Trypanosoma gambiense: Blocking ability of parasite and macrophage homogenates on attachment during phagocytosis

This study deals with the ability of the parasite and macrophage homogenates, each fractionated into soluble and insoluble parts, to block the attachment of Trypanosoma gambiense on the macrophage in the process of phagocytosis. The soluble parasite fraction and the insoluble macrophage fraction both showed a high blocking ability. However, the ability of the parasite fraction was completely lost on trypsin digestion, while that of the macrophage was not changed at all. In addition, sonication of the macrophage did not change its blocking ability.     

Tracking soluble and nanoparticulated titanium released in vivo from metal dental implant debris using (single-particle)-ICP-MS

BackgroundThis work studies the presence of the Ti, Al and V metal ions and Ti nanoparticles released from the debris produced by the implantoplasty, a surgical procedure used in the clinic, in rat organs.MethodsThe sample preparation for total Ti determination was carefully optimized using microsampling inserts to minimize the dilution during the acid attack of the lyophilized tissues by a microwave-assisted acid digestion method. An enzymatic digestion method was optimized and applied to the different tissue samples in order to extract the titanium nanoparticles for the single-particle ICP-MS analysis.ResultsA statistically significant increase was found for Ti concentrations from control to experimental groups for several of the studied tissues, being and particularly significant in the case of brain and spleen. Al and V concentrations were detected in all tissues but they were not different when comparing control and experimental animals, except for V in brain. The possible presence of Ti-containing nanoparticles mobilized from the implantoplasty debris was tested using enzymatic digestions and SP-ICP-MS. The presence of Ti-containing nanoparticles was observed in all the analyzed tissues, however, differences on the Ti mass per particle were found between the blanks and the digested tissue and between control and experimental animals in some organs.ConclusionThe developed methodologies, both for ionic and nanoparticulated metal contents in rat organs, have shown the possible increase in the levels of Ti both as ions and nanoparticles in rats subjected to implantoplasty.     

Endogenous cellulase enzymes in the stick insect (Phasmatodea) gut

High cellulase (endo-beta-1,4-glucanase) activity was detected in the anterior midgut of the walking stick (Phasmatodea) Eurycantha calcarata. The enzyme was isolated and analyzed via mass spectrometry. RT-PCR revealed two endoglucanase genes, EcEG1 and EcEG2. Mascot analysis of the purified enzyme confirms it to be the product of gene EcEG1. Homologous cDNAs were also isolated from a distantly related species, Entoria okinawaensis, suggesting a general distribution of cellulase genes in phasmids. Phasmid cellulases showed high homology to endogenously-produced glycoside hydrolase family 9 (GH9) endoglucanases from insects, especially to those of termites, cockroaches, and crickets. The purified E. calcarata enzyme showed clear antigency against an anti-serum for termite GH9 cellulase, which, together with the sequence homology, further suggests an endogenous origin of the enzyme. This discovery suggests a possible nutritive value for cellulose in the leaf-feeding phasmids, unlike in herbivorous Lepidoptera.     

Trade-off between digestion and respiration in two airbreathing callichthyid catfishes Holposternum littorale (Hancock) and Corydoras aeneus (Gill)

In callichthyid catfishes, the posterior intestine is modified to function as an air breathing organ by being air-filled, thin-walled and highly vascularized. These modifications make it unsuitable for digestive functions and digesta has to be transported quickly through this region to minimize disruption of vital respiratory functions. However, the weak muscles of the wall of the respiratory intestine make this problematic. It is hypothesized that the unidirectional ventilatory air current within the respiratory intestine is responsible for the quick transport of digesta through the respiratory intestine. To verify this, movement of digesta through the alimentary tract was examined in Hoplosternum littorale and Corydoras aeneus that were either allowed to breathe air or prevented from air breathing. When air breathing was prevented, digesta was not transported to the rectum in H. littorale and there was a 94% reduction in the amount of digesta in the rectum of C. aeneus. This study suggests that the anterior digestive intestine facilitates the passage of air although it is filled with digesta. The anterior digestive intestine packages digesta into a string of slightly compressed boluses, creating an air channel in the digestive intestine thus allowing air to pass unimpeded.     

Stomach stones in king penguin chicks

Many animals that possess a gizzard swallow stones or sandy grit, supposedly to aid in the mechanical breakdown of food. While this has been well documented in the literature, our study is the first to report the presence of stones in the gizzard of king penguin chicks. We found stones, so called ‘gastroliths’, in the pyloric region of the gizzard, the part of the digestive tract that is specialised for the mechanical breakdown of food. Stones were already present in the gizzard of chicks and, hence, during the first year of the life of king penguins, which is spent on land. Some chicks were found to have more than 130 stones (0.5–22 mm in size) in their gizzard. The gastroliths we found in king penguins are of the same geological origin as rocks present at the colony, which suggests that birds swallowed them there. The functional role of gastroliths in penguin chicks and adults is still unknown. We discuss the potential roles that these gastroliths might play in king penguins (i.e. aid in digestion, buoyancy control during foraging at sea, adaptation to fasting).     

Lysozymes in insects: what role do they play in nitrogen metabolism?

Abstract. Lysozymes are widely distributed in many organisms as one of the components of defence mechanisms. In herbivores, when nitrogen is not contained in sufficient amounts in the diet, bacteria lysed by stomach lysozymes are used as sources of nitrogen. In ruminants, lysozymes function as digestive enzymes in the true stomach. A convergence of amino acid sequence has been shown between the stomach lysozymes of different ruminants, and similar lysozymes have recently been reported in the gut or salivary gland of insects. In this mini review, the enzymatic and ecological functions of lysozymes in insects, particularly in termites, are introduced, together with future studies that are needed in this field.     

Flexibility of digestive responses in two generalist herbivores,the tortoises Geochelone carbonaria and Geochelone denticulata

Summary To test the prediction that digestive responses digestibility, intake and passage time-of generalist herbivores vary with different diets, feeding trials were conducted in Venezuela with two sympatric tortoise species, Geochelone carbonaria and G. denticulata. Three single-species diets (two fruit, one foliage) were fed to both species. For a given diet, digestibility, mass-specific intake and passage time did not differ between the two tortoise species, nor did they vary by sex or body mass within each species. However, the digestive parameters varied for tortoises feeding on the different diets. The responses ranged from nearly abandoning cell wall fermentation and depending entirely on extraction of cell contents to relying heavily on cell wall fermentation. Therefore, these generalist herbivores have flexible digestive responses that are influenced by diet, not fixed digestive responses that limit the diet, as previously observed in other generalist herbivores. A three-part classification of herbivores (specialist, specialized mixed feeder and opportunistic mixed feeder) is suggested as an approach to understanding flexible and inflexible digestive strategies in herbivores.     

Protease inhibitors in the alimentary tract of the medicinal leech Hirudo medicinalis: In vivo and in vitro studies

Summary In individual leeches the flux of labeled serum through the digestive tract was monitored to measure the rate of digestion. A mean value of 10 mg of the original serum (or 2–3 mg of the contents of the foregut) per individual per day was found, which was constant during 10 weeks. On average the serum remained in the intestinum for 20 days. Occurrence and concentrations of eglin and bdellin, specific proteinase inhibitors of Hirudo, were analyzed after various periods following the ingestion of a meal. In the foregut they were present immediately after feeding. Their quantities increased several-fold within a few weeks. In the intestinum the tests for these inhibitors were always negative. The inhibition of the proteolytic activity of intestinum preparations by eglin, bdellin, and foregut extract was tested in vitro. Using azo-albumin as (an unspecific) substrate, inhibition by eglin was maximally 25% and by bdellin 60%. When the quantitative relations presumably representing in vivo conditions were applied, only a slight inhibition of proteolysis occurred. A hypothetical role of the inhibitors in the preservation of the blood stored in the foregut is discussed.Abbreviations BIGGANA N-benzoyl-isoleucyl-glutaryl-glycyl-arginyl-4-nitroanilide - SAPPNA N-succinyl-alanyl-alanyl-prolyl-phenylalanyl-4-nitroanilide - TPCK tosyl-phenylalanyl-chloromethyl-detone - TRIS tris-(hydroxymethyl)aminomethane     

Analysis of starch amylolysis using plots for first-order kinetics

Investigators often study product release from starches during prolonged incubations with α-amylase in vitro. The reaction time courses usually fit to a linear form of a first order rate equation, i.e., ln[(C_∞ − C_t)/C_∞] = −kt. This equation calls for an accurate estimate of C_∞, i.e., the concentration of product at the end of the reaction. Estimates of C_∞ from digestibility curves can be unreliable. The Guggenheim method does not require prior knowledge of C_∞ but seems not to have been applied to starch hydrolysis data. An alternative method is also available in which the logarithm of the slope (LOS) of a digestibility curve at various time points is plotted against time. This allows estimations of both k and C_∞ and can also reveal whether changes occur in digestion rate from rapid to slow as digestion proceeds. We describe the Guggenheim and LOS methods and provide examples of their application to starch digestibility data.