Experiences with the Irrigation Management Game

The Irrigation Management Game is a role playing exercise for the training of personnel involved in the management and operation of irrigation schemes. The paper describes the author's experience in developing and using this management game, and gives advice on the development of such training material.     

Composition of saturnian stream particles

During Cassini's approach to Saturn, the Cosmic Dust Analyser (CDA) discovered streams of tiny (less than 20 nanometers) high-velocity (approximately 100 kilometers per second) dust particles escaping from the saturnian system. A fraction of these impactors originated from the outskirts of Saturn's dense A ring. The CDA time-of-flight mass spectrometer recorded 584 mass spectra from the stream particles. The particles consist predominantly of oxygen, silicon, and iron, with some evidence of water ice, ammonium, and perhaps carbon. The stream particles primarily consist of silicate materials, and this implies that the particles are impurities from the icy ring material rather than the ice particles themselves.     

Origins of bilateral symmetry: Hox and dpp expression in a sea anemone

Over 99% of modern animals are members of the evolutionary lineage Bilateria. The evolutionary success of Bilateria is credited partly to the origin of bilateral symmetry. Although animals of the phylum Cnidaria are not within the Bilateria, some representatives, such as the sea anemone Nematostella vectensis, exhibit bilateral symmetry. We show that Nematostella uses homologous genes to achieve bilateral symmetry: Multiple Hox genes are expressed in a staggered fashion along its primary body axis, and the transforming growth factor-beta gene decapentaplegic (dpp) is expressed in an asymmetric fashion about its secondary body axis. These data suggest that bilateral symmetry arose before the evolutionary split of Cnidaria and Bilateria.     

Low-dose cyclophosphamide selectively decreases regulatory T cells and inhibits angiogenesis in dogs with soft tissue sarcoma

Background: Low‐dose, continuous (metronomic) chemotherapy improves tumor control by inhibiting tumor angiogenesis and suppressing regulatory T cells (Treg) in mice and humans. The effects of metronomic chemotherapy on Treg and tumor angiogenesis in dogs has not been investigated previously. Objective: To determine whether metronomic cyclophosphamide (CYC) therapy decreases Treg or exhibits antiangiogenic activity or both in dogs with soft tissue sarcoma (STS). We hypothesized that Treg numbers would be increased in dogs with STS and that continuous dosing of CYC would decrease Treg in a dose‐dependent manner, as well as exhibit antiangiogenic activity. Animals: Eleven client‐owned dogs with grade I or II STS. Twenty‐one healthy dogs were used as controls. Methods: Prospective, open, clinical trial. Dogs with STS were enrolled in 2 dose cohorts and administered CYC at 12.5 or 15 mg/m² PO once daily for 28 days. Whole blood and tumor biopsy specimens were obtained on days 0, 14, and 28 to assess changes in T lymphocyte subsets by flow cytometry and tumor microvessel density (MVD), respectively. Results: Administration of CYC at 12.5 mg/m²/d significantly decreased the number of Treg from days 0 to 28, but there was no change in the percentage of Treg or tumor MVD. In dogs that received CYC at 15.0 mg/m²/d, both the number and percent of Treg as well as tumor MVD were significantly decreased over 28 days. Conclusions: CYC administered at 15 mg/m²/d should be used in further studies examining the antitumor properties of low‐dose CYC in dogs.     

Substructure of certain cytoplasmic microtubules: an electron microscopic study

egatively stained cytoplasmic microtubules of lung-fluke sperm show a helical structure that is not found in peripheral doublet tubules of axial units. In transverse sections, the wall of such microtubules appears to comprise about eight subunits.     

Plant growth,phosphorus nutrition,and acid phosphatase enzyme activity in three tomato cultivars grown hydroponically at different zinc concentrations

Three tomato cvs., Blizzard, Liberto, and Calypso, were grown hydroponically in a controlled temperature (C.T.) room for six weeks at three zinc (Zn) concentrations (0.01, 0.5, and 5.0 mg Zn L^‐1) in the nutrient solution. There were significant reductions in the dry matter and chlorophyll contents of all three cultivars grown at both low (0.01 mg L^‐1) and high (5 mg L^‐1) Zn as compared to 0.5 mg Zn L^‐1. The concentration of Zn at 0.01 mg L^‐1 was not sufficient to provide for optimal plant growth, while 5 mg Zn L^‐1 in the nutrient solution was detrimental to plant growth for all three cultivars. The best results for all parameters tested were for the plants grown at 0.5 mg Zn L^‐1. The concentration of phosphorus (P) was at an excess level in leaves of plants grown in 0.01 mg Zn L^‐1, while it was deficient in the 5 mg Zn L^‐1 treatment. Acid Phosphatase Enzyme [EC.3.1.3.2.] (APE) activity was significantly higher in both the leaves and roots of P‐deficient plants, i.e., plants receiving high (5 mg L^‐1) Zn. Acid Phosphatase Enzyme activity was slightly higher in the mature leaves than those in developing leaves, where P concentration was higher. Concentration of P and, in particular Zn, increased in the roots with increasing Zn in the nutrient solution. The APE activity increased in the roots of P‐deficient plants receiving high Zn (5 mg L^‐1).