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11.
The effects of mineral salts constituting water hardness on fecundity ofDaphnia magna were assessed. Of the salts tested, increased concentrations of NaHCO3 and MgSO4 had no effect on fecundity, CaSO4 significantly increased fecundity, and KCl significantly reduced fecundity. The number of offspring produced per daphnid
was correlative to the CaSO4 concentration at CaSO4 concentrations between 91 and 2100 mg/ℓ. The effects of CaSO4 on daphnid fecundity could influence the interpretive outcome of industrial wastewater toxicity tests using this species
when the waste and dilution waters contain different concentrations of CaSO4. It is recommended that when performing these tests, dilution water be sampled at the intake site of the industry's water
source, thus assuring initial comparability of the waste and dilution waters. The CaSO4 content of the water prior to and after industrial use should be determined to identify any alterations of CaSO4 concentration during use. Identification of CaSO4 concentration differences can aid in the interpretation of effects associated with the wastewater. 相似文献
12.
Modifications of the kinetic properties of the Escherichia coli (RA11) Na(+) - H(+) antiport system by imposed pH gradients (deltapH, interior alkaline) and membrane potential(delta(psi), interior negative) were studied by looking at the accelerating effects of deltapH and delta on downhill Na(+) efflux from membrane vesicles incubated at different external pHs. First,variations of the Na(+) efflux rate ( VNa) as a function of imposed delta pH appear to be strongly dependent on the external pH value.The individual VN, vs. deltapH relationships observed between pH 5.5 and pH 6.6 are all nonlinear and indicate the existence of a threshold deltapH above which V(Na) increases steeply as the deltapH magnitude increases; threshold deltapH values progressively decrease as the pH is raised from 5.5 to 6.6. In contrast, at or above neutrality, V(Na) acceleration is linearly related to deltapH amplitude. Strikingly, it is shown that the deltapH-dependent variations in the Na(+) efflux rate measured in vesicles incubated at different external pHs can be accounted for by variations of internal pH; the observed relationship suggests that a high internal H(+) concentration inhibits the Na(+) -H(+) antiport activity.This inhibition results from a drastic increase in the apparent K(m), of the Na(+) efflux reaction as the internal H(+) concentration increases. On the other hand, imposed Δ increases the Na(+) efflux rate linearly by a selective modification of the V(max) value of the Na(+) efflux. Together, these data indicate that the internal H(+) concentration controls the Na(+)-H(+) antiport activity and that the chemical and electrical proton gradients affect two different kinetic steps of the Na(+)-H(+) exchange reaction. 相似文献
13.
Leukotriene B3, leukotriene B4 and leukotriene B5; binding to leukotriene B4 receptors on rat and human leukocyte membranes 总被引:1,自引:0,他引:1
S Charleson J F Evans R J Zamboni Y Leblanc B J Fitzsimmons C Leveillé P Dupuis A W Ford-Hutchinson 《Prostaglandins》1986,32(4):503-516
Specific high-affinity binding sites for [3H]-leukotriene B4 have been identified on membrane preparations from rat and human leukocytes. The rat and human leukocyte membrane preparations show linearity of binding with increasing protein concentration, saturable binding and rapid dissociation of binding by excess unlabelled leukotriene B4. Dissociation constants of 0.5 to 2.5 nM and maximum binding of 5000 fmoles/mg protein were obtained for [3H] leukotriene B4 binding to these preparations. Displacement of [3H]-leukotriene B4 by leukotriene B4 was compared with displacement by leukotriene B3 and leukotriene B5 which differ from leukotriene B4 only by the absence of a double bond at carbon 14 or the presence of an additional double bond at carbon 17, respectively. Leukotriene B3 was shown to be equipotent to leukotriene B4 in ability to displace [3H]-leukotriene B4 from both rat and human leukocyte membranes while leukotriene B5 was 20-50 fold less potent. The relative potencies for the displacement of [3H]-leukotriene B4 by leukotrienes B3, B4 and B5 on rat and human leukocyte membranes were shown to correlate well with their potencies for the induction of the aggregation of rat leukocytes and the chemokinesis of human leukocytes. 相似文献
14.
Photoacoustic spectroscopy of Anacystis nidulans. I. Effect of sample thickness on the photoacoustic signal 总被引:1,自引:0,他引:1
A photoacoustic spectroscopy study of the cyanobacteria Anacystis nidulans has been undertaken. It is demonstrated, by using a filter deposition technique, that the photoacoustic signal intensity becomes progressively saturated as the thickness of the algal layer is increased. This saturation effect originates mostly from the limited optical penetration of the sample and distorts the photoacoustic spectrum from its true shape. A theoretical model is proposed to explain these results, and practical means to obviate the limitations of this spectroscopic technique are suggested. 相似文献
15.
The photoacoustic spectrum of Anacystis nidulans recorded at room temperature is qualitatively similar to low-temperature absorption or fluorescence excitation spectra. The bands of pigment holochroms are well resolved compared to room-temperature absorption spectra. The thermal deactivation spectrum obtained by extrapolating acoustic data for an infinitely thin sample indicates that the photosynthetic efficiency decreases from phycocyanin to chlorophyll a and carotenoids. 相似文献
16.
17.
The photosynthetic energy storage yield of uncoupled thylakoid membranes was monitored by photoacoustic spectroscopy at various measuring beam intensities. The energy storage rate as evaluated by the half-saturation measuring beam intensity (i50) was inhibited by 3-(3,4-dichlorophenyl)-1,1 dimethylurea, by heat inactivation or by artificial electron acceptors specific for photosystem I or photosystem II; and was activated by electron donors to photosystem I. The reactions involving both photosystems were all characterized by a similar maximal energy storage yield of 16±2 percent. The data could be interpreted if we assumed that the energy storage elicited by the photosystems at 35 Hz is detected at the level of the plastoquinone pool.Abbreviations PS
photosystem
- Tes
N-Tris [hydroxymethl] methyl-2-aminoethanesulfonic acid
- DCMU
3-(3,4-dichlorophenyl)-1,1-dimethylurea
- DCIP
2,6-dichlorophenolindophenol
- FeCN
potassium ferricyanide
- DCBQ
2,5-dichlorobenzoquinone
- TMPD
N,N,N-tetramethyl-p-phenilenediamine 相似文献
18.
Gabrielle G. Leblanc 《Developmental neurobiology》1990,21(4):567-577
This study shows that explants of quail neural crest cultured in a medium containing serum and chick embryo extract give rise to large numbers of cells expressing immunoreactivity for substance P (SP), a neuropeptide found in sensory neurons. These cells arise from cycling precursors, but do not appear to divide after expressing SP. The SP-positive cells in cranial neural crest cultures express both neurofilament and the Q211 antigen, but those in trunk cultures express only the Q211 antigen. In both cranial and trunk cultures, large subpopulations of the SP-positive cells express tyrosine hydroxylase and/or choline acetyltransferase, neurotransmitter markers characteristic of autonomic neurons. This finding argues against the idea that SP expression necessarily indicates commitment to the sensory neuron lineage. I further show that embryonic dorsal root ganglion (DRG) cells retain the ability to coexpress SP and tyrosine hydroxylase in vitro although to a lesser extent than do neural crest cells. 相似文献
19.
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