Toxicity and metabolism of endosulfan and its effect on oxygen consumption and total nitrogen excretion of the fish Macrognathus aculeatum

Experiments were conducted with the freshwater fish Macrognathus aculeatum to study the toxicity and metabolism of endosulfan and the effect of the pesticide on the oxygen consumption and total nitrogen excretion. The 96-hr LC₅₀ value was 3.5 ± 0.2 ppb. In brain, gills, gut, liver, and kidney, endosulfan was metabolized to endosulfan sulfate, but this appears to be only an intermediary step as the nontoxic endosulfan ether was found only in the liver and kidney, the principal organs of elimination of toxicants in fish. The pesticide, both at sublethal and lethal concentrations, decreased oxygen consumption and total nitrogen excretion.     

Effects of tobacco smoke inhaltion on the tracheo-bronchial microflora of ratsEffets de l'inhalation de fumée de tabac sur la flore tracheo-bronchiale de rats

The purpose of work was to study the effects of tobacco smoke on the airway flora in rats. A study on the regional distribution, total numbers and composition of the flora suggested the following: (a) Subacute smoke exposure intensified the penetration of the flora into deeper, normally sterile portions of the airways. (b) On smoking, the predominantly D. pneumoniae type flora of normal rats was found to shift to a form in which Hemophilus sp. was most frequent. (c) Exposure to low or high nicotine content cigarettes did not particularly modify these results.     

云南松苗木生长对追肥和IBA叶面喷施的响应

采用L₉(3⁴)正交设计（增加1个对照），进行根博士追肥和IBA叶面喷施对云南松苗木生长影响的试验。苗龄45 d时开始第1次追肥和叶面喷施激素。分别于苗龄90、135、180 d与225 d时测定其地径和苗高，255 d时测定主根长和一级侧根数。结果表明，苗龄225 d时，平均地径和苗高分别为1.46~2.02 mm和4.5~5.2 cm，测定时，主根长和一级侧根数分别为21.7~31.1 cm和8~12条·株^-1。除135 d和225 d外，其余各阶段地径与苗高均呈现极显著差异（P<0.01）。影响地径和主根长的主导因子是追肥频率，苗高和一级侧根数的则是根博士浓度；侧根与苗高协同生长，主根长与地径生长呈正相关。30 d追施1次300倍的根博士溶液与叶面喷施0.15 g·L^-1IBA溶液的组合促进苗木生长。试验根博士与IBA配合应用可防止云南松产生蹲苗现象。     

南京中山陵蜡梅资源及应用研究

通过对南京中山陵园蜡梅资源调查,介绍了中山陵园丰富的蜡梅品种资源及应用,重点叙述了新选育品种的优良特性.通过市场调查,分析了蜡梅目前应用的不足之处,并提出促进蜡梅应用开发主要措施及途径.     

广州中山纪念堂植物群落结构动态变化

2020年7月,采用野外实地普查法对广州市中山纪念堂植物群落进行调查,分析了树种组成、径阶结构、树高分布、健康状况等指标,并与1983年的历史数据进行对比分析,研究37年来该园植物群落结构动态变化。结果表明,1983—2020年:1)公园植物种类从26种增加到104种,乡土植物从17种增加到63种;2)乔木密度从17.1株/hm^(2)增加到202.1株/hm^(2),灌木密度从168.7株/hm^(2)增加到687.8株/hm^(2);3)胸径30 cm以下的乔木增长372株,胸径30~80 cm的乔木增长343株;4)幼林树木的占比上升,大树的占比下降,平均树高自13.9 m降至12.8 m;5)群落树木健康状况良好,健康树木数量占比超过98%。     

生长激素转基因家蝇的建立

利用显微注射技术，将人生长激素表达载体导入家蝇受精卵，人工孵化后收集子１、２代卵，提取染色体，经核酸探针及ＰＣＲ特异片段扩增检测，两代均为阳性。对整合阳性卵孵化至幼虫，热冲击诱导后立即进行表达检测，结果发现，人生长激素在蝇幼虫体内实现了表达，表达量最高可达４．０４μｇ／Ｌ。对转基因家蝇不同发育阶段的表型特征进行了观察，未发现明显变化     

Ovarian inhibition of pulsatile luteinizing hormone secretion in prepuberal holstein heifers

Fifteen prepuberal Holstein heifers were utilized to examine pulsatile luteinizing hormone (LH) secretion before and after ovariectomy. Heifers were ovariectornized at 3, 6 or 9 months of age (n=5/group) and scheduled for blood sampling at 1 week before, 1 week after and 4 weeks following ovariectomy. During each 8 hr sampling period (0600–1400 hr), blood samples (10 ml) were collected via indwelling jugular canulae at 10 min intervals. Prior to ovariectomy, mean plasma LH concentration and both number and amplitude of LH pulses per 8 hr sampling period were similar (P>.05) among age groups, and the absence of a pulsatile LH secretion profile was accompanied by a low mean LH concentration. Within 1 week after ovariectomy, both number of LH pulses and mean LH concentrations increased (P<.O1) in all age groups. Between 1 and 4 weeks after ovariectomy, both amplitude of LH pulses and mean LH concentrations increased (P<.O1) when the data from the three age groups were combined. We conclude that ovarian inhibition of pulsatile LH secretion is established by 3 months of age and is maintained through 9 months of age. In addition, the initial elevation mean plasma LH concentration is due to greater pulse frequency, while the subsequent rise in mean LH concentration reflects increased amplitude of LH pulses.     

孙中山先生对发展中国农业科学的见解

孙中山先生是中国民主主义革命的伟大先躯,在他的思想宝库中,科学立国占有很重要的地位,至今仍有现实意义.本文着重介绍他的农业科学思想.     

The effect of some Frescon analogs on the aquatic snail,Lymnaea stagnalis: III. Relation of some physical and chemical properties to neurotoxicity and molluscicidal effectiveness

The hydrolysis rates, particle sizes in suspension, and the relative lipophilicity of Frescon and its analogs were determined and compared with their neurotoxic and molluscicidal effectiveness. The hydrolysis rates of these compounds were closely correlated to their neurotoxicity, and, with one exception, to their molluscicidal effectiveness as well. The aberrant behavior of the one analog could not be attributed to a retarded penetration rate or an excessively large particle size in suspension. There appears to be some, as yet, unidentified factor which determines the molluscicidal activity of this analog. However, it is likely that both neurotoxicity and molluscicidal action are the result of a nucleophilic displacement reaction, although at different targets. Also, differences in the relative molluscicidal effectiveness of the Frescon analogs at different concentrations were possibly due to variations in particle size, which appears to be a function of the type and amount of emulsifier used.     

Toxicity in the brain of organophosphate insecticides: Comparison of the toxicities of metabolites with parent compounds using an intracerebral injection method

The toxicity in the brain of several parathion, fenthion, and fensulfothion insecticides and their toxic metabolites was determined by a technique of directly injecting the compounds into the region of the third ventricle of conscious mice, an area rich in cholinesterase activity. The results were compared on a body weight basis to the toxicity of these compounds when given by ip and oral routes. The results show that there is a direct relationship between the relative inhibition of cholinesterase activity in the brain by the organophosphates (e.g., methyl paraoxon, Sumioxon, and some members of the fenthion series) and the toxicity of these compounds in the brain. Methyl paraoxon and Sumioxon were found to be very toxic in the brain, Sumioxon being three to four times less toxic than methyl paraoxon. This is of the same order of effect of these compounds in inhibiting cholinesterases. It is concluded that any selective effects of Sumithion compared with methyl parathion must be due to the greater rate of metabolism of Sumithion to less toxic metabolites as well as to the lower toxicity of the oxon metabolite and not due to the relative rates of penetration of the toxic oxygen metabolites as previously suggested [J. Miyamoto, Agr. Biol. Chem.28, 422 (1964)]. A gas-liquid chromatographic method was employed to assess the distribution in the brain following intracerebral injection of the parathion-type compounds. The results suggest that there may be intracerebral metabolism of thionophosphates in vivo.