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1.
Abstract. Contrary to current assumptions, the reflex blood of two-spot ladybirds, Adalia bipunctata , and seven-spot ladybirds, Coccinella septempunctata , contains haemocyte-like cells. Furthermore, DNA can be extracted and amplified from coccinellid reflex blood, confirming the presence of haemocyte-like cells and demonstrating a nondestructive method of DNA extraction. 相似文献
2.
Thomas Jahns Alexandra Zobel Diethelm Kleiner Heinrich Kaltwasser 《Archives of microbiology》1988,149(5):377-383
Evidence for the existence of an energy-dependent urea permease was found for Alcaligenes eutrophus H16 and Klebsiella pneumoniae M5a1 by studying uptake of 14C-urea. Since intracellular urea was metabolized immediately, uptake did not result in formation of an urea pool. Evidence is based on observations that the in vivo urea uptake and in vitro urease activity differ significantly with respect to kinetic parameters, temperature optimum, pH optimum, response towards inhibitors and regulation. The K
m for urea uptake was 15–20 times lower (38 M and 13 M urea for A. eutrophus and K. pneumoniae, respectively) than the K
m of urease for urea (650 M and 280 M urea), the activity optimum for A. eutrophus was at pH 6.0 and 35°C for the uptake and pH 9.0 and 65°C for urease. Uptake but not urease activity in both organisms strongly decreased upon addition of inhibitors of energy metabolism, while in K. pneumoniae, potent inhibitors of urease (thiourea and hydroxyurea) did not affect the uptake process. Significant differences in the uptake rates were observed during growth with different nitrogen sources (ammonia, nitrate, urea) or in the absence of a nitrogen source; this suggested that a carrier is involved which is subject to nitrogen control. Some evidence for the presence of an energy-dependent uptake of urea was also obtained in Pseudomonas aeruginosa DSM 50071 and Providencia rettgeri DSM 1131, but not in Proteus vulgaris DSM 30118 and Bacillus pasteurii DSM 33.Non-standard abbreviations CCCP
Carbonylcyanide-m-chlorphenylhydrazone
- DCCD
dicyclohexylcarbodiimide
- DNP
2,4-dinitrophenole 相似文献
3.
It is now generally recognized that cell growth conditions in nature are often suboptimal compared to controlled conditions provided in the laboratory. Natural stresses like starvation and acidity are generated by cell growth itself. Other stresses like temperature or osmotic shock, or oxygen, are imposed by the environment. It is now clear that defense mechanisms to withstand different stresses must be present in all organisms. The exploration of stress responses in lactic acid bacteria has just begun. Several stress response genes have been revealed through homologies with known genes in other organisms. While stress response genes appear to be highly conserved, however, their regulation may not be. Thus, search of the regulation of stress response in lactic acid bacteria may reveal new regulatory circuits. The first part of this report addresses the available information on stress response in Lactococcus lactis.Acid stress response may be particularly important in lactic acid bacteria, whose growth and transition to stationary phase is accompanied by the production of lactic acid, which results in acidification of the media, arrest of cell multiplication, and possible cell death. The second part of this report will focus on progress made in acid stress response, particularly in L. lactis and on factors which may affect its regulation. Acid tolerance is presently under study in L. lactis. Our results with strain MG1363 show that it survives a lethal challenge at pH 4.0 if adapted briefly (5 to 15 minutes) at a pH between 4.5 and 6.5. Adaptation requires protein synthesis, indicating that acid conditions induce expression of newly synthesized genes. These results show that L. lactis possesses an inducible response to acid stress in exponential phase.To identify possible regulatory genes involved in acid stress response, we determined low pH conditions in which MG1363 is unable to grow, and selected at 37°C for transposition insertional mutants which were able to survive. About thirty mutants resistant to low pH conditions were characterized. The interrupted genes were identified by sequence homology with known genes. One insertion interrupts ahrC, the putative regulator of arginine metabolism; possibly, increased arginine catabolism in the mutant produces metabolites which increase the pH. Several other mutations putatively map at some step in the pathway of (p)ppGpp synthesis. Our results suggest that the stringent response pathway, which is involved in starvation and stationary phase survival, may also be implicated in acid pH tolerance. 相似文献
4.
Luís C. Duarte Alexandra P. Nobre Francisco M. Gírio M. T. Amaral-Collaço 《Biotechnology Techniques》1994,8(12):859-864
Summary The kinetic parameters of the yeastDebaryomyces hansenii grown in continous cultivation on D-xylose were determined by different methods. While the values obtained for μm by the steady state and the washout methods only gave a 3% difference, the determined Ks values by the steady state and the maximal biomass output methods led a to a 305% difference. The latter method was suggested
to overestimate the Ks value. 相似文献
5.
Kevin M. Brindle Alexandra M. Fulton Simon-Peter Williams 《Journal of molecular recognition : JMR》1993,6(4):159-165
Models of metabolic flux regulation are frequently based on an extrapolation of the kinetic properties of enzymes measured in vitro to the intact cell. Such an extrapolation assumes a detailed knowledge of the intracellular environment of these enzymes in terms of their free substates and effectors concentrations and possible interaction with other cellular macromolecules, which may modify their kinetic properties. These is a considerable incentive, therefore, to study the properties of enzymes directly in vivo. We have been using non-invasive NMR techniques, in conjunction with molecular genetic manipulation of enzyme levels, to study the kinetic properties of individual enzymes in vivo. We have also developed a novel strategy which has allowed us to monitor, by NMR, the ligand binding properties and mobilities of enzymes in the intact cell. This technique may also allow us to measured the diffusion coefficients of these proteins in the cell. These studies should give new insight into the properties of enzymes in vivo 相似文献
6.
Yaoyu Ren Timo Danner Alexandra Moy Martin Finsterbusch Tanner Hamann Jan Dippell Till Fuchs Marius Müller Ricky Hoft André Weber Larry A. Curtiss Peter Zapol Matthew Klenk Anh T. Ngo Pallab Barai Brandon C. Wood Rongpei Shi Liwen F. Wan Tae Wook Heo Martin Engels Jagjit Nanda Felix H. Richter Arnulf Latz Venkat Srinivasan Jürgen Janek Jeff Sakamoto Eric D. Wachsman Dina Fattakhova-Rohlfing 《Liver Transplantation》2023,13(1):2201939
The garnet-type phase Li7La3Zr2O12 (LLZO) attracts significant attention as an oxide solid electrolyte to enable safe and robust solid-state batteries (SSBs) with potentially high energy density. However, while significant progress has been made in demonstrating compatibility with Li metal, integrating LLZO into composite cathodes remains a challenge. The current perspective focuses on the critical issues that need to be addressed to achieve the ultimate goal of an all-solid-state LLZO-based battery that delivers safety, durability, and pack-level performance characteristics that are unobtainable with state-of-the-art Li-ion batteries. This perspective complements existing reviews of solid/solid interfaces with more emphasis on understanding numerous homo- and heteroionic interfaces in a pure oxide-based SSB and the various phenomena that accompany the evolution of the chemical, electrochemical, structural, morphological, and mechanical properties of those interfaces during processing and operation. Finally, the insights gained from a comprehensive literature survey of LLZO–cathode interfaces are used to guide efforts for the development of LLZO-based SSBs. 相似文献
7.
THE SARCOTUBULAR SYSTEM OF FROG SKELETAL MUSCLE : A Morphological and Biochemical Study 总被引:6,自引:20,他引:6 下载免费PDF全文
U. Muscatello Ebba Andersson-Cedergren G. F. Azzone Alexandra von der Decken 《The Journal of cell biology》1961,10(4):201-218
In the frog skeletal muscle cell a well defined and highly organized system of tubular elements is located in the sarcoplasm between the myofibrils. The sarcoplasmic component is called the sarcotubular system. By means of differential centrifugation it has been possible to isolate from the frog muscle homogenate a fraction composed of small vesicles, tubules, and particles. This fraction is without cytochrome oxidase activity, which is localized in the mitochondrial membranes. This indicates that the structural components of this fraction do not derive from the mitochondrial fragmentation, but probably from the sarcotubular system. This fraction, called sarcotubular fraction, has a Mg++-stimulated ATPase activity which differs from that of muscle mitochondria in that it is 3 to 4 times higher on the protein basis as compared with the mitochondrial ATPase, and is inhibited by Ca++ and by deoxycholate like the Kielley and Meyerhof ATPase. We therefore conclude that the "granules" of the Kielley and Meyerhof ATPase, which were shown to have a relaxing effect, are fragments of the sarcotubular system. The isolated sarcotubular fraction has a high RNA content and demonstrable activity in incorporating labeled amino acids, even in the absence of added supernatant. 相似文献
8.
Andrea Robitzki Alexandra Mack Arnaud Chatonnet Paul G. Layer 《Journal of neurochemistry》1997,69(2):823-833
Abstract: The function of the enzyme butyrylcholinesterase (BChE) in the developing and mature brain is still unclear. We have inserted 577 bp of the 5' upstream region plus 106 bp of the exon 1 of the rabbit BChE gene in reverse orientation under control of an SV40 early promoter derivative in an expression vector. This vector was introduced by calcium phosphate-mediated transfection into embryonic chicken retina cells during the first days of reaggregation culture. Depending on the retinal origin, the transfected cell population forms histotypic retina-like spheres, so-called rosetted or stratified retinospheroids. We show that antisense 5'-BChE gene expression decreased the steady-state mRNA level of BChE and the translation of the BChE protein, inhibited proliferation, and accelerated histogenesis in both cellular systems. The pronounced effects of antisense 5'-BChE transfection of spheroids document a key role of BChE during the early reaggregation process of retinal cells, most likely by regulating their growth and differentiation. 相似文献
9.
Evidence for a major gene (RP10) for autosomal dominant retinitis pigmentosa on chromosome 7q: linkage mapping in a second,unrelated family 总被引:7,自引:0,他引:7
Rachel E. McGuire Alexandra M. Gannon Lori S. Sullivan Joseph A. Rodriguez Stephen P. Daiger 《Human genetics》1995,95(1):71-74
Retinitis pigmentosa is a genetically heterogeneous form of retinal degeneration, which has X-linked, autosomal recessive and autosomal dominant forms. The disease genes in families with autosomal dominant retinitis pigmentosa (adRP) have been linked to six loci, on 3q, 6p, 7p, 7q, 8q and 19q. In a large American family with late-onset adRP, microsatellite markers were used to test for linkage to the loci on 3q, 6p, 7p, 7q and 8q. Linkage was found to 7q using the marker D7S480. Additional microsatellite markers from 7q were then tested. In total, five markers, D7S480, D7S514, D7S633, D7S650 and D7S677, show statistically significant evidence for link-age in this family, with a maximum two-point lod score of 5.3 at 0% recombination from D7S514. These results confirm an earlier report of linkage to an adRP locus (RP10) in an unrelated family of Spanish origin and indicate that RP10 may be a significant gene for inherited retinal degeneration. In addition, we used recently reported microsatellite markers from 7q to refine the linkage map of the RP10 locus. 相似文献
10.
Victor Rico-Gray Jose G. Garcia-Franco Alexandra Chemas Armando Puch Paulino Sima 《Economic botany》1990,44(4):470-487
We studied species composition, similarity, and structure of homegardens in two Yucatecan Maya communities, Tixpeual and Tixcacaltuyub, Yucatan, Mexico. The number of gardens sampled per village was 20 and 22; total area sampled was very similar, 45,265 m2 and 40,150 m2; the number of trees and shrubs present was 5651 and 5603; and number of species was 135 and 133, respectively. Diversity was low for both sites (H′= 1.6), as were the correlation coefficients (r) for the species-area and individuals-area correlations. The relatively low values obtained for the structural parameters reflect the random pattern of plant incorporation to the gardens, the variability in the proportion of constantly used and not constantly used garden area, and a certain uniformity in the number of species used and number of individuals present, and the relationship between these parameters and garden size. All these reflect the uniqueness of each homegarden, which depends upon the cultural background of the owner. We noticed a trend towards a change in homegarden structure and function in response to the modernization process. Homegardens in villages in the outskirts of cities tend to have more ornamental species and commercial fruit plants than homegardens in isolated villages. 相似文献