A stable isotope trace method to measure silicic acid uptake by marine phytoplankton.

A tracer method is described that uses the stable isotope ³⁰Si to measure rates of silicic acid uptake by diatom cultures and natural populations of marine phytoplankton. The method involves (i) incubation of organisms requiring silicic acid for growth in the presence of ³⁰Si-labeled silicic acid, (ii) collection of the resulting particulate silicon, (iii) conversion of the particulate silicon to BaSiF₆, (iv) determination of the ³⁰Si content of BaSiF₆ by solid sample mass spectrometry, and (v) calculation of the uptake rate from the ³⁰Si enrichment of the particulate matter during the incubation. The maximum overall error in the uptake rate measurement is ±10%.     

Enzymes of vitamin B6 degradation. Purification and properties of 5-pyridoxic-acid oxygenase from Arthrobacter sp

5-Pyridoxic-acid oxygenase, a cytoplasmic enzyme formed when Arthrobacter Cr-7 is grown with pyridoxine as a sole source of carbon and nitrogen, was purified about 190-fold to homogeneity from fully induced cells. The enzyme catalyzes Reaction a, (Formula: see text) the essential ring-opening step in the degradation of pyridoxine, and provides a second example of an FAD-dependent oxygenase that adds both two hydrogen and two oxygen atoms to its substrate. 5-Pyridoxic-acid oxygenase has an isoelectric point of 4.6, functions optimally between pH 7 and 8, appears to contain a single subunit of Mr = 51,000 and one FAD (but no iron) per subunit, and is readily resolved by precipitation with ammonium sulfate at pH 3.0. FMN and riboflavin do not replace FAD as coenzyme, but their presence enhances a normally minor side reaction (Reaction b) NAD(P)H + H+ + O2----NAD(P)+ + H2O2 (b) catalyzed by the holoenzyme. Reaction b also is enhanced when the poorly utilized analogues, 3-hydroxy-2-methylpyridine-5-carboxylic acid or NADH, replace 5-pyridoxic acid or NADPH, respectively, as substrates in Reaction a. Each of the enzymes required in two different pathways for degradation of pyridoxine to anabolic intermediates has now been studied. A comparison of these two pathways and their enzymes is provided.     

How Can the Eco‐efficiency of a Region be Measured and Monitored?

The concept of eco-efficiency is commonly referred to as a business link to sustainable development. In this article, ecoefficiency is examined at a regional level as an approach to promoting the competitiveness of economic activities in the Finnish Kymenlaakso region and mitigating their harmful impacts on the environment. The aim is to develop appropriate indicators for monitoring changes in the eco-efficiency of the region. A starting point is to produce indicators for the environmental and economic dimensions of regional development and use them for measuring regional eco-efficiency. The environmental impact indicators are based on a life-cycle assessment method, producing different types of environmental impact indicators: pressure indicators (e.g., emissions of CO₂), impact category indicators (e.g., CO₂ equivalents in the case of climate change), and a total impact indicator (aggregating different impact category indicator results into a single value). Environmental impact indicators based on direct material input, total material input, and total material requirement of the Kymenlaakso region are also assessed. The economic indicators used are the gross domestic product, the value added, and the output of the main economic sectors of Kymenlaakso. In the eco-efficiency assessment, the economic and environmental impact indicators are monitored in the same graph. In a few cases eco-efficiency ratios can also be calculated (the economic indicators are divided by the environmental indicators). Output (= value added + intermediate consumption) is used as an economic indicator related to the environmental impact indicators, which also cover the upstream processes of the region's activities. In the article, we also discuss the strengths and weaknesses of using the different environmental impact indicators.     

Dehydroheliamine,a trace alkaloid from the saguaro,Carnegiea gigantea (cactaceae)

Extraction of Carnegiea gigantea yielded a new 3,4-dihydroisoquinoline alkaloid, dehydroheliamine; the structure was confirmed by synthesis.     

How costly is clutch formation in the Audouin's Gull Larus audouinii?

During the Audouin's Gull's breeding season at the Ebro Delta in 1993, 24 fresh eggs from eight three-egg clutches (modal clutch-size) were collected at the peak of the laying period. Eggs were processed to obtain formalin-fixed yolks, which were halved and stained using the potassium dichromate method. Digitized images of the yolks were examined to assess the daily rates of yolk deposition. We used these data in combination with egg compositional analysis to build a model of energy demands during the formation of an average clutch in Audouin's Gull. To show how the different parameters of clutch formation affect the daily energy investment peak, we performed a simulation analysis in which the rapid yolk development (RYD) period, the follicle triggering interval (FTI), the laying interval (LI) and the albumen synthesis period (ASP) were allowed to vary simultaneously. In our sample, the mean RYD period was seven days with a range from six to eight days. There were no significant differences in yolk volume among eggs in a clutch, but albumen volume was significantly smaller in third eggs. According to our model the albumen synthesis of the a-egg coincides with the energy demand peak for clutch formation. This peak represents an increase by ca. 42% in female energy requirements. Values obtained from the simulation analysis showed that only the ASP of the a-egg and the RYD durations of the second and third follicles produced noticeable reductions in peak energy investment. We predict that in gulls, whose laying intervals seem to be kept constant, significant increases of the durations of the RYD periods of second and third eggs, or even significant reductions of yolk size of these eggs, may operate simultaneously to match the energy demands during clutch formation to the prevailing food conditions.     

Identification, purification, and characterization of phosphotyrosine-specific protein phosphatases from cultured chicken embryo fibroblasts.

Tyrosine phosphorylation catalyzed by a unique class of protein kinases is an important process in both normal cell proliferation and oncogenic transformation. In this study, phosphoprotein phosphatases specific for the dephosphorylation of phosphotyrosine residues were partially purified from secondary chicken embryo fibroblasts, using 32P-labeled immunoglobulin G phosphorylated by pp60src as substrate. Crude cell extracts contained ca. 70% of the activity in the soluble form and ca. 30% associated with a crude membrane fraction. The soluble activity was purified by using DEAE-cellulose and carboxymethyl cellulose column chromatography and gel filtration, and at least three enzyme species of apparent Mr 55,000 (pTPI), 50,000 (pTPII), and 95,000 (pTPIII)--comprising ca. 20, 45, and 35%, respectively, of the total activity--were resolved. All three enzymes possessed somewhat similar properties. They had a pH optimum of about 7.4, they were inhibited by Zn2+, vanadate, ATP, and ADP, and they were unaffected by divalent metal cations, EDTA, and F- under standard assay conditions employing a physiological ionic strength. These properties suggest that they represent a class of enzymes distinct from well-known phosphoseryl-phosphothreonyl-protein phosphatases and that dephosphorylation of phosphotyrosine-containing proteins may be carried out by a unique family of phosphoprotein phosphatases. Transformation by Rous sarcoma virus resulted in a small increase in phosphotyrosyl-protein phosphatase activity.     

Reaction mechanism of surfactant‐sensitized chemiluminescence of bis(2,4,6‐trichlorophyenyl) oxalate and hydrogen peroxide induced by gold nanoparticles

The chemiluminescence (CL) of bis(2,4,6‐trichlorophyenyl) oxalate with hydrogen peroxide in the present of cationic surfactant and gold nanoparticles was studied. The CL emission was obviously enhanced in the presence of surfactant at a suitable concentration, with a synergetic catalysis effect exhibited. Different sizes of gold nanoparticles (15 and 50 nm) showed different effects on CL intensity. Mechanisms of the CL reaction and sensitization effect are discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Pre‐copulation intervals,copulation frequencies,and initial progeny sex ratios in two biotypes of whitefly,Bemisia tabaci

The whitefly Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) is a species complex, and its systematic classification requires controlled crossing experiments among its genetic groups. Accurate information on pre‐copulation intervals, copulation frequencies, and initial frequency of egg fertilization of newly emerged adults is critical for designing procedures for collecting the virgin adults necessary for these experiments. In the literature, considerable variation is reported between B. tabaci populations, with respect to the length of the pre‐copulation interval and the initial frequency of egg fertilization. Here, we used a video‐recording method to observe continuously the copulation behaviour of the Mediterranean/Asia Minor/Africa (B biotype) and the Asia II (ZHJ1 biotype) groups of B. tabaci. We also recorded the initial frequency of egg fertilization, as determined by the sex of the progeny. When adults were caged in female–male pairs on leaves of cotton plants, the earliest copulation events occurred 2–6 h after emergence; at 12 h after emergence 56–84% of the females had copulated at least once, and nearly all (92–100%) had copulated at least once by 36 h after emergence. Both females and males copulated repeatedly. Approximately 80 and 20% of copulation events occurred during the photophase and scotophase, respectively. By 72 h post‐emergence, the females of the B and ZHJ1 biotypes had copulated on average 6.1 and 3.9 times, respectively. When adults were caged in groups on plants 1–13 h after emergence, 30–35% of the eggs deposited during this period were fertilized, and approximately 90% of females were fertilized by the end of the 13 h. Although timing of copulation differed in detail between the two genetic groups, the results demonstrate that B. tabaci adults can start to copulate as early as 2–6 h post‐emergence and the majority of females can become fertilized on the day that they emerge.