Measurement of stopping power ratios for 60 MeV positive or negative pions.

Pion stopping power ratios are essential parameters for pion radiotherapy treatment planning. The validity of scaling proton stopping powers to pions is called into question since the pion mass is intermediate between the electron and proton masses. Direct measurements of stopping power ratios with respect to water were made for 60 MeV pions of both charges in Teflon, Plexiglas, nylon, paraffin, gelatine, tissue-equivalent plastic (Shonka A150), graphite, aluminium, steel and copper. Corrections for multiple scattering and energy dependence of the stopping power are applied. Measured stopping power ratios at an accuracy of 0.6% are in agreement to within the limits of experimental error with stopping power ratios calculated from the Bethe-Bloch equation using elemental I-values and Bragg additivity.     

Metacarpal morphometry in monozygotic and dizygotic elderly twins

Summary The relative importance of genetic factors in the pathogenesis of age related bone loss has been investigated in a study involving 17 monozygotic (MZ) and 8 dizygotic (DZ) pairs of twins aged 64 to 75 years. Radiographic morphometry was performed at the midpoints of the 2nd, 3rd and 4th metacarpals of both hands and the mean total and cortical widths were evaluated. The heritability, h², was calculated as the difference between the intrapair variances in same sexed DZ and MZ pairs divided by the intrapair variance in DZ pairs. The mean intrapair variance of both total and cortical width was found to be four to five times higher in DZ than in MZ pairs. The differences are highly significant with an h² value between 0.7 and 0.8, indicating a predominant genetic influence. It is stressed that this result applies only to the population from which the twin sample was drawn.     

Cross-over study of fat-corrected forearm mineral content during nandrolone decanoate therapy for osteoporosis

We have previously reported an increase in forearm bone mineral content (BMC) during therapy for osteoporosis with the anabolic steroid, nandrolone decanoate. However, it has recently been claimed that part of this increase is spurious, due to a decrease in forearm fat during the treatment. We have therefore analyzed the data from a cross-over study of the effects of this agent on 70 osteoporotic women, using the fat correction procedure supplied by the manufacturer of the forearm densitometer. There was a significant rise (p less than 0.001) in the mean fat-corrected BMC (BMC[fc]) on nandrolone decanoate (50 mg intramuscularly every 2 or 3 weeks) and a non-significant fall in mean BMC[fc] off the drug. The mean time-weighted rate of change in the fat-corrected value was +29 +/- 5 mg/cm/year on nandrolone decanoate and -5 +/- 5 mg/cm/year off nandrolone decanoate (p less than 0.001). Nandrolone decanoate produces a significant gain in forearm mineral content even after allowing for changes in forearm fat content during therapy.     

Effects of exposure period of acetylsalicylic acid, paracetamol and isopropanol on L929 cytotoxicity

An established fibroblast cell line, L929, was exposed to three substances—acetylsalicylic acid, isopropanol and paracetamol—for 24 hr, 72 hr or 13 days. The effective concentration that caused 50% inhibition of cell growth (EC₅₀) was calculated for both the 24- and 72-hr exposures using three assays—total protein (TP), neutral red uptake (NR) and enzymatic conversion of MTT to formazan. The methods determining the viability of the cells were more sensitive than measurement of total protein. Cells exposed for 13 days continued to proliferate during the entire period, although at a reduced rate, and never attained the density of the control. The relative toxic effect of the substances varied considerably as a consequence of the duration of the exposure period.     

Stereoselective efflux of (E)-10-hydroxynortriptyline enantiomers from the cerebrospinal fluid of depressed patients.

In 5 patients treated with nortriptyline or amitriptyline for at least 9 months, the cerebrospinal fluid (CSF)/plasma ratio for 10-hydroxynortriptyline (10-OH-NT) ranged from 0.085 to 0.172, which is similar to the ratio previously measured in patients treated for 3 weeks. In 4 other patients treated with racemic (E)-10-OH-NT, the mean concentration ratio between (-)- and (+)-(E)-10-OH-NT was 3.56 in plasma, 2.39 in plasma ultrafiltrate and 1.42 in CSF (one-way ANOVA; P less than 0.001). The mean free fraction in plasma determined by ultrafiltration for (-)-(E)-10-OH-NT was 28.9 +/- S.D.1.1% and for the (+)-enantiomer 43.7 +/- 0.8% (P less than 0.001) confirming the difference in protein binding shown previously in healthy subjects. There was a correlation between the concentration of 10-OH-NT (sum of enantiomers) in CSF and plasma ultrafiltrate (r = 0.96; n = 7; P less than 0.001). The concentration in CSF was, however, only about 50% of that in the plasma ultrafiltrate and this seems to be due to a stereoselective transport of (E)-10-OH-NT out from the CSF. The secretion from the CSF is more pronounced for the (-)-compared to the (+)-enantiomer, which is consistent with the stereoselectivity of the renal secretion of these compounds.