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31.
Estimation of the size of freshwater ciliate populations by a sub-sampling technique 总被引:4,自引:4,他引:0
Paolo Madoni 《Hydrobiologia》1984,111(3):201-206
A technique is described for the estimation of the size of ciliate populations based on replicated counts. Sample drops were
taken by automatic pipettes of different volume from activated sludge and from a small oligotrophic stream. Specific aims
were: 1) the estimation of the number of species; 2) the estimation of the number of individual in each species; 3) the selection
of a suitable sub-sample size and number of replicates. For each volume the cumulative increase in species taken in successive
sub-samples was determined. For each species the minimum permissible sub-sample volume and the number of replicates required
for an allowable error of 10% and 25% were determined. Lastly, the relationship between the mean number of individuals counted
for each species and the relative coefficient of variation was visualized. 相似文献
32.
Dion tomasellii sp. nov. occurs with an interrupted distribution from Guerrero to central Sonora. It is characterized by falcate to subfalcate leaflets. The populations from Sonora and northern Sinaloa are segregated asD. tomasellii var.sonorense on the basis of their narrower and glaucous leaflets. 相似文献
33.
Giorgio M. Hanozet Barbara Giordana Paolo Parenti Andrea Guerritore 《The Journal of membrane biology》1984,81(3):233-240
Summary In brush border membrane vesicles from the midgut ofPhilosamia cynthia larvae (Lepidoptera) thel- andd-alanine uptake is dependent on a potassium gradient and on transmembrane electrical potential difference. Each isomer inhibits the uptake of the other form: inhibition ofl-alanine uptake byd-alanine is competitive, whereas inhibition ofd-alanine uptake byl-alanine is noncompetitive. Transstimulation experiments as well as the different pattern of specificity to cations suggest the existence of two transport systems. Kinetic parameters for the two transporters have been calculated both when Kout>Kin and Kout=Kin.d-alanine is actively transported also by the whole midgut, but it is not metabolized by the intestinal tissue. 相似文献
34.
The isomerization of poly-L -proline in different solvents has been studied by NMR spectroscopy. Different resonance signals for the CHα protons have been obtained for the two different helical conformations of thus compound, namely form I and form II. 相似文献
35.
36.
The effect of tryptophan on the biosynthesis of proline has been investigated. Cells of Daucus carota grown in B5 medium supplemented with 5×10–4M tryptophan acquired the ability to grow in the presence of inhibitory concentrations of azetidine-2-carboxylic acid, an analog of proline. When trp was added to carrot cell cultures at sub-growth inhibiting concentrations, overproduction of intracellular free proline was observed. An increase was also observed for lys, his, ala, leu and phe. Likewise, the addition of asparagine, glutamic acid and phenylalanine to the medium stimulated the intracellular increase of free proline and other amino acids.Abbreviations A2CA
azetidine-2-carboxylic acid
- 2,4-D
2,4-dichlorophenoxyacetic acid
- 5MT
5-methyltryptophan
- P5C
pyrroline-5-carboxylic acid
- f.wt.
fresh weight
- d.wt.
dry weight 相似文献
37.
Glyceraldehyde 3-Phosphate:NADP Reductase of Spinach Leaves : Steady State Kinetics and Effect of Inhibitors
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The steady state kinetics of glyceraldehyde 3-phosphate:NADP+ oxidoreductase (GNR) (EC 1.2.1.9) have been investigated. The enzyme exhibits hyperbolic behavior over a wide range of substrate concentrations. Double-reciprocal plots are nearly parallel or distantly convergent with limiting Km values of 2 to 5 micromolar for NADP+ and 20 to 40 micromolar for D-glyceraldehyde 3-phosphate (G3P). The velocity response to NADP+ as the varied substrate is however sigmoidal if G3P concentration exceeds 10 micromolar, whereas the response to G3P may show inhibition above this concentration. This `G3P-inhibited state' is alleviated by saturating amounts of NADP+ or NADPH. Product inhibition patterns indicate NADPH as a potent competitive inhibitor to NADP+ (Ki 30 micromolar) and mixed inhibitor towards G3P, and 3-phosphoglycerate (3PGA) as mixed inhibitor to both NADP+ and G3P (Ki 10 millimolar). The data, and those obtained with dead-end inhibitors, are consistent with a nonrapid equilibrium random mechanism with two alternative kinetic pathways. Of these, a rapid kinetic sequence (probably ordered with NADP+ binding first and G3P binding as second substrate) is dominant in the range of hyperbolic responses. A reverse reaction with 3PGA and NADPH as substrates is unlikely, and was not detected. Of a number of compounds tested, erythrose 4-phosphate (Ki 7 micromolar) and Pi (Ki 2.4 millimolar) act as competitive inhibitors to G3P (uncompetitive towards NADP+) and are likely to affect the in vivo activity. Ribose 5-phosphate, phosphoenolpyruvate, ATP, and ADP are also somewhat inhibitory. Full GNR activity in the leaf seems to be allowed only under high photosynthesis conditions, when levels of several inhibitors are low and substrate is high. We suggest that a main function of leaf GNR is to supply NADPH required for photorespiration, the reaction product 3PGA being cycled back to chloroplasts. 相似文献
38.
Analyses of wheat/rye addition lines by Southern blotting confirmed the presence of sequences related to theSec 1, Sec 2, andSec 3 loci on chromosomes 1R and 2R. Comparison of the 1R and 2R addition lines allowed the identification of -secalin genes atSec 1 andSec 2, respectively, while -secalin and -secalin genes atSec 1 were discriminated by comparative hybridization with three probes: -secalin, total -secalin, and 3 -secalin. The high molecular weight (HMW) secalin genes atSec 3 were identified using a homologous HMW subunit probe from wheat. Gene copy numbers were estimated as about 40–60 for -secalins, 5–10 for -secalins, and 2 for HMW secalins. Comparison of individual plants of cv. Gazelle showed a high degree of polymorphism, particularly for sequences related to -secalins and HMW secalins. 相似文献
39.
Alessandro Stefani Antonio Pisani Nicola B. Mercuri Paolo Calabresi 《Molecular neurobiology》1996,13(1):81-95
Glutamatergic transmission in the central nervous system (CNS) is mediated by ionotropic, ligand-gated receptors (iGluRs), and metabotropic receptors (mGluRs). mGluRs are coupled to GTP-binding regulatory proteins (G-proteins) and modulate different second messenger pathways. Multiple effects have been described following their activation; among others, regulation of fast synaptic transmission, changes in synaptic plasticity, and modification of the threshold for seizure generation. Some of the major roles played by the activation of mGluRs might depend on the modulation of high-voltage-activated (HVA) calcium (Ca2+) currents. Some HVA Ca2+ channels (N-, P-, and Q-type channels) are signaling components at most presynaptic active zones. Their mGluR-mediated inhibition reduces synaptic transmission. The interference, by agonists at mGluRs, on L-type channels might affect the repetitive neuronal firing behavior and the integration of complex events at the somatic level. In addition, the mGluR-mediated effects on voltagegated Ca2+ signals have been suggested to strongly influence neurotoxicity. Rather different coupling mechanisms underlie the relation between mGluRs and Ca2+ currents: Together with a fast, membrane-delimited mechanism of action, much slower responses, involving intracellular second messengers, have also been postulated. In the recent past, the relative paucity of selective agonists and antagonists for the different subclasses of mGluRs had hampered the clear definition of the roles of mGluRs in brain function. However, the recent availability of new pharmacological tools is promising to provide a better understanding of the neuronal functions related to different mGluR subtypes. The analysis of the mGluR-mediated modulation of Ca2+ conductances will probably offer new insights into the characterization of synaptic transmission and the development of neuroprotective agents. 相似文献
40.
A preliminary report on the use of transfer factor for treating stage D3 hormone-unresponsive metastatic prostate cancer 总被引:4,自引:0,他引:4
Dr. Giancarlo Pizza Caterina De Vinci Diego Cuzzocrea Domenico Menniti Ernesto Aiello Paolo Maver Giuseppe Corrado Piero Romagnoli Ennio Dragoni Giuseppe LoConte Umberto Riolo Aldopaolo Palareti Paolo Zucchelli Vittorio Fornarola Dimitri Viza 《Biotherapy》1996,9(1-3):123-132
As conventional treatments are unsuccessful, the survival rate of stage D3 prostate cancer patients is poor. Reports have
suggested the existence of humoral and cell-mediated immunity (CMI) against prostate cancer tumour-associated antigens (TAA).
These observations prompted us to treat stage D3 prostate cancer patients with an in vitro produced transfer factor (TF) able
to transfer, in vitro and in vivo, CMI against bladder and prostate TAA. Fifty patients entered this study and received one
intramuscular injection of 2–5 units of specific TF monthly. Follow-up, ranging from 1 to 9 years, showed that complete remission
was achieved in 2 patients, partial remission in 6, and no progression of metastatic disease in 14. The median survival was
126 weeks, higher than the survival rates reported in the literature for patients of the same stage. 相似文献