蛇根草水培体系中喜树碱、金丝桃苷及其他组分的初步鉴定

采集广东肇庆市鼎湖山的野生型广州蛇根草,进行室内水培优化,并初步构建了广州蛇根草水培体系.采用HPLC和GC-MS技术分析鉴定根部分泌物中的喜树碱、金丝桃苷以及其他成分.结果表明:广州蛇根草水培体系需建立在无强阳光直射,温度适宜(18～25℃)的条件下.利用大孔树脂AB-8吸附结合固相萃取技术富集根系分泌液,以石油醚/乙酸乙酯(6∶4)为洗脱液进行柱色谱分离,获得浓缩液经HPLC检测含有喜树碱和金丝桃苷,表明广州蛇根草根系分泌物中存在喜树碱和金丝桃苷,同时GC-MS鉴定分析表明广州蛇根草根系分泌物中还含有各种热稳定的化感物质,如邻苯二甲酸二丁酯和苯二甲酸,单(2-乙基己基)酯等化合物.本研究初步表明通过构建蛇根草水培体系,以其根系生物合成喜树碱和金丝桃苷有一定的可行性.     

Epizootics of sudden death in tammar wallabies (Macropus eugenii) associated with an orbivirus infection

Epizootics of sudden death in tammar wallabies (Macropus eugenii) occurred at six research facilities and zoological gardens in New South Wales, Australia, in late 1998 and at one Queensland research facility in March 1999. There were 120 confirmed tammar wallaby deaths during this period; however, population censuses indicated that up to 230 tammar wallabies may have died. The majority of animals died without premonitory signs. A small proportion of wallabies exhibited increased respiratory rate, sat with a lowered head shortly before death or were discovered in lateral recumbency, moribund and with muscle fasciculations. Gross postmortem findings consistently included massive pulmonary congestion, mottled hepatic parenchyma and subcutaneous oedema throughout the hindlimbs and inguinal region. Approximately 30% of the animals examined also had extensive haemorrhage within the fascial planes and skeletal muscle of the hindlimb adductors, inguinal region, ventral thorax, dorsal cervical region and perirenal retroperitoneal area. The tissues of affected animals became autolytic within a short period after death. Bacteriological examination of tissues from 14 animals did not provide any significant findings. Toxicological examination of the gastric and colonic contents of four animals did not reveal evidence of brodifacoume or other rodenticides. Viruses from the Eubenangee serogroup of the Orbivirus genus were isolated from the cerebral cortex of nine, and the myocardium of two, tammar wallabies and the liver and intestine of another tammar wallaby. A similar orbivirus was also isolated from the cerebrospinal fluid of another tammar wallaby that died suddenly. The disease agent appears to be a previously unrecognised orbivirus in the Eubenangee serogroup. This is the first report of epizootics of sudden deaths in tammar wallabies apparently associated with an orbivirus infection.     

Equine neonatal thoracic and abdominal ultrasonography.

Pathologic disorders of the equine neonate often develop shortly after foaling as a result of prematurity, dystocia, trauma, or septicemia. Recognition of these disorders requires routine patient assessment along with diagnostic aids, including abdominal and thoracic ultrasonography. Fortunately, modern technology affords today's equine practitioners the opportunity to use ultrasonography to advance their practice, and it is the authors' hope that this article might help in those efforts.     

Earthquakes on dipping faults: the effects of broken symmetry

Dynamic simulations of earthquakes on dipping faults show asymmetric near-source ground motion caused by the asymmetric geometry of such faults. The ground motion from a thrust or reverse fault is larger than that of a normal fault by a factor of 2 or more, given identical initial stress magnitudes. The motion of the hanging wall is larger than that of the footwall in both thrust (reverse) and normal earthquakes. The asymmetry between normal and thrust (reverse) faults results from time-dependent normal stress caused by the interaction of the earthquake-generated stress field with Earth's free surface. The asymmetry between hanging wall and footwall results from the asymmetric mass and geometry on the two sides of the fault.     

A Magnetic Signature at Io: Initial Report from the Galileo Magnetometer

During the inbound pass of the Galileo spacecraft, the magnetometer acquired 1 minute averaged measurements of the magnetic field along the trajectory as the spacecraft flew by Io. A field decrease, of nearly 40 percent of the background jovian field at closest approach to Io, was recorded. Plasma sources alone appear incapable of generating perturbations as large as those observed and an induced source for the observed moment implies an amount of free iron in the mantle much greater than expected. On the other hand, an intrinsic magnetic field of amplitude consistent with dynamo action at Io would explain the observations. It seems plausible that Io, like Earth and Mercury, is a magnetized solid planet.