Early and delayed reproductive death in human cells exposed to high energy iron ion beams.

The aim of this research was to determine the biological effectiveness for early and delayed effects of high energy, high linear energy transfer (LET) charged particles. Survival and delayed reproductive death were measured in AG1522 human fibroblast cells exposed to Fe-ion beams of energies between 0.2 and 1 GeV/n, 0.97 GeV/n Ti-ion and 0.49 GeV/n Si-ion beams. The cells were irradiated at the HIMAC accelerator in Chiba, Japan (0.2 and 0.5 GeV/n Fe and 0.49 GeV/n Si) and at the NASA Space Radiation Laboratory in Brookhaven, USA (1 GeV/n Fe and 0.97 GeV/n Ti ions). The dose-effect curves were measured in the dose range between 0.25 and 2 Gy. For comparison cells were exposed to 60Co gamma rays. Analysis of the dose-effect curves show that all the heavy ion beams induce inactivation and delayed reproductive death more effectively than 60Co gamma rays. The only exception is the 0.2 GeV/n Fe-ion beam at low doses. The progeny of the irradiated cells show delayed damage in the form of reproductive death with all the heavy ion beams with the 1 GeV/n Fe-ion beam being the most effective. The relative biological effectiveness at low doses of the iron beams is highest for LET values between 140 and 200 keV/micrometers with values of 1.6 and 3 for early and delayed reproductive death, respectively. Analysis of the fluence-effect curves shows that the cross-sections for early and delayed inactivation increase with increasing LET up to 442 keV/micrometers.

Differential effectiveness of solar UVB subcomponents in causing cell death, oncogenic transformation and micronucleus induction in human hybrid cells.

PURPOSE: (1). To determine the biological effectiveness of two solar ultraviolet (UVB) spectra with different lower wavelength thresholds for oncogenic transformation and micronucleus induction in CGL1 cells; (2). to investigate whether the action spectra for short- and long-term effects are similar; and (3). to investigate possible links between transformation and other delayed effects. MATERIALS AND METHODS: Two spectra were derived from a solar UV simulator by using two filters: the first transmitted radiation with lambda > 284 nm, the second with lambda > 293 nm. The resulting spectra have the same UVA, but different UVB components (lambda between 284 and 320 nm, 19 W m(-2), and lambda between 293 and 320 nm, 13 W m(-2)). CGL1 cells were irradiated with 466 J m(-2) with lambda > 284 nm and 1582 J m(-2) with lambda > 293 nm. These doses were approximately equilethal. The endpoints examined were oncogenic transformation, and centromere-positive and -negative micronucleus frequencies in the directly irradiated cells and in transtheir progeny. RESULTS: At equilethal doses, the oncogenic transformation frequency in the directly irradiated cells was greater by a factor of at least 7 for lambda > 284 nm irradiation compared with lambda > 293 nm. The micronucleus induction frequency was also significantly higher with the lambda > 284 spectrum. Consistent with our previous findings, no delayed micronucleus formation was found in the progeny of cells exposed to lambda > 293 nm, while a threefold elevation above controls was seen in the progeny of cells exposed to lambda > 284 nm irradiation. This was also the case for formation of micronuclei with a centromere. CONCLUSIONS: It was found that: (1). for equilethal doses the lambda > 284 nm spectrum was more biologically effective than the lambda > 293 nm spectrum for induction of oncogenic transformation and micronucleus formation; and (2). the higher effectiveness of the lambda > 284 nm spectrum found at equilethal doses for delayed effects in the progeny of irradiated cells resembles that found for transformation. The results suggest that the UVB action spectrum for cell killing is different from that of some delayed effects, and from that of transformation.

Inactivation cross sections for mammalian cells exposed to charged particles: a phenomenological approach.

Published data on inactivation of V79 cells irradiated with monoenergetic proton and ion beams (He, C, O, Ne) have been analysed. Values for RBE alpha, RBE10% and the inactivation cross section sigma have been evaluated in the LET range between 5 and 400 keV.micron-1. RBE against LET curves and inactivation cross sections against LET and against Z*2/beta 2 curves have been studied in a comparative approach with respect to the different ion types. RBE-LET curves depend strongly on the type of ion for LET > 30 keV.micron-1. At LET < 30 keV.micron-1 and low doses protons show the greatest effectiveness; at LET > 30 keV.micron-1 and high doses He ions provide the most effective radiation. Apart from protons, separation among the various ion curves is less marked in the sigma against Z*2/beta 2 plot than in the sigma against LET plot. sigma against Z*2/beta 2 curves for ions with 2 < or = Z < or = 10 and 200 < Z*2/beta 2 < 1500 show a common trend independent of Z and are well represented by a linear relationship.

Solar UV radiation: differential effectiveness of UVB subcomponents in causing cell death, micronucleus induction and delayed expression of heritable damage in human hybrid cells.

PURPOSE: To determine the effectiveness of two UV spectra with different UVB components for cell kill and micronucleus induction in irradiated human HeLaxskin fibroblast (CGL1) hybrid cells and their progeny. To determine the presence of reactive oxygen species (ROS) in the progeny of the irradiated cells at various post-irradiation times and their relationship with induced delayed biological effects. MATERIAL AND METHODS: A commercial solar ultraviolet simulator was used. Two different filters were employed: the first transmitted radiation with lambda>284nm and the second radiation with lambda>293nm. The resulting spectra have different UVB components (lambda between 284 and 320nm, 19 W/m(2), and between 293 and 320nm, 13 W/m(2)) and the same UVA component (lambda between 320 and 400nm, 135 W/m(2)). CGL1 cells were irradiated with various doses. Clonogenic survival and micronucleus formation were scored in the irradiated cells and their progeny. ROS were detected by incubation of cultures at various post-irradiation times with dichlorodihydrofluorescein diacetate followed by flow cytometric measurement of the final product, dichlorofluorescein. RESULTS: The biological effectiveness of the lambda>284nm spectrum was higher by a factor of 3 compared to the lambda>293nm spectrum for cell kill, and by a factor of 5 for micronucleus induction. No delayed cell death or micronucleus formation was found in the progeny of cells exposed to lambda>293nm, while a large and dose-dependent effect was found in the progeny of cells exposed to lambda>284nm for both of these endpoints. ROS levels above those in unirradiated controls were found only in the progeny of cells exposed to the lambda>284nm spectrum. CONCLUSIONS: The spectrum with lambda>284nm was more effective than that with lambda>293nm for induction of cell kill and micronucleus formation in the directly irradiated cells as well as induction of delayed effects in the progeny in the form of delayed reproductive death and micronucleus formation. The presence of ROS in the progeny of the irradiated cells may be the cause of the delayed effects.

Inactivation of human cells exposed to fractionated doses of low energy protons: relationship between cell sensitivity and recovery efficiency.

Within the framework of radiation biophysics research in the hadrontherapy field, split-dose studies have been performed on four human cell lines with different radiation sensitivity (SCC25, HF19, H184B5 F5-1 M10, and SQ20B). Low energy protons of about 8 and 20 keV/micron LET and gamma-rays were used to study the relationship between the recovery ratio and the radiation quality. Each cell line was irradiated with two dose values corresponding to survival levels of about 5% and 1%. The same total dose was also delivered in two equal fractions separated by 1.5, 3, and 4.5 hours. A higher maximum recovery ratio was observed for radiosensitive cell lines as compared to radioresistant cells. The recovery potential after split doses was small for slow protons, compared to low-LET radiation. These data show that radiosensitivity may not be related to a deficient recovery, and suggest a possible involvement of inducible repair mechanisms.

Radiobiological studies on the 65 MeV therapeutic proton beam at Nice using human tumour cells.

PURPOSE: To determine the relative biological effectiveness (RBE) for initial and delayed inactivation of cells by a modulated proton beam suitable for the treatment of tumours of the eye, within the spread-out Bragg peak and in its distal declining edge. MATERIALS AND METHODS: Human tumour SCC25 cells were irradiated with the 65 MeV proton beam at the Cyclotron Medicyc in Nice. Perspex plates of different thickness were used to simulate five positions along the beam line: 2mm corresponding to the entrance beam; 15.6 and 25 mm in the spread-out Bragg peak; 27.2 and 27.8mm for the distal edge. At each position clonogenic survival of the irradiated cells and of their progeny were determined at various dose values. 60Co gamma-rays were used as reference radiation. RESULTS: RBE values evaluated at the survival level given by 2 Gy of gamma-rays increased with increasing depth from close to 1.0 at the proximal to about 1.2 at the distal part of the peak. Within the declining edge it reached the value of about 1.4 at 27.2 and about 2 at 27.8 mm. For the progeny of irradiated cells, the RBE value ranged from 1.0 to 1.1 within the spread-out Bragg peak and then increased up to a value of 2.0 at the last position. The dose-effect curves for the progeny always had a larger shoulder than for the irradiated progenitors, their alpha parameters being lower by a factor of about 4 and their beta parameters always being higher. The alpha/beta ratio was about 50 Gy for the progenitors and about 6 Gy for their progeny. The incidence of delayed effects increased with dose and with the depth within the beam. CONCLUSIONS: RBE values for the inactivation of cells irradiated in the spread-out Bragg peak are compatible with the value currently assumed in clinical applications. In the distal declining edge of the beam, the RBE values increased significantly to an extent that may be of concern when the region of the treatment volume is close to sensitive tissues. The yield of delayed reproductive cell death was significant at each position along the beam line.

Inactivation of human normal and tumour cells irradiated with low energy protons.

PURPOSE: To analyse the cell inactivation frequencies induced by low energy protons in human cells with different sensitivity to photon radiation. MATERIALS AND METHODS: Four human cell lines with various sensitivities to photon irradiation were used: the SCC25 and SQ20B derived from human epithelium tumours of the tongue and larynx, respectively, and the normal lines M/10, derived from human mammary epithelium, and HF19 derived from a lung fibroblast. The cells were irradiated with y-rays and proton beams with linear energy transfer (LET) from 7 to 33 keV/microm. Clonogenic survival was assessed. RESULTS: Survival curves are reported for each cell line following irradiation with gamma-rays and with various proton LETs. The surviving fraction after 2 Gy of gamma-rays was 0.72 for SQ20B cells, and 0.28-0.35 for the other cell lines. The maximum LET proton effectiveness was generally greater than that of gamma-rays. In particular there was a marked increase in beam effectiveness with increasing LET for the most resistant cells (SQ20B) whose 2 Gy-survival varied from 0.72 with gamma-radiation down to 0.37 with 30 keV/microm protons. The relative biological effectiveness (RBE(2 Gy gamma)) with the 30 keV/microm beam, evaluated as the ratio of 2 Gy to the proton dose producing the same inactivation level as that given by 2 Gy of gamma-rays, was 3.2, 1.8, 1.3 and 0.8 for SQ20B, M/10, SCC25, and HF19, respectively. CONCLUSIONS: RBE for inactivation with high-LET protons increased with the cellular radioresistance to gamma-rays. The cell line with the greatest resistance to gamma-rays was the most responsive to the highest LET proton beam. A similar trend has also been found in studies reported in the literature with He, C, N ions with LET in the range 20-125 keV/microm on human tumour cell lines.

Effect of tamoxifen on lipoprotein(a) and insulin-like growth factor-I (IGF-I) in healthy women.

Studies in breast cancer patients have shown that tamoxifen decreases circulating levels of lipoprotein(a) (Lp(a)), an independent risk factor for premature coronary heart disease, and insulin-like growth factor-I (IGF-I), a promising surrogate biomarker for breast cancer. Since a common hormone regulatory pathway has been suggested for both biomarkers, we measured Lp(a) levels for 6 months in 68 healthy women participating in a chemoprevention trial of tamoxifen and correlated its changes with IGF-I. After 1 month, mean Lp(a) levels decreased by 23% with tamoxifen and increased by 6% with placebo (P = 0.033). No further change was observed after 2 and 6 months. Women with abnormal values at baseline (i.e. > 30 mg/dl) showed the highest reduction. The mean levels of IGF-I decreased by 23.5% with tamoxifen and remained stable with placebo, but the changes induced by tamoxifen in Lp(a) and IGF-I levels were uncorrelated. Our results support the observation that tamoxifen may be a suitable preventive option for women with multiple disease risk factors.

Biologic activity of tamoxifen at low doses in healthy women.

BACKGROUND: Results of a clinical trial recently completed in the United States indicate that administration of tamoxifen (20 mg/day) to women at risk can reduce breast cancer incidence by approximately 50% but is associated with an increased risk of developing endometrial cancer and venous thromboembolic events. Since these adverse effects may be dose related, we investigated the effect of tamoxifen on several biomarkers when the drug was given at doses lower than those currently in use. METHODS: In two sequential experiments, 127 healthy hysterectomized women aged 35-70 years were randomly assigned to one of the following four treatment arms: placebo (n = 31) or tamoxifen at 20 mg/day (n = 30) (first experiment); or tamoxifen at 10 mg/day (n = 34) or tamoxifen at 10 mg/ alternate days (n = 32) (second experiment). Baseline and 2-month measurements of the following parameters were compared: 1) total cholesterol (primary end point) and other surrogate markers of cardiovascular disease, e.g., low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides, and lipoprotein(a); 2) blood cell count; 3) fibrinogen; 4) antithrombin III; 5) osteocalcin; and, 6) in a subgroup of 103 women, insulin-like growth factor-I (IGF-I), a possible surrogate marker for breast cancer. RESULTS: After adjustment for the baseline values, there were reductions in circulating levels of total cholesterol and IGF-I of the same magnitude in all three tamoxifen treatment arms. A similar pattern was observed for most of the other parameters. In the placebo arm, fibrinogen level, which showed a decrease, was the only parameter exhibiting change. CONCLUSIONS: Up to a 75% reduction in the conventional dose of tamoxifen (i.e., 20 mg/day) does not affect the activity of the drug on a large number of biomarkers, most of which are surrogate markers of cardiovascular disease. This study was hypothesis generating, and larger studies are warranted to assess the efficacy of tamoxifen at low doses.

Technical report: Cell thickness measurements by confocal fluorescence microscopy on C3H10T1/2 and V79 cells.

Measurements of C3H10T1/2 and V79 cell thickness were performed on living cells by confocal laser fluorescence microscopy. Thickness distributions are reported for cells growing as a monolayer (on mylar and glass) and suspended in their medium. Mean values for cells grown on mylar (corrected for refractive index effects) are 2.9 +/- 0.6 and 6.1 +/- 1.0 microm for C3H10T1/2 and V79 cells respectively. Mean values of the diameters of cells suspended in their medium are 13.0 +/- 1.6 and 9.3 +/- 1.4 microm for C3H10T1/2 and V79 respectively. Knowledge of cell thickness, as irradiated, is of central relevance for studying the relative biological effectiveness of low energy, poorly penetrating radiations. It can be concluded, from the measured cell thickness distributions, that with C3H10T1/2 cells grown on mylar, the LET variation through the whole cell is within 20% for protons and alpha-particles with energies down to 0.6 and 2.5 MeV respectively. From a comparison with thickness values reported in the literature for living or fixed embedded cells growing on plastic substrate, mean values between 2.4 and 3.4 microm and between 6 and 7.5 microm could be assumed for C3H10T1/2 cells and for the most widely used V79 cell lines respectively.

Transformation of C3H 10T1/2 cells by low doses of ionising radiation: a collaborative study by six European laboratories strongly supporting a linear dose-response relationship.

For the assessment of radiation risk at low doses, it is presumed that the shape of the low-dose-response curve in humans for cancer induction is linear. Epidemiological data alone are unlikely to ever have the statistical power needed to confirm this assumption. Another approach is to use oncogenic transformation in vitro as a surrogate for carcinogenesis in vivo. In mid-1990, six European laboratories initiated such an approach using C3H 10T1/2 mouse cells. Rigid standardisation procedures were established followed by collaborative measurements of transformation down to absorbed doses of 0.25 Gy of x-radiation resulting in a total of 759 transformed foci. The results clearly support a linear dose-response relationship for cell transformation in vitro with no evidence for a threshold dose or for an enhanced, supralinear response at doses approximately 200-300 mGy. For radiological protection this represents a large dose, and the limitations of this approach are apparent. Only by understanding the fundamental mechanisms involved in radiation carcinogenesis will further knowledge concerning the effects of low doses become available. These results will, however, help validate new biologically based models of radiation cancer risk thus providing increased confidence in the estimation of cancer risk at low doses.

Tamoxifen reduces plasma homocysteine levels in healthy women.

Treatment with tamoxifen is associated with reduced incidence of myocardial infarction. As plasma homocysteine is an independent risk factor for cardiovascular disease, we studied the effects of tamoxifen on plasma homocysteine in 66 healthy women participating in the Italian prevention trial of breast cancer who were randomized in a double-blind manner to tamoxifen 20 mg day(-1) or placebo for 5 years. They were aged between 35 and 70 years, had undergone previous hysterectomy for non-malignant conditions and had no contraindications to the use of tamoxifen. Plasma levels of total homocysteine (tHcy) were measured at randomization and after 2 and 6 months. The mean +/- s.d. plasma levels of tHcy were 7.59 +/- 1.71 micromol l(-1), 7.25 +/- 1.61 and 7.09 +/- 1.33 in the tamoxifen group and 8.07 +/- 2.06, 7.93 +/- 1.77 and 8.12 +/- 2.04 in the placebo group at 0, 2 and 6 months (P = 0.008 for the between-group difference over time). The higher the baseline tHcy level, the greater was the lowering effect of tamoxifen. No statistically significant effect of age, body mass index or smoking habit on baseline tHcy levels and its variation over time was found. In conclusion, tamoxifen (20 mg day(-1) for 6 months) decreased plasma tHcy levels in healthy women. This effect may contribute to its protective effect on myocardial infarction.

Inactivation of C3H10T1/2 cells by low energy protons and deuterons.

PURPOSE: To determine the RBE-LET relationship for C3H10T1/2 cell inactivation by protons in the LET range 11-33 keV/microm and to compare inactivation frequencies induced in C3H10T1/2 cells by protons and deuterons at two matching LET values in the range 11-20 keV/microm. MATERIALS AND METHODS: C3H10T1/2 cells were irradiated with protons and deuterons at the radiobiological facility set up at the 7MV Van de Graaff accelerator at the LNL, Legnaro, Padova. Gamma rays from 60Co were used as reference radiation. RESULTS: Proton RBE values (alpha/alphagamma) for inactivation of C3H10T1/2 cells are constant around a value of 2 between 11 and 20 keV/microm and then rise sharply to reach a value of 4.2+/-1.0 at 33 keV/microm. Deuteron RBE values are 1.7+/-0.4 and 2.2+/-0.6 at LET values of 13 and 18 keV/microm respectively. CONCLUSIONS: Proton RBE values with C3H10T1/2 cells are significantly larger than unity at LET values as low as 11 keV/microm. No difference in effectiveness for inactivation of C3H10T1/2 has been found between protons and deuterons at two LET values in the range 10-20 keV/microm.

Alpha-particle-induced neoplastic transformation in synchronized hybrid cells of HeLa and human skin fibroblasts.

Survival and oncogenic transformation frequencies were determined through the cell cycle in hybrid cells (HeLa x human skin fibroblasts), exposed to 0.30 and 0.15 Gy 4.3 MeV (LET= 101 keV/microm) alpha-particles. The cells were synchronized by mitotic collection and irradiated at times ranging from 2 to 10 h after collection, corresponding to G1 and early S. At 0.30 Gy the highest value in the transformation frequency (1.6 +/- 0.3) x 10(-4) transformants/survivor, occurred 4 h after mitotic collection, corresponding to mid-G1 and was about twice as high as that for the asynchronous population (0.7 +/- 0.1) x 10(-4) transformants/survivor. A similar pattern was seen at 0.15 Gy albeit less marked. The results are similar to previous findings with C3H10T1/2 exposed to 0.30 Gy where (1.8 +/- 0.4) x 10(-4) and (0.8 +/- 0.4) x 10(-4) transformants/survivor were found in mid-G1 and in the asynchronous population respectively. The results of both these studies with 101 keV/microm alpha particles indicate that mid-G1 cells may be more sensitive than asynchronous cells by up to a factor of two. However, it is unlikely that such a factor is sufficient to represent the cell cycle 'hot spot' for transformation postulated to explain the inverse dose-rate effect.

Exercise training in mild hypertension: effects on blood pressure, left ventricular mass and coagulation factor VII and fibrinogen.

The aim of this study was to assess the effects of aerobic exercise on resting and 24-hour blood pressure (BP), left ventricular mass (LVM), plasma fibrinogen and factor VII (FVII). For this purpose 14 sedentary subjects with untreated diastolic BP between 90 and 104 mm Hg completed a 12-week supervised exercise program. At the end of this period, 8 subjects resumed a sedentary life-style and were reexamined 2 months later (detraining). Baseline, posttraining and postdetraining examinations included resting BP assessment, ambulatory BP monitoring, cardiopulmonary stress test, echocardiography and measurements of plasma fibrinogen and FVII. Exercise-mediated increase in aerobic fitness (VO2 max + 24%) was associated with a significant reduction in resting systolic and diastolic BP (p < 0.01), mean systolic and diastolic 24-hour BP (p < 0.001) and LVM index. As for the coagulation parameters only the concentration of fibrinogen significantly decreased (p < 0.01) whereas FVII remained unchanged. The 8 subjects that resumed a sedentary life-style were reexamined 2 months later: their resting BP, 24-hour BP and fibrinogen concentration returned to baseline values; only the effect on LVM was conserved. Our study underlines the usefulness and safety of regular physical exercise in mild hypertension. Most of the patients (11 of 14) had their BP normalized and a significant reduction in LVM and fibrinogen concentration was observed, leading to an overall improvement in coronary risk profile.

Effect of tamoxifen on measurements of hemostasis in healthy women.

BACKGROUND: Tamoxifen citrate is being evaluated for primary prevention of breast cancer, but this drug with estrogen-like properties may cause changes in the hemostatic system that would increase the risk of thrombosis. METHODS: Women who had undergone hysterectomy were consecutively enrolled in the placebo-controlled, randomized, double-blind Breast Carcinoma Chemoprevention Tamoxifen Study, which was designed to evaluate the efficacy of oral tamoxifen citrate (20 mg/d). Our substudy of hemostasis and lipid measurements included the first 68 consecutive women assigned to tamoxifen (n = 31) or placebo (n = 37). Blood specimens were obtained before treatment and after 1,2,4, and 6 months of treatment. Measurements included blood cell counts, lipid levels, coagulation activation markers, clotting factors, and anticoagulant and fibrinolysis proteins. RESULTS: Hematocrit and hemoglobin and platelet levels fell slightly but significantly in women treated with tamoxifen. No between-treatment differences were observed in any of the clotting factors. Naturally occurring anticoagulant proteins such as antithrombin and protein C fell slightly in women treated with tamoxifen. However, no significant changes were observed in any of the markers of activated coagulation or fibrinolysis (fibrinopeptide A, prothrombin fragment 1 + 2, thrombin-antithrombin complex, D-dimer). Total and low-density lipoprotein cholesterol levels fell significantly in women treated with tamoxifen. CONCLUSIONS: Tamoxifen induced a modest decrease in anticoagulant proteins, but without biochemical signs of activation of coagulation and fibrinolysis. Tamoxifen improved the lipid profile and induced changes in blood cell counts, which should determine an improvement in blood rheologic factors. These preliminary findings seem to justify continuation of the double-blind study in healthy women, but only direct comparison of thromboembolic complications in the 2 treatment groups will establish whether tamoxifen carries a risk of thrombosis.

[Physical training exercise reduces the plasma levels of fibrinogen in subjects with mild hypertension]. / L'esercizio fisico allenante riduce i livelli plasmatici di fibrinogeno in soggetti con ipertensione lieve.

We evaluated the behaviour of plasma fibrinogen in subjects undergoing physical training in a prospective non-controlled open study, carried out in 14 sedentary, mildly hypertensive individuals (mean age 52 +/- 5 years). Subjects underwent 3 months of controlled physical training (3 times a week) tailored to reach, at each session, 80-90% of maximal heart rate based upon a baseline test. Before and after the period of training, resting systolic and diastolic blood pressure, 24-hour systolic and diastolic blood pressure, plasma fibrinogen, body mass index (BMI), maximum oxygen consumption (VO2max), serum cholesterol and triglycerides were evaluated. After training VO2 max increased (24 +/- 5 vs 30 +/- 5 mL/Kg/min, p < 0.01); there were no variations in BMI (24 +/- 2 vs 23 +/- 2 Kg/m2, p = 0.35), cholesterol (220 +/- 30 vs 213 +/- 36 mg/dL, p = 0.41) or triglycerides (117 +/- 51 vs 118 +/- 37 mg/dL, p = 0.58). Resting systolic (148 +/- 10 vs 133 +/- 10 mmHg, p < 0.01) and diastolic blood pressure (97 +/- 5 vs 85 +/- 6 mmHg, p < 0.01) and 24-hour systolic (135 +/- 6 vs 129 +/- 5 mmHg, p < 0.01) and diastolic blood pressure (86 +/- 7 vs 81 +/- 6 mmHg, p < 0.01) decreased; plasma fibrinogen also decreased (324 +/- 60 vs 278 +/- 53 mg/dL, p < 0.01). Eight individuals tested 5 months after cessation of training, showed a return of fibrinogen, blood pressure and VO2 max to baseline values.(ABSTRACT TRUNCATED AT 250 WORDS)

Oncogenic transformation of C3H 10T1/2 cells exposed to alpha particles: sensitivity through the cell cycle.

Oncogenic transformation of synchronized C3H 10T1/2 cells was determined after exposure to 4.3 MeV alpha particles (LET = 101 keV/microns). Two synchronization techniques were tested using basic and modified protocols: one based on the release of cells from contact inhibition and the second on the mitotic shake-off method. Progression of cells through the cycle was followed as a function of time by flow cytometric analysis, DNA labeling for passage through S phase, the growth curve for the cell number and mitotic index measurements. The conclusion is that, although the release of cells from confluence provides higher yields of synchronized cells, mitotic shake-off proved to be the best way of collecting a synchronized population of minimally perturbed cells. Cells synchronized by mitotic shake-off were irradiated with 0.30 Gy in the interval between 2 and 10 h corresponding to G1 and early S phases. For comparison asynchronous populations were irradiated in parallel. Oncogenic transformation frequency, corrected for background, in mid-G1 phase was (18 +/- 4) x 10(-5) (average values of frequencies at 4 and 6 h) compared with the value of (8 +/- 4) x 10(-5) for the asynchronous population. While these data are suggestive of a trend toward a slightly increased sensitivity in mid-G1 phase, it is not statistically significant. The surviving fraction is constant in G1 phase.

Radiation-induced chromosomal aberrations in mouse 10T1/2 cells: dependence on the cell-cycle stage at the time of irradiation.

Cell-cycle stage radiosensitivity for the induction of chromosome aberrations has been investigated in C3H 10T1/2 cells. Exponentially growing cells were irradiated with 3 Gy X-rays (80 kVp) or 0.6 Gy alpha-particles (LET = 101 keV/micron). The two doses produce the same survival level (37%) in the asynchronous population. Cells were harvested at four different times following irradiation and cell-cycle phase at the time of irradiation was assessed by using the differential replication staining technique. The frequency of chromosome aberrations produced in a given stage of the cell cycle was not constant as a function of the sampling time, but this could not be simply related to the existence of subphases exhibiting different radiosensitivity, because of cell-cycle perturbation introduced by radiation. X-radiation induced more exchanges than deletions, whereas a predominance of isochromatid deletions was observed after alpha-irradiation. This can be interpreted on the basis of the different patterns of energy deposition of densely- and sparsely-ionizing radiation. Both X- and alpha-rays produced a significant increase in the frequency of Robertsonian translocations when cells were exposed in G1 or S phase, but not in G2 phase.

Are capillary whole blood coagulation monitors suitable for the control of oral anticoagulant treatment by the international normalized ratio?

The 512 Coagulation Monitor is a portable coagulation photometer that uses disposable cartridges containing a lyophilized rabbit brain thromboplastin to measure the PT for capillary whole blood. It has been proposed as a suitable system for patient self monitoring at home, but its performance has never been thoroughly assessed for results expressed as International Normalized Ratio (INR). In particular, there is no available information about the adequacy of the WHO calibration model with the Monitor. The aims of the study were to determine the International Sensitivity Index (ISI) against the secondary International Reference Preparation for rabbit thromboplastin and to assess the precision of the INR. The study demonstrates that the Monitor can be calibrated with the WHO model, because log-transformed PTs for patients stabilized on oral anticoagulants and normal individuals are linearly related and because the same orthogonal regression line describes patient and normal data points adequately. However, the ISI calculated in this study (2.715) is higher than that adopted by the manufacturer (2.036). The between-assay reproducibility of the Monitor is acceptable (CV = 9.7%) with results expressed in seconds, but become unacceptably poor when the results are converted into INR (CV = 18.8%) because of the high ISI value of the thromboplastin used. We think that the Monitor might be suitable for monitoring oral anticoagulant therapy if the manufacturer would provide a more sensitive thromboplastin in the cartridges.