SIMS MICROSCOPY: METHODOLOGY,PROBLEMS AND PERSPECTIVES IN MAPPING DRUGS AND NUCLEAR MEDICINE COMPOUNDS

Secondary ion mass spectrometry (SIMS) microscopy, a mass spectrometry method designed in the 1960s, offers new analytical capabilities, high sensitivity (ppm to ppb region), high specificity and improved lateral resolution, thus facilitating insight into many physiological and biomedical questions. Apart from the sample preparation and the physical characteristics of the detection, the biological model must also be considered. SIMS analysis of diffusible ions and molecules requires strict cryogenic procedures which always begin by a flash-freeze fixation. Cellular integrity can be checked by mapping the major element distributions since intra and extracellular ions are redistributed only in damaged cells. Cryofixing may be followed either by a freeze-fracture methodology or by cryoembedding and dry-cutting. Chemical sample preparation is only used for ions or molecules bound to fixed cell structures. The use of scanning procedures ameliorates the lateral resolution and chromosome imaging has been reported with probe size of below 50nm. Absolute quantification can be derived for embedded specimen by using internal references included in tissue equivalent resins. The sensitivity is limited by the ionization yield of the tag element and may be further impaired when working at high mass resolution (≥5000) to eliminate interfering cluster ions. SIMS drug mapping is usually performed after in vitro administration of a molecule to cell culture systems. Drug detection is accomplished indirectly by detecting a tag isotope naturally present or introduced by labelling, mainly with halogens,¹⁵N and¹⁴C. Molecular imaging with TOF-SIMS is an appealing alternative especially for heavier compounds. We stress some biological problems through a critical review of published SIMS drug studies. SIMS proved useful in assessing the targeting specificity of nuclear medicine pharmaceutics, even after in vivo administration. The first microscopic evidence of a thionamide induced follicular blockade of the iodine organification process is presented in a human sample.     

Thymoquinone is protective against 2,3,7,8-tetrachlorodibenzo-p-dioxin induced hepatotoxicity

We investigated changes in rat liver tissues following administration of thymoquinone (TQ) against 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induced hepatotoxicity. Fifty rats were assigned randomly to five groups of 10 as follows: control, corn oil, TCDD, TQ and TCDD + TQ. Biochemical and histopathological analyses were conducted on liver tissue. We found that 30 day TCDD administration caused histopathological changes in liver including thickening of Glisson’s capsule, intracytoplasmic vacuolization in hepatocytes, sinusoidal dilation, vascular and sinusoidal congestion and inflammatory cell infiltration. TCDD administration increased malondialdehyde (MDA), total oxidant status (TOS), alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) levels in rat liver tissue and reduced glutathione (GSH), superoxide dismutase (SOD), catalase (CAT) and total antioxidant status (TAS) levels compared to all other groups. In the TQ treated group, GSH, SOD, CAT and TAS levels increased compared to all other groups. MDA, TOS, ALT, AST, ALP levels decreased compared to all other groups. Our histological findings were consistent with the biochemical findings. The oxidative and histologic effects of TCDD were eliminated by TQ treatment. TCDD administration caused oxidative stress in rat liver and TQ administered with TCDD prevented TCDD induced hepatotoxicity. TQ could be considered an alternative anti-TCDD toxicity agent.     

中国木薯乙醇的资源潜力及其空间分布

利用气候、土壤、地形和土壤等数据,运用ArcGIS的空间叠加分析功能,分析了中国木薯乙醇的分布生产潜力及空间分布.结果表明:中国适宜木薯分布的区域主要在广西、广东、福建、云南、江西和海南等广大南部地区,这些地区的木薯乙醇生产潜力也最高;适宜木薯种植的未利用地面积较少,仅有1.53×104hm2,其乙醇生产潜力仅能满足目前中国E10汽油约1.0%的乙醇需求量;要满足中国目前E10汽油的全部乙醇需求,需要扩大目前木薯总种植耕地面积的4.4～5.7倍,而中国的粮食安全需求则限制了该目标的实现;中国木薯乙醇满足未来生物乙醇的需求前景不容乐观,中国木薯乙醇企业的发展规划要充分考虑原料的可获性,切不可盲目扩大生产.     

Strong seasonal disequilibrium measured between the oxygen isotope signals of leaf and soil CO2 exchange

The oxygen isotope composition (δ¹⁸O) of atmospheric CO₂ is among a very limited number of tools available to constrain estimates of the biospheric gross CO₂ fluxes, photosynthesis and respiration at large scales. However, the accuracy of the partitioning strongly depends on the extent of isotopic disequilibrium between the signals carried by these two gross fluxes. Chamber‐based field measurements of total CO₂ and CO¹⁸O fluxes from foliage and soil can help evaluate and refine our models of isotopic fractionation by plants and soils and validate the extent and pattern of isotopic disequilibrium within terrestrial ecosystems. Owing to sampling limitations in the past, such measurements have been very rare and covered only a few days. In this study, we coupled automated branch and soil chambers with tuneable diode laser absorption spectroscopy techniques to continuously capture the δ¹⁸O signals of foliage and soil CO₂ exchange in a Pinus pinaster Aït forest in France. Over the growing season, we observed a seasonally persistent isotopic disequilibrium between the δ¹⁸O signatures of net CO₂ fluxes from leaves and soils, except during rain events when the isotopic imbalance became temporarily weaker. Variations in the δ¹⁸O of CO₂ exchanged between leaves, soil and the atmosphere were well explained by theory describing changes in the oxygen isotope composition of ecosystem water pools in response to changes in leaf transpiration and soil evaporation.     

Optimal range of prey size for antlions

1. Antlions are opportunistic trap building predators that cannot control prey encounter. Their trap should ideally retain a great diversity of prey. However, building a single trap that captures many prey with varying characteristics can be challenging. 2. A series of five different ant species ranging from thin to large, of sizes ranging from 2.75 to 6.5 mm, and a mean weight ranging from 0.54 to 6.00 mg were offered in a random succession to antlions. The state of satiation of the antlions was controlled, and their mass and the depth of their pit were recorded. The reaction of antlion to the prey, the probability of capture as well as the time to escape were recorded. 3. The probability of an antlion reaction is an increasing function of the pit depth and a decreasing function of antlion mass. The probability of capture is highest for intermediate prey mass and is an increasing function of pit depth. The time to escape is a declining function of prey mass and an increasing function of pit depth. 4. There is an upper limit to prey mass given that large prey escape out of the pit. There is a lower limit to prey mass given the difficulty to apprehend the smallest, thin species. Consequently, there is a range of prey mass, corresponding to a medium‐sized ant of 2 mg, for which the pit functions best. The physics of insect locomotion on sandy slopes was identified as the key to understanding the functioning of antlion pits.     

Uptake and intracellular transport of acidic fibroblast growth factor: evidence for free and cytoskeleton-anchored fibroblast growth factor receptors

Endocytic uptake and intracellular transport of acidic FGF was studied in cells transfected with FGF receptor 4 (FGFR4). Acidification of the cytosol to block endocytic uptake from coated pits did not inhibit endocytosis of the growth factor in COS cells transfected with FGFR4, indicating that it is to a large extent taken up by an alternative endocytic pathway. Fractionation of the cells demonstrated that part of the growth factor receptor was present in a low-density, caveolin-containing fraction, but we were unable to demonstrate binding to caveolin in immunoprecipitation studies. Upon treatment of the cells with acidic FGF, the activated receptor, together with the growth factor, moved to a juxtanuclear compartment, which was identified as the recycling endosome compartment. When the cells were lysed with Triton X-100, 3-([3-chloramidopropyl]dimethylammonio)-2-hydroxy-1-propanesulfona te, or 2-octyl glucoside, almost all surface-exposed and endocytosed FGFR4 was solubilized, but only a minor fraction of the total FGFR4 in the cells was found in the soluble fraction. The data indicate that the major part of FGFR4 is anchored to detergent-insoluble structures, presumably cytoskeletal elements associated with the recycling endosome compartment.     

The calcium‐dependent protein kinase CPK7 acts on root hydraulic conductivity

The hydraulic conductivity of plant roots (Lp_r) is determined in large part by the activity of aquaporins. Mechanisms occurring at the post‐translational level, in particular phosphorylation of aquaporins of the plasma membrane intrinsic protein 2 (PIP2) subfamily, are thought to be of critical importance for regulating root water transport. However, knowledge of protein kinases and phosphatases acting on aquaporin function is still scarce. In the present work, we investigated the Lp_r of knockout Arabidopsis plants for four Ca²⁺‐dependent protein kinases. cpk7 plants showed a 30% increase in Lp_r because of a higher aquaporin activity. A quantitative proteomic analysis of wild‐type and cpk7 plants revealed that PIP gene expression and PIP protein quantity were not correlated and that CPK7 has no effect on PIP2 phosphorylation. In contrast, CPK7 exerts a negative control on the cellular abundance of PIP1s, which likely accounts for the higher Lp_r of cpk7. In addition, this study revealed that the cellular amount of a few additional proteins including membrane transporters is controlled by CPK7. The overall work provides evidence for CPK7‐dependent stability of specific membrane proteins.