Development of a new quantitative gas permeability method for dental implant-abutment connection tightness assessment

Background  

Most dental implant systems are presently made of two pieces: the implant itself and the abutment. The connection tightness between those two pieces is a key point to prevent bacterial proliferation, tissue inflammation and bone loss. The leak has been previously estimated by microbial, color tracer and endotoxin percolation.     

Design and baseline characteristics of the ParkFit study,a randomized controlled trial evaluating the effectiveness of a multifaceted behavioral program to increase physical activity in Parkinson patients

Background  

Many patients with Parkinson's disease (PD) lead a sedentary lifestyle. Promotion of physical activities may beneficially affect the clinical presentation of PD, and perhaps even modify the course of PD. However, because of physical and cognitive impairments, patients with PD require specific support to increase their level of physical activity.     

Fairy, tadpole, and clam shrimps (Branchiopoda) in seasonally inundated clay pans in the western Mojave Desert and effect on primary producers

Background

Fairy shrimps (Anostraca), tadpole shrimps (Notostraca), clam shrimps (Spinicaudata), algae (primarily filamentous blue-green algae [cyanobacteria]), and suspended organic particulates are dominant food web components of the seasonally inundated pans and playas of the western Mojave Desert in California. We examined the extent to which these branchiopods controlled algal abundance and species composition in clay pans between Rosamond and Rogers Dry Lakes. We surveyed branchiopods during the wet season to estimate abundances and then conducted a laboratory microcosm experiment, in which dried sediment containing cysts and the overlying algal crust were inundated and cultured. Microcosm trials were run with and without shrimps; each type of trial was run for two lengths of time: 30 and 60 days. We estimated the effect of shrimps on algae by measuring chlorophyll content and the relative abundance of algal species.

Results

We found two species of fairy shrimps (Branchinecta mackini and B. gigas), one tadpole shrimp (Lepidurus lemmoni), and a clam shrimp (Cyzicus setosa) in our wet-season field survey. We collected Branchinecta lindahli in a pilot study, but not subsequently. The dominant taxa were C. setosa and B. mackini, but abundances and species composition varied greatly among playas. The same species found in field surveys also occurred in the microcosm experiment. There were no significant differences as a function of experimental treatments for either chlorophyll content or algal species composition (Microcoleus vaginatus dominated all treatments).

Conclusions

The results suggest that there was no direct effect of shrimps on algae. Although the pans harbored an apparently high abundance of branchiopods, these animals had little role in regulating primary producers in this environment.     

Phylogenetic analysis using insertion sequence fingerprinting in Escherichia coli

Chromosomal DNA from 23 closely related, pathogenic strains of Escherichia coli was digested and probed for the insertion sequences IS1, IS2, IS4, IS5, and IS30. Under the assumption that elements residing in DNA restriction fragments of the same apparent length are identical by descent, parsimony analysis of these characters yielded a unique phylogenetic tree. This analysis not only distinguished among bacterial strains that were otherwise identical in their biochemical characteristics and enzyme electrophoretic mobilities, but certain aspects of the topology of the tree were consistent across several unrelated insertion elements. The distribution of IS elements was then reexamined in light of the inferred phylogenetic relationships to investigate the biological properties of the elements, such as rates of insertion and deletion, and to discover apparent recombinational events. The analysis shows that the pattern of distribution of insertion elements in the bacterial genome is sufficiently stable for epidemiological studies. Although the rate of recombination by conjugation has been postulated to be low, at least two such events appear to have taken place.      

The adaptation of enzymes to temperature: catalytic characterization of glucosephosphate isomerase homologues isolated from Mytilus edulis and Isognomon alatus, bivalve molluscs inhabiting different thermal environments

Homologues of glucosephosphate isomerase (GPI, EC 5.3.1.9) were purified to homogeneity and kinetically characterized from Mytilus edulis and Isognomon alatus, two bivalve molluscs experiencing contrasting thermal environments. The enzyme isolated from I. alatus functions at warmer temperatures (25-35 C) than GPI from M. edulis, a species that inhabits colder marine littoral habitats (5-20 C). The former exhibits apparent first-order (with respect to substrate) catalytic rate constants (Vmax/KM) in vitro that become progressively greater than the mussel enzyme as the assay temperature is raised. Apparent zero-order catalytic rate constants (Vmax) are relatively less differentiated. Catalytic efficiency, defined as the rate at which a catalytic event occurs in either reaction direction for reference standard states (substrate concentrations), is greater for the enzyme from the tropical species (I. alatus) at all realistic combinations of temperature and substrate concentration except for the lowest temperatures and highest substrate concentrations, where the GPI from the boreal/temperate M. edulis is more efficient. This pattern of catalytic divergence appears to be due primarily to differentiation in Vmax/KM. These results and other published data are reviewed and shown to be inconsistent with claims that adaptation of enzymes to higher cell temperatures requires a loss in catalytic efficiency.