AFM feature definition for neural cells on nanofibrillar tissue scaffolds.

A diagnostic approach is developed and implemented that provides clear feature definition in atomic force microscopy (AFM) images of neural cells on nanofibrillar tissue scaffolds. Because the cellular edges and processes are on the same order as the background nanofibers, this imaging situation presents a feature definition problem. The diagnostic approach is based on analysis of discrete Fourier transforms of standard AFM section measurements. The diagnostic conclusion that the combination of dynamic range enhancement with low-frequency component suppression enhances feature definition is shown to be correct and to lead to clear-featured images that could change previously held assumptions about the cell-cell interactions present. Clear feature definition of cells on scaffolds extends the usefulness of AFM imaging for use in regenerative medicine.

Rapid DNA double-strand breaks resulting from processing of Cr-DNA cross-links by both MutS dimers.

Mismatch repair (MMR) strongly enhances cyto- and genotoxicity of several chemotherapeutic agents and environmental carcinogens. DNA double-strand breaks (DSB) formed after two replication cycles play a major role in MMR-dependent cell death by DNA alkylating drugs. Here, we examined DNA damage detection and the mechanisms of the unusually rapid induction of DSB by MMR proteins in response to carcinogenic chromium(VI). We found that MSH2-MSH6 (MutSalpha) dimer effectively bound DNA probes containing ascorbate-Cr-DNA and cysteine-Cr-DNA cross-links. Binary Cr-DNA adducts, the most abundant form of Cr-DNA damage, were poor substrates for MSH2-MSH6, and their toxicity in cells was weak and MMR independent. Although not involved in the initial recognition of Cr-DNA damage, MSH2-MSH3 (MutSbeta) complex was essential for the induction of DSB, micronuclei, and apoptosis in human cells by chromate. In situ fractionation of Cr-treated cells revealed MSH6 and MSH3 chromatin foci that originated in late S phase and did not require replication of damaged DNA. Formation of MSH3 foci was MSH6 and MLH1 dependent, whereas MSH6 foci were unaffected by MSH3 status. DSB production was associated with progression of cells from S into G(2) phase and was completely blocked by the DNA synthesis inhibitor aphidicolin. Interestingly, chromosome 3 transfer into MSH3-null HCT116 cells activated an alternative, MSH3-like activity that restored dinucleotide repeat stability and sensitivity to chromate. Thus, sequential recruitment and unprecedented cooperation of MutSalpha and MutSbeta branches of MMR in processing of Cr-DNA cross-links is the main cause of DSB and chromosomal breakage at low and moderate Cr(VI) doses.

Unusual case of skull metastasis secondary to pancreatic adenocarcinoma.

Skull metastasis must be kept in mind when considering the differential diagnosis of a skull tumor. Skull metastases cause local swelling that is usually painless, and rarely they lead to neurologic dysfunction. Despite the fact that hematogenous skull metastases can be caused by nearly all types of tumors (lung, prostate, thyroid carcinoma, malignant melanoma), breast cancer is associated with the highest rate of metastatic skull lesions. We report an extremely rare case of skull metastasis from a pancreatic adenocarcinoma, in a 65-year-old woman, presented with painless frontoparietal scalp swelling which developed within three months. To the best of our knowledge, this is the second case involving the skull secondary to a pancreatic adenocarcinoma, and the first case when skull metastasis was the first evidence of a pancreatic adenocarcinoma.

Multi-organ cavernous hemangiomas: case report.

Hemangiomas are rare benign tumors of vascular origin and multiple location of these tumors in different organs is extremely unusual. We report a case with multiple hemangiomas, characterized by calvarial, hepatic and suspicious costal involvement. Organ involvement and multiplicity of the neoplasm made our case very interesting and distinct. Our search of the English literature has revealed that no similar case has ever been published.

Fiber optic sensors using novel substrates for hydrogen sulfide determination by solid surface fluorescence.

Two different fiber optic sensors were developed for the determination of hydrogen sulfide at ppb concentration levels; a probe-type fiber optic sensor coated with polyethylene oxide containing 0.5 M CdCl(2) and a fiber optic sensor utilizing 0.5 M CdCl(2)-pretreated filter paper as solid substrate. In the first type, CdCl(2)-polyethyleneoxide (PEO) mixture was coated onto the tip of a fiber optic probe and the probe was exposed to H(2)S. The methodology is based on the measurement of CdS fluorescence on the surface. Detection limit (3s) of the PEO-coated fiber optic system was 36.0 ppb for H(2)S and precision at the 0.552 ppm level was 29% R.S.D. For the fiber optic system utilizing CdCl(2)-pretreated filter paper, two different configurations were devised and evaluated; a bifurcated fiber optic sensor and a single fiber optic sensor. Similar figures were obtained with these two systems; the detection limit (3s) was 4.0 ppb for the bifurcated fiber optic sensor and 4.3 ppb for the single fiber optic sensor, and both sensors had linear responses in the range 0.032-1.0 ppm. Their precisions at 0.299 ppm level were also very similar, 10 and 11% R.S.D., respectively, for the bifurcated and single fiber systems. In addition to the fiber optic sensors developed, various surfactants (sodiumdodecylsulfate (SDS), Aerosol OT, Aerosol A102, Aerosol 501), some cellulosic substances (sodium carboxymethylcellulose (CMC), ethylcellulose, hydroxypropylmethylcellulose, ethylhydroxyethylcellulose, alpha-cellulose) and several water-soluble polymers (polyacrylicacid polyethleneoxide (PEO), polyvinylalcohol (PVA)) were dissolved in proper solvents and after mixing with 0.5 M CdCl(2), were spread over glass slides. These novel solid substrates were exposed to H(2)S and fluorescence signal on the surfaces of the glass slides was measured with a luminescence spectrometer. The new substrates were shown to be good alternatives to filter paper for the determination of H(2)S by room temperature solid surface fluorescence spectrometry.

Sample Preparation for Arsenic, Copper, Iron, and Lead Determination in Sugar.

Two sample preparation methods were modified and optimized for the determination of As, Cu, Fe, and Pb in white sugar using atomic absorption spectrometry (AAS). Analyses were carried out using hydride generation AAS (HG-AAS) for As and flame AAS (FAAS) for Cu, Fe, and Pb. White sugar samples were prepared by dry ashing of the samples with H(2)SO(4) and Mg(NO(3))(2). Recoveries for As, Cu, Fe, and Pb were 87.6, 92.8, 95.8, 91.1% respectively,in ashing with H(2)SO(4). They were 95.1, 92.4, 97.4, and 91.1%, respectively, in ashing with Mg(NO(3))(2).6H(2)O. When small quantities of spikes were used, 94.7 and 95.3% recoveries of arsenic were found for the procedures applying H(2)SO(4) and Mg(NO(3))(2), respectively.

A novel sorbent tube for ambient hydrogen sulfide determination.

A novel tubular device has been developed for hydrogen sulfide determination in air. Several substrates such as commercial silica gel and alumina TLC plates, silica gel powder, alumina, CaSO(4), CaCO(3), BaSO(4), MgO, chalk, alpha-cellulose and ethyl cellulose were tested as solid substrates. 30-70-mesh silica gel was finally employed in glass tubes of 4.0 mm internal diameter. Silica gel is treated with 0.5 M aqueous CdCl(2) solution, dried, filled into the glass tube and sample gas is passed through the device using nitrogen as the carrier gas where 70% relative humidity is employed. The analyte reacts with the solid substrate to form a luminescent spot whose length in the tube is measured and correlated to concentration. The flow rate was 68 ml min(-1). The analytical system is linear in the range of 0.2-1.3 ppm H(2)S for the specified conditions. The prepared devices are stable at least for 3 months prior to sampling; and after sampling, the luminescing spot is stable also at least for 3 months.

Hydrogen sulfide determination by solid surface luminescence.

In the analytical system suggested, atmospheric hydrogen sulfide reacts with the surface of a filter paper treated with aqueous cadmium chloride and yields a luminescent species whose intensity can be correlated with the analyte concentration in ambient air. It was shown that the luminescent species are CdS solid particles which were formed in a well defined size. The paper luminescence was also tried on polymeric surfaces; polyethyleneoxide, polyvinyl alcohol, ethylcellulose and carboxymethylcellulose were found to give a similar luminescence signal. The system can be used on the tip of an optical fiber for an irreversible, cumulative type of analytical device for hydrogen sulfide determination. The 3s detection limit for the paper luminescence detection system was 7.8 ppb H(2)S.

Determination of germanium by AAS in chloride-containing matrices.

Interference effects of NaCl on the ET-AAS determination of Ge have been studied. The use of several matrix modifiers to alleviate this problem such as Ni and Zn perchlorates and nitrates, nitric acid, ammonium nitrate are reported. The stabilizing effect of Zn and Ni perchlorates allows the use of high pretreatment temperatures. NaCl is thus thermally volatilized from the atomizer by employing pretreatment temperatures higher than 1500 degrees C resulting in an improved sensitivity. Germanium levels in zinc plant slag samples, have been determined and compared to those obtained for the same samples spiked with NaCl with platform and wall atomization using nickel perchlorate as a matrix modifier. The results were compared with those from a hydride generation system equipped with a liquid nitrogen trap. The recoveries for germanium have been almost complete and amount to 99% for the original slag samples and 80% for 15% (w/w) NaCl containing spiked samples.