Repair evidence

Gunz, D., Hess, M.T., and Naegeli, H. (1996) Recognition of DNA adducts by human nucleotide excision repair. Evidence for a thermodynamic probing mechanism. /. Biol. Chem., 271, 25089-25098. 

There are no classification requirements for routine NDE beyond thickness testing and visual inspection except for repairs, modifications or where service history has identified a specific problem in which case the Surveyors will request NDE at the same locations in similar ships. Under circumstances where visual inspection has found evidence of fatigue cracking the Surveyor can also call for NDE to assess the full extent... 

Metallic devices have been used to repair and replace parts of the human body for centuries. Archaeological evidence clearly indicates that surgical procedures were performed in several ancient civilisations. The use of surgical metal implants in humans was first recorded in 1562 when a gold prosthesis was used to close a defect in a cleft palate. ... 

The outstanding virtue of zinc-rich paints is simplicity in application. No special equipment is required and the operation can, of course, be carried out on site, large or small structures being equally suitable for treatment. While there is some evidence that the zinc-rich paints will reduce iron oxides remaining on the steel surface, proper surface preparation is as important here as with traditional paints if the best results are to be achieved. The main use of zinc-rich paints is to protect structural steel-work, ships hulls, and vulnerable parts of car bodies, and to repair damage to other zinc coatings. 

Although mast cells and basophils probably account for >90% of stored histamine in the body, histamine is also present in platelets, enterochromaffin-like cells, endothelial cells, and neurons. Histamine can act as a neurotransmitter in the brain. Histaminergic nerves have their cell bodies within a very small area of the brain (the magnocellular nuclei of the posterior hypothalamus) but have axons in most areas of the forebrain. There is also evidence for axons projecting into the spinal (Fig. 1) cord. Finally, there is evidence that histamine synthesis can be induced in tissues undergoing rapid tissue growth and repair. In certain neonatal tissues (e.g. liver), the rate of synthesis of this unstored diffusable histamine (termed nascent histamine) is profound and may point to a role for histamine is cell proliferation. 

There is strong evidence that DNA adduction by these bulky reactive metabolites of PAHs is far from random, and that there are certain hot spots that are preferentially attacked. Differential steric hindrance and the differential operation of DNA repair mechanisms ensure that particular sites on DNA are subject to stable adduct formation (Purchase 1994). DNA repair mechanisms clearly remove many PAH/ guanine adducts very quickly, but studies with P postlabeling have shown that certain adducts can be very persistent—certainly over many weeks. Evidence for this has been produced in studies on fish and Xenopus (an amphibian Reichert et al. 1991 Waters et al. 1994). 

There is some evidence that carotenoids (particularly P-carotene) may influence both arms of the DNA damage repair balance (Astley et al., 2002 Pillion et al, 1998). 

Kasai, H., Crain, P.F., Kuchino, Y., Nishimura, S., Oot-suyama, A. and Tanooka, H. (1986). Formation of 8-hydroxyguanine moiety in cellular DNA by agents producing oxygen radicals and evidence for its repair. Carcint nesis 7, 1849-1858. 

Figure 3 shows an ion exchange HPLC analysis of the irradiation experiment performed with the duplex 13. The starting duplex 13 elutes at a retention time of 13 min. The cleaved DNA strand has a retention time of 11 min. Clearly evident again is the clean conversion of the unrepaired duplex 13 into the cleaved, repaired , DNA fragment. 

Incorporation of an artificial flavin nucleobase and of a cyclobutane pyrimidine dimer building block into DNA DNA double strands, DNArPNA hybrid duplexes, and DNA-hairpins, provided compelling evidence that an excess electron can hop through DNA to initiate dimer repair even at a remote site. The maximum excess electron transfer distance realised so far in these defined Donor-DNA-Acceptor systems is 24 A. New experiments are now in progress to clarify whether even larger transfer distances can be achieved. 

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