Comparative study of periphyton colonisation on common reed (Phragmites australis) and artificial substrate in a shallow lake,Manyas, Turkey

Hydrobiologia - Colonisation of epiphytic algae on the common reed (Phragmites australis) and on glass slides were studied during a twenty-four week exposure period in a shallow, turbid lake,...     

Exploring the importance of institutional contexts for the development of ethnic stereotypes: a comparison of schools in Belgium and England

This article suggests the usefulness of an ecological approach in studying the development of teachers' ethnic stereotypes in schools. It builds on existing research in this area by exploring the importance of nationally specific educational contexts and school characteristics on the development of teachers' stereotypes of Turkish minority students. Observation and interview data from case-study research involving one Flemish (Belgian) and one English secondary, multicultural inner-city school suggest differences between Flemish and English teachers' ethnic stereotypes. These differences can in part be explained by the influence of nationally specific regulations governing teachers' power to evaluate students, a nationally specific policy on ethnic minority cultures and needs, the ethnic and gender composition of the school's student and staff population, and the enforcement of an inclusive school policy by the school's senior management. The conclusions discuss implications for further research on ethnic stereotyping and discrimination in schools.     

Purification of heterotrimeric G protein alpha subunits by GST-Ric-8 association: primary characterization of purified G alpha(olf)

Ric-8A and Ric-8B are nonreceptor G protein guanine nucleotide exchange factors that collectively bind the four subfamilies of G protein α subunits. Co-expression of Gα subunits with Ric-8A or Ric-8B in HEK293 cells or insect cells greatly promoted Gα protein expression. We exploited these characteristics of Ric-8 proteins to develop a simplified method for recombinant G protein α subunit purification that was applicable to all Gα subunit classes. The method allowed production of the olfactory adenylyl cyclase stimulatory protein Gα(olf) for the first time and unprecedented yield of Gα(q) and Gα(13). Gα subunits were co-expressed with GST-tagged Ric-8A or Ric-8B in insect cells. GST-Ric-8·Gα complexes were isolated from whole cell detergent lysates with glutathione-Sepharose. Gα subunits were dissociated from GST-Ric-8 with GDP-AlF(4)(-) (GTP mimicry) and found to be >80% pure, bind guanosine 5'-[γ-thio]triphosphate (GTPγS), and stimulate appropriate G protein effector enzymes. A primary characterization of Gα(olf) showed that it binds GTPγS at a rate marginally slower than Gα(s short) and directly activates adenylyl cyclase isoforms 3, 5, and 6 with less efficacy than Gα(s short).     

Effects of various inhibitors on β-galactosidase purified from the thermoacidophilic <Emphasis Type="Italic">Alicyclobacillus acidocaldarius</Emphasis> subsp. <Emphasis Type="Italic">Rittmannii</Emphasis> isolated from Antarctica

β-Galactosidase purified from the thermoacidophilic Alicyclobacillus acidocaldarius subsp. rittmannii isolated from Antarctica is a member of the GH42 family. The enzyme was not effected by various concentrations of its reaction product glucose, but was greatly inhibited by the other reaction product galactose using both substrates, ONPG and lactose. Linewever-Burk plot analysis derived from both ONPG and lactose hydrolysis results showed that galactose is a mixed-type inhibitor of the purified β-galactosidase. The enzyme was slightly activated by Mg²⁺ (13% at 20 mM), while inhibited at higher concentrations of Ca⁺² (33% at 10 mM), Zn⁺² (86% at 8 mM) and Cu⁺² (87% at 4 mM). The enzyme activity was not significantly altered by the metal ion chelators EDTA and 1,10-phenanthroline up to 20 mM, indicating that this enzyme is not a metalloenzyme. 2-Mercaptoethanol and DTT were found to enhance β-galactosidase activity, while p-chloromercuribenzoic acid (PCMB) completely inhibited enzymatic activity (97% at 1 mM; 99.7% at 2 mM), indicating at least one essential Cys residue modified by the reagents in the active site of β-galactosidase. Iodoacetamide and Nethylmaleimide had little effect on the β-galactosidase. Phenylmethylsulfonyl fluoride (PMSF) inhibited the enzyme strongly (19.8% at 1 mM; 71.9% at 10 mM), also showing the participation of serine for enzyme activity.     

Levan nanostructured thin films by MAPLE assembling

Synthesis of nanostructured thin films of pure and oxidized levan exopolysaccharide by matrix-assisted pulsed laser evaporation is reported. Solutions of pure exopolysaccharides in dimethyl sulfoxide were frozen in liquid nitrogen to obtain solid cryogenic pellets that have been used as targets in pulsed laser evaporation experiments with a KrF* excimer source. The expulsed material was collected and assembled onto glass slides and Si wafers. The contact angle studies evidenced a higher hydrophilic behavior in the case of oxidized levan structures because of the presence of acidic aldehyde-hydrogen bonds of the coating formed after oxidation. The obtained films preserved the base material composition as confirmed by Fourier transform infrared spectroscopy. They were compact with high specific surface areas, as demonstrated by scanning electron and atomic force microscopy investigations. In vitro colorimetric assays revealed a high potential for cell proliferation for all coatings with certain predominance for oxidized levan.     

Depth profiles of cyanobacterial hepatotoxins (microcystins) in three Turkish freshwater lakes

The Turkish freshwater lakes, Sapanca, Iznik and Taskisi (Calticak) have been enriched with nutrients from agriculture and domestic sources for many years. A major bloom of cyanobacteria (blue-green algae) in Lake Sapanca was recorded in May 1997, closely followed by a fish kill. Investigations were subsequently made on the cyanobacteria and water quality of the lakes, including analysis for cyanobacterial hepatotoxins (microcystins) in the filtered particulate fraction. Samples, taken from the beginning of May to end of August 1998, were analysed for microcystins by high–performance liquid chromatography with photodiode array detection (HPLC-PDA), protein phosphatase inhibition assay (PPIA) and an enzyme-linked immunosorbent assay (ELISA). No microcystins were detected in the water column in Lake Sapanca above 10 m, but toxins were found in filtered cyanobacterial samples from 20 m depth at a concentration of 3.65 μg l^?1 microcystin–LR equivalents. Ninety percent of the microcystin pool detected in L. Sapanca was found between depths of 15 and 25 m. The principal microcystin detected by HPLC-PDA was similar to microcystin–RR. Two unidentified microcystin variants were found in Lake Taskisi surface samples at a concentration of 2.43 μg l^?1 microcystin–LR equivalents in the filtered cyanobacterial cell fraction. Although 10 water samples (10 × 5 l) were taken from Lake Iznik (surface to 20 m, 5 m intervals), no microcystins were detected by HPLC-PDA (limit of detection 10 ng). The depth at which microcystins were detected in L. Sapanca coincided with the draw-off depth for the drinking water supply for the city of Sakarya     

Inflammatory response to cold injury in remote organs is reduced by corticotropin-releasing factor

Current experimental evidence concerning the potential activity of corticotropin releasing factor (CRF) in inflammatory processes still remains controversial. To determine whether CRF has protective effects on three remote organs (liver, lung and stomach) affected by cold injury and to characterize the role of neutrophils in cold-induced inflammation, dorsums of anesthetized rats were exposed for 5 min to a 22% NaCl solution maintained at -20+/-0.5 degrees C and the rats were sacrificed at 24 h after the cold injury. The results indicate that cold-exposure-induced edema in the liver, lung and stomach was blocked by subcutaneous (s.c.; 1.2 and 12 nmol/kg; 30 min before cold trauma) CRF pretreatment, while the central administration of CRF (intracisternally (i.c.); 0.30 and 1.5 nmol/rat; 15 min before cold) had the similar effect at the higher dose. Histological assessment and the tissue myeloperoxidase activities also revealed that CRF given peripherally has a protective role in damage generation. Moreover, CRF had a facilitatory effect in the recovery of the body temperature following cold exposure. In conclusion, CRF is likely to act on its peripheral receptors in the inflamed remote organs, suppressing the edematogenic effects of inflammatory mediators, some of which are neutrophil-derived.     

Effect of exogenous melatonin on ethanol-induced changes in Na(+),K(+)- and Ca(2+)-ATPase activities in rat synaptosomes

In the present study, the effects of acute ethanol (EtOH) toxicity and of exogenous melatonin (MLT) on this toxicity were examined by measuring membrane-bound ATPases and acetylcholinesterase activities in rat synaptosomal membranes. The concentrations of plasma -tocopherol and adrenal ascorbic acid (AA) were also measured. Synaptosomal Na⁺,K⁺-ATPase and Ca²⁺-ATPase activities were significantly depressed in acute EtOH-intoxicated rats compared with controls, while acetylcholinesterase activity remained unaltered. Pretreatment with MLT (10 mg/kg) prior to acute EtOH administration prevented EtOH-induced inhibition of ATPases. Adrenal AA and plasma -tocopherol levels were also depressed regardless of MLT pretreatment. MLT treatment alone affected neither membrane-bound enzyme activities nor tissue and blood levels of vitamins C and E. It is concluded that acute EtOH intoxication disturbs neural transport functions through the membrane-bound ATPase activity depression. Reduced AA and -tocopherol levels may contribute to the neurodegenerative effects of EtOH. However, pretreatment with a high dose of MLT before EtOH administration may be beneficial to prevent EtOH-induced toxicity on ATPase-mediated neural transport functions.     

Effects of neutral,cationic, and anionic chromium ascorbate complexes on isolated human mitochondrial and genomic DNA

The relative activities of neutral, cationic, and anionic chromium ascorbate complexes toward isolated human mitochondrial and genomic DNA were investigated at physiologically relevant conditions by agarose gel electrophoresis. A direct relationship between the charge of the Cr(III) species and their DNA-damaging properties was found. The cationic species were found to be fully capable of DNA-cleavage, even in short incubation periods. Incubations were also performed in the presence of amino acids. No apparent effect was observed under the applied experimental conditions to facilitate or prevent damage through the ternary amino acid-Cr-DNA adduct formation or binary chromium-amino acid complex formation.     

Isolation and identification of alkaline protease producer halotolerantBacillus licheniformis strain BA17

An alkaline protease producerBacillus licheniformis strain was isolated from Van Lake in Turkey. The strain is Gram positive, aerobic, motile, sporulating rod-shaped bacterium. Spores were ellipsoidal and positioned central in nonswollen sporangium. The cells were able to grow well at a pH range of 5.7–10. The optimal growth temperature was found to be 37 °C. Growth at a wide range of NaCl concentration (from 0 to 20%) showed that BA17 is halotolerant. Main fatty acid composition of BA17 was anteiso-C15:0 and iso-C15∶0. The strain was presumptively identified asB. licheniformis according to 16S rDNA gene sequence analysis. The most appropriate medium for the growth and protease production is composed of 0.5% yeast extract, 0.5% NaNO₃, 0.02% MgSO₄\7H₂O, 0.1% K₂HPO₄ and 0.5% maltose. The optimum temperature and pH of the alkaline protease of strain BA17 were found to be 60 °C and pH 11, respectively. The activity was completely lost in the presence of PMSF, suggesting that the preparation contains serine-alkaline protease(s).