Charged-particle mutagenesis. 1. Cytotoxic and mutagenic effects of high-LET charged iron particles on human skin fibroblasts.

Cytotoxic and mutagenic effects of high-LET charged iron (56Fe) particles were measured quantitatively using primary cultures of human skin fibroblasts. Argon and lanthanum particles and gamma rays were used in comparative studies. The span of LETs selected was from 150 keV/microns (330 MeV/u) to 920 keV/microns (600 MeV/u). Mutations were scored at the hypoxanthine guanine phosphoribosyl transferase (HPRT) locus using 6-thio-guanine (6-TG) for selection. Exposure to these high-LET charged particles resulted in exponential survival curves. Mutation induction, however, was fitted by the linear model. The relative biological effectiveness (RBE) for cell killing ranged from 3.7 to 1.3, while that for mutation induction ranged from 5.7 to 0.5. Both the RBE for cell killing and the RBE for mutagenesis decreased with increasing LET over the range of 1.50 to 920 keV/microns. The inactivation cross section (sigma i) and the action cross section for mutation induction (sigma m) ranged from 32.9 to 92.0 microns2 and 1.45 to 5.56 X 10(-3) microns2; the maximum values were obtained by 56Fe with an LET of 200 keV/microns. The mutagenicity (sigma m/sigma i) ranged from 2.05 to 7.99 X 10(-5) with an inverse relationship to LET.     

Ventilatory and hematopoietic responses to chronic hypoxia in two rat strains.

Hilltop (H) and Madison (M) strains of Sprague-Dawley rats exhibit strikingly different susceptibilities to the effects of chronic altitude exposure. The H rats develop greater polycythemia, hypoxemia, and pulmonary hypertension. We studied ventilation, pulmonary gas exchange, tissue oxygenation, and hematologic adaptations in the two rat strains during a 50-day exposure to a simulated altitude (HA) of 5,500 m (18,000 ft). There were no strain differences among the variables we studied under sea level (SL) conditions. Within the first 14 days of hypoxic exposure, the only significant strain differences were that erythropoietin (EPO) rose much higher and erythroid activity was greater in the H rats, even though arterial Po2 and PCo2 (Pao2 and PaCo2, respectively), renal venous PO2 (Prvo2), and ventilation (VE) were equivalent in the two strains during this time. By day 14 at HA, the H rats had significantly higher erythroid activity, hematocrit (Hct), and EPO levels, significantly lower PaO2 and PrvO2, but equivalent VE and PaCO2. These changes persisted for the remainder of the exposure, except that the Hct continued to rise and the increase was greater in H rats. Despite the greater O2-carrying capacity of H rats in the later stages of hypoxic exposure, PaO2 and PrvO2 were significantly lower in H rats. There were no strain differences at either SL or HA in ventilatory responses to hypercapnia or hypoxia, in blood O2 affinity or 2,3-diphosphoglycerate, in extrarenal production of EPO, or in EPO clearance. We conclude that early in the hypoxic exposure the H rats produce more EPO at apparently equivalent levels of hypoxia, and this is the first step in the pathogenesis of the maladaptation to HA manifest by H rats. We find no consistent evidence that differences in VE contribute to the variable susceptibility to hypoxia in the two rat strains.     

Screening and analysis of differentially expressed genes from an alien addition line of wheat Thinopyrum intermedium induced by barley yellow dwarf virus infection.

The alien addition line TAI-27 contains a pair of chromosomes of Thinopyrum intermedium that carry resistance against barley yellow dwarf virus (BYDV). A subtractive library was constructed using the leaves of TAI-27, which were infected by Schizaphis graminum carrying the GAV strain of BYDV, and the control at the three-leaf stage. Nine differentially expressed genes were identified from 100 randomly picked clones and sequenced. Two of the nine clones were highly homologous with known genes. Of the remaining seven cDNA clones, five clones matched with known expressed sequence tag (EST) sequences from wheat and (or) barley whereas the other two clones were unknown. Five of the nine differentially expressed sequences (WTJ9, WTJ11, WTJ15, WTJ19, and WTJ32) were highly homologous (identities >94%) with ESTs from wheat or barley challenged with pathogens. These five sequences and another one (WTJ18) were also highly homologous (identities >86%) with abiotic stress induced ESTs in wheat or barley. Reverse Northern hybridization showed that seven of the nine differentially expressed cDNA sequences hybridized with cDNA of T. intermedium infected by BYDV. Three of these also hybridized with cDNA of line 3B-2 (a parent of TAI-27) infected by BYDV. The alien chromosome in TAI-27 was microdissected. The second round linker adaptor mediated PCR products of the alien chromosomal DNA were labeled with digoxygenin and used as the probe to hybridize with the nine differentially expressed genes. The analysis showed that seven differentially expressed genes were homologous with the alien chromosome of TAI-27. These seven differentially expressed sequences could be used as ESTs of the alien chromosome of TAI-27. This research laid the foundation for screening and cloning of new specific functional genes conferring resistance to BYDV and probably other pathogens.     

THE DISCOVERY OF THE GENUS SHELFORDIA CAMERON (HYMENOPTERA: BRACONTOAE: BRACONINAE) IN CHINA, WITH DESCRIPTION OF ONE NEW SPECIES

The genus Shelfordia is discovered in China for the first time, and one new species of this genus (S. chinensis sp. nov.) is fully described and illustrated in the present paper. The type specimen is deposited in the Parasitic Hymenoptera Collection, Zhejiang University, Hangzhou, China.     

EFFECTS OF HELPER PROTEINS ENCODED BY p19 AND orf1-orf2 GENES ON Cyt1Aa PROTEIN EXPRESSION IN ACRYSTALLIFEROUS STRAIN OF BACILLUS THURINGIENSIS

A series of plasmids were constructed to examine the effects of p19 and orf1‐orf2 genes from Bacillus thuringiensis on Cyt1Aa synthesis and inclusion formation. The plasmids expressed the cyt1Aa gene along with either p19 or orf1‐orf2, or each of them coordinatively with p20 in the acrystalliferous strain of B. thuringiensis subsp. israelensis 4Q7. No effect on the expression of Cyt1Aa protein was found when P19 or Orf1‐Orf2 co‐expressed with Cyt1Aa. However, when including p20 gene, the constructs with p19 or orf1‐orf2 gene produced lower yield of Cyt1Aa proteins than without p19 or orf1‐orf2 gene. Electron microscopy observation and bioassay showed that P19 and Orf1‐Orf2 have no influence on the crystal size and toxicity of Cyt1Aa protein. It is presumed that P19 and Orf1‐Orf2 might have negative effects on Cyt1Aa synthesis in B. thuringiensis.     

用分子生物学技术对草菇进行菌株鉴别

利用AP-PCR和RAPD技术对三个草菇菌株进行鉴别,其结果与用草菇菌株V34基因文库中的中等重复序列为探针进行限制性内切酶长度多态性分析(RFLP),及对编码核糖体5.8SrRNA的DNA(rDNA)进行PCR扩增后的产物进行限制性内切酶长度多态性分析(PCR-RFLP)的结果相一致。这一结果显示出用这四种方法对草菇菌株进行鉴别具有相似的效果。同时用这四种方法构建的分子生物学标记显示出这三个菌株中的两个菌株在遗传上有着较大程度的相似性。     

华北蓟属植物的化学分类初探

本文对华北地区蓟属ＣｉｒｓｉｕｍＡｄａｎｓ．１６种植物的甲醇提取液紫外吸收光谱（ＵＶ）进行了比较研究。结果表明,蓟属植物的叶较其它部位的ＵＶ具有较好的稳定性和代表性,其光谱的特征可以作为属下分类的重要依据,其化学分类结果与形态分类基本一致。根据光谱特征,结合形态学及有关的细胞学和同工酶方面的资料,重新确立了Ｓｅｃｔ．Ｐｓｅｕｄｏ－Ｅｒｉｏｌｅｐｉｓ（Ｎａｋａｉ）Ｋｉｔａｍ．和Ｃ．ｓｅｇｅｔｕｍＢｇｅ．的组级和种级地位,最后,作者进一步讨论了光谱特征在化学分类中的意义。     

安息香科植物地理分布研究

安息香科植物共１２属,约１５０种,分布于亚洲和美洲的热带亚热带地区及欧洲南部的温暖地区。亚洲是现代安息香科植物的主要分布区,有１１个属,集中分布于中国南部和西南部附近。中国南岭山地及其附近汇集了８属２０多种,包括中国特有的陀螺果属、秤锤树属和长果安息香属以及东亚北美间断分布的银钟花属。这些呈星散分布的残余成分是从当地起源的。中国西南地区的安息香科植物仅云南一地就达８属３０余种,其中不少为局部分化形成的狭域分布特有种。这里是安息香科植物的分化中心,茉莉果属和歧序野茉莉属可能即是由此发端的。后者和安息香属经中南半岛一直分布到热带亚洲地区,并在马来西亚地区形成一次生分化中心。欧洲安息香科植物可能来自亚洲,并于第三纪得到发展。安息香科植物在欧洲的衰落,可能是遭到第四纪冰川严重破坏的结果。北美安息香科植物和欧亚大陆的有着共同起源,主要分布于东南部,并通过中美向南美发展。南美安息香科植物达５０余种,集中分布于亚马逊河流域。这里是安息香科植物的另一次生分化中心。特产巴西的花弄蝶属即是从当地分化出来的。