Dynamic ventral disc contraction is necessary for Giardia attachment and host pathology.

Giardia lamblia is a common parasitic protist that infects the small intestine and causes giardiasis, resulting in diarrhea, vomiting, weight loss, and malabsorption. Giardiasis leads to cellular damage, including loss of microvilli, disruption of tight junctions, impaired barrier function, enzyme inhibition, malabsorption, and apoptosis. In the host, motile Giardia trophozoites attach to the duodenal microvilli using a unique microtubule organelle called the ventral disc. Despite early observations of disc-shaped depressions in microvilli after parasite detachment, little is known about disc-mediated attachment mechanisms and there little direct evidence showing that parasite attachment causes cellular damage. However, advancements in in vitro organoid models of infection and genetic tools have opened new possibilities for studying molecular mechanisms of attachment and the impact of attachment on the host. Through high-resolution live imaging and a novel disc mutant, we provide direct evidence for disc contraction during attachment, resolving the long-standing controversy of its existence. Specifically, we identify three types of disc movements that characterize contraction, which in combination result in a decrease in disc diameter and volume. Additionally, we investigate the consequences of attachment and disc contractility using an attachment mutant that has abnormal disc architecture. In a human organoid model, we demonstrate that this mutant has a limited ability to break down the epithelial barrier as compared to wild type. Based on this direct evidence, we propose a model of attachment that incorporates disc contraction to generates the forces required for the observed "grasping" of trophozoites on the host epithelium. Overall, this work highlights the importance of disc contractility in establishing and maintaining parasite attachment, leading to intestinal barrier breakdown.

Dry matter and calcium digestibility in captive veiled chameleons (Chamaeleo calyptratus).

Although metabolic bone disease (MBD) is a very common disease in reptiles kept as pets, empirical data on the calcium (Ca) metabolism of reptiles are still scarce. We used the opportunity of a large-scale experimental study on growth and clinical manifestations of MBD in captive veiled chameleons (Chamaeleo calyptratus) to measure the apparent dry matter (DM) and Ca digestibility in 19 animals (6-49 g), receiving locust nymphs (Locusta migratoria) of two size classes (0.05 and 0.5 g) with or without supplementation of Ca, vitamin A and cholecalciferol (Group A: Ca 0.04-0.09%DM; Group B: Ca 0.47-0.84%DM). Dry matter digestibility was significantly lower for animals receiving smaller-sized prey. A regression analysis of dietary Ca vs. digestible Ca content revealed a complete 'true' digestibility of Ca for the range of investigated diets, which might indicate that requirements for this mineral were not yet exceeded by the diets used (so that a reduction in Ca absorption would be induced). Options of higher dietary Ca provision, and reactions of chameleons to such diets, should be further investigated.

Comparative proteome analysis of Helicobacter pylori.

Helicobacter pylori, the causative agent of gastritis, ulcer and stomach carcinoma, infects approximately half of the worlds population. After sequencing the complete genome of two strains, 26695 and J99, we have approached the demanding task of investigating the functional part of the genetic information containing macromolecules, the proteome. The proteins of three strains of H. pylori, 26695 and J99, and a prominent strain used in animal models SS1, were separated by a high-resolution two-dimensional electrophoresis technique with a resolution power of 5000 protein spots. Up to 1800 protein species were separated from H. pylori which had been cultivated for 5 days on agar plates. Using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) peptide mass fingerprinting we have identified 152 proteins, including nine known virulence factors and 28 antigens. The three strains investigated had only a few protein spots in common. We observe that proteins with an amino acid exchange resulting in a net change of only one charge are shifted in the two-dimensional electrophoresis (2-DE) pattern. The expression of 27 predicted conserved hypothetical open reading frames (ORFs) and six unknown ORFs were confirmed. The growth conditions of the bacteria were shown to have an effect on the presence of certain proteins. A preliminary immunoblotting study using human sera revealed that this approach is ideal for identifying proteins of diagnostic or therapeutic value. H. pylori 2-DE patterns with their identified protein species were added to the dynamic 2D-PAGE database (http://www.mpiib-berlin.mpg.de/2D-PAGE/). This basic knowledge of the proteome in the public domain will be an effective instrument for the identification of new virulence or pathogenic factors, and antigens of potentially diagnostic or curative value against H. pylori.