Biology subjects

Copeland, J. M.

Publications and source records attributed to Copeland, J. M..

4 recordsLinked to original sources

bioRxiv2026

Optimization and Validation of Whole-Room Indirect Calorimetry for Improved Accuracy and Temporal Resolution

With metabolic disease on the rise across the globe, the devices that can provide precise and reliable estimates of energy expenditure and macronutrient oxidation can play a critical role in the development and evaluation of therapeutic regimes and wearable technologies that can be used outside of the laboratory. Whereas, metabolic carts can provide short-term (minutes to hours) metabolic measurements, whole-room calorimeters enable long-duration (hours to days) metabolic assessment, providing insights into how metabolism changes in response to meals, activity, sleep, etc. Obtaining accurate metabolic measurement via whole-room calorimetry, however, requires rigorous methods for calibration and quality assurance. To date most room calorimeters have been tuned to assess energy expenditure over long periods of time, i.e. 24-hours. Here we present novel calibration and signal processing techniques and recommendations that aim to improve the utility of metabolic chambers for use over different measurement epochs. This work serves as both a transparent description of our hardware, validation procedures, and data processing approaches.

physiology↗

bioRxiv2023

Electron transport chain RNAi in glutamate neurons extends life span, increases sleep, and decreases locomotor activity in Drosophila melanogaster

RNAi targeting the electron transport chain has been proven to prolong life span in many different species, and experiments specifically with Drosophila melanogaster and Caenorhabditis elegans have shown a distinct role for neurons. To determine which subset of neurons is implicated in this life span extension, we used the GAL4/UAS system to activate RNAi against genes of Complex I and Complex V. We found life span extension of 18 - 24% with two glutamate neuron (D42 and VGlut) GAL4 lines. We used the GAL80 system to determine if the overlapping set of glutamate neurons in these two GAL4 lines imparts the life span extension. Limiting GAL4 activity to non-VGlut glutamate neurons in the D42 background failed to extend life span, suggesting that glutamate neurons have a unique role in aging. Interestingly, RNAi of the electron transport chain in D42 glutamate neurons also caused an increase in daytime and nighttime sleep and a decrease in nighttime locomotor activity. Changes to sleep patterns and prolonged life span were not accompanied by any changes in female fertility or response to starvation. Our findings demonstrate that a small subset of neurons can control life span, and further studies exploring the role of the electron transport chain in aging can be focused on the activity of glutamate neurons.

neuroscience↗

bioRxiv2020

Real-Time Measurement of Stimulated Dopamine Release in Compartments of the Adult Drosophila melanogaster Mushroom Body

Drosophila melanogaster, the fruit fly, is an exquisite model organism to understand neurotransmission. Dopaminergic signaling in the Drosophila mushroom body (MB) is involved in olfactory learning and memory, with different compartments controlling aversive learning (corner) vs appetitive learning (medial tip). Here, the goal was to develop techniques to measure endogenous dopamine in compartments of the MB for the first time. We compared three stimulation methods: acetylcholine (natural stimulus), P2X2 (chemogenetics), and CsChrimson (optogenetics). Evoked dopamine release was measured with fast-scan cyclic voltammetry in isolated adult Drosophila brains. Acetylcholine stimulated the largest dopamine release (0.40 M), followed by P2X2 (0.14 M), and CsChrimson (0.07 M). With the larger acetylcholine and P2X2 stimulations, there were no regional or sex differences in dopamine release. However, with CsChrimson, dopamine release was significantly higher in the corner than the medial tip, and females had more dopamine than males. Michaelis-Menten modeling of the single-light pulse revealed no significant regional differences in Km, but the corner had a significantly lower Vmax (0.12 M/s vs. 0.19 M/s) and higher dopamine release (0.05 M vs. 0.03 M). Optogenetic experiments are challenging because CsChrimson is also sensitive to blue light used to activate green fluorescent protein, and thus, light exposure during brain dissection must be minimized. These experiments expand the toolkit for measuring endogenous dopamine release in Drosophila, introducing chemogenetic and optogenetic experiments for the first time. With a variety of stimulations, different experiments will help improve our understanding of neurochemical signaling in Drosophila.

neuroscience↗

bioRxiv2020

RING Finger Protein 11 (RNF11) modulates dopamine release in Drosophila

Recent work indicates a role for RING finger protein 11 (RNF11) in Parkinson disease (PD) pathology, which involves the loss of dopaminergic neurons. However, the role of RNF11 in regulating dopamine neurotransmission has not been studied. In this work, we tested the effect of RNF11 RNAi knockdown or overexpression on stimulated dopamine release in the larval Drosophila central nervous system. Dopamine release was stimulated using optogenetics and monitored in real-time using fast-scan cyclic voltammetry at an electrode implanted in an isolated ventral nerve cord. RNF11 knockdown doubled dopamine release, but there was no decrease in dopamine from RNF11 overexpression. RNF11 knockdown did not significantly increase stimulated serotonin or octopamine release, indicating the effect is dopamine specific. Dopamine clearance was also changed, as RNF11 RNAi flies had a higher Vmax and RNF11 overexpressing flies had a lower Vmax than control flies. RNF11 RNAi flies had increased mRNA levels of dopamine transporter (DAT) in RNF11, confirming changes in DAT. In RNF11 RNAi flies, release was maintained better for stimulations repeated at short intervals, indicating increases in the recycled releasable pool of dopamine. Nisoxetine, a DAT inhibitor, and flupenthixol, a D2 antagonist, did not affect RNF11 RNAi or overexpressing flies differently than control. Thus, RNF11 knockdown causes early changes in dopamine neurotransmission, and this is the first work to demonstrate that RNF11 affects both dopamine release and uptake. RNF11 expression decreases in human dopaminergic neurons during PD, and that decrease may be protective by increasing dopamine neurotransmission in the surviving dopaminergic neurons.

neuroscience↗