Some of the properties of flame retardant medium density fiberboard made from rubberwood and recycled containers containing aluminum trihydroxide

The flame retardancy of medium density fiberboard (MDF) made from mixture of rubberwood fibers and recycled old corrugated containers was studied. Aluminum trihydroxide (ATH) was used as a fire retardant additive and mixed with the fibers to manufacture experimental MDF panels using wet process. Phenol formaldehyde (PF) resin in liquid, 2% based on oven dry weight of fibers, was used along with 0%, 10%, 15% and 20% of ATH. The flame retardant test was done using the limiting oxygen index (LOI) test. The other properties investigated include internal bond strength, thickness swelling and water absorption. The results showed that ATH loading increased as the LOI of MDF increased. This demonstrated that ATH could improved the fire retardant property of MDF at sufficient loading. An increase in concentration of ATH showed an increase in the IB values of MDF made without resin. MDF panels made without resin showed a progressive increase in internal bond as the composition of recycled old corrugated containers fiber increased. Addition of resin improved internal bond strength and reduced thickness swelling, and water absorption. Thickness swelling of panel increased as the composition of recycled old corrugated containers fiber increased. Scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) showed that there is indication of ATH and resin filling the void space in between fibers.     

Effects of colloidal fouling and gas sparging on microfiltration of yeast suspension

Cross-flow microfiltration is an important step in separating Baker’s yeast (Saccharomyces cerevisiae) from aqueous suspension in many processes. However the permeate flux often declines rapidly due to colloidal fouling of membranes and concentration polarisation. The present work explores the possibility of maintaining acceptable permeate flux by co-current sparging of gas along with the feed, which would scour away colloidal deposits and reduce concentration polarisation of membranes. In this work, both washed and unwashed yeast were used to study the effect of washing to reduce protein fouling of membranes. It was found that permeate flux increased by 45% for liquid throughput of 75 kg/h for a feed concentration of 2.0 kg/m³ of washed yeast as compared with unwashed yeast suspension without gas sparging. For washed yeast suspension, the increase in gas flow rate from 0.5 lpm to 1.5 lpm (30 l/h to 90 l/h) had beneficial effect on permeate flux. It is concluded that in the present case, the gas flow rate should be less than or equal to the liquid flow rate for enhancement of permeates flux.     

The arginine regulatory protein mediates repression by arginine of the operons encoding glutamate synthase and anabolic glutamate dehydrogenase in Pseudomonas aeruginosa

The arginine regulatory protein of Pseudomonas aeruginosa, ArgR, is essential for induction of operons that encode enzymes of the arginine succinyltransferase (AST) pathway, which is the primary route for arginine utilization by this organism under aerobic conditions. ArgR also induces the operon that encodes a catabolic NAD(+)-dependent glutamate dehydrogenase (GDH), which converts l-glutamate, the product of the AST pathway, in alpha-ketoglutarate. The studies reported here show that ArgR also participates in the regulation of other enzymes of glutamate metabolism. Exogenous arginine repressed the specific activities of glutamate synthase (GltBD) and anabolic NADP-dependent GDH (GdhA) in cell extracts of strain PAO1, and this repression was abolished in an argR mutant. The promoter regions of the gltBD operon, which encodes GltBD, and the gdhA gene, which encodes GdhA, were identified by primer extension experiments. Measurements of beta-galactosidase expression from gltB::lacZ and gdhA::lacZ translational fusions confirmed the role of ArgR in mediating arginine repression. Gel retardation assays demonstrated the binding of homogeneous ArgR to DNA fragments carrying the regulatory regions for the gltBD and gdhA genes. DNase I footprinting experiments showed that ArgR protects DNA sequences in the control regions for these genes that are homologous to the consensus sequence of the ArgR binding site. In silica analysis of genomic information for P. fluorescens, P. putida, and P. stutzeri suggests that the findings reported here regarding ArgR regulation of operons that encode enzymes of glutamate biosynthesis in P. aeruginosa likely apply to other pseudomonads.     

Genotoxicity of goniothalamin in CHO cell line

Goniothalamin (GTN) is a styrylpyrrone derivative from Goniothalamus umbrosus and other Annonaceae species. It has been shown to have anti-cancer and apoptosis-inducing properties against various human tumour and animal cell lines. The compound has also been shown to be active in vivo against DMBA-induced rat mammary tumours and was reported as an anti-fertility agent in rats. The aim of our study was to assess the genotoxicity of GTN in CHO cells using the UKEMS guidelines. A metabolic activation fraction (S9) was prepared according to standard methods. The methylthiazoletetrazolium (MTT) screening assay was then carried out to determine the cytotoxicity index (IC50) of GTN. The average IC50 value was 12.45 (+/- 3.63)microM. The mitotic index (MI) assay was then performed to determine the clastogenicity indices (MI(C25), MI(C50) and MI(C100)) of GTN. The chromosome aberration (CA) induction assay using air-dried metaphase spread was then performed to investigate the clastogenic effects of goniothalamin. Benzo[a]pyrene (BaP) and ethylmethanesulphonate (EMS) were used as positive controls in the presence and absence of S9 metabolic activation, respectively. The anti-genotoxicity effect of GTN was also assessed using a combination of GTN and EMS, and GTN and BaP. Dose-responses of CA frequencies were determined for both, the genotoxicity and anti-genotoxicity effects. GTN on its own and when combined with positive controls, was found to induce and enhance CA, respectively. Chromatid and whole chromosome breaks/gaps, as well as interchanges, endoreduplications and ring chromosomes were the main types of aberration induced by GTN. The overall clastogenic effect of GTN was statistically significant. In conclusion, GTN is potentially a genotoxic or clastogenic substance without any anti-genotoxic properties.     

NMR studies of an immunomodulatory benzodiazepine binding to its molecular target on the mitochondrial F1F0‐ATPase

Bz‐423 is an inhibitor of the mitochondrial F₁F₀‐ATPase, with therapeutic properties in murine models of immune diseases. Here, we study the binding of a water‐soluble Bz‐423 analog (5‐(3‐(aminomethyl)phenyl)‐7‐chloro‐ 1‐methyl‐3‐(naphthalen‐2‐ylmethyl)‐1H‐benzo][e][1,4]diazepin‐2(3H)‐one); (1) to its target subunit on the enzyme, the oligomycin sensitivity conferring protein (OSCP), by NMR spectroscopy using chemical shift perturbation and cross‐relaxation experiments. Titration experiments with constructs representing residues 1–120 or 1–145 of the OSCP reveals that (a) 1 binds to a region of the protein, at the minimum, comprising residues M51, L56, K65, V66, K75, K77, and N92, and (b) binding of 1 induces conformational changes in the OSCP. Control experiments employing a variant of 1 in which a key binding element on the small molecule was deleted; it had no perturbational effect on the spectra of the OSCP, which indicates that the observed changes with 1 represent specific binding interactions. Collectively, these data suggest that 1 might inhibit the enzyme through an allosteric mechanism where binding results in conformational changes that perturb the OSCP‐F₁ interface resulting in disrupted communication between the peripheral stalk and the F₁‐domain of the enzyme. © 2009 Wiley Periodicals, Inc. Biopolymers 29: 85–92, 2010. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com     

Small cytoplasmic domain peptides of natriuretic peptide receptor-C attenuate cell proliferation through Gialpha protein/MAP kinase/PI3-kinase/AKT pathways

The present studies were undertaken to investigate the effect of C-atrial natriuretic peptide (ANP)(4-23) and several peptide fragments containing 12 amino acids from different regions of the cytoplasmic domain of natriuretic peptide receptor (NPR)-C on cell proliferation in the absence or presence of angiotensin (ANG) II, endothelin (ET)-1, and arginine vasopressin (AVP) in A-10 vascular smooth muscle cells (VSMC). The peptide fragments used have either complete G(i) activator sequences K(461)-H(472) (peptide 1) and H(481)-H(492) (peptide 3) or partial G(i) activator sequences R(469)-K(480) (peptide 2) and I(465)-H(472) (peptide Y) with truncated COOH or NH(2) terminus, respectively. The other peptide used had no structural specificity (Q(473)-K(480), peptide X) or was the scrambled peptide control for peptide 1 (peptide Z). ANG II, ET-1 and AVP significantly stimulated DNA synthesis in these cells as determined by [(3)H]thymidine incorporation that was inhibited by peptides 1, 2, and 3 and not by peptides X, Y, and Z in a concentration-dependent manner, with an apparent K(i) between 1 and 10 nM. In addition, C-ANP(4-23), which interacts with NPR-C, also inhibited DNA synthesis stimulated by vasoactive peptides; however, the inhibition elicited by C-ANP(4-23) was not additive with the inhibition elicited by peptide 1. On the other hand, basal DNA synthesis in these cells was not inhibited by C-ANP(4-23) or the peptide fragments. Furthermore, vasoactive peptide-induced stimulation of DNA synthesis was inhibited by PD-98059 and wortmannin, and this inhibition was potentiated by peptide 1. In addition, peptide 1 also inhibited vasoactive peptide-induced phosphorylation of ERK1/2 and AKT and enhanced expression of G(i)alpha proteins. These data suggest that C-ANP(4-23) and small peptide fragments containing 12 amino acids irrespective of the region of the cytoplasmic domain of NPR-C inhibit proliferative responses of vasoactive peptides through G(i)alpha protein and MAP kinase/phosphatidylinositol 3-kinase/AKT pathways.     

Protein adsorption on Ion exchange resin: Estimation of equilibrium isotherm parameters from batch kinetic data

The simple Langmuir isotherm is frequently employed to describe the equilibrium behavior of protein adsorption on a wide variety of adsorbents. The two adjustable parameters of the Langmuir isotherm—the saturation capacity, orq _m, and the dissociation constant,K _d—are usually estimated by fitting the isotherm equation to the equilibrium data acquired from batch equilibration experiments. In this study, we have evaluated the possibility of estimatingq _m andK _d for the adsorption of bovine serum albumin to a cation exchanger using batch kinetic data. A rate model predicated on the kinetic form of the Langmuir isotherm, with three adjustable parameters (q _m,K _d, and a rate constant), was fitted to a single kinetic profile. The value ofq _m determined as the result of this approach was quantitatively consistent with theq _m value derived from the traditional batch equilibrium data. However, theK _d value could not be retrieved from the kinetic profile, as the model fit proved insensitive to this parameter. Sensitivity analysis provided significant insight into the identifiability of the three model parameters.     

G protein-linked cell signaling and cardiovascular functions in diabetes/hyperglycemia

Vascular complications, including impaired contractility and increased cell proliferation, are the most common complications with diabetes. Chronic hyperglycemia seems to be an important contributing factor in this process. Various signaling pathways are implicated in diabetes/hyperglycemia-induced impaired vascular functions. Nonenzymatic glycation, enhanced production of diacylglycerol, increased activity of membranous protein kinase C (PKC), and increased oxidative stress have been proposed to explain the adverse effects of hyperglycemia on vascular smooth muscle cells. Hyperglycemia-induced stimulation of L-type Ca²⁺ channel via G protein-coupled adenylyl cyclase/cAMP and phospholipase C/PKC pathways also has been shown. In addition, hyperglycemia has been reported to decrease the availability of nitric oxide in humans, which may contribute to all the hemodynamic and physiological changes occuring in diabetes. G protein-adenylyl cyclase signaling that plays an important role in the regulation of cardiovascular functions also has been reported to be impaired in diabetes and under hyperglycemic conditions. In this review article, various G protein-linked cell signaling and functions in diabetes and hyperglycemia are discussed.     

Incidence and remediation of fungi in a sick building in Malaysia: a case study

Problems caused by indoor microbial, especially fungal growth, have been further exaggerated by the increased incidence of water intrusions, condensation from air-conditioning system, and other factors. While fungal contamination in a building can be one of the indicators of indoor air quality (IAQ), air quality assessment and remediation should be considered as important and should be carried out systematically. This study reports the incidence and remediation of an excessive fungal growth in a building in Universiti Sains Malaysia (USM), Pulau Pinang, Malaysia. Acting on an official report by the building owner and occupants, an immediate walk-through investigation was carried out between June and December 2009. A thorough sampling comprising swab and spore impactor techniques showed that the colony-forming unit per cubic meter of air (CFU/m³) levels were far above those in the guidelines of most developed countries. Thus, the building was declared a ‘sick building’ and closed to the publics. However, through immediate action with recommended methods to overcome the problem, the premise has been pronounced safe. This is a good example of successful teamwork that involved a continuous investigation by a team of experts along with comprehensive action taken by the occupants and other authorities responsible for the building.