Differential diffusivity of Nodal and Lefty underlies a reaction-diffusion patterning system

Biological systems involving short-range activators and long-range inhibitors can generate complex patterns. Reaction-diffusion models postulate that differences in signaling range are caused by differential diffusivity of inhibitor and activator. Other models suggest that differential clearance underlies different signaling ranges. To test these models, we measured the biophysical properties of the Nodal/Lefty activator/inhibitor system during zebrafish embryogenesis. Analysis of Nodal and Lefty gradients revealed that Nodals have a shorter range than Lefty proteins. Pulse-labeling analysis indicated that Nodals and Leftys have similar clearance kinetics, whereas fluorescence recovery assays revealed that Leftys have a higher effective diffusion coefficient than Nodals. These results indicate that differential diffusivity is the major determinant of the differences in Nodal/Lefty range and provide biophysical support for reaction-diffusion models of activator/inhibitor-mediated patterning.     

青海互助土族民间利用野生植物调查

采用民族植物学和人类学的研究方法,对青海互助土族民间利用野生植物进行了调查.结果表明,与当地土族直接相关的野生植物包括32种,经常食用的有12种.     

Field observations of fish species susceptible to epizootic ulcerative syndrome in the Zambezi River basin in Sesheke District of Zambia

A field investigation was conducted in the Sesheke District of Zambia along the Zambezi River to determine the fish species susceptible to epizootic ulcerative syndrome (EUS), a newly confirmed disease in Southern Africa. A total of 2,132 fishes were inspected for gross EUS-like lesions, of which 188 (8.82%; 95% CI = 7.67–10.1%) were found with typical characteristic lesions of EUS. Of these 188 samples, 156 were found to have mycotic granulomas on histopathological analysis, representing 83.0% (95% CI = 76.7–87.9%) of the initially identified in the laboratory through gross examination. The following 16 species of fish were examined and found with EUS lesions; Clarias ngamensis, Clarias gariepinus, Barbus poechii, Tilapia sparrmanii, Serranochromis angusticeps, Brycinus lateralis, Micralestes acutidens, Sargochromis carlottae, Hydrocynus vittatus, Phryngochromis acuticeps, Schilbe intermedius, Hepsetus odoe, Labeo lunatus, Oreochromis andersonii, Barbus unitaeniatus, and Barbus paludinosus. T. sparrmanii did not show any lesions, while the Clarias species were found to be the most afflicted with EUS. These results could be useful to fish farmers and organizations interested in improving aquaculture in the area.     

Demonstration of neuraminidase activity in Mycoplasma neurolyticum and of neuraminidase proteins in three canine Mycoplasma species

Neuraminidases are virulence factors in many pathogenic microorganisms. They are present also in some Mycoplasma species that cause disease in birds, dogs and alligators. Thirty-seven Mycoplasma species have been examined previously for neuraminidase (sialidase) activity, whereas many of the species causing disease in man, ruminants, pigs, rodents and other animals have not. In this study neuraminidase enzymatic activity (NEAC) was examined in 45 previously untested Mycoplasma species, including those causing diseases in man, farm animals and laboratory animals. The only species in which NEAC was found was Mycoplasma neurolyticum, specifically, its type strain (Type A(T)) which is capable of inducing neurologic signs in inoculated young mice and rats. The NEAC of washed cells was relatively weak, but it differed even more than 10-fold among cells of cultures derived from individual colonies of M. neurolyticum. A weak NEAC was also detected in the supernatant of the M. neurolyticum broth culture. Canine Mycoplasma spp. with high sialidase activity reported previously, Mycoplasma canis, Mycoplasma cynos and Mycoplasma molare had 100-fold more NEAC than M. neurolyticum, but apparent differences in NEAC levels existed among strains of M. canis and of M. cynos. Zymograms using neuraminidase-specific chromogenic substrate were used to show proteins having NEAC. In M. canis (a field isolate Larissa and the type strain PG14(T)), M. cynos (isolate 896) and M. molare (type strain H542(T)) proteins with NEAC had molecular masses of ～130kDa, 105kDa and 110kDa, respectively. Identification of these neuraminidases could provide the basis for their molecular characterization.     

Characterization of the antigenic and functional domains of a Mycoplasma synoviae variant vlhA gene

The Mycoplasma synoviae haemagglutinin gene, vlhA, encodes two major immunodominant and surface-exposed membrane proteins, MSPB and MSPA. Both products are antigenically variable but only MSPA mediates binding to erythrocytes. Previously we have shown that M. synoviae type strain WVU 1853 could express a variant vlhA gene, referred to as MS2/28.1, with a considerably shorter and divergent MSPA region. A finding that prompted detailed characterization of its antigenic and functional properties. Here we mutagenized each of the six opal codons of the variant MS2/28.1 vlhA member into tryptophan, thus allowing its expression in Escherichia coli as well as its cleavage products, MSPB and MSPA. In addition, we expressed 5 contiguous regions of MS2/28.1 extending from the last part of MSPB to the C-terminus of MSPA. Colony immunostaining with region-specific antisera mapped antigenic variation to the N-terminal half of MS2/28.1 MSPA. No haemagglutinating activity was observed for MSPB, but consistent haemadsorption inhibition was mapped to the region extending from amino acid 325 to 344. Inhibition of both haemagglutination and haemadsorption activities were obtained with sera directed against the C-terminal region of MSPA, with the highest titers (1/320 and 1/160, respectively) being recorded for its last 60 residues. Importantly, antibodies to this region also yielded the highest metabolic inhibition titer of 1/1280. Overall, aside from mapping the functional domains of a M. synoviae highly divergent haemagglutinin gene, this study shows that the C-terminal half of its MSPA region induced the highest titers of antibodies inhibiting haemagglutination, haemadsorption, and metabolism.     

Oxidative damage in bone and erythrocytes of suckling rats exposed to 2,4-dichlorophenoxyacetic acid

Nowadays, people’s exposure to pesticides such as 2,4-dichlorophenoxyacetic acid (2,4-D) is increasing continuously. This compound is suspected to produce in excess free radicals which have adverse effects on human health causing several cell alterations in the organism. The present study investigated oxidative stress in the bone and erythrocytes of suckling rats whose mothers were treated with 2,4-D. Experiments were carried out on adult Wistar rats given 600 mg/L of 2,4-D in their drinking water from the 14th day of pregnancy until day 14 after delivery. Exposing dams to 2,4-D caused disorders in the bone of their progeny. Indeed, it induced changes in bone mineralization, especially calcium and phosphorus levels. Moreover, total tartrate-resistant acid phosphatase, which reflected bone resorption, was enhanced while total alkaline phosphatase, which reflected bone formation, was reduced suggesting that this herbicide accelerated bone resorption. The impairment of bone function corresponded histologically.Rats exposed to 2,4-D showed in both bone and erythrocytes an increase in malondialdehyde, advanced oxidation protein products and protein carbonyl levels and a decrease in non-enzymatic (glutathione, non-protein thiol, and vitamin C) and enzymatic (superoxide dismutase, catalase, and glutathione peroxidase) antioxidant system.     

Resistance to <Emphasis Type="Italic">Bemisia tabaci</Emphasis> in tomato wild relatives

Bemisia tabaci is one of the most threatening pests in agriculture, particularly in Solanaceous crops such as tomato and pepper that are cultivated in the open field. Pesticide application is often not effective and hazardous to humans and environment. The exploitation of plant natural defenses that are present in wild relatives of tomato, may offer a solution. To evaluate resistance parameters and to identify plant material with high levels of resistance, we screened a number of accessions of tomato wild relatives using three methods; a free-choice test in a screenhouse in Indonesia, a no-choice test with clip-on cages in a greenhouse and a leaf disc test in a climate-room in the Netherlands. Antibiosis resulting in low adult survival was the major component for resistance in tomato. However, other resistance component(s) may play a role as well. In some accessions there was a change in the resistance level over time. Several resistance parameters used in the different tests were well correlated. The best resistance source was an accession of Solanum galapagense, which had not been identified as being resistant in the past. This is of particular interest as this species is closely related to the cultivated tomato, which may facilitate introgression of the resistance component(s). Whitefly non-preference and resistance were associated with the presence of type IV trichomes. Other mechanisms might be involved since some accessions without type IV trichomes showed low nymphal density. The leaf disc test is a good in vitro alternative for the clip-on cage whitefly resistance screening, as shown by the high correlation between the results obtained with this test and the clip-on cage test. This offers breeders the possibility to carry out tests more efficiently.     

Radio-telemetry as a tool to define protected areas for seabirds in the marine environment

Although most Manx shearwaters (Puffinus puffinus) in the UK are protected within Special Protection Areas (SPAs) at their breeding colonies, such site-based protection does not currently extend into the marine environment. Manx shearwaters form rafts (dense flocks of birds) on the sea adjacent to their breeding colony from late afternoon onwards, before coming ashore after nightfall. The ecological and protection requirements of Manx shearwaters in the UK would be more completely addressed if existing SPA boundaries were extended into adjacent marine areas to include those used for rafting behaviour. However the spatial extent of rafts has never been assessed accurately. Because rafting behaviour continues after nightfall, radio-telemetry was used to investigate rafting distributions of Manx shearwaters around the three largest UK colonies: Skomer (south-west Wales), Bardsey (north-west Wales) and Rum (north-west Scotland). Totals of 30, 28 and 30 birds were radio-tagged, with 174, 264 and 385 rafting locations estimated for Skomer, Rum and Bardsey, respectively. Kernel contour analysis was used to describe the ‘rafting range’ around each colony. The maximum extent of the 95% kernel contours was used to determine the area which would encompass most rafting birds. The maximum extents of rafting ranges were 4, 6 and 9 km, respectively for Skomer, Rum and Bardsey. We believe this is the first successful illustration of how radio-telemetry data can potentially be used to define protected areas for birds in the marine environment.     

A school salad bar increases frequency of fruit and vegetable consumption among children living in low-income households

OBJECTIVE: To measure change in fruit and vegetable (F&V) consumption among elementary-school children after the introduction of a salad bar programme as a lunch menu option in the US Department of Agriculture's (USDA) reimbursable lunch programme in Los Angeles Unified School District (LAUSD). DESIGN: A cross-sectional sample of children was interviewed before and after a salad bar intervention (1998 and 2000, respectively) utilising a 24-hour food recall questionnaire. Frequencies of F&V consumption were calculated. SETTING: The evaluation took place in three LAUSD elementary schools participating in the salad bar programme and the USDA reimbursable lunch programme. SUBJECTS: Three hundred and thirty-seven children in 2nd-5th grade (7-11 years old). RESULTS: After the salad bar was introduced, there was a significant increase in frequency (2.97 to 4.09, P < 0.001) of F&V consumed among the children studied. The increase in frequency of F&V consumed was almost all due to an increase during lunch (84%). Mean energy, cholesterol, saturated fat and total fat intakes were significantly lower in the children after the salad bar was introduced in the schools compared with the intakes in the children before the salad bar was introduced.Conclusion: A salad bar as a lunch menu option in the USDA reimbursable lunch programme can significantly increase the frequency of F&V consumption by elementary-school children living in low-income households.     

Comment on "Preindustrial to modern interdecadal variability in coral reef pH"

Based on the boron isotopic composition of coral from the southwestern Pacific, Pelejero et al. (Reports, 30 September 2005, p. 2204) suggested that natural variations in pH can modulate the impact of ocean acidification on coral reef ecosystems. We show that this claim cannot be reconciled with other marine carbon chemistry constraints and highlight problems with the authors' interpretation of the paleontologic data.