Primary Events in the Radiolysis of Nucleic Acids and their Components

The radiolysis of dilute aqueous solutions of DNA and its components is discussed, with particular reference to the rates of reaction and the sites of reaction of the primary reactive species, OH, H and e^?_aq. Recent work on the formation and subsequent reactions of OH? and electron-adducts of pyrimidines is described.     

Quality and consumption of oxidized lipids from deep-frying fats and oils in New Zealand

Samples of beef dripping and plant oil-based deep-frying fat were obtained from fast-food premises in Christchurch, New Zealand, as well as samples of deep-fried battered fish and potato chips. The fat in these samples was analyzed for level of oxidation by measuring acid value, peroxide value, polar compounds, thiobarbituric acid-reactive substances (TBARS), and conjugated dienes. The acid and peroxide value results were contradictory when compared with limits set in the New Zealand Food Regulations 1984, but the levels of polar compounds were generally below 25%, indicating that the fats were well maintained. The TBARS and conjugated diene levels were compared with those for oxidized corn oil used in a feeding trial and indicated a similar oxidation level, although the amount of fat consumed in the feeding trial would be 30–50% higher. These results show that well-maintained deep-frying fat has oxidation levels sufficient to cause elevation of plasma lipid oxidation levels as observed in a human feeding trial.     

Bed rest, diet and working capability in liver disease (author's transl)

General views concerning bed rest, diet and working capability in liver disease have changed during the last years. Rigorous bed rest in acute viral hepatitis is necessary only for short periods of time; it is necessary in chronic liver disease only in rare cases and during the terminal stage, respectively. A liver diet does not exist. Normal palatable nutrition is completely adequate in liver disease. Restriction of protein and sodium chloride intake is indicated only in cases with incumbent coma or with ascites. Patients suffering from acute viral hepatitis are incapable of working; however, they can go back to work a few weeks after the acute stage. Estimation of disability to work in patients with chronic liver disease may be difficult; no general rules can be given; in chronic active hepatitis disability is proportional to the activity of the disease and may range from 20-100%. Fatty liver without inflammatory changes does not influence working capability.     

Cyanogen bromide treatment of methionine-containing compounds

The preparation of a series of X-Met-Gly-OEt and X-Met-Phe-OMe and their treatment with CNBr in either 70% or 97-100% formic acid at 25 degrees C are described where X is methanesulfonyl (mesyl), p-nitrobenzyloxycarbonyl, phthaloyl, trifluoroacetyl, acetyl, formyl, or tert-butyloxycarbonyl. Total cleavage of the peptide esters was found with mesyl-, p-nitrobenzyloxycarbonyl-, phthaloyl-, and trifluoroacetylmethionyl derivatives which indicated the suitability of these derivatives as amino protecting groups in peptide synthesis. Treatment of the acetylmethionyl peptide esters with CNBr in 70 and 97-100% formic acid resulted in 92 and 98% cleavage, respectively. With formylmethionyl peptide esters, about 85-95% cleavage was estimated when either 70 or 97-100% formic acid was used as the solvent. With the tert-butyloxycarbonylmethionyl derivatives, CNBr treatment in 70% formic acid resulted in about 93% cleavage of peptides, while treatment in 97-100% formic acid led to only 30-33% release of C-terminal amino acid esters. Quantitative cleavage of the carbonylbis(methionyl peptide esters) was observed. The reaction of CNBr with N-terminal methionyl derivatives containing free alpha-amino groups revealed that free methionine was quantitatively converted to homoserine lactone, whereas methionine ethyl ester and methionyl peptides (Met-Gly and Met-Phe) disappeared from the reaction mixture in 70% formic acid with only partial splitting of the ester (16%) or peptide bond (45%).     

Comparison of friction and lubrication of different hip prostheses

It is well documented that an important cause of osteolysis and subsequent loosening of replacement hip joints is polyethylene wear debris. To avoid this, interest has been renewed in metal-on-metal and ceramic-on-ceramic prostheses. Various workers have assessed the lubrication modes of different joints by measuring the friction at the bearing surfaces, using different lubricants. Measurements of friction factors of a series of hip prostheses were undertaken using carboxymethyl cellulose (CMC) fluids, silicone fluids, synovial fluid and different concentrations of bovine serum as the lubricant. The experimental results were compared with theoretical predictions of film thicknesses and lubrication modes. A strong correlation was observed between experiment and theory when employing CMC fluids or silicone fluids as the lubricant. Mixed lubrication was found to occur in the metal-on-metal (CoCrMo/CoCrMo) joints with all lubricants at a viscosity within the physiological range. This was also the case for the metal-on-plastic (CoCrMo/ultra-high molecular weight polyethylene) joints. The ceramic-on-ceramic (Al2O3/Al2O3) joints, however, exhibited full fluid film lubrication with the synthetic lubricants but mixed lubrication with the biological lubricants. Employing a biological fluid as the lubricant affected the friction to varying degrees when compared with the synthetic lubricants. In the case of the ceramic-on-ceramic joints it acted to increase the friction factor tenfold; however, for the metal-on-metal joints, biological fluids gave slightly lower friction than the synthetic lubricants did. This suggests that, when measuring friction and wear of artificial joints, a standard lubricant should be used.     

The piecewise-linear analysis of two connecting structures including the effect of clearance at the connections

A method of analysis is presented for two structures which have connections with clearance. It is assumed that the behaviour of the structures is described, by the movement of discrete nodes and that as the load on the structure changes, clearances open or close between corresponding nodes on the structures; each time this occurs the stiffness of the combined structure changes because its configuration has changed. Between these changes, the structure will behave linearly and the overall behaviour can be described as piecewise linear. Applications include diesel engine crankshafts with bearing clearances and the wrap-around problem in pin-and-eye connections.