Starch consolidation of calcium carbonate as a tool to develop lightweight fillers for LDPE-based plastics

Calcium carbonate (CaCO3) is used as a filler to improve the stiffness and processability of plastics at low cost. However, its high density limits the quantity to be used. In this work, the feasibility of using starch consolidation of eggshells-derived CaCO3 (ES) to develop lightweight fillers for low density polyethylene (LDPE)-based materials was studied. Starch, recovered from potato by-products, was combined with ES, gelatinized, dried, and milled as a fine powder. The obtained ES/starch-based particles were then compounded with LDPE and their influence on chromatic, mechanical, morphological, and density properties of mold injected LDPE-based materials was studied. Commercially available CaCO3 (COM) was used as control. ES/starch particles were 18 times less dense than the commercially available CaCO3 (2.62 g cm-3). When incorporated into LDPE-based formulations, ES/starch originated brownish materials with lower density (1.18 g cm-3) and higher stiffness (542 MPa of Young's modulus) than those produced with the COM sample (1.33 g cm-3 of density; 221 MPa of Young's modulus). Therefore, starch consolidation of ES revealed to be a promising approach to develop lightweight fillers able to provide stiffness and color to LDPE-based plastics, while valorizing biomolecules-rich by-products.

Evaluation of physical fitness in police dogs using an incremental exercise test

The aim of this study was to evaluate the feasibility of using blood lactate (BL), heart rate (HR) and rectal temperature (RT) to evaluate the physical fitness of police dogs using a treadmill incremental exercise test. The animals (n=20) were exercised using a protocol that consisted of five stages of six minutes each at increasing speeds of 9.66, 11.27, 12.87, 14.48 and 16.09 km/h with a slope adjusted to 10%. The test ended when the animal completed the five steps or when exhaustion was reached, either during or between steps. BL from the marginal ear vein, HR and RT were measured on the police dogs at rest (T0), after each step (T1 to T5) and after a recovery period of 20 minutes (T6). The mean duration of exercise was 19 min 17 s (standard deviation ± 5 min 30 s), with only one animal completing all five stages. In the case of BL, no differences were found when comparing consecutive stages, but when compared to the values at rest (T0), a significant increase was found in T2 (P<0.05), T3, T4 and T6 (P<0.001). When the RT was considered, an increase was found between T0 and T3 (P<0.05). HR was the parameter in which the largest variations were observed, between T1 and T2 (P<0.05), and T1, T4 and T6 when compared to the stage immediately before (P<0.01). When compared to T0, all stages showed differences (P<0.001). However, no correlation was found between the parameters evaluated in this test. This study showed the feasibility of evaluating the physical fitness of police dogs using a blood sample from the marginal ear vein and a lactate portable measuring device. It was also found that the values recorded in animals previously familiarised with the treadmill were similar to those that were not. This work provides data that can be used in training and testing of dogs that perform this kind of work, and can be the basis for further studies.

Rhizomelic chondrodysplasia punctata is a peroxisomal protein targeting disease caused by a non-functional PTS2 receptor

Rhizomelic chondrodysplasia punctata (RCDP) is an autosomal recessive disease characterized clinically by a disproportionately short stature primarily affecting the proximal parts of the extremities, typical dysmorphic facial appearance, congenital contractures and severe growth and mental retardation. Although some patients have single enzyme deficiencies, the majority of RCDP patients (86%) belong to a single complementation group (CG11, also known as complementation group I, Amsterdam nomenclature). Cells from CG11 show a tetrad of biochemical abnormalities: a deficiency of i) dihydroxyacetonephosphate acyltransferase, ii) alkyldihydroxyacetonephosphate synthase, iii) phytanic acid alpha-oxidation and iv) inability to import peroxisomal thiolase. These deficiencies indicate involvement of a component required for correct targeting of these peroxisomal proteins. Deficiencies in peroxisomal targeting are also found in Saccharomyces cerevisiae pex5 and pex7 mutants, which show differential protein import deficiencies corresponding to two peroxisomal targeting sequences (PTS1 and PTS2). These mutants lack their PTS1 and PTS2 receptors, respectively. Like S. cerevisiae pex cells, RCDP cells from CG11 cannot import a PTS2 reporter protein. Here we report the cloning of PEX7 encoding the human PTS2 receptor, based on its similarity to two yeast orthologues. All RCDP patients from CG11 with detectable PEX7 mRNA were found to contain mutations in PEX7. A mutation resulting in C-terminal truncation of PEX7 cosegregates with the disease and expression of PEX7 in RCDP fibroblasts from CG11 rescues the PTS2 protein import deficiency. These findings prove that mutations in PEX7 cause RCDP, CG11.