Molecular processes involved in light detection
Contributed by: Robin Waterman @RobinWEcoEvo
Keywords
Animals, Experimental, Fundamental research, Historical figure, Lab, Medicine, North America, Physiological/organismal ecology, Sensory organs, Technology, Vision systems, Woman
Slides
Note: click the gear symbol to see notes that accompany the presentation
View and download in google slides here
Resources
Hubbard, Ruth, and Allen Kropf. “Molecular aspects of visual excitation.” Annals of the New York Academy of Sciences 81.2 (1959): 388-398. link
Notes
Slide 1: Researcher’s Background
Ruth Hubbard Wald was a biochemist studying light-sensitive molecules in invertebrate and vertebrate visual systems. She was the first woman to be tenured in Harvard’s biology department, an advocate for the advancement of women in the sciences, and a critic of biological determinism.
Biography in brief
Ruth Hubbard Wald was born in Vienna, Austria in 1924 as the daughter of two Jewish physicians. At the age of 14, she and her family immigrated to the US, fleeing Nazi occupation. Wald got her B.A. and Ph.D. in biology from Radcliffe College (now a division of Harvard University). She returned to Harvard in 1954 as a research fellow and worked her way up the male-dominated academic totem pole to become Professor of Biology in 1974. In close collaboration with fellow Harvard biologist and future husband George Wald, she conducted groundbreaking work on the biochemistry of vision.
Wald’s social and political activism took an increasingly central position in her life. She protested the use of science to aid Vietnam war efforts and began to question the use of animals in research. Wald was critical of what she termed “genomania” – a gene-centric oversimplification of biology that she believed not only misrepresented the complexity of the world, but also wrongly legitimized eugenic and discriminatory thinking. Lastly, Wald was a fierce feminist, creating the Harvard course: “Biology and Women’s Issues”, challenging existing male-dominated power structures in the sciences, and debunking efforts to claim a biological basis for gender inequality.
Is (or was) their research under-valued because of their identity?
Due to her identify as a woman, Wald struggled for years to be recognized by the male-dominated faculty and noted that all of her fellow female scientists were stuck in “nonjobs”, despite their accomplishments.
Are there other scientists/research examples that this example can replace or be added to?
George Wald
Slide 2: Research Overview
Take home message of study
Wald’s most significant contribution to the field was showing that light acts on the visual system through a chemical re-arrangement (isomerization) of the visual pigment rhodopsin, which triggers a series of molecular pathways (photoreceptor excitation) ultimately allowing the brain to detect light.
Study system
This image shows close-up images of eyes of some of the organisms that Wald used to study the visual system (from top left to bottom right: squid, cow, chicken, bullfrog). Other organisms Wald used in her studies are the octopus, cuttlefish, lobster, rhesus monkey, and cusk fish.
Sources for images:
cow: https://www.drovers.com/article/eyes-have-it-cows-dominance-shown-through-sight
squid: https://en.wikipedia.org/wiki/Cephalopod_eye#/media/File:Squid_eye.jpg
bullfrog: https://www.wildrepublic.com/product/bullfrog/
chicken: https://www.backyardchickens.com/articles/information-on-chicken-eyesight.67301/
Slide 3: Key Research Points
Main figure
This figure summarizes how light acts on the light-sensitive pigment found in the rods of the retina (rhodopsin). When hit by light, a light-absorbing chromophore molecule (retinene) changes it shapes (isomerizes). If sufficiently heated, this change triggers neuronal excitation, where a signal is sent to the brain. Because the molecule is unstable, it splits apart in a process called bleaching and can then recombine over time to reform rhodopsin, allowing the molecule to detect light once again.
Societal Relevance
Rods are responsible for night vision, so understanding exactly how light acts on these cells has important implications for medical research on topics such as eye disease pathology, the impact of vitamins on eyesight, and the development of therapies to improve vision in low light. Furthermore, comparisons among different vertebrate and invertebrate species helps shed light on evolved differences in light perception, which could reveal connections between habitat light quality and species persistence.
