of snacking on overall diet quality
Fluorescent lights and eye health
Treatment options for adults with amblyopia, a vision disorder
Bad vibrations control insect pests
Many species of insects attract mates by emitting species-specific chemicals called pheromones. If pheromone communication is interrupted, mating won't occur and insect populations will dwindle. For decades, scientists have exploited this fact and have used synthetic pheromones to disrupt the mating activities of many serious insect pests. Synthetic pheromones lure targeted insect pests into traps or cause them to become disoriented and unable to find mates.
But not all insect species use pheromones to find mates. Leafhoppers and planthoppers, numbering about 30,000 species, attract mates with vibrational signals that travel along the stems and leaves of plants. Some of these vibrational signallers are major insect pests that, to date, have only been controllable with insecticides.
Eriksson et al explored if disruption of insect vibrational signaling could thwart reproduction and effectively control leafhopper pests. Their target insect was Scaphoideus titanus, a leafhopper that carries the deadly Flavescence doree disease of grapevines.
The researchers disrupted the normal male-female signaling of the leafhoppers by introducing a pre-recorded signal from a rival male. The disruptive signal was applied through an MP3 driven electromagnetic shaker that was attached to the wire used to support a row of grapevines. The last vine on the wire was 940 cm (about 31 feet) from the signal source.
The disruptive signal significantly reduced mating success of S. titanus on all vines, including the vine that was farthest from the source, when compared with control vines. Over 80% of females on the treated vines were unmated, compared with about 20% on the control vines.
The results of this study show that disruptive signaling has the potential to be an effective and nontoxic way to control a leafhopper pest of grapevines.
Reference
Eriksson A, Anfora G, Lucchi A, Lanzo F, Virant-Doberlet M, Mazzoni V. Exploitation of insect vibrational signals reveals a new method of pest control. PLoS ONE. 2012;7(3):e32954.
Effect of snacking on overall diet quality
Americans are snacking more. From 1977 to 2006, the percentage of Americans who reported that they ate snacks outside of regular meals increased from 71% to 97%. The effect of this increased snacking on diet quality is not well understood. Several studies have linked snacking with higher energy and lower micronutrient intake. Because these studies examined individual micronutrients, interpreting their results in the context of overall diet quality is problematic.
In order to better gauge how snacking affects overall diet quality, Zizza and Xu evaluated diet survey results for 11,209 participants in the National Health and Nutrition Examination Surveys (NHANES) against the Healthy Eating Index-2005 (HEI-2005). The HEI-2005 is a measure of diet quality in conformance with the 2005 Dietary Guidelines for Americans. The HEI-2005 consists of 9 adequacy components (total fruit, whole fruit, total vegetables, dark green and orange vegetables and legumes, total grains, whole grains, milk, meat and beans, and oils) and 3 moderation components (saturated fat, sodium, and energy from solid fat, alcohol, and added sugars). The sum of the scores for all components can range from 0 to 100, with higher scores reflecting healthier diets. The NHANES participants were stratified to 5 categories of snacking - those who snacked 0, 1, 2, 3, or ≥4 times per day.
The authors found that snacking was not associated with poorer diet quality based upon the overall HEI-2005 scores. Evaluation of the HEI-2005 component scores revealed a positive association of snacking frequency with scores for fruit, whole grains, milk, oils, and sodium. The authors expected a positive association of snacking with fruit scores because fruit is easily consumed as a snack. The positive association of snacking and milk scores is consistent with earlier studies that found milk to be a frequent snack item. But the positive association of snacking and sodium scores contradicts earlier studies. The authors attribute the positive sodium scores to lower intake of vegetables and meat and beans. An earlier study found that intake of vegetables and meat and beans was associated with poorer sodium scores since sodium is often added to these foods during processing and preparation. There was an inverse relationship between snacking and the score for solid fat, alcohol, and added sugars, confirming earlier studies.
The authors noted several limitations of this study including the fact that the NHANES participants complete dietary recall interviews and may misreport their food intake. Also participants provided only 24 hours of dietary data so the data do not capture day-to-day variability in food intake.
The authors conclude that theirs is the first study to show a positive association between snacking and overall diet quality.
References
Zizza CA, Xu B. Snacking is associated with overall diet quality among adults. J Acad Nutr Diet. 2012;112(2):291-296.
Guenther PM, Reedy J, Krebs-Smith SM. Development of the Healthy Eating Index-2005. J Am Diet Assoc. 2008;108(11):1896-1901.
Fluorescent lights and eye health
Will the prevalence of eye disease increase because we're changing over to fluorescent lights to
slow climate change? That's the warning posited by Walls et al in a recent paper in the American
Journal of Public Health. There are several flaws in this paper which negate the authors'
prognostication.
The authors note that, to improve energy efficiency, US federal law requires the phase out of incandescent light bulbs by 2014. It's important to clarify that the new US lighting standards do not ban incandescent light bulbs but rather require that they be made about 25% more energy efficient. This energy efficiency already has been achieved with halogen incandescent bulbs. Alternatives to incandescent bulbs also have become available and more widely used. Compact fluorescent lights (CFLs) are a popular alternative because they are relatively low in cost and use 75% less energy than traditional incandescent bulbs.
The authors then express concern that exposure to fluorescent lights poses an ultraviolet (UV) radiation risk to people. They paint a backdrop of workers moving from fields and outdoor worksites into artificially lit office environments in our knowledge-based society. Oddly, they suggest that workers in offices have greater UV exposure than workers outdoors (and potentially exposed to sunlight) but provide no data to support this. They see increased UV exposure risk as fluorescent lights become more widely used in homes.
To highlight the differences in fluorescent lights, the authors include a table of fluorescent light color temperatures, expressed in Kelvin (K) units. Color temperatures range from 2700K to 8000K. The lower color temperatures are warmer and produce a yellowish light, and the higher ones are cooler and produce a bluish to white light. CFLs intended to replace the traditional soft white incandescent bulbs have a color temperature of 2700K. The cool white fluorescent tubes that have been widely used in offices for years have a color temperature of 4100K.
The authors are particularly concerned about fluorescent lights over 4000K. These lights, they claim, emit UV radiation that is hazardous to ocular tissues, although they provide no reference to support this. They predict an increased use of 4000K fluorescent lights as traditional incandescent bulbs are phased out. They view warmer CFLs (less than 3500K) as poor replacements for incandescent bulbs because these CFLs "…produce light that is generally not adequate for concentration at work…," another unsupported statement. In fact, a Popular Mechanics lab test found that people actually preferred the light from 2700K and 3500K CFLs over that from a traditional incandescent bulb.
The authors then describe their calculation of increased eye disease prevalence resulting from increased use of fluorescent lights. They base their calculation on a study by Lucas et al which estimated eye disease risk from sunlight exposure and a study by Lytle et al which estimated squamous cell carcinoma risk from unfiltered fluorescent light exposure. Walls et al conclude that increased use of fluorescent lighting may increase UV-related eye diseases by up to 12%.
Walls et al make dubious assumptions to conclude that increased use of fluorescent lights to mitigate climate change may increase eye disease.
References
Walls HL, Walls KL, Benke G.
Eye disease resulting from increased use of fluorescent lighting as a climate change mitigation strategy. Am J Public Health.
2011;101(12):
2222-2225.
Masamitsu E. The best compact fluorescent light bulbs: PM lab test. Popular Mechanics website. http://www.popularmechanics.com/home/reviews/news/4215199?series=15. Published May 2007. Accessed January 25, 2012.
Lucas RM, McMichael AJ, Armstrong BK, Smith WT. Estimating the global disease burden due to ultraviolet radiation exposure. Int J Epidemiol. 2008;37(3):654-667.
Lytle CD, Cyr WH, Beer JZ, et al. An estimation of squamous cell carcinoma risk from ultraviolet radiation emitted by fluorescent lamps. Photodermatol Photoimmunol Photomed. 1992;9(6):268-274.
Treatment options for adults with amblyopia, a vision disorder
When I was a teenager, I was excited to join a girls' softball team. First practice, I stepped up to the plate, waited for the pitch, saw the pitcher release the ball, swung … and missed. Next pitch, swung … and missed. Third pitch, swung … and missed. After several more at bats, each time with three swings and a strikeout, I was feeling lousy. Years later, I learned my ineptitude at softball stemmed from vision problems that persisted after being diagnosed with and treated for a disorder called amblyopia when I was 6 years old.
Amblyopia, or lazy eye, results from inadequate development of the brain's visual processing circuitry during childhood. A frequent cause of the disorder is a misalignment of the eyes. Misaligned eyes send 2 different images to the brain, which the brain resolves by suppressing the input from 1 eye. The visual processing circuitry for the suppressed eye will not develop normally, and that eye will have reduced vision that cannot be corrected with lenses. Suppression of vision in 1 eye also results in a loss of depth perception, or stereoblindness. It was stereoblindness that made it nearly impossible for me to hit a softball.
If caught early, vision loss from amblyopia can be minimized. Surgery may be required to correct misaligned eyes. To strengthen vision in the suppressed eye, vision to the good eye is blocked with a patch or by using drops. Even if treated early, some degree of diminished vision, particularly stereoblindness, may persist. About 2 to 4% of people have amblyopia in varying degrees of severity. Many people with amblyopia test normal or close to it on standard vision tests (reading those charts of letters), but have difficulty with tasks like driving or playing sports.
Until about 10 or 15 years ago, most physicians and scientists believed that treatment for amblyopia was ineffective after about age 7 because the brain's visual circuits were thought to be permanently hard-wired by then. Scientists now know that brain circuitry can be modified, and they use the term plasticity to describe this capacity. Since the late 1990s, studies have shown brain plasticity in adults with amblyopia who improved their vision with treatments such as perceptual learning, which involves the repeated practice of challenging visual tasks.
Even playing video games may help people with amblyopia. In a pilot study published in August 2011, Li et al found that teenagers and adults with amblyopia who played video games for 2 hours per day, for a total of 40 or 80 hours, improved their vision. Because this was a small, nonrandomized study, its findings must be interpreted with caution. The investigators have another study underway, An Active Approach to Treat Amblyopia: Perceptual Learning and Video Games, in which they are evaluating improvement in vision after structured sessions of perceptual learning and video-game play in people with amblyopia and normal vision.
Another treatment for amblyopia is vision therapy, an intensive visual training program done under the supervision of an optometrist. Dr. Susan R. Barry, a professor of neurobiology at Mount Holyoke College, is probably the best known adult with amblyopia to have undergone vision therapy. As a neurobiologist, she had believed that her amblyopia was untreatable but in midlife was encouraged by an optometrist to try vision therapy. Her vision therapy was a success and, in her late forties, she acquired stereovision. Barry tells her fascinating story in the book, Fixing My Gaze.
Clinical studies and Sue Barry's experience have shown that adults with amblyopia can improve their vision with the proper treatment. This bodes well for effective treatments to become more widely available for people with amblyopia in the future.
References
Levi DM, Li RW. Perceptual learning as a potential treatment for amblyopia: a mini-review. Vision Res. 2009;49(21):2535-2549.
Li RW, Ngo C, Nguyen J, Levi DM. Video-game play induces plasticity in the visual system of adults with amblyopia. PLoS Biol. 2011;9(8):e1001135.
Barry SR. Fixing My Gaze: A Scientist's Journey Into Seeing in Three Dimensions. New York, NY: Perseus Books Group; 2009.