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At least 685 records · Page 38Linked to original sources
PubMed2000

The impact of buffers and surfactants from micellar electrokinetic chromatography on matrix-assisted laser desorption ionization (MALDI) mass spectrometry of peptides. Effect of buffer type and concentration on mass determination by MALDI-time-of-flight mass spectrometry.

This paper describes the effect of various buffers, surfactants, and organic additives commonly encountered in capillary zone electrophoresis and micellar electrokinetic chromatography on the molecular weight determination of peptides by matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry. Signal-to-noise ratio generally decreased with increasing buffer concentration without affecting mass accuracy, but the type of buffer was also important. Good spectra were obtained with an ammonium acetate buffer up to a concentration of 500 mM without impacting ionization of either peptides or other mobile phase constituents. Ionization of organic additives, such as anionic surfactants, non-ionic surfactants, and cyclodextrins was buffer dependent and presented a problem when the mass of the additive was in the range of the peptide mass. Brij-35, Tween-80, and cyclodextrins all produced prominent spectra of their own in the presence of sodium or potassium containing buffers, but not with ammonium acetate. Cationization of these neutral species with sodium or potassium ions allowed them to acquire a positive charge and produce spectra. In contrast, the ammonium ion appears to be a poor cationizating agent. Ionization of neutral surfactants was suppressed in ammonium acetate without impacting the spectra of peptides. Ammonium acetate buffers containing 30 mM sodium dodecyl phosphate also gave spectra with good signal intensity and no interference from the surfactant. Suppression of peptide ionization in MALDI was a problem when methanol, tetrabutyl amine, or poly(vinyl alcohol) were used with either ammonium acetate, sodium phosphate, and N-(2-hydroxyethyl)piperazine-N-(2-ethansulfonic acid).

Buffers↗
PubMed1988

Free radical production by high energy shock waves--comparison with ionizing irradiation.

Fricke chemical dosimetry is used as an indirect measure of the free radical production of ionizing irradiation. We adapted the Fricke ferrous sulfate radiation dosimeter to examine the chemical effects of high energy shock waves. Significant free radical production was documented. The reaction was dose dependent, predictably increased by acoustic impedance, but curvilinear. A thousand shocks at 18 kilovolts induced the same free radical oxidation as 1100 rad cobalt-60 gamma ionizing irradiation, increasing to 2900 rad in the presence of an air-fluid zone of acoustic impedance. The biological effect of these free radicals was compared to that of cobalt-60 ionizing irradiation by measuring the affect on Chinese hamster cells by clonogenic assay. While cobalt-60 irradiation produced a marked decrease in clonogenic survivors, little effect was noted with high energy shock waves. This suggested that the chemical effects produced by shock waves were either absent or attenuated in the cells, or were inherently less toxic than those of ionizing irradiation.

Animals↗
PubMed2000

Magnetic resonance imaging (MRI) controlled outcome of side effects caused by ionizing radiation, treated with 780 nm-diode laser -- preliminary results.

BACKGROUND AND OBJECTIVE: Ionizing radiation therapy by way of various beams such as electron, photon and neutron is an established method in tumor treatment. The side effects caused by this treatment such as ulcer, painful mastitis and delay of wound healing are well known, too. Biomodulation by low level laser therapy (LLLT) has become popular as a therapeutic modality for the acceleration of wound healing and the treatment of inflammation. Evidence for this kind of application, however, is not fully understood yet. This study intends to demonstrate the response of biomodulative laser treatment on the side effects caused by ionizing radiation by means of magnetic resonance imaging (MRI). STUDY DESIGN/PATIENTS AND METHODS: Six female patients suffering from painful mastitis after breast ionizing irradiation and one man suffering from radiogenic ulcer were treated with lambda=780 nm diode laser irradiation at a fluence rate of 5 J/cm2. LLLT was performed for a period of 4-6 weeks (mean sessions: 25 per patient, range 19-35). The tissue response was determined by means of MRI after laser treatment in comparison to MRI prior to the beginning of the LLLT. RESULTS: All patients showed complete clinical remission. The time-dependent contrast enhancement curve obtained by the evaluation of MR images demonstrated a significant decrease of enhancement features typical for inflammation in the affected area. CONCLUSION: Biomodulation by LLLT seems to be a promising treatment modality for side effects induced by ionizing radiation.

Adult↗
PubMed1979

Studies on the effects of ionization on bacterial aerosols in a burns and plastic surgery unit.

The effect of the ionization of the air on the decay of bacterial aerosols was studied in a Burns and Plastic Surgery Unit. Ions were generated by free corona needles. The air content of bacteria measured by settle plates was found to be smaller during the ionization period than during the controls period. The number of individual phage typed Staph. aureus strains was especially found to be lower during ionization. The opposite potential increased the disappearance of bacteria from the air. The size of skin particles carrying bacteria is not optimum, but the results obtained show that the ionization may have applications in controlling airborne infection.

Air Ionization↗
PubMed1995

Matrix-assisted laser desorption ionization of neutral clusters composed of matrix and analyte molecules.

A new version of the matrix-assisted laser desorption ionization experiment is described. Composed clusters created by laser desorption of a mixture of analyte and matrix material were injected into a supersonic jet and then analyzed by multiphoton ionization time-of-flight mass spectrometry. Selective two-photon ionization of matrix molecules of a cluster component caused their dissociation, followed by intercluster proton or cation transfer to an analyte that is transparent for the wavelength of ionizing radiation. The intercluster charge transfer reactions are the only pathway for analyte ion formation under these conditions, as can be concluded from analysis of the mass spectra of a variety of substances.

Amino Acid Sequence↗
PubMed2003

Electrospray ionization of protein mixtures at low pH.

Solutions composed of single proteins and mixtures of proteins are subjected to electrospray ionization to study the influence of protein components on the responses of one another. Protein matrix effects in electrospray ionization are particularly relevant to the development of top-down protein identification methodologies involving protein mixtures, whereby whole protein ions are subjected to tandem mass spectrometry. Emphasis is placed largely on solutions composed of equal parts methanol and water and 1% acetic acid. The results, therefore, are relevant to low-pH solutions with significant organic content, a commonly used set of conditions in electrospray ionization mass spectrometry that tends to denature proteins. Under these conditions, very similar response curves are measured for a variety of proteins after charge normalization. That is, when the data are plotted in terms of the concentration of charge sites, rather than in terms of the concentration of protein molecules, the slopes of the response curves as well as the point at which response becomes less than linear with concentration are similar. Charge normalization is made on the basis of the weighted average charge of a protein, as reflected in the electrospray ionization mass spectrum. When proteins can be regarded as a collection of equivalent charge sites, the signal response from one protein can be used to predict the responses for other proteins. Furthermore, it is also possible to predict the dependence of the signal response for a particular protein in a mixture on the concentration of other proteins in the mixture. Examining signal response on a weighted average charge basis appears to be an effective means for identifying situations in which the protein does not behave as a collection of equivalent charge sites.

Cytochrome c Group↗
PubMed1999

The tyrosine kinase lck is required for CD95-independent caspase-8 activation and apoptosis in response to ionizing radiation.

Induction of apoptosis is a hallmark of cytostatic drug and radiation-induced cell death in human lymphocytes and lymphoma cells. However, the mechanisms leading to apoptosis are not well understood. We provide evidence that ionizing radiation induces a rapid activation of caspase-8 (FLICE) followed by apoptosis independently of CD95 ligand/receptor interaction. The radiation induced cleavage pattern of procaspase-8 into mature caspase-8 resembled that following CD95 crosslinking and resulted in cleavage of the proapoptotic substrate BID. Overexpression of dominant-negative caspase-8 interfered with radiation-induced apoptosis. Caspase-8 activation by ionizing radiation was not observed in cells genetically defective for the Src-like tyrosine kinase Lck. Cells lacking Lck also displayed a marked resistance towards apoptosis induction upon ionizing radiation. After retransfection of Lck, caspase-8 activation and the capability to undergo apoptosis in response to ionizing radiation was restored. We conclude that radiation activates caspase-8 via an Lck-controlled pathway independently of CD95 ligand expression. This is a novel signaling event required for radiation induced apoptosis in T lymphoma cells.

Antibodies↗
PubMed2002

Ionizing radiation activates Erb-B receptor dependent Akt and p70 S6 kinase signaling in carcinoma cells.

In this study we have investigated the effects of low dose ionizing radiation (2 Gy) on p70 S6 kinase and Akt signaling with respect to Erb-B receptors in both the A431 squamous and the MDA-MB-231 mammary carcinoma cell lines. Ionizing radiation caused a 2-3-fold increase in p70 S6 kinase activity that was blocked pharmacologically using an EGFR inhibitor (AG1478) alone, or in combination with an Erb-B2 inhibitor (AG825). These results suggested that both EGFR and Erb-B2 receptors could initiate radiation-induced activation of p70 S6K. EGFR dependent Erb-B3 signaling also contributed to p70 S6 kinase activity through recruitment and activation of PI3K, which has been shown to regulate p70 S6 kinase activity. Furthermore, inhibition of the EGFR blocked IR stimulated increases in protein translation, a biologic consequence of p70 S6 kinase activation. We also report that ionizing radiation stimulated Akt activity that was partially independent of PI3K activity, but dependent on Erb-B2 function. Erb-B2 inhibition also correlated with enhanced apoptosis following IR exposure, suggesting an important role for Erb-B2 in cell survival. Together this work demonstrates that the Erb-B receptor tyrosine kinase network stimulates cytoprotective p70 S6 kinase and Akt activity in response to clinically relevant doses of ionizing radiation.

Apoptosis↗
PubMed2005

Rapid in situ detection of alkaloids in plant tissue under ambient conditions using desorption electrospray ionization.

Desorption electrospray ionization (DESI) mass spectrometry is applied to the in situ detection of alkaloids in the tissue of poison hemlock (Conium maculatum), jimsonweed (Datura stramonium) and deadly nightshade (Atropa belladonna). The experiment is carried out by electrospraying micro-droplets of solvent onto native or freshly-cut plant tissue surfaces. No sample preparation is required and the mass spectra are recorded under ambient conditions, in times of a few seconds. The impact of the sprayed droplets on the surface produces gaseous ions from organic compounds originally present in the plant tissue. The effects of operating parameters, including the electrospray high voltage, heated capillary temperature, the solvent infusion rate and the carrier gas pressure on analytical performance are evaluated and optimized. Different types of plant material are analyzed including seeds, stems, leaves, roots and flowers. All the previously reported alkaloids have been detected in C. maculatum, while fifteen out of nineteen known alkaloids for D. stramonium and the principal alkaloids of A. belladonna were also identified. All identifications were confirmed by tandem mass spectrometry. Results obtained show similar mass spectra, number of alkaloids, and signal intensities to those obtained when extraction and separation processes are performed prior to mass spectrometric analysis. Evidence is provided that DESI ionization occurs by both a gas-phase ionization process and by a droplet pick-up mechanism. Quantitative precision of DESI is compared with conventional electrospray ionization mass spectrometry (after sample workup) and the RSD values for the same set of 25 dicotyledonous C. maculatum seeds (one half of each seed analyzed by ESI and the other by DESI) are 9.8% and 5.2%, respectively.

Alkaloids↗
PubMed2003

Poly(ADP-ribose) polymerase-1 is a positive regulator of the p53-mediated G1 arrest response following ionizing radiation.

Poly(ADP-ribose) polymerase-1 (PARP-1) and the p53 tumor suppressor protein are both involved in the cellular response to genotoxic stress. Upon binding to the site of DNA strand breakage, PARP-1 is activated, leading to rapid and transient poly(ADP-ribosyl)ation of nuclear proteins using NAD+ as substrate. To investigate the role of PARP-1 in the p53 response to ionizing radiation in human cells, PARP-1 function was disrupted in wild-type p53 expressing MCF-7 and BJ/TERT cells using two strategies: chemical inhibition with 1,5-dihydroxyisoquinoline, and trans-dominant inhibition by overexpression of the PARP-1 DNA-binding domain. Although a number of proteins can catalyze poly(ADP-ribosyl)ation in addition to PARP-1, we show that PARP-1 is the only detectable active species in BJ/TERT and MCF-7 cells. 1,5-Dihydroxyisoquinoline treatment prior to ionizing radiation delayed and attenuated the induction of two p53-responsive genes, p21 and mdm-2, and led to suppression of the p53-mediated G1-arrest response in MCF-7 and BJ/TERT cells. Trans-dominant inhibition of PARP-1 by overexpression of the PARP-1 DNA-binding domain in MCF-7 cells also led to a delay and attenuation in p21 induction and suppression of the p53-mediated G1 arrest response to ionizing radiation. Hence, inhibition of endogenous PARP-1 function suppresses the transactivation function of p53 in response to ionizing radiation. This study establishes PARP-1 as a critical regulator of the p53 response to DNA damage.

Binding Sites↗
PubMed2006

Activation of Bak and Bax through c-abl-protein kinase Cdelta-p38 MAPK signaling in response to ionizing radiation in human non-small cell lung cancer cells.

Intracellular signaling molecules and apoptotic factors seem to play an important role in determining the radiation response of tumor cells. However, the basis for the link between signaling pathway and apoptotic cell death machinery after ionizing irradiation remains still largely unclear. In this study, we showed that c-Abl-PKCdelta-Rac1-p38 MAPK signaling is required for the conformational changes of Bak and Bax during ionizing radiation-induced apoptotic cell death in human non-small cell lung cancer cells. Ionizing radiation induced conformational changes and subsequent oligomerizations of Bak and Bax, dissipation of mitochondrial membrane potential, and cytochrome c release from mitochondria. Small interference (siRNA) targeting of Bak and Bax effectively protected cells from radiation-induced mitochondrial membrane potential loss and apoptotic cell death. p38 MAPK was found to be selectively activated in response to radiation treatment. Inhibition of p38 MAPK completely suppressed radiation-induced Bak and Bax activations, dissipation of mitochondrial membrane potential, and cell death. Moreover, expression of a dominant negative form of protein kinase Cdelta (PKCdelta) or siRNA targeting of PKCdelta attenuated p38 MAPK activation and conformational changes of Bak and Bax. In addition, ectopic expression of RacN17, a dominant negative form of Rac1, markedly inhibited p38 MAPK activation but did not affect PKCdelta activation. Upon stimulation of cells with radiation, PKCdelta was phosphorylated dramatically on tyrosine. c-Abl-PKCdelta complex formation was also increased in response to radiation. Moreover, siRNA targeting of c-Abl attenuated radiation-induced PKCdelta and p38 MAPK activations, and Bak and Bax modulations. These data support a notion that activation of the c-Abl-PKCdelta-Rac1-p38 MAPK pathway in response to ionizing radiation signals conformational changes of Bak and Bax, resulting in mitochondrial activation-mediated apoptotic cell death in human non-small cell lung cancer cells.

Apoptosis↗
PubMed2004

Protective effects of melatonin on the ionizing radiation induced DNA damage in the rat brain.

Melatonin is an endogenously produced antioxidant with radioprotective actions while ionizing radiation is a well-known cytotoxic and mutagenic agent of which the biological results are attributable to its free radical producing effects. The effect of melatonin on the DNA strand breakage and lipid peroxidation induced by ionizing radiation in the rat brain were investigated in order to clarify its radioprotective ability. The DNA strand breakage in rat brain exposed to 1000 cGy ionizing radiation was assessed by alkaline single cell gel electrophoresis and the lipid peroxidation was evaluated by measuring thiobarbituric acid reactive substances (TBARS) concentrations. A significant increase in DNA damage (p < 0.05) and TBARS concentrations (p < 0.01) was found in the radiation treated rat brain. Pre-treatment of rats with intraperitoneal doses of 100 mg/kg melatonin provided a significant decrease in the DNA strand breakage and lipid peroxidation. Our results indicate that melatonin can protect brain cells from oxidative damage induced by ionizing radiation.

Animals↗
PubMed2006

Computational evaluation of changes in ionizing radiation dose distribution in tissues caused by EM applicators when external radiation and hyperthermia act simultaneously.

PURPOSE: The presented theoretical study investigates the influence of CFMA-like electromagnetic microstrip applicators (MAs) on ionizing radiation intensity and depth radiation dose distribution (DRDD) in irradiated tissues which are tightly covered with a MA. METHODS: It is shown that at relatively low photon energy (<200 keV) the MA does not affect noticeable the profile of the DRDD curve and does not lead to skin overdosing. Nevertheless, it significantly (up to 20-35%) decreases the low energy ionizing radiation intensity. For high energy photons (>1 MeV), on the contrary, the decrease of radiation intensity, caused by the MA, is small (3-10%), but the profile of the DRDD curve, calculated by means of the Monte-Carlo method, is significantly affected. RESULTS: The radiation dose maximum is shifted to the skin, resulting in possible skin overdosing. Radiation absorption characteristics of MA are calculated and compared with published parameters of EM horn and US applicators now in use for external simultaneous radiation and hyperthermia (ESRH) procedures. The MA provides the minor ionizing radiation absorption. Due to it and owing to their conformability with the tissue surface the MAs would not require any additional means or devices to be used for ESRH treatment procedures with any common ionizing radiation equipment. CONCLUSIONS: The necessity of development means for decreasing the time of radiation equipment occupation during ESRH procedures is pointed out.

Absorption↗
PubMed2006

The magnitude and time-dependence of the apoptotic response of normal and malignant cells subjected to ionizing radiation versus hyperthermia.

PURPOSE: The purpose of the study was to examine the optimal time of exposure and dose of heat and ionizing radiation that results in the killing of human cancer cells in vitro via apoptosis vs. necrosis. MATERIALS AND METHODS: Human mammary carcinoma, colorectal carcinoma and normal bovine capillary endothelial (BCE) cell lines were subjected to 20 Gy ionizing radiation and 6, 12, 24, and 72 h later assessed for apoptosis using detection of apoptotic bodies and caspase assays. Necrosis was detected by loss of cells from the surface and lactate dehydrogenase (LDH) release. The colorectal carcinoma cells were subjected to hyperthermia using temperatures ranging from 39 - 44 degrees C for 5, 15 or 45 min. exposures and at varying times post-treatment, apoptosis and necrosis were measured. RESULTS: In response to ionizing radiation, none of the cells underwent necrosis and some cell types apoptosed 24 and 72 h posttreatment. The colorectal cancer cells exhibited a steady increase of apoptosis at 6, 12, and 24 h. When these cells were exposed to 40 degrees C for 5 min, caspases increased within 6 h and a significant fraction (50%) of cells apoptosed. If the time of exposure to 40 degrees C was increased to 15 or 45 min, 80% and 100% of the dying cells apoptosed, respectively. A temperature of 39 degrees C did not cause cell death even after 45 min exposures. If heat was elevated to 42 or 44 degrees C, increased necrosis was observed with a corresponding decrease in apoptosis. CONCLUSIONS: These studies reveal time and temperature dependent in vitro cell responses to ionizing radiation and water-bath hyperthermia.

Animals↗
PubMed1983

Attempts at aerosol control in a turkey rearing confinement with negative air ionization.

Aerosol control is a significant problem in agriculture and industry. Two separate studies were conducted to determine the effectiveness of a "negative air ionization" system in aerosol control. The first study was conducted with a turkey "brooder" barn and a control for a six-week period. The second study was conducted with a turkey "grow-out" barn and a control for a twelve-week period. Sampling parameters for both studies included environmental aerosol sampling, ion imbalance measurements, relative humidity, temperature and barometric pressure measurements and daily turkey mortality. Study two also included post study bird weights. Results of sampling parameters were consistent between study one and study two. No significant difference was found between test and control total average aerosol concentration for both studies. Ion imbalance measurements served to indicate that test environments were negatively ionized while control environments experienced normal environmental conditions. Meteorological parameters did not significantly affect aerosol concentrations. Normal variations in bird mortality were observed in the first study, but death rates increased with ionization in the latter. Overall, it was determined that the "negative air ionization" could not be considered as an effective means of aerosol control in turkey rearing confinements.

Aerosols↗
PubMed2002

Hammerhead ribozyme against gamma-glutamylcysteine synthetase attenuates resistance to ionizing radiation and cisplatin in human T98G glioblastoma cells.

Glioblastoma cells are highly malignant and show resistance to ionizing radiation, as well as anti-cancer drugs. This resistance to cancer therapy is often associated with a high concentration of glutathione (GSH). In this study, the effect of continuous down-regulation of gamma-glutamylcysteine synthetase (gamma-GCS) expression, a rate-limiting enzyme for GSH synthesis, on resistance to ionizing radiation and cisplatin (CDDP) was studied in T98G human glioblastoma cells. We constructed a hammerhead ribozyme against a gamma-GCS heavy subunit (gamma-GCSh) mRNA and transfected it into T98G cells. (1) The transfection of the ribozyme decreased the concentration of GSH and resulted in G1 cell cycle arrest of T98G cells. (2) The transfection of the ribozyme increased the cytotoxicity of ionizing radiation and CDDP in T98G cells. Thus, hammerhead ribozyme against gamma-GCS is suggested to have potential as a cancer gene therapy to reduce the resistance of malignant cells to ionizing radiation and anti-cancer drugs.

Antineoplastic Agents↗
PubMed2005

Cooperative antitumor effect of multitargeted kinase inhibitor ZD6474 and ionizing radiation in glioblastoma.

PURPOSE: Glioblastoma multiforme is an aggressive disease in which vascular endothelial growth factor (VEGF) and the EGF receptor (EGFR) are implicated in tumor growth, relapse, and resistance to radiotherapy and chemotherapy. The VEGF receptors VEGFR-1 (flt-1) and VEGFR-2 (KDR), typically present on endothelial cells, have also been identified in human glioblastoma tissues and cell lines. In addition, EGFR is dysregulated in the majority of human glioblastomas and EGFR overexpression correlates with shorter survival. We have investigated the antitumor and antiangiogenic effect of ZD6474, an inhibitor of both VEGFR and EGFR signaling as a single agent and in combination with ionizing radiation. EXPERIMENTAL DESIGN: We have used ZD6474 and/or ionizing radiation in human glioblastoma cell lines D54 and U251 in vitro and in nude mice bearing established xenografts. The effects of treatment on tumor blood vessels and protein expression were evaluated by Western blot and immunohistochemistry. RESULTS: As single agents, ionizing radiation and ZD6474 caused a dose-dependent inhibition of soft agar growth in D54 and U251 cell lines, whereas a cooperative effect was obtained in combination. Treatment of mice bearing D54 xenografts with either ZD6474 or radiotherapy alone caused tumor growth inhibition that was reversible upon treatment cessation. A cooperative and long-lasting inhibition of tumor growth was obtained with ZD6474 in combination with concomitant radiotherapy. The antiproliferative effect was accompanied by inhibition of VEGF protein expression and inhibition of angiogenesis as measured by vessel counting. CONCLUSION: This study shows the antitumor activity of ZD6474 in combination with ionizing radiation in glioblastoma both in vitro and in vivo, and provides a scientific rationale to evaluate ZD6474 alone or in combination with radiotherapy in patients affected by this disease.

Animals↗
PubMed2006

Controlled trial of naturalistic dawn simulation and negative air ionization for seasonal affective disorder.

OBJECTIVE: This trial assessed two novel nonpharmaceutical treatments for winter depression-naturalistic dawn simulation and high-density negative air ionization-delivered during the final hours of sleep. METHOD: The patients were 99 adults (77 women and 22 men) with the winter seasonal pattern of major depressive disorder (94 cases) and bipolar II disorder (five cases). Five parallel groups received 1) dawn simulation (0.0003-250 lux in the pattern of May 5 at 45 degrees north latitude); 2) a dawn light pulse (13 minutes, 250 lux, with an illuminant dose of 3.25x10(3) lux-minutes matched to the simulated dawn); 3) postawakening bright light (30 minutes, 10,000 lux); 4) negative air ionization at high flow rate (93 minutes, 4.5x10(14 )ions/second); or 5) ionization at low flow rate (93 minutes, 1.7x10(11) ions/second). The symptoms were assessed over 3 weeks with the Structured Interview Guide for the Hamilton Depression Rating Scale-Seasonal Affective Disorder Version. RESULTS: Posttreatment improvement results were bright light, 57.1%; dawn simulation, 49.5%; dawn pulse, 42.7%; high-density ions, 47.9%; and low-density ions, 22.7% (significantly lower than the others). Contrary to the authors' hypothesis, analysis of variance failed to find superiority of dawn simulation to the dawn pulse or bright light. However, the dawn pulse led to a pattern of residual or exacerbated depressive symptoms similar to those seen in low-density ion nonresponders. CONCLUSIONS: Naturalistic dawn simulation and high-density ionization are active antidepressants that do not require the effort of postawakening bright light therapy. They can be considered candidate alternatives to bright light or medication.

Adult↗