Biomineralization Consolidation of Fresco Wall Paintings Samples by Bacillus sphaericus

Bacterial-induced mineralization has been explored for protection and consolidation of degraded limestone, concrete and plaster by precipitation of calcium carbonate. It is the first time that Bacillus sphaericus was used for consolidating the nonsterilized decayed wall paintings samples by immersing them in sterile nutritional media. The B. sphaericus used in this study produced urease, which catalyzes the hydrolysis of urea (CO(NH₂)₂) into ammonium (NH₄) and carbonate (CO₃^?2) leading to the precipitation of calcium carbonate. The effect of B. sphaericus on wall paintings was determined by recording the evolution of culture media chemistry and examining the treated wall paintings under a scanning electron microscope to show the structural and morphological evolution of calcium carbonate that was investigated in wall paintings models.     

Anaerobic C–H Oxyfunctionalization: Coupling of Nitrate Reduction and Quinoline Hydroxylation in Recombinant Pseudomonas putida

Whole‐cell biocatalysis for C–H oxyfunctionalization depends on and is often limited by O₂ mass transfer. In contrast to oxygenases, molybdenum hydroxylases use water instead of O₂ as an oxygen donor and thus have the potential to relieve O₂ mass transfer limitations. Molybdenum hydroxylases may even allow anaerobic oxyfunctionalization when coupled to anaerobic respiration. To evaluate this option, the coupling of quinoline hydroxylation to denitrification is tested under anaerobic conditions employing Pseudomonas putida (P. putida) 86, capable of aerobic growth on quinoline. P. putida 86 reduces both nitrate and nitrite, but at low rates, which does not enable significant growth and quinoline hydroxylation. Introduction of the nitrate reductase from Pseudomonas aeruginosa enables considerable specific quinoline hydroxylation activity (6.9 U g_CDW^?1) under anaerobic conditions with nitrate as an electron acceptor and 2‐hydroxyquinoline as the sole product (further metabolization depends on O₂). Hydroxylation‐derived electrons are efficiently directed to nitrate, accounting for 38% of the respiratory activity. This study shows that molybdenum hydroxylase‐based whole‐cell biocatalysts enable completely anaerobic carbon oxyfunctionalization when coupled to alternative respiration schemes such as nitrate respiration.     

alpha-Tomatine, the major saponin in tomato, induces programmed cell death mediated by reactive oxygen species in the fungal pathogen Fusarium oxysporum

The tomato saponin alpha-tomatine has been proposed to kill sensitive cells by binding to cell membranes followed by leakage of cell components. However, details of the modes of action of the compound on fungal cells are poorly understood. In the present study, mechanisms involved in alpha-tomatine-induced cell death of fungi were examined using a filamentous pathogenic fungus Fusarium oxysporum. alpha-Tomatine-induced cell death of F. oxysporum (TICDF) occurred only under aerobic conditions and was blocked by the mitochondrial F(0)F(1)-ATPase inhibitor oligomycin, the caspase inhibitor D-VAD-fmk, and protein synthesis inhibitor cycloheximide. Fungal cells exposed to alpha-tomatine showed TUNEL-positive nuclei, depolarization of transmembrane potential of mitochondria, and reactive oxygen species (ROS) accumulation. These results suggest that TICDF occurs through a programmed cell death process in which mitochondria play a pivotal role. Pharmacological studies using inhibitors suggest that alpha-tomatine activates phosphotyrosine kinase and monomeric G-protein signaling pathways leading to Ca(2+) elevation and ROS burst in F. oxysporum cells.     

Mutational spectrum of dihydropyrimidine dehydrogenase gene (DPYD) in the Tunisian population

Dihydropyrimidine dehydrogenase enzyme (DPD) deficiency is a pharmacogenetic syndrome leading to severe side-effects in patients receiving therapies containing the anticancer drug 5-fluorouracil (5-FU). The aim of this population study is to evaluate gene variations in the coding region of the dihydropyrimidine dehydrogenase gene (DPYD) in the Tunisian population. One hundred and six unrelated healthy Tunisian volunteers were genotyped by denaturing HPLC (DHPLC). Twelve variants in the coding region of the DPYD were detected. Allele frequencies of DPYD*5 (A1627G), DPYD*6 (G2194A), DPYD*9A (T85C), A496G, and G1218A were 12.7%, 7.1%, 13.7%, 5.7%, and 0.5%, respectively. The DPYD alleles DPYD*2A (IVS 14+1g>1), DPYD*3 (1897 del C) and DPYD*4 (G1601A) associated with DPD deficiency were absent from the examined subjects. We describe for the first time a new intronic polymorphism IVS 6-29 g>t, found in an allelic frequency of 4.7% in the Tunisian population. Comparing our data with that obtained in Caucasian, Egyptian, Japanese and African-American populations, we found that the Tunisian population resembles Egyptian and Caucasian populations with regard to their allelic frequencies of DPYD polymorphisms. This study describes for the first time the spectrum of DPYD sequence variations in the Tunisian population.     

Effective biofertilizer Trichoderma spp. isolates with enzymatic activity and metabolites enhancing plant growth

International Microbiology - Trichoderma species have been widely recognized as biofertilizer fungi for their ability to produce phytohormones and enhance plant growth. In our current study,...     

A simple and rapid serum bactericidal assay and its evaluation in clinical isolates of Klebsiella pneumoniae

A simple and rapid assay for the determination of serum bactericidal activity was developed and evaluated in 125 clinical isolates of Klebsiella pneumoniae. The serum reactivity against these isolates was concomitantly determined by the conventional viable count technique in order to compare the efficacy of the two techniques. The rapid assay could be completed within 5-8 h and the results were recorded in terms of visible change of colour of the culture medium. Of the 125 strains tested, more than 50% were found to be resistant to 20% normal human serum. There was an excellent agreement between the two methods. The degree of discordance observed in the results obtained by the two methods was statistically not significant (P>0.05). The conventional technique is labor intensive, cumbersome and time-consuming. The assay described here, on the other hand, is simple, easy and rapid enough to allow testing of a large number of bacterial isolates or recombinant clones in a single day. Thus, the assay can serve as an excellent alternative to the conventional technique for determining the bacterial serum susceptibility.     

Distribution of N-cadherin in human cerebral cortex during prenatal development

An important subgroup of adhesion molecules is the superfamily of cadherins, which takes part in cell recognition and differentiation during development. To our knowledge only one study describing N-cadherin expression in developing human brain has been performed so far. Our aim is to identify N-cadherin expression to establish a relationship between its expression and function in human cerebral cortex during prenatal development. In the present study, localization and intensity of N-cadherin was investigated in developing cerebral cortex. Fetuses from spontaneous abortions (n=13) were obtained from first, second, and third trimesters. Western blot analysis revealed three bands and the third trimester samples showed the strongest bands for N-cadherin. Cell processes, axon bundles, and some of the developing neurons revealed immunoreactivity for N-cadherin throughout pregnancy. The immunoreactivity increased in the developing neocortex and expanded from the ventricular layer toward the marginal zone as development progressed. Moreover, the immunoreactivity was strong in vascular endothelium during all three trimesters. We conclude that N-cadherin is dynamically related to the organization of cerebral cortex layers during prenatal development. The dynamic expression pattern implicates N-cadherin as a potential regulator of cell migration, axon extension and fasciculation, the establishment of synaptic contacts, and neurovascular angiogenesis in the developing human cerebral cortex.     

Blood pressure regulates the activity and function of the Na-K-2Cl cotransporter in vascular smooth muscle

The Na-K-2Cl cotransporter (NKCC1) is one of several transporters that have been linked to hypertension, and its inhibition reduces vascular smooth muscle tone and blood pressure. NKCC1 in the rat aorta is stimulated by vasoconstrictors and inhibited by nitrovasodilators, and this is linked to the contractile state of the smooth muscle. To determine whether blood pressure also regulates NKCC1, we examined the acute effect of hypertension on NKCC1 in rats after aortic coarctation. In the hypertensive aorta (28-mmHg rise in mean blood pressure), an increase in NKCC1 activity (measured as bumetanide-sensitive (86)Rb efflux) was apparent by 16 h and reached a plateau of 62% greater than control at 48 h. In contrast, there was a slight decrease in NKCC1 activity in the hypotensive aorta (21% decrease in mean blood pressure). Measurement of NKCC1 mRNA by real-time PCR revealed a fivefold increase in the hypertensive aorta compared with the hypotensive aorta or sham aorta. The inhibition by bumetanide of isometric force response to phenylephrine was significantly greater in the hypertensive aorta than in the control aorta or hypotensive aorta. We conclude that NKCC1 in rat aortic smooth muscle is regulated by blood pressure, most likely through changes in transporter abundance. This upregulation of NKCC1 is associated with a greater contribution to force generation in the hypertensive aorta. This is the first demonstration that NKCC1 in vascular smooth muscle is regulated by blood pressure and indicates that this transporter is important in the acute response of vascular smooth muscle to hypertension.     

Trace element concentrations and superoxide dismutase and catalase activities in benign and malignant larynx tumors

The plasma and erythrocyte levels of zinc, copper, and magnesium and the activities of red-cell copper-zinc superoxide dismutase (Cu/Zn-SOD) and catalase (CAT) were determined in patients with benign and malignant tumors of the larynx. Blood samples from patients and healthy controls were drawn using heparinized tubes. The erythrocyte Cu/Zn-SOD and CAT activities were determined spectrophotometrically and the zinc, copper, and magnesium concentrations were determined in erythrocyte and plasma by atomic absorption spectrometry. Variance analysis was employed in the statistical evaluation of the findings. There was a significant increase in red-cell Cu/Zn-SOD activity in the subjects with malignant and benign tumors compared to controls (p<0.001). The CAT activity increased only in the benign tumor group (p<0.01). The plasma zinc concentrations were significantly lower in the malignant tumor group (p<0.05) and significantly higher in the benign tumor group (p<0.01). The erythrocyte copper concentrations were significantly lower in both benign and malignant tumor groups (p<0.001). The plasma copper and magnesium and the erythrocyte magnesium concentrations did not show significant differences relative to controls (p>0.05). The increases in the activities of SOD and CAT activities and the changes in trace elements concentrations can indicate the presence of increased reactive oxygen species that might play a part in the pathogenesis larynx tumors. Presented at the IX Asian-Pacific Congress of Clinical Biochemistry, March 9–14, 2002, New Delhi, India.