The role of moral commitment within the Investment Model

The Investment Model (Rusbult, 1980) defines general commitment as a long-term orientation towards relationship maintenance and feelings of psychological attachment, influenced by satisfaction, quality of alternatives and intrinsic/extrinsic investments. We suggest the importance of additionally assessing moral commitment, defined by an intrapersonal predisposition to remain in the relationship (Johnson, 1991). We argue moral commitment's association to perceived intrinsic investments acting as internal barriers influencing general commitment and promoting relationship maintenance. A correlational study resorting to structural equation modelling showed that moral commitment predicted intrinsic investments, which in turn predicted general commitment (Model 1). No direct paths emerged from moral commitment to satisfaction or quality of alternatives (Model 2), nor it emerged as a fourth direct predictor of general commitment (Model 3). Results are discussed under relationships maintenance and dissolution frameworks.

Biochemical, stabilization and crystallization studies on a molecular chaperone (PaoD) involved in the maturation of molybdoenzymes

Molybdenum and tungsten enzymes require specific chaperones for folding and cofactor insertion. PaoD is the chaperone of the periplasmic aldehyde oxidoreductase PaoABC. It is the last gene in the paoABCD operon in Escherichia coli and its presence is crucial for obtaining mature enzyme. PaoD is an unstable, 35 kDa, protein. Our biochemical studies showed that it is a dimer in solution with a tendency to form large aggregates, especially after freezing/thawing cycles. In order to improve stability, PaoD was thawed in the presence of two ionic liquids [C4mim]Cl and [C2OHmim]PF6 and no protein precipitation was observed. This allowed protein concentration and crystallization using polyethylene glycol or ammonium sulfate as precipitating agents. Saturation transfer difference - nuclear magnetic resonance (STD-NMR) experiments have also been performed in order to investigate the effect of the ionic liquids in the stabilization process, showing a clear interaction between the acidic ring protons of the cation and, most likely, negatively charged residues at the protein surface. DLS assays also show a reduction of the overall size of the protein aggregates in presence of ionic liquids. Furthermore, cofactor binding studies on PaoD showed that the protein is able to discriminate between molybdenum and tungsten bound to the molybdenum cofactor, since only a Mo-MPT form of the cofactor remained bound to PaoD.

Effect of pressure on refolding of recombinant pentameric cholera toxin B

The production of recombinant proteins is an essential tool for the expansion of modern biological research and biotechnology. The expression of heterologous proteins in Escherichia coli often results in an incomplete folding process that leads to the accumulation of inclusion bodies (IB), aggregates that hold a certain degree of native-like secondary structure. High hydrostatic pressure (HHP) impairs intermolecular hydrophobic and electrostatic interactions, leading to dissociation of aggregates under non-denaturing conditions and is therefore a useful tool to solubilize proteins for posterior refolding. Cholera toxin (CT) is composed of a non-toxic pentamer of B subunits (CTB), a useful adjuvant in vaccines, and a toxic subunit A (CTA). We studied the process of refolding of CTB using HHP. HHP was shown to be effective for dissociation of CTB monomers from IB. Posterior incubation at atmospheric pressure of concentrated CTB (1mg/ml) is necessary for the association of the monomers. Pentameric CTB was obtained when suspensions of CTB IB were compressed at 2.4kbar for 16h in the presence of Tween 20 and incubated at 1bar for 120h. Soluble and biologically active pentameric CTB was obtained, with a yield of 213mg CTB/liter of culture. The experience gained in this study can be important to improve the refolding of proteins with quaternary structure.

Effect of magnetic hyperthermia on the structure of biofilm and cellular viability of a food spoilage bacterium

This work evaluated the effect of magnetic hyperthermia (MH) on planktonic cells and biofilms of a major food spoilage bacterium Pseudomonas fluorescens and its performance compared to a conventional direct heating (DH) technique. The results showed that MH had a greater and faster bactericidal effect, promoting a significant reduction in cell viability (≥3 Log CFU) in planktonic and biofilm cells, and leading to a complete eradication of planktonic cells at 55 °C (after only ~8 min). Accordingly, when comparing the same final temperatures, MH was more harmful to the integrity of cell membranes than DH, as observed in confocal laser scanning microscope images. Additionally, scanning electron microscope images revealed that exposure to MH had promoted modifications of the bacterial cell surface as well as of the structure of the biofilm. These results present the possibility of using MH out of the biomedical field as a potential disinfection method in food-related environments.

Toxicity of organic and inorganic nanoparticles to four species of white-rot fungi

The rapid development of nanoparticles (NP) for industrial applications and large-volume manufacturing, with its subsequent release into the environment, raised the need to understand and characterize the potential effects of NP to biota. Accordingly, this work aimed to assess sublethal effects of five NP to the white-rot fungi species Trametes versicolor, Lentinus sajor caju, Pleurotus ostreatus, and Phanerochaete chrysosporium. Each species was exposed to serial dilutions of the following NP: organic-vesicles of SDS/DDAB and of Mo/NaO; gold-NP, quantum dot CdSe/ZnS, and Fe/Co. Fungi growth rate was monitored every day, and at the end of assay the mycelium from each replicate was collected to evaluate possible changes in its chemical composition. For all NP-suspensions the following parameters were characterized: hydrodynamic diameter, surface charge, aggregation index, zeta potential, and conductivity. All tested NP tended to aggregate when suspended in aqueous media. The obtained results showed that gold-NP, CdSe/ZnS, Mo/NaO, and SDS/DDAB significantly inhibited the growth of fungi with effects on the mycelium chemical composition. Among the tested NP, gold-NP and CdSe/ZnS were the ones exerting a higher effect on the four fungi. Finally to our knowledge, this is the first study reporting that different types of NP induce changes in the chemical composition of fungi mycelium.

Meningococcal encephalitis associated with cerebellar tonsillar herniation and acute cervicomedullary injury

A 13-year-old girl presented with a progressive ascending paralysis, bulbar dysfunction and finally respiratory arrest. Magnetic resonance (MR) showed acute cervicomedullary injury and hindbrain herniation. An emergency foramen magnum decompression and external ventricular drainage insertion were performed, and meningococcal infection was diagnosed. The patient recovered completely. Meningococcal encephalitis may have an atypical presentation, and a surgery can optimise the outcome.

Does direct admission from an emergency department with on-site neurosurgical services facilitate time critical surgical intervention following a traumatic brain injury in children?

OBJECTIVES

To compare the proportion of trauma craniotomies performed within 4 hours of presentation to emergency departments (ED) with and without on-site neurosurgery.

DESIGN

A retrospective cohort analysis of data collected prospectively between January 2005 and April 2010 from patients with traumatic brain injury who were admitted to the paediatric intensive care unit (PICU) following traumatic brain injury.

METHODS

Times for admission to ED, PICU and theatre were obtained through analysis of prospectively collected data management systems. Emergency department admission to neurosurgical theatre lag time was calculated using Microsoft Excel. Statistical analysis was performed using R (version 2.11.0). Subjects. Fifty-seven cases were identified. Twenty patients were admitted directly from ED to an on-site neurosurgical unit. The remaining 37 were transferred from regional EDs.

RESULTS

Thirty-one craniotomies were performed. Thirteen in-patients admitted directly to hospital with neurosurgery on site. Eighteen in patients admitted at the local hospital and then transferred to the neurosurgical unit. Thirteen of Thirty-one (42%) craniotomies were performed within 4 hours. In the on-site group 10 of 13 (77%) craniotomies were performed within 4 hours compared to 3 of 18 (17%) in those transferred from regional ED (p = 0.001232) (Fisher exact test). Eleven patients were transferred directly from ED to neurosurgical theatre for emergency craniotomies. Within this subgroup, seven patients came from the cohort of admissions to a hospital with on-site neurosurgery. The remaining four patients were transferred from regional ED. There were eight extradural haematomas, one subdural haematoma and two intraparenchymal haemorrhages. The mean time from ED presentation to theatre was 1.68 hours and 5.46 hours for the on-site and regional transfer groups, respectively. There were no mortalities.

CONCLUSIONS

Forty-two per cent of trauma craniotomies are performed within 4 hours. However, presentation to an ED with on-site neurosurgical services significantly facilitates time critical surgery in children following a traumatic brain injury.

Probiotic yogurts manufactured with increased glucose oxidase levels: postacidification, proteolytic patterns, survival of probiotic microorganisms, production of organic acid and aroma compounds

We investigated the effect of increased glucose oxidase concentration as a technological option to decrease oxidative stress during the processing of probiotic yogurts. Probiotic yogurts were produced with increased concentrations of glucose oxidase (0, 250, 500, 750, or 1,000 mg/kg) and submitted to physicochemical and microbiological analysis at 1, 15, and 30 d of refrigerated storage. Higher concentrations of glucose oxidase (750 and 1,000 mg/kg) and a longer storage time were found to have an influence on the characteristics of the probiotic yogurt, contributing to more extensive postacidification, an increase in the dissolved oxygen level, and higher proteolysis. In addition, increased production of aroma compounds (diacetyl and acetaldehyde) and organic acids (mainly lactic acid) and a decrease in the probiotic bacteria count were reported. The use of glucose oxidase was a feasible option to minimize oxidative stress in probiotic yogurts. However, supplementation with excessive amounts of the enzyme may be ineffective, because insufficient substrate (glucose) is present for its action. Consumer tests should be performed to evaluate changes in the sensory attributes of the probiotic yogurts with increased supplementation of glucose oxidase. In addition, packaging systems with different permeability to oxygen should be evaluated.

Characterization and crystallization of mouse aldehyde oxidase 3: from mouse liver to Escherichia coli heterologous protein expression

Aldehyde oxidase (AOX) is characterized by a broad substrate specificity, oxidizing aromatic azaheterocycles, such as N¹-methylnicotinamide and N-methylphthalazinium, or aldehydes, such as benzaldehyde, retinal, and vanillin. In the past decade, AOX has been recognized increasingly to play an important role in the metabolism of drugs through its complex cofactor content, tissue distribution, and substrate recognition. In humans, only one AOX gene (AOX1) is present, but in mouse and other mammals different AOX homologs were identified. The multiple AOX isoforms are expressed tissue-specifically in different organisms, and it is believed that they recognize distinct substrates and carry out different physiological tasks. AOX is a dimer with a molecular mass of approximately 300 kDa, and each subunit of the homodimeric enzyme contains four different cofactors: the molybdenum cofactor, two distinct [2Fe-2S] clusters, and one FAD. We purified the AOX homolog from mouse liver (mAOX3) and established a system for the heterologous expression of mAOX3 in Escherichia coli. The purified enzymes were compared. Both proteins show the same characteristics and catalytic properties, with the difference that the recombinant protein was expressed and purified in a 30% active form, whereas the native protein is 100% active. Spectroscopic characterization showed that FeSII is not assembled completely in mAOX3. In addition, both proteins were crystallized. The best crystals were from native mAOX3 and diffracted beyond 2.9 Å. The crystals belong to space group P1, and two dimers are present in the unit cell.