Sex steroids in intersexual fishes

Studies of thein vitro gonadal steroidogenesis in intersexual fishes, using labelled testosterone as precursor, showed large species variation. The protogynousMonopterus albus produced predominantly 5α-reduced metabolites while the protandrousRhabdosargus sarba produced mainly 5β-reduced products. Both fishes synthesized 11-oxotestosterone; the synthesis of which appeared to mediate mainly through adrenosterone inM. albus butvia 11β-hydroxytestosterone inR. sarba. When the plasma levels of androstenedione, testosterone, 11-oxotestosterone, 11β-hydroxytestosterone, estrone and 17β-estradiol among the male, intersexual and female phase of the same species were compared, available data showed that either there was no obvious difference among the different sexual phases or the differences could be accounted for by the seasonal reproductive activities of the animal. Except for androstenedione, there are no marked changes in plasma testosterone, 11-oxotestosterone, 11β-hydroxytestosterone, estrone and 17β-estradiol levels in the intersexual phase compared with the female and male, it is unlikely that these classical sex steroids act as a primary trigger of natural sex reversal in these fishes; the role of androstenedione awaits further elucidation. Department of Zoology, University of Hong Kong     

Nudging fisheries and aquaculture research towards food systems

Food system is a powerful concept for understanding and responding to nutrition and sustainability challenges. Food systems integrate social, economic, environmental and health aspects of food production through to consumption. Aquatic foods are an essential part of food systems providing an accessible source of nutrition for millions of people. Yet, it is unclear to what degree research across diverse disciplines concerning aquatic foods has engaged food systems, and the value this concept has added. We conducted a systematic review of fisheries, aquaculture and aquatic food literature (2017–2019) to determine the following: the characteristics of this research; the food systems components and interrelations with which research engaged; and the insights generated on nutrition, justice, sustainability and climate change. Sixty five of the 88 reviewed articles focussed on production and supply chains, with 23 considering human nutrition. Only 13% of studies examined low- and middle-income countries that are most vulnerable to undernutrition. One third of articles looked beyond finfish to other aquatic foods, which illuminated values of local knowledge systems and diverse foods for nutrition. When aggregated, reviewed articles examined the full range of food system drivers—biophysical and environmental (34%), demographic (24%) and socio-cultural (27%)—but rarely examined interactions between drivers. Future research that examines a diversity of species in diets, system-wide flows of nutrients, trade-offs amongst objectives, and the nutritional needs of vulnerable social groups would be nudging closer to the ambitions of the food systems concept, which is necessary to address the global challenges of equity, nutrition and sustainability.     

Impact of tillage, stubble management and crop rotation on nematode populations in a long-term field experiment

The population abundance of free-living and plant-parasitic nematodes was investigated in a long-term rotation/tillage/stubble management experiment at Wagga Wagga Agricultural Institute, New South Wales (NSW), Australia. The treatments were a combination of two crop rotations: wheat (Triticum aestivum)–wheat and wheat–lupin (Lupinus angustifolius); two tillage systems: conventional cultivation (CC) and direct drill (DD); and two stubble management practices: stubble retention (SR) and stubble burnt (SB). Plots of one of the wheat–wheat treatments received urea at 100 kg N ha⁻¹ during the cropping season. Soil samples from 0–5 and 5–10 cm depths were collected in September (maximum tillering), October (flowering) and December (after harvest), 2001, to analyse nematode abundance. Soil collected in September was also analysed for concentrations of total and labile C, and pH levels.Three nematode trophic groups, namely bacteria-feeders (primarily Rhabditidae), omnivores (primarily Dorylaimidae excluding plant-parasites and predators) and plant-parasites (Pratylenchus spp. and Paratylenchus spp.) were recorded in each soil sample. Of them, bacteria-feeders (53–99%, population range 933–2750 kg⁻¹ soil) dominated in all soil samples. There was no difference in nematode abundance and community composition between the 0–5 cm and 5–10 cm layers of soil. The mean population of free-living and plant-parasitic nematodes varied significantly between the treatments in all sampling months. In most cases, total free-living nematode densities (Rhabditidae and Dorylaimidae) were significantly (P < 0.001) greater in wheat–lupin rotation than the wheat–wheat rotation irrespective of tillage and stubble management practices. In contrast, a greater population of plant-parasitic nematodes was recorded from plots with wheat–wheat than the wheat–lupin rotation. For treatments with wheat–wheat, total plant-parasitic nematode (Pratylenchus spp. and Paratylenchus spp.) densities were greater in plots without N-fertiliser (295–741 kg⁻¹ soil) than the plots with N-fertiliser (14–158 kg⁻¹ soil).Tillage practices had significant (P < 0.05) effects mostly on the population densities of plant-parasitic nematodes while stubble management had significant effects (P < 0.05) on free-living nematodes. However, interaction effects of tillage and stubble were significant (P < 0.01) for the population densities of free-living nematodes only. Population of Rhabditidae was significantly higher in conventional cultivated plots (7244 kg⁻¹ soil) than the direct drilled (3981 kg⁻¹ soil) plots under stubble retention. In contrast, plots with direct drill and stubble burnt had significantly higher populations of Dorylaimidae than the conventional cultivation with similar stubble management practice. No correlations between abundance of free-living nematodes, and concentration of total C and labile C in soil were observed in this study. These results showed that stubble retention contributed for enormous population density of free-living (beneficial) nematodes while conventional cultivation, irrespective of stubble management, contributed for suppressing plant-parasitic nematodes.     

Short-term responses of two contrasting species of earthworms in an agricultural soil amended with coal fly-ash

With the renewed interest in the use of coal fly-ash for amendment of agricultural soils in Australia, we assessed how earthworms, as indicators of soil health, responded to this ameliorant. We assessed survival, weight, burrowing and elemental concentrations for earthworms of a native unnamed Megascolecid species and of exotic Aporrectodea trapezoides in intact soil cores treated with an alkaline fly-ash at rates equivalent to 0, 5 and 25 t/ha over 6 weeks. Fly-ash did not affect survival, growth, number of burrows created or phosphorus solubilisation. Transfer of the earthworms to the new environment having vastly different pH from where they were collected, and possibly overcrowding, caused mortality in the soil cores for all treatments. A. trapezoides that had smaller individuals suffered mortality of 12% compared with 23% for the larger earthworms of Megascolecids. Earthworms of Megascolecids each increased their weight by 0.24g (25% of their original weight) while those of A. trapezoides lost 0.18g each (21% of their original weight). The difference in growth between the two earthworms was associated with grazing habit and probably with the large difference in the pH between source soil and that of the core soil. Megascolecids appeared to minimize grazing on ash-tainted soil and so ingested less Zn, which was more abundant in the fly-ash than in the soil, compared with A. trapezoides that had elevated concentration of this metal. Extractable P in the soil was increased with both species of earthworms, more so with the exotic species that solubilized 11% more P than the native Megascolecids. The benign influence of fly-ash on survival and growth of worms was associated with the pH of soil remaining unchanged during the six weeks of incubation.     

Nonenzymatic antioxidant activity of four organosulfur compounds derived from garlic

The nonenzymatic antioxidant activity of diallyl sulfide (DAS), diallyl disulfide (DADS), S-ethyl cysteine (SEC), and N-acetyl cysteine (NAC) in the liposome system was examined. The antioxidant protection from these organosulfur agents was concentration dependent (p < 0.05). SEC and NAC showed significantly lower lipophilicity and greater reducing power than DAS and DADS (p < 0.05). Greater antioxidant protection was presented in the combinations of alpha-tocopherol with four organosulfur agents than alpha-tocopherol treatment alone (p < 0.05), and SEC and NAC showed greater sparing effects on alpha-tocopherol (p < 0.05). Four organosulfur agents lost antioxidant activity when the temperature was 65 degrees C (p < 0.05). At pH 2.5 and 10, DAS and DADS still showed antioxidant activity (p < 0.05). On the basis of the observed nonenzymatic antioxidant protection, these organosulfur compounds are potent agents for enhancing lipid stability.     

Sequential extraction and quantitative recovery of gliadins, glutenins, and other proteins from small samples of wheat flour

Methods to sequentially extract and fractionate wheat flour proteins were evaluated to reliably quantify gliadins, glutenins, and albumins/globulins in single flour samples. Compositions of the resulting protein fractions were analyzed by RP-HPLC combined with SDS-PAGE. Unknown proteins were identified by mass spectrometry or N-terminal sequencing. The best separation and recovery of discrete albumin/globulin, gliadin, and glutenin fractions from the same flour sample was achieved by extraction with 0.3 M NaI in 7.5% 1-propanol followed by 2% SDS, 25 mM DTT in 25 mM TRIS, pH 8.0, and precipitation of the solubilized proteins with ammonium acetate/methanol followed by acetone. Average flour composition for the variety Butte86 was 10% albumin/globulin, 40% gliadin, and 48% glutenin. This method should be useful for determining flour composition in diverse samples and evaluating relationships between proteins and end-use functionality.     

2001-2007年湖北省耕地安全演化分析

为了研究湖北省耕地资源安全状况,从耕地的数量、质量以及耕地生态3个方面构建了耕地安全演化评价体系,应用信息熵模型评价了湖北省2001-2007年耕地安全系统的演化状况。结果表明：湖北省的耕地系统从2001年的0.12088,变为2007年的-0.22354,其中耕地的数量、质量及生态分别从2001年的0.10358、-0.00286、0.02015变为2007年的-0.22273、-0.00078、-0.00002。说明湖北省耕地安全向着有序的方向发展,且有序度不断增强。但仍存在不稳定因素,主要为人均耕地减少、城市快速扩张、生态环境恶化等。因此,应加大耕地整理力度,提高城市土地集约度,同时运用经济、法律、政策手段提高耕地质量,改进耕地生态。     

Epitaxial cuprate superconductor/ferroelectric heterostructures

Thin-film heterostructures of Bi(4)Ti(3)O(12)Bi(2)Sr(2)CuO(6+x), have been grown on single crystals of SrTiO(3), LaAlO(3), and MgAl(2)O(4) by pulsed laser deposition. X-ray diffraction studies show the presence of c-axis orientation only; Rutherford backscattering experiments show the composition to be close to the nominal stoichiometry. The films are ferroelectric and exhibit a symmetric hysteresis loop. The remanent polarization was 1.0 microcoulomb per square centimeter, and the coercive field was 2.0 x 10(5) volts per centimeter. Similar results were obtained with YBa(2)Cu(3)O(7-x) and Bi(2)Sr(2)CaCu(2)O(8+x), and single-crystal Bi(2)Sr(2)CuO(6+x)as the bottom electrodes. These films look promising for use as novel, lattice-matched, epitaxial ferroelectric film/electrode heterostructures in nonvolatile memory applications.