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At least 19 recordsLinked to original sources

PubMed2004

Structure of the N-terminal domain of the circadian clock-associated histidine kinase SasA.

Circadian oscillators are endogenous biological systems that generate the approximately 24 hour temporal pattern of biological processes and confer a reproductive fitness advantage to their hosts. The cyanobacterial clock is the simplest known and the only clock system for which structural information for core component proteins, in this case KaiA, KaiB and KaiC, is available. SasA, a clock-associated histidine kinase, is necessary for robustness of the circadian rhythm of gene expression and implicated in clock output. The N-terminal domain of SasA (N-SasA) interacts directly with KaiC and likely functions as the sensory domain controlling the SasA histidine kinase activity. N-SasA and KaiB share significant sequence similarity and, thus, it has been proposed that they would be structurally similar and may even compete for KaiC binding. Here, we report the NMR structure of N-SasA and show it to be different from that of KaiB. The structural comparisons provide no clear details to suggest competition of SasA and KaiB for KaiC binding. N-SasA adopts a canonical thioredoxin fold but lacks the catalytic cysteine residues. A patch of conserved, solvent-exposed residues is found near the canonical thioredoxin active site. We suggest that this surface is used by N-SasA for protein-protein interactions. Our analysis suggests that the structural differences between N-SasA and KaiB are the result of only a few critical amino acid substitutions.

Amino Acid Sequence↗

PubMedDate not supplied

Sasa health exerts a protective effect on Her2/NeuN mammary tumorigenesis.

Bamboo grass leaves of different Sasa species have been widely used in food and medicine in Eastern Asia for hundreds of years. Of special interest are Kumazasa (Sasa senanensis rehder) leaves used to prepare an alkaline extract known as Sasa Health. This extract was reported to inhibit both the development and growth of mammary tumors in a mammary tumor strain of virgin SHN mice (1). We found that Sasa Health exerts a significant protective effect on spontaneous mammary tumorigenesis in another mouse model of human breast cancer, the transgenic FVB-Her2/NeuN mouse model. Two cohorts of Her2/NeuN female mice of different age (eleven-week-old and twenty-four-week-old) chronically treated with Sasa Health in drinking water showed both a delay in the development of tumors and reduced tumor multiplicity. Sasa Health also induced inhibition of mammary duct branching and side bud development in association with reduced angiogenesis. Altogether these findings indicate that Sasa Health contains phytochemicals that can effectively retard spontaneous mammary tumorigenesis.

Animals↗

PubMed2000

A kaiC-interacting sensory histidine kinase, SasA, necessary to sustain robust circadian oscillation in cyanobacteria.

Both regulated expression of the clock genes kaiA, kaiB, and kaiC and interactions among the Kai proteins are proposed to be important for circadian function in the cyanobacterium Synechococcus sp. strain PCC 7942. We have identified the histidine kinase SasA as a KaiC-interacting protein. SasA contains a KaiB-like sensory domain, which appears sufficient for interaction with KaiC. Disruption of the sasA gene lowered kaiBC expression and dramatically reduced amplitude of the kai expression rhythms while shortening the period. Accordingly, sasA disruption attenuated circadian expression patterns of all tested genes, some of which became arrhythmic. Continuous sasA overexpression eliminated circadian rhythms, whereas temporal overexpression changed the phase of kaiBC expression rhythm. Thus, SasA is a close associate of the cyanobacterial clock that is necessary to sustain robust circadian rhythms.

Adaptation, Physiological↗

PubMed2004

Structure and molecular phylogeny of sasA genes in cyanobacteria: insights into evolution of the prokaryotic circadian system.

Cyanobacteria are the simplest organisms known to have a circadian system. In addition to the three well-studied kai genes, kaiA, kaiB, and kaiC, an important element of this system is a two-component sensory transduction histidine kinase sasA. Using publicly available data of complete prokaryotic genomes, we performed structural and phylogenetic analyses of the sasA genes. Results show that this gene has a triple-domain structure, and the domains are under different selective constraints. The sasA gene originated in cyanobacteria probably through the fusion of the ancestral kaiB gene with a double-domain, two-component sensory transduction histidine kinase. The results of the phylogenetic analyses suggest that sasA emerged before the kaiA gene, about 3,000-2,500 MYA, and has evolved in parallel with the evolution of the kaiBC cluster. The observed concordant patterns of the sasA and kaiBC evolution suggest that these genes might compose an ancient KaiBC-SasA-based circadian system, without the kaiA gene, and that such a system still exists in some unicellular cyanobacteria.

Amino Acid Sequence↗

PubMedDate not supplied

Effects of gonadectomy at different ages and Sasa Health, bamboo grass leaf extract, on spontaneous motor activity in female and male mice.

To investigate the role of gonadal hormones in spontaneous motor activity and the contribution of Sasa Health, bamboo grass leaf extract, to this process, female and male ICR mice were gonadectomized at 2 (Experiment I) or 9-12 months of age (Experiment II). The spontaneous motor activity was measured 1 week and 1 month after the operation, then after a subsequent 1 month of treatment with Sasa Health administered in the drinking water. Ovariectomy caused a significant decrease in activity even after 1 week in Experiment I, but had little effect in Experiment II. In the males, a significant decrease was found only in the dark phase 1 month after castration in Experiment I, while little change in activity was induced by castration in Experiment II. Administration of Sasa Health caused an increase and decrease in the activity of the females and males, respectively, of both the control and the gonadectomized groups in Experiment I. Sasa Health had little effect on the motor activity in Experiment II. The agent acted on the plasma levels of several components modulated by gonadectomy, mostly restoring them to the control values. These findings indicate that gonadal hormones and Sasa Health influence spontaneous motor activity and plasma component levels in both sexes and have apparent sex- and age-related effects.

Aging↗

PubMed2006

A KaiC-associating SasA-RpaA two-component regulatory system as a major circadian timing mediator in cyanobacteria.

KaiA, KaiB, and KaiC clock proteins from cyanobacteria and ATP are sufficient to reconstitute the KaiC phosphorylation rhythm in vitro, whereas almost all gene promoters are under the control of the circadian clock. The mechanism by which the KaiC phosphorylation cycle drives global transcription rhythms is unknown. Here, we report that RpaA, a potential DNA-binding protein that acts as a cognate response regulator of the KaiC-interacting kinase SasA, mediates between KaiC phosphorylation and global transcription rhythms. Circadian transcription was severely attenuated in sasA (Synechococcus adaptive sensor A)- and rpaA (regulator of phycobilisome-associated)-mutant cells, and the phosphotransfer activity from SasA to RpaA changed dramatically depending on the circadian state of a coexisting Kai protein complex in vitro. We propose a model in which the SasA-RpaA two-component system mediates time signals from the enzymatic oscillator to drive genome-wide transcription rhythms in cyanobacteria. Moreover, our results indicate the presence of secondary output pathways from the clock to transcription control, suggesting that multiple pathways ensure a genome-wide circadian system.

Bacterial Proteins↗

PubMed2004

Experimental test of Hatano and Sasa's nonequilibrium steady-state equality.

Most natural processes occur far from equilibrium and cannot be treated within the framework of classical thermodynamics. In 1998, Oono and Paniconi [Oono, Y. & Paniconi, M. (1998) Prog. Theor. Phys. Suppl. 130, 29-44] proposed a general phenomenological framework, steady-state thermodynamics, encompassing nonequilibrium steady states and transitions between such states. In 2001, Hatano and Sasa [Hatano, T. & Sasa, S. (2001) Phys. Rev. Lett. 86, 3463-3466] derived a testable prediction of this theory. Specifically, they were able to show that the exponential average of Y, a quantity similar to a dissipated work, should be equal to zero for arbitrary transitions between nonequilibrium steady states, -ln = 0. We have tested this strong prediction by measuring the dissipation and fluctuations of microspheres optically driven through water. We have found that -ln approximately 0 for three different nonequilibrium systems, supporting Hatano and Sasa's proposed extension of thermodynamics to arbitrary steady states and irreversible transitions.

Models, Theoretical↗

PubMed2002

Circadian formation of clock protein complexes by KaiA, KaiB, KaiC, and SasA in cyanobacteria.

Physical interactions among clock-related proteins KaiA, KaiB, KaiC, and SasA are proposed to be important for circadian function in the cyanobacterium Synechococcus elongatus PCC 7942. Here we show that the Kai proteins and SasA form heteromultimeric protein complexes dynamically in a circadian fashion. KaiC forms protein complexes of approximately 350 and 400-600 kDa during the subjective day and night, respectively, and serves as a core of the circadian protein complexes. This change in the size of the KaiC-containing complex is accompanied by nighttime-specific interaction of KaiA and KaiB with KaiC. In various arrhythmic mutants that lack each functional Kai protein or SasA, circadian rhythms in formation of the clock protein complex are abolished, and the size of the protein complexes is dramatically affected. Thus, circadian-regulated formation of the clock protein complexes is probably a critical process in the generation of circadian rhythm in cyanobacteria.

Bacterial Proteins↗

PubMed2003

Sasa-Satsuma higher-order nonlinear Schrödinger equation and its bilinearization and multisoliton solutions.

Higher-order and multicomponent generalizations of the nonlinear Schrödinger equation are important in various applications, e.g., in optics. One of these equations, the integrable Sasa-Satsuma equation, has particularly interesting soliton solutions. Unfortunately, the construction of multisoliton solutions to this equation presents difficulties due to its complicated bilinearization. We discuss briefly some previous attempts and then give the correct bilinearization based on the interpretation of the Sasa-Satsuma equation as a reduction of the three-component Kadomtsev-Petviashvili hierarchy. In the process, we also get bilinearizations and multisoliton formulas for a two-component generalization of the Sasa-Satsuma equation (the Yajima-Oikawa-Tasgal-Potasek model), and for a (2+1)-dimensional generalization.

Journal Article↗

PubMedDate not supplied

Effects of Sasa Health, extract of bamboo grass leaves, on spontaneous mammary tumourigenesis in SHN mice.

Chronic treatment with Sasa Health, extract of bamboo grass leaves obtained by alkaline hydrolysis, in drinking water at the concentration of 0.044%-0.088% Fe-Chlorophyllin Na resulted in the significant inhibition of both development and growth of spontaneous mammary tumours in a high mammary tumour strain of SHN virgin mice. Limited treatment for 12 days in mice with palpable sizes of mammary tumours also markedly retarded the growth of the tumours. The end-bud formation and thymidylate synthetase activity of normal mammary glands were stimulated, but the formation of preneoplastic mammary hyperplastic alveolar nodules was inhibited by the treatment. Chronic ingestion of Sasa Health stimulated the excretion of urine components and decreased and increased the prolactin level and superoxide dismutase activity in serum, respectively. It showed no deleterious effects on food and water intake, body growth and any external appearance and all findings indicate that Sasa Health could be a promising agent for the protection and therapy of breast and other types of tumours.

Animals↗

PubMed1997

A validational study of the Structured Interview of Symptoms Associated with Sexual Abuse (SASA) using three samples of sexually abused, allegedly abused, and nonabused boys.

OBJECTIVE: With the rapid rise of sexual abuse allegations, there is a growing need to develop instruments to help clinicians determine the likelihood that sexual abuse has occurred. METHOD: This study evaluated the discriminant validity of a structured parent interview regarding emotional, behavioral, and physical symptoms by comparing results among three subsamples of age matched boys: 22 sexually abused boys whose perpetrator confessed, 47 boys evaluated in a sexual abuse clinic but without a history of perpetrator confession and 52 nonabused boys selected after rigorous screening. RESULTS: In comparison with the nonabused (NA) boys, the sexually abused boys were significantly more likely to demonstrate sudden emotional and behavioral changes, frequent stomach aches, more knowledge about sex and sexual activities than expected for age, unusual aggressiveness toward playmate or toy's private parts, crying easily, difficulty getting to sleep, and a change to poor school performance. The internal reliability of the SASA was determined to be .83 and scoring of an abbreviated 12-item scale demonstrated a sensitivity of 90.9% and a specificity of 88.5%. CONCLUSIONS: The findings suggest that Structured Interview of Symptoms Associated with Sexual Abuse (SASA) is an effective tool which may help in the comprehensive assessment of boys who may have been sexually abused.

Adolescent↗

PubMed1984

Deep Supercooling in Most Tissues of Wintering Sasa senanensis and Its Mechanism in Leaf Blade Tissues.

Cold hardiness of leaf blades, leaf sheaths, culms, rhizomes, and leaf buds in wintering Sasa senanensis (Fr. et Sav.) Rehder, a dwarf bamboo, was studied paying special attention to the types of resistance mechanisms which were determined with differential thermal analysis. Coincidence of LT(25) (lethal temperature at which 25% of the tissues are injured) with the initiation temperature of LTE (low temperature exotherm) suggested that all of these tissues described above owe their cold hardiness mechanism mostly to deep supercooling. Deep supercooling in leaf blades was also substantiated with microscopic observations, suggesting that the units of supercooling were minute tissues compartmentalized by longitudinal and cross veins. It was also shown that cooling rates and storage of shoots at -5 degrees C for 1 to 5 days in the ice-inoculated state did not greatly affect the supercooling ability of leaf blades. Sasa senanensis seemed to exhibit a unique strategy against prolonged subzero temperature, and its leaves would be a good system for the study on mechanisms of deep undercooling in plants.

Journal Article↗

PubMed2004

Silica deposition in relation to ageing of leaf tissues in Sasa veitchii (Carriere) Rehder (Poaceae: Bambusoideae).

BACKGROUND AND AIMS: Silica deposition is one of the important characteristics of plants in the family Poaceae. There have been many investigations into the distribution, deposition and physiological functions of silica in this family. Two hypotheses on silica deposition have been proposed based on these studies. First, that silica deposition occurs passively as a result of water uptake by plants, and second, that silica deposition is controlled positively by plants. To test these two apparently contradictory hypotheses, silica deposition in relation to the ageing of leaf tissues in Sasa veitchii was investigated. METHODS: Tissues were examined using a light microscope and a scanning electron microscope equipped with an energy dispersive X-ray microanalyser. KEY RESULTS: The deposition process differed depending on cell type. In mesophyll tissue, fusoid cells deposited large amounts of silica depending on leaf age after maturation, while chlorenchyma cells deposited little. In epidermal tissue, comprised of eight cell types, only silica cells deposited large amounts of silica during the leaf's developmental process and none after maturation. Bulliform cells, micro-hairs and prickle hairs deposited silica densely and continuously after leaf maturation. Cork cells, guard cells, long cells and subsidiary cells deposited silica at low levels. CONCLUSIONS: The significance of these observations is discussed in relation to the two hypotheses proposed for silica deposition in Poaceae. The results of the present study clearly indicate that both hypotheses are compatible with each other dependent on cell types.

Microscopy, Electron, Scanning↗

PubMed2006

Effects of resource heterogeneity on nitrogen translocation within clonal fragments of Sasa palmata: an isotopic (15N) assessment.

BACKGROUND AND AIMS: Clonal fragments of the rhizomatous dwarf bamboo Sasa palmata, which widely predominates in temperate regions of Japan, were grown under heterogeneous resource conditions such as gap understories or nutrient-patchy grassland. Clonal fragments develop multiple ramets with long rhizomes and appear to be physiologically integrated by the translocation of assimilates. The glasshouse experiment reported here was designed to clarify the mechanisms of physiological integration of nitrogen more precisely. METHODS: To assess how resource conditions influence the amount of nitrogen translocation, and which organ acts as the strongest sink, two experiments were conducted that traced movement of 15N label between interconnected pairs of ramets to compare homogeneous and heterogeneous light and soil nitrogen conditions. KEY RESULTS: The amount of 15N translocated to leaves was between 9% and 11% greater in high-N and high-light ramets in the heterogeneous compared with homogeneous treatments. Under heterogeneous soil nitrogen conditions, translocation increased from individual ramets in resource-rich patches to ramets in resource-poor patches, while the reverse was true under heterogeneous light environments, reflecting differences in the positions of leaves that act as the strongest sinks. Neither the mass increments nor the total mass of clonal fragments was significantly affected by heterogeneity of either light or nutrients, possibly because the experimental period was too short for differences to manifest themselves. CONCLUSIONS: This study clearly demonstrated that nitrogen is readily translocated between ramets, particularly under heterogeneous resource conditions. The translocation patterns were governed by functional 'division of labour' mechanisms that resulted in net nitrogen movement from understory sites to gaps, thereby enhancing the carbon acquisition of the whole fragment. Thus, physiological integration may provide benefits for S. palmata when it is growing under heterogeneous conditions in which there are deficits of certain environmental resources.

Data Interpretation, Statistical↗

PubMed1987

Sporobolomyces inositophilus, a new species of ballistosporous yeast isolated from a dead leaf of Sasa sp. in Japan.

A new species of ballistosporous yeast, Sporobolomyces inositophilus was isolated from a dead leaf of Sasa sp. collected at a mountain in Japan. This yeast is assumed to have a close relationship to Sporobolomyces singularis since it produces bilaterally symmetrical ballistospores and pale-coloured colonies and resembles Sporobolomyces singularis in these respects. These two species differ from typical species of Sporobolomyces and seem to constitute a natural taxonomic group.

Japan↗

PubMed2000

Clonal structure in a dwarf bamboo (Sasa senanensis) population inferred from amplified fragment length polymorphism (AFLP) fingerprints.

Amplified fragment length polymorphism (AFLP) fingerprints were used to reveal clonal structure of a dense population of dwarf bamboo, Sasa senanensis, in a 10-ha study plot at Sugadaira Montane Research Center, University of Tsukuba, Nagano, Japan. We generated AFLP fingerprints for 51 leaf samples, collected at 50 m intervals, using three selective primer pairs. A total of 135-166 fragments were detected per sample, and 22 different fingerprints were identified based on 24-83 differing fragments. Our results demonstrate that the S. senanensis population in our plot consists of at least 22 clones and that the largest single clone occurs over a distance of about 300 m. Furthermore, the clone distribution pattern implies a relationship between site quality and clonal structure.

Clone Cells↗

PubMed2002

Silica accumulation in long-lived leaves of Sasa veitchii (Carrière) Rehder (Poaceae-Bambusoideae).

Silica accumulation in long-lived leaves of Sasa veitchii was investigated using the molybdenum blue method. In general, silica accumulation was rapid during spring and summer, and slow during winter. The leaves continuously accumulate silica throughout their life. The significance of these observations is discussed in relation to two hypotheses for silica accumulation in plants: (1) that silica accumulation is a result of water consumption by the plant: and (2) that silica is actively accumulated to protect the plant. The results of the present study support the former hypothesis.

Plant Leaves↗

PubMed1999

Inhibitory effects of Sasa senanensis Rehder extract (SE) on calcium-ionophore A23187-induced histamine release from rat peritoneal exudate cells.

The effects of Sasa senanensis Rehder extract (SE) by alkaline hydrolysis on histamine release from rat peritoneal exudate cells (PECs) were examined. Preincubation with SE for 5 min suppressed calcium-ionophore A23187-induced histamine release in a concentration-dependent manner. A23187 evoked a quick increase in cytoplasmic free calcium ([Ca2+]i) levels in the presence of extracellular calcium. Preincubation with SE also had an inhibitory effect on calcium influx increases induced by A23187. These results indicate that SE prevents degranulation from rat PECs by inhibiting [Ca2+]i level elevation.

Animals↗