A liquid-scintillation-based primary standardization of Pb

A new radioactivity solution standard of ²¹⁰Pb has been developed and will be disseminated by the National Institute of Standards and Technology (NIST) as standard reference material (SRM) 4337. This new ²¹⁰Pb solution standard is contained in a 5 mL flame-sealed borosilicate glass ampoule, consists of (5.133±0.002) g of a nominal 1 mol L⁻¹ nitric acid solution, has a density of (1.028±0.002) g mL⁻¹ at 20 °C, has carrier ion concentrations of about 11 μg Pb²⁺ and 21 μg Bi³⁺ per gram of solution, and is certified to contain a massic activity (9.037±0.22) kBq g⁻¹ as of the reference time 1200 EST, 15 June 2006. All of the uncertainties cited above correspond to standard uncertainties multiplied by a coverage factor k=2. The standardization for the ²¹⁰Pb content of the solution was based on 4πβ liquid scintillation (LS) measurements using CIEMAT/NIST ³H-standard efficiency tracing (CNET). Confirmatory determinations were also performed by high-resolution HPGe γ-ray spectrometry, by 2π spectrometry with a Si surface barrier detector of separated ²¹⁰Po, and by 4πβ(LS)–γ(NaI) anticoincidence counting.     

“Dark” (compacted) neurons may not die through the necrotic pathway

Dark neurons were produced in the cortex of the rat brain by hypoglycemic convulsions. In the somatodendritic domain of each affected neuron, the ultrastructural elements, except for disturbed mitochondria, were remarkably preserved during the acute stage, but the distances between them were reduced dramatically (ultrastructural compaction). Following a 1-min convulsion period, only a few neurons were involved and their environment appeared undamaged. In contrast, 1-h convulsions affected many neurons and caused swelling of astrocytic processes and neuronal dendrites (excitotoxic neuropil). A proportion of dark neurons recovered the normal structure in 2 days. The non-recovering dark neurons were removed from the brain cortex through two entirely different pathways. In the case of 1-h convulsions, their organelles swelled, then disintegrated and finally dispersed into the neuropil through large gaps in the plasma membrane (necrotic-like removal). Following a 1-min convulsion period, the non-recovering dark neurons fell apart into membrane-bound fragments that retained the compacted interior even after being engulfed by astrocytes or microglial cells (apoptotic-like removal). Consequently, in contrast to what is generally accepted, the dark neurons produced by 1-min hypoglycemic convulsions do not die as a consequence of necrosis. As regards the case of 1-h convulsions, it is assumed that a necrotic-like removal process is imposed, by an excitotoxic environment, on dark neurons that previously died through a non-necrotic pathway. Apoptotic neurons were produced in the hippocampal dentate gyrus by intraventricularly administered colchicine. After the biochemical processes had been completed and the chromatin condensation in the nucleus had reached an advanced phase, the ultrastructural elements in the somatodendritic cytoplasm of the affected cells became compacted. If present in an apparently undamaged environment such apoptotic neurons were removed from the dentate gyrus through the apoptotic sequence of morphological changes, whereas those present in an impaired environment were removed through a necrotic-like sequence of morphological changes. This suggests that the removal pathway may depend on the environment and not on the death pathway, as also assumed in the case of the dark neurons produced by hypoglycemic convulsions.     

香烟辐射水平及所致吸烟者剂量

目的 评估我国吸烟人群因吸烟所致内照射剂量并与其他国家进行比较。方法 收集并分析国内外香烟中²¹⁰Po/²¹⁰Pb辐射水平,推荐主流烟雾中²¹⁰Po/²¹⁰Pb份额,进行我国吸烟者因吸烟所致内照射剂量估算。结果 2015年中国15岁及以上成人现在吸烟者为3.2亿,日平均吸烟量为15.2支;按文献中香烟品牌数量加权的²¹⁰Po /²¹⁰Pb活度均值分别为28.2 mBq/支和39.3 mBq/支;在剂量估算中,²¹⁰Po主流烟雾份额采用模拟装置和志愿者实验结果均值20%,²¹⁰Pb主流烟雾份额采用模拟装置实验结果10%。根据我国日平均吸烟量和现在吸烟者人数估算的我国现在吸烟者年有效剂量为126 μSv·a^-1,集体有效剂量为40746人·Sv。结论 我国香烟中²¹⁰Po/²¹⁰Pb含量约为其它国家香烟的2～3倍,但由于本文采用的主流烟雾份额和²¹⁰Po/²¹⁰Pb剂量转换系数不同于其它文献,所以本文估算的我国吸烟人员吸20支烟所受剂量低于部分国家。     

细胞培养中支原体污染的去除

在运用细胞培养手段的生物学研究和生物工程产品中，支原体污染仍是一个颇为棘手的问题。１１株人的细胞ＳＰＣ－Ａ１、Ｋ５６２、ＨＵＴ－１０２、ＢＴ－３２５、６Ｔ－ＣＥＭ、ＮＫＭ－４５、ＣＮＥ、ＨＬ－６０、ＱＧＹ－７７０１、ＱＺＧ、人羊膜细胞；３株小鼠细胞Ｐ３８８－１、ＹＡＣ－１、Ｐ８１５；１株绒猴细胞Ｂ９５－８；和一株杂交瘤ＱＫＴ３等，已污染了支原体的细胞经ＭＣ－２１０ １μｇ／ｍｌ处理７天，支原体污染     

Transmission of antibodies to Chlamydia Psittaci and Coxiella Burnetii through eggs and “crop milk” in pigeons

Young semi-domesticated pigeons captured or hatched from eggs gathered in Bratislava during 1989–1991 were examined for complement fixing antibodies to Chlamydia psittaci and agglutinating antibodies to Coxiella burnetii. Antibodies to Ch. psittaci were present in 76% of birds younger than 24 h, in 47.7% between 1 and 10 days of age and in 12% of nestlings over 10 days old. Antibodies to Ch. psittaci were also detected in crop milk of 4.1% of 1 to 10 day old birds and in 4.5% of specimens older than 10 days. Antibodies to C. burnetii were not found in juvenile birds under 24 h old, but antibodies against this agent were present in 16.4% birds between 1 and 10 days old and in 18% over 10 days old. Antibodies to C. burnetii were also detected in crop milk collected from crops of 2% of the young birds between 1 and 10 days.     

Dynamic mislocalizations of nuclear pore complex proteins after focal cerebral ischemia in rat

Nuclear pore complexes (NPCs) play an important role in coordinating the transport of proteins and nucleic acids between the nucleus and cytoplasm, and are therefore essential for maintaining normal cellular function and liability. In the present study, we investigated the temporal immunohistochemical distribution of five representative components of NPCs—Ran GTPase‐activating protein 1 (RanGap1), glycoprotein‐210 (Gp210), nucleoporin 205 (Nup205), nucleoporin 107 (Nup107), and nucleoporin 50 (Nup50)—after 90 min of transient middle cerebral artery occlusion (tMCAO) up to 28 days after the reperfusion in rat brains. Single immunohistochemical analyses showed ring‐like stainings along the periphery of the nucleus in sham control brains. After tMCAO, Gp210 and Nup107 immunoreactivity continuously increased from 1 day, and RanGap1, Nup205, and Nup50 increased from 2 days until 28 days, which also displayed progressive precipitations within the nucleus in the peri‐ischemic area, while the ischemic core showed scarce expression with collapsed structure. Double immunofluorescent analyses revealed nuclear retention and apparent colocalization of RanGap1 with Nup205, Gp210 with Nup205, and partial colocalization of Nup205 with Nup107; most of the ischemic changes above were similar to those observed in patients with C9orf72‐genetic amyotrophic lateral sclerosis. Taken together, these observations suggest that the mislocalization of these nucleoporins may be a common pathogenesis of both ischemic and neurodegenerative disease. © 2016 Wiley Periodicals, Inc.