Industry-relevant magnetron sputtering and cathodic arc ultra-high vacuum deposition system for in situ x-ray diffraction studies of thin film growth using high energy synchrotron radiation.

We present an industry-relevant, large-scale, ultra-high vacuum (UHV) magnetron sputtering and cathodic arc deposition system purposefully designed for time-resolved in situ thin film deposition/annealing studies using high-energy (>50 keV), high photon flux (>10(12) ph/s) synchrotron radiation. The high photon flux, combined with a fast-acquisition-time (<1 s) two-dimensional (2D) detector, permits time-resolved in situ structural analysis of thin film formation processes. The high-energy synchrotron-radiation based x-rays result in small scattering angles (<11°), allowing large areas of reciprocal space to be imaged with a 2D detector. The system has been designed for use on the 1-tonne, ultra-high load, high-resolution hexapod at the P07 High Energy Materials Science beamline at PETRA III at the Deutsches Elektronen-Synchrotron in Hamburg, Germany. The deposition system includes standard features of a typical UHV deposition system plus a range of special features suited for synchrotron radiation studies and industry-relevant processes. We openly encourage the materials research community to contact us for collaborative opportunities using this unique and versatile scientific instrument.

Photochemical reactions and phototoxicity of sterols: novel self-perpetuating mechanisms for lipid photooxidation.

Sterols are important lipid components that may contribute to phototoxicity. We have found that phototoxic response in earthworms is related to sterols extractable with lipophilic solvents. The photochemically active compounds in worm lipids are 5,7,9(11),22-ergostatetraen-3 beta-ol (9-DHE) and 5,7,9(11)-cholestartien-3 beta-ol (9-DDHC), respectively. Human skin lipids are known to contain 9-DHE. We have also found 9-DDHC in human skin, which is reported here for the first time. In the presence of an excess of the corresponding 5,7-dienes (ergosterol of 7-dehydrocholesterol), these photoactive sterols constitute a self-regenerating source of singlet molecular oxygen (1O2) during irradiation in vivo or in vitro with UVA (315-400 nm). The quantum yield for photosensitization of 1O2 by 9-DHE was estimated to be 0.09. The 1O2 is scavenged by the dienes and the rate constant for 1O2 quenching by ergosterol was found to be 1.2 x 10(7) M-1 s-1 in methyl t-butyl ether (MTBE). This scavenging ultimately leads to the production of 5,8-endoperoxide and hydrogen peroxide. Photochemically induced superoxide radical was also produced on irradiation of sterol 5,7,9-trienes and trapped with the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO). The production of singlet oxygen, peroxides and radicals by the sterols may be significant in the cell damaging and tumor promoting action of UVA light on skin.

Formation of N-7-(2-carbamoyl-2-hydroxyethyl)guanine in DNA of the mouse and the rat following intraperitoneal administration of [14C]acrylamide.

Acrylamide is an alkylating agent which reacts very slowly in direct reactions with DNA and is negative in the Ames test, but is carcinogenic in mice and rats. In order to explain the cancer-initiating properties of acrylamide we have studied DNA adduct formation in vitro with a metabolizing system and in vivo in mice and rats following i.p. administration of 14C-labeled acrylamide. A major adduct found in both species was N-7-(2-carbamoyl-2-hydroxy-ethyl)guanine, formed by reaction of the DNA with the epoxide metabolite glycidamide. The levels of this adduct were similar in the different organs of the two rodent species, which supports the notion that glycidamide is relatively evenly distributed among tissues and that the organ-specificity in acrylamide carcinogenesis cannot be explained by a selective accumulation of the DNA-reactive metabolite in target organs.

Generation of hydrogen peroxide by incidental metal ion-catalyzed autooxidation of glutathione.

Autooxidation of reduced glutathione in 50 mM buffer at pH 7.9 is indetectably slow in the presence of 1 mM DETAPAC, EDTA, TET, or tripyridine, but passing buffer through Chelex resin was insufficient to remove traces of catalytically active metals. Production of hydrogen peroxide during glutathione autooxidation was catalyzed by traces of Fe+2 or Cu+2, and to a much lesser extent by Cu+1 and Ni+2, but not to a detectable extent by Na+1, K+1, Fe+3, Al+3, Cd+2, Zn+2, Ca+2, Mg+2, Mn+2, or Hg+2. Cysteine was a much better precursor for hydrogen peroxide production than were cysteine sulfinic or sulfonic acids. The chelators EGTA, NTA, bipyridine, dimethyl glyoxime, salicylate, and Desferal were ineffective at preventing autooxidation. EDDA and 8-hydroxyquinoline were partially effective. Catalase could completely prevent the accumulation of detectable H2O2, but superoxide dismutase was only slightly inhibitory. Hydroxyl radical and singlet oxygen quenching agents (mannitol and histidine) stimulated. A mechanism for the production of H2O2 during trace metal catalyzed oxidation of glutathione is proposed, involving glutathione-complexed metal and dissolved oxygen. Although a radical intermediate can not be ruled out, no radical initiated chain reaction is necessary.

Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on lipid peroxidation in microsomal systems in vitro.

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) when added to suspensions of rat hepatic microsomes in the presence of NADPH has little influence on the peroxidation of microsomal lipids unless the system also contains complexed ferric ion, in which case TCDD stimulates. This stimulation does not appear to require metabolism of the TCDD. Peroxidation was monitored by production of thiobarbiturate-reactive substances (malondialdehyde and dienals), production of conjugated dienes, and disappearance of polyunsaturated fatty acids. Stimulation of lipid peroxidation by TCDD in a mixed lysosome-microsome preparation resulted in significantly decreased 'leakage' of acid phosphatase into the medium, implying an effect on lysosomal membranes. Consideration both of the present results and data in the literature leads to the conclusion that it is premature to attempt to define the relationship between enzyme induction, lipid peroxidation and TCDD lethality.

Pharmacokinetics, interactions with macromolecules and species differences in metabolism of DEHP.

The recent long-term carcinogenesis bioassay of di(2-ethylhexyl) phthalate (DEHP) in rats and mice reported by the National Toxicology Program was the first such bioassay to implicate DEHP as a hepatocarcinogen. At the levels of DEHP fed (up to 1.2% of the diet for two years), the livers of the rats would have been exposed to unhydrolyzed diester; this would not have been the case at lower dosages. Extrapolation to lower dosages is therefore questionable. We do not have sufficient pharmacokinetic data in mice to evaluate the dose relationships as yet. Rodents differ conspicuously from primates in their manner of metabolizing DEHP, both in terms of the demand made on the oxidation potential of the liver and in the chemical properties of the major metabolites. The relevance of these differences must be determined before rodent species can be considered models for the effects of DEHP in humans. Radioactivity from carbonyl-labeled DEHP did not associate with purified protein, RNA or DNA from rat liver in vivo. Label from 2-ethyl-(1-14C)-hexyl-labeled DEHP or mono(2-ethylhexyl) phthalate (MEHP) did appear to associate strongly with purified DNA, but label from free 14C-labeled 2-ethylhexanol did not. The apparent binding from DEHP and MEHP was not exchangeable, but was not proven to be covalent. This phenomenon needs additional study.

Dibutyryl cyclic adenosine 3'5' monophosphate, sugar transport, and regulatory control of cell division in normal and transformed cells.

Swiss 3T3 cells exhibit contact-regulated cell growth and have a lower ability to transport 2-deoxyglucose than polyoma (Py)-transformed 3T3 cells. Py3T3 cells treated with dibutyryl cyclic adenosine 3'5' monophosphate (dBcAMP) and theophylline have reduced cell growth and transport 2-deoxyglucose at the same rate as normal 3T3 cells. Evidence that the cessation of cell growth and reduced transport abilities in Py3T3 cells does not represent a return to contact-regulated growth comes from the following observations. First, treating high density Py3T3 cells with dBcAMP allows more than two doublings of cell number, even though ability to transport 2-deoxyglucose is returned to levels equal to those of normal 3T3 cells. Second, dBcAMP prevents serum-stimulated increases in 2-deoxyglucose transport in Py3T3 but not in 3T3 cells.