Cigarette smoking: profiles of thromboxane- and prostacyclin-derived products in human urine.

Thromboxane (TX) B2, 2,3-dinor-TXB2, 11-dehydro-TXB2, 6-oxoprostaglandin (PG)F1 alpha and 2,3-dinor-6-oxo-PGF1 alpha were measured in 24 h urine samples obtained from 30 apparently healthy chronic cigarette smokers and 37 closely matched non-smoking control subjects. Samples were analysed using a newly developed assay based on immunoaffinity chromatography and capillary column gas chromatography/electron capture negative ion chemical ionisation mass spectrometry. There were significant and comparable increases in the excretion rates of both 2,3-dinor-TXB2 and 11-dehydro-TXB2 in the smoking compared with the non-smoking group (2P less than 0.001). Excretion rates of 2,3-dinor-TXB2 were 418 +/- 35 and 265 +/- 26 pg/mg creatinine in the two groups, respectively. 11-Dehydro-TXB2 excretion rates were 440 +/- 54 and 221 +/- 18 pg/mg creatinine, respectively (mean +/- S.E.). There were significant (2P less than 0.05) positive correlations between average reported cigarette consumption and excretion of both thromboxane metabolites. There were small but significant (2P less than 0.02) increases in the excretion rates of both 6-oxo-PGF1 alpha and 2,3-dinor-6-oxo-PGF1 alpha in the smoking compared with the non-smoking group. There was no significant difference in the rates of excretion of TXB2 in the two groups. The effects of acute cigarette smoke exposure (five cigarettes in 2 h) was also studied in four normally non-smoking healthy volunteers. There was no significant change in the excretion rate of any of the eicosanoids measured during control and smoking periods (at least 2 weeks apart), indicating that increased TXA2 biosynthesis in chronic smokers is unlikely to be a consequence of acute platelet activation.

Continuous subcutaneous insulin infusion does not provoke significant acute-phase response.

C-reactive protein (CRP), the classical acute-phase reactant, and serum amyloid A protein (SAA), the putative precursor of AA-type amyloid fibrils, were measured in 62 diabetic patients. They were all attending their regular clinic appointments and had been asymptomatic during the 2 wk preceding sampling. CRP and SAA levels were similar in 18 patients on continuous subcutaneous insulin infusion (CSII), 27 patients treated by conventional insulin therapy (CIT), nine treated by diet only, and eight treated by diet and oral hypoglycemic agents, and were almost entirely within the normal range. It is concluded that CSII does not provoke an acute-phase reaction in diabetic patients and, while caution should always be exercised with a new form of treatment, it does not seem likely that CSII will predispose to the development of reactive systemic amyloidosis.

The effect of acute hyperglycemia on flow velocity in the macular capillaries.

The effect of acute hyperglycemia on retinal blood flow was measured in 12 diabetic patients (mean blood glucose, 276 mg%) on continuous subcutaneous insulin infusion and six nondiabetic controls (mean blood glucose, 198 mg%). Flow velocity measurements in macular capillaries were made using the blue field entoptic method. Retinal artery and vein diameters were measured using red-free fundus photographs. No significant change in flow velocity or retinal vessel diameter was noted in either group.

Does vitreous fluorophotometry reflect severity of early diabetic retinopathy?

To determine the relationship between vitreous fluorophotometry (VF) and severity of diabetic retinopathy (DR) 13 patients with mild to moderate background DR starting continuous subcutaneous insulin infusion were followed up serially for 12 months. They were studied by colour stereo retinal photographs, which were assessed by the Wisconsin Grading System, and by VF, which was assessed by the permeability index of the retina for fluorescein. By four months the severity of DR on colour photographs had deteriorated by at least one level in at least one eye in eight patients. In four patients the DR did not deteriorate. Assessment of anatomical abnormalities by severity of DR on colour photographs correlated well with the functional abnormalities of the blood-retinal barrier(s) assessed by VF, especially for the macular field. Comparison of permeability index data in the patients developing preproliferative or proliferative features of DR (group A) with the same data in patients who did not develop such changes (group B) indicated that group A patients had more severe DR than did group B patients at entry. Grading of colour photographs showed a similar trend but with greater overlap. Considerable overlap in fluorescein permeability remained between those subjects with no visible DR and those with microaneurysms with or without haemorrhages and small hard exudates.

Causes of death and risk factors in young and old diabetic patients referred to a retinopathy clinic.

The causes of death and associated risk factors are compared in young and old diabetic patients attending a retinopathy clinic. Mortality in those diagnosed under and over the age of 30 years is also examined in order to compare insulin-dependent with non-insulin-dependent patients. A defined cohort attending the Hammersmith Hospital Retinopathy Clinic was followed for an average of 11 years. Main outcome measures were standardized mortality ratios (SMRs) in different age/sex groups and relative hazard rates (RHRs) for possible risk factors related to mortality. The patients were divided into those aged under and over the age of 60 years at attendance at the clinic. The RHRs were smaller in the elderly for plasma urea [1.015 versus 1.107 (p < 0.01)]. Attenuation of risk was also suggested for systolic blood pressure (RHR of 1.005 in the elderly versus 1.015 in the younger patients) and for the effects of smoking [RHR of 1.17 (elderly patients) and 1.35 (younger patients)]. In those diagnosed under the age of 30 years, there were very high SMRs for renal disease, cerebrovascular disease (men only), ischemic heart disease, other heart disease, and respiratory disease (men only), but increased SMRs were also demonstrated in those diagnosed over the age of 30 years. The risk factors associated with poor survival were similar for those diagnosed over and under the age of 30 years: poor diabetic control, high systolic and diastolic blood pressure, and increased plasma urea. In conclusion, there was no evidence that blood sugar control or diastolic blood pressure were less important in older age groups. Plasma urea, systolic pressure, and being on insulin were less useful as predictors of mortality in the elderly, but were still important in patients diagnosed over the age of 30 years.

Diabetic retinopathy: I. The measurement of intercapillary area in normal retinal angiograms.

A method for the quantitation of areas of non-perfusion of retinal angiograms is described. The values for the area of the foveal avascular zone (FAZ) and the intercapillary areas in the perifoveal region of ten angiograms of normal subjects were determined. The reproducibility of measurement between and within observers was good, correlation coefficients being 0.9963 and 0.9945, respectively, for the FAZ. The inter- and intra-observer coefficients of correlation for the perifoveal intercapillary areas were 0.9284 and 0.8687, respectively. The upper limit of normal intercapillary area was determined to be 0.07 mm2 in the first degree from the FAZ, 0.04 mm2 in the second degree and 0.025 mm2 elsewhere in the macular field.

Computer-aided digitisation of fundus photographs.

A method is described for the analysis of standard retinal colour photographs with the facility to compare accurately photographs taken serially, thus yielding information on the change in the retinal disease over a period of several years. The reproducibility of placement of a microaneurysm on the same photograph by the same observer is equivalent to +/- 6.6 microns at the retina and inter-observer variation is equivalent to +/- 7.2 micron at the retina. Overall accuracy of placement of a point is 10 micron at the retina.

Diabetic retinopathy: II. Assessment of severity and progression from fluorescein angiograms.

A quantitative method for assessing the severity of retinopathy from fluorescein angiograms was applied to a group of patients starting continuous subcutaneous insulin infusion. There was a highly significant correlation between the area of nonperfusion as measured in the 20 degrees field centered on the right macula, and the mean retinopathy score derived by a standard method from a color retinal photographic survey. In those subjects who deteriorated more, there was an increase in the nonperfused areas, whereas the foveal avascular zone remained unchanged.

Hydroxyethylvaline adduct formation in haemoglobin as a biological monitor of cigarette smoke intake.

The ethylene oxide adduct formed on the N-terminal valine in haemoglobin was investigated as a biological monitor of tobacco smoke intake. The modified method developed for the determination of the hydroxyethylvaline adduct (HOEtVal) involved reaction of globin with pentafluorophenyl isothiocyanate, extraction of the HOEtVal thiohydantoin product, derivatization of this by trimethylsilylation and quantitation by capillary gas chromatography with selective ion monitoring mass spectrometry using a tetradeuterated internal standard. The method was applied to globin samples from 26 habitual cigarette smokers and 24 non-smokers. There was a significant correlation between cigarette smoke intake as measured by the average number of cigarettes smoked per day and HOEtVal levels (r = 0.537, p less than 0.01). Background levels were found in non-smokers (mean 49.9 pmol/g Hb, range 22-106 pmol/g Hb). Smoking increased these levels by 71 pmol/g Hb/10 cigarettes per day. Cotinine levels in plasma of the smokers were determined by GC-NPD using 2-methyl-4-nitroaniline as internal standard. For non-smokers cotinine was determined by GC-MS selective ion monitoring using d3-methylcotinine as internal standard. There was no correlation between number of cigarettes smoked per day and cotinine levels (r = 0.297, p greater than 0.05) although cotinine was correlated with HOEtVal (r = 0.43, p less than 0.01). The HOEtVal adduct levels thus appear to be a suitable biomonitor for exposure to hydroxyethylating agents in cigarette smoke, reflecting an integrated dose over the erythrocyte lifetime. This is in contrast to plasma cotinine determinations which reflect only the previous day's exposure to nicotine in smoke.