Ronald Walter - Academia.edu (original) (raw)

Papers by Ronald Walter

Inorganic Chemistry, 2000

Cationic mu-oxo V(III) dimers of the type [V2OL4Cl2]2+ (L = 1,10-phenanthroline, 3,4,7,8-tetramet... more Cationic mu-oxo V(III) dimers of the type [V2OL4Cl2]2+ (L = 1,10-phenanthroline, 3,4,7,8-tetramethyl-1,10-phenanthroline, 4,7-diphenyl-1,10-phenanthroline; or 2,2'-bipyridine) are shown to interact very strongly with DNA and to lead ultimately to its degradation. Spectroscopic binding studies, electrophoreses, DNA melting temperature experiments, and other tests on the parent 1,10-phenthroline complex all yield results consistent with tight binding. However, the exact nature of the binding--i.e., intercalative, groove binding, electrostatic, or covalent--remains unclear. Resonance Raman spectroscopy is found to be a powerful method for studying the interaction of these mu-oxo V(III) dimers with DNA and shows that in frozen aqueous solution, the parent complex [V2O(phen)4Cl2]2+ undergoes initial aquation, followed by the reaction of the aquated species with the DNA. Once the V(III) dimer is bound to the DNA, redox takes place, leading to the formation of alkaline-sensitive lesions. Hydrogen peroxide is implicated as a partner in this redox event, based on the effects of the enzymes SOD and catalase.

Chemical Communications, 1996

Plasmid DNA is cleaved by dimeric 0x0-bridged vanadium(II1) complexes without exogenous oxidants ... more Plasmid DNA is cleaved by dimeric 0x0-bridged vanadium(II1) complexes without exogenous oxidants or reductants. Some naturally occuring antitumour antibiotics such as bleomy-cin require metal ions as cofactors for DNA strand scissi0n.l This has stimulated the development of ...

Rapid Communications in Mass Spectrometry, 2005

Photochemistry and Photobiology, 1983

Advances in experimental medicine and biology, 2016

Besides recently developed zebrafish cancer models, other fish species have been employed for man... more Besides recently developed zebrafish cancer models, other fish species have been employed for many years as cancer models in laboratory studies. Two models, namely in Xiphophorus and medaka have proven useful in providing important clues to cancer etiology. Medaka is a complementary model to zebrafish in many areas of research since it offers similar resources and experimental tools. Xiphophorus provides the advantages of a natural ("evolutionary mutant") model with established genetics. Xiphophorus hybrids can develop spontaneous and radiation or carcinogen induced cancers. This chapter describes the tumor models in both species, which mainly focus on melanoma, and summarizes the main findings and future research directions.

BMC genomics, 2016

A growing number of studies report an abnormal expression of Piwi-interacting RNAs (piRNAs) and t... more A growing number of studies report an abnormal expression of Piwi-interacting RNAs (piRNAs) and the piRNA processing enzyme Piwi in many cancers. Whether this finding is an epiphenomenon of the chaotic molecular biology of the fast dividing, neoplastically transformed cells or is functionally relevant to tumorigenesisis is difficult to discern at present. To better understand the role of piRNAs in cancer development small laboratory fish models can make a valuable contribution. However, little is known about piRNAs in somatic and neoplastic tissues of fish. To identify piRNA clusters that might be involved in melanoma pathogenesis, we use several transgenic lines of medaka, and platyfish/swordtail hybrids, which develop various types of melanoma. In these tumors Piwi, is expressed at different levels, depending on tumor type. To quantify piRNA levels, whole piRNA populations of testes and melanomas of different histotypes were sequenced. Because no reference piRNA cluster set for me...

Journal of Bacteriology, Jun 1, 1988

The Journal of Cell Biology, 1988

In Silico Biology, Feb 1, 2005

Teleost fish genome projects involving model species are resulting in a rapid accumulation of gen... more Teleost fish genome projects involving model species are resulting in a rapid accumulation of genomic and expressed DNA sequences in public databases. The expressed sequence tags (ESTs) collected in the databases can be mined for the analysis of both structural and functional genomics. In this study, we in silico analyzed 49,430 unigenes representing a total of 692,654 ESTs from four model fish for their potential use in developing simple sequence repeats (SSRs), or microsatellites. After bioinformatical mining, a total of 3,018 EST derived SSRs (EST-SSRs) were identified for 2,335 SSR containing ESTs (SSR-ESTs). The frequency of identified SSR-ESTs ranged from 1.5% for Xiphophorus to 7.3% for zebrafish. The dinucleotide repeat motif is the most abundant SSR, accounting for 47%, 52%, 64%, and 78% for medaka, Fundulus, zebrafish, and Xiphophorus, respectively. Simulation analysis suggests that a majority of these EST-SSRs have sufficient flanking sequences for polymerase chain reaction (PCR) primer design. Comparative DNA sequence analyses of SSR-ESTs identified several cross-species SSRs and sequences that may be used as cross-reference genes in comparative studies. For example, the flanking sequences of one SSR (CTG)n within the pituitary tumor-transforming gene (PTTG) 1 interacting protein (PTTGIP), showed conservation spanning the medaka, Fundulus, human, and mouse genomes. This study provides a large body of information on EST-SSRs that can be useful for the development of polymorphic markers, gene mapping, and comparative genome analysis. Functional analysis of these SSR-ESTs may reveal their role in metabolism and gene evolution of these model species.

Next Generation Sequencing - Advances, Applications and Challenges, 2016

Photochemistry and Photobiology, Jul 31, 2000

Molecular and Biochemical Parasitology, Apr 30, 1991

Science of aging knowledge environment : SAGE KE, Jan 26, 2003

The fusion of male- and female-derived gametes initiates the phenomenal process of producing a hi... more The fusion of male- and female-derived gametes initiates the phenomenal process of producing a highly complex mammalian organism. Successful reproduction is so important that mammals invoke a battery of protective mechanisms for the germ cell lineages that function to maximize genetic integrity while still allowing genetic diversity and adaptation. Protective mechanisms likely include, but are not limited to, robust DNA repair to safeguard genetic integrity and apoptosis to remove cells with intolerable levels of DNA damage. Analyses of spontaneous mutant frequencies are generally consistent with germline DNA being stringently maintained relative to somatic tissues. Despite the rigorous protection afforded germ cells, genetic integrity is observed to decline with increased maternal and paternal age. It is not yet clear whether cells in the germ line truly age or whether other processes decline or become dysfunctional with age. For example, in a younger animal, the differentiation an...

Comparative biochemistry and physiology. Toxicology & pharmacology : CBP, 2015

We report RNA-Seq results from skin of X. maculatus Jp 163 B after exposure to various doses of &... more We report RNA-Seq results from skin of X. maculatus Jp 163 B after exposure to various doses of "cool white" fluorescent light (FL). We show that FL exposure incites a genetic transcriptional response in skin nearly as great as observed for UVB exposure; however, the gene sets modulated due to exposure to the two light sources are quite different. Known light responsive genes involved in maintaining circadian cycling (e.g., clock, cry2a, cry1b, per1b, per2, per3, and arntl1a) exhibited expected shifts in transcriptional expression upon FL exposure. Exposure to FL also resulted in down-regulated transcription of many genes involved with cell cycle progression (e.g., cdc20, cdc45, cdca7b, plk1, cdk1, ccnb-3, and cdca7a) and chromosome segregation (e.g., cenpe, cenpf, cenpi, cenpk, cenpo, cenpp, and cenpu; cep70; knstrm, kntc, mcm2, mcm5; smc2). In addition, several DNA replication and recombination repair genes (e.g., pola1, pole, rec52, rad54l, rpa1, and parpbp) exhibit red...

Metrology, Inspection, and Process Control for Microlithography XIX, 2005

AIXUV GmbH and partners have developed a high speed Reflectometer for EUV mask-blanks which is fu... more AIXUV GmbH and partners have developed a high speed Reflectometer for EUV mask-blanks which is fully compliant with the SEMI-standard P38 for EUV-mask-blank metrology. The system has been installed in June 2004 at SCHOTT Lithotec AG. It features high throughput, high lateral and spectral resolution, high reproduci-bility and low absolute uncertainty. Using AIXUV&amp;amp;amp;amp;amp;#39;s EUV-LAMP and debris mitigation, low cost-of-ownership and

Emerging Lithographic Technologies IX, 2005

Mask Blanks for EUV Lithography require a lot of new properties and features compared to standard... more Mask Blanks for EUV Lithography require a lot of new properties and features compared to standard Chrome-on-Glass mask blanks. SCHOTT Lithotec has introduced all relevant technology steps to manufacture EUV mask blanks. Starting from completely new low thermal expansion substrate materials with significantly improved surface quality over multilayer coatings for EUV reflection up to new absorber layers with improved dry