Calculation of beta-ray dose distributions from ophthalmic applicators and comparison with measurements in a model eye

Dose distributions throughout the eye, from three types of beta-ray ophthalmic applicators, were calculated using the EGS4, ACCEPT 3.0, and other Monte Carlo codes. The applicators were those for which doses were measured in a recent international intercomparison [Med. Phys. 28, 1373 (2001)], planar applicators of 106Ru-106Rh and 90Sr-90Y and a concave 106Ru-106Rh applicator. The main purpose was to compare the results of the various codes with average experimental values. For the planar applicators, calculated and measured doses on the source axis agreed within the experimental errors (<10%) to a depth of 7 mm for 106Ru-106Rh and 5 mm for 90Sr-90Y. At greater distances the measured values are larger than those calculated. For the concave 106Ru-106Rh applicator, there was poor agreement among available calculations and only those calculated by ACCEPT 3.0 agreed with measured values. In the past, attempts have been made to derive such dose distributions simply, by integrating the appropriate point-source dose function over the source. Here, we investigated the accuracy of this procedure for encapsulated sources, by comparing such results with values calculated by Monte Carlo. An attempt was made to allow for the effects of the silver source window but no corrections were made for scattering from the source backing. In these circumstances, at 6 mm depth, the difference in the results of the two calculations was 14%-18% for a planar 106Ru-l06Rh applicator and up to 30% for the concave applicator. It becomes worse at greater depths. These errors are probably caused mainly by differences between the spectrum of beta particles transmitted by the silver window and those transmitted by a thickness of water having the same attenuation properties.     

Levodopa, bromocriptine and selegiline modify cardiovascular responses in Parkinson's disease

Autonomic nervous system (ANS) involvement is frequently found in Parkinson's disease (PD), but its causal relationship to the disease itself and its medication is unclear. We evaluated the effects of PD medications on cardiovascular ANS functions. Heart rate (HR) responses to normal and deep breathing, the Valsalva manoeuvre and tilting, and blood pressure (BP) responses to tilting and isometric work were measured prospectively in 60 untreated PD patients randomised to receive either levodopa (n=20), bromocriptine (n=20) or selegiline (n=20) as their initial treatment. The results were compared with those of 28 healthy controls. The responses were recorded at baseline, after 6 months on medication and following a 6-week washout period. At baseline HR responses to normal breathing, deep breathing and tilting were already lower and the fall in the systolic BP immediately and at 5 min after tilting was more pronounced in the PD patients than in the controls. Six months' levodopa treatment diminished the systolic BP fall after tilting when compared to baseline, whereas bromocriptine and selegiline increased the fall in systolic BP after tilting and selegiline diminished the BP responses to isometric work. The BP responses returned to the baseline values during the washout period. The drugs induced no change in the HR responses. Thus PD itself causes autonomic dysfunction leading to abnormalities in HR and BP regulation and the PD medications seem to modify ANS responses further. Bromocriptine and selegiline, in contrast to levodopa, increase the orthostatic BP fall and supress the BP response to isometric exercise reflecting mainly impairment of the sympathetic regulation. Received: 17 February 2000 / Received in revised form: 25 May 2000 / Accepted: 15 June 2000     

Is there any link between insulin resistance and inflammation in established preeclampsia?

Both insulin resistance and inflammation may contribute to the onset of preeclampsia. They also could be interrelated. We studied the relationship between inflammatory cytokines and markers of insulin resistance. During their third trimester, 22 proteinuric preeclamptic women and 16 normotensive controls underwent intravenous glucose tolerance test (minimal model). Preeclamptic women were more insulin-resistant (P = .009), and they had higher levels of serum soluble tumor necrosis alpha receptor II (TNFalpha RII) (P = .002), triglycerides (P = .006), uric acid (P = .001), and leptin (P = .002) than did the controls. However, the study groups did not differ in serum TNFalpha, C-reactive protein (CRP), interleukin-6 (IL-6), sex hormone-binding globulin (SHBG), and high-density lipoprotein-2 (HDL(2))-cholesterol. In multiple regression analysis only SHBG (P = .01) and triglycerides (P = .0036) were associated with insulin sensitivity independently of body mass index (BMI), weight gain, HDL(2)-cholesterol, CRP, TNFalpha, and TNFalpha RII, IL-6, and leptin. We conclude that insulin resistance and the inflammatory markers studied were not associated in established preeclampsia.     

Seropositivity for Helicobacter pylori antibodies is associated with lower occurrence of venous bypass graft occlusion

Common chronic infections including those caused by cytomegalovirus (CMV), herpes simplex viruses (HSV), Helicobacter pylori and Chlamydia pneumoniae have previously been related to increased risk of coronary heart disease (CHD). We investigated the association between serology of these chronic infections and coronary bypass graft occlusions in 61 patients. As a result, IgG seropositivity rate against H. pylori was higher among patients without occlusion (82%) than in those with occlusion (45%) or apparently healthy controls (57%) (p = 0.004 and p = 0.008, respectively). In conclusion, H. pylori infection, as judged by IgG seropositivity, is associated with lower occurrence of venous bypass graft occlusion in patients with CHD and may thus be connected with better outcome and prognosis of CHD patients after bypass graft surgery.     

Postpartum bone mineral density in women treated for thromboprophylaxis with unfractionated heparin or LMW heparin

Venous thromboembolism remains an important cause of maternal mortality. In a randomised open study, 44 pregnant women with confirmed previous or current thromboembolism were randomised to receive either low-molecular-weight heparin, dalteparin (N = 21) once daily subcutaneously or unfractionated sodium heparin (UF heparin, N = 23) twice daily subcutaneously for thromboprophylaxis during pregnancy and puerperium. Bone mineral density (BMD) in the lumbosacral spine was measured with dual X-ray absorptiometry (DEXA) 1, 6, 16, 52 weeks and, if possible, 3 years after delivery. BMD values were also compared with those of healthy, delivered women (N = 19). Mean BMD of the lumbar spine was significantly lower in the unfractionated heparin group compared with the dalteparin and with the control groups (repeated measures ANOVA p = 0.02). BMD in the dalteparin group did not differ from BMD of healthy delivered women. Multiple logistic regression analysis revealed that therapy was the only independent factor influencing BMD at weeks 16 and 52. Therefore we recommend use of dalteparin instead of UF heparin for long-term thromboprophylaxis during and after pregnancy.     

Efficacy of nimodipine in the prophylaxis of migraine

The efficacy of nimodipine in the prophylaxis of migraine was assessed in a double-blind, placebo-controlled, cross-over study carried out on 33 patients, 20 of whom suffered from classic and 13 from common migraine. Four patients dropped out, but not as a result of the side effects of the drug. The duration of drug treatment was 8 weeks. The dosage used was 30 mg four times daily. Nimodipine proved to be better than placebo, the number of migraine attacks and severity of headache showing a significant reduction. The drug was well tolerated and no marked side effects were noted. The results suggest that nimodipine is a useful new prophylactic drug for migraine, but further studies are needed before its final value can be evaluated.     

Hepatic injury and drug metabolism in patients with alpha-methyldopa-induced liver damage

Summary The clinical picture and drug metabolism in 36 consecutive patients with alpha-methyldopa — induced hepatic injury were investigated. The diagnosis was based on case history and biochemical, histological and follow-up studies after withdrawal the drug. Alpha-methyldopa-induced liver damage was found to occur in two phases, acutely within months and chronically within years after beginning treatment. Differences were also found in clinical symptoms and the results of liver tests on the patients if they were divided on the basis of the time factor. Drug metabolism was impaired in patients with alpha-methyldopa-induced liver damage, as indicated by low cytochrome P-450 level in liver biopsies and prolonged antipyrine elimination rate from plasma. Disappearance of the symptoms and normalisation of the liver tests after drug withdrawal occurred faster in patients with an acute type of hepatotoxicity than in subjects with delayed onset of the symptoms. The occurrence of hepatotoxicity in four members of a family suggests a genetic disposition to alpha-methyldopa-induced hepatic injury. The occurrence of two phases of liver damage suggests that a possible mechanism for acute hepatotoxicity might be an allergic reaction to metabolic intermediates produced during breakdown of alpha-methyldopa in the liver. For cases of delayed onset the cause might be increasing damage to microsomal liver protein due to covalent binding during long-term exposure to the drug.