DNA repair, DNA replication and human disorders: A personal journey

I was born in 1946 and grew up in the industrial north-west of England close to the city of Manchester. My parents were German- Jewish refugees, who left Germany fairly early, in 1933. My father helped to establish and was one of the directors of a tannery, which made leather for shoes and handbags. This was part of a group of tanneries established first in Strasbourg by my great-grandfather Ferdinand Oppenheimer. I would describe my childhood and adolescent years as comfortable by general post-war standards. I went to a state primary school and obtained a scholarship to Manchester Grammar School (MGS), a fairly prestigious secondary school. As a child I was always interested in chemistry but had little interest in or knowledge of biology. The educational system in the UK at that time was such that one had to specialise very early and as a consequence I have had no formal biology education since the age of 12, something I have managed to hide reasonably successfully for the rest of my life! In my final two years at MGS I studied just physics, chemistry and mathematics and obtained a scholarship to Pembroke College, Cambridge (England) to study Natural Sciences, with the intention of becoming a chemist. In the second year at Cambridge, one of the options was a course on biochemistry. Having no real idea what this was, I read a book about it in the summer of 1965, and was truly astonished and excited to discover that the basis of life was just a bunch of rather complicated organic chemistry reactions. So I took the biochemistry course in my second year. By the end of that year, I was fed up with chemistry and for my final year I chose to do biochemistry rather than chemistry, a decision I have not regretted. The biochemistry lectures must have been pretty up-to-date, as we were told briefly about the discovery of DNA repair by Dick Setlow [1], a topic that seemed rather esoteric at the time

Xeroderma Pigmentosum

Xeroderma pigmentosum (XP) is defined by extreme sensitivity to sunlight, resulting in sunburn, pigment changes in the skin and a greatly elevated incidence of skin cancers. It is a rare autosomal recessive disorder and has been found in all continents and racial groups. Estimated incidences vary from 1 in 20, 000 in Japan to 1 in 250, 000 in the USA, and approximately 2.3 per million live births in Western Europe. The first features are either extreme sensitivity to sunlight, triggering severe sunburn, or, in patients who do not show this sun-sensitivity, abnormal lentiginosis (freckle-like pigmentation due to increased numbers of melanocytes) on sun-exposed areas. This is followed by areas of increased or decreased pigmentation, skin aging and multiple skin cancers, if the individuals are not protected from sunlight. A minority of patients show progressive neurological abnormalities. There are eight XP complementation groups, corresponding to eight genes, which, if defective, can result in XP. The products of these genes are involved in the repair of ultraviolet (UV)- induced damage in DNA. Seven of the gene products (XPA through G) are required to remove UV damage from the DNA. The eighth (XPV or DNA polymerase h) is required to replicate DNA containing unrepaired damage. There is wide variability in clinical features both between and within XP groups. Diagnosis is made clinically by the presence, from birth, of an acute and prolonged sunburn response at all exposed sites, unusually early lentiginosis in sun-exposed areas or onset of skin cancers at a young age. The clinical diagnosis is confirmed by cellular tests for defective DNA repair. These features distinguish XP from other photodermatoses such as solar urticaria and polymorphic light eruption, Cockayne Syndrome (no pigmentation changes, different repair defect) and other lentiginoses such as Peutz-Jeghers syndrome, Leopard syndrome and Carney complex (pigmentation not sunassociated), which are inherited in an autosomal dominant fashion. Antenatal diagnosis can be performed by measuring DNA repair or by mutation analysis in CVS cells or in amniocytes. Although there is no cure for XP, the skin effects can be minimised by rigorous protection from sunlight and early removal of pre-cancerous lesions. In the absence of neurological problems and with lifetime protection against sunlight, the prognosis is good. In patients with neurological problems, these are progressive, leading to disabilities and a shortened lifespan

Wiring a periscope--ocelli, retinula axons, visual neuropils and the ancestrality of sea spiders.

The Pycnogonida or sea spiders are cryptic, eight-legged arthropods with four median ocelli in a 'periscope' or eye tubercle. In older attempts at reconstructing phylogeny they were Arthropoda incertae sedis, but recent molecular trees placed them as the sister group either to all other euchelicerates or even to all euarthropods. Thus, pycnogonids are among the oldest extant arthropods and hold a key position for the understanding of arthropod evolution. This has stimulated studies of new sets of characters conductive to cladistic analyses, e.g. of the chelifores and of the hox gene expression pattern. In contrast knowledge of the architecture of the visual system is cursory. A few studies have analysed the ocelli and the uncommon "pseudoinverted" retinula cells. Moreover, analyses of visual neuropils are still at the stage of Hanström's early comprehensive works. We have therefore used various techniques to analyse the visual fibre pathways and the structure of their interrelated neuropils in several species. We found that pycnogonid ocelli are innervated to first and second visual neuropils in close vicinity to an unpaired midline neuropil, i.e. possibly the arcuate body, in a way very similar to ancestral euarthropods like Euperipatoides rowelli (Onychophora) and Limulus polyphemus (Xiphosura). This supports the ancestrality of pycnogonids and sheds light on what eyes in the pycnogonid ground plan might have 'looked' like. Recently it was suggested that arthropod eyes originated from simple ocelli similar to larval eyes. Hence, pycnogonid eyes would be one of the early offshoots among the wealth of more sophisticated arthropod eyes

When giving some away makes sense to jump-start the diffusion process.

This paper uses an analytical model to examine when it makes sense to provide incentives to innovators to adopt a new product. The model allows for separate segments of innovators and imitators, each of which follows a Bass-type diffusion process. Interestingly “seeding” the market is optimal for a limited range of situations and these do not appear to include those where there is a downturn in sales (chasm) as sales move from the first to the second segment. Research has frequently identified different segments of adopters of new products. Categorizations include innovators vs imitators (Bass, 1969; Rogers, 1995; Mahahan et al., 1990; Im et al., 2003), technophiles vs “normal” people, and business vs consumer users. Further, considerable effort has gone into studying the influence of members of the first group on the second. This paper focuses on when, if ever, it makes sense for a manufacture of a new product to “seed” the market by subsidizing a few early adopters to speed the adoption process. The paper builds on earlier work by Kalish and Lilien (1983) which focused on the impact of widely available government subsidies on the adoption of socially desirable innovations (i.e. alternative energy sources) as well as the work of Jain et al. (1995). Unlike that work, we concentrate on providing subsidies (here free goods) to selective individuals in the context of a model which allows for separate segments of innovators and imitators and nests the standard Bass (1969) model.

Unstable particle's wave-function renormalization prescription

We strictly define two set Wave-function Renormalization Constants (WRC) under the LSZ reduction formula for unstable particles at the first time. Then by introducing antiparticle's WRC and the CPT conservation law we obtain a new wave-function renormalization condition which can be used to totally determine the two set WRC. We calculate two physical processes to manifest the consistence of the present wave-function renormalization prescription with the gauge theory in standard model. We also prove that the conventional wave-function renormalization prescription which discards the imaginary part of unstable particle's WRC leads to physical amplitude gauge dependent.Comment: 10 pages, 3 figure

A semi-automated non-radiactive system for measuring recovery of RNA synthesis and unscheduled DNA synthesis using ethynyluracil derivatives

Nucleotide excision repair (NER) removes the major UV-photolesions from cellular DNA. In humans, compromised NER activity is the cause of several photosensitive diseases, one of which is the skin-cancer predisposition disorder, xeroderma pigmentosum (XP). Two assays commonly used in measurement of NER activity are ‘unscheduled DNA synthesis (UDS)’, and ‘recovery of RNA synthesis (RRS)’, the latter being a specific measure of the transcription-coupled repair sub-pathway of NER. Both assays are key techniques for research in NER as well as in diagnoses of NER-related disorders. Until very recently, reliable methods for these assays involved measurements of incorporation of radio-labeled nucleosides. We have established non-radioactive procedures for determining UDS and RRS levels by incorporation of recently developed alkyne-conjugated nucleoside analogues, 5-ethynyl-2′-deoxyuridine (EdU) and 5-ethynyuridine (EU). EdU and EU are respectively used as alternatives for 3H-thymidine in UDS and for 3H-uridine in RRS. Based on these alkyne-nucleosides and an integrated image analyser, we have developed a semi-automated assay system for NER-activity. We demonstrate the utility of this system for NER-activity assessments of lymphoblastoid samples as well as primary fibroblasts. Potential use of the system for large-scale siRNA-screening for novel NER defects as well as for routine XP diagnosis are also considered

Preparation, Structure, and Reactivity of Nonstabilized Organoiron Compounds. Implications for Iron-Catalyzed Cross Coupling Reactions

A series of unprecedented organoiron complexes of the formal oxidation states −2, 0, +1, +2, and +3 is presented, which are largely devoid of stabilizing ligands and, in part, also electronically unsaturated (14-, 16-, 17- and 18-electron counts). Specifically, it is shown that nucleophiles unable to undergo β-hydride elimination, such as MeLi, PhLi, or PhMgBr, rapidly reduce Fe(3+) to Fe(2+) and then exhaustively alkylate the metal center. The resulting homoleptic organoferrate complexes [(Me4Fe)(MeLi)][Li(OEt2)]2 (3) and [Ph4Fe][Li(Et2O)2][Li(1,4-dioxane)] (5) could be characterized by X-ray crystal structure analysis. However, these exceptionally sensitive compounds turned out to be only moderately nucleophilic, transferring their organic ligands to activated electrophiles only, while being unable to alkylate (hetero)aryl halides unless they are very electron deficient. In striking contrast, Grignard reagents bearing alkyl residues amenable to β-hydride elimination reduce FeXn (n = 2, 3) to clusters of the formal composition [Fe(MgX)2]n. The behavior of these intermetallic species can be emulated by structurally well-defined lithium ferrate complexes of the type [Fe(C2H4)4][Li(tmeda)]2 (8), [Fe(cod)2][Li(dme)]2 (9), [CpFe(C2H4)2][Li(tmeda)] (7), [CpFe(cod)][Li(dme)] (11), or [Cp*Fe(C2H4)2][Li(tmeda)] (14). Such electron-rich complexes, which are distinguished by short intermetallic Fe−Li bonds, were shown to react with aryl chlorides and allyl halides; the structures and reactivity patterns of the resulting organoiron compounds provide first insights into the elementary steps of low valent iron-catalyzed cross coupling reactions of aryl, alkyl, allyl, benzyl, and propargyl halides with organomagnesium reagents. However, the acquired data suggest that such C−C bond formations can occur, a priori, along different catalytic cycles shuttling between metal centers of the formal oxidation states Fe(+1)/Fe(+3), Fe(0)/Fe(+2), and Fe(−2)/Fe(0). Since these different manifolds are likely interconnected, an unambiguous decision as to which redox cycle dominates in solution remains difficult, even though iron complexes of the lowest accessible formal oxidation states promote the reactions most effectively

On the Effect of Applying Mean Input Data in Long-Term Air Pollution Transport Models

The effect of applying mean (i.e. temporally and spatially averaged) input data (removal coefficients, wind velocity, travel distance between source and receptor) in a long-term model of the transport of heavy metals (especially As) in Europe's atmosphere has been investigated by running modified versions of this model. At 5 receptors considered in this study, the application of mean removal coefficients in the model resulted in an underprediction of concentration values and dry deposition, being approximately 0.75 times the original values, and an overestimation of wet deposition by a factor of approximately 1.5. The assumption of a straight travel of pollutants between a source and some receptor brings about an overestimation of concentration and deposition by a factor of approximately 1.2. The application of a mean wind velocity changed results only slightly. All occurring effects have also been investigated theoretically, so that assertions and formulae which are independent of the special model under consideration have been obtained