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991.
皖南、赣北奥陶纪笔石立体标本形成环境的初步研究* 总被引:1,自引:0,他引:1
皖南、赣东北和赣西北地区奥陶纪笔石地层发育良好,笔石化石丰富。宁国组和胡乐组均为笔石相地层,但笔石的保存特点并不相同。立体保存的黄铁矿化笔石标本主要见于宁国组,而胡乐组的笔石几乎均为薄膜标本。在比较宁国组和胡乐组在岩性、颜色、化石、矿物和元素等方面的特点后发现,两者有较明显的差异。这表明宁国组和胡乐组形成时的环境是不同的,前者为弱还原环境,后者为较强的还原环境,而在研究区内影响笔石体立体保存的主要因素为还原环境和较高的铁含量。在还原环境下,铁可呈Fe~(2+)存在,笔石体内含有硫,死亡后经降解作用可生成H_2S;H_2S和Fe~(2+)结合可使笔石体黄铁矿化,从而使笔石体硬化而呈立体保存下来。宁国组的铁含量明显高于胡乐组,这似可以解释宁国组产有较多笔石立体标本的原因。 相似文献
992.
Bart M. Nicolaï Jan F. Van Impe Peter A. Vanrolleghem Joos Vandewalle 《Antonie van Leeuwenhoek》1992,62(4):273-283
The mathematical model for the penicillin G fed-batch fermentation proposed by Heijnen et al. (1979) is compared with the model of Bajpai & Reuß (1980). Although the general structure of these models is similar, the difference in metabolic assumptions and specific growth and production kinetics results in a completely different behaviour towards product optimization. A detailed analysis of both models reveals some physical and biochemical shortcomings. It is shown that it is impossible to make a reliable estimation of the model parameters, only using experimental data of simple constant glucose feed rate fermentations with low initial substrate amount. However, it is demonstrated that some model parameters might be key factors in concluding whether or not altering the substrate feeding strategy has an important influence on the final amount of product.It is illustrated that feeding strategy optimization studies can be a tool in designing experiments for parameter estimation purposes. 相似文献
993.
Ian A. Graham Laura M. Smith Christopher J. Leaver Steven M. Smith 《Plant molecular biology》1990,15(4):539-549
The cucumber malate synthase (MS) gene, including 1856 bp of 5 non-trnascribed sequence, has been transferred into Petunia (Mitchell) and Nicotiana plumbaginifolia plants using an Agrobacterium binary vector. The transferred gene is found in variable copy number in different transformants, and is stably transmitted in each case as a single Mendelian character. Transgene mRNA accumulates in the seedling during the first three days of germination, then declines in amount as the cotyledons emerge from the seed. The decline is more pronounced in light-grown seedlings than in dark-grown seedlings. Expression of the MS transgene is also detected at a low level in petals of transformed Petunia plants. In these respects the pattern of MS gene expression is similar in cucumber and in trnasformed plants, showing that the transferred DNA fragment contains a functional MS gene. A 1076 bp fragment of 5 sequence was linked to the -glucuronidase reporter gene and transferred into Nicotiana, where it was shown to direct temporal and spatial patterns of expression similar to that of the complete MS gene. However, histochemical localisation of -glucuronidase activity demonstrated that the chimaeric gene is expressed not only in cotyledons of transgenic plants, but also in endosperm and some hypocotyl cells during early germination. The relevance of these findings to the control of malate synthase gene expression is discussed. 相似文献
994.
Northern blot analysis revealed that a single 4.2 kb phytochrome mRNA species was detectable in cotyledons excised from five-day-old etiolated cucumber seedlings. Intact etiolated five-day-old cucumber seedlings were given a red light or benzyladenine treatment, and cotyledons were harvested at various times following treatment. The abundance of phytochrome mRNA in the cotyledons was quantitated using 32P-labeled RNA probes and slot blot analysis. By 2 h after irradiation the phytochrome mRNA level was reduced to 40% of the initial abundance and reaccumulation began by 3 h after irradiation. Reaccumulation of phytochrome mRNA to the time-zero dark control level was achieved by 10 h after treatment. A decrease in phytochrome mRNA abundance was evident by 2 h after benzyladenine treatment, and a maximal reduction to 45% of the time-zero dark control was attained by 4 h after treatment. No recovery of the phytochrome mRNA level was evident by 8 h after benzyladenine treatment. The abundance of actin mRNA was unaffected by benzyladenine treatment. 相似文献
995.
Characterization of a pollen-specific gene family from Brassica napus which is activated during early microspore development 总被引:13,自引:0,他引:13
Diego Albani Laurian S. Robert Pauline A. Donaldson Illimar Altosaar Paul G. Arnison Steven F. Fabijanski 《Plant molecular biology》1990,15(4):605-622
In this paper we describe the isolation and characterization of a genomic clone (Bp4) from Brassica napus which contains three members of a pollen-specific multigene family. This family is composed of 10 to 15 closely related genes which are expressed in early stages of microspore development. The complete nucleotide sequence of the clone Bp4 and of three homologous cDNA clones is reported. One of the genes (Bp4B) contained in the genomic clone is believed to be non-functional because of sequence rearrangements in its 5 region and intron splicing sites. The remaining genes (Bp4A and Bp4C), as well as the cDNA clones, appear to code for small proteins of unique structure. Three different types of proteins can be predicted as a result of the deletion of carboxy or amino terminal portions of a conserved core protein. These proteins all share a common alternation of hydrophobic and hydrophilic domains. A fragment of the genomic clone containing the gene Bp4A, as well as the non-functional gene Bp4B, was introduced into tobacco plants via Agrobacterium-mediated transformation. The functional gene Bp4A is expressed in transgenic tobacco plants and shows spatial and temporal regulation consistent with the expression patterns seen in Brassica napus. 相似文献
996.
Versieck Jacques Vanballenberghe Lidia Wittoek Ann Vermeir Gerda Vandecasteele Carlo 《Biological trace element research》1990,(1):683-689
A method is described for the determination of mercury in human blood serum and packed blood cells employing neutron activation
analysis. Great attention was devoted to the collection and manipulation of the samples. The accuracy and precision of the
method were tested by analyzing biological reference materials and by comparing the concentrations measured in a number of
serum samples to those obtained by another, independent technique (cold vapor atomic absorption spectrometry) in the same
samples. The article reports the levels measured in blood serum and packed blood cells samples from 15 adult volunteers, as
well as the figures determined in a “second-generation” biological reference material (freeze-dried human serum), prepared
and conditioned at the University of Ghent. 相似文献
997.
Multivariate statistical analysis has been applied to time series measurements of aerosol elemental composition from PIXE
analysis of filter samples, and principal components have been resolved that represent distinct particle types in an external
mixture in the atmosphere. In this study, it is argued that a combination of chemical and statistical analyses of the data
may be more powerful in determining chemical species in atmospheric aerosols than studies that employ mainly direct chemical
analysis of chemical species in unresolved mixtures of aerosol particle samples. Sulfur is generally associated with mineral
dust elements. It is reasoned that the association may represent sulfuric acid coatings on particles that can lead to mineral
dissolution and solubilization of significant amounts of aluminum, iron, and other metals.
Upon wet or dry deposition to the surface, the fluxes of these metals in biologically-available form may be sufficient to
affect primary productivity in the world ocean and cause ecological damage in lakes. As a consequence, the fluxes of biogenic
trace gases to the atmosphere may be changed, possibly leading to changes in the tropospheric concentration of ozone. The
inputs to lakes of soluble aluminum, which is toxic to fish, may be partly by deposition directly from the atmosphere, thus
not limited to leaching of soils by acid deposition. Human inhalation of soluble aluminum and other solulilized mineral metals
may account, in part, for the observed geographic pattern of deaths attributed to chronic obstructive pulmonary disease (COPD)
that show high rates in cities of the Western US and the southeast region, but low in most of the midwest and northeast. 相似文献
998.
Krishnan S. S. McNeill K. G. Mernagh J. R. Harrison J. E. 《Biological trace element research》1990,(1):415-421
Two new facilities for in vivo activation analysis of patients have been designed, developed, and constructed at Toronto General
Hospital. One of these is for the determination of body calcium for the diagnosis of osteoporosis and other diseases associated
with bone loss. The other is for the measurement of total body nitrogen for the determination of protein status.
These facilities replace old university facilities and take into account the comfort and management of patients. In addition,
in the case of the calcium facility, the precision of the measurements has been improved because of larger detector volume
and increased neutron source strength. Both the facilities are now in routine hospital clinical use. 相似文献
999.
Edward J. B. Beeley P. A. Bennett L. G. I. Poland J. S. 《Biological trace element research》1990,(1):53-61
A microcomputer-controlled irradiation and measurement system and a microprocessor-controlled sample changer have been installed
at the SLOWPOKE-2 Facility at the Royal Military College of Canada (RMC). These systems can provide the gamut of instrumental
neutron activation analysis (INAA) techniques for the analyst. Custom software has been created for system control, data acquisition,
and off-line spectral analysis using programs that incorporate Gaussian peak-fitting methods of analysis. The design and use
of the equipment is discussed, and the performance is illustrated with results obtained from the analysis of marine sediment
and biological reference materials. 相似文献
1000.
Localized transient expression of GUS in leaf discs following cocultivation with Agrobacterium 总被引:15,自引:0,他引:15
A chimaeric gene has been constructed that expresses -D-glucuronidase (GUS) in transformed plant tissues, but not in bacterial cells. This gene has proved extremely useful for monitoring transformation during the period immediately following gene transfer from Agrobacterium tumefaciens. GUS expression was detectable 2 days after inoculation, peaked at 3–4 days and then declined; if selection was imposed expression increased again after 10–14 days. The extent of transient expression after 4 days correlated well with stable integration as measured by kanamycin resistance, hormone independence, and gall formation. Histochemical staining of inoculated leaf discs confirmed the transient peak of GUS expression 3–4 days after inoculation. The most surprising result was that the blue staining was concentrated in localized zones on the circumference of the disc; within these zones, essentially all the cells appeared to be expressing GUS. We suggest that the frequency of gene transfer from Agrobacterium is extremely high within localized regions of leaf explants, but that the frequency of stable integration is several orders of magnitude lower. 相似文献