Teetering on the Rim: Global Restructuring, Daily Life, and the Armed Retreat of the Bolivian State.

Teetering on the Rim: Global Restructuring, Daily Life, and the Armed Retreat of the Bolivian State. Lesley Gill. New York: Columbia University Press, 2000. 222 pp.     

Titanium Implant Impairment and Surrounding Muscle Cell Death Following High-Salt Diet: An In Vivo Study

Aim of the study

High-salt consumption has been widely described as a risk factor for cardiovascular, renal and bone functions. In the present study, the extent to which high-salt diet could influence Ti6Al4V implant surface characteristic, its adhesion to rat tibial crest, and could modify muscle cell viability of two surrounding muscles, was investigated in vivo. These parameters have also been assessed following a NMES (neuro-myoelectrostimulation) program similar to that currently used in human care following arthroplasty.

Results

After a three-week diet, a harmful effect on titanium implant surface and muscle cell viability was noted. This is probably due to salt corrosive effect on metal and then release of toxic substance around biologic tissue. Moreover, if the use of NMES with high-salt diet induced muscles damages, the latter were higher when implant was added. Unexpectedly, higher implant-to-bone adhesion was found for implanted animals receiving salt supplementation.

Conclusion

Our in vivo study highlights the potential dangerous effect of high-salt diet in arthroplasty based on titanium prosthesis. This effect appears to be more important when high-salt diet is combined with NMES.     

Role of Δ1-Pyrroline-5-Carboxylate Dehydrogenase Supports Mitochondrial Metabolism and Host-Cell Invasion of Trypanosoma cruzi

Proline is crucial for energizing critical events throughout the life cycle of Trypanosoma cruzi, the etiological agent of Chagas disease. The proline breakdown pathway consists of two oxidation steps, both of which produce reducing equivalents as follows: the conversion of proline to Δ¹-pyrroline-5-carboxylate (P5C), and the subsequent conversion of P5C to glutamate. We have identified and characterized the Δ¹-pyrroline-5-carboxylate dehydrogenase from T. cruzi (TcP5CDH) and report here on how this enzyme contributes to a central metabolic pathway in this parasite. Size-exclusion chromatography, two-dimensional gel electrophoresis, and small angle x-ray scattering analysis of TcP5CDH revealed an oligomeric state composed of two subunits of six protomers. TcP5CDH was found to complement a yeast strain deficient in PUT2 activity, confirming the enzyme''s functional role; and the biochemical parameters (K_m, k_cat, and k_cat/K_m) of the recombinant TcP5CDH were determined, exhibiting values comparable with those from T. cruzi lysates. In addition, TcP5CDH exhibited mitochondrial staining during the main stages of the T. cruzi life cycle. mRNA and enzymatic activity levels indicated the up-regulation (6-fold change) of TcP5CDH during the infective stages of the parasite. The participation of P5C as an energy source was also demonstrated. Overall, we propose that this enzymatic step is crucial for the viability of both replicative and infective forms of T. cruzi.     

Secondary phytohaemagglutinin (PHA) swelling response is a good indicator of T‐cell‐mediated immunity in free‐living birds

The validity of using the phytohaemagglutinin (PHA) test to measure acquired immunity, one of the most widely used methods, is currently being debated due to new knowledge on the complex physiology of the process. As a greater secondary response to repeated challenges linked to increases of circulating lymphocyte levels would be indicative of a T‐cell‐mediated immune response, we performed for the first time an experiment under natural conditions with repeated PHA challenges in free‐living adult birds and chicks to shed light on this topic. We found significantly stronger secondary response to PHA injection independent of sex or age, while controlling for body condition, the second response being on average 90% larger than the first. Likewise, lymphocyte counts were significantly higher in the second PHA challenge, whereas no significant differences were found among untreated birds. Significant positive correlations between the PHA response and both lymphocyte counts and plasma protein levels (mainly albumin, globulin precursor) were recovered, whereas no significant differences were recovered in plasma protein levels between challenges. Our results are consistent with those from captive birds, supporting the validity of the PHA skin‐swelling test as an accurate gauge of acquired T‐cell‐mediated immunity in birds.     

Dimerization of Neu/Erb2 transmembrane domain is controlled by membrane curvature

Secondary structures of the proto-oncogenic Neu/ErbB2 transmembrane segment and its mutant analogue have been determined in phospholipids. It is found that the mutated peptide possesses less helical character possibly due to the valine/glutamic acid point mutation. Embedding peptides in lipid systems whose topology can change from small (100-200 A) tumbling objects to bilayer discs of 450 A diameter leads to the finding that coiled-coil interactions are only observed in the presence of a bilayer membrane of low curvature, independent of mutation. This strongly suggests that any event that may change membrane topology can therefore perturb the dimerization/ologomerization and subsequent phosphorylation cascade leading to cell growth or cancer processes.