Autoregulation of Osteocyte Sema3A Orchestrates Estrogen Action and Counteracts Bone Aging

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Complete Nucleotide Sequence and Genetic Organization of Aichi Virus, a Distinct Member of the Picornaviridae Associated with Acute Gastroenteritis in Humans

The complete nucleotide sequence of a novel enteric virus, Aichi virus, associated with nonbacterial acute gastroenteritis in humans was determined. The Aichi virus genome proved to be a single-stranded positive-sense RNA molecule with 8,251 bases excluding a poly(A) tail; it contains a large open reading frame with 7,302 nucleotides that encodes a potential polyprotein precursor of 2,433 amino acids. The genome contains a 5′ nontranslated region (NTR) with 712 bases and a 3′ NTR with 240 bases followed by a poly(A) tail. The structure of the genome, VPg–5′ NTR–leader protein–structural proteins–nonstructural proteins–3′ NTR–poly(A), was found to be typical of a picornavirus. The VP0-VP3 and VP3-VP1 cleavage sites were determined to be Q-H and Q-T, respectively, by N-terminal amino acid sequence analyses using purified virion proteins. Possible cleavage sites, Q-G, Q-A, and Q-S, which cleave P2 and P3 polyproteins were found to be similar to those of picornaviruses. A dendrogram based on 3D^pol proteins indicated that Aichi virus is genetically distinct from the known six genera of picornaviruses including entero-, rhino-, cardio-, aphtho-, and hepatovirus and echovirus 22. Considering this together with other properties of the virus (T. Yamashita, S. Kobayashi, K. Sakae, S. Nakata, S. Chiba, Y. Ishihara, and S. Isomura, J. Infect. Dis. 164:954–957, 1991), we propose that Aichi virus be regarded as a new genus of the family Picornaviridae.     

TEMPERATURE-DEPENDENT CHANGES IN COLONY SIZE OF THE FRESHWATER PENNATE DIATOM ASTERIONELLA FORMOSA (BACILLARIOPHYCEAE) AND THEIR POSSIBLE ECOLOGICAL IMPLICATIONS1

Changes in colony size (cell number per colony) of Asterionella Formosa Hass. were experimentally evaluated in relation to water temperature using two types of clones having colony sizes of four or eight cells. The clones were isolated from two different temperate freshwater lakes. Both clones showed the same general trend with changing temperature. Most of the colonies were normal in size at low temperatures, but colony size was twice as large at high temperatures. Variable colony sizes were present at low percentages. Colony separation occurred at the oldest connection within the colony after cell division. Culture experiments showed that the rates of specific growth and colony separation were balanced except for a rather short period of time when the temperature was changed. Optical and scanning electron micrography did not show any distinctive morphological structure at the point of connection except for porelli and mucilage pads. Seasonal changes in colony size of A. formosa observed in a freshwater lake are discussed based on these temperature results.     

Light and dark rate-determining steps in electron transport reactions in spinach chloroplasts

Effects of various factors, such as uncouplers, inhibitors andinhibitory treatments of chloroplasts, on light-dependent (K_L)and -independent (K_D) parameters estimated from the light intensity-activityrelationship, were studied. In the Hill-reaction with ferricyanide or methyl viologen aselectron acceptor, a reagent or treatment affecting electrontransport on one side of system II, which included the rate-limitingstep for the entire electron transport, affected only K_D. Incontrast, a change in the rate of electron transfer on the otherside of system II affected only K_L. We inferred that K_D representsthe rate of the dark rate-limiting step at infinite light intensity.On the other hand, K_L is concerned to the quantum yield of theprimary reaction, as well as to the rate constant of the reactionon the side of system II opposite to that of the rate-limitingstep at infinite light intensity. Effects of inhibitors and treatments on the reaction parameterschanged markedly depending on the pH of the reaction medium.However, the contrasting effects of inhibitors affecting theopposite sides of system II were consistently observed in definedlevels of pH. This was also the case in the photoreduction ofmethyl viologen with the ascorbate-DPIP couple as electron donor. ¹ Present address: Department of Biology, Faculty of Science,Toho University, Narashino, Chiba, Japan. (Received May 2, 1972; )     

Capturing microscopic features of bone remodeling into a macroscopic model based on biological rationales of bone adaptation

To understand Wolff’s law, bone adaptation by remodeling at the cellular and tissue levels has been discussed extensively through experimental and simulation studies. For the clinical application of a bone remodeling simulation, it is significant to establish a macroscopic model that incorporates clarified microscopic mechanisms. In this study, we proposed novel macroscopic models based on the microscopic mechanism of osteocytic mechanosensing, in which the flow of fluid in the lacuno-canalicular porosity generated by fluid pressure gradients plays an important role, and theoretically evaluated the proposed models, taking biological rationales of bone adaptation into account. The proposed models were categorized into two groups according to whether the remodeling equilibrium state was defined globally or locally, i.e., the global or local uniformity models. Each remodeling stimulus in the proposed models was quantitatively evaluated through image-based finite element analyses of a swine cancellous bone, according to two introduced criteria associated with the trabecular volume and orientation at remodeling equilibrium based on biological rationales. The evaluation suggested that nonuniformity of the mean stress gradient in the local uniformity model, one of the proposed stimuli, has high validity. Furthermore, the adaptive potential of each stimulus was discussed based on spatial distribution of a remodeling stimulus on the trabecular surface. The theoretical consideration of a remodeling stimulus based on biological rationales of bone adaptation would contribute to the establishment of a clinically applicable and reliable simulation model of bone remodeling.     

Heat-Stability of Iron-Sulfur Centers and P-700 in Photosystem I Reaction Center Complexes Isolated from the Thermophilic Cyanobacterium Synechococcus elongatus

Stabilities of iron-sulfur centers and reaction center chlorophyllP-700 in Photosystem I reaction center complex (CP1-a), isolatedby sodium dodecyl sulfate treatment from the thermophilic cyanobacteriumSynechococcus elongatus, were studied by EPR and optical spectroscopy.P-700 was destroyed by treatment at temperatures above 80?Cfor 5 minutes with a half inactivation temperature of 93?C.The three iron-sulfur centers F_A, F_B and F_X showed similar thermalstabilities and were half inactivated at about 70?C. Thus, theisolated Photosystem I reaction center complexes of S. elongatusare still highly resistant to heat. (Received May 9, 1990; Accepted June 25, 1990)     

Isolation of an oxygen-evolving Photosystem II preparation containing only one tightly bound calcium atom from a chlorophyll b-deficient mutant of rice

Oxygen-evolving Photosystem II (PS II) particles were prepared from the thylakoid membranes of a chlorophyll b-less rice mutant, which totally lacks light-harvesting chlorophyll a/b proteins, after solubilization with β-octylglucoside. The preparation was essentially free of Photosystem I as judged from its low-temperature fluorescence spectrum and polypeptide composition. The PS II particles contained all the major subunit polypeptides of the PS II reaction center core complexes and the three extrinsic proteins related to oxygen evolution. The relative abundances of the 33, 21 and 15 kDa proteins were 100, 64 and 20%, respectively, of the corresponding proteins in the mutant thylakoids. The chlorophyll-to-Q_A ratio was 53 and there was only one bound Ca²⁺ per Q_A. Thus, one of the two bound Ca²⁺ present in the oxygen-evolving PS II membrane preparations from wild-type rice (Shen J.-R., Satoh, K. and Katoh, S. (1988) Biochim. Biophys. Acta 933, 358–364) is missing. The mutant PS II particles were highly active in oxygen evolution in the absence of exogenously added Ca²⁺, although addition of 5 mM Ca²⁺ enhanced the activity by 30%. When the 21 and 15 kDa proteins were supplemented to the particles, the Ca²⁺-effect disappeared and the rate of oxygen evolution increased to a level exceeding 1000 μmol O₂ per mg chlorophyll per h. The results indicate that the number of Ca²⁺ needed to promote a high rate of oxygen evolution is one per PS II in higher plants.     

Delphinidin-3-glucoside suppresses lipid accumulation in HepG2 cells

Delphinidin is an anthocyanidin commonly found in various fruits and vegetables. Delphinidin has been known to possess many functions, such as an antioxidant, and anti-inflammatory, anti-cancer and anti-muscular atrophy agent. In this study, we attempted to evaluate the effects of delphinidin on lipid accumulation in hepatocytes. The results showed that palmitic acid (PA)-induced cellular senescence in HepG2 cells and reduced the expression of SMARCD1, which is known to regulate senescence-associated lipid accumulation in hepatocytes. However, delphinidin-3-glucoside (D3 g) suppressed PA-induced senescence and reversed the expression of SMARCD1 to the level of untreated HepG2 cells. Consequently, D3 g inhibited PA-induced lipid accumulation through the restoration of the expression of SMARCD1 and fatty acid oxidation genes. Taken together, our results suggest that D3 g suppresses the lipid accumulation induced by hepatocyte senescence.     

A Vertical Gradient of the Chloroplast Abundance among Leaves of Chenopodium album

The abundances of chloroplasts in leaves on the main stems ofChenopodium album at different height levels were investigatedin relation to the photosynthetic capacity and light environmentof the leaves. (1) The number of chloroplasts per mesophyllcell decreased with descending position of leaves, except foryoung developing leaves at the top of plants that had smallerchloroplast numbers per cell than matured leaves beneath them.Contents of chlorophyll and ribulose-1,5-bisphosphate carboxylase/oxygenaseper leaf area that were highest in the topmost young leavesand decreased with decreasing height level indicate that thereis a vertical gradient of chloroplast abundance per leaf areadecreasing from the top of the leaf canopy with depth. (2) Light-saturatingrate of photosynthetic oxygen evolution per leaf area of maturedleaves decreased more steeply with decreasing leaf positionthan the chloroplast number per cell. Gradients of chlorophylland the enzyme protein contents were also steeper than thatof the chloroplast number. Loss of photosynthesis in lower leavesis, therefore, ascribed partly to loss of whole chloroplastsand partly to reduced photosynthetic capacities of the remainingchloroplasts. (3) The chloroplast number per cell in newly expandedsecond leaves was comparable to those in leaves that have developedat later stages of the plant growth but decreased graduallyduring leaf senescence both in the dark and light. The formationof the vertical gradient of chloroplast abundance is, therefore,ascribed to loss of whole chloroplasts during senescence ofleaves. (4) Irradiance a leaf receives decreased sharply fromthe top of the canopy with depth. The physiological or ecophysiologicalsignificance of the vertical distribution of chloroplasts amongleaves was discussed taking light environments of leaves intoconsideration. (Received July 31, 1995; Accepted October 20, 1995)