Kinetics of amorphous silica dissolution and the paradox of the silica polymorphs

The mechanisms by which amorphous silica dissolves have proven elusive because noncrystalline materials lack the structural order that allows them to be studied by the classical terrace, ledge, kink-based models applied to crystals. This would seem to imply amorphous phases have surfaces that are disordered at an atomic scale so that the transfer of SiO(4) tetrahedra to solution always leaves the surface free energy of the solid unchanged. As a consequence, dissolution rates of amorphous phases should simply scale linearly with increasing driving force (undersaturation) through the higher probability of detaching silica tetrahedra. By examining rate measurements for two amorphous SiO(2) glasses we find, instead, a paradox. In electrolyte solutions, these silicas show the same exponential dependence on driving force as their crystalline counterpart, quartz. We analyze this enigma by considering that amorphous silicas present two predominant types of surface-coordinated silica tetrahedra to solution. Electrolytes overcome the energy barrier to nucleated detachment of higher coordinated species to create a periphery of reactive, lesser coordinated groups that increase surface energy. The result is a plausible mechanism-based model that is formally identical with the classical polynuclear theory developed for crystal growth. The model also accounts for reported demineralization rates of natural biogenic and synthetic colloidal silicas. In principle, these insights should be applicable to materials with a wide variety of compositions and structural order when the reacting units are defined by the energies of their constituent species.     

Effect of a late evening snack on outpatients with liver cirrhosis

Aims: We have reported that one-week administration of a late evening snack (LES) improved not only malnutrition but also glucose intolerance in hospitalized patients with liver cirrhosis. Thus, we investigated whether long-term LES administration to outpatients for 3 months could reproduce the results obtained from hospitalized patients, especially improved glucose intolerance. If this treatment aggravated glucose intolerance, we tried to find any marker predicting this aggravation before the treatment. Methods: Outpatients were prescribed one pack of oral supplementation of a branched-chain amino acid (BCAA)-enriched nutrient, Aminoleban EN (210 kCal) as a LES without dietician supervision. Both before LES administration and after 3 months, glucose tolerance and liver function were examined using a 75 g oral glucose tolerance test (OGTT), biochemical parameters in blood and the relationship between glucose tolerance (area under the curve (AUC)) and the following serum markers. Results: Branched-chain amino acid/tyrosine ratio (BTR), the number of red blood cells (RBC), and hematocrit (Ht) significantly increased, with significant reduction of blood NH(3) level in patients with a blood glucose level less than 200 mg/dL 2 h after 75 g OGTT. However, the increase of AUC was seen after 3 months of LES administration in patients who had blood glucose higher than 200 mg/dL 2 h after 75 g OGTT. AUC weakly correlated positively with serum 7S collagen and negatively with choline esterase (ChE) and albumin (Alb). Conclusion: 75 g OGTT is a useful marker to predict the worst outcome and avoid the adverse effect of LES treatment in liver cirrhosis patients if performed without adequate nutrient conduct by a dietician.     

Determinants of Intima-Media Thickness in the Young: The ALSPAC Study

ObjectivesThis study characterized the determinants of carotid intima-media thickness (cIMT) in a large (n > 4,000) longitudinal cohort of healthy young people age 9 to 21 years.BackgroundGreater cIMT is commonly used in the young as a marker of subclinical atherosclerosis, but its evolution at this age is still poorly understood.MethodsAssociations between cardiovascular risk factors and cIMT were investigated in both longitudinal (ages 9 to 17 years) and cross-sectional (ages 17 and 21 years) analyses, with the latter also related to other measures of carotid structure and stress. Additional use of ultra-high frequency ultrasound in the radial artery at age 21 years allowed investigation of the distinct layers (i.e., intima or media) that may underlie observed differences.ResultsFat-free mass (FFM) and systolic blood pressure were the only modifiable risk factors positively associated with cIMT (e.g., mean difference in cIMT per 1-SD increase in FFM at age 17: 0.007 mm: 95% confidence interval [CI]: 0.004 to 0.010; p < 0.001), whereas fat mass was negatively associated with cIMT (difference: ?0.0032; 95% CI: 0.004 to ?0.001; p = 0.001). Similar results were obtained when investigating cumulative exposure to these factors throughout adolescence. An increase in cIMT maintained circumferential wall stress in the face of increased mean arterial pressure when increases in body mass were attributable to increased FFM, but not fat mass. Risk factor?associated differences in the radial artery occurred in the media alone, and there was little evidence of a relationship between intimal thickness and any risk factor.ConclusionsSubtle changes in cIMT in the young may predominantly involve the media and represent physiological adaptations as opposed to subclinical atherosclerosis. Other vascular measures may be more appropriate for the identification of arterial disease before adulthood.     

Worldwide Variation in the Use of Nuclear Cardiology Camera Technology,Reconstruction Software,and Imaging Protocols

ObjectivesThis study sought to describe worldwide variations in the use of myocardial perfusion imaging hardware, software, and imaging protocols and their impact on radiation effective dose (ED).BackgroundConcerns about long-term effects of ionizing radiation have prompted efforts to identify strategies for dose optimization in myocardial perfusion scintigraphy. Studies have increasingly shown opportunities for dose reduction using newer technologies and optimized protocols.MethodsData were submitted voluntarily to the INCAPS (International Atomic Energy Agency Nuclear Cardiology Protocols Study) registry, a multinational, cross-sectional study comprising 7,911 imaging studies from 308 labs in 65 countries. The study compared regional use of camera technologies, advanced post-processing software, and protocol characteristics and analyzed the influence of each factor on ED.ResultsCadmium-zinc-telluride and positron emission tomography (PET) cameras were used in 10% (regional range 0% to 26%) and 6% (regional range 0% to 17%) of studies worldwide. Attenuation correction was used in 26% of cases (range 10% to 57%), and advanced post-processing software was used in 38% of cases (range 26% to 64%). Stress-first single-photon emission computed tomography (SPECT) imaging comprised nearly 20% of cases from all world regions, except North America, where it was used in just 7% of cases. Factors associated with lower ED and odds ratio for achieving radiation dose ≤9 mSv included use of cadmium-zinc-telluride, PET, advanced post-processing software, and stress- or rest-only imaging. Overall, 39% of all studies (97% PET and 35% SPECT) were ≤9 mSv, while just 6% of all studies (32% PET and 4% SPECT) achieved a dose ≤3 mSv.ConclusionsNewer-technology cameras, advanced software, and stress-only protocols were associated with reduced ED, but worldwide adoption of these practices was generally low and varied significantly between regions. The implementation of dose-optimizing technologies and protocols offers an opportunity to reduce patient radiation exposure across all world regions.     

儿童痉挛型脑性瘫痪蹲伏步态多学科团队治疗的初步经验CSCD

目的总结多学科团队联合治疗儿童痉挛型脑性瘫痪(以下简称脑瘫)蹲伏步态的初步经验。方法以2018年6月至2020年1月在上海交通大学医学院附属上海儿童医学中心和上海同济大学附属养志康复医院诊治的29例存在蹲伏步态的痉挛型脑瘫患儿为研究对象,男20例,女9例;平均年龄14.3岁(12~16.5岁)。患儿均行三维步态分析,由骨科医生、康复治疗师及步态研究员共同分析步态检查报告,并商定治疗方案,包括:手术前予康复宣教及康复训练3~4周(其中家庭康复1~3周),包括体位摆放、体位转移、轮椅训练、肌力训练等。采取单次多平面手术,包括髋关节重建术、髌韧带推进术、股骨远端短缩伸展截骨术等,如患儿存在扁平外翻足则行Mosca术。术后2周开始院内康复训练,时间8周;予居家康复训练+线上指导10个月。术后每3个月门诊复查,12个月以后行三维步态分析,评价临床疗效。结果29例痉挛型脑瘫蹲伏步态患儿均完成多学科团队治疗方案,医院康复训练及康复指导时间0.5~2周,家庭康复训练2~3周,家庭康复训练指导经互联网完成;均行单次多平面手术,其中髌韧带推进术29例,股骨远端短缩伸展术20例,内收肌切断术10例,股直肌延长术1例,髂腰肌松解术15例,Dega骨盆截骨+股骨近端内翻去旋转截骨术3例,腘绳肌延长术14例,距舟关节复位+距下关节融合术5例,Mosca手术13例。术后复查三维步态分析时间平均为术后13.5个月(12~15个月)。结果显示,患儿术后髋关节在支撑相中末期最大伸展角度较术前平均改善了12.29°,术后膝关节在支撑相中期屈曲角度较术前平均改善了26.84°,术后踝关节在支撑相中期背屈角度较术前平均改善了7.05°。康复评定发现,患儿髋外展、伸髋、伸膝及踝跖屈肌群的肌力均明显提升,平衡稳定性较术前增强,但步行过程中躯干横向位移问题未能改善。结论本研究已经验证了多学科团队治疗儿童痉挛型脑瘫蹲伏步态可有效改善膝关节的僵直状态,提升各关节运动肌群的肌力,明显改善异常的步态外观。儿童痉挛型脑瘫蹲伏步态骨科和康复科联合治疗模式短期疗效良好,远期疗效还有待进一步观察。     

16p11.2微缺失相关儿童癫痫的临床表型与遗传学特征分析北大核心CSCD

目的探究16p11.2微缺失相关儿童癫痫的临床表型与遗传学特征。方法回顾性收集200例应用全外显子测序技术进行癫痫遗传学分析的癫痫患儿,其中9例癫痫患儿为16p11.2微缺失,分析9例16p11.2微缺失患儿的临床表型及遗传学特征。结果16p11.2微缺失检出率为4.5%(9/200)。9例患儿为3~10月龄的婴儿;癫痫发作形式为局灶运动性发作伴意识障碍,部分进展为全身强直-阵挛发作;发作间期脑电图为局灶或多灶性痫样放电,对抗癫痫药物反应良好。9例患儿16p11.2缺失片段大小在398~906 kb之间,缺失基因数为23~33个,且均为致病性变异,其中2例为母源性来源,1例为父源性来源,余均为新发变异。结论16p11.2微缺失在癫痫患儿中有一定的检出率,16p11.2微缺失多为新发变异,且为基因大片段缺失;16p11.2微缺失相关儿童癫痫多在出生1年内起病且为药物反应性癫痫。     

免疫荧光技术检测室内感染蚊虫体内登革病毒的研究

目的　探讨检测媒介蚊虫体内登革病毒的方法。　方法　以埃及伊蚊和白纹伊蚊两种有效媒介为研究对象 ,在人工经口感染大剂量登革 2型病毒 (DEN- 2 )的基础上 ,通过蚊细胞培养病毒分离和蚊头部压片免疫荧光技术进行病毒抗原检测。　结果　埃及伊蚊感染 DEN- 2病毒 1d后 ,接种 C6 / 36细胞 ,盲传一代后第 5 d出现空斑现象 ,确证细胞发病。白纹伊蚊经口感染登革病毒后 ,取吸血雌蚊每日进行头部压片免疫荧光检测 ,结果显示 ,从蚊虫感染后第 1d～第 2 0d内均能检测到病毒抗原。　结论　用免疫荧光技术 ,可直接检测出感染蚊体内是否携带登革病毒 ,是较为简便、省时、敏感的方法     

Local methacholine but not bradykinin potentiates insulin-mediated glucose uptake in muscle in vivo by augmenting capillary recruitment

Aims/hypothesis Insulin has nitric-oxide-dependent vasodilatory effects in muscle, including capillary recruitment, that enhance access for itself and glucose. However, nitric-oxide-dependent vasodilators other than methacholine do not enhance insulin action. Our hypothesis is that methacholine, unlike bradykinin, enhances insulin-mediated glucose uptake in muscle by augmenting capillary recruitment.Methods Local infusion of either methacholine or bradykinin into one leg of the anaesthetised rat was made during physiological insulin (3 mU·kg^–1·min^–1) infusion under euglycaemic conditions and without affecting systemic blood pressure. Whole-body glucose infusion was determined, as was femoral blood flow, 2-deoxyglucose uptake into calf muscles and the metabolism of infused 1-methylxanthine, a measure of capillary recruitment for each leg.Results Methacholine alone (0.3 µmol·l^–1) increased femoral arterial blood flow, increased capillary recruitment but had no effect on 2-deoxyglucose uptake of the test leg relative to the contra-lateral control leg. Insulin alone (systemically) required a glucose infusion rate of 8.7 mg·kg^–1·min^–1 to maintain euglycaemia, increased 2-deoxyglucose uptake and capillary recruitment, but was without effect on femoral blood flow in either leg. Local methacholine with systemic insulin infusion increased femoral blood flow, 2-deoxyglucose uptake and capillary recruitment in the test leg only. Bradykinin (0.07 µmol·l^–1), alone or with insulin, administered in a manner that increased femoral blood flow similarly to methacholine, did not affect 2-deoxyglucose uptake or capillary recruitment.Conclusions/interpretation Methacholine but not bradykinin enhances insulin-mediated muscle glucose uptake in vivo. We conclude that methacholine acts at specific sites in the vasculature of muscle to stimulate capillary recruitment and thereby enhance insulin access.     

Osteoarticular and muscle infectious lesions in patients with the human immunodeficiency virus

Summary Between 1988 and 1995, 1832 HIV positive patients were evaluated in our institution. We studied the epidemiologic, immunologic and bacteriologic data, laboratory tests, and X-Ray films in those with musculoskeletal infection. We reviewed twenty-one cases of musculoskeletal infection in twenty patients aged 23–35 years (mean 28,6 years, M:F=15:5). In all of them risk factor for HIV was intravenous drug abuse. The number of CD4 positive lymphocytes ranged from 0,003 to 0,5 10⁹/l. Staphylococcus aureus was the organism responsible of the infection in twelve cases, all active intravenous drug abusers at the time the diagnosis was done. The remaining causative agents were: Mycobacterium tuberculosis (3 cases), Candida albicans (2 cases), Salmonella subgroup 1 (1 case), Neisseria gonorrhoeae (1 case), Pseudomona aeruginosa (1 case) and Streptococcus agalactiae (1 case). Fifteen infections were diagnosed between 1988 and 1991 and 6 between 1992 and 1995. Musculoskeletal infectious lesions in HIV positive patients in our country are related in the majority of cases to intravenous drug abuse. In the last four years due to a National medical health care plan conducted to educate this group of people the number of musculoskeletal infections is decreasing.