Comparison of frugivory by howling monkeys (Alouatta palliata) and bats (Artibeus jamaicensis) in the tropical rain forest of Los Tuxtlas,Mexico

Information on the fruit diets of howling monkeys and fruit-eating bats in the tropical rain forest of Los Tuxtlas, Mexico was collected for a year to compare the plant species used. Howling monkeys used 19 plant species whereas bats used 32 plant species as fruit sources. Eleven species were common in the diet of both mammals. A rank analysis at the plant species level showed that the fruit diets of Alouatta and Artibeus were very different. In contrast to bats, howling monkeys displayed a seasonal pattern in fruit consumption. Diet overlap between the two mammals was highest during the monkeys' fruit-eating season. Measures of fruit production in eight trees (four species) indicated marked variations in fruit biomass produced and in length of fruiting from tree to tree and species to species. Peaks in fruit production were typical both at the species and the individual tree levels, demonstrating the very patchy nature of the fruit available to the monkeys and the bats.     

Construction of a model of the human proximal colon

The objective of the present study was to construct a system that re-creates the conditions of fermentation and absorption of the human proximal colon. The model was constructed using a glass tube with an internal dialysis membrane tube. The food substrate was fed into the dialysis membrane three times a day simulating a typical human feeding. The substrate contained 58% carbohydrates, 35% proteins, 3% fiber, 3% starch, and 1% lipids on dry weight base, with 90% moisture. The inoculum was a fecal culture propagated in TSB. The intestinal absorption was simulated using a polyethylene glycol (PEG) solution running continuously outside the dialysis membrane. All microorganisms increased their counts after inoculation, and reached higher counts generally after substrate feed. The most important short chain fatty acids (SCFA: acetic, propionic and butyric acids) were analyzed, and their concentrations inside and outside the membrane were significantly different due to the extraction efficiency of the PEG solution. The greatest production occurred at 48 h. SCFA ratios showed that at the beginning, acetate was the predominant compound, but after 12 h the proportion of butyrate increased and the acetate was decreased. This SCFA production pattern is similar to that reported for the proximal colon in live systems. Continuous operation of the colon model for 48 h was enough to reveal the development of microorganisms and SCFA production. This model reproduced the conditions of the human proximal colon adequately and can be used to study the development of colonic microbiota.     

Structure of the oligosaccharide portion of human hepatitis B surface antigen

The hepatitis B surface antigen, which constitutes the currently available vaccine, is the empty envelope of the hepatitis B virus. We investigated the carbohydrate structures of the envelope glycoproteins. The intact oligosaccharides were enzymatically released from the coat glycoproteins using peptide-N4-(N-acetyl-beta-glucosaminyl) asparagine amidase F and isolated by gel permeation chromatography. Cesium ion liquid secondary ion mass spectra of the intact, underivatized oligosaccharides showed molecular weights of 1932, 2078, and 2223. The mixture included partially and totally sialylated structures, a fraction (approximately 8%) of which were substituted with a single terminal fucose residue; no desialylated oligosaccharides were detected. The reducing termini of the oligomers were derivatized by reduction of the Schiff base formed using p-aminobenzoic acid ethyl ester, and fragmentation patterns identical to those produced from standard biantennary complex oligosaccharides were obtained. Methylation linkage analysis of the oligosaccharides showed that the carbohydrate composition and the mannose branching patterns also resembled those of a biantennary oligosaccharide. The results of this study indicate that glycosylation of the hepatitis B surface antigen, which takes place in the liver, is typical of other serum glycoproteins made in the liver; and this analytical strategy, including cesium ion liquid secondary ion mass spectrometry, is an effective approach for the structural analysis of complex carbohydrates available in only the 1-10 micrograms sample size range.