Connectivity, Organization, and Network Coordination of the Drosophila Central Circadian Clock.

Daily rhythms in behavior and physiology are orchestrated by a network of circadian clock neurons. Neuronal connections within this network produce coherence and robustness in circadian timekeeping that are uncharacteristic of rhythms driven by non-neuronal clocks. Using Drosophila as a model system, my thesis research aims to understand how clock neurons are physiologically connected and how their molecular oscillations are coordinated to produce coherent circadian rhythms. I have developed an experimental approach to address functional connectivity in the fly brain that combines chemogenetic excitation of neurons of interest with simultaneous monitoring of potential postsynaptic physiology with genetically encoded fluorescent sensors. Using this method, I have mapped connections in the clock network mediated by the critical neuropeptide Pigment-Dispersing Factor. In addition, I have performed ex vivo patch-clamp recordings of the fly clock neurons and provided the first electrophysiological characterization of the dorsal lateral neurons (LNds), the Evening Oscillator of the clock network. I find that the neuronal activity LNds is modulated by multiple fast neurotransmitters, and that a group of dorsal clock neurons provides inhibitory synaptic input onto the LNds. Furthermore, I find that while GABAergic inhibition of the clock network promotes sleep at night, glutamatergic inhibition promotes wakefulness during the day. To study how the molecular rhythms of clock neurons are coordinated, I have genetically sped-up or slowed-down the molecular clock in specific subsets of clock neurons and determined how such manipulations affect the molecular oscillations in un-manipulated clock neuron classes and sleep/activity rhythms. I find that the various groups of clock neurons do not display uniform modes of coupling. Rather, they display unique and complex coupling relationships that vary from group to group. In contrast to the widely accepted “Master Pacemaker” model, my results show that the clock network consists of multiple independent oscillators, each unified by its neuropeptide output. Lastly, I find that robust circadian rhythms require coherence of molecular clocks across a much larger proportion of the clock network than previously thought. Collectively, my thesis research greatly advances our understanding of how the circadian clock neuron network is wired and how it is organized and coordinated.PhDMolecular, Cellular and Developmental BiologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/133295/1/zepenyao_1.pd

A neural network underlying circadian entrainment and photoperiodic adjustment of sleep and activity in Drosophila

A sensitivity of the circadian clock to light/dark cycles ensures that biological rhythms maintain optimal phase relationships with the external day. In animals, the circadian clock neuron network (CCNN) driving sleep/activity rhythms receives light input from multiple photoreceptors, but how these photoreceptors modulate CCNN components is not well understood. Here we show that the Hofbauer-Buchner eyelets differentially modulate two classes of ventral lateral neurons (LNvs) within the Drosophila CCNN. The eyelets antagonize Cryptochrome (CRY)- and compound-eye-based photoreception in the large LNvs while synergizing CRY-mediated photoreception in the small LNvs. Furthermore, we show that the large LNvs interact with subsets of “evening cells” to adjust the timing of the evening peak of activity in a day length-dependent manner. Our work identifies a peptidergic connection between the large LNvs and a group of evening cells that is critical for the seasonal adjustment of circadian rhythms. SIGNIFICANCE STATEMENT In animals, circadian clocks have evolved to orchestrate the timing of behavior and metabolism. Consistent timing requires the entrainment these clocks to the solar day, a process that is critical for an organism's health. Light cycles are the most important external cue for the entrainment of circadian clocks, and the circadian system uses multiple photoreceptors to link timekeeping to the light/dark cycle. How light information from these photorecptors is integrated into the circadian clock neuron network to support entrainment is not understood. Our results establish that input from the HB eyelets differentially impacts the physiology of neuronal subgroups. This input pathway, together with input from the compound eyes, precisely times the activity of flies under long summer days. Our results provide a mechanistic model of light transduction and integration into the circadian system, identifying new and unexpected network motifs within the circadian clock neuron network

Establishing thresholds of handgrip strength based on mortality using machine learning in a prospective cohort of Chinese population

BackgroundThe relative prognostic importance of handgrip strength (HGS) in comparison with other risk factors for mortality remains to be further clarified, and thresholds used for best identify high-risk individuals in health screening are not yet established. Using machine learning and nationally representative data from the China Health and Retirement Longitudinal Study (CHARLS), the study aimed to investigate the prognostic importance of HGS and establish sex-specific thresholds for health screening.MethodsA total of 6,762 participants from CHARLS were enrolled. A random forest model was built using 30 variables with all-cause mortality as outcome. SHapley Additive exPlanation values were applied to explain the model. Cox proportional hazard models and Harrell’s C index change were used to validate the clinical importance of the thresholds.ResultsAmong the participants, 3,102 (45.9%) were men, and 622 (9.1%) case of death were documented follow-up period of 6.78 years. The random forest model identified HGS as the fifth important prognostic variable, with thresholds for identifying high-risk individuals were < 32 kg in men and < 19 kg in women. Low HGS were associated with all-cause mortality [HR (95% CI): 1.77 (1.49–2.11), p < 0.001]. The addition of HGS thresholds improved the predictive ability of an established office-based risk score (C-index change: 0.022, p < 0.001).ConclusionOn the basis of our thresholds, low HGS predicted all-cause mortality better than other risk factors and improved prediction of a traditional office-based risk score. These results reinforced the clinical utility of measurement of HGS in health screening

DiVA -Digitala Vetenskapliga Arkivet

IR spectra, TG analysis and x-ray diffraction showed a solvated structure for the as-grown C 60 microtubes. Through a gentle heat-treatment in vacuum, pure C 60 microtubes with single crystalline fcc structure were obtained after the elimination of solvents. It is suggested that the C 60 microtubes form through self-assembly from several individual C 60 nanorods

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Glucose-Sensing Neurons Reciprocally Regulate Insulin and Glucagon

A recent paper by Oh et al. identified a single pair of neurons in the fruit fly brain that directly senses 'blood' glucose levels and reciprocally regulates the secretion of insulin and glucagon. This study provides insight into how the brain regulates the circulation and storage of glucose

Serotonergic neurons translate taste detection into internal nutrient regulation

The nervous and endocrine systems coordinately monitor and regulate nutrient availability to maintain energy homeostasis. Sensory detection of food regulates internal nutrient availability in a manner that anticipates food intake, but sensory pathways that promote anticipatory physiological changes remain unclear. Here, we identify serotonergic (5-HT) neurons as critical mediators that transform gustatory detection by sensory neurons into the activation of insulin-producing cells and enteric neurons in Drosophila. One class of 5-HT neurons responds to gustatory detection of sugars, excites insulin-producing cells, and limits consumption, suggesting that they anticipate increased nutrient levels and prevent overconsumption. A second class of 5-HT neurons responds to gustatory detection of bitter compounds and activates enteric neurons to promote gastric motility, likely to stimulate digestion and increase circulating nutrients upon food rejection. These studies demonstrate that 5-HT neurons relay acute gustatory detection to divergent pathways for longer-term stabilization of circulating nutrients

Research on the Corrosion Damage Mechanism of Concrete in Two Freeze–Thaw Environments

This study aims to investigate the effects of two freeze–thaw environments (i.e., maintenance freeze-thaw (MFT) environment and immersion freeze-thaw (IFT) environment) on the durability performance, deterioration rules, and mechanisms of concrete. In MFT, the concrete specimens were firstly cured in the standard curing environment (temperature, 20 ± 3, humidity, not less than 95%, and ages, 28 d) and then were carried out in freeze–thaw environment, while in IFT, the concrete specimens were firstly cured in the salt (NaHCO3, NaCl, and Na2SO4) immersion environment for 90 d and then were carried out in freeze–thaw environment. In this study, the damage features, relative dynamic elastic modulus, mass changes, and erosion-resistance coefficient of concrete have been measured. Thereafter, using the scanning electron microscopy (SEM) and the mercury intrusion porosimetry (MIP), the air-void structure parameters and the microstructures have been measured, respectively. The results show that the relative dynamic elastic modulus and the erosion-resistance coefficient of the compressive strength of the concrete in the IFT environment are, respectively, 14.3% and 21.0% higher than those of the concrete in the MFT environment. In addition, the results of the microstructure analyses show that the corrosion damages of the concrete are mainly caused by the combined action of the corrosion products of ettringite and freeze–thaw environment. However, the damage to the concrete in the MFT environment is more serious than that in the IFT environment. The results of the MIP analysis show that the harmful pore value for the concrete in the MFT environment is almost two times larger than that for the concrete in the IFT environment