Urea handling by the renal countercurrent system: Insights from computer simulation

Summary The renal handling of urea has been investigated with the aid of a computer model of the countercurrent system in which active electrolyte reabsorption occurs along the entire ascending limb of Henle's loop. In this model, summarized in Fig. 9, the buildup of a corticopapillary gradient for urea is optimized if there isnet addition of urea to loops of Henle only in the outer medulla. This added urea remains within the tubular system until it is reabsorbed from collecting ducts in the inner medulla. Thus, a net transfer of urea from outer to inner medulla is accomplished (via distal tubule and cortical collecting duct). There is nonet addition of urea to loops of Henle within the inner medulla; in this region, the loops act simply as countercurrent exchangers for urea. Computer simulation of systematic variation in the urea permeabilities of each nephron segment shows that interference with any element of the above schema results in impairment of the medullary accumulation of urea relative to plasma. Simulation of varying rates of urinary urea excretion demonstrates that this model can account for the ability of the kidney to excrete substantial amounts of urea without an accompanying osmotic loss of water. The major insight gained from this study is that net addition of urea to loops of Henle in the outer medulla greatly enhances the medullary accumulation of urea, whereas, net addition of urea to loops within the inner medulla tends to defeat such accumulation and hence the urinary concentrating process. This general principle applies also to an alternate model of the countercurrent system, in which electrolyte reabsorption from thin ascending limbs of Henle is passive.     

运用循环经济理念治理我国城市生活垃圾

阐述了循环经济的内涵,探讨了在中国城市垃圾中实行循环经济的方式、方法、措施及对策.     

Peptide loading onto recycling HLA-DR molecules occurs in early endosomes

Presentation of exogenous antigens to MHC class II-restricted T cells can follow two different processing pathways. The classical pathway requires newly synthesized MHC class II molecules, invariant chain and HLA-DM expression, whereas the alternative pathway is independent of protein synthesis, invariant chain and HLA-DM. In both cases, MHC class II molecules associate with peptides derived from exogenous antigens that have been processed in endocytic compartments. Different endosomal/prelysosomal compartments where peptide/MHC class II complexes and HLA-DM molecules accumulate have been described. We show here that the alternative pathway uses an earlier compartment than the classical pathway. Experiments with chemically cross-liniked antigen suggest that recycling MHC class II molecules present rapidly degraded antigens, leading to a rapid immune response to exogenously added influenza virus proteins.     

飞秒激光小切口角膜基质透镜取出术人体角膜基质透镜再利用的研究新进展

随着飞秒激光小切口角膜基质透镜取出术(SMILE)在临床的广泛开展,术中大量的一片式角膜基质透镜被完整地取出,从而引发学者们开始对人体角膜基质透镜的再利用进行了研究。在基础方面,主要从细胞生物学、免疫学及生物力学角度,将透镜用于培养角膜成纤维细胞、构建生物角膜支架、描述角膜的生物力学行为等;在临床方面,将透镜植入自体或同种异体的角膜,以矫治远视和老视、修补角膜溃疡穿孔、治疗角膜缺陷性疾病等,收到了良好的效果。     

动静脉内瘘穿刺间距选择与再循环发生的护理问题

目的探讨不同的内瘘穿刺间距与再循环及通路流量的关系。方法对第二军医大学长海医院肾内科45例维持性血液透析患者的血管通路分别采用TRANSONICHDO2血液透析监护仪测得实际通路内血流量（Qa）,并分为3组：Qa〉1000ml/min（13例）;Qa600～1000ml/min（20例）;Qa〈600ml/min（12例）,选择不同的穿刺间距（4、6、8、10cm）,采用尿素法（UT）和TRANS2种方法进行再循环率测定。结果UT与STRANS的测定结果,采用非参数方法进行统计,Spearman相关系数rs=0.934,P〈0.01,结果显示2种测定方法有很好的相关性;当Qa〉600ml/min时,在穿刺间距≥4cm时RTRANS（%）=0,RUT（%）=（2.91±0.93）,均为阴性结果;当Qa〈600ml/min时,RTRANS（%）和针距呈直线负相关,r=-0.956,P〈0.01;RUT（%）和针距亦呈直线负相关,r=-0.996,P〈0.01;结论在Qa〉600ml/min时,大于4cm穿刺间距不会引起R;但在Qa〈600ml/min,R随间距的缩短而增大,只有当间距〉10cm时无通路内再循环;认为每月进行通路流量检测十分必要,除能指导穿刺间距的选择,利于内瘘保护外,又能及时发现血管功能障碍,提前给予临床干预。     

血液透析中内瘘血管两种不同穿刺方法运用的临床观察

目的比较改进后的动脉端针尖向心方向穿刺内瘘术与常用动脉端针尖逆心方向穿刺内瘘术的优缺点。方法选取我院2008年1月至2011年1月,采用穿刺内瘘术行血液透析的慢性肾功能衰竭患者60例,随机分为甲、乙两组。甲组采用常用的动脉端针尖逆心方向穿刺术,乙组采用动脉端针尖向心方向穿刺术,血液透析为每周2次,共随访观察3年,对两组病员的肌酐下降率及假性动脉瘤形成率进行对比分析,比较其优缺点。结果改进后的动脉端针尖向心方向穿刺内瘘术较动脉端针尖逆心方向穿刺术假性动脉瘤形成的机率减小,肌酐下降率基本相同。结论动脉端针尖向心方向穿刺术较动脉端逆心方向穿刺术能较有效地预防假性动脉瘤形成,并未增加再循环,也不降低透析效率,可在血液净化中推广应用。     

欠发达地区如何发展畜牧业循环经济

发展欠发达地区畜牧业的循环经济可提高粮食产量,减少污染、开辟新能源、增加农民收入。可参照禽-粪-饲料、畜-粪-渔-果、畜-沼-菜、草-畜-草等的循环模式发展。应采取的主要措施有:大力宣传、调整农牧业结构、秸秆过腹还田、先行示范,逐步推广、坚持外延扩张与内涵提高相结合等。促进欠发达地区畜牧业循环经济快速发展。     

Low-level thiocyanate concentrations impact on iron oxidation activity and growth of Leptospirillum ferriphilum through inhibition and adaptation

Leptospirillum ferriphilum is the dominant iron-oxidising bacterium in traditional microbial communities utilised in bioprocesses for gold recovery from sulfidic minerals. Ferrous iron oxidation activity and growth of unadapted and thiocyanate-adapted L. ferriphilum HT was studied in batch culture across increasing thiocyanate (SCN⁻) concentrations in the range 0–2 mg/L to assess the feasibility of recycling remediated cyanidation wastewaters. Thiocyanate concentrations of 1 mg/L and 1.4 mg/L induced an inhibitory effect in the unadapted culture wherein ferrous iron oxidation rate and cell growth were compromised. A substantial lag in the onset of ferrous iron oxidation occurred at concentrations above 0.5 mg/L SCN⁻, with no oxidation activity above 1.75 mg/L SCN⁻. The adapted culture, however, was uninhibited across the SCN⁻ concentration range investigated and demonstrated a higher specific ferrous iron oxidation rate owing to reduced growth. It is postulated that SCN⁻ exposure in the absence of adaptation induces osmotic stress. Moreover, upregulation of genes associated with the synthesis of osmo-protectants may be responsible for the preservation of activity observed in the adapted culture. As L. ferriphilum is dominant within the biooxidation tank community, evidence of sustained iron oxidation activity at low-level SCN⁻ concentrations affirms the potential of recycling bioremediated cyanidation wastewater.     

Lithium recovery from production waste by thermal pre-treatment

Among the two types of lithium batteries, non-rechargeable primary-type batteries, and secondary-type rechargeable lithium-ion batteries (LIB), there have been efforts to recycle lithium only for LIB. Primary lithium batteries experience a vast market expansion with a present market volume of 2500–3200 t Li/a. Owed to a lack of apt technology, approx. 25% of this lithium is disposed of as lithium foil punching residues and is not recycled. The non-uniform lithium metal waste qualities, the high hazard potential when handling metallic lithium as well as the intake of impurities through the processing procedure are the main reasons why lithium from this source has not been recycled, yet.These problems have been solved through thermally converting lithium into Li₂O and Li₃N, followed by dissolution in water and precipitation with CO₂, allowing for obtaining Li₂CO₃ already in battery-grade quality as a crude product (>99.5% purity) after precipitation. Accompanying iodine is recovered in analytical grade quality through sublimation. By means of design of experiments (DoE), a process has been developed and optimized that displays broad input material variability and consumes only water and CO₂ as process chemicals. 83 ± 2.5% isolated yield of Li₂CO₃ was obtained by conducting the oxidation at 400 °C with 0.25 g residue of whatever origin for 2.5 h. As the products bg-Li₂CO₃, I₂, and Fe₂O₃ are all marketable it is almost zero waste.     

小鼠黏附分子nepmucin在内皮细胞内循环机制的探讨

目的探讨nepmucin分子在内皮细胞内的循环途径。方法采用共聚焦荧光显微技术进行内在化实验,分别用4种细胞器标记蛋白抗体[Rab5/胞内体、LAMP-1/溶酶体、γ1-adaptin/外侧高尔基网络(TGN)以及LDLR/分选与循环胞内体]与抗nepmucin抗体双染色转染内皮细胞,观察nepmucin分子内在化后的分布情况。结果 Nepmucin分子出现在胞内体、TGN、溶酶体和分选与循环胞内体中。结论 Nepmucin的循环途径可能是经分选胞内体运输至TGN或循环胞内体,然后回到细胞膜;或是进入溶酶体被降解。