Platelets release novel thiol isomerase enzymes which are recruited to the cell surface following activation

The thiol isomerase enzymes protein disulphide isomerase (PDI) and endoplasmic reticulum protein 5 (ERp5) are released by resting and activated platelets. These re-associate with the cell surface where they modulate a range of platelet responses including adhesion, secretion and aggregation. Recent studies suggest the existence of yet uncharacterised platelet thiol isomerase proteins. This study aimed to identify which other thiol isomerase enzymes are present in human platelets. Through the use of immunoblotting, flow cytometry, cell-surface biotinylation and gene array analysis, we report the presence of five additional thiol isomerases in human and mouse platelets and megakaryocytes, namely; ERp57, ERp72, ERp44, ERp29 and TMX3. ERp72, ERp57, ERp44 and ERp29 are released by platelets and relocate to the cell surface following platelet activation. The transmembrane thiol isomerase TMX3 was also detected on the platelet surface but does not increase following activation. Extracellular PDI is also implicated in the regulation of coagulation by the modulation of tissue factor activity. ERp57 was identified within platelet-derived microparticle fractions, suggesting that ERp57 may also be involved in the regulation of coagulation as well as platelet function. These data collectively implicate the expanding family of platelet-surface thiol isomerases in the regulation of haemostasis.

Sulforaphane protects cortical neurons against 5-S-cysteinyl-dopamine-induced toxicity through the activation of ERK1/2, Nrf-2 and the upregulation of detoxification enzymes

The degeneration of dopaminergic neurons in the substantia nigra has been linked to the formation of the endogenous neurotoxin 5-S-cysteinyl-dopamine. Sulforaphane (SFN), an isothiocyanate derived from the corresponding precursor glucosinolate found in cruciferous vegetables has been observed to exert a range of biological activities in various cell populations. In this study, we show that SFN protects primary cortical neurons against 5-S-cysteinyl-dopamine induced neuronal injury. Pre-treatment of cortical neurons with SFN (0.01-1 microM) resulted in protection against 5-S-cysteinyl-dopamine-induced neurotoxicity, which peaked at 100 nM. This protection was observed to be mediated by the ability of SFN to modulate the extracellular signal-regulated kinase 1 and 2 and the activation of Kelch-like ECH-associated protein 1/NF-E2-related factor-2 leading to the increased expression and activity of glutathione-S-transferase (M1, M3 and M5), glutathione reductase, thioredoxin reductase and NAD(P)H oxidoreductase 1. These data suggest that SFN stimulates the NF-E2-related factor-2 pathway of antioxidant gene expression in neurons and may protect against neuronal injury relevant to the aetiology of Parkinson's disease.

Fatty acid compositions of inositol and choline phospholipids of breast tumours and normal breast tissue

The fatty acid compositions of the -choline and -inositol phospholipids of breast tumours of women undergoing surgery for treatment of breast disease (malignant n = 12; benign n = 10) and normal breast tissue of women undergoing breast reduction surgery (n = 6) were determined. The fatty acid compositions of erythrocyte phospholipids were also determined in the same subjects and in an additional number of normal healthy volunteers (n = 16). Levels of oleic acid were lower in both phospholipid fractions of erythrocytes of women with breast disease and in the phosphatidylcholine fraction of breast tumours compared with normal breast tissue. Significantly higher levels of linoleic acid were found in erythrocytes of tumour-bearing subjects and a similar trend was evident in the phosphatidylcholine fraction of tumour compared with normal breast tissues. Conversely, lower levels of two of the products of linoleic acid chain elongation and desaturation, dihomogamma-linolenic and arachidonic acids, were found in the erythrocyte phospholipids of tumour-bearing subjects and in the choline phospholipids of breast tumour tissues. These data suggest that in women with breast disease, there may be inhibition of 6-desaturase, and enhanced activity of 9-desaturase, enzymes which play an important role in determining membrane phospholipid fatty acid composition. This pattern of altered fatty acid composition characteristic of erythrocyte phospholipids of tumour-bearing subjects and phosphatidylcholine of breast tumour tissue was less evident in the case of the breast tumour phosphatidylinositol in which differences other than those described were seen.

Improved process topology for membrane distillation

In membrane distillation in a conventional membrane module, the enthalpies of vaporisation and condensation are supplied and removed by changes in the temperatures of the feed and permeate streams, respectively. Less than 5% of the feed can be distilled in a single pass, because the potential changes in the enthalpies of the liquid streams are much smaller than the enthalpy of vaporisation. Furthermore, the driving force for mass transfer reduces as the feed stream temperature and vapour pressure fall during distillation. These restrictions can be avoided if the enthalpy of vaporisation is uncoupled from the heat capacities of the feed and permeate streams. A specified distillation can then be effected continuously in a single module. Calculations are presented which estimate the performance of a flat plate unit in which the enthalpy of distillation is supplied and removed by the condensing and boiling of thermal fluids in separate circuits, and the imposed temperature difference is independent of position. Because the mass flux through the membrane is dependent on vapour pressure, membrane distillation is suited to applications with a high membrane temperature. The maximum mass flux in the proposed module geometry is predicted to be 30 kg/m2 per h at atmospheric pressure when the membrane temperature is 65°C. Operation at higher membrane temperatures is predicted to raise the mass flux, for example to 85 kg/m2 per h at a membrane temperature of 100°C. This would require pressurisation to 20 bar to prevent boiling at the heating plate of the feed channel. Pre-pressurisation of the membrane pores and control of the dissolved gas concentrations in the feed and the recyled permeate should be investigated as a means to achieve high temperature membrane distillation without pore penetration and wetting.

Direct contact membrane distillation

This review looks at the work carried out over the past 15 years on membrane distillation and reports the conditions utilized for research. The process is still used mainly at the laboratory scale, but a few pilot plants have been built across the world, mostly for desalination and the production of potable water. Studies into membrane distillation have been concerned with the effect of mass transfer, heat transfer, and stirring rate, but the most important effect that has to be considered with this process is temperature polarization. A section on temperature polarization and the effect of boundary layers is included in this review.

Permeate flux modeling of membrane distillation

This paper concerns the modeling of membrane distillation. The model developed has been used to predict permeate fluxes using different initial operating conditions. PVDF and PTFE membranes were successfully used in a flat plate module to experimentally confirm the theoretical results. The correlation between theory and experiment was close for both membranes. The PTFE membranes produced higher fluxes than PVDF. A Versapor membrane was also used for this work. This membrane is a composite, with a thin porous layer on a support layer. It was found not to be suitable for membrane distillation. A comparison of the heat flux was also carried out. Again, there was good correlation between theory and experiment

Advances in module design for membrane distillation

This review looks at the work carried out over the past 15 years on membrane distillation and reports the conditions utilized for research. The process is still used mainly at the laboratory scale, but a few pilot plants have been built across the world, mostly for desalination and the production of potable water. Studies into membrane distillation have been concerned with the effect of mass transfer, heat transfer, and stirring rate, but the most important effect that has to be considered with this process is temperature polarization. A section on temperature polarization and the effect of boundary layers is included in this review.

Tissue engineering a fetal membrane

The aim of this study was to construct an artificial fetal membrane (FM) by combination of human amniotic epithelial stem cells (hAESCs) and a mechanically enhanced collagen scaffold containing encapsulated human amniotic stromal fibroblasts (hASFs). Such a tissue-engineered FM may have the potential to plug structural defects in the amniotic sac after antenatal interventions, or to prevent preterm premature rupture of the FM. The hAESCs and hASFs were isolated from human fetal amniotic membrane (AM). Magnetic cell sorting was used to enrich the hAESCs by positive ATP-binding cassette G2 selection. We investigated the use of a laminin/fibronectin (1:1)-coated compressed collagen gel as a novel scaffold to support the growth of hAESCs. A type I collagen gel was dehydrated to form a material mimicking the mechanical properties and ultra-structure of human AM. hAESCs successfully adhered to and formed a monolayer upon the biomimetic collagen scaffold. The resulting artificial membrane shared a high degree of similarity in cell morphology, protein expression profiles, and structure to normal fetal AM. This study provides the first line of evidence that a compacted collagen gel containing hASFs could adequately support hAESCs adhesion and differentiation to a degree that is comparable to the normal human fetal AM in terms of structure and maintenance of cell phenotype.

Antioxidant enzymes, inflammatory indices and lifestyle factors in older men: a cohort analysis

We examined the relationship between blood antioxidant enzyme activities, indices of inflammatory status and a number of lifestyle factors in the Caerphilly prospective cohort study of ischaemic heart disease. The study began in 1979 and is based on a representative male population sample. Initially 2512 men were seen in phase I, and followed-up every 5 years in phases II and III; they have recently been seen in phase IV. Data on social class, smoking habit, alcohol consumption were obtained by questionnaire, and body mass index was measured. Antioxidant enzyme activities and indices of inflammatory status were estimated by standard techniques. Significant associations were observed for: age with α-1-antichymotrypsin (p<0.0001) and with caeruloplasmin, both protein and oxidase (p<0.0001); smoking habit with α-1-antichymotrypsin (p<0.0001), with caeruloplasmin, both protein and oxidase (p<0.0001) and with glutathione peroxidose (GPX) (p<0.0001); social class with α-1-antichymotrypsin (p<0.0001), with caeruloplasmin both protein (p<0.001) and oxidase (p<0.01) and with GPX (p<0.0001); body mass index with α-1-antichymotrypsin (p<0.0001) and with caeruloplasmin protein (p<0.001). There was no significant association between alcohol consumption and any of the blood enzymes measured. Factor analysis produced a three-factor model (explaining 65.9% of the variation in the data set) which appeared to indicate close inter-relationships among antioxidants.

New insights on regulation of LMTK2, a membrane kinase integrating pathways central to neurodegeneration

In a short communication in this issue (Manser et al. 2012), Christopher Miller’s group at the Institute of Psychiatry, King’s College London present an elegant and convincing set of experiments using molecular techniques to show that a brain-enriched membrane-associated protein kinase, lemur tyrosine kinase-2 (LMTK2), is directly phosphorylated by the cyclin-dependent kinase-5/p35 and this event is sufficient for LMTK2 to phosphorylate an abundant protein phosphatase, PP1C. LMTK2 has been little studied to date and, despite its name, is a kinase which phosphorylates serine or threonine residues of protein substrates. The paper adds to the evidence that this enzyme is a potentially important mediator positioned to integrate a number of intracellular signalling pathways relevant to neurodegeneration.