PET-CT在非完全实性肺结节中的应用价值

肺癌在中国恶性肿瘤的发病率位居第一,随着低剂量薄层CT在肺癌筛查中的广泛应用,临床发现更多表现为非完全实性结节的肺腺癌,目前众多研究使CT影像学特征和肺腺癌病理的关系得到更进一步的认知,虽然CT能对部分非完全实性结节做出定性和定位诊断,但仍有部分非完全实性结节诊断困难,PET-CT结合了病灶的代谢信息和精确的定位信息,从而提高对肺部结节诊断的敏感性、特异性、准确性,综合多个文献PET-CT在非完全实性结节中的诊断分期价值较CT无明显提升,却在评估预后和制定合适手术方案上可以起到一定的作用,本文就PET-CT在SSN中的应用价值进行阐述。     

Clathrin light chain B: gene structure and neuron-specific splicing.

The clathrin light chains are components of clathrin coated vesicles, structural constituents involved in endocytosis and membrane recycling. The clathrin light chain B (LCB) gene encodes two isoforms, termed LCB2 and LCB3, via an alternative RNA splicing mechanism. We have determined the structure of the rat clathrin light chain B gene. The gene consists of six exons that extend over 11.9 kb. The first four exons and the last exon are common to the LCB2 and LCB3 isoforms. The fifth exon, termed EN, is included in the mRNA in brain, giving rise to the brain specific form LCB2 but is excluded in other tissues, generating the LCB3 isoform. Primary rat neuronal cell cultures express predominantly the brain specific LCB2 isoform, whereas primary rat cultures of glia express only the LCB3 isoform, suggesting that expression of the brain-specific LCB2 form is limited to neurons. Further evidence for neuronal localization of the LCB2 form is provided using a teratocarcinoma cell line, P19, which can be induced by retinoic acid to express a neuronal phenotype, concomitant with the induction of the LCB2 form. In order to determine the sequences involved in alternative splice site selection, we constructed a minigene containing the alternative spliced exon EN and its flanking intron and exon sequences. This minigene reflects the splicing pattern of the endogenous gene upon transfection in HeLa cell and primary neuronal cell cultures, indicating that this region of the LCB gene contains all the necessary information for neuron-specific splicing.     

烟青虫感染核型多角体病毒后围食膜的病变

昆虫的围食膜是衬在昆虫中肠内一种网状的结构,它可充作虫体抵御外来病原侵染的一道屏障。关于鳞翅目昆虫幼虫感染了昆虫病毒后围食膜的病变问题,国内外鲜有报道。尤锡镇和康慧娟(1985)曾以实验证明家蚕围食膜对核型多角体病毒有灭活作用,而且认为核型多角体病毒不能侵染和破坏围食膜。Derksen和Granados(1988)则证明染病幼虫的围食膜因不同杆状病毒(包括两种核型多角体病     

Cloning of the recA gene from a free-living leptospire and distribution of RecA-like protein among spirochetes

A recombinant plasmid carrying the recA gene of Leptospira biflexa serovar patoc was isolated from a cosmid library of genomic DNA by complementation of an Escherichia coli recA mutation. The cloned serovar patoc recA gene efficiently restored resistance to UV radiation and methyl methanesulfonate. Recombination proficiency was also restored, as measured by the formation of Lac+ recombinants from duplicated mutant lacZ genes. Additionally, the cloned recA gene increased the spontaneous and mitomycin C-induced production of lambda phage in lysogens of an E. coli recA mutant. The product of the cloned recA gene was identified in maxicells as a polypeptide with an Mr of 43,000. Antibodies prepared against the E. coli RecA protein cross-reacted with the serovar patoc RecA protein, indicating structural conservation. Southern hybridization data showed that the serovar patoc recA gene has diverged from the recA gene of L. interrogans, Leptonema illini, and E. coli. With the exception of the RecA protein of L. interrogans serovar hardjo, the RecA protein of the Leptospira serovars and L. illini were synthesized at elevated levels following treatment of cells with nalidixic acid. The level of detectable RecA correlated with previous studies demonstrating that free-living cells of L. biflexa serovars and L. illini were considerably more resistant to DNA-damaging agents than were those of parasitic L. interrogans serovars. RecA protein was not detected in cells of virulent Treponema pallidum or Borrelia burgdorferi.     

Thylakoid differentiation in endocyanelles

Cyanophora paradoxa Korshikov synchronized autotrophically in a light-dark regime of 14 h light and 10 h dark divides in the last two hours of the dark period. The division rate of the free-living blue-green alga, Synechococcus leopoliensis Raciborski, at identical culture conditions (24°C; 32 W m⁻²) is only slightly lowered in the light period. The comparison of thylakoid differentiation in the endocyanelles of Cyanophora paradoxa and in Synechococcus leopoliensis during the light-dark regime yields (1) the same ensemble of pigment-protein complexes in both organisms, (2) comparable syntheses of chlorophyll and phycobilins of Cyanophora paradoxa grown under 32 W m⁻² and of Synechococcus leopoliensis grown under light intensities below 9.2 W m⁻², and (3) identical photosynthetic oxygen evolution during the light period of the light-dark regime with minima at the beginning, in the middle (6th–7th h), and at the end of the light period. In both organisms this stage-specific oxygen evolution is inhibited by treatment with chloroamphenicol. Cycloheximide, however, causes no significant alterations. Results are discussed in view of the endosymbiotic theory.     

Effects of magnetic fields on mammary tumor development induced by 7, 12-dimethylbenz(a)anthracene in rats

A series of epidemiological studies have indicated associations between exposure to magnetic fields (MFs) and a variety of cancers, including breast cancer. In order to test the possibility that MF acts as a cancer promoter or copromoter, four separate experiments have been conducted in rats in which the effects of chronic exposure to MFs on the development of mammary tumors induced by 7,12-dimethylbenz(a)anthracene (DMBA) were determined. Female rats were exposed in magnetic coils for 91 days (24 h/day) to either alternating current (AC; 50 Hz)-MF or direct current (DC)-MF. Magnetic flux density of the DC-MF was 15 mT. Two AC-MF exposures used a homogeneous field with a flux density of 30 mT (rms); one used a gradient field with flux density ranging from 0.3–1 μT. DMBA (5 mg) was administered orally at the onset of MF exposure and was repeated thrice at intervals of 1 week. In each experiment, 18–36 animals were exposed in 6 magnetic coils. The same number of rats were used as sham-exposed control. These control animals were treated with DMBA and were placed in dummy coils in the same room as the MF-exposed rats. Furthermore, groups of age-matched rats (reference controls) were treated with DMBA but housed in another room to exclude any MF exposure due to the magnetic stray field from the MF produced by coils. At the end of the exposure or sham-exposure period, tumor number and weight or size of tumors were determined at necropsy. Results were as follows: In sham-exposed animals or reference controls, the tumor incidence varied between 50 and 78% in the 4 experiments. The average number of mammary tumors per tumor-bearing animal varied between 1.6 and 2.9. In none of the experiments did MFs significantly alter tumor incidence, but in one of the experiments with AC-MF exposure at 30 mT, the number of tumors per tumor-bearing animal was significantly increased. Furthermore, exposure to a DC-MF at 15 mT significantly enhanced the tumor weight. Exposure to a gradient AC-MF at 0.3–1 μT exerted no significant effects. These experiments seem to indicate that MFs at high flux densities may act as a promoter or copromoter of breast cancer. However, this interpretation must be considered only a tentative conclusion because of the limitations of this study, particularly the small sample size used for MF exposure and the lack of repetition of data. © 1993 Wiley-Liss. Inc.     

Valproic Acid Causes Proteasomal Degradation of DICER and Influences miRNA Expression

Valproic acid (VPA) is a commonly used drug to treat epilepsy and bipolar disorders. Known properties of VPA are inhibitions of histone deacetylases and activation of extracellular signal regulated kinases (ERK), which cannot fully explain VPA’s clinical features. We found that VPA induces the proteasomal degradation of DICER, a key protein in the generation of micro RNAs. Unexpectedly, the concentration of several micro RNAs increases after VPA treatment, which is caused by the upregulation of their hosting genes prior to DICER degradation. The data suggest that a loss of DICER protein and changes in micro RNA concentration contributes to the clinical properties of VPA. VPA can be used experimentally to down regulate DICER protein levels, which likely reflects a natural regulation of DICER.