On the adsorption kinetics and mechanism of enhanced photocatalytic activity of Fe3 O4 -SiO2 -TiO2 core-multishell nanoparticles against E. coli.

In the present study, a Fe3 O4 -TiO2 (FT) core-shell and a core-multishell structure of Fe3 O4 -SiO2 -TiO2 (FST) were synthesized, and their bactericidal capability was investigated on Escherichia coli (E. coli). Scanning electron microscopy (SEM), ultraviolet-visible spectroscopy (UV-vis), X-ray diffraction, Brunauer-Emmett-Teller, zeta potential, and fluorimetry were carried out to characterize properties of synthesized nanoparticles. An efficiency of 98% adsorption and harsh bacterial damage was observed when E. coli was put in contact with FST. Weaker adsorption of bacteria in contact with FT demonstrated that heterojunction has destructive effects on nanostructure. Further investigation proved that more OH were produced on the surface of FST, which is a sign of its longer lifetime. Moreover, results revealed that the presence of SiO2 in the structure caused enhanced coverage, surface area, and porosity in TiO2 outer layer, all of which have positive effects on adsorption. However, UV-vis showed smaller band gap for FT. It suggests that although photoactivity of FST is less influenced by light absorption, it possesses more e/h lifetime for generation of reactive oxygen species. Results point to the importance of SiO2 as an obstacle of heterojunction on both adsorption and photoactivity. It was also proposed that increasing band gap in FST can be attributed to the porosity of SiO2 that causes suppression of TiO2 nanocrystallite growth.

Effects of Oral Dosage of Lead Acetate II on Osteocalcin Gene Expression in Rat Mesenchymal Stem Cells.

BACKGROUND: Lead (Pb) is a heavy metal that has devastating effects on many animal tissues. In this study we investigated the effects of orally-dosed lead acetate II on osteocalcin gene (osteocalcin) expression in mesenchymal stem cells grown in an osteogenic medium. Osteocalcin is an abundant bone matrix differentiation protein. METHODS: Twelve male Wistar rats were divided into three groups of four rats each. Two groups were fed orally with 50 or 100 ppm of lead acetate II with libitum feed and water for two months. The control group was fed with libitum feed and water only. Rats were euthanized and femoral bone marrow mesenchymal stem cells (BM-MSCs) were extracted. The cells were cultured in osteogenic medium and osteocalcin expression was determined by real-time PCR. RESULTS: Real-time PCR showed that osteocalcin expression was significantly less in the BM-MSCs of rats that received 100 ppm of lead acetate II than in the BM-MSCs of the other groups (P<0.05), and that osteocalcin expression was less in the BM-MSCs of the group that received 50 ppm of lead acetate II than in the control group. CONCLUSION: Doses of 50 and 100 ppm of lead acetate II in rats caused a significant decrease in osteocalcin expression in BM-MSCs grown in osteogenic medium.

Pathodiagnostic parameters and evaluation of O6- methyl guanine methyl transferase gene promoter methylation in meningiomas.

Histopathological evaluation and grading of meningioma give important prognostic information. We evaluated retrospectively monotonous sheeting, necrosis, hypercellularity, nuclear pleomorphism, small cell changes, brain invasion, mitosis, mast cells, psammoma bodies, MIB-1 labeling index (MIB-1 LI) and histological grade of 230 primary meningioma tumors according to the latest World Health Organization (WHO) classification. To reveal any possible association between clinical features and promoter hypermethylation of O(6)-methylguanine-DNA methyltransferase (MGMT) as an important epigenetic modification in many human cancers, we also evaluated the methylation status of MGMT in meningiomas by a SYBR-green-based real-time PCR method. There was a female predominance (2.38 to 1) in the meningiomas. The mean age of the patients was 49.9 ± 12.6 years (range 16 to 78 years). Transitional meningiomas were the most common subtype of the meningiomas (35.21%, n=81). Most of the meningiomas were located in the falx and parasagital area. There was a significant correlation between histopathological features of malignancy. These features were observed more frequently and with statistical relation to grade II rather than grade I. Mast cells, psammoma bodies and nuclear pleomorphism had poor associations (P>0.05). When we re-evaluated the tumor grading, 31 patients with grade I meningiomas were upgraded to grade II. None of the meningiomas tested by MSQP were methylated in MGMT promoter sequence. High MIB-1 LI could be indicative for higher grade of meningioma. Continuous revision of the classification system is needed to improve the accuracy of prognostic judgments in meningioma. The data confirm that there is no rationale to test meningiomas for MGMT methylation status.

The effect of temperature on antibacterial activity of biosynthesized silver nanoparticles.

The purpose of this study was the evaluation of two different temperatures on antibacterial activity of the biosynthesized silver nanoparticles. 38 silver nanoparticles-producing bacteria were isolated from soil and identified. Biosynthesis of silver nanoparticles by these bacteria was verified through visible light spectrophotometry. Two strains were relatively active for production of silver nanoparticles. These strains were subjected for molecular identification and recognized as Bacillus sp. and Acinetobacter schindleri. In the present study, the effect of temperatures was evaluated on structure and antimicrobial properties of the silver nanoparrticles by transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis and antimicrobial Agar well diffusion methods. The silver nanoparticles showed antibacterial activity against all the pathogenic bacteria; however, this property was lost after treatment of the silver nanoparticles by high temperatures (100 and 300 °C). TEM images showed that the average sizes of heated silver nanoparticles were >100 nm. However, these were <100 nm for non-heated silver nanoparticles. Although, XRD patterns showed the crystalline structure of heated silver nanoparticles, their antibacterial activities were less. This was possible because of the sizes and accordingly less penetration of the particles into the bacterial cells. In addition, elimination of the capping agents by heat might be considered another reason.

Immunohistochemical assessment of MGMT expression and p53 mutation in glioblastoma multiforme.

AIMS AND BACKGROUND: The prognosis of glioblastoma multiforme (GBM) remains poor despite advances in surgery and adjuvant therapies. TP53 and O6-methylguanine-DNA methyltransferase (MGM) are tumor suppressor genes that are implicated in GBM resistance to radiation and chemotherapy. In order to assess the expression of the protein products of these two genes, 50 GBM samples were analyzed in this study. METHODS: Demographic and clinical data along with postsurgery tumor samples from 50 GBM patients were collected from the pathology archive. MGMT and p53 protein expression was evaluated by immunohistochemistry. RESULTS: 52% of cases had mutated p53, predominantly expressed in the nuclei of tumor cells. MGMT immunohistochemistry was negative in 35 (70%) patients and positive in 15 (30%) others. Immunohistochemistry-negative specimens for MGMT expression showed a significantly higher expression of mutant p53 (P = 0.03). CONCLUSION: MGMT expression was significantly lower in cells bearing p53 mutation. This indicates that there is a tendency for p53 activity to decline with MGMT inactivation. However, this study could not deduce which protein was the regulator of the other.

Association between MGMT promoter hypermethylation and p53 mutation in glioblastoma.

O(6)-methylguanine-DNA methyltransferase (MGMT) is a DNA repair enzyme that removes alkyl groups from the O(6) position of guanine. MGMT is transcriptionally silenced by promoter hypermethylation in several human neoplasia. We used methylation-specific PCR (MSP) to analyze the MGMT promoter methylation status of 50 glioblastoma tumors. Hypermethylation was detected in 24 of 50 (48%) samples. We also analyzed mutant p53 expression by immunohistochemical analysis of glioblastoma tissue samples. A significant association was found between MGMT methylation and p53 mutation status (p< .05). These results suggested that epigenetic inactivation of MGMT plays an important role in the survival of glioblastoma patients and this inactivated gene involved in p53 mutation.

Aberrant p16 methylation, a possible epigenetic risk factor in familial esophageal squamous cell carcinoma.

AIM: Detection of methylation in the p16 gene, an inhibitor of cyclin D-dependent protein kinase, as a new tumor marker for early detection of esophageal squamous cell carcinoma (ESCC) in DNA derived from blood and serum. METHOD: A large family with clustering of ESCC was assessed in Khorasan province in northeastern Iran. The family had three histologically proven cases of ESCC in two consecutive generations and several other deceased cases with histories of ESCC. DNA from blood of 28 living family members in three consecutive generations, 30 sporadic ESCC cases (from serum, blood, and tumor tissues), and 30 healthy volunteers (from blood) were examined for the methylation status of p16 promoter using methylation-specific PCR (MSP). RESULTS: Aberrant p16 promoter methylation was found in 64.3% (n = 28) of ESCC family members and none (n = 30) of our normal volunteers. Five of the 28 family members with esophageal cancer symptoms had negative endoscopy results for ESCC, while four of these members had p16 hypermethylation in their blood. The family members with negative endoscopy and positive p16 promoter methylation are being monitored closely for signs of ESCC development through regular check-ups and chromoendoscopies. In sporadic ESCC in northeastern Iran, 73.3% (n = 30) of tumor tissue samples had p16 hypermethylation. Serum and blood samples from the same patients showed p16 hypermethylation in 26.6% and 43.3% of the samples, respectively. CONCLUSION: Aberrant p16 methylation may be a valuable diagnostic tool as a tumor marker for the early identification of individuals in high risk ESCC families.