A colorimetric procedure for determination of small amounts of cyanide and thiocyanate, involving the synthesis of a pyridine dyestuff by the reaction of pyridine and an aromatic amine, has been simplified for the estimation of thiocyanate alone in biological fluids. Replacement of benzidine with p-phenylenediamine in the colorimetric reaction has both improved the precision of the analytical procedure and avoided a carcinogenic hazard. This method has been used to follow the decrease in plasma thiocyanate associated with abstinence from cigarette smoking, and its subsequent increase upon resumption. It has also been used to measure the plasma and urinary thiocyanate concentrations of patients suffering from the particular toxic amblyopias—tobacco amblyopia and Leber’s hereditary optic atrophy— believed to be associated with cyanide toxicity, and to follow the increased thiocyanate concentrations that accompany significant improvements in the patients’ vision brought about by various treatments.

Serum total creatine kinase (CK) and the lactate dehydrogenase (LDH) isoenzymes were studied in 38 sedentary middle-aged men (aged 35-50 yrs) during a 30 week marathon training programme. Basal CK activity rose by 33% after 15 weeks but a significant rise (27%) in LDH activity took 30 weeks to occur. Post-exercise (maximum test on a bicycle ergometer) CK and LDH activities were higher than pre-exercise levels but the increment in enzyme activity following exercise did not change. LDH1 and LDH2 isoenzyme activity increased by 2.5% and 4% of total LDH respectively while LDH3 and LDH5 decreased by 3.9% and 2.4% respectively over 30 weeks. Post marathon total CK did not correlate with finishing time at 30 mins or 30 hrs post race. The range of CK MB isoenzyme activity at 30 mins post race was 1.8-9.8% of total CK with 11 subjects having a value above 6%. The training programme appears not to have affected muscle CK and LDH release during exercise but isoenzyme distribution changes reflect the adaptations known to occur in muscle during endurance training. Unfortunately only 16 subjects were available for all the investigations, and it is these upon whom most of the data were obtained.

A microdiffusion technique has been used to separate and concentrate the nanomole amounts of cyanide in whole blood, and to permit its simplified colorimetric estimation (1). With this technique cyanide was measured in whole blood from normal smokers, normal nonsmokers, and patients suffering from tobacco amblyopia. Cyanide was also measured in whole blood from vitamin B12-deficient and normally fed Wistar rats. From the experimental animal results and results from patients, it is suggested that a more suitable index of cyanide exposure may be the alteration of plasma thiocyanate rather than the direct determination of whole blood cyanide.

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The effects of a 30 week exercise programme on serum lipid values, blood pressure, and cardiac function were assessed in a group of sedentary men aged 35-50 training for their first marathon. Mean serum cholesterol concentration (n=33) fell by 12% from 6-54 (SE 0.18) to 5-76 (0-15) mmol/l (mean fall mmol/l; 95% confidence interval 0-52 to 1-04 mmoVIl), serum triglyceride concentration (n=33) by 22% from 156 (0.17) to 1-21 (0-09) mmol/l (mean fall 0 34 mmol/l; 95% confidence interval 0-12 to 056 mmol/l), and mean blood pressure (n=27) by 10% from 102 (2) ventricular end-diastolic volume (n= 16) increased with training; as a result of this and an increased exercise left ventricular ejection fraction peak exercise cardiac output increased from 19.9 (1-2) to 23-1 (3-0) I/min (mean rise 3-2 I/min; 95% confidence interval 1-5 to 5-0 I/min). Maximum oxygen consumption increased from 33-9 (1.6) to 39-0 (1.3) ml/kg/min (mean rise 5-0 ml/kg/min; 95% confidence interval 1-8 to 8.2 ml/kg/min).This study showed favourable effects on coronary risk factors and cardiac function and supports the place ofregular exercise in coronary prevention programmes. IntroductionThe sight of runners on the streets of Britain has become commonplace. This burgeoning of interest has been most evident in nonathletes and is reflected in the number of popular marathons that have taken place in recent years. It is interesting to speculate on the motives behind this activity, though it is a popular belief that exercise is good for the individual and especially for the heart. Though much is known about the effect of training on cardiorespiratory function in athletes, thereis littleinformation concerning the benefits (or otherwise) of prolonged endurance training in previously unfit runners, many of whom are middle aged. Indeed, concern has been expressed about the possible hazards of prolonged exercise in this age group, given the reports of sudden death in marathon runners.