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991.
Lysophosphatidate Acyltransferase in the Microsomes from Maturing Seeds of Meadowfoam (Limnanthes alba) 总被引:6,自引:5,他引:1 下载免费PDF全文
Lysophosphatidate (LPA) acyltransferase (EC 2.3. 1.51) in the microsomes from the maturing seeds of meadowfoam (Limnanthes alba), nasturtium (Tropaeolum majus), palm (Syagrus cocoides), castor bean (Ricinus communis), soybean (Glycine max), maize (Zea mays), and rapeseed (Brassica napus) were tested for their specificities toward 1-oleoyl-LPA or 1-erucoyl-LPA, and oleoyl coenzyme A (CoA) or erucoyl CoA. All the enzymes could use either of the two acyl acceptors and oleoyl CoA, but only the meadowfoam enzyme could use erucoyl CoA as the acyl donor to produce dierucoyl phosphatidic acid (PA). The meadowfoam enzyme was studied further. It had an optimal activity at pH 7 to 8, and its activity was inhibited by 1 millimolar MnCl2, ZnCl2, or p-chloromercuribenzoate. In a test of substrate specificity using increasing concentrations of either 1-oleoyl-LPA or 1-erucoyl-LPA, and either oleoyl CoA or erucoyl CoA, the enzyme activity in producing PA was highest for dioleoyl-PA, followed successively by 1-oleoyl-2-erucoyl-PA, dierucoyl-PA, and 1-erucoyl-2-oleoyl-PA. In a test of substrate selectivity using a fixed combined concentration, but varying proportions, of 1-oleoyl-LPA and 1-erucoyl-LPA, and of oleoyl CoA and erucoyl CoA, the enzyme showed a pattern of acyl preference similar to that observed in the test of substrate specificity, but the preference toward oleoyl moiety in the substrates was slightly stronger. The meadowfoam microsomes could convert [14C]glycerol-3-phosphate to diacylglycerols and triacylglycerols in the presence of erucoyl CoA. The meadowfoam LPA acyltransferase is unique in its ability to produce dierucoyl-PA, and should be a prime candidate for use in the production of trierucin oils in rapeseed via genetic engineering. 相似文献
992.
Acetohydroxy Acid Synthase Activity in Chlorella emersonii under Auto- and Heterotrophic Growth Conditions 下载免费PDF全文
Acetohydroxyacid synthase (AHAS) activity was studied in the green unicellular alga Chlorella emersonii. This activity and its regulation was compared in the algae grown autotrophically and heterotrophically on glucose in the dark. No evidence for the existence of more than one enzyme was found. The activity in crude extracts from either heterotrophically or autotrophically grown cells showed a Km for pyruvate of 9 millimolar, a 22-fold preference for 2-ketobutyrate over pyruvate as the second substrate, 50% inhibition by 0.5 millimolar valine, and 50% inhibition by 0.3 micromolar sulfometuron methyl (SMM). Spontaneous mutants of the alga resistant to SMM were isolated, which appeared to be single gene mutants containing SMM-resistant AHAS activity. Hence, AHAS appears to be the sole direct target site of SMM in C. emersonii. The fact that the mutants had equivalent SMM resistance under auto- and heterotrophic conditions further supports the conclusion that the same enzyme functions under both physiological regimes. The addition of valine and isoleucine leads to partial relief of SMM inhibition of biomass increase, but not of SMM inhibition of cell division. 相似文献
993.
An effective method of reconstruction of the auricular conchal cavity using a postauricular island flap containing the postauricular blood vessels is described. In this procedure, the island flap is brought in to cover the defect of the conchal cavity through a tunnel between the defect and the retroauricle. Sound anatomic and mechanical principles are introduced in this technique. Two patients underwent the operation, and good results were obtained. 相似文献
994.
Summary The plant root tip represents a fascinating model system for studying changes in Golgi stack architecture associated with the developmental progression of meristematic cells to gravity sensing columella cells, and finally to young and old, polysaccharideslime secreting peripheral cells. To this end we have used high pressure freezing in conjunction with freeze-substitution techniques to follow developmental changes in the macromolecular organization of Golgi stacks in root tips ofArabidopsis andNicotiana. Due to the much improved structural preservation of all cells under investigation, our electron micrographs reveal both several novel structural features common to all Golgi stacks, as well as characteristic differences in morphology between Golgi stacks of different cell types.Common to all Golgi stacks are clear and discrete differences in staining patterns and width of cis, medial and trans cisternae. Cis cisternae have the widest lumina (30 nm) and are the least stained. Medial cisternae are narrower (20 nm) and filled with more darkly staining products. Most trans cisternae possess a completely collapsed lumen in their central domain, giving rise to a 4–6 nm wide dark line in cross-sectional views. Numerous vesicles associated with the cisternal margins carry a non-clathrin type of coat. A trans Golgi network with clathrin coated vesicles is associated with all Golgi stacks except those of old peripheral cells. It is easily distinguished from trans cisternae by its blebbing morphology and staining pattern. The zone of ribosome exclusion includes both the Golgi stack and the trans Golgi network.Intercisternal elements are located exclusively between trans cisternae of columella and peripheral cells, but not meristematic cells. In older peripheral cells only trans cisternae exhibit slime-related staining. Golgi stacks possessing intercisternal elements also contain parallel rows of freeze-fracture particles in their trans cisternal membranes. We propose that intercisternal elements serve as anchors of enzyme complexes involved in the synthesis of polysaccharide slime molecules to prevent the complexes from being dragged into the forming secretory vesicles by the very large slime molecules. In addition, we draw attention to the similarities in composition and apparent site of synthesis of xyloglucans and slime molecules.Dedicated to the memory of Professor Oswald Kiermayer 相似文献
995.
K Markiewicz L Górski M Cholewa Z Gawor T Dryjański 《Polski tygodnik lekarski (Warsaw, Poland : 1960)》1990,45(23-24):461-465
Nifedipine was administrated to 25 patients with chronic congestive heart failure treated with digoxin and furosemide++, nifedipine (NF) in a daily dose of 30-80 mg for 14 days. Before and after the treatment with nifedipine chest X-ray, blood biochemical investigations, echocardiographic evaluation of the left ventricular function and submaximal exercise test were performed. Nifedipine induced significant decreases in the left ventricular systolic dimension, heart volume, blood serum potassium and uric acid concentrations and hematocrit . Resting and exertional heart rate, blood pressure, exercise power and duration, watt-pulse, myocardial oxygen demand index, ejection fraction, cardiac output, body weight, 24-hour urinary output, blood serum concentrations of urea, creatinine, sodium and chloride changed insignificantly following nifedipine administration. The obtained results suggest that long-term nifedipine treatment of patients who were already given digoxin and furosemide neither improve nor worsen their clinical status. 相似文献
996.
A Grzegorzewska Z Lowicki E Chmara A Mrozikiewicz K Baczyk 《Polski tygodnik lekarski (Warsaw, Poland : 1960)》1990,45(16-18):339-341
This work aimed at establishing whether liver ability to biotransformation of drugs expressed by antipyrine kinetics is disturbed in peritoneally dialysed patients with end-stage renal failure. The investigations were carried out in 10 uraemic patients using the antipyrine test and comparing antipyrine kinetics with those obtained in 13 healthy individuals. At the time of investigations, standard clinical tests of liver function were normal and HBs antigen was absent in all patients. It was shown that peritoneally dialysed patients with end-stage renal failure had not significantly changed antipyrine elimination as compared with the group of healthy controls: t0.5 = 13.2 +/- 6.8 v. 11.8 +/- 8.1 h, plasma clearance = 50 +/- 30 v. 34 +/- 21 ml/min (x +/- SD). The obtained results indicate that antipyrine kinetics is within normal range in uraemic patients regularly dialysed suggesting cytochrome P-450 in microsomes not being markedly reduced. 相似文献
997.
E Rudzki D Litewska Z Samochocki P Rebandel E Saciuk A Chrupek B Niemczyk 《Polski tygodnik lekarski (Warsaw, Poland : 1960)》1990,45(42-44):876-879
Three hundred sixty five children and hundred thirty nine adults with atopic dermatitis were divided into three groups. Group A included patients with negative family history of allergy; group B--allergy history in one parent or his family; group C--allergy in both parents or their families. It was found that total IgE level was higher in patients of group C in comparison with group A. Similarly, bronchial asthma and/or rhinitis coexisted more frequently, incidence of urticaria was higher and its onset earlier in patients of group C. The results noted in patients of group B occupied middle position between those in group A and group C. Results related to the incidence of RAST positive reactions and multiple sensitivity were similar but the differences were lower. Radioimmunologic assays were performed only in part of the tested patients. 相似文献
998.
Summary In tip-growingChara rhizoids, the in-vivo saltatory movements of Golgi vesicles were recorded. The movements in radial direction back and forth between the ER aggregate and the plasma membrane occurred three times more often than movements passing the ER aggregate tangentially. The mean velocity of the class of Golgi vesicles observed (0.4–1 m in diameter) was approx. 0.3 m/s. Higher speed of 1–1.5 m/s occurred only in radial directions. Possibly, the ER aggregate is involved in guidance of the Golgi vesicles.Abbreviations DIC
differential interference contrast
- ER
endoplasmic reticulum
- OsFeCN
osmium tetroxide-potassium ferricyanide
Dedicated to the memory of Professor O. Kiermayer 相似文献
999.
M. Z. Oracion K. Niwa I. Shiotani 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1990,80(5):617-624
Summary Tetraploid F1 hybrids between Ipomoea batatas, sweet potato (2n = 6x = ca. 90), and diploid (2n = 2x = 30) I. trifida (H. B. K.) Don. showed various degrees of fertility reduction. The present study aimed to clarify its causes by cytological analysis of meiotic chromosome behavior in the diploid and sweet potato parents and their tetraploid hybrids. The diploid parents showed exclusively 15 bivalents, and the sweet potato parents exhibited almost perfect chromosome pairing along with predominant multivalent formation. Their hybrids (2n = 4x= 57–63) formed 2.6–5.0 quadrivalents per cell, supporting the autotetraploid nature. The meiotic aberratios of the hybrids were characterized by the formation of univalents, micronuclei, and abnormal sporads (monad, dyad, triad, and polyad). The causes underlying these aberrations were attributed in part to the multivalent formation, and in part to a disturbance in the spindle function. Three hybrids showing serious meiotic aberrations were very low in fertility. The utilization of the sweet potato-diploid I. trifida hybrids for sweet potato improvement is described and, further, the role of interploidy hybridization in the study of the sweet potato evolution is discussed. 相似文献
1000.
It has been found that nearly 50% of the lymph node and spleen macrophages (MP) of the CBA line mice contain DNA at levels superior to the diploid value (H2c--H4c in mononuclear MP, and up to H16c among polynuclear ones, the latter comprising 2.5-9.0% of the whole MP population). No DNA synthesis and mitosis were detected by autoradiography, cytophotometry, and cytomorphological analysis. During carcinogenesis the proportion of MP with elevated DNA amounts ("activated MPs") decreases due to their migration to tumours. Also immature MPs (1.6%) appear in the population, which synthesize DNA, but do not divide. Injection of retinoids restores the percentage of MPs with elevated DNA amounts to the levels characteristic of the intact animals, the fraction of DNA-synthetizing cells increasing up to 2.8%. It is proposed that retinoids may accelerate the processes of MP maturation, activation and renewing. A mechanism of cooperative action of MPs and retinoids is discussed in addition to the role of DNA hyper-replication. 相似文献