Poly(acrylonitrile)chitosan composite membranes for urease immobilization

(Poly)acrylonitrile/chitosan (PANCHI) composite membranes were prepared. The chitosan layer was deposited on the surface as well as on the pore walls of the base membrane. This resulted in the reduction of the pore size of the membrane and in an increase of their hydrophilicity. The pore structure of PAN and PANCHI membranes were determined by TEM and SEM analyses. It was found that the average size of the pore under a selective layer base PAN membrane is 7 microm, while the membrane coated with 0.25% chitosan shows a reduced pore size--small or equal to 5 microm and with 0.35% chitosan--about 4 microm. The amounts of the functional groups, the degree of hydrophilicity and transport characteristics of PAN/Chitosan composite membranes were determined. Urease was covalently immobilized onto all kinds of PAN/chitosan composite membranes using glutaraldehyde. Both the amount of bound protein and relative activity of immobilized urease were measured. The highest activity (94%) was measured for urease bound to PANCHI2 membranes (0.25% chitosan). The basic characteristics (pH(opt), pH(stability), T(opt), T(stability), heat inactivation and storage stability) of immobilized urease were determined. The obtained results show that the poly(acrylonitrile)chitosan composite membranes are suitable for enzyme immobilization.     

Simple criterion for selection of flavonoid compounds with anti-HIV activity

Flavonoid compounds represent an important natural source of antiretrovirals for AIDS therapy due to their significant anti-HIV-1 activity and low toxicity. Here we propose a simple theoretical criterion to discriminate active from inactive flavonoids that is suitable for rapid in silico screening of flavonoid libraries, and selection and optimization of lead compounds with anti-HIV-1 activity.     

Effects of short-term magnesium supplementation on ionized,total magnesium and other relevant electrolytes levels

BioMetals - This study aimed to investigate the short-term effects of three magnesium (Mg) dietary supplements containing mineral immediately available for absorption on Mg biochemical status...     

Coordinated activation of AMP‐activated protein kinase,extracellular signal‐regulated kinase,and autophagy regulates phorbol myristate acetate‐induced differentiation of SH‐SY5Y neuroblastoma cells

We explored the interplay between the intracellular energy sensor AMP‐activated protein kinase (AMPK), extracellular signal‐regulated kinase (ERK), and autophagy in phorbol myristate acetate (PMA)‐induced neuronal differentiation of SH‐SY5Y human neuroblastoma cells. PMA‐triggered expression of neuronal markers (dopamine transporter, microtubule‐associated protein 2, β‐tubulin) was associated with an autophagic response, measured by the conversion of microtubule‐associated protein light chain 3 (LC3)‐I to autophagosome‐bound LC3‐II, increase in autophagic flux, and expression of autophagy‐related (Atg) proteins Atg7 and beclin‐1. This coincided with the transient activation of AMPK and sustained activation of ERK. Pharmacological inhibition or RNA interference‐mediated silencing of AMPK suppressed PMA‐induced expression of neuronal markers, as well as ERK activation and autophagy. A selective pharmacological blockade of ERK prevented PMA‐induced neuronal differentiation and autophagy induction without affecting AMPK phosphorylation. Conversely, the inhibition of autophagy downstream of AMPK/ERK, either by pharmacological agents or LC3 knockdown, promoted the expression of neuronal markers, thus indicating a role of autophagy in the suppression of PMA‐induced differentiation of SH‐SY5Y cells. Therefore, PMA‐induced neuronal differentiation of SH‐SY5Y cells depends on a complex interplay between AMPK, ERK, and autophagy, in which the stimulatory effects of AMPK/ERK signaling are counteracted by the coinciding autophagic response.

     

Immobilization of lipase from Candida rugosa on Sepabeads(®): the effect of lipase oxidation by periodates

The objective of this paper was the investigation of a suitable Sepabeads^? support and method for immobilization of lipase from Candida rugosa. Three different supports were used, two with amino groups, (Sepabeads^? EC-EA and Sepabeads^? EC-HA), differing in spacer length (two and six carbons, respectively) and one with epoxy group (Sepabeads^? EC-EP). Lipase immobilization was carried out by two conventional methods (via epoxy groups and via glutaraldehyde), and with periodate method for modification of lipase. The results of activity assays showed that lipase retained 94.8% or 87.6% of activity after immobilization via epoxy groups or with periodate method, respectively, while glutaraldehyde method was inferior with only 12.7% of retention. The immobilization of lipase, previously modified by periodate oxidation, via amino groups has proven to be more efficient than direct immobilization of lipase via epoxy groups. In such a way immobilized enzyme exhibited higher activity at high reaction temperatures and higher thermal stability.     

Physical activity and natural anti-VIP antibodies: potential role in breast and prostate cancer therapy

Background

There is convincing evidence from numerous clinical and epidemiological studies that physical activity can reduce the risk for breast and prostate cancer. The biological mechanisms underlying this phenomenon remain elusive. Herein we suggest a role for naturally produced antibodies reactive with the vasoactive intestinal peptide (VIP) in the suppression of breast and prostate cancer, which we believe could offer a possible molecular mechanism underlying control of these cancers by physical exercise.

Methodology and Results

We found that sera from individuals having breast and prostate cancers have decreased titers of VIP natural antibodies as demonstrated by a lower reactivity against peptide NTM1, having similar informational and structural properties as VIP. In contrast, sera collected from elite athletes, exhibited titers of natural NTM1-reactive antibodies that are significantly increased, suggesting that physical activity boosts production of these antibodies.

Significance

Presented results suggest that physical exercise stimulates production of natural anti-VIP antibodies and likely results in suppression of VIP. This, in turn, may play a protective role against breast and prostate cancers. Physical exercise should be further investigated as a potential tool in the treatment of these diseases.     

Strawberry polyphenols attenuate ethanol-induced gastric lesions in rats by activation of antioxidant enzymes and attenuation of MDA increase

Background and Aim

Free radicals are implicated in the aetiology of gastrointestinal disorders such as gastric ulcer, colorectal cancer and inflammatory bowel disease. Strawberries are common and important fruit due to their high content of essential nutrient and beneficial phytochemicals which seem to have relevant biological activity on human health. In the present study we investigated the antioxidant and protective effects of three strawberry extracts against ethanol-induced gastric mucosa damage in an experimental in vivo model and to test whether strawberry extracts affect antioxidant enzyme activities in gastric mucosa.

Methods/Principal Findings

Strawberry extracts were obtained from Adria, Sveva and Alba cultivars. Total antioxidant capacity and radical scavenging capacity were performed by TEAC, ORAC and electron paramagnetic resonance assays. Identification and quantification of anthocyanins was carried out by HPLC-DAD-MS analyses. Different groups of animals received 40 mg/day/kg body weight of strawberry crude extracts for 10 days. Gastric damage was induced by ethanol. The ulcer index was calculated together with the determination of catalase and SOD activities and MDA contents. Strawberry extracts are rich in anthocyanins and present important antioxidant capacity. Ethanol caused severe gastric damage and strawberry consumption protected against its deleterious role. Antioxidant enzyme activities increased significantly after strawberry extract intake and a concomitantly decrease in gastric lipid peroxidation was found. A significant correlation between total anthocyanin content and percent of inhibition of ulcer index was also found.

Conclusions

Strawberry extracts prevented exogenous ethanol-induced damage to rats'' gastric mucosa. These effects seem to be associated with the antioxidant activity and phenolic content in the extract as well as with the capacity of promoting the action of antioxidant enzymes. A diet rich in strawberries might exert a beneficial effect in the prevention of gastric diseases related to generation of reactive oxygen species.     

Partitioning of tRNA-dependent Editing between Pre- and Post-transfer Pathways in Class I Aminoacyl-tRNA Synthetases

Hydrolytic editing activities are present in aminoacyl-tRNA synthetases possessing reduced amino acid discrimination in the synthetic reactions. Post-transfer hydrolysis of misacylated tRNA in class I editing enzymes occurs in a spatially separate domain inserted into the catalytic Rossmann fold, but the location and mechanisms of pre-transfer hydrolysis of misactivated amino acids have been uncertain. Here, we use novel kinetic approaches to distinguish among three models for pre-transfer editing by Escherichia coli isoleucyl-tRNA synthetase (IleRS). We demonstrate that tRNA-dependent hydrolysis of noncognate valyl-adenylate by IleRS is largely insensitive to mutations in the editing domain of the enzyme and that noncatalytic hydrolysis after release is too slow to account for the observed rate of clearing. Measurements of the microscopic rate constants for amino acid transfer to tRNA in IleRS and the related valyl-tRNA synthetase (ValRS) further suggest that pre-transfer editing in IleRS is an enzyme-catalyzed activity residing in the synthetic active site. In this model, the balance between pre-transfer and post-transfer editing pathways is controlled by kinetic partitioning of the noncognate aminoacyl-adenylate. Rate constants for hydrolysis and transfer of a noncognate intermediate are roughly equal in IleRS, whereas in ValRS transfer to tRNA is 200-fold faster than hydrolysis. In consequence, editing by ValRS occurs nearly exclusively by post-transfer hydrolysis in the editing domain, whereas in IleRS both pre- and post-transfer editing are important. In both enzymes, the rates of amino acid transfer to tRNA are similar for cognate and noncognate aminoacyl-adenylates, providing a significant contrast with editing DNA polymerases.     

Characterization of Erwinia amylovora strains from Bulgaria by pulsed-field gel electrophoresis

The aim of this study was to characterize genetically Bulgarian Erwinia amylovora strains using pulsed-field gel electrophoresis (PFGE) analysis. Fifty E. amylovora strains isolated from different hosts, locations, as well as in different years were analysed by PFGE after XbaI, SpeI, and XhoI digestion of the genomic DNA. The strains were distributed into four groups according to their XbaI-generated profile. About 82% of the strains displayed a PFGE profile identical to that of type Pt2. Three strains belonged to the Central Europe Pt1 type. Two new PFGE profiles, not reported so far, were established--one for a strain isolated from Malus domestica and another for all Fragaria spp. strains. The same grouping of the strains was obtained after analysis of the SpeI digestion patterns. On the basis of PFGE profiles, after XbaI and SpeI digestion, a genetic differentiation between the strains associated with subfamily Maloideae and subfamily Rosoideae was revealed. The presence of more than one PFGE profile in the population of E. amylovora in Bulgaria suggests a multiple source of inoculum.