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PubMedDate not supplied

Progress in clinical trials for coronary arterial restenosis using beta radiation sources.

Vascular brachytherapy has yet taken the leap into progression from emerging technology to standard of care dependent on the outcome of clinical trials. Data collected from early pilot trials and on-going clinical trials indicate that such a progression is achievable. Three-year follow-up data from patients treated with intracoronary radiation for the prevention of restenosis are now available. Data from larger trials are being assessed using angiographic and intravascular ultrasound analysis. The beta radiation studies are demonstrating different levels of efficacy, raising new issues regarding dosimetry and potential complications. Past trials have examined the use of vascular brachytherapy for recurrence prevention of restenosis in patients with in-stent restenosis. New data related to the use of liquid-filled balloon systems and radioactive stent are also being collected. This article updates the current status of clinical trials in vascular brachytherapy utilizing beta emitters, highlighting preliminary results and assessing their implications for the development of this field.

Beta Particles↗
PubMedDate not supplied

Video-rate and continuous visual stimuli do not produce equivalent response timings in visual cortical neurons.

Video cathode ray tube (CRT) technology has proven to be extremely valuable for performing research in the visual system. However, the image on a CRT monitor is not constant, but consists of a series of brief pulses. This has implications for any study that explores the responses of neurons in the visual system on short time scales. In particular, there is no unambiguous time point at which a visual stimulus presented via CRT may be said to have ended. Recordings from single units in visual cortical area V1 of an awake primate demonstrate that, when studying changes in response timing on the order of 10 ms or less, stimuli delivered at video frame rates do not duplicate the effects seen with stimuli that have continuous functions of luminance versus time. Additionally, there does not seem to be any clear method of comparing the results obtained with video-rate stimuli with results obtained with continuous-time stimuli that holds for all conditions. These effects are especially critical when exploring the time course of the neuronal responses to the ending of a visual stimulus (off-response). Our findings cast doubt upon the recently reported result that off-responses have consistently shorter latencies than on-responses.

Animals↗
PubMed1994

Postcolumn radionuclide detection of low-energy beta emitters in capillary electrophoresis.

A postcolumn radionuclide detection system for capillary electrophoresis (CE) is described. Eluant from an electrophoresis capillary is directed onto a peptide binding membrane that has been previously coated with a solid scintillator. The membrane is moved in a preselected pattern relative to the fixed capillary outlet during electrophoresis. Light emission from scintillation is imaged onto a charge-coupled device (CCD) using a series of 35-mm camera lenses. Detection of two low-energy beta- emitters (35S and 3H) not previously reported for capillary electrophoresis is demonstrated. The separation efficiencies are similar to those obtained with on-line UV detection. The response for 35S-labeled methionine is linear (r2 = 0.996) from 66 amol to 11 fmol. Detection limits are 88 zmol (0.03 Bq) for 32P-labeled analytes, 17 amol (0.94 Bq) for 35S-labeled analytes, and 8 fmol (8.5 Bq) for 3H-labeled analytes.

Beta Particles↗
PubMed1998

Determination of 226Ra in mineral drinking waters by alpha liquid scintillation with rejection of beta-gamma emitters.

The radiotoxicity of radium isotopes (especially the long-half-life 226Ra) requires their monitoring in drinking waters or nuclear wastes. We studied the applicability of the PERALS method of detection (photon electron rejecting alpha liquid scintillation) for radium measurement. This method combines alpha liquid scintillation with pulse shape analysis for beta rejection and specific chemical extractants included in the scintillating cocktail. Radium is separated by an extractive-scintillator cocktail called RADAEX containing 2-methyl-2-heptylnonanoic acid (HMHN) and dicyclohexano-21-crown-7 (Cy(2)21C7) as extractant molecules. The variation of the radium extraction has been studied relative to pH, salt concentrations, anion and cation effects, and the volume ratio between aqueous and organic phases. The main parameter affecting the radium extraction in mineral drinking water is its complexation by inorganic anions, especially sulfate. Due to the lack of thermodynamic data, some complexation constants had to be determined. For instance, the value reported in this paper for radium sulfate (log beta = 2.58 +/- 0.22) is in good agreement with that from the literature. The knowledge of complexation constants allows the determination of radium extraction recovery for any solution when the inorganic anion concentrations had been measured by capillary zone electrophoresis. The detection limit for this technique is found to be equal to 0.006 Bq.L-1 using only 6 mL of sample solution for analysis. Several French mineral waters have been studied and the results compared with determinations of uranium and thorium concentrations by ICPMS and time-resolved laser induced fluorescence (TRLIF).

Beta Particles↗
PubMed1993

Radiolytic footprinting. Beta rays, gamma photons, and fast neutrons probe DNA-protein interactions.

Ionizing radiations induce numerous damages in DNA, especially strand breaks. The hydroxyl radical OH., produced by the radiolysis of water, is mainly responsible for this effect. The fact that strand breakage occurs at all nucleotides and that bound proteins may locally radioprotect DNA at the binding site lead us to develop a radiolytic footprinting method to study DNA-protein interactions. Three different radiations were used: beta rays, gamma photons, and fast neutrons. In order to validate this technique, three well-known interaction systems were tested: the lac repressor-lac operator of Escherichia coli, the cyclic AMP receptor protein (CRP) of E. coli and its specific site in the lac regulation region, and the core nucleosome. Radiolytic footprinting gives results similar to those obtained by more classical probes: DNase I, complexes of orthophenanthroline (OP) and copper, complexes of ethylenediaminetetraacetate ion (EDTA) and iron, and UV light. For the same system (lac repressor), irradiation with either gamma photons or fast neutrons gives identical results.

Animals↗
PubMed2001

Backbone dynamics of a module pair from the ligand-binding domain of the LDL receptor.

The ligand-binding domain of the LDL receptor consists of seven contiguous LDL-A modules. The fifth of these ligand-binding modules is absolutely required for recognition of both LDL and beta-VLDL particles. A four-residue linker of variable sequence connects each pair of modules, except for modules four and five, which are connected by a 12-residue linker. To provide a more detailed understanding of the structural relationship in a typical pair of functionally important LDL-A repeats of the LDLR, we investigated the backbone dynamics of repeats five (LR5) and six (LR6) alone and in the context of the covalently connected LR5-6 pair. Our results reveal substantial flexibility in the four-residue linker connecting the two repeats in the LR5-6 pair. The intrinsic dynamic behavior of each repeat is essentially unchanged when the repeats are covalently connected. These observations indicate that the relative orientation of repeats in LR5-6 is not fixed. Modeled in an extended conformation, the linker can separate LR5 and LR6 by up to 15 A, a distance that would allow substantial freedom of motion of each repeat with respect to the other in the pair.

Amino Acid Motifs↗
PubMed2002

Recycling of scrap cathode ray tubes.

It is estimated that approximately 50% of the weight of a computer monitor is composed of cathode ray tube (CRT) glass. Thus, the successful recycling of scrap CRT glass can greatly relieve the disposal problem created by scrap monitors. CRT glass may be considered a hazardous waste due to its high lead concentration. A CRT can be divided into panel (front) glass and funnel (back) glass. Several coatings have been applied to the surface of the CRT panel and funnel glass. These coatings may present an adverse effectto the environment by obstructing the recycling and reuse of the CRT glass. To recycle CRT glass, a series of tests has been conducted to remove the coatings from scrap CRT glass. In this study, the CRT panel and funnel glass obtained from scrap computer monitors was cleaned by wet-scrubbing and ultrasonic cleaning methods. This cleaned CRT glass is intended to be recycled and reused by CRT manufacturers. This study shows that the wet-scrubbing method has a better coating removal performance and no associated pollution problem (i.e., no additional chemical additives). Thus, the wet-scrubbing method is recommended for use as a CRT coating removal method. The results of these tests are presented in this paper.

Beta Particles↗
PubMed2004

Influence of beta-radiation sterilisation in properties of new chitosan/soybean protein isolate membranes for guided bone regeneration.

Novel chitosan (cts) and soybean protein isolate (SI) blended membranes were prepared. These membranes were produced by solvent casting. Besides combining the advantages of both materials, cts/SI membranes exhibit a biphasic structure that will eventually originate in situ porous formation, through a two-step degradation mechanism. In this particular work the effect of beta-radiation over the properties of these membranes was evaluated. beta-radiation sterilisation was performed at three different doses (25, 50 and 100 kGy) and eventual surface chemical changes were evaluated by Fourier transformed infrared--with attenuated total reflection and contact angle measurements. Moreover, eventual bulk properties changes due to beta-radiation were assessed by means of mechanical tensile tests and water uptake measurements. In general, no substantial changes were detected on the studied properties, with the exception of the surface energy that was found to be slightly increased for higher applied doses.

Beta Particles↗
PubMed1993

The modulation of radiation-induced damage to pig skin by essential fatty acids.

The ability of essential fatty acids (EFAs) to modulate radiation-induced normal tissue injury was assessed in pig skin. Female Large White pigs (approximately 25 Kg) received 3 ml/day orally of either an 'active' oil [So-1100, containing 9% gamma-linolenic acid (GLA)] or a 'placebo' oil (So-1129) for just 4 weeks before or for 4 weeks before and for 16 weeks after irradiation; localised irradiation of skin was with single doses of beta-rays from 22.5 mm diameter 90Sr/90Y plaques. The severity of the acute reaction, assessed in terms of erythema or moist desquamation, was significantly less in those pigs that received So-1100 both before and after irradiation, as compared with those receiving that oil only prior to irradiation and the 'placebo' groups. Dose modification factors (DMFs) of between 1.13-1.24 were obtained. A similar reduction in the severity of acute skin injury was seen in pigs receiving So-1100 for only 10 weeks after irradiation. Late skin damage, assessed in terms of late erythema or dermal necrosis, was also reduced with So-1100, with DMFs of 1.14-1.51. No such modification was observed if So-1100 was only administered for 4 weeks prior to irradiation. No adverse side-effects were apparent as a result of EFA administration. So-1100 may represent a safe and valuable method of increasing the therapeutic gain in radiotherapy.

Animals↗
PubMed2004

Reinforcement of single-walled carbon nanotube bundles by intertube bridging.

During their production, single-walled carbon nanotubes form bundles. Owing to the weak van der Waals interaction that holds them together in the bundle, the tubes can easily slide on each other, resulting in a shear modulus comparable to that of graphite. This low shear modulus is also a major obstacle in the fabrication of macroscopic fibres composed of carbon nanotubes. Here, we have introduced stable links between neighbouring carbon nanotubes within bundles, using moderate electron-beam irradiation inside a transmission electron microscope. Concurrent measurements of the mechanical properties using an atomic force microscope show a 30-fold increase of the bending modulus, due to the formation of stable crosslinks that effectively eliminate sliding between the nanotubes. Crosslinks were modelled using first-principles calculations, showing that interstitial carbon atoms formed during irradiation in addition to carboxyl groups, can independently lead to bridge formation between neighbouring nanotubes.

Beta Particles↗
PubMed2004

Strong bundles.

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Beta Particles↗
PubMed2003

Beta irradiation: new uses for an old treatment: a review.

Beta radiation has a long history as a treatment modality in ophthalmology. It is a convenient and practical method of applying radiation and has the advantage of minimal tissue penetration. There has been a recent resurgence in the use of beta radiation in other areas in medicine, such as the prevention of restenosis after coronary artery stenting. Beta radiation has been shown in vitro and in vivo to inhibit proliferation of human Tenon's fibroblasts, which enter a period of growth arrest but do not die. Effects on the cell cycle controller p53 have been shown to be important in this process. In ophthalmology, beta radiation has been used widely for the treatment of pterygium and is under evaluation for treatment of age-related macular degeneration and for controlling wound healing after glaucoma drainage surgery. In this latter role, beta radiation may be particularly appropriate for use in developing countries to improve the results of trabeculectomy while potentially avoiding some of the side effects of other antimetabolites.

Aged↗