Bending continuous structures with SMAs: a novel robotic fish design

In this paper, we describe our research on bio-inspired locomotion systems using deformable structures and smart materials, concretely shape memory alloys (SMAs). These types of materials allow us to explore the possibility of building motor-less and gear-less robots. A swimming underwater fish-like robot has been developed whose movements are generated using SMAs. These actuators are suitable for bending the continuous backbone of the fish, which in turn causes a change in the curvature of the body. This type of structural arrangement is inspired by fish red muscles, which are mainly recruited during steady swimming for the bending of a flexible but nearly incompressible structure such as the fishbone. This paper reviews the design process of these bio-inspired structures, from the motivations and physiological inspiration to the mechatronics design, control and simulations, leading to actual experimental trials and results. The focus of this work is to present the mechanisms by which standard swimming patterns can be reproduced with the proposed design. Moreover, the performance of the SMA-based actuators' control in terms of actuation speed and position accuracy is also addressed.     

Palmitoylation of inducible nitric-oxide synthase at Cys-3 is required for proper intracellular traffic and nitric oxide synthesis

A number of cell types express inducible nitric-oxide synthase (NOS2) in response to exogenous insults such as bacterial lipopolysaccharide or proinflammatory cytokines. Although it has been known for some time that the N-terminal end of NOS2 suffers a post-translational modification, its exact identification has remained elusive. Using radioactive fatty acids, we show herein that NOS2 becomes thioacylated at Cys-3 with palmitic acid. Site-directed mutagenesis of this single residue results in the absence of the radiolabel incorporation. Acylation of NOS2 is completely indispensable for intracellular sorting and .NO synthesis. In fact, a C3S mutant of NOS2 is completely inactive and accumulates to intracellular membranes that almost totally co-localize with the Golgi marker beta-cop. Likewise, low concentrations of the palmitoylation blocking agents 2-Br-palmitate or 8-Br-palmitate severely affected the .NO synthesis of both NOS2 induced in muscular myotubes and transfected NOS2. However, unlike endothelial NOS, palmitoylation of inducible NOS is not involved in its targeting to caveolae. We have created 16 NOS2-GFP chimeras to inspect the effect of the neighboring residues of Cys-3 on the degree of palmitoylation. In this regard, the hydrophobic residue Pro-4 and the basic residue Lys-6 seem to be indispensable for palmitoylation. In addition, agents that block the endoplasmic reticulum to Golgi transit such as brefeldin A and monensin drastically reduced NOS2 activity leading to its accumulation in perinuclear areas. In summary, palmitoylation of NOS2 at Cys-3 is required for both its activity and proper intracellular localization.     

Age, Growth Rates, Sex Change and Feeding Habits of Notothenioid Fish Eleginops Maclovinus from the Central-southern Chilean Coast

The róbalo, Eleginops maclovinus, a protandrous hermaphrodite species, is an important component of the ichthyofauna in the coastal areas and estuaries of southern Chile. However, there are many aspects about its life history that are unknown. Three hundred and eighty-three specimens of E. maclovinus (19–79 cm total length, TL) were collected between November 2002 and December 2003 from central-southern Chile. Marginal increment analysis from sagittal otoliths showed a single annual minimum in March, demonstrating that a single growth ring is formed each year. The growth of E. maclovinus was described by the von Bertalanffy growth model by following parameters: L _∞ = 105.4 cm TL, K = 0.08 per year, and t ₀ = −1.03 years. E. maclovinus can live for 10 years. The length and age at which the 50% of the males in the population transformed into females was estimated at ~36 cm TL and ~5-years old. A total of 27 prey items were identified. The most important prey items were the crustaceans Hemigrapsus crenulatus and Emerita analoga associated with estuarial and marine habitats respectively. Ontogenetic changes in the diet were related to the spatial distributional pattern of males (1–4 years old, in the estuary) and females (5–8 years old, in the sea). Also, diet changes are associated with the type of available prey in each habitat occupied, indicating a generalized opportunist strategy.     

Cytochrome oxidase in health and disease

Yeast and bovine cytochrome c oxidases (COX) are composed of 12 and 13 different polypeptides, respectively. In both cases, the three subunits constituting the catalytic core are encoded by mitochondrial DNA. The other subunits are all products of nuclear genes that are translated on cytoplasmic ribosomes and imported through different transport routes into mitochondria. Biogenesis of the functional complex depends on the expression of all the structural and more than two dozen COX-specific genes. The latter impinge on all aspects of the biogenesis process. Here we review the current state of information about the functions of the COX-specific gene products and of their relationship to human COX deficiencies.     

Gene dose influences cellular and calcium channel dysregulation in heterozygous and homozygous T4826I-RYR1 malignant hyperthermia-susceptible muscle

Malignant hyperthermia susceptibility (MHS) is primarily conferred by mutations within ryanodine receptor type 1 (RYR1). Here we address how the MHS mutation T4826I within the S4-S5 linker influences excitation-contraction coupling and resting myoplasmic Ca²⁺ concentration ([Ca²⁺]_rest) in flexor digitorum brevis (FDB) and vastus lateralis prepared from heterozygous (Het) and homozygous (Hom) T4826I-RYR1 knock-in mice (Yuen, B. T., Boncompagni, S., Feng, W., Yang, T., Lopez, J. R., Matthaei, K. I., Goth, S. R., Protasi, F., Franzini-Armstrong, C., Allen, P. D., and Pessah, I. N. (2011) FASEB J. doi:22131268). FDB responses to electrical stimuli and acute halothane (0.1%, v/v) exposure showed a rank order of Hom ≫ Het ≫ WT. Release of Ca²⁺ from the sarcoplasmic reticulum and Ca²⁺ entry contributed to halothane-triggered increases in [Ca²⁺]_rest in Hom FDBs and elicited pronounced Ca²⁺ oscillations in ∼30% of FDBs tested. Genotype contributed significantly elevated [Ca²⁺]_rest (Hom > Het > WT) measured in vivo using ion-selective microelectrodes. Het and Hom oxygen consumption rates measured in intact myotubes using the Seahorse Bioscience (Billerica, MA) flux analyzer and mitochondrial content measured with MitoTracker were lower than WT, whereas total cellular calpain activity was higher than WT. Muscle membranes did not differ in RYR1 expression nor in Ser²⁸⁴⁴ phosphorylation among the genotypes. Single channel analysis showed highly divergent gating behavior with Hom and WT favoring open and closed states, respectively, whereas Het exhibited heterogeneous gating behaviors. [³H]Ryanodine binding analysis revealed a gene dose influence on binding density and regulation by Ca²⁺, Mg²⁺, and temperature. Pronounced abnormalities inherent in T4826I-RYR1 channels confer MHS and promote basal disturbances of excitation-contraction coupling, [Ca²⁺]_rest, and oxygen consumption rates. Considering that both Het and Hom T4826I-RYR1 mice are viable, the remarkable isolated single channel dysfunction mediated through this mutation in S4-S5 cytoplasmic linker must be highly regulated in vivo.     

Administration of triclabendazole is safe and effective in controlling fascioliasis in an endemic community of the bolivian altiplano

Background

The Bolivian northern Altiplano is characterized by a high prevalence of Fasciola hepatica infection. In order to assess the feasibility, safety and efficacy of large-scale administration of triclabendazole as an appropriate public health measure to control morbidity associated with fascioliasis, a pilot intervention was implemented in 2008.

Materials and Methods

Schoolchildren from an endemic community were screened for fascioliasis and treated with a single administration of triclabendazole (10 mg/kg). Interviews to assess the occurrence of adverse events were conducted on treatment day, one week later, and one month after treatment. Further parasitological screenings were performed three months after treatment and again two months later (following a further treatment) in order to evaluate the efficacy of the intervention.

Results

Ninety infected children were administered triclabendazole. Adverse events were infrequent and mild. No serious adverse events were reported. Observed cure rates were 77.8% after one treatment and 97.8% after two treatments, while egg reduction rates ranged between 74% and 90.3% after one treatment, and between 84.2% and 99.9% after two treatments. The proportion of high-intensity infections (≥400 epg) decreased from 7.8% to 1.1% after one treatment and to 0% after two treatments.

Conclusion

Administration of triclabendazole is a feasible, safe and efficacious public health intervention in an endemic community in the Bolivian Altiplano, suggesting that preventive chemotherapy can be applied to control of fascioliasis. Further investigations are needed to define the most appropriate frequency of treatment.     

Mitochondrial respiratory thresholds regulate yeast chronological life span and its extension by caloric restriction

We have explored the role of mitochondrial function in aging by genetically and pharmacologically modifying yeast cellular respiration production during the exponential and/or stationary growth phases and determining how this affects chronological life span (CLS). Our results demonstrate that respiration is essential during both growth phases for standard CLS, but that yeast have a large respiratory capacity, and only deficiencies below a threshold (~40% of wild-type) significantly curtail CLS. Extension of CLS by caloric restriction also required respiration above a similar threshold during exponential growth and completely alleviated the need for respiration in the stationary phase. Finally, we show that supplementation of media with 1% trehalose, a storage carbohydrate, restores wild-type CLS to respiratory-null cells. We conclude that mitochondrial respiratory thresholds regulate yeast CLS and its extension by caloric restriction by increasing stress resistance, an important component of which is the optimal accumulation and mobilization of nutrient stores.