[Primary skull base chondrosarcoma: a clinicopathological analysis]

Objective: To investigate the clinicopathological features, immunophenotype, molecular characteristics and differential diagnosis of primary skull base chondrosarcoma. Methods: Nine cases of primary skull base chondrosarcoma were collected at the First Affiliated Hospital of Fujian Medical University, from January 2006 to June 2019, reviewed for the clinical and radiologic data and morphologic features, immunophenotype and molecular characteristics. Results: Among all the 9 cases, six were male, three were frmale, with average age 47 years, and median age 47 years; five cases were WHO gradeⅠ, and four were WHO grade Ⅱ. Microscopically, the tumor showed lobulated growth pattern with low-medium cellularity within a chondroid or mucoid background. The tumor cells showed mild-moderate atypia, with binucleated forms, and mitosis was rare or occasional. Immunohistochemistry (IHC) showed tumor cells were positive for S-100 protein, vimentin, SOX-9 and D2-40, and negative for Brachyury, CK, EMA and CK8/18; the Ki-67 index was low (1% to 5%). Molecular analysis showed IDH1 R132C mutation in four cases. Conclusions: Skull base chondrosarcoma is a rare cartilaginous malignant tumor with a good prognosis. Its characteristic morphologies, combined with IHC and molecular detection are helpful for the differential diagnosis.

In situ Raman scattering study on a controllable plasmon-driven surface catalysis reaction on Ag nanoparticle arrays

Control of the plasmon-driven chemical reaction for the transformation of 4-nitrobenzenethiol to p,p'-dimercaptoazobenzene by Ag nanoparticle arrays was studied. The Ag nanoparticle arrays were fabricated by means of nanosphere lithography. By changing the PS particle size, the localized surface plasmon resonance (LSPR) peaks of the Ag nanoparticle arrays can be tailored from 460 to 560 nm. The controlled reaction process was monitored by in situ surface-enhanced Raman scattering. The reaction can be dramatically influenced by varying the duration of laser exposure, Ag nanoparticle size, laser power and laser excitation wavelength. The maximum reaction speed was achieved when the LSPR wavelength of the Ag nanoparticle arrays matched the laser excitation wavelength. The experimental results reveal that the strong LSPR can effectively drive the transfer of the 'hot' electrons that decay from the plasmon to the reactants. The experimental results were confirmed by theoretical calculations.

Antibacterial silver-containing silica glass prepared by ion implantation

Recently, there is much interest in nanocomposites consisting of metal nanoparticles dispersed in dielectric matrix. Silver is the first candidate used in antibacterial research. In the present study, sliver-containing silica glass is prepared by ion implantation. The bactericidal properties of Ag-implanted samples are investigated using E. coli. The implanted samples are characterized by optical absorption spectroscopy, atomic force microscopy and transmission electron microscopy. The size and position of the silver nanoparticles formed by ion implantation can be optimized by adjusting the implanted process parameters. All the implanted samples show antibacterial properties. But the samples with silver nanoparticle-enriched surfaces possess excellent antibacterial properties in comparison with other implanted samples. This indicates that ion implantation is a potential method for synthesizing antibacterial biomaterials.

Synthesis and Magnetic Properties of Maghemite (gamma-Fe(2)O(3)) Short-Nanotubes

We report a rational synthesis of maghemite (gamma-Fe(2)O(3)) short-nanotubes (SNTs) by a convenient hydrothermal method and subsequent annealing process. The structure, shape, and magnetic properties of the SNTs were investigated. Room-temperature and low-temperature magnetic measurements show that the as-fabricated gamma-Fe(2)O(3) SNTs are ferromagnetic, and its coercivity is nonzero when the temperature above blocking temperature (T(B)). The hysteresis loop was operated to show that the magnetic properties of gamma-Fe(2)O(3) SNTs are strongly influenced by the morphology of the crystal. The unique magnetic behaviors were interpreted by the competition of the demagnetization energy of quasi-one-dimensional nanostructures and the magnetocrystalline anisotropy energy of particles in SNTs.

ZnO single-crystal films fabricated by the oxidation of zinc-implanted sapphire

Zinc oxide single-crystal films are prepared by the oxidation of zinc-implanted sapphire at 700 °C for 2 h in oxygen ambient. The cross-section transmission electron microscopy image and the selected-area electron diffraction (SAED) pattern show that ZnO single-crystal films are formed on the surface of the zinc-implanted sapphire substrate. The quality and excitonic properties of the single-crystal ZnO films are studied through absorption spectra, the photoluminescence spectra and resonant Raman spectrum. The mechanisms for the formation of single-crystal ZnO films are discussed.

Controlling the growth of ZnO quantum dots embedded in silica by Zn/F sequential ion implantation and subsequent annealing

We report the formation of embedded ZnO quantum dots (QDs) by Zn and F ion sequential implantation and subsequent annealing. Optical absorption and photoluminescence spectrum measurements, transmission electron microscopy bright field images and selected area electron diffraction patterns indicate that ZnO QDs were formed after annealing in air or vacuum at temperatures higher than 500 °C. Atomic force microscopy images show a comparatively flat surface of the annealed samples, which indicates that only very few Zn atoms are evaporated to the surfaces. The formation of ZnO QDs during the thermal annealing can be attributed to the direct oxidization of Zn nanoparticles by the oxygen molecules in the substrate produced during the implantation of F ions. The quality of ZnO QDs increases with the increase of annealing temperature.

RETRACTED: Isolation, characterization and expression of a gene from Brassica napus encoding a LIM-domain protein

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Formation and microstructural investigation of Ag–Cu alloy nanoclusters embedded in SiO2 formed by sequential ion implantation

We report on the formation of alloy nanoclusters in silica by Ag/Cu ion sequential implantation. The formation of alloy nanocluster has been evidenced by optical absorption spectra, selected area electron diffraction and energy dispersive X-ray spectra. The microstructure characters of nanoclusters have been studied by high resolution transmission electron microscopy. The lattice distortion of some nanoclusters has been observed. A model has been given to explain the distortion. Some defects (partial dislocation, stacking faults) have been found in nanoclusters.

A new type of scanning electron microscope using the coaxial backscattered electrons

A new coaxial detection system for backscattered electrons in SEM is described. This coaxial detection system allows us to collect only the backscattered electrons that have lost a small percentage of the primary energy, emerging from the sample surface with a take-off angle defined by the objective lens. This new configuration reinforces the atomic-number contrast and suppresses effectively the topographic contrast. The simulation and experimental results confirm these expectations: this new type of SEM is very suitable for observing differences in atomic number. Moreover, by associating the obtained image with a conventional secondary electron image, we build a third (color) image that allows us to give finally at the same time, in a single image, both of the chemical and topographic information.

Application of breath-hold T2-weighted, first-pass perfusion and gadolinium-enhanced T1-weighted MR imaging for assessment of myocardial viability in a pig model

The purpose of this study was to correlate the abnormal signal area on various magnetic resonance (MR) images to the infarct area on pathologic examination and to assess the myocardial viability on the basis of MR images. T2-weighted, first-pass perfusion, and delayed gadolinium-enhanced T1-weighted images were used as "one-stop examinations" in a pig model of reperfused myocardial infarction. The results of each MR image were compared with those of 2,3, 5-triphenyltetrazolium chloride (TTC) staining. The abnormal signal areas on T2-weighted and Gd-enhanced T1-weighted images were larger than the infarct areas on TTC staining (34.7% and 32.3% vs. 28.3%; P< 0.05), whereas the nonperfused areas on perfusion images were correlated (25.6% vs, 28.3%; P = 0.139). Electron microscopic examination showed severely distorted ultrastructures in the infarct areas and mildly damaged ultrastructures in the peri-infarct areas. Perfusion images probably reflected the infarct areas, whereas T2-weighted and Gd-enhanced T1-weighted images seemed to include peri-infarct as well as infarct areas.

The spatial distribution and resolution of coaxial backscattered electrons in SEM, calculated by monte carlo simulations

We simulate, within a sample, the trajectories of the backscattered electrons detected in a scanning electron microscopy with a particular detection geometry. Thus we obtain the depth and lateral distributions, according to the adjustable parameter values, of the detected electrons. Finally, the scanline profile across a chemical edge is drawn. The conditions corresponding to the best lateral resolution are established; we obtain an ultimate resolution of the same order as the beam diameter.

Radiation-sensitive Arabidopsis mutants are proficient for T-DNA transformation

Stable transformation of plants by Agrobacterium T-DNAs requires that the transgene insert into the host chromosome. Although most of the Agrobacterium Ti plasmid genes required for this process have been studied in depth, few plant-encoded factors have been identified, although such factors, presumably DNA repair proteins, are widely presumed to exist. It has previously been suggested that the UVH1 gene product is required for stable T-DNA integration in Arabidopsis. Here we present evidence suggesting that uvh1 mutants are essentially wild type for T-DNA integration following inoculation via the vacuum-infiltration procedure.

Cloning and characterization of a gene (UVR3) required for photorepair of 6-4 photoproducts in Arabidopsis thaliana

UV radiation induces two major classes of pyrimidine dimers: the pyrimidine [6-4] pyrimidone photoproduct (6-4 product) and the cyclobutane pyrimidine dimer (CPD). Many organisms produce enzymes, termed photolyases, that specifically bind to these damage products and split them via a UV-A/blue light-dependent mechanism, thereby reversing the damage. These photolyases are specific for either CPDs or 6-4 products. A gene that expresses a protein with 6-4 photolyase activity in vitro was recently cloned from Drosophila melanogaster and Xenopus laevis. We report here the isolation of a homolog of this gene, cloned on the basis of sequence similarity, from the higher plant Arabidopsis thaliana. This cloned gene produces a protein with 6-4 photolyase activity when expressed in Escherichia coli. We also find that a previously described mutant of Arabidopsis (uvr3) that is defective in photoreactivation of 6-4 products carries a nonsense mutation in this 6-4 photolyase homolog. We have therefore termed this gene UVR3. Although homologs of this gene have previously been shown to produce a functional 6-4 photolyase when expressed in heterologous systems, this is the first demonstration of a requirement for this gene for photoreactivation of 6-4 products in vivo.

UV- and gamma-radiation sensitive mutants of Arabidopsis thaliana

Arabidopsis seedlings repair UV-induced DNA damage via light-dependent and independent pathways. The mechanism of the "dark repair" pathway is still unknown. To determine the number of genes required for dark repair and to investigate the substrate-specificity of this process we isolated mutants with enhanced sensitivity to UV radiation in the absence of photoreactivating light. Seven independently derived UV sensitive mutants were isolated from an EMS-mutagenized population. These fell into six complementation groups, two of which (UVR1 and UVH1) have previously been defined. Four of these mutants are defective in the dark repair of UV-induced pyrimidine [6-4]pyrimidinone dimers. These four mutant lines are sensitive to the growth-inhibitory effects of gamma radiation, suggesting that this repair pathway is also involved in the repair of some type of gamma-induced DNA damage product. The requirement for the coordinate action of several different gene products for effective repair of pyrimidine dimers, as well as the nonspecific nature of the repair activity, is consistent with nucleotide excision repair mechanisms previously described in Saccharomyces cerevisiae and nonplant higher eukaryotes and inconsistent with substrate-specific base excision repair mechanisms found in some bacteria, bacteriophage, and fungi.

Photorepair mutants of Arabidopsis

UV radiation induces two major DNA damage products, the cyclobutane pyrimidine dimer (CPD) and, at a lower frequency, the pyrimidine (6-4) pyrimidinone dimer (6-4 product). Although Escherichia coli and Saccharomyes cerevisiae produce a CPD-specific photolyase that eliminates only this class of dimer, Arabidopsis thaliana, Drosphila melanogaster, Crotalus atrox, and Xenopus laevis have recently been shown to photoreactivate both CPDs and 6-4 products. We describe the isolation and characterization of two new classes of mutants of Arabidopsis, termed uvr2 and uvr3, that are defective in the photoreactivation of CPDs and 6-4 products, respectively. We demonstrate that the CPD photolyase mutation is genetically linked to a DNA sequence encoding a type II (metazoan) CPD photolyase. In addition, we are able to generate plants in which only CPDs or 6-4 products are photoreactivated in the nuclear genome by exposing these mutants to UV light and then allowing them to repair one or the other class of dimers. This provides us with a unique opportunity to study the biological consequences of each of these two major UV-induced photoproducts in an intact living system.

Little or No Repair of Cyclobutyl Pyrimidine Dimers Is Observed in the Organellar Genomes of the Young Arabidopsis Seedling

A Southern-blot-based, site-specific assay for ultraviolet (UV)-induced cyclobutyl pyrimidine dimers (CPDs), employing the CPD-specific enzyme T4 endonuclease V, was used to follow the repair of this lesion in particular DNA sequences in 5- to 6-d-old Arabidopsis thaliana seedlings. CPDs, measured as enzyme-sensitive sites, in nuclear sequences were removed rapidly in the light but were repaired slowly, if at all, in the dark. This result was identical to that obtained in prior analyses of CPDs in total cellular DNA. Assay of representative chloroplast and mitochondrial sequences in the same DNA preparations revealed that, in contrast to nuclear sequences, enzyme-sensitive sites are inefficiently eliminated in both the presence and absence of visible light. These observations suggest that Arabidopsis seedlings possess little or no capacity for the repair of CPDs in the organellar genomes. Given the fact that the UV dose employed only marginally affected the growth of the seedlings, we suggest that Arabidopsis seedlings must possess very efficient mechanism(s) for the tolerance of UV-induced DNA damage.

A mechanism for intergenomic integration: abundance of ribulose bisphosphate carboxylase small-subunit protein influences the translation of the large-subunit mRNA

Multimeric protein complexes in chloroplasts and mitochondria are generally composed of products of both nuclear and organelle genes of the cell. A central problem of eukaryotic cell biology is to identify and understand the molecular mechanisms for integrating the production and accumulation of the products of the two separate genomes. Ribulose bisphosphate carboxylase (Rubisco) is localized in the chloroplasts of photosynthetic eukaryotic cells and is composed of small subunits (SS) and large subunits (LS) coded for by nuclear rbcS and chloroplast rbcL genes, respectively. Transgenic tobacco plants containing antisense rbcS DNA have reduced levels of rbcS mRNA, normal levels of rbcL mRNA, and coordinately reduced LS and SS proteins. Our previous experiments indicated that the rate of translation of rbcL mRNA might be reduced in some antisense plants; direct evidence is presented here. After a short-term pulse there is less labeled LS protein in the transgenic plants than in wild-type plants, indicating that LS accumulation is controlled in the mutants at the translational and/or posttranslational levels. Consistent with a primary restriction at translation, fewer rbcL mRNAs are associated with polysomes of normal size and more are free or are associated with only a few ribosomes in the antisense plants. Effects of the rbcS antisense mutation on mRNA and protein accumulation, as well as on the distribution of mRNAs on polysomes, appear to be minimal for other chloroplast and nuclear photosynthetic genes. Our results suggest that SS protein abundance specifically contributes to the regulation of LS protein accumulation at the level of rbcL translation initiation.

Regulation of Photosynthesis during Leaf Development in RbcS Antisense DNA Mutants of Tobacco

We have previously characterized RbcS antisense DNA mutants of tobacco that have drastic reductions in their content of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; S.R. Rodermel, M.S. Abbott, L. Bogorad [1988] Cell 55: 673-681). In this report we examine the impact of Rubisco loss on photosynthesis during tobacco (Nicotiana tabacum) leaf development. Photosynthetic capacities are depressed in the antisense leaves, but the patterns of change in photosynthetic rates during the development of these leaves are similar to those in wild-type plants: after attaining a maximum in young leaves, photosynthetic capacities undergo a prolonged senescence decline in older leaves. The alterations in photosynthetic capacities in both the wild type and mutant are closely correlated with changes in Rubisco activity and content. During wild-type leaf development, Rubisco accumulation is regulated by coordinate changes in RbcS and rbcL transcript accumulation, whereas in the antisense leaves, Rubisco content is a function of RbcS, but not rbcL, transcript abundance. This indicates that large subunit protein production is controlled posttranscriptionally in the mutants. The antisense leaves accumulate near-normal levels of chlorophyll and representative photosynthetic proteins throughout development, suggesting that photosynthetic gene expression is not feedback regulated by Rubisco abundance. Considered together, the data in this paper indicate that leaf developmental programs are generally insensitive to sharp reductions in Rubisco content and emphasize the metabolic plasticity of plant cells in achieving optimal photosynthetic rates.

Nuclear-organelle interactions: the immutans variegation mutant of Arabidopsis is plastid autonomous and impaired in carotenoid biosynthesis

The immutans (im) variegation mutant of Arabidopsis thaliana contains green- and white-sectored leaves due to the action of a nuclear recessive gene. The mutation is somatically unstable, and the degree of sectoring is influenced by light and temperature. Whereas the cells in the green sectors contain normal chloroplasts, the cells in the white sectors are heteroplastidic and contain non-pigmented plastids that lack organized lamellar structures, as well as small pigmented plastids and/or rare normal chloroplasts. This indicates that the plastids in im white cells are not affected equally by the nuclear mutation and that the expression of immutans is 'plastid autonomous'. In contrast to other variegation mutants with heteroplastidic cells, the defect in im is not maternally inherited. immutans thus represents a novel type of nuclear gene-induced variegation mutant. It has also been found that the white tissues of immutans accumulate phytoene, a non-colored C40 carotenoid intermediate. This suggests that immutans controls, either directly or indirectly, the activity of phytoene desaturase (PDS), the enzyme that converts phytoene to zeta-carotene in higher plants. However, im is not the structural gene for PDS. A secondary effect of carotenoid deficiency, both in immutans and in wild-type plants treated with a herbicide that blocks carotenoid synthesis, is an increase in acid ribonuclease activity in white tissue. It is concluded that the novel variegation generated by the immutans mutation should offer great insight into the complex circuitry that regulates nuclear-organelle interactions.

Destabilization of rbcS sense transcripts by antisense RNA

Steady-state rbcS mRNA levels are drastically reduced in transgenic tobacco plants that express rbcS antisense RNAs. We have found that these reductions are not due to an effect of the antisense RNA at the level of rbcS transcription; rather, the sense mRNAs are more actively degraded in the mutant than wild-type plants. We have examined the kinetics of this turnover process by inhibiting transcription with cordycepin, and have found that rbcS sense mRNA decay is accelerated about five-fold in the antisense plants. This provides direct evidence that antisense RNAs can serve to destabilize sense transcripts in plants.

Photosynthesis, Rubisco Activity and Amount, and Their Regulation by Transcription in Senescing Soybean Leaves

Senescence is a phase of leaf ontogeny marked by declining photosynthetic activity that, in soybean (Glycine max [L.] Merr.), is paralleled by a decline in chloroplast function. Soybean leaves have different patterns of decline in photosynthetic capacity and chloroplast function associated with nodal position and sink activity. The objective of this work was to determine whether leaves from nodes 3 and 6 of soybean, which show these different patterns, are similarly regulated with respect to ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) activity and content and also to ascertain the degree of regulation of Rubisco content by transcription. Leaves from nodes 3 and 6 of field-grown soybean plants were sampled periodically from the time of their unfolding until near death. In situ CO2-exchange rate (CER) increased to a maximal level in both leaves and then declined slowly. For node 3 leaves the decline was progressive, but for node 6 leaves the decline was arrested at about 75% of maximum CER for a period of about 20 d, coincident with the onset of rapid seed growth, before a short period of very rapid decline immediately preceding leaf death. Rubisco activities and Rubisco content were directly correlated with CER in the leaves exhibiting the two different patterns. Rubisco activation ratio was similar for the two leaves and did not change throughout development. The primary regulator of photosynthesis at the physiological level, thus, was the amount of Rubisco protein. Decreases in Rubisco holoenzyme during senescence of both leaves were accompanied by coordinate decreases in the levels of mRNAs for the small and large subunits of Rubisco, suggesting that the decrease in Rubisco enzyme amounts during soybean leaf senescence is due to slower transcription rates and that levels of these mRNAs are coordinately controlled during senescence as they are during chloroplast development. However, plastid DNA template availability and posttranscriptional controls may also influence Rubisco content during senescence of these leaves. We conclude that soybean leaf photosynthesis likely unfolds according to a single developmental program but that modifications can be superimposed upon this program to maximize photosynthetic rates.