RET @ BU Week 2

This week started out with many questions. Upon assessing our accomplishments from week one, my colleague Liz and I have many questions that can be developed into possible investigations.  Our newly acquired understanding of Ashwin's (BU Ph. D candidate) phase contrast microscope rendered it possible for us to develop testable hypotheses within the time frame we are working with.

My week one blog ended with questions about about using the microscope as a diagnostic tool (RDT).  However, our time frame, advances in the image processing of the microscope in question, as well as certain lab protocols (access to bodily fluids) forced us to re-think our hypothesis. Given that we use regular brightfield microscopes in the classroom, we thought that it would be a good idea to investigate brightfield image versus phase contrast imaging in the lab.  Ideally, we hope to generate images such as the ones on the left as part of our collected data.

 Differences in light absorption between living cells and their surrounding nutrients are often negligible.  In other words, you can't tell where the cell membrane ends and the organelles begins using brightfield microscopes.  Phase contrast microscopy uses the very small refractive index of different cellular components and their surrounding to produce contrast in these organelles and similar transparent specimens.  The simplest example of refractive index can be observed in the image on the right.

Among others, here are some of the hypotheses we plan on investigating:

1. General observation of the specimens without stain in brightfield vs. phase contrast - How does the look of these specimens (Amoeba, daphnia, euglena, paramecium) differ?
2. Depth of view: cell membrane vs. organelles or cytoplasm. Can cilia & flagella be observed in brightfield and/or phase contrast?
3. Organisms phototaxis behavior (LED in phage contrast vs. bright field)

• What wavelength of light do euglena exhibit positive or negative phototaxis (toward or away from)?
• At what speed do euglena move toward or away from the light source (brightfield vs. LED)?

"I'm going to be a .... I don't need all these science courses." 
Note: The phase contrast optical theory was developed in theoretical physics.  Yet, it led innovative developments in seemingly unrelated disciplines, us as biology and medicine.