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131.
C. A. Cullis 《Biochemical genetics》1979,17(3-4):391-401
The segregation of isozymes of peroxidase and acid phosphatase in progenies of crosses between large (L) and small (S and L6) flax genotrophs has been determined. The peroxidase isozymes segregated as expected on a simple Mendelian model with a dominant and a recessive allele and with the L genotroph being a homozygous dominant. All the peroxidase isozymes which differed segregated together, so the isozymes are controlled by either a single locus or closely linked loci. The acid phosphatase isozymes in the F1 were all L type, but the segregations observed in the F2 were not always consistent with a simple Mendelian model. 相似文献
132.
The temperature and orientation dependence of pulsed NMR ‘free induction decay’ signals have been studied in detail for lipid bilayers macroscopically-oriented between glass slides. Results for the lipid molecules (1H, 31P), bound water (2H2O) and ions dissolved in the aqueous phase (23Na) are presented. Bilayers of egg-lecithin, dimyristoyl lecithin and potassium oleate have been investigated. In the liquid crystal phase all the signals, including those from bound water and ions exhibit a |3 cos2? ? 1| dependence on orientation of the bilayer normal to the magnetic field. In the case of DML samples, some orientation dependence of both 1H and 2H signals persists in the gel phase, indicating that the lipid molecules retain a degree of reorientational freedom about their long axes in this phase. At the gel-liquid crystal transition the 2H quadrupole spittings undergo a discontinuous change. Results are interpreted in terms of a model in which water molecules are bound to individual lipid head groups and reorient with them, while sodium ions are located in the aqueous channel between bilayers. 相似文献
133.
Pseudomonas testosteroni metabolized 4-hydroxycinnamate by an initial cleavage of the side chain to yield acetate and the aromatic moiety, 4-hydroxybenzaldehyde. The latter was further oxidized via 4-hydroxybenzoate to protocatechuate, which underwent meta cleavage. During growth of the organism on 4-hydroxycinnamate, the
for acetate showed an undulating pattern, which was attributed to alternating induction and repression of enzymes involved in the oxidation of acetate. Repression was caused either by 4-hydroxybenzoate or by its later metabolites, formate and pyruvate.In batch culture, P. testosteroni oxidized mixtures of 4-hydroxybenzoate and 4-hydroxycinnamate in a diauxic pattern. The capacity to oxidize 4-hydroxycinnamate appeared in the cells before 4-hydroxybenzoate was exhausted, indicating that the enzymes catalysing the conversion of 4-hydroxycinnamate into 4-hydroxybenzoate. were induced despite the presence of 4-hydroxybenzoate. The induction of these early enzymes of 4-hydroxycinnamate catabolism started when the molar concentration ratio of 4-hydroxybenzoate to 4-hydroxycinnamate fell below a value of 0.3.In continuous culture of P. testosteroni on a mixture of 4-hydroxybenzoate and 4-hydroxycinnamate, both substrates were almost completely utilized up to a dilution rate of about 0.5/h. At higher dilution rates, 4-hydroxycinnamate was decreasingly utilized so that eventually at a dilution rate of 0.74/h, its effluent concentration equalled its influent concentration. At D
M, a utilization ratio of 1.23 in favour of 4-hydroxybenzoate was found to become established in the culture. The
of the cells for acetate was maximal at a dilution rate of 0.38/h and decreased before 4-hydroxycinnamate utilization was at its peak at 0.59/h. This suggested that it was mainly the aromatic moiety of 4-hydroxycinnamate which was metabolized at high dilution rates. The failure to utilize acetate at high dilution rates was apparently due to the repression of its catabolic enzymes by later metabolites of 4-hydroxybenzoate and to the relatively low concentration of acetate in the fermenter. This low concentration, due to the continuous washout of acetate, prevented it from relieving the repression.Abbreviations 4HB
4-hydroxybenzoate
- 4HC
4-hydroxycinnamate
-
D
M
dilution rate allowing maximal cell output rate
- OD
optical density 相似文献
134.
Roberta C. Reuben 《Biochimica et Biophysica Acta (BBA)/General Subjects》1979,588(3):310-321
Hexamethylene bisacetamide (diacetyldiamino hexane) is a potent inducer of erythroid differentiation in murine erythroleukemia cells. Hexamethylene bisacetamide and the closely related pentamethylene bisacetamide were synthesized with radioactive labels in various portions of the molecule and the uptake, metabolism, and intracellular distribution determined. Bisacetamides are taken up by the cell; an intracellular concentration equal to the extracellular concentration is achieved by 6–8 h. Commitment to differentiation is not detected until at least 10 h after equilibration. Both uptake and commitment to differentiate are concentration and temperature dependent. The majority of the compound is deacetylated upon cell entry and the acetate portion incorporated nonspecifically into lipid and protein. Acetate competes with the incorporation of hexamethylene bisacetamide into protein and lipid, but does not affect inducing activity. The diamine portion of the molecule is detected only in the cytoplasm, in a trichloroacetic acid-soluble and acetylated form, whereas the acetate moiety is detected in both cytoplasm and nucleus and in both a trichloroacetic acid-soluble and insoluble form. The cellular uptake of diamines and bisacetamides (acetylated diamines) are similar, but acetylation of the diamine greatly increases inducing activity. 相似文献
135.
The effect of exposure period and concentration of algae on the frequency of infection of aposymbiotic ciliates by algae obtained from the same clone of Paramecium bursaria syngen 2, was studied. The frequency of infection was roughly proportional to the algal concentration and to the exposure time of ciliates to algae. The relationship of algal concentration to infection frequency closely fitted the Poisson distribution curve for N = 1, suggesting that the minimum number of algae required to infect a single ciliate is 1. However, the data also strongly suggested that the average number of algae required to initiate infection of an average ciliate was ? 1,000. Three possible resolutions of this situation are: (a) the selection by the ciliate of a rare infective variant from a heterogeneous population: (b) the rare escape of an alga from digestion by the ciliate; and (c) the requirement for a large number of algae-ciliate contacts to induce susceptibility in the ciliate. Splitting the exposure of ciliates to algae into 2 periods of 0.5 h, separated by 5 h in the absence of algae, produced a much higher frequency of infection than a single l-h exposure, supporting the suggestion that the large number of algae is required to induce susceptibility in the ciliate which can then be infected by as few as a single algal cell. 相似文献
136.
Growth and nitrate reductase activity were measured in Paul's Scarlet rose cell suspensions, cultured in media purified from molybdenum and containing nitrate or urea as sole nitrogen source with or without added Mo. Urea could replace nitrate to yield 80% of the fresh weight in nitrate medium. Nitrate reductase activities were compared by in vivo and in vitro assays. The latter varied due to inactivation during extraction. Compared with activities in cells in complete NO3
- medium, activity in NO3
--Mo cells was reduced to 30% and, in urea-grown cells, to trace amounts. Increases in nitrate reductase activity were found when NO3
- alone was added to NO3
- or urea+Mo cultures. In NO3
--Mo cultures, Mo alone or with NO3
- caused a similar increase in activity, whereas urea-Mo cultures required both NO3
- and Mo for enzyme induction.Abbreviations FAD
flavin adenine dinucleotide
- Mo
molybdenum
- NADH
reduced nicotinamide adenine dinucleotide
- NO3
-+Mo
standard MX1 culture medium
- NO3
--Mo
MX1 medium purified of Mo and used for continuous subculture with nitrate
- NR
nitrate reductase
- PSR
Paul's Scarlet rose
- PVP
polyvinylpyrrolidone
- U
urea
- U+Mo
MX1 medium containing urea instead of nitrate
- U-Mo
MX1 medium containing urea instead of nitrate and also purified of Mo 相似文献
137.
DONALD L. CRONKITE 《The Journal of eukaryotic microbiology》1976,23(3):431-433
SYNOPSIS. Conjugation in Paramecium tetraurelia can be induced within mating-reactive cultures of a single mating type by treating the cells with solutions of KC1 + acriflavine in culture medium low in Ca2+. Gene mutations with known physiologic effect were used as selective inhibitors of cell surface membrane function to see which functions are necessary for chemical induction of conjugation. The results strongly suggest that a transient increase in the internal concentration of calcium at the very beginning of chemical induction is a necessary but not sufficient step. 相似文献
138.
139.
家蝇幼虫血淋巴中抗真菌肽的诱导方法比较及抗真菌活性 总被引:1,自引:0,他引:1
以未诱导组作为空白对照研究比较真菌诱导、超声诱导和热诱导家蝇Musca domestica 幼虫血淋巴初提液的抗真菌肽效果,比较各种诱导方法诱导后的幼虫存活率;用凝胶层析法和高效液相分离纯化热诱导家蝇3龄幼虫抗真菌肽,检测其抗白假丝酵母菌Candida albicans和新生隐球菌Cryptococcus neoformans活性;SDS-PAGE分析抗真菌肽的蛋白分子量范围。结果表明:3种诱导方法诱导后家蝇幼虫均产生具有明显抗真菌作用的抗真菌肽,其初提液抑菌圈大小没有明显差别;真菌诱导组和热诱导组幼虫存活率低于对照组,而超声诱导组与对照组相比则无明显差别。经分离纯化后,抗真菌肽仍具有较好的抗真菌活性;SDS-PAGE分析表明该抗真菌肽有效成分的蛋白分子量在14.4 kD以下。结果提示热诱导家蝇幼虫产生抗真菌肽是一种方便、有效的诱导方式。 相似文献
140.
NaCl胁迫对PSII光能利用和耗散的影响 总被引:13,自引:1,他引:13
用荧光动力学的方法研究了不同浓度的NaCl 处理对PSII光能利用和耗散的影响。结果表明,在较低的光强下,与对照、100m mol/L 和200m mol/L NaCl 处理相比,经300m mol/L 和400m mol/L NaCl 处理的小麦,其荧光光化学淬灭效率较低,荧光非光化学淬灭效率较高,Fo 淬灭系数较大,QB - 非还原性PSII反应中心含量较大; 而在较高光强下, 其荧光非光化学淬灭效率和Fo 淬灭系数则相对较低。 相似文献