Structure and properties of agar from two unexploited agarophytes from Venezuela

The red seaweeds Gelidiella acerosa and Gracilaria mammillaris growing along the coast of Venezuela were investigated as potential economic sources of agar. Agar extracted from Gracilaria mammillaris accounted for 27% of the algal dry weight but had quite a poor gelling ability because of the presence of alkali-stable sulphate groups on the D-galactose residue. However, the gel strength of its aqueous solutions was considerably enhanced by the addition of potassium, sodium and calcium ions (up to 1N). On the contrary, the galactan from Gelidiella acerosa (yield of about 20% w/w) exhibited quite good properties. In particular, the gel strength was comparable to that of commercial agaroses. Sulphate esters were not detectable by chemical methods and NMR spectroscopy revealed an agarose backbone with a high degree of methylation on both D and L-galactose residues.     

Microbial complexes from apogeotropic roots and from rhizosphere of cycad plants

The microbial complexes of soil, the rhizosphere, and the rhizoplane of the apogeotropic (coralloid) roots of cycad plants were comparatively studied. The aseptically prepared homogenates of the surface-sterilized coralloid roots did not contain bacterial microsymbiont, indicating that it was absent in the root tissues. At the same time, associated bacteria belonging to different taxonomic groups were detected in increasing amounts in the cycad rhizoplane, rhizosphere, and the surrounding soil. The bacterial communities found in the cycad rhizoplane and the surrounding soil were dominated by bacteria from the genus Bacillus. The saprotrophic bacteria and fungi colonizing the cycad rhizosphere and rhizoplane were dominated by microorganisms capable of degrading the plant cell walls. The local degradation of the cell wall was actually observed on the micrographs of the thin sections of cycad roots in the form of channels, through which symbiotic cyanobacterial filaments can penetrate into the cortical parenchyma.     

Isolation and genotyping of Toxoplasma gondii from free-ranging chickens from Mexico

The prevalence of Toxoplasma gondii in free-ranging chickens is a good indicator of the presence of T. gondii oocysts in the environment because chickens feed from the soil. In the present study, prevalence of T. gondii in 208 free-range chickens (Gallus domesticus) from Mexico was investigated. Blood, heart, and brain from each animal were obtained to test for T. gondii infection. Antibodies to T. gondii, assayed with the modified agglutination test (1:10 or higher), were found in 13 (6.2%) chickens. Hearts and brains of 13 seropositive chickens were bioassayed in mice, and T. gondii was isolated from 6 chickens. All 6 isolates were avirulent for mice. Genotyping of chicken isolates of T. gondii using the SAG2 locus indicated that 5 were type III and 1 was type I. This is the first report of isolation of T. gondii from chickens from Mexico.     

Isolation of Surface Immunoglobulin from Lymphocytes from Human and Murine Thymus

CELLS capable of binding radioiodinated antigen occur in lymphocyte populations obtained from foetal and neonatal human thymus¹. In accordance with Ehrlich's hypothesis of 1900 (ref. 2), the receptors for antigen on the surface of these cells probably consist of immunoglobulin. A first step in the attainment of chemical proof of the nature of this receptor is the identification of immunoglobulin on the thymus cells. We now report the isolation of immunoglobulin from the surfaces of lymphocytes obtained from murine and neonatal human thymuses. This isolation and identification was made possible by application of a modification³ of the enzymatic iodination procedure of Marchalonis⁴ which catalysed the iodination of proteins present on the surfaces of living lymphocytes.     

Isolation and genotyping of Toxoplasma gondii from free-ranging chickens from Argentina

The prevalence of Toxoplasma gondii in free-ranging chickens can be considered a good indicator of the prevalence of T. gondii oocysts in the environment because chickens feed from the ground. In the present study, prevalence of T. gondii in 29 free-range chickens (Gallus domesticus) from Argentina was investigated. Blood, heart, and brain from each chicken were examined for T. gondii infection. Antibodies to T. gondii, assayed with the modified agglutination test (MAT), were found in 19 of 29 (65.5%) chickens. Hearts and brains of seropositive (MAT > or = 1:5) chickens were bioassayed in mice. Toxoplasma gondii was isolated from 9 of 19 seropositive chickens. Genotyping of chicken isolates of T. gondii using the SAG2 locus indicated that 1 was type I, 1 was type II, and 7 were type III. This is the first report of isolation of T. gondii from chickens from Argentina.     

Extraction and purification of pectins from Alcohol Insoluble Solids from ripe and unripe apples

Pectins are extracted from Alcohol Insoluble Solids of ripe and unripe apples and fractionated by ion exchange chromatography and gelfiltration. In the extracts mainly pectins with neutral sugar contents of 0·15, 0·24 and 0·53 mol neutral sugar residues/mole galacturonate residues are present. The pectin molecules contain rhamnose, arabinose, xylose, galactose, glucose and galacturonic acid residues. No mannose could be detected. The neutral sugar composition of the glycans bound to the galacturonan was found to be constant, except for the relative amount of galactose. During ripening the neutral sugar composition of the extractable pectin does not change.     

Characterization of amylolytic and pullulytic enzymes from thermophilic archaea and from a newFervidobacterium species

Nine extremely thermophilic archaea and one novel thermophilic bacterium were screened for their ability to produce amylolytic and pullulytic enzymes. Cultivation of these micro-organisms was performed in the absence of elemental sulphur with starch as the major carbon source. Enzymatic activity was mainly detected in two archaea belonging to the order Thermoproteales,Desulfurococcus mucosus andStaphylothermus marinus, in two archaea belonging to the order Thermococcales,Thermococcus celer andT. litoralis and in two novel archaeal strains, TYS and TY previously isolated from the Guaymas Basin in the Gulf of California. Both amylolytic and pullulytic activities were also detected in a newly isolated thermophilic bacterium belonging to the order Thermotogales and previously described asFervidobacterium pennavorans. Best yields for enzyme production were obtained in 1–1 batch cultures with the strains TYS (13 units U/1 of amylase, 6 U/1 of pullulanase),F. pennavorans (2.5 U/l of amylase, 4.5 U/l of pullulanase) andT. litoralis (3.0 U/l of amylase). Enzymes were in general characterized by temperature optima around 90–100°C, pH optima around 5.5–6.5 and a high degree of thermostability. Due to the remarkable properties of these enzymes, they are of interest for biotechnological applications.     

Direct methylation from mouse plasma and from liver and brain homogenates

The analysis of fatty acid composition of plasma and tissue is important as a method for studying lipid nutrition. We investigated the possibility of direct methylation of fatty acids by BF(3)-methanol from plasma and from liver and brain homogenates without lipid extraction. There were no ghost peaks in the chromatogram produced by the direct methylation method. The 18:0 percentages were significantly higher in the direct methylation method than in the lipid extraction method. There were not remarkable differences in fatty acid composition in the direct methylation and methylation after lyophilization methods. Furthermore, the recovery ratio of the internal standard in the direct methylation method was higher than that in the lipid extraction method. The difference of fatty acid composition with lipid extraction may be caused by the change of lipid class extraction. Therefore, the direct methylation method without lipid extraction is the most suitable for determining fatty acid composition in plasma and tissue.     

Virulence of Yersinia pseudotuberculosis isolated from pork and from the throats of swine

Yersinia pseudotuberculosis was isolated from retail pork and from healthy swine throats. These wild-type strains and their representative cured isogenic strains were tested for the presence of plasmids and several virulence factors, and these characteristics were compared with those of virulent strains from humans. Two pork isolates (serotype IVB) and four swine isolates (serotypes IIB, IIC, III, and IVB) harbored a 42- to 48-megadalton plasmid which had similar fragmentation patterns resulting from digestion with restriction endonuclease. These six strains were lethal for mice via oral challenge and were positive in autoagglutination and calcium dependency tests. They also invaded HeLa cells and induced cytotoxicity. Histopathological examination and indirect fluorescent-antibody staining provided definite evidence of the pathogenicity of these strains when tissue sections from orally infected mice were used. The virulence factors of wild-type pork and swine isolates with the 42- to 48-megadalton plasmid were identical to those of two human isolates (serotypes IVB and VB). Hence, these pork and swine isolates should be considered potentially pathogenic for humans. The finding suggests that retail pork and swine may play an important role in the epidemiology of human infections caused by Y. pseudotuberculosis.     

Isolation of the C-fragment and C''-fragment of lipotropin from pig pituitary and C-fragment from brain.

Three novel peptides derived from lipotropin, the C-Fragment (residues 61-91), C'-Fragment (61-87) and N-Fragment (1-38), were isolated from pig pituitary, and the C-Fragment was shown to be present in brain. The experimental procedures developed for their isolation are described. The formation of each of the fragments involves enzymic cleavage of lipotropin at consecutive basic residues, with specificity identical with that involved in the activation of known prohormones. In brain assays C-Fragment exhibits a range of biological activities related to its ability to act as an inhibitory neurotransmitter.     

Comparison of ethylenediaminetetraacetate-enhanced exudation from detached and translocation from attached bean leaves

A technique for collection of phloem exudate from detached leaves using 20 millimolar EDTA (pH 7.0) has previously been developed (King, Zeevaart 1974 Plant Physiol 53: 96-103). It was the aim of the present study to determine the efficiency of this technique in relation to undisturbed export from attached leaves. Paired primary leaves of bean seedlings (Phaseolus vulgaris L. cv Montcalm) were used to minimize variations in plant material. Attached leaves, exposed to ¹⁴CO₂ for 10 minutes with subsequent excision of one of the leaves and collection of the exudate over a 12-hour period, showed a 25% export of total assimilated ¹⁴C from the attached versus 15% of total assimilated ¹⁴C in the form of exudation from the detached ones. Leaf excision changed the labeling pattern within the leaf, increasing% total leaf ¹⁴C-activity in the ethanolic fraction, while decreasing activity in the starch fraction, as compared to attached leaves. This was presumably caused by a lack of translocation from the detached leaves. Excision did not affect dark respiration. However, measurements of total nonstructural carbohydrates in leaf starch and neutral fractions indicated no significant differences between attached and leaves detached in EDTA. Thus, in terms of actual carbon export, and accompanying distribution of nonexported carbohydrate within the leaf, EDTA-enhanced exudation compares favorably with translocation from attached leaves.