In vitro studies of DNA damage and repair mechanisms induced by BNCT in a poorly differentiated thyroid carcinoma cell line

Boron neutron capture therapy (BNCT) for aggressive tumors is based on nuclear reaction [¹⁰B (n, α) ⁷Li]. Previously, we demonstrated that BNCT could be applied for the treatment of undifferentiated thyroid carcinoma. The aim of the present study was to describe the DNA damage pattern and the repair pathways that are activated by BNCT in thyroid cells. We analyzed γH2AX foci and the expression of Ku70, Rad51 and Rad54, main effector enzymes of non-homologous end joining (NHEJ) and homologous recombination repair (HRR) pathways, respectively, in thyroid follicular carcinoma cells. The studied groups were: (1) C [no irradiation], (2) gamma [⁶⁰Co source], (3) N [neutron beam alone], (4) BNCT [neutron beam plus 10 µg ¹⁰B/ml of boronphenylalanine (¹⁰BPA)]. The total absorbed dose was always 3 Gy. The results showed that the number of nuclear γH2AX foci was higher in the gamma group than in the N and BNCT groups (30 min-24 h) (p < 0.001). However, the focus size was significantly larger in BNCT compared to other groups (p < 0.01). The analysis of repair enzymes showed a significant increase in Rad51 and Rad54 mRNA at 4 and 6 h, respectively; in both N and BNCT groups and the expression of Ku70 did not show significant differences between groups. These findings are consistent with an activation of HRR mechanism in thyroid cells. A melanoma cell line showed different DNA damage pattern and activation of both repair pathways. These results will allow us to evaluate different blocking points, to potentiate the damage induced by BNCT.

Improvement of the boron neutron capture therapy (BNCT) by the previous administration of the histone deacetylase inhibitor sodium butyrate for the treatment of thyroid carcinoma

We have shown that boron neutron capture therapy (BNCT) could be an alternative for the treatment of poorly differentiated thyroid carcinoma (PDTC). Histone deacetylase inhibitors (HDACI) like sodium butyrate (NaB) cause hyperacetylation of histone proteins and show capacity to increase the gamma irradiation effect. The purpose of these studies was to investigate the use of the NaB as a radiosensitizer of the BNCT for PDTC. Follicular thyroid carcinoma cells (WRO) and rat thyroid epithelial cells (FRTL-5) were incubated with 1 mM NaB and then treated with boronophenylalanine ¹⁰BPA (10 μg ¹⁰B ml⁻¹) + neutrons, or with 2, 4-bis (α,β-dihydroxyethyl)-deutero-porphyrin IX ¹⁰BOPP (10 μg ¹⁰B ml⁻¹) + neutrons, or with a neutron beam alone. The cells were irradiated in the thermal column facility of the RA-3 reactor (flux = (1.0 ± 0.1) × 10¹⁰ n cm⁻² s⁻¹). Cell survival decreased as a function of the physical absorbed dose in both cell lines. Moreover, the addition of NaB decreased cell survival (p < 0.05) in WRO cells incubated with both boron compounds. NaB increased the percentage of necrotic and apoptotic cells in both BNCT groups (p < 0.05). An accumulation of cells in G2/M phase at 24 h was observed for all the irradiated groups and the addition of NaB increased this percentage. Biodistribution studies of BPA (350 mg kg⁻¹ body weight) 24 h after NaB injection were performed. The in vivo studies showed that NaB treatment increases the amount of boron in the tumor at 2-h post-BPA injection (p < 0.01). We conclude that NaB could be used as a radiosensitizer for the treatment of thyroid carcinoma by BNCT.

New irradiation facility for biomedical applications at the RA-3 reactor thermal column

A new irradiation facility has been developed in the RA-3 reactor in order to perform trials for the treatment of liver metastases using boron neutron capture therapy (BNCT). RA-3 is a production research reactor that works continuously five days a week. It had a thermal column with a small cross section access tunnel that was not accessible during operation. The objective of the work was to perform the necessary modifications to obtain a facility for irradiating a portion of the human liver. This irradiation facility must be operated without disrupting the normal reactor schedule and requires a highly thermalized neutron spectrum, a thermal flux of around 10(10) n cm(-2)s(-1) that is as isotropic and uniform as possible, as well as on-line instrumentation. The main modifications consist of enlarging the access tunnel inside the thermal column to the suitable dimensions, reducing the gamma dose rate at the irradiation position, and constructing properly shielded entrance gates enabled by logical control to safely irradiate and withdraw samples with the reactor at full power. Activation foils and a neutron shielded graphite ionization chamber were used for a preliminary in-air characterization of the irradiation site. The constructed facility is very practical and easy to use. Operational authorization was obtained from radioprotection personnel after confirming radiation levels did not significantly increase after the modification. A highly thermalized and homogenous irradiation field was obtained. Measurements in the empty cavity showed a thermal flux near 10(10) n cm(-2)s(-1), a cadmium ratio of 4100 for gold foils and a gamma dose rate of approximately 5 Gy h(-1).

Prehospital use of paracetamol among children attending the accident and emergency department

OBJECTIVES

To identify patterns of prehospital administration of paracetamol to children who were perceived to be feverish by their carers.

METHODS

A prospective cohort study of carers of children attending a paediatric accident and emergency (A&E) department. Carers of children completed a questionnaire to identify domestic patterns of paracetamol use. Data were collected on temperature of the child in the A&E department, administration of antipyretics in the A&E department, diagnosis, and disposal from the A&E department.

RESULTS

Seventy five adults attending the A&E department consented to involvement. Sixty five of the children were feverish on arrival in the A&E department. Twenty one children (32.3%) had not received paracetamol before attending. There was a significant relation between knowledge of the antipyretic properties of paracetamol and administration (chi(2)=5.0, p<0.05). There was a significant correlation between fever and administration of paracetamol in the A&E department (chi(2)=23.7, p<0.01), however, 15 feverish patients (24.6%) were not treated.

CONCLUSIONS

Most carers administer paracetamol appropriately in the prehospital setting. Administration correlates significantly with knowledge of its benefits. There is scope for education of carers and A&E department staff in the in the appropriate use of antipyretics such as paracetamol.

Factors affecting the exchange of tocopherol between red blood cells and plasma

The purpose of this study was to clarify factors that affect the equilibrium distribution of alpha-tocopherol between red blood cells and plasma. Plasma labeled with 14C-alpha-tocopherol was incubated with red cells for 4 to 6 hr and the distribution of the tocopherol determined in the two compartments (red blood cell (RBC: plasma ratio). Use of heparin as anticoagulant gave a higher RBC: plasma ratio than acid citrate dextrose. The RBC:plasma ratio was affected by the hematocrit of the incubation mixture, higher ratios being obtained with lower hematocrits. The ratio was not related to the plasma concentration of alpha-toxopherol, indicating that the red cell was not saturated up to four times normal plasma levels. Of possible clinical significance was the finding that the RBC: plasma ratio was related to the total lipid concentration of plasma. Red cell content of alpha-tocopherol decreased as plasma lipids increased, until at three times normal plasma lipid concentration the red cells had one-third or less of their normal concentration of alpha-tocopherol. The implications of this observation on the relationship between plasma and tissue aplha-tocopherol are discussed.