从害虫马尾松毛虫中提取甲壳素的初步研究

采用酸碱法对马尾松毛虫蛹中甲壳素的提取方法进行了初步研究。重点分析了N aOH不同处理条件对脱有机物质和甲壳素产率的影响,确定了从马尾松毛虫蛹中提取甲壳素的基本工艺:(1)脱矿物质:盐酸浓度为2.5%,浸泡时间为20 h,浸泡温度为30℃;(2)脱有机物质:N aOH浓度为6%,浸泡温度为75℃,浸泡时间为10 h;(3)脱色:双氧水浓度为9%,浸泡时间为2.5 h,浸泡温度为80℃。在此条件下,获得的甲壳素产品为白色粉状固体,其N含量为6.87%,灰分为1.19%,水分为8.37%。产率为29.97%。产品的N含量达到食品级甲壳素标准,灰分含量达到工业级甲壳素标准。实验有助于后续深入研究马尾松毛虫蛹中甲壳素的提取,也为今后进一步制备虫蛹壳聚糖打下了基础。     

Effect of a Single Dose of Cadmium on Pregnant Wistar Rats and their Offspring

Cadmium (Cd) is a well‐known toxicant targeting many organs, among them placenta. This heavy metal also has embryonary and foetal toxicity. This study was undertaken to analyse the effect of a single Cd dose administered at 4, 7, 10 or 15 days of gestation on the offspring of pregnant rats sacrificed at 20 days of gestation. Cadmium chloride was administered subcutaneously at 10 mg/kg body weight to Wistar pregnant dams; control animals received a proportionate volume of sterile normal saline by the same route. Maternal uteri, livers, kidneys and lungs, and foetuses were examined at necropsy. Samples of maternal organs and whole foetuses were collected for histopathologic examination, determination of Cd levels and staining by the Alizarin red S technique. Results revealed a clear embryotoxic and a teratogenic effect of this heavy metal, the former as a significant increase in the number of resorptions, and the latter as significant decrease of the gestational sac weight, and the size and weight of foetuses of Cd‐treated dams as well as induced malformations in skull bones, vertebrae and thoracic, and pelvian limbs. The deleterious effects found were similar to those previously reported for other animal models suggesting a high conservation of the pathogenic mechanisms of Cd. Additionally, many of the addressed aspects showed a slight dependence on the time of administration of the toxic that might be due to the accumulation of the metal in different organs, as we were able to demonstrate by the analysis of its concentration.     

Clay illuviation in Red Mediterranean soils

Theories regarding pedogenesis in Red Mediterranean soils have undergone several stages of development. The concept of clay illuviation in these soils was not a part of early theories and it is not yet unanimously accepted as a leading soil forming process. A methodology is presented for studying the illuviation of clay in these soils emphasizing typology of textural features and fabrics. The problem of age determination is also addressed, through the use of radiometric dates and correlation with archaeological artifacts. Clay illuviation in Red Mediterranean soils under present day environmental conditions suggests that it occurs presently only on humid and sub-humid margins of the Mediterranean basin. Elsewhere illuvial clay accumulations are inherited from Interglacial periods. Red Mediterranean soils during glacial periods were eroded, colluviated, aggraded with aeolian dust, calcitic fraction of which was redistributed in form of calcitic features and eventually were affected by water logging. An example of water logging of Red Mediterranean soils (Mamora, Morocco) which took place during the last Glacial cycle, consists of yellow illuvial clays accompanied by a yellowing of the ground mass. During earlier cycles water logging resulted in whitish grey stains in which hydromorphic textural features were deposited.     

Alteration meteorique des biotites en algerie

The authors compared the weathering of biotite on different morphological surfaces of the granitic outcroprs of Beni-Toufout (northeast Algeria), using the polarizing microscope, scanning electron microscope and microprobe, and mineralogical analysis.On the youngest surfaces, the optical and crystallographic characters of biotites are preserved, except on edges where folding appears accompanied by loss of pleochroism and birefringence and by ferruginisation. At this stage biotites are still composed of 10-Å minerals with interstratified ones at the edges.In the next stage of weathering, folding affects the whole mineral. Meta-halloysite appears at this stage.Then the weathering proceeds by developmental of “brushes” at ends of minerals and by development of folding, creating large cavities in the mineral, some filled with argillans and other with kaolinite. Mineralogical analysis shows an increase of kaolinite but 10-Å vermiculite and interstratified minerals are still present.The next step consists of a progressive increase of kaolinite and ferruginistation. Cavitation of minerals has become important, but small flakes of unweathered biotite can still be found.In the extreme stage of weathering, the mineral is colorless gray under crossed nicols; its flakes are outlined by ferruginisation. Internal cavities are partially filled with argillans. Mineralogical analysis shows only kaolinite and ferruginous compounds. In this extreme weathering, two subtypes of weathered biotites were observed, one characterized by total kaolinisation with a weak internal cavitation and the second by a very strong internal cavitation and a dominance of ferruginous compounds.The weathering of biotites in Beni-Toufout is intermediate between the temperate forms and those from the tropics. As in Europe, weathering is progressive with a vermiculite stage present but much less developed. As in the tropics, weathering leads to a kaolinisation of biotites.     

Comparative micromorphology of two late Pleistocene paleosols (in the Paris Basin)

The micromorphology of two late Pleistocene paleosols in the Paris Basin, St. Pierre-les-Elbeuf and Bois du Moulin were studied in order to characterize their pedogenicand sedimentary processes and to reconstruct and interpret the pedosedimentary history and climate of each profile. The micromorphological observations of greatest interpretive value were the types of clayey and silty textural accumulations (argillans and siltans), pedality and porosity; of lesser value were papules, bioactivity and concretions.During the last interglacial period on both profiles developed a sol brun lessivé, comparable to those developed during the Holocene. With the onset of cold conditions of the last Glaciation, the two differentiate pedologically and sedimentologically. At Elbeuf, in the Seine Valley, we observe colluviation of silts and the development of grey forest soils with strong textural degradation under cold and moderately dry local conditions. At Moulin, on the plateau the grey forest phase is very weak and probably brief and is followed by a marked phase of churning and eluviation of silt; conditions were wetter than in the valley, such that the upland position protected the profile from colluvial truncation.The advantages of micromorphology in interpreting pedo-sedimentary sequences is discussed.