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81.
Gene expression during tuber development in potato plants 总被引:4,自引:0,他引:4
S Prat W B Frommer R H?fgen M Keil J Kossmann M K?ster-T?pfer X J Liu B Müller H Pe?a-Cortés M Rocha-Sosa 《FEBS letters》1990,268(2):334-338
Potato tubers are modified stems that have differentiated into storage organs. Factors such as day-length, nitrogen supply, and levels of the phytohormones cytokinin and gibberellic acid, are known to control tuberization. Morphological changes during tuber initiation are accompanied by the accumulation of a characteristic set of proteins, thought to be involved in N-storage (i.e. patatin) or defense against microbial or insect attack (i.e. proteinase inhibitor II). Additionally, deposition of large amounts of starch occurs during tuber formation, which is paralleled by an increase in sucrose synthase and other enzymes involved in starch biosynthesis (i.e. ADP-glucose pyrophosphorylase, starch synthases, and branching enzyme). Potential controlling mechanisms for genes expressed during tuberization are discussed. 相似文献
82.
Increased susceptibility of ribulose-1,5-bisphosphate carboxylase/oxygenase to proteolytic degradation caused by oxidative treatments 总被引:5,自引:0,他引:5
The susceptibility of the chloroplastic enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase to proteolysis by trypsin, chymotrypsin, proteinase K, and papain is enhanced by oxidative treatments including spontaneous oxidation of cysteines. Proteinases exhibit a high specificity for the oxidized inactive form of the carboxylase, cleaving its large subunit. Treatment of the inactive enzyme with dithiothreitol results in partial recovery of both carboxylase activity and resistance to proteolysis. This behavior may explain the specific degradation of ribulose-1,5-bisphosphate carboxylase/oxygenase that occurs in vivo during leaf senescence. 相似文献
83.
M Pombo F Alvez R Varela-Cives J L Iglesias-Diz F Martinón M Castro-Gago J Pe?a 《Hormone research》1982,16(3):160-163
The authors present the 2nd documented case of Wilms' tumor associated with the "ectopic ACTH syndrome'. This is a 7 1/2-year-old girl who, on examination at the time of admission, had the classical cushingoid appearance. A large hard mass was palpable in the right side of the abdomen. Hormonal assays were consistent with Cushing's syndrome; the serum ACTH levels were extremely high. After surgical removal of the mass, we suspected a stage I Wilms' tumor; this was confirmed by histopathological studies. After surgery, the girl quickly lost her cushingoid appearance and weight excess. Postoperative serum ACTH levels were normal. Ectopic hormone syndromes associated with tumors in childhood are discussed as well as the possible mechanism involved in the ectopic production of ACTH. 相似文献
84.
85.
The effective synthesis of 4,4,14α-trimethyl-19 (10 → 9β) abeo-steroids (iv), (v), and (Vl) with two- and five-carbon side chains from lanosterol is described. Their structures were proved on the basis of spectral data. The title compounds are the first synthetic synthons for the preparation of 4,4,14α-trimethyl-steroids with an unnatural configuration. 相似文献
86.
A simple filter method for the fluorometric estimation of DNA in alkaline and neutral sucrose gradient fractions with DABA·2HCl is discussed. Alpha-450 membrane filters of regenerated cellulose (Gelman Instrument Co., Ann Arbor, Michigan) were used. In the proposed method washing of the DNA precipitate as well as the reaction with DABA·2HCl were performed directly on the filters, thus avoiding repeated washing and centrifugations of DNA precipitates applied hitherto in analogous fluorometric techniques. A good coincidence of the results concerning localization of DNA sedimentation profiles determined by radioisotopic and fluorometric methods was obtained. The method is very convenient for DNA estimation in alkaline and neutral sucrose density gradient fractions obtained by ultracentrifugation of DNA of nonproliferating cells where DNA labeling is very difficult, and in the case of human lymphocytes even impossible without stimulation for blastic transformation. Its other advantages are a considerably simplified procedure and a higher precision with respect to other fluorometric methods for determination of DNA. 相似文献
87.
Summary Experiments were performed to obtain information on: (i) the specific properties of Ca2+ binding and transport in yeast (ii) the relationship between both parameters; (iii) similarities to or differences from other biological systems as measured by the effects of inhibitors; and (iv) the effects of mono and divalent cations, in order to get some insight on the specificity and some characteristics of the mechanism of the transport system for divalent cations in yeast.The results obtained gave some kinetic parameters for a high affinity system involved in the transport of Ca2+ in yeast. These were obtained mainly by considering actual concentrations of Ca2+ in the medium after substracting the amounts bound to the cell. Ak
m
of 1.9 m and aV
max
of 1.2 nmol (100 mg·3 min)–1 were calculated.The effects of some inhibitors and other cations on Ca2+ uptake allow one to postulate some independence between binding and transport for this divalent cation.Of the inhibitors tested, only lanthanum seems to be a potent inhibitor of Ca2+ uptake in yeast.The effects of Mg2+ on the uptake of Ca2+ agree with the existence of a single transport system for both divalent cations.The actions of Na+ and K+ on the transport of Ca2+ offer interesting possibilities to study further some of the mechanistic properties of this transport system for divalent cations. 相似文献
88.
Summary Normal mouse spleen cells take up in vitro radioactively labeled immune RNA. RNA taken up is present in nuclei, polysomes, membranes and cytoplasm. About 20–40% of immune RNA is nonspecifically associated with cell surface. 45% of RNA taken up is degraded and reutilized inside the cells within 2 hours.This work was supported by the Polish Academy of Sciences within the project 09.7.4.1.1. 相似文献
89.
F De Venanzi F Pe?a O Jiménez H De Alvarado 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1976,152(1):47-51
Isolated perfused fed rat livers spontaneously liberated glucose and orthophosphate to the medium; 24-hr fasted rat livers did not exhibit these phenomena. In perfused fed rat livers, glucagon (2 mug) increased glucose output and promoted orthophosphate incorporation. In perfused fed rat livers, insulin (250 or 500 mU) inhibited the spontaneous liberation of glucose and orthophosphate. Comparable doses of insulin significantly reduced the glucagon (2 mug)-induced increase in glucose output from perfused fed rat liver, but did not affect orthophosphate uptake by the organ. 相似文献
90.
Examination was made of the effect of alternating light and darkness (LD 12:12) and constant light (LL) conditions on length of development and fecundity of the moth, Ephestia kuehniella. It was found the conditions applied cause acceleration of larval development on an average by 3 days in comparison with development under constant darkness conditions (DD). The fecundity of the insects examined decreases considerably under the experimental conditions.When pharate adults are kept in light for 18 hr per 24-hr period on the 6th to 7th day of their development, males incapable of fertilizing females are produced. 相似文献