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41.
Stomatal Movement and Sucrose Uptake by Guard Cell Protoplasts of Commelina benghalensis L. 总被引:2,自引:0,他引:2
Sucrose concentration in guard cells of epidermal strips ofCommelina benghalensis increased with stomatal opening. Sucroseuptake patterns were investigated using guard cell protoplastsof C. benghalensis. Sucrose (0.5 mM) uptake into these protoplastswas sensitive to pH, with an optimum at pH 6. Uptake of sucroseinto guard cell protoplasts was inhibited by 2,4-dinitrophenol(DNP), diethylstilbestrol (DES) and (ptrifluoromethoxy)carbonylcyanide phenylhydrozone (FCCP), while DCMU and o-phenanthrolinehad no effect on the uptake of sucrose. Fusicoccin (FC) stimulatedsucrose influx. The influence of pH and the effect of the metabolicinhibitors on the sucrose uptake into the guard cell protoplastsare consistent with an energy dependent membrane-function. (Received July 7, 1986; Accepted September 26, 1986) 相似文献
42.
A 81-fold purification of human seminal plasma acid phosphatase was obtained by a three-step procedure, involving ammonium sulfate precipitation, DEAE-cellulose chromatography and Sephadex G-200 gel filtration. Homogeneity of the preparation during purification steps was tested by polyacrylamide gel electrophoresis and only one major band was obtained after the final step. The pH optimum for the activity of the purified enzyme was 5.6 and thermal stability was obtained even up to 40 degrees C. PNPP was the most specific synthetic substrate. The Km of purified seminal acid phosphatase towards PNPP was 1.5 X 10(-3) M. Among the metal ions tested, Hg+2 showed an I50 value of 4.2 X 10(-7) M. Studies with PCMB, PMSF and EDTA did not show any inhibition, whereas NaF and L(+)tartrate, at 1 mM concentration, inhibited the enzyme by 95% and 85%, respectively. 相似文献
43.
Amino acid replacements in yeast iso-1-cytochrome c. Comparison with the phylogenetic series and the tertiary structure of related cytochromes c 总被引:14,自引:0,他引:14
The structural and folding requirements of eukaryotic cytochromes c have been investigated by determining the appropriate DNA sequences of a collection of 46 independent cyc 1 missense mutations obtained in the yeast Saccharomyces cerevisiae and by deducing the corresponding amino acid replacements that abolish function of iso-1-cytochrome c. A total of 33 different replacements at 19 amino acid positions were uncovered in this and previous studies. Because all of these nonfunctional iso-1-cytochromes c are produced at far below the normal level and because a representative number are labile in vitro, most of the replacements appear to be affecting stability of the protein or heme attachment. By considering the tertiary structure of related cytochromes c, the loss of function of most of the mutant iso-1-cytochromes c could be attributed to either replacements of critical residues that directly interact with the heme group or to replacements that disrupt the proper folding of the protein. The replacements of residues interacting with the heme group include those required for covalent attachment (Cys-19 and Cys-22), ligand formation (His-23 and Met-85), and formation of the immediate heme environment (Leu-37, Tyr-53, Trp-64, and Leu-73). Proper folding of the protein is prevented by replacements of glycine residues at sites that cannot accommodate side chains (Gly-11 and Gly-34); by replacements of residues with proline, which limit the torsion angle (Leu-14 and His-38); and by replacements apparently unable to direct the local folding of the backbone into the proper conformation (Pro-35, Tyr-72, Asn-75, Pro-76, Lys-84, Leu-99, and Leu-103). Even though most of the missense mutations occurred at sites corresponding to evolutionarily invariant or conserved residues, a consideration of the replacements in functional revertants indicates that the requirement for residues evolutionarily preserved is less stringent than commonly assumed. 相似文献
44.
Steinberg H.; Das D. K.; Cerreta J. M.; Cantor J. D. 《Journal of applied physiology》1986,61(2):775-779
Hyperoxic injury results in an influx of polymorphonuclear leukocytes (PMN) into the lung. To better understand the role of the PMN in this injury, kinetic studies were used to assess the survival of PMNs in the circulation. The rate of deposition of PMNs in the lungs of rabbits exposed to hyperoxia was also examined. The half-lives (T1/2) of [3H]thymidine-labeled PMNs in the circulation in rabbits exposed to air or to 95% O2 for less than or equal to 48 h varied between 3.9 and 4.5 h. After 72 h of hyperoxic exposure, T1/2 fell to 2.2 h, the marginal and circulating PMN pool increased and 3H deposition in the lung increased 10-fold. Autoradiographs confirmed that [3H]thymidine was initially nuclear- and cellular-associated but, with time, [3H]thymidine dispersed throughout the lung, suggesting PMN disintegration. These PMN events seem to occur in the later phases of O2 toxicity, and because PMNs are an additional source of oxyradicals, they may further amplify oxidant injury. 相似文献
45.
46.
Incidence of actinomycetes infection in women using intrauterine contraceptive devices 总被引:1,自引:0,他引:1
Pancervicovaginal smears taken from 350 women using an intrauterine contraceptive device (IUD) were screened for the presence of actinomycetes organisms. Of the 12 cases in which actinomycetes-like organisms were seen in Papanicolaou-stained smears, the presence of actinomycetes organisms was confirmed by immunofluorescence in 10 cases. The prevalence of actinomycetes infection was thus 2.8% (10 of 350 cases) in the IUD users. Eight (4.3%) of 173 symptomatic subjects had actinomycetes infections. Two of the positive cases were asymptomatic. Eight of the ten patients with confirmed actinomycetes infection were using the Cu T device while two were wearing the Lippes Loop IUD. Seven of the ten patients had been using an IUD for more than two years. The time of insertion of the IUD (postpuerperal, postmenstrual or after medical termination of pregnancy) did not show any correlation with the presence of actinomycetes infection. Actinomyces israelii was responsible for the infection in eight cases while Arachnia propionica was seen in two cases. The organisms could not be grown in culture. 相似文献
47.
Baseline frequency of sister-chromatid exchanges (SCE) in newborn lymphocytes and its relationship to in vivo aging in humans 总被引:1,自引:0,他引:1
Heparinised cord blood from newborns and peripheral venous blood from three other age groups of individuals (1-75 years) have been cultured in vitro to obtain baseline frequencies of SCE and to see if the frequency of baseline SCE in vitro varies as a function of aging in vivo. The results demonstrate an age-dependent variation in the frequency of SCEs. Although the SCE frequency was lowest (5.10/cell) in 1-5-year-old infants, a significantly higher (P less than 0.001) frequency (8.97/cell) was observed in the cord blood of newborns. In old age, the level of SCE also increased. The plausible reason(s) for such observations is discussed. 相似文献
48.
49.
The rate and extent of lysis of Vibrio cholerae cells under nongrowing conditions were dependent on the osmolarity of the growth medium. Gross alterations in cellular morphology were observed when V. cholerae cells were grown in media of high and low osmolarity. The rate of lysis of V. cholerae cells under nongrowing conditions increased after treatment with chloramphenicol. Chloramphenicol-treated V. cholerae 569B cells showed formation of sphaeroplast-like bodies in medium of high osmolarity, but not in low osmolarity. Changes in the osmolarity of the growth medium also regulated the expression of the outer membrane proteins. This regulation was abolished if V. cholerae cells were grown in Pi-depleted medium. Analysis of the lytic behavior and composition of outer membrane proteins of an osmotically fragile mutant strain revealed a similar dependence on the osmolarity of the growth medium. 相似文献
50.
Long term oscillation in glycolysis 总被引:3,自引:0,他引:3
To increase the period of glycolytic oscillations in yeast extracts (Saccharomyces uvarum), the dependence of the period on pH, on concentrations of phosphate and enzymes, and on temperature has been studied. Stable oscillatory trans were obtained at a pH value of about 6.5. Increasing the phosphate and decreasing the enzyme concentrations as well as decreasing temperature lengthened the period. By dilution of the extract with buffer while maintaining the metabolite concentrations at their initial level the period could be successively prolonged from 20 min to about 6 h. 相似文献