Plasma kinetics of injected recombinant chicken somatotropin in juvenile coho salmon (Oncorhynchus kisutch) using a homologous radioimmunoassay

Although somatotropins are potent growth promoters in salmonids, there is little information on how these proteins are metabolized by poikilotherms. In the present study, the plasma uptake and clearance rates of recombinant chicken somatotropin (rcGH) were investigated in juvenile coho salmon (Oncorhynchus kisutch). Two doses of rcGH were administered by intraperitoneal (ip) or intramuscular (im) injection and blood samples were collected over a period of 32 days. A specific radioimmunoassay was validated and used to discriminate rcGH from endogenous somatotropin. Plasma rcGH concentration was proportional to the dose delivered, but uptake and clearance rates were found to be independent of dose (between 0.5 and 5.0 g/g). Absorption of rcGH into the plasma was faster from the im site, but the peak levels attained were similar after im or ip treatment (using the same dose) as was area under the curve. Plasma half-life was calculated from the declining phase of the uptake/clearance profile but the results were biased by the concurrent uptake of rcGH from the ip or im reservoir of material, resulting in an over-estimation of the true half-life value. Effective treatment doses and intervals are discussed.     

Canopy-microclimate effects on the antagonism between Trichoderma stromaticum and Moniliophthora perniciosa in shaded cacao

The collective impact of several environmental factors on the biocontrol activity of Trichoderma stromaticum ( Ts ) against Moniliophthora perniciosa ( Mp ), the cause of cacao witches' broom disease, was assessed under field conditions of shaded cacao ( Theobroma cacao ) in south-eastern Bahia, Brazil. Biocontrol experiments were performed adjacent to an automated weather station, with sensors and Ts -treated brooms placed at different canopy heights. Sporulation occurred at the same dates for all Ts isolates, but in different quantities. Broom moisture >30%, air temperature of approximately 23 ± 3°C, relative humidity >90%, solar radiation intensities <0·12 KW m⁻² and wind speed near zero were the key environmental parameters that preceded Ts sporulation events. A multiple logistic regression indicated that these weather variables combined were capable of distinguishing sporulation from non-sporulation events, with a significant effect of wind speed. Analyses of environmental factors at ground level indicated similar pre-sporulation conditions, with a soil moisture content above a threshold of 0·34 m³ m⁻³ preceding all sporulation events. The sporulation of five selected Ts isolates was compared at four different canopy heights. Isolates responded differently to weather variation in terms of sporulation and antagonism to Mp at different canopy levels, indicating that different microclimates are established along the vertical profile of a shaded cacao plantation. The potential of these findings for development of predictive mathematical models and disease-management approaches is discussed.     

Encephalopathy caused by Talisia esculenta intoxication in pregnant ewes and their newborn lambs

An outbreak of acute encephalopathy occurred in pregnant ewes and their newborn lambs associated with consumption of Talisia esculenta fruits and bark. Clinical signs in 5 adult pregnant ewes included drooling, bloat, tachypnea, depression, ataxia, body shaking, difficulty in rising, and recumbency. Three neonatal lambs born to some of those ewes had similar clinical signs. No significant gross abnormalities were observed on autopsy. Histologically, neuronal necrosis, axonal and dendritic swelling, and loss of Purkinje neurons were observed in the cerebellum. The observation of similar neurologic clinical signs and lesions in pregnant ewes and their neonatal lambs suggests that the toxic principle of T. esculenta crosses the placenta and reaches the fetus.     

Glyphosate applied at low doses can stimulate plant growth

BACKGROUND: Glyphosate blocks the shikimic acid pathway, inhibiting the production of aromatic amino acids and several secondary compounds derived from these amino acids. Non-target plants can be exposed to low doses of glyphosate by herbicide drift of spray droplets and contact with treated weeds. Previous studies have reported that low doses of glyphosate stimulate growth, although these data are very limited. The objective of this study was to determine the effects of low glyphosate doses on growth of a range of plant species. RESULTS: Growth of maize, conventional soybean, Eucalyptus grandis Hill ex Maiden, Pinus caribea L. and Commelia benghalensis L. was enhanced by 1.8-36 g glyphosate ha(-1). Growth of glyphosate-resistant soybean was unaffected by any glyphosate dose from 1.8 to 720 g AE ha(-1). The optimum doses for growth stimulation were distinct for plant species and tissue evaluated. The greatest stimulation of growth was observed for C. benghalensis and P. caribea. Shikimic acid levels in tissues of glyphosate-treated soybean and maize were measured and found to be elevated at growth-stimulating doses. CONCLUSION: Subtoxic doses of glyphosate stimulate the growth of a range of plant species, as measured in several plant organs. This hormesis effect is likely to be related to the molecular target of glyphosate, since the effect was not seen in glyphosate-resistant plants, and shikimate levels were enhanced in plants with stimulated growth.     

Natural seed coats provide protection against penetration by Callosobruchus maculatus (Coleoptera: Bruchidae) larvae

The seed coat is the first host or non-host tissue contacted by bruchids, suggesting its participation in the evolutionary adaptation of bruchids to favor legume seeds. In the present work, we studied the influence of seed coat on the ability of Callosobruchus maculatus (Coleoptera: Bruchidae F.) larvae to penetrate, develop in and survive on seeds. Our results showed that the oviposition, larval eclosion and adult emergence of C. maculatus were drastically reduced in some seeds and that the time necessary for the surviving larvae to perforate the seed coat increased by up to 100% in these seeds. The surviving larvae that crossed the Phaseolus vulgaris (Leguminosae B.) seed coat reached only 55.6% of the mass of a normal larva. The seed coat of some seeds was very toxic to insect larval development. Despite individual variations, seed coats were generally highly restrictive to the development and survival of the bruchid. The study of the seed coat efficiency as a protection tissue against penetration of insects can provide an important tool for new strategies for crop protection. The strengthening of the seed coat defense mechanisms may represent an efficient strategy because the seed chemical defense barrier would be moved to the outer structures and damage to the embryo would be minimized or avoided.     

Alternative control of Chalara paradoxa,causal agent of black rot of pineapple by plant extract of Mormodica charantia

European Journal of Plant Pathology - Black rot of pineapple caused by the fungus Chalara paradoxa is considered an aggressive and difficult disease to control. The use of natural products has been...     

Microscopic analysis of calcium ionophore activated egress of Toxoplasma gondii from the host cell

Toxoplasma gondii invades and destroys nucleated cells of warm blooded hosts in a process which involves several steps: recognition, adhesion, penetration, multiplication inside a parasitophorous vacuole (PV) and egress. The last one is the least understood. Parasite egress from LLC-MK2 cells infected with the RH strain of T. gondii was artificially triggered with 4BrA23187 calcium ionophore. The combination of videomicroscopy, field emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM) showed that egress does not result from host cell rupture due to overloading with tachyzoites. Videomicroscopy showed that upon calcium ionophore administration parasite rosettes disassemble, the contour of the parasitophorous vacuole disappears and each tachyzoite takes a separate route to the extracellular medium. FESEM and TEM showed the fragmentation of the intravacuolar network, the fragmentation of parasitophorous vacuole membrane and individual tachyzoites with extruded conoids migrating through the cytosol, tightly surrounded by remnants of parasitophorous vacuole membrane or free in the cytosol. Both videomicroscopy and FESEM showed that a single parasite can cross the host cell membrane without disrupting it, while a large number of parasites, egressing simultaneously, rupture the membrane and the cell as a whole. These data suggest that invasion and egress share less similarities than previously believed.