Spatial and temporal distribution of geminiviruses in leafhoppers of the genus cicadulina monitored by conventional and quantitative polymerase chain reaction

ABSTRACT Spatial and temporal distribution of Maize streak virus (MSV, family Geminiviridae, genus Mastrevirus) was monitored in the vector species Cicadulina mbila and the nonvector species C. china? using conventional and real-time quantitative polymerase chain reaction. Sustained feeding on MSV-infected plants showed that virus accumulation reaches a maximum in C. china?, but not in C. mbila. After a 3-day acquisition access feeding period (AAP), MSV was detected in the gut, the hemolymph, and the head of C. mbila, but only in the gut of C. china?. Similarly, Digitaria streak virus (genus Mastrevirus), which is not transmitted by either of the two species, was only detected in the gut. MSV was detected in the hemolymph of C. mbila 3 h after the beginning of the AAP. Although viral DNA progressively decreases in the vector and nonvector species after a 3-day AAP, MSV DNA remained stable in the salivary glands of C. mbila.     

The Effects of Growth Factor on Testicular Germ Cell Apoptosis in the Stallion

Apoptosis is necessary for both initiation and control of spermatogenesis; however, an increase in apoptosis can lead to subfertility/infertility in stallions, causing substantial financial loss in the equine industry. The ability of stem cell factor (SCF), leukemia-inhibiting factor (LIF), granulocyte–macrophage colony-stimulating factor (GM-CSF), and estradiol (E₂), alone or in combination, to prevent apoptosis of germ cells in short-term equine testicular cultures was examined. Testicular tissue was sectioned into approximately 2-mm cubes and placed in media-filled culture chambers. Concentrations of SCF (100 ng/mL), LIF (10 ng/mL), GM-CSF (5 ng/mL), and E₂ (10⁻⁹ mol/l) were added alone or in combination to each well. After 6 hours in culture, the tissue was fixed and immunohistochemically (terminal deoxynucleotidyl transferase-mediated nick-end labeling; TUNEL) stained for apoptosis detection. Apoptotic cells per 100 Sertoli cell nuclei within seminiferous tubules were counted until the 500^th Sertoli cell nuclei was reached. This counting procedure was used for each slide. An analysis of variance (ANOVA) with a Tukey's test was used to compare apoptotic rates. In comparison with the control, GM-CSF alone lowered apoptosis by 34.77%. GM-CSF–treated tissue combined with SCF and LIF as well as GM-CSF combined with SCF, LIF, and E₂ reduced apoptosis when compared with the control (37.45% and 44.40%, respectively) or other treatment combinations. GM-CSF alone reduced apoptosis; results suggest possible synergy for the combinations of SCF and LIF with GM-CSF and for E₂ with SCF, LIF, and GM-CSF.     

In vitro modulation of reactive oxygen and nitrogen intermediate (ROI/RNI) production in Crassostrea gigas hemocytes

Bivalve hemocyte competence has been measured by quantifying functional characteristics, including reactive oxygen intermediate (ROI) production after activation with zymosan or phorbol myristate acetate (PMA). However, untreated oyster hemocytes also produce ROI and RNI (reactive nitrogen intermediates) after bleeding even if not stimulated by zymosan or PMA. Extensive investigation of this parameter by flow cytometry showed that, in vitro, ROI/RNI production by untreated hemocytes maintained in seawater appeared to be independent of both bacterial burden in the serum and non-self particle phagocytosis. ROI/RNI production in granulocytes was higher than in hyalinocytes and could be intensified when activated by zymosan but not by PMA. Both cell types used NADPH-oxidase- and NO-synthase-like pathways to produce these molecules; the NO-synthase pathway seemed relatively more dominant in hyalinocytes and NADPH-oxidase appeared more effective in granulocytes. These results provide new insights for interpreting the modulation of ROI/RNI production by untreated hemocytes shown by other studies, relative to environmental conditions or physiological status of the oysters.     

Effects of natural barriers on the spillover of a marine mollusc: implications for fisheries reserves

• 1. The movement of organisms and dispersal of propagules is fundamental to the maintenance of populations over time. However, the existence of barriers, created through the spatial configuration of habitats, may significantly affect dispersal patterns and thus influence community dynamics and resource sustainability.
• 2. Within marine environments unstructured or open habitats may form partial or complete ecological barriers due to elevated risk of predation or physical stresses associated with them. The existence and effects of such barriers may be of particular importance when considering the establishment of marine protected areas with a fisheries enhancement focus.
• 3. In this paper, the spillover of post‐settlement queen conch (Strombus gigas) from a protected area in the Turks and Caicos Islands is investigated. It is hypothesized that the reserve boundaries overlap with a series of shallow, sand habitats that effectively enclose the protected population, reducing the spillover of conch into the adjacent fished areas.
• 4. To test this, density gradient maps for juvenile and adult conch populations were constructed using underwater visual survey data at 68 sites within and surrounding the protected area. These maps illustrate very low densities coinciding with poor, shallow sand habitats along the two marine boundaries of the reserve where spillover is expected to take place.
• 5. These sand habitats are thought to create ecological barriers to a slow, sedentary gastropod largely due to their shallowness (physical stresses of solar exposure or anoxia) and lack of food reducing the tendency of individuals to move across these areas, despite the 10‐times higher density of adult queen conch observed in the protected area compared with outside.

Copyright © 2003 John Wiley & Sons, Ltd.     

Diagnosis and management of small-scale fisheries in developing countries

Small‐scale fisheries (SSF) make important but undervalued contributions to the economies of some of the world’s poorest countries. They also provide much of the animal protein needed by societies in which food security remains a pressing issue. Assessment and management of these fisheries is usually inadequate or absent and they continue to fall short of their potential as engines for development and social change. In this study, we bring together existing theory and methods to suggest a general scheme for diagnosing and managing SSF. This approach can be adapted to accommodate the diversity of these fisheries in the developing world. Many threats and solutions to the problems that beset SSF come from outside the domain of the fishery. Significant improvements in prospects for fisheries will require major changes in societal priorities and values, with consequent improvements in policy and governance. Changes in development policy and science reflect these imperatives but there remains a need for intra‐sectoral management that builds resilience and reduces vulnerability to those forces beyond the influence of small‐scale fishers.     

Plant growth-promoting bacteria in the rhizo- and endosphere of plants: Their role, colonization, mechanisms involved and prospects for utilization

In both managed and natural ecosystems, beneficial plant-associated bacteria play a key role in supporting and/or increasing plant health and growth. Plant growth-promoting bacteria (PGPB) can be applied in agricultural production or for the phytoremediation of pollutants. However, because of their capacity to confer plant beneficial effects, efficient colonization of the plant environment is of utmost importance. The majority of plant-associated bacteria derives from the soil environment. They may migrate to the rhizosphere and subsequently the rhizoplane of their hosts before they are able to show beneficial effects. Some rhizoplane colonizing bacteria can also penetrate plant roots, and some strains may move to aerial plant parts, with a decreasing bacterial density in comparison to rhizosphere or root colonizing populations. A better understanding on colonization processes has been obtained mostly by microscopic visualisation as well as by analysing the characteristics of mutants carrying disfunctional genes potentially involved in colonization. In this review we describe the individual steps of plant colonization and survey the known mechanisms responsible for rhizosphere and endophytic competence. The understanding of colonization processes is important to better predict how bacteria interact with plants and whether they are likely to establish themselves in the plant environment after field application as biofertilisers or biocontrol agents.