Among the enzymes involved in carotenoid biosynthesis, phytoene desaturase is considered to be a rate-limiting enzyme in this pathway and is also the target of many bleaching herbicides. This enzyme shows diversity concerning its function and amino acid homology among various organisms. The phytoene desaturase gene crtl of Erwinia uredovora was expressed, the 5'-region of which was fused to the sequence for the transit peptide of a pea Rubisco small subunit, in tobacco plants under the control of the CaMV 35S promoter. This chimeric gene product was targeted into chloroplasts and processed in the transgenic plants. The production and processing of the corresponding protein could be demonstrated by Western blotting. Immunogold localization showed that the location of the gene product Crtl was preferentially in the thylakoids. A radioactive labeling study using the leaves demonstrated enhanced activity for the synthesis of β-carotene. In addition, the transgenic tobacco acquired elevated resistance to the bleaching herbicide norflurazon. 相似文献
Type B aortic dissection (TBAD) carries a high risk of complications, particularly with a partially thrombosed or patent false lumen (FL). Therefore, uncovering the risk factors leading to FL thrombosis is crucial to identify high-risk patients. Although studies have shown that morphological parameters of the dissected aorta are related to FL thrombosis, often conflicting results have been reported. We show that recent models of thrombus evolution in combination with sensitivity analysis methods can provide valuable insights into how combinations of morphological parameters affect the prospect of FL thrombosis. Based on clinical data, an idealized geometry of a TBAD is generated and parameterized. After implementing the thrombus model in computational fluid dynamics simulations, a global sensitivity analysis for selected morphological parameters is performed. We then introduce dimensionless morphological parameters to scale the results to individual patients. The sensitivity analysis demonstrates that the most sensitive parameters influencing FL thrombosis are the FL diameter and the size and location of intimal tears. A higher risk of partial thrombosis is observed when the FL diameter is larger than the true lumen diameter. Reducing the ratio of the distal to proximal tear size increases the risk of FL patency. In summary, these parameters play a dominant role in classifying morphologies into patent, partially thrombosed, and fully thrombosed FL. In this study, we point out the predictive role of morphological parameters for FL thrombosis in TBAD and show that the results are in good agreement with available clinical studies.
Investigations of the reproductive biology of Cyclops vicinusrevealed that mated females oscillate between gravid and nongravidreproductive conditions. The gravid condition can be dividedin two recognizable phases: gravid/nonovigerous and gravid/ovigerous,the former phase being shortest. The maturation of new oocytestakes place when the old egg sacs are still being carried; thisensures a rapid clutch succession. Females which remain unmated,extrude few eggs, in no case complete egg sacs, and remain gravidthus conserving oocytes. Females which mate only once, showa similar reproductive pattern (clutch size and clutch succession)to those which remain combined with males, and thus have theopportunity to remate, but tend to produce fewer clutches. Malesare able to fertilize 34 females day1. Matingcapacity of males is possibly limited by the time needed tofill a new spermatophore. Short-term starvation (5 days) lengthenedclutch-to-clutch periods and diminished clutch size. When thestarvation period started in the gravid/ovigerous phase, a normalclutch was extruded but no new oocytes matured during starvation,indicating that the energy for egg maturations is provided inthe first part of the reproductive cycle. 相似文献
With regards to pollination there exist several mutualistic relationships between Hadena -species and Caryophyllaceae. As mutualists have both negative and positive effects on their partners, mutualism is often betoken as reciprocative exploitation which may shift to parasitism if the exploitation of one partner becomes prevalent. Several Silene - and Saponaria -species are considered to be larval host plants of Hadena bicruris . Although Silene latifolia ssp. alba and S. dioica are frequently cited as hosts of the seed eating larvae, field and laboratory observations at Ulm were suggestive for only S. latifolia ssp. alba being a suitable host. Records of the oviposition behavior of H. bicruris made it evident that in fact a considerable number of eggs could be found in planted stands of both species. On the other hand, phenological data of the flowering periods and of the oviposition behavior of H. bicruris showed that S. latifolia ssp. alba is clearly preferred for oviposition if host selection is possible due to contemporaneous flowering of individuals of both plant species growing at close range. In addition, the flowering periods of S. latifolia ssp. alba and the periods of moth activity overlap to a large extent. This is not the case in S. dioica . Feeding experiences first indicated that the caterpillars may not prefer one of the species to the other, but comparison of the pupal weight of the animals reared on fruits of exclusively one of the species showed that the seeds of S. latifolia ssp. alba were more profitable for nutrition than those of S. dioica ; the pupal weight of animals reared on seeds of the former species significantly exceeded that of animals reared on seeds of the latter one. The question arises if the symbiosis of H. bicruris and its hosts constitutes a stable situation or if an evolutionary shift to mutualism or parasitism will take place. 相似文献
Lactate dehydrogenase (LDH), an ubiquitous enzyme among vertebrates, invertebrates, plants and microbes was discovered in the early period of enzymology. The enzyme has been dissolved in several distinguishable molecular forms. In mammals, three types of subunits encoded by the genes Ldh-A, Ldh-B and Ldh-C give rise to a selected number of tetrametric isoenzymes. LDH-A4, LDH-B4 and the mixed hybrid forms of the A- and B-subunits are present in many tissues but with certain distribution patterns. LDH-C4 is confined in mammals to testes and sperm. Numerous techniques have been employed to purify, characterize and separate the different forms of the enzyme. This report deals with the main protocols and procedures of purification of LDH and its isoenzymes including chromatographic and electrophoretic methods, partitioning in aqueous two-phase systems and precipitation approaches. In particular, affinity separation techniques based on natural and pseudo-biospecific ligands are described in detail. In addition, basic physico-chemical and kinetic properties of the enzyme from different sources are summarized. In a second part, the clinical significance of the determination of LDH in diverse body fluids in respect to the total activity and the isoenzyme distribution in different organs is discussed. 相似文献