Brain Responses to Violet, Blue, and Green Monochromatic Light Exposures in Humans: Prominent Role of Blue Light and the Brainstem

BACKGROUND: Relatively long duration retinal light exposure elicits nonvisual responses in humans, including modulation of alertness and cognition. These responses are thought to be mediated in part by melanopsin-expressing retinal ganglion cells which are more sensitive to blue light than violet or green light. The contribution of the melanopsin system and the brain mechanisms involved in the establishment of such responses to light remain to be established. METHODOLOGY/PRINCIPAL FINDINGS: We exposed 15 participants to short duration (50 s) monochromatic violet (430 nm), blue (473 nm), and green (527 nm) light exposures of equal photon flux (10(13)ph/cm(2)/s) while they were performing a working memory task in fMRI. At light onset, blue light, as compared to green light, increased activity in the left hippocampus, left thalamus, and right amygdala. During the task, blue light, as compared to violet light, increased activity in the left middle frontal gyrus, left thalamus and a bilateral area of the brainstem consistent with activation of the locus coeruleus. CONCLUSION/SIGNIFICANCE: These results support a prominent contribution of melanopsin-expressing retinal ganglion cells to brain responses to light within the very first seconds of an exposure. The results also demonstrate the implication of the brainstem in mediating these responses in humans and speak for a broad involvement of light in the regulation of brain function

Unit Nonresponse in a Population-Based Study of Prostate Cancer

Low unit response rates can increase bias and compromise study validity. Response rates have continued to fall over the past decade despite all efforts to increase participation. Many factors have been linked to reduced response, yet relatively few studies have employed multivariate approaches to identify characteristics that differentiate respondents from nonrespondents since it is hard to collect information on the latter. We aimed to assess factors contributing to enrollment of prostate cancer (PCa) patients. We combined data from the North Carolina-Louisiana (LA) PCa Project's LA cohort, with additional sources such as US census tract and LA tumor registry data. We included specific analyses focusing on blacks, a group often identified as hard to enroll in health-related research. The ability to study the effect of Hurricane Katrina, which occurred amidst enrollment, as a potential determinant of nonresponse makes our study unique. Older age (≥ 70) for blacks (OR 0.65) and study phase with respect to Hurricane Katrina for both races (OR 0.59 for blacks, OR 0.48 for whites) were significant predictors of participation with lower odds. Neighborhood poverty for whites (OR 1.53) also was a significant predictor of participation, but with higher odds. Among blacks, residence in Orleans parish was associated with lower odds of participation (OR 0.33) before Katrina. The opposite occurred in whites, with lower odds (OR 0.43) after Katrina. Our results overall underscore the importance of tailoring enrollment approaches to specific target population characteristics to confront the challenges posed by nonresponse. Our results also show that recruitment-related factors may change when outside forces bring major alterations to a population's environment and demographics

Comparative analysis of expressed sequence tags (ESTs) from Triticum monococcum shoot apical meristem at vegetative and reproductive stages

Triticum monococcum has recently drawn the attention of biologists to discover and utilize novel genes and alleles. To explore the molecular features of the genetic network governing floral transition in shoot apical meristem (SAM) of spring growth habit T. monococcum, two expressed sequence tag (EST) libraries containing 3,031 ESTs from vegetative SAM (VS) and 2,647 ESTs from early reproductive SAM (RS) were analyzed. Assembly of ESTs resulted in 2,303 unigenes for VS library (368 contigs and 1,935 singletons) and 1,890 unigenes (337 contigs and 1,553 singletons) for RS library. The 67.05 % of VS unigenes and 66.30 % of RS unigenes showed significant similarity with genes of known, putative and or unknown function, whereas the remaining 32.95 % of the VS unigenes and 33.7 % of RS unigenes displayed no significant match with the public protein database. The 1,064 and 866 unigenes of VS and RS libraries were assigned to functional categories using Pageman ontology tool. Further analysis revealed that the switch from VS to RS caused significant changes in the abundance of unigenes assigned to some functional categories. A total of 37 genes were identified which were significantly differentially expressed between vegetative and reproductive stages of T. monococcum SAM. Investigation of the differentially expressed genes revealed the importance of the genes involved in energy metabolism, ubiquitin/26S proteasome system, polyamines biosynthesis and signaling of reactive oxygen species in SAM differentiation towards floral transition in T. monococcum.Roohollah Shamloo-Dashtpagerdi, Hooman Razi, Angelica Lindlöf, Ali Niazi, Ali Dadkhodaie, Esmaeil Ebrahimi