Yeast V-ATPase Regulation by Phosphofructokinase-1

V-ATPase is a vacuolar (lysosome-like) ATPase-dependent proton pump necessary for maintaining pH homeostasis in the organelles of the endomembrane system. It also contributes to regulation of the cytosol pH and the extracellular pH. In specialized cells (renal intercalated cells, epididymis clear cells, and osteoclasts), V-ATPase proton transport supports urinary acidification, sperm maturation, and bone resorption. Genetic mutations of V-ATPase expressed in those tissue-specific cells cause distal renal tubular acidosis, infertility, and osteopetrosis. V-ATPases are composed of a peripheral domain (V1), which hydrolyzes ATP, and a membrane-bound domain (Vo), which transports proton. V-ATPase activity is tightly regulated in vivo by numbers of mechanisms, including reversible disassembly of the V1 and Vo domains. Glucose, the nutrient oxidized in glycolysis, modulates reversible dissociation of V-ATPase. This dissertation was aimed at understanding how subunits of phosphofructokinase-1 (α subunit and β subunit) regulate V-ATPase function. Our results showed that both subunits are important for V-ATPase activity, but β subunit displayed more significant phenotypes. Deletion of β subunit reduced glucose-dependent V1Vo reassembly and altered V-ATPase binding to its assembly factor, RAVE. We additionally investigated the mechanisms by which phosphofructokinase-1 controls V-ATPase function. We concluded that glucose-dependent V1Vo reassembly and V-ATPase function at steady state were controlled by the glycolytic flux, independently of phosphofructokinase-1. Notably, V-ATPase activation in vivo correlated with the presence of phosphoglycerate kinase at vacuolar membranes. These studies further advanced our understanding how glucose controls V-ATPase pumps in vivo

Feedforward Compensation And Cascaded Control Scheme For Trajectory Tracking Of Pneumatic Muscle Actuated System

Over the past decade, pneumatic muscle actuators (PMA) has been steadily receiving much attention not only in the areas of industrial applications as well in promising research areas such as robotics and biomedical engineering. The popularity can be much associated with the attractive advantages PMA has to offer such as inherent compliant safety, high power to weight ratio and compact form factor. Despite the attractive advantages it has to offer, PMA exhibits significant nonlinear characteristics such as hysteretic behavior and creep phenomenon. Subsequently, these dynamic and time varying behaviors often makes modelling and real time motion control a challenging effort. Although many control methods have been developed, these controller design procedures frequently require exact model of mechanism and deep understanding in modern control theory which leads to their impracticability. Henceforth, in this research, a practical control strategy namely the Feedforward Compensation with Cascaded Control (FFC) scheme is proposed for the trajectory control of the PMA mechanism. The practical control scheme employed heavily considers on simple structure and straightforward design framework. Hence, the proposed FFC controller includes control elements that are derived from the measured open loop responses. The tracking performance is examined and compared to a Proportional Integral Derivative (PID) controller through experimental works. Experimental results show that the proposed controller can produce zero steady state error in step positioning. Similarly, the feedforward compensation with cascaded control scheme performs better in tracking when compared to PID controller with a higher tracking accuracy with an average improvement of 45 % and 64 % for maximal tracking error and root mean square error respectively. Likewise, when evaluated for robustness towards load variations, the proposed control strategy provides an ameliorated performance over the PID controller with an error improvement of 58 % in terms of maximal tracking error and 44 % in terms of root mean square error

Toward Transparent Sequence Models with Model-Based Tree Markov Model

In this study, we address the interpretability issue in complex, black-box Machine Learning models applied to sequence data. We introduce the Model-Based tree Hidden Semi-Markov Model (MOB-HSMM), an inherently interpretable model aimed at detecting high mortality risk events and discovering hidden patterns associated with the mortality risk in Intensive Care Units (ICU). This model leverages knowledge distilled from Deep Neural Networks (DNN) to enhance predictive performance while offering clear explanations. Our experimental results indicate the improved performance of Model-Based trees (MOB trees) via employing LSTM for learning sequential patterns, which are then transferred to MOB trees. Integrating MOB trees with the Hidden Semi-Markov Model (HSMM) in the MOB-HSMM enables uncovering potential and explainable sequences using available information

3D experimental study on a cylindrical floating breakwater system

The objective of the present study is to investigate the performance of a cylindrical floating breakwater system based on 3D experimental tests. The experiments were carried out in the wave basin (36 m*60 m*1.5 m)of the Ocean University of China. The cylindrical floating breakwater system consists of 10cylindrical floating breakwater units and 10mesh cages with balls in them, connected by 18 connectors and moored by a taut mooring system. The wave transmission coefficients, reflection coefficients, dissipation coefficients and motion responses of the floating breakwater are measured in both oblique and beam sea conditions. It is found that with the increase of the wavelength, both of the wave transmission coefficients and motion response amplitude of the FB system suffers an increase before it reaches its peak value, followed by a decrease trend. It can be concluded from the experiments that the proposed FB system has a satisfactory performance and it can be used to a wide range of sea conditions

Crystallization of Adenylylsulfate Reductase from Desulfovibrio gigas: A Strategy Based on Controlled Protein Oligomerization

Adenylylsulfate reductase (adenosine 5′-phosphosulfate reductase, APS reductase or APSR, E.C.1.8.99.2) catalyzes the conversion of APS to sulfite in dissimilatory sulfate reduction. APSR was isolated and purified directly from massive anaerobically grown Desulfovibrio gigas, a strict anaerobe, for structure and function investigation. Oligomerization of APSR to form dimers–α_2β_2, tetramers–α_4β_4, hexamers–α_6β_6, and larger oligomers was observed during purification of the protein. Dynamic light scattering and ultracentrifugation revealed that the addition of adenosine monophosphate (AMP) or adenosine 5′-phosphosulfate (APS) disrupts the oligomerization, indicating that AMP or APS binding to the APSR dissociates the inactive hexamers into functional dimers. Treatment of APSR with β-mercaptoethanol decreased the enzyme size from a hexamer to a dimer, probably by disrupting the disulfide Cys156—Cys162 toward the C-terminus of the β-subunit. Alignment of the APSR sequences from D. gigas and A. fulgidus revealed the largest differences in this region of the β-subunit, with the D. gigas APSR containing 16 additional amino acids with the Cys156—Cys162 disulfide. Studies in a pH gradient showed that the diameter of the APSR decreased progressively with acidic pH. To crystallize the APSR for structure determination, we optimized conditions to generate a homogeneous and stable form of APSR by combining dynamic light scattering, ultracentrifugation, and electron paramagnetic resonance methods to analyze the various oligomeric states of the enzyme in varied environments

Growth mechanism and magnon excitation in NiO nanowalls

The nanosized effects of short-range multimagnon excitation behavior and short-circuit diffusion in NiO nanowalls synthesized using the Ni grid thermal treatment method were observed. The energy dispersive spectroscopy mapping technique was used to characterize the growth mechanism, and confocal Raman scattering was used to probe the antiferromagnetic exchange energy J2 between next-nearest-neighboring Ni ions in NiO nanowalls at various growth temperatures below the Neel temperature. This study shows that short spin correlation leads to an exponential dependence of the growth temperatures and the existence of nickel vacancies during the magnon excitation. Four-magnon configurations were determined from the scattering factor, revealing a lowest state and monotonic change with the growth temperature

Significance of Coronary Calcification for Prediction of Coronary Artery Disease and Cardiac Events Based on 64-Slice Coronary Computed Tomography Angiography

This work aims to validate the clinical significance of coronary artery calcium score (CACS) in predicting coronary artery disease(CAD) and cardiac events in 100 symptomatic patients (aged 37–87 years, mean 62.5, 81 males) that were followed up for a mean of 5 years. Our results showed that patients with CAD and cardiac events had significantly higher CACS than those without CAD and cardiac events, respectively. The corresponding data were 1450.42 ± 3471.24 versus 130 ± 188.29 (P 1000. Increased CACS (>100)was also associated with an increased frequency of multi-vessel disease. Nonetheless, 3 (20%) out of 15 patients with zero CACS had single-vessel disease. Significant correlation (P < 0.001) was observed between CACS and CAD on a vessel-based analysis for coronary arteries. It is concluded that CACS is significantly correlated with CAD and cardiac events

Increased Risk for Entamoeba histolytica Infection and Invasive Amebiasis in HIV Seropositive Men Who Have Sex with Men in Taiwan

Entamoeba histolytica, morphologically identical to but genetically different from E. dispar and E. moshkovskii, is the causative agent of amebiasis. Recently there have been reports of increased risk for amebiasis among men who have sex with men (MSM) due to oral-anal sexual contact in several developed countries. In this longitudinal follow-up study, the incidence of amebiasis was determined among HIV-infected patients using serological and specific amebic antigen assays. DNA extracted from stool samples containing E. histolytica were analyzed by PCR, sequenced, and compared. Clinical manifestations and treatment response of invasive amebiasis in HIV-infected patients were reviewed. The results demonstrated that HIV-infected MSM were at significantly higher risk of amebiasis than patients from other risk groups. Clustering of E. histolytica isolates by sequencing analyses from geographically unrelated patients suggested person-to-person transmission. Despite immunosuppression, amebic liver abscesses and colitis responded favorably to metronidazole therapy. It is important to investigate in areas of high incidence of both amebiasis and HIV (sub-Saharan Africa) how generalizable these findings are