Trypanosoma cruzi: cloning and expression of an antigen recognized by acute and chronic human chagasic sera.

Here we describe the characterization of a Trypanosoma cruzi DNA sequence (clone A13) that codes for a polypeptide recognized by IgM and IgG antibodies from sera of acute and congenital chagasic patients. Antibodies to A13 antigen are also detected in the sera of chronic patients with different clinical forms of Chagas' disease, but not in sera of patients with leishmaniasis or other parasitic diseases. The antigenic determinants encoded by clone A13 are found in amastigotes and trypomastigotes of several T. cruzi strains, but not in the noninfective epimastigotes. The DNA sequence of the recombinant clone reveals one open reading frame encoding 251 amino acids without tandemly repeated sequences. Our data suggest that the A13 antigen may be useful for the development of serodiagnostic procedures.     

Studies on the yield and gel strength of agar from Gracilaria domingensis Sonder ex Kuetzing (Gracilariales,Rhodophyta) following the addition of calcium

Studies were carried out on the seasonal variation in yield and gel strength of agar from Gacilaria domingensis with and without the addition of calcium chloride. Extraction was done with and without treatment with 1% hydrochloric acid. The results showed an increase in yield and gel strength when an alkaline solution of calcium was used, but the gel strength was low. For commercial use, Gracilaria domingensis should be mixed with better quality Gracilaria species because of its low gel strength.     

REPRODUCTIVE BIOLOGY OF A TROPICAL PALM SWAMP COMMUNITY IN THE VENEZUELAN LLANOS

The reproductive biology of a tropical palm swamp community, called morichal in the Venezuelan Central Llanos, was studied. Of the 128 woody and herbaceous species of plants recorded, 99 (77.34%) were hermaphrodites, 25 (19.53%) were monoecious, and four (3.13%) were dioecious. The morichal is characterized by a low number of species with obligate cross-fertilization. The frequencies of species with different breeding systems in a subsample of 26 species showed that eight (30.77%) were self-incompatible, 14 (53.85%) were self-compatible, and four (15.38%) were agamospermous. Ten of 14 self-compatible species were autogamous. Regardless of the self-incompatibility level estimated, seed and fruit set were greater in self-fertilized flowers than in hand-pollinated flowers in three of the nine self-incompatible species. These results are related to the facts that: 1) the relative isolation of the plant population limits the gene flow among similar communities and enforces the intrapopulation pollen flow; 2) the overlapping flowering patterns and infrequent and unspecialized pollinators may be enforcing self-compatibility and agamospermy; 3) self-compatibility is the rule among short-lived species in the morichal; and 4) three out of four agamospermous species are of the Melastomataceae family.     

Arabitol accumulation in Geotrichum candidum

Culture conditions which lead to the intracellular accumulation of arabitol and mannitol in Geotrichum candidum were investigated. The accumulation of arabitol was dependent on the concentrations of metabolizable hexoses, the non-metabolizable disaccharide sucrose, NaCl and KCl in the growth medium. In media containing 2% (w/v) glucose, fructose or l-sorbose cultures contained only mannitol after 48 h or 72 h growth. In media containing 10% (w/v) to 30% (w/v) glucose, or 25% (w/v) fructose or l-sorbose there was an increase in the total concentration of intracellular polyol due to the accumulation of arabitol. This pentitol was also found to accumulate intracellularly when the organism was grown in medium containing 34% (w/v) sucrose, 0.7 M NaCl or 0.7 M KCl in addition to 2% (w/v) glucose. Under the conditions tested no change in the accumulation of mannitol or ethanol-soluble carbohydrate, believed to be primarily composed of trehalose, was evident.Intracellular polyol was released during incubation of arthrospores obtained from media containing 25% or 10% glucose, in distilled water at 25° C, but no polyol was released under these conditions from arthrospores obtained from growth in 2% glucose medium.     

The Roberts syndrome

Summary Four siblings with the autosomal recessive Roberts syndrome are reported, and we discuss the phenotypic overlap of this syndrome with other similar radial, aplasia syndromes.     

Lysine-ketoglutarate reductase activity in developing maize endosperm

Lysine-ketoglutarate reductase activity was detected and characterized in the developing endosperm of maize (Zea mays L.). The enzyme showed specificity for its substrates: lysine, α-ketoglutarate, and NADPH. Formation of the reaction product saccharopine was demonstrated. The pH optimum of the enzyme was close to 7, and the K_m for lysine and α-ketoglutarate were 5.2 and 1.8 millimolar, respectively.     

Feeding and trapping fish withPiper auritum

The “natives” at Rio Indio, on the central Caribbean slope of Panama, trap the river fishBrycon chagrensis using leaves ofPiper auritum as bait in feeders. The people use this technique because the fish tastes like the leaf after it has fed regularly on the leaf. This technique has potential use in aquaculture. The plant could also be cultivated for marketing as a food-flavoring condiment and fish food.