A Design Pattern for Decentralised Decision Making

The engineering of large-scale decentralised systems requires sound methodologies to guarantee the attainment of the desired macroscopic system-level behaviour given the microscopic individual-level implementation. While a general-purpose methodology is currently out of reach, specific solutions can be given to broad classes of problems by means of well-conceived design patterns. We propose a design pattern for collective decision making grounded on experimental/theoretical studies of the nest-site selection behaviour observed in honeybee swarms (Apis mellifera). The way in which honeybee swarms arrive at consensus is fairly well-understood at the macroscopic level. We provide formal guidelines for the microscopic implementation of collective decisions to quantitatively match the macroscopic predictions. We discuss implementation strategies based on both homogeneous and heterogeneous multiagent systems, and we provide means to deal with spatial and topological factors that have a bearing on the micro-macro link. Finally, we exploit the design pattern in two case studies that showcase the viability of the approach. Besides engineering, such a design pattern can prove useful for a deeper understanding of decision making in natural systems thanks to the inclusion of individual heterogeneities and spatial factors, which are often disregarded in theoretical modelling.     

The First Identification of Carbohydrate Binding Modules Specific to Chitosan

Two carbohydrate binding modules (DD1 and DD2) belonging to CBM32 are located at the C terminus of a chitosanase from Paenibacillus sp. IK-5. We produced three proteins, DD1, DD2, and tandem DD1/DD2 (DD1+DD2), and characterized their binding ability. Transition temperature of thermal unfolding (T_m) of each protein was elevated by the addition of cello-, laminari-, chitin-, or chitosan-hexamer (GlcN)₆. The T_m elevation (ΔT_m) in DD1 was the highest (10.3 °C) upon the addition of (GlcN)₆ and was markedly higher than that in DD2 (1.0 °C). A synergistic effect was observed (ΔT_m = 13.6 °C), when (GlcN)₆ was added to DD1+DD2. From isothermal titration calorimetry experiments, affinities to DD1 were not clearly dependent upon chain length of (GlcN)_n; ΔG_r° values were −7.8 (n = 6), −7.6 (n = 5), −7.6 (n = 4), −7.6 (n = 3), and −7.1 (n = 2) kcal/mol, and the value was not obtained for GlcN due to the lowest affinity. DD2 bound (GlcN)_n with the lower affinities (ΔG_r° = −5.0 (n = 3) ∼ −5.2 (n = 6) kcal/mol). Isothermal titration calorimetry profiles obtained for DD1+DD2 exhibited a better fit when the two-site model was used for analysis and provided greater affinities to (GlcN)₆ for individual DD1 and DD2 sites (ΔG_r° = −8.6 and −6.4 kcal/mol, respectively). From NMR titration experiments, (GlcN)_n (n = 2∼6) were found to bind to loops extruded from the core β-sandwich of individual DD1 and DD2, and the interaction sites were similar to each other. Taken together, DD1+DD2 is specific to chitosan, and individual modules synergistically interact with at least two GlcN units, facilitating chitosan hydrolysis.     

Wild‐type and specific mutant androgen receptor mediates transcription via 17β‐estradiol in sex hormone‐sensitive cancer cells

We previously encountered regulatory processes wherein dihydrotestosterone (DHT) exerted its inhibitory effect on parathyroid hormone‐related protein (PTHrP) gene repression through the estrogen receptor (ER)α, but not the androgen receptor (AR), in breast cancer MCF‐7 cells. Here, we investigated whether such aberrant ligand‐nuclear receptor (NR) interaction is present in prostate cancer LNCaP cells. First, we confirmed that LNCaP cells expressed large amounts of AR at negligible levels of ERα/β or progesterone receptor. Both suppression of PTHrP and activation of prostate‐specific antigen genes were observed after independent administration of 17β‐estradiol (E2), DHT, or R5020. Consistent with the notion that the LNCaP AR lost its ligand specificity due to a mutation (Thr‐Ala877), experiments with siRNA targeting the respective NR revealed that the AR monopolized the role of the mediator of shared hormone‐dependent regulation, which was invariably associated with nuclear translocation of this mutant AR. Microarray analysis of gene regulation by DHT, E2, or R5020 disclosed that more than half of the genes downstream of the AR (Thr‐Ala877) overlapped in the LNCaP cells. Of particular interest, we realized that the AR (wild‐type [wt]) and AR (Thr‐Ala877) were equally responsible for the E2‐AR interactions. Fluorescence microscopy experiments demonstrated that both EGFP‐AR (wt) and EGFP‐AR (Thr‐Ala877) were exclusively localized within the nucleus after E2 or DHT treatment. Furthermore, reporter assays revealed that some other cancer cells exhibited aberrant E2‐AR (wt) signaling similar to that in the LNCaP cells. We herein postulate the presence of entangled interactions between wt AR and E2 in certain hormone‐sensitive cancer cells. J. Cell. Physiol. 230: 1594–1606, 2015. © 2014 The Authors. Journal of Cellular Physiology Published by Wiley Periodicals, Inc.     

Knockdown of aquaporin-8 induces mitochondrial dysfunction in 3T3-L1 cells

BackgroundAquaporin-8 (AQP8), a member of the aquaporin water channel family, is expressed in various tissue and cells, including liver, testis, and pancreas. AQP8 appears to have functions on the plasma membrane and/or on the mitochondrial inner membrane. Mitochondrial AQP8 with permeability for water, H₂O₂ and NH₃ has been expected to have important role in various cells, but its information is limited to a few tissues and cells including liver and kidney. In the present study, we found that AQP8 was expressed in the mitochondria in mouse adipose tissues and 3T3-L1 preadipocytes, and investigated its role by suppressing its gene expression.MethodsAQP8-knocked down (shAQP8) cells were established using a vector expressing short hairpin RNA. Cellular localization of AQP8 was examined by western blotting and immunocytochemistry. Mitochondrial function was assessed by measuring mitochondrial membrane potential, oxygen consumption and ATP level measurements.ResultsIn 3T3-L1 cells, AQP8 was expressed in the mitochondria. In shAQP8 cells, mRNA and protein levels of AQP8 were decreased by about 75%. The shAQP8 showed reduced activities of complex IV and ATP synthase; it is probable that the impaired mitochondrial water handling in shAQP8 caused suppression of the electron transport and ADP phosphorylation through inhibition of the two steps which yield water. The reduced activities of the last two steps of oxidative phosphorylation in shAQP8 cause low routine and maximum capacity of respiration and mitochondrial hyperpolarization.ConclusionMitochondrial AQP8 contributes to mitochondrial respiratory function probably through maintenance of water homeostasis.General significanceThe AQP8-knocked down cells we established provides a model system for the studies on the relationships between water homeostasis and mitochondrial function.     

Substrate specificity of an esterase from the archaeon Sulfolobus tokodaii bearing a GGG(A)X motif

A GGG(A)X-type esterase (Est0071) from an archaeon catalyzes asymmetric hydrolysis of prochiral bulky malonic diesters in good enantioselectivity. The selectivity of Est0071 was for the opposite enantiomer to that previously shown for pig liver esterase, and the resulting enantiomeric excess of the products was higher. Est0071 could also catalyze the hydrolysis of various acetates of secondary alcohols, and showed moderate enantioselectivity in these reactions.     

Neurophysiological Effects of Sleep Deprivation in Healthy Adults,a Pilot Study

Total sleep deprivation (TSD) may induce fatigue, neurocognitive slowing and mood changes, which are partly compensated by stress regulating brain systems, resulting in altered dopamine and cortisol levels in order to stay awake if needed. These systems, however, have never been studied in concert. At baseline, after a regular night of sleep, and the next morning after TSD, 12 healthy subjects performed a semantic affective classification functional magnetic resonance imaging (fMRI) task, followed by a [¹¹C]raclopride positron emission tomography (PET) scan. Saliva cortisol levels were acquired at 7 time points during both days. Affective symptoms were measured using Beck Depression Inventory (BDI), Spielberger State Trait Anxiety Index (STAI) and visual analogue scales. After TSD, perceived energy levels, concentration, and speed of thought decreased significantly, whereas mood did not. During fMRI, response speed decreased for neutral words and positive targets, and accuracy decreased trendwise for neutral words and for positive targets with a negative distracter. Following TSD, processing of positive words was associated with increased left dorsolateral prefrontal activation. Processing of emotional words in general was associated with increased insular activity, whereas contrasting positive vs. negative words showed subthreshold increased activation in the (para)hippocampal area. Cortisol secretion was significantly lower after TSD. Decreased voxel-by-voxel [¹¹C]raclopride binding potential (BP_ND) was observed in left caudate. TSD induces widespread cognitive, neurophysiologic and endocrine changes in healthy adults, characterized by reduced cognitive functioning, despite increased regional brain activity. The blunted HPA-axis response together with altered [¹¹C]raclopride binding in the basal ganglia indicate that sustained wakefulness requires involvement of additional adaptive biological systems.