共查询到20条相似文献,搜索用时 31 毫秒
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Lipophilic cationic fluorescent dyes (D) specifically stain the mitochondria of living cells. A perfusion chamber for cell cultures is described, which can be used to determine the kinetics of vital staining of the mitochondria of single selected cells in situ. In these experiments styrylpyridinium dyes and cultures of HeLa cells were used. The dyes differ strongly in their lipophilic properties; R
m values and the partition coefficients P
o/w between n-octanol (o) and water (w) were determined in order to characterize their lipophilicity. In the thermostat-regulated chamber the concentration of the dye C
D can be increased from C
D=0 to C
D>0 within a few seconds (concentration jump). Thus, the time t=0 for the beginning of the vital staining and the dye concentration in the cell medium during the staining experiment, C
D=const., are unambiguously defined. The concentration of the dye, C
b, which is bound to the mitochondria (b), is proportional to the intensity of the fluorescence I
b. On the other hand, the free dye molecules (f) in the aqueous medium exhibit practically no fluorescence, I
fI
b. The intensity of the fluorescence I=I
b was measured as a function of time t; the measured values were corrected for photobleaching. The fluorescence intensity I(t) at first increases linearly with t and reaches a saturation value for t . In the linear range of I(t) the flow J
o=(dI/dt)o of the dye into the cell depends strongly on the dye concentration and increases linearly with C
D. The concentration range C
D=10–9–10–5
M at 37° C was investigated. From the linear correlation between J
o and C
D it follows that the kinetics of the vital staining of mitochondria is controlled by diffusion. At t=0 the flow of the xenobiotic agent through the cell membrane determines the rate of staining. The slope dJ
o/dC
D of the plot J
o vs C
D describes the efficiency of dye accumulation at the mitochondria and strongly increases with increasing lipophilicity of the dye molecules. Thus lipophilic dyes pass through the cell membrane more easily than less lipophilic molecules. 相似文献
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W.B. Allington A.L. Cordry G.A. McCullough D.E. Mitchell J.W. Nelson 《Analytical biochemistry》1978,85(1):188-196
An apparatus for concentrating macromolecules and removing macro molecules from nonionic solutes electrophoretically has been developed. Typical applications and techniques are outlined. Concentrations from 24- to 50-fold were achieved in a short period of time. The nondisruptive nature and versatility of the system is shown by the concentration of bovine serum albumin and three different enzymes. 相似文献
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Summary The inhibition effects onZymomonas mobilis of ethanol concentration history (time-integrated exposure to ethanol) and ethanol concentration change rate have been investigated. It was found that the ethanol concentration history had no significant effect on the fermentative capability ofZ. mobilis, while the ethanol concentration change rate had a quite intense inhibitory effect. 相似文献
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Johnson TD 《Biometrics》2007,63(4):1207-1217
Many challenges arise in the analysis of pulsatile, or episodic, hormone concentration time series data. Among these challenges is the determination of the number and location of pulsatile events and the discrimination of events from noise. Analyses of these data are typically performed in two stages. In the first stage, the number and approximate location of the pulses are determined. In the second stage, a model (typically a deconvolution model) is fit to the data conditional on the number of pulses. Any error made in the first stage is carried over to the second stage. Furthermore, current methods, except two, assume that the underlying basal concentration is constant. We present a fully Bayesian deconvolution model that simultaneously estimates the number of secretion episodes, as well as their locations, and a nonconstant basal concentration. This model obviates the need to determine the number of events a priori. Furthermore, we estimate probabilities for all "candidate" event locations. We demonstrate our method on a real data set. 相似文献
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A specific continuous-flow analytical system for determination of lactose concentration in a liquid mixture of constituent sugars was developed and tested based on a series of enzymatic reactions. Lactose and glucose oxidase immobilized on a phenol–formaldehyde resin were employed. More detailed study was carried out based on a reaction by-product quantitatively detected by an available iodide electrode. A multichannel proportioning pump fed two independently operated analytical streams eliminating thus the background glucose interference. With a goal of lactose concentration control in a fermentation process, the system response time delay was shortened to approximately 15 min. Apart from optimization of the analytical system operating parameters, the study indicates also the major application problem areas: lactase inhibition by galactose, galactose oxidation by glucose oxidase, and a partial loss of glucose oxidase activity in a prolonged continuous-flow operation. A manual Colorimetric Procedure was employed to verify the results of the potentiometric method. 相似文献
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The apparent viscosity of baker's yeast suspensions was employed to control the cell concentration of the mixing of baker's yeast and distilled water. The apparent viscosity of baker's yeast was found to be a function of cell concentration and independent of the flow rate through the rotational viscometer. The viscometer and mixing unit were found to have first order dynamics. The open loop dynamics of the control system were nonlinear but could be linearized for small perturbations. The control system was employed to successfully control the cell concentration but exhibited nonlinear behavior. 相似文献
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N A Margolina T I Rozhanskaya B V Moskvichyov G V Samsonov G Z Nefyodova S A Tverskaya 《Prikladnaia biokhimiia i mikrobiologiia》1975,11(4):601-603
Criteria for the selection of membranes and optimal conditions for the trypsin concentration by ultrafiltration through acetylcellulose membranes have been developed. The possibility of a repeated concentration of trypsin by means of these membrances has been shown. 相似文献
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Ascorbate concentration in fish ontogeny 总被引:2,自引:0,他引:2
K. Dabrowski 《Journal of fish biology》1992,40(2):273-279
The ontogenetic trend of ascorbate has been quantified in three freshwater fishes: roach ( Rutilus rutilus ), whitefish ( Coregonus lavaretus ) and Arctic charr ( Salvelinus alpinus ). Total ascorbate (reduced and oxidized) declined from 150 to μg g−1 as newly hatched larvae grew to become several-months-old juveniles. Declining total ascorbate with increasing size of metamorphosing fish could not be reversed by feeding on brine shrimp, Artemia salina nauplii, zooplanktonic food containing > 74μg g−1 total ascorbate. The proportion of reduced ascorbate in total ascorbate increases with fish size/age. The physiological mechanism of the changes in transferable ascorbate forms remains unknown, but high dehydroascorbate concentrations suggest high vulnerability of larval fish to oxidation stress. This is the first report on quantity of vitamin C retained in actively-feeding larval and juvenile fish. The efficiency of ascorbate transfer from zooplankters to larval fish amounted to 5–20%. The ecological significance of larval fish feeding on various zooplankters and/or phytoplankton may reflect a trend toward maximum transfer of this vitamin in freshwater food webs. 相似文献
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A simple technique is described for easy removal of high concentration polyacrylamide gels after electrophoresis from glass tubes without breaking them. 相似文献
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Summary Clarification of fermentation broths by TFMF has been studied using new and “old” membranes. Efficient recovery of SK in the
filtrate by simple TFMF process was not possible, 41.9% of the activity remains in the retentate. In situ washes do not solve
the problem. Total recovery implies centrifugation of the retentate. 相似文献
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Samples of healthy tissue were taken from each of six prostatectomy specimens (55–72 yr), digested with acids, and analyzed
for selenium by atomic fluorescence spectroscopy. The concentrations for five specimens were 1.32±0.09 μg Se/g dry wt (range
1.24–1.42) and 0.213±0.012 μg Se/g wet wt (range 0.200–0.229). The other specimen, from a 58-yr-old man who was the only one
within this study to take a 200-μg Se/d dietary supplement, contained 2.72 μg Se/g dry wt and 0.421 μg Se/g wet wt. 相似文献
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W Wasowicz 《Acta physiologica Polonica》1989,40(5-6):558-563
In this work we have determined selenium concentration in urine in two groups of healthy subjects. Selenium content in the younger group, aged 11-15 years (n = 41), was 13.7 +/- 6.5 micrograms/g-1 creatinine. In the older group, aged 17-97 years (n = 62), slightly but statistically significant lower selenium concentration in urine (11.4 +/- 4.9 micrograms/g Ct, p less than 0.05) was found. We have also shown a significant difference in the excretion of the element between the group of boys and men (p less than 0.05). Concentration of selenium excreted in urine in the population of healthy people (11-97 years, n = 103) is 12.3 +/- 5.4 micrograms Se/g Ct. 相似文献
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M A El-Rifai 《Journal of theoretical biology》1984,106(4):559-576
Three different active transport membrane configurations are suggested for achieving concentration amplification in a circulating substrate solution. The steady-state characteristics of the structures are investigated on the basis of a linear approximation of the rate of active transport. An analysis of the effects of system parameters and geometry on the concentration gradient along the flow path is presented. It is seen that the concentration gradient may be synthesized by appropriate choice of membrane arrangement, flow and physico-chemical transport parameters. 相似文献