Detection of radiation effects in polymer gel dosimeters using 129Xe NMR

Polymer gel dosimeters consist of monomers, with or without cross-linking agents, dispersed in a gel. Upon exposure to ionizing radiation, polymerization proceeds within the gel matrix, thereby changing several measurable physical properties that can then be related quantitatively to absorbed dose. Several previous studies have examined how various nuclear magnetic resonance (NMR) properties, such as the relaxation rates of water protons, change with dose, and magnetic resonance imaging (MRI) has been used successfully to measure three-dimensional dose distributions in irradiated polymer gels. Here we report our first observations of the manner in which the chemical shift of xenon gas (129Xe) dissolved in a gel changes with absorbed dose, and we introduce the potential use of high resolution xenon NMR spectra for understanding better the dose response of gels. 129Xe possesses a large chemical shift range and xenon spectra are sensitive to subtle changes in the physical and chemical environments in which the gas is dissolved. For doses ranging from 0 Gy to 40 Gy we found that the mean chemical shift of 129Xe was linearly related to dose, and that the gel dosimeter could be described in terms of a two-component model undergoing fast exchange. We found no evidence of radiation damage to the gelatin matrix at doses between 0 Gy and 40 Gy. At 40 Gy, the fast-exchange model begins to break down, and distinct gelatin and poly(methacrylate) resonances are observed at higher doses. High resolution NMR measurements of xenon provide a novel method for probing radiation dose effects in irradiated polymer gels.     

阿克拉霉素A聚氰基丙烯酸异丁酯毫微粒冻干针剂体内外抗肝癌活性

阿克拉霉素A聚氰基丙烯酸异丁酯毫微粒的冻干针剂,能明显抑制体外培养人肝癌细胞株7703的生长,IC50为0.28μg·ml^-1。在0.8μg·ml^-1浓度时,克隆形成抑制率为90%,抑制作用有明显剂量依赖关系而未见明显时间依赖关系。静脉给药后,对常位移植人肝癌模型裸小鼠的抑瘤率为86.84%,肿瘤细胞增殖活性阳性率为20.83%。体内外均显示明显的抗肝癌活性,且体内抗肝癌活性比阿克拉霉素A冻干针剂强。     

清除骨髓中癌细胞的磁性微球研究 II.聚苯乙烯磁性微球的研制

为制备能用于清除骨髓中癌细胞的磁性微球,首先合成了单分散、大粒径的多孔聚苯乙烯交联微球,借助微球多孔结构对其进行磁化。探讨了影响磁化效果的主要因素。为使其与单抗连接紧密,在微球表面聚合了一层聚丙烯醛膜,使其表面带上易与单抗反应的醛基。同时测定了所制微球的磁响应性。X-射线衍射证明磁性物质为γ-Fe₂O₃。     

Changes in performance,maximal oxygen uptake and maximal accumulated oxygen deficit after 5, 10 and 15 days of live high:train low altitude exposure

Nineteen well-trained cyclists (14 males and 5 females, mean initial V˙O_2max 62.3 ml kg^–1 min^–1) completed a multistage cycle ergometer test to determine maximal mean power output in 4 min (MMPO_4min), maximal oxygen uptake (V˙O_2max) and maximal accumulated oxygen deficit (MAOD). The athletes were divided into three groups, each of which completed 5, 10 or 15 days of both a control condition (C) and live high:train low altitude exposure (LHTL). The C groups lived and trained at the ambient altitude of 610 m. The LHTL groups spent 8–10 h night^–1 in normobaric hypoxia at a simulated altitude of 2,650 m, and trained at the ambient altitude of 610 m. The changes to MMPO_4min, V˙O_2max and MAOD in response to LHTL altitude exposure were not significantly different for the 5-, 10- and 15-day treatment periods. For the pooled data from all three treatment periods, there were significant increases in MMPO_4min [mean (SD) 5.15 (0.83) W kg^–1 vs 5.34 (0.78) W kg^–1] and MAOD [50.1 (14.2) ml kg^–1 vs 54.9 (13.1) ml kg^–1] in the LHTL athletes between pre- and post-altitude exposure. There were no significant changes in MMPO_4min [5.09 (0.76) W kg^–1 vs 5.16 (0.86) W kg^–1] or MAOD [50.5 (14.1) ml kg^–1 vs 49.1 (13.0) ml kg^–1] in the C athletes over the corresponding period. There were significant increases in V˙O_2max in the athletes during both the LHTL [63.2 (9.0) ml kg^–1 min^–1 vs 64.1 (9.0) ml kg^–1 min^–1] and C [62.0 (8.6) ml kg^–1 min^–1 vs 63.4 (9.2) ml kg^–1 min^–1] conditions. In these athletes, there was no difference in the impact of 5, 10 or 15 days of LHTL on the increases observed in MMPO_4min, V˙O_2max or MAOD; and LHTL increased MMPO_4min and MAOD more than training at low altitude alone. Electronic Publication     

On the origins of chemical exchange saturation transfer (CEST) contrast in tumors at 9.4 T

Chemical exchange saturation transfer (CEST) provides an indirect means to detect exchangeable protons within tissues through their effects on the water signal. Previous studies have suggested that amide proton transfer (APT) imaging, a specific form of CEST, detects endogenous amide protons with a resonance frequency offset 3.5 ppm downfield from water, and thus may be sensitive to variations in mobile proteins/peptides in tumors. However, as CEST measurements are influenced by various confounding effects, such as spillover saturation, magnetization transfer (MT) and MT asymmetry, the mechanism or degree of increased APT signal in tumors is not certain. In addition to APT, nuclear Overhauser enhancement (NOE) effects upfield from water may also provide distinct information on tissue composition. In the current study, APT, NOE and several other MR parameters were measured and compared comprehensively in order to elucidate the origins of APT and NOE contrasts in tumors at 9.4 T. In addition to conventional CEST methods, a new intrinsic inverse metric was applied to correct for relaxation and other effects. After corrections for spillover, MT and T₁ effects, corrected APT in tumors was found not to be significantly different from that in normal tissues, but corrected NOE effects in tumors showed significant decreases compared with those in normal tissues. Biochemical measurements verified that there was no significant enhancement of protein contents in the tumors studied, consistent with the corrected APT measurements and previous literature, whereas quantitative MT data showed decreases in the fractions of immobile macromolecules in tumors. Our results may assist in the better understanding of the contrast depicted by CEST imaging in tumors, and in the development of improved APT and NOE measurements for cancer imaging. Copyright © 2014 John Wiley & Sons, Ltd.     

Effectiveness of voice therapy in reflux-related voice disorders

Gastroesophageal reflux (GER) with laryngopharyngeal reflux plays a significant role in voice disorders. A significant proportion of patients attending ear, nose, and throat clinics with voice disorders may have gastresophageal reflux disease (GERD). There is no controlled study of the effect of voice therapy on GERD. We assessed the effect of voice therapy in patients with dysphonia and GERD. Thirty‐two patients with dysphonia and GERD underwent indirect laryngoscopy and voice analysis. Esophageal and laryngeal symptoms were assessed using the reflux symptom index (RSI). At endoscopy, esophagitis was graded according to Los Angeles classification. Patients were randomized to receive either voice therapy and omeprazole (20 mg bid) (n = 16, mean [SD] age 36.1 [9.6] y; 5 men; Gp A) or omeprazole alone (n = 16, age 31.8 [11.7] y; 9 men; Gp B). During voice analysis, jitter, shimmer, harmonic‐to‐noise ratio (HNR) and normalized noise energy (NNE) were assessed using the Dr. Speech software (version 4 1998; Tigers DRS, Inc). Hoarseness and breathiness of voice were assessed using a perceptual rating scale of 0–3. Parameters were reassessed after 6 weeks, and analyzed using parametric or nonparametric tests as applicable. In Group A, 9 patients had Grade A, 3 had Grade B, and 1 had Grade C esophagitis; 3 had normal study. In Group B, 8 patients had Grade A, 2 had Grade B esophagitis, and 6 had normal study. Baseline findings: median RSI scores were comparable (Group A 20.0 [range 14–27], Group B 19.0 [15–24]). Median rating was 2.0 for hoarseness and breathiness for both groups. Values in Groups A and B for jitter 0.5 (0.6) versus 0.5 (0.8), shimmer 3.1 (2.5) versus 2.8 (2.0), HNR 23.0 (5.6) versus 23.1 (4.2), and NNE ?7.3 (3.2) versus ?7.2 (3.4) were similar. Post‐therapy values for Groups A and B: RSI scores were 9.0 (5–13; P < 0.01 as compared with baseline) and 13.0 (10–17; P < 0.01), respectively. Ratings for hoarseness and breathiness were 0.5 (P < 0.01) and 1.0 (P < 0.01) and 2.0. Values for jitter were 0.2 (0.0; P = 0.02) versus 0.4 (0.7), shimmer 1.3 (0.7; P < 0.01) versus 2.3 (1.2), HNR 26.7 (2.3; P < 0.01) versus 23.7 (3.2), and NNE ?12.3 (3.0, P < 0.01) versus ?9.2 (3.4; P < 0.01). Improvement in the voice therapy group was significantly better than in patients who received omeprazole alone. Dysphonia is a significant problem in GER. Treatment for GER improves dysphonia, but in addition, voice therapy enhances the improvement.     

DOES VISUAL SUBORDINATE-LEVEL CATEGORISATION ENGAGE THE FUNCTIONALLY DEFINED FUSIFORM FACE AREA?

Functional magnetic resonance imaging was used to compare brain activation associated with basic-level (e.g. bird) and subordinate-level (e.g. eagle) processing for both visual and semantic judgements. We localised the putative face area for 11 subjects, who also performed visual matching judgements for pictures and aurally presented words. The middle fusiform and occipital gyri were recruited for subordinate minus basic visual judgements, reflecting additional perceptual processing. When the face area was localised individually for each subject, analyses in the middle fusiform gyri revealed that subordinate-level processing activated the individuals face area. We propose that what is unique about the way faces engage this region is the focal spatial distribution of the activation rather than the recruitment of the face per se. Eight subjects also performed semantic judgements on aurally presented basic- and subordinate-level words. The parahippocampal gyri were more activated for subordinate-level than basic-level semantic judgements. Finally, the left posterior inferior temporal gyrus was activated for subordinate-level judgements, both visual and semantic, as well as during passive viewing of faces.     

Fast and simplified mapping of mean axon diameter using temporal diffusion spectroscopy

Mapping axon diameter is of interest for the potential diagnosis and monitoring of various neuronal pathologies. Advanced diffusion‐weighted MRI methods have been developed to measure mean axon diameters non‐invasively, but suffer major drawbacks that prevent their direct translation into clinical practice, such as complex non‐linear data fitting and, more importantly, long scanning times that are usually not tolerable for most human subjects. In the current study, temporal diffusion spectroscopy using oscillating diffusion gradients was used to measure mean axon diameters with high sensitivity to small axons in the central nervous system. Axon diameters have been found to be correlated with a novel metric, DDR_⊥ (the rate of dispersion of the perpendicular diffusion coefficient with gradient frequency), which is a model‐free quantity that does not require complex data analyses and can be obtained from two diffusion coefficient measurements in clinically relevant times with conventional MRI machines. A comprehensive investigation including computer simulations and animal experiments ex vivo showed that measurements of DDR_⊥ agree closely with histological data. In humans in vivo, DDR_⊥ was also found to correlate well with reported mean axon diameters in human corpus callosum, and the total scan time was only about 8 min. In conclusion, DDR_⊥ may have potential to serve as a fast, simple and model‐free approach to map the mean axon diameter of white matter in clinics for assessing axon diameter changes. Copyright © 2016 John Wiley & Sons, Ltd.     

Training-induced increases in sea level V˙O2 m a x and endurance are not enhanced by acute hypobaric exposure

The present study used untrained subjects to examine the effect of acute hypobaric exposure during endurance training on subsequent exercise performance at sea level. Two groups, each of nine subjects, completed 5 weeks of endurance training [cycle ergometer exercise for 45 min, three times per week at a heart rate corresponding to 70% of that achieved at the maximal O₂ consumption (V˙O_{2 max} ) either at sea level or at high altitude] in a hypobaric chamber, under either normobaric [sea level, SL; 750 mmHg (100 kPa) ≈90 m] or hypobaric [altitude, ALT; 554 mmHg (73.4 kPa) ≈ 2500 m] conditions and the changes in SL V˙O_{2 max} , SL endurance time and peak blood lactate during the endurance test compared. While each group showed increases in both SL V˙O_{2 max} (≈12%) and SL endurance time (≈71%), there were no significant differences between the groups [SL V˙O_{2 max} , mean (SE) – SL group: pre-training = 42.4 (3.5), post-training = 46.1 (3.5) ml · kg^?1· min^?1, P < 0.005; ALT group: pre-training = 40.8 (2.6), post-training = 47.2 (3.4) ml · kg^?1· min^?1, P < 0.01; SL endurance time – SL group: pre-training 7.1 (1.5), post-training 11.8 (2.9) min, P < 0.01; ALT group: pre-training = 7.5 (0.6), post-training = 13.3 (1.4) min, P < 0.001]. Peak blood lactate during the endurance test was not altered by either training regimen. It is concluded that acute exposure of untrained subjects to hypobaric hypoxia during endurance training has no synergistic effect on the degree of improvement in either SL V˙O_{2 max} or endurance time.     

Modulation of disease severity of dystrophic epidermolysis bullosa by a splice site mutation in combination with a missense mutation in the COL7A1 gene

Dystrophic epidermolysis bullosa (EBD) is a clinically heterogeneous skin disorder, characterized by abnormal anchoring fibrils (AF) and loss of dermal-epidermal adherence. EBD has been linked to the COL7A1 gene at chromosome 3p21 which encodes collagen VII, the major component of the AF. Here we investigated two unrelated EBD families with different clinical phenotypes and novel combinations of recessive and dominant COL7A1 mutations. Both families shared the same recessive heterozygous 14 bp deletion at the exon-intron 115 boundary of the COL7A1 gene. The deletion caused in-frame skipping of exon 115 and the elimination of 29 amino acid residues from the pro-alpha1(VII) polypeptide chain. As a result, procollagen VII was not converted to collagen VII and the C-terminal NC-2 propeptide which is normally removed from the procollagen VII prior to formation of the anchoring fibrils was retained in the skin. All affected individuals also carried missense mutations in exon 73 of COL7A1 which lead to different glycine- to-arginine substitutions in the triple-helical domain of collagen VII. Combination of the deletion mutation with a G2009R substitution resulted in a mild phenotype. In contrast, combination of the deletion with a G2043R substitution led to a severe phenotype. The G2043R substitution was a de novo mutation which alone caused a mild phenotype. Thus, different combinations of dominant and recessive COL7A1 mutations can modulate disease activity of EBD and alter the clinical presentation of the patients.