Effects of prenatal X-irradiation: studies on the mechanism of X-irradiation-induced inhibition of microsomal enzyme development in rat liver

Exposure of pregnant rats to 25 R of x-irradiation on the fourteenth gestation day has produced in the male offspring an impairment of the development of the hepatic microsomal enzyme system which metabolizes hexobarbital. However, irradiation did not suppress the increase of enzyme activity brought about by the administration of chemical inducers (pheno-barbital). Actinomycin, on the other hand, inhibited to varying degrees both the ontogenic and phenobarbital-induced increases in enzyme activity. The effects on the enzyme system have been supported by in vivo measurements of the duration of hexobarbital hypnosis. The ontogenic increase in enzyme activity is hormone-dependent, while that following phenobarbital administration is independent of hormonal regulation as evidenced by the response in hypophysectomized or sexually immature animals. It is concluded from these results that the inhibitory effect of x-irradiation on the hepatic enzyme system is mediated through an action on the hormonal regulation of enzyme activity. Evidence for this hypothesis is discussed.     

SARCOCYSTIS MURIS BLANCHARD BEI EINER MICROTUSART

Aus dem umfangreichen Material der oben angef(?)hrten Sammelreise erhielt ich von Herrn Dr. R. Piechocki eine in einer Schlagfalle gefangene, bereits entpelzte Microtusart. Die Bestimmung ergab Microtus maximowiczii Schrenk. Pr(?)ft man die Literatur (?)ber Sarcosporidienbefall nach, so findet man bis     

不用土壤栽培黄瓜

德湼泊彼德罗夫卡尔拉李布克湼特温室综合制造工厂从1957年1月在没有土壤的砂砾和水中栽培黄瓜和蕃茄。这种栽培方法,具有很大的经济意义:它不需要更换土壤,并有力地防止了线虫的的虫瘿。此外,植物的营养面积可以降低1—2倍,能保证获得较高的产量和适当地减低蔬菜的成本。     

癌基因产物的第一张肖象

以California大学Berkeley分校Sung-Hou Kim研究组为主发表的文章,被视作为癌基因作用研究上的一个里程碑。Kim及其同事报道了有关ras癌基因家族中的一个成员所编码的一种蛋白质的三维结构。“这是第一个被确定了结构的癌基因蛋白质”,Kim说,“由此提供了认识ras基因生物功能的结构基础”。     

免疫健全鼠和免疫缺陷鼠对致死性汉坦病毒感染不同的敏感性与抵抗力

本文研究了不同鼠龄的免疫健全(mu/ )和先天性T细胞缺陷(nu/nu)CD—1鼠对致死性汉坦病毒脑膜脑炎的敏感性与抵抗力。nu/ 鼠对致死性感染的敏感性取决于鼠龄。生后一周鼠脑内接种汉坦病毒76一118株,死亡率为100%;接种9日龄鼠,死亡率60%;接种14～42日龄鼠则不发病死亡。接种的nu/ 鼠,5和7日龄比生后24小时鼠死亡发生时间明显提前。同龄组nu/nu鼠在鼠龄与生存时间之间无类似的逆相关。然而,14日龄或更大龄的鼠尽管发病和死亡的时间延长,但仍是敏感的。接种的7日龄nu/ 鼠和7、9、14日龄nu/nu鼠的脑内病毒滴度近乎一样。较大龄鼠尽管病毒滴度峰值相对较低,但似乎不受中和抗体反应的影响。接种的一周龄nu/ 鼠比接种的新生鼠死得快,断奶nu/ 鼠与nu/nu鼠对汉坦病毒脑膜脑炎的抵抗力不同,这表明细胞免疫对疾病的发展与恢复起作用。     

Diurnal Rhythmicity in the Pattern of mRNAs in the Leaves of Sinapis alba

Previous studies have shown that certain specific leaf mRNAs exhibit a diurnal rhythmicity in their quantity in higher plants. To determine whether this situation is restricted to a few mRNAs, or affects a large number, we have used in vitro translation and two-dimensional polyacrylamide gel electrophoresis to analyze the mRNA complement in leaves of Sinapis alba at different times during an 8-hour/16-hour day/night cycle. A method for the visual analysis of two-dimensional polyacrylamide gel electrophoresis was also developed. This method selected, at each sampling time, spots that were significant. It then selected, between two sampling times, intensity changes that were significant at the 0.02 confidence level. During a day/night cycle, complex rhythmic changes affected about 10% of the mRNAs. Nineteen different rhythm patterns were found. These 19 patterns fell into four main classes: mRNAs that increase during the light period and decrease during the dark, mRNAs that increase and then decrease during the light period, mRNAs that decrease during the light period and increase during the dark period, and mRNAs that increase and then decrease during the dark period.     

Emission of volatile sulfur compounds from spruce trees

Spruce (Picea Abies L.) trees from the same clone were supplied with different, but low, amounts of plant available sulfate in the soil (9.7-18.1 milligrams per 100 grams of soil). Branches attached to the trees were enclosed in a dynamic gas exchange cuvette and analyzed for the emission of volatile sulfur compounds. Independent of the sulfate supply in the soil, H₂S was the predominant reduced sulfur compound continuously emitted from the branches with high rates during the day and low rates in the night. In the light, as well as in the dark, the rates of H₂S emission increased exponentially with increasing water vapor flux from the needles. Approximately 1 nanomole of H₂S was found to be emitted per mole of water. When stomata were closed completely, only minute emission of H₂S was observed. Apparently, H₂S emission from the needles is highly dependent on stromatal aperture, and permeation through the cuticle is negligible. In several experiments, small amounts of dimethylsulfide and carbonylsulfide were also detected in a portion of the samples. However, SO₂ was the only sulfur compound consistently emitted from branches of spruce trees in addition to H₂S. Emission of SO₂ mainly proceeded via an outburst starting before the beginning of the light period. The total amount of SO₂ emitted from the needles during this outburst was correlated with the plant available sulfate in the soil. The diurnal changes in sulfur metabolism that may result in an outburst of SO₂ are discussed.