The lateral diffusion of lipid probes in the surface membrane of Schistosoma mansoni.

The technique of fluorescence recovery after photobleaching was used to measure the lateral diffusion of fluorescent lipid analogues in the surface membrane of Schistosoma mansoni. Our data reveal that although some lipids could diffuse freely others exhibited restricted lateral diffusion. Quenching of lipid fluorescence by a non-permeant quencher, trypan blue, showed that there was an asymmetric distribution of lipids across the double bilayer of mature parasites. Those lipids that diffused freely were found to reside mainly in the external monolayer of the outer membrane whereas lipids with restricted lateral diffusion were located mainly in one or more of the monolayers beneath the external monolayer. Formation of surface membrane blebs allowed us to measure the lateral diffusion of lipids in the membrane without the influence of underlying cytoskeletal structures. The restricted diffusion found on the normal surface membrane of mature parasites was found to be released in membrane blebs. Quenching of fluorescent lipids on blebs indicated that all probes were present almost entirely in the external monolayer. Juvenile worms exhibited lower lateral diffusion coefficients than mature parasites: in addition, the lipids partitioned into the external monolayer. The results are discussed in terms of membrane organization, cytoskeletal contacts, and biological significance.

Soil quality and financial performance of biodynamic and conventional farms in new zealand.

Biodynamic farming practices and systems show promise in mitigating some of the detrimental effects of chemical-dependent, conventional agriculture on the environment. The physical, biological, and chemical soil properties and economic profitability of adjacent, commercial biodynamic and conventional farms (16 total) in New Zealand were compared. The biodynamic farms in the study had better soil quality than the neighboring conventional farms and were just as financially viable on a per hectare basis.

Isolation and characterisation of a surface membrane glycoprotein from adult Schistosoma mansoni.

A peanut agglutinin-binding glycoprotein in adult Schistosoma mansoni was shown to be absent from pre-liver worms, but could be detected on the worm surface in large amounts at four weeks post-infection. Four-week parasites incubated with fluorescein isothiocyanate-peanut agglutinin showed a general surface fluorescence. The molecule did not incorporate methionine or palmitate. ELISA using the isolated glycoprotein showed the presence of antibodies to it in serum from infected mice and from humans infected with S. mansoni and Schistosoma haematobium. The implications of these results for surface membrane development are discussed.

N-acetylation of serotonin, octopamine and dopamine by adult Brugia pahangi.

The metabolism of biogenic amines by the filarial worm, Brugia pahangi, was investigated by incubating cut worms with radio-labelled amine substrates. Two-dimensional thin-layer chromatography and analysis on two high-performance liquid chromatography systems showed that [14C]5-hydroxytryptamine was metabolised to a less polar compound that was identified as N-acetyl 5-hydroxytryptamine. N-Acetyloctopamine and N-acetyldopamine were also formed when cut B. pahangi were incubated with [14C]octopamine and [3H]dopamine, respectively. N-Acetyltransferase activity towards 5-hydroxytryptamine was readily detected in nematode homogenates. This enzyme was localised in a 50,000 x g supernatant and required the addition of the co-substrate, acetyl CoA, for activity. No evidence was obtained for the involvement of monoamine oxidases in the metabolism of 5-HT in these filarial worms.

Lectin binding to glycoproteins in the surface membrane of Schistosoma mansoni.

A number of lectins were assessed for their ability to bind to glycoproteins in the surface membrane of Schistosoma mansoni. The membrane polypeptides were separated by SDS-PAGE and the glycoproteins visualised by incubating the gel with radio-iodinated lectin followed by autoradiography. Most of the individual lectins bound to a variety of glycoproteins but peanut agglutinin and Dolichos biflorus agglutinin bound preferentially to a single glycoprotein of apparent molecular weight 170 000. This glycoprotein was subsequently shown to be exposed at the surface of the parasite and localised at the tubercles.

Tegument surface membranes of adult Schistosoma mansoni: development of a method for their isolation.

Several approaches to surface membrane stripping have been applied to the adult schistosome. Membrane removal was evaluated by the use of different extrinsic and intrinsic markers of which alkaline phosphatase proved to be the most reliable. After initial studies employing incubation of worms in buffer alone, Triton X-100 or freeze/thaw, the last method was chosen for development. The final method applies a single freeze/thaw step to adult worms in balanced salt solution followed by short bursts of agitation on a vortex mixer to release the tegument. Differential and density gradient steps subsequently yield a final membrane pellet enriched over 130 times in surface alkaline phosphatase. The method has been characterized during its development using electron microscopy and enzyme markers for contaminant worm fractions.

Immunocytochemistry of cytoskeletal proteins in adult Schistosoma mansoni.

Antisera to vertebrate actin and actin-binding proteins were used to characterize the cytoskeleton of adult Schistosoma mansoni. Actin, alpha-actinin and tropomyosin immunoreactivities were detected in the cytoplasm of the apical tegument. Antiserum to alpha-actinin bound to the tegumental spines and this protein may be involved in cross-linking of spine actin filaments. Actin, alpha-actinin and tropomyosin antisera bound to the musculature. Strongest immunoreactivity was seen in the parenchyma. Antisera to actin, alpha-actinin, tropomyosin and spectrin bound to parenchyma cells including those of the tubercles, suggesting that these proteins are located in muscle cell bodies. The distribution of cytoskeletal proteins is discussed in relation to tegumental repair processes.

Formation of tumor-like structures on legume roots by Rhizobium.

Tumor-like structures appeared on the roots of Medicago sativa, Alysicarpus vaginalis, and Trifolium pratense inoculated with a non-nodulating strain of Rhizobium trifolii or with irradiated cultures of either of two nodulating Rhizobium strains. The structures were composed of disorganized plant tissues which, on the basis of microscopic examination, were devoid of bacterial cells. Rhizobia which could nodulate legumes of one cross-inoculation group and which were able to induce formation of such tumor-like structures on plants of a second cross-inoculation group were isolated from extracts of these root growths. The apparent tumorogenic activity of some of the rhizobia, but not their nodulating capacity, was lost when the bacteria were transferred in laboratory media.

Isolation and characterisation of discoid granules from the tegument of adult Schistosoma mansoni.

Discoid granules were isolated from the tegument of adult Schistosoma mansoni by differential centrifugation of freeze-thaw extracts. Comparison of proteins and glycoproteins from discoid granules, surface membranes and the soluble fraction implied that discoid granules and the surface membrane were functionally linked. The results are discussed in terms of discoid granule function and surface membrane organisation.