Temozolomide-mediated radiation enhancement in glioblastoma: a report on underlying mechanisms.

PURPOSE: In this study, we investigated the mechanisms by which temozolomide enhances radiation response in glioblastoma cells. EXPERIMENTAL DESIGN: Using a panel of four primary human glioblastoma cell lines with heterogeneous O(6)-methylguanine-DNA methyltransferase (MGMT) protein expression, normal human astrocytes, and U87 xenografts, we investigated (a) the relationship of MGMT status with efficacy of temozolomide-based chemoradiation using a panel of in vitro and in vivo assays; (b) underlying mechanisms by which temozolomide enhances radiation effect in glioblastoma cells; and (c) strategies to overcome resistance to radiation + temozolomide. RESULTS: Temozolomide enhances radiation response most effectively in glioblastomas without detectable MGMT expression. On concurrent radiation + temozolomide administration in MGMT-negative glioblastomas, there seems to be decreased double-strand DNA (dsDNA) repair capacity and enhanced dsDNA damage compared either with radiation alone or with sequentially administered temozolomide. Our data suggest that O(6)-benzylguanine can enhance the antitumor effects of concurrent radiation + temozolomide in MGMT-positive cells by enhancing apoptosis and the degree of dsDNA damage. O(6)-Benzylguanine was most effective when administered concurrently with radiation + temozolomide and had less of an effect when administered with temozolomide in the absence of radiation or when administered sequentially with radiation. Our in vivo data using U87 xenografts confirmed our in vitro findings. CONCLUSIONS: The present study shows that temozolomide enhances radiation response most effectively in MGMT-negative glioblastomas by increasing the degree of radiation-induced double-strand DNA damage. In MGMT-positive glioblastomas, depletion of MGMT by the addition of O(6)-benzylguanine significantly enhances the antitumor effect of concurrent radiation + temozolomide. These are among the first data showing mechanisms of synergy between radiation and temozolomide and the effect of MGMT.

Fluorodeoxyuridine mediated cell cycle synchronization in S-phase increases the Auger radiation cell killing with 125I-iododeoxyuridine.

Aim: 125I-iododeoxyuridine is a potential Auger radiation therapy agent. Its incorporation in DNA of proliferating cells is enhanced by fluorodeoxyuridine. Here, we evaluated therapeutic activities of 125I-iododeoxyuridine in an optimized fluorodeoxyuridine pre-treatment inducing S-phase synchronization. Methods: After S-phase synchronization by fluorodeoxyuridine, cells were treated with 125I-iododeoxyuridine. Apoptosis analysis and S-phase synchronization were studied by flow cytometry. Cell survival was determined by colony-forming assay. Based on measured growth parameters, the number of decays per cell that induced killing was extrapolated. Results: Treatment experiments showed that 72 to 91% of synchronized cells were killed after 0.8 and 8 kBq/ml 125I-iododeoxyuridine incubation, respectively. In controls, only 8 to 38% of cells were killed by corresponding 125I-iododeoxyuridine activities alone and even increasing the activity to 80 kBq/ml gave only 42 % killing. Duplicated treatment cycles or repeated fluorodeoxyuridine pre-treatment allowed enhancing cell killing to >95 % at 8 kBq/ml 125I-iododeoxyuridine. About 50 and 160 decays per S-phase cells in controls and S-phase synchronization, respectively, were responsible for the observed cell killing at 0.8 kBq/ml radio-iododeoxyuridine. Conclusion: These data show the successful application of fluorodeoxyuridine that provided increased 125I-iododeoxyuridine Auger radiation cell killing efficacy through S-phase synchronization and high DNA incorporation of radio-iododeoxyuridine.

Distal locking of femoral nails: evaluation of a new radiation-independent targeting system.

OBJECTIVES: The purpose of this study was to assess the effectiveness of a novel radiation-independent aiming device for distal locking of intramedullary nails in a human cadaver model. METHODS: A new targeting system was used in 25 intact human cadaver femora for the distal locking procedure after insertion of an intramedullary nail. The number of successful screw placements and the time needed for this locking procedure were recorded. The accuracy of the aiming process was evaluated by computed tomography. RESULTS: The duration of the distal locking process was 8.0 ± 1.8 minutes (mean ± SD; range, 4-11 minutes). None of the screw placements required fluoroscopic guidance. Computed tomography revealed high accuracy of the locking process. The incidence angle (α) of the locking screws through the distal locking holes of the nail was 86.8° ± 5.0° (mean ± SD; range, 80°-96°). Targeting failed in 1 static locking screw because of a material defect in the drilling sleeve. CONCLUSIONS: This cadaver study indicated that an aiming arm-based targeting device is highly reliable and accurate. The promising results suggest that it will help to decrease radiation exposure compared with the traditional "free-hand technique."

Techniques for CT and MR, post-processing, radiation.

Brain perfusion can be assessed by CT and MR. For CT, two major techniquesare used. First, Xenon CT is an equilibrium technique based on a freely diffusibletracer. First pass of iodinated contrast injected intravenously is a second method,more widely available. Both methods are proven to be robust and quantitative,thanks to the linear relationship between contrast concentration and x-ray attenuation.For the CT methods, concern regarding x-ray doses delivered to the patientsneed to be addressed. MR is also able to assess brain perfusion using the firstpass of gadolinium based contrast agent injected intravenously. This method hasto be considered as a semi-quantitative because of the non linear relationshipbetween contrast concentration and MR signal changes. Arterial spin labelingis another MR method assessing brain perfusion without injection of contrast. Insuch case, the blood flow in the carotids is magnetically labelled by an externalradiofrequency pulse and observed during its first pass through the brain. Eachof this various CT and MR techniques have advantages and limits that will be illustratedand summarised.Learning Objectives:1. To understand and compare the different techniques for brain perfusionimaging.2. To learn about the methods of acquisition and post-processing of brainperfusion by first pass of contrast agent for CT and MR.3. To learn about non contrast MR methods (arterial spin labelling).

The primary in vivo immune response to Mls-1 (Mtv-7 sag). Route of injection determines the immune response pattern.

Injection of cells expressing the retroviral superantigen Mls-1 (Mtv-7 sag) into adult Mls-1- mice induces a strong immune response including both T- and B-cell activation. This model was used for studying qualitative aspects of the immune response in normal mice with a defined antigen-presenting cell (the B cell) and without the use of adjuvant. BALB/c mice were injected locally or systemically with Mls-1-expressing spleen cells from Mls-1-congenic BALB.D2 mice. Intravenous injection led to an initially strong expansion of Mls-1-reactive V beta 6+ CD4+ cells mainly in the spleen, to a large degree explained by the trapping of reactive cells, and a rapid down-regulation of interleukin-2 (IL-2) and interferon-gamma (IFN-gamma) production, consistent with the proposed tolerogenic property of B cells as antigen-presenting cells. However, these mice developed a slowly appearing but persistent B-cell response dominated by IgG1-producing cells, suggesting a shift in lymphokines produced rather than complete unresponsiveness. Subcutaneous injection into the hind footpad with the same number of cells led to a strong local response in the draining lymph node, characterized by a dramatic increase of V beta 6+ CD4+ T cells, local production of IL-2 and IFN-gamma and a strong but short-lived antibody response dominated by IgG2a-producing cells, characteristic of a T-helper type 1 (Th1) type of response. Both routes of injection led ultimately to deletion of reactive T cells and anergy, as defined by the inability to produce IL-2 upon in vitro stimulation with Mls-1. It is concluded that Mls-1 presented by B cells induces qualitatively different responses in vivo dependent on the route of injection. We propose that the different responses result from the migration of the injected cells to different micro-anatomical sites in the lymphoid tissue. Furthermore, these results suggest that B cells may function as professional antigen-presenting cells in vivo present in an appropriate environment.

Development and evaluation of neural network models to estimate daily solar radiation at Córdoba, Argentina

The objective of this work was to develop neural network models of backpropagation type to estimate solar radiation based on extraterrestrial radiation data, daily temperature range, precipitation, cloudiness and relative sunshine duration. Data from Córdoba, Argentina, were used for development and validation. The behaviour and adjustment between values observed and estimates obtained by neural networks for different combinations of input were assessed. These estimations showed root mean square error between 3.15 and 3.88 MJ m-2 d-1 . The latter corresponds to the model that calculates radiation using only precipitation and daily temperature range. In all models, results show good adjustment to seasonal solar radiation. These results allow inferring the adequate performance and pertinence of this methodology to estimate complex phenomena, such as solar radiation.

Numerical procedure for estimating temperature in solarized soils

The objective of this work was to develop a simplified numerical procedure for the estimation of accumulated monthly hours of solarized soil temperatures. The proposed model requires monthly means of daily solar radiation and maximum air temperature as input data, and a daily pattern of temperature variation assumed to be sine-shaped. The procedure was verified using observations made during the years 1992 and 1993 in Jaguariúna, SP. The proposed procedure can predict monthly temperature hours at 10 cm depth in the solarized soil, with acceptable accuracy, in the region for which it was developed.

Swiss population exposure to radiation by interventional radiology in 2008.

The aim of this study was to investigate the radiation exposure of the Swiss population to interventional procedures. A nationwide survey was conducted in Switzerland. The annual effective dose per capita due to interventional procedures was found to be 0.14 mSv, corresponding to 12% of the total dose. Coronary angiography and percutaneous coronary interventions were found to be the most frequent and the most irradiating interventional procedures, accounting for 52% of the total examination frequency and 64% of the dose delivered to the population. Switzerland stands at the same level as other countries in terms of effective dose per capita due to interventional radiology.

Cerebral aneurysm exclusion by CT angiography based on subarachnoid hemorrhage pattern: a retrospective study.

BACKGROUND: To identify patients with spontaneous subarachnoid hemorrhage for whom CT angiography alone can exclude ruptured aneurysms. METHODS: An observational retrospective review was carried out of all consecutive patients with non-traumatic subarachnoid hemorrhage who underwent both CT angiography and catheter angiography to exclude an aneurysm. CT angiography negative cases (no aneurysm) were classified according to their CT hemorrhage pattern as "aneurismal", "perimesencephalic" or as "no-hemorrhage." RESULTS: Two hundred and forty-one patients were included. A CT angiography aneurysm detection sensitivity and specificity of 96.4% and 96.0% were observed. All 35 cases of perimesencephalic or no-hemorrhage out of 78 CT angiography negatives also had negative angiography findings. CONCLUSIONS: CT angiography is self-reliant to exclude ruptured aneurysms when either a perimesencephalic hemorrhage or no-hemorrhage pattern is identified on the CT within a week of symptom onset.

Pattern dystrophy with high intrafamilial variability associated with Y141C mutation in the peripherin/RDS gene and successful treatment of subfoveal CNV related to multifocal pattern type with anti-VEGF (ranibizumab) intravitreal injections.

OBJECTIVE: To identify disease causing mutation in three generations of a Swiss family with pattern dystrophy and high intrafamilial variability of phenotype. To assess the effect of intravitreal ranibizumab injections in the treatment of subfoveal choroidal neovascularization associated with pattern dystrophy in one patient. METHODS: Affected family members were ascertained for phenotypic and genotypic characterization. Ophthalmic evaluations included fundus photography, autofluorescence imaging, optical coherence tomography, and International Society for Clinical Electrophysiology of Vision standard full-field electroretinography. When possible family members had genetic testing. The proband presented with choroidal neovascularization and had intravitreal injections as needed according to visual acuity and optical coherence tomography. RESULTS: Proband had a multifocal type pattern dystrophy, and his choroidal neovascularization regressed after four intravitreal injections. The vision improved from 0.8 to 1.0, and optical coherence tomography showed complete anatomical restoration. A butterfly-shaped pattern was observed in her cousin, whereas a fundus pulverulentus pattern was seen in a second cousin. Aunt had a multifocal atrophic appearance, simulating geographic atrophy in age-related macular degeneration. The Y141C mutation was identified in the peripherin/RDS gene and segregated with disease in the family. CONCLUSION: This is the first report of marked intrafamilial variation of pattern dystrophy because of peripherin/RDS Y141C mutation. Intravitreal ranibizumab injections might be a valuable treatment for associated subfoveal choroidal neovascularization.

Postnatal expression pattern of calcium-binding proteins in organotypic thalamic cultures and in the dorsal thalamus in vivo.

The present study describes the postnatal expression of calbindin, calretinin and parvalbumin and glutamic acid decarboxylase (GAD) and microtubule-associated protein 2 (MAP2) in organotypic monocultures of rat dorsal thalamus compared to the thalamus in vivo. Cultures were maintained for up to 7 weeks. Cortex-conditioned medium improved the survival of thalamic cultures. MAP2-immunoreactive material was present in somata and dendrites of small and large-sized neurons throughout the cultures. Parvalbumin immunoreactivity was present in larger multipolar or bitufted neurons along the edge of a culture. These neurons also displayed strong parvalbumin mRNA and GAD mRNA expression, and GABA immunoreactivity. They likely corresponded to cells of the nucleus reticularis thalami. Parvalbumin mRNA, but neither parvalbumin protein nor GAD mRNA, was expressed in neurons with large somata within the explant. They likely represented relay cells. GAD mRNA, but not parvalbumin mRNA, was expressed in small neurons within the explants. Small neurons also displayed calbindin- and calretinin-immunoreactivity. The small neurons likely represented local circuit neurons. The time course of expression of the calcium-binding proteins revealed that all were present at birth with the predicted molecular weights. A low, but constant parvalbumin expression was observed in vitro without the developmental increase seen in vivo, which most likely represented parvalbumin from afferent sources. In contrast, the explantation transiently downregulated the calretinin and calbindin expression, but the neurons recovered the expression after 14 and 21 days, respectively. In conclusion, thalamic monocultures older than three weeks represent a stable neuronal network containing well differentiated neurons of the nucleus reticularis thalami, relay cells and local circuit neurons.

Pattern-based sensing of nucleotides in aqueous solution with a multicomponent indicator displacement assay

A multicomponent indicator displacement assay ( MIDA) based on an organometallic receptor and three dyes can be used for the identification and quantification of nucleotides in aqueous solution at neutral pH.

CT radiation dose in children: a survey to establish age-based diagnostic reference levels in Switzerland

This work aimed at assessing the doses delivered in Switzerland to paediatric patients during computed tomography (CT) examinations of the brain, chest and abdomen, and at establishing diagnostic reference levels (DRLs) for various age groups. Forms were sent to the ten centres performing CT on children, addressing the demographics, the indication and the scanning parameters: number of series, kilovoltage, tube current, rotation time, reconstruction slice thickness and pitch, volume CT dose index (CTDI(vol)) and dose length product (DLP). Per age group, the proposed DRLs for brain, chest and abdomen are, respectively, in terms of CTDI(vol): 20, 30, 40, 60 mGy; 5, 8, 10, 12 mGy; 7, 9, 13, 16 mGy; and in terms of DLP: 270, 420, 560, 1,000 mGy cm; 110, 200, 220, 460 mGy cm; 130, 300, 380, 500 mGy cm. An optimisation process should be initiated to reduce the spread in dose recorded in this study. A major element of this process should be the use of DRLs.