Food for thought-the metabolism of learning
Glucose and lactate have both been shown to be important modulators of memory processing. In the brain, glucose provides resources to neurons and astrocytes for energy needs, particularly during times of high activity such as memory processing. Astrocytes metabolize both glycogen and glucose to form lactate, which can then be transferred to neurons to provide energy - a model known as the astrocyte-neuron lactate shuttle. The current studies explore whether changes in extracellular lactate and glucose vary during memory tasks designed to promote egocentric learning (response training) or allocentric learning (place training). Previous work has demonstrated response training relies more on the striatum than the hippocampus while place training relies more on the hippocampus than striatum. We implanted biosensor probes designed to measure extracellular levels of glucose or lactate into the dorsal hippocampus or dorsal striatum of rats. The animals were then trained on either place or response tasks. Levels of lactate increased during training and while levels of glucose decreased initially, then increased as learning was attained. These results indicate while there may be a general increase in lactate production by astrocytes during learning, the uptake by neurons may be more specific to the brain areas necessary for the specific type of learning.
Stimulated Raman scattering microscopy for chemical information in tissue imaging
Chemical imaging techniques such as Raman spectroscopy derive their imaging contrast from the specimen’s inherent chemical vibrational modes. Without dyes, fluorescent labels, or extensive sample preparation, this family of imaging modalities determines chemical information about a specimen with minimal sample perturbation. In this manner, chemical imaging is ideal for use with certain live cell or animal and plant tissue imaging applications, and has strong potential for in vivo applications. One of the more recently developed non-linear Raman modalities, stimulated Raman scattering (SRS), is particularly exciting due to its fast imaging speed and high contrast fidelity as compared to other chemical imaging techniques. Here, we highlight the utility of chemical imaging with an emphasis on the unique strengths of SRS. We then explain how we are using SRS technology to expand and enhance tissue imaging research themes within our group.
An Increased Throughput Method for Screening Mechanochemical Reactions
Mechanophores are molecules that utilize mechanical forces to initiate chemical transformations. Recently, polymer-functionalized spiropyrans have been established as mechanophores in both solution and in the solid-state. When correctly attached to a polymer of sufficient molecular weight, a visible color change and fluorescence can be observed when the polymeric material is subjected to mechanical deformation. This color change is attributed to a 6-π electrocyclic ring-opening of the spiropyran initiated by mechanochemical transduction of macroscopic forces the molecular level to yield the highly conjugated merocyanine form of the mechanophore. Recently, an ultrasonication flow cell was created as an increased throughput method for characterizing mechanophore reactivity in solution-phase polymers. By coupling the characterization method, UV-Vis spectroscopy, to the sonication apparatus, a variety of fundamental parameters have been rapidly assessed for their influence on this mechanochemical reaction. This talk will highlight the effects of power intensity, flow rate, and polymer architecture on the mechanochemical reactivity of spiropyran mechanophores.