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Methyl mercury uptake in free cells and different immobilizates of the cyanobacteriumNostoc calcicola has been examined. The general growth of the immobilized cyanobacterial cells could be negatively correlated with methyl mercury uptake. Alginate spheres proved most efficient in terms of uptake rate (0.48 nmol mg protein–1 min–1, 10 min) and total bioaccumulation (10.71 nmol mg protein–1, 1 h) with a bioconcentration factor of 3.3×103. Alginate biofilms showed a faster methyl mercury accumulation rate (0.83 nmol mg protein–1 min–1, 10 min) with a saturation of 10.28 nmol mg protein–1 reached within only 30 min (bioconcentration factor, 3.1×103). Foam preparations with a slow initial uptake approximated biofilms but were characterized by a lower bioconcentration factor (2.8×103). Free cells, in comparison, maintained the initial slow rate of uptake (0.62 nmol mg protein–1 min–1, 10 min), saturating at 30 min (8.81 nmol mg protein–1), and the resultant lowest bioconcentration factor (2.7×103). Cell ageing (30 days) brought a drastic reduction (3-fold) in organomercury uptake by free cells while alginate spheres maintained the same potential. Foam preparations of the same age showed a significant improvement in methyl mercury uptake followed by only a marginal decline in alginate biofilms. Data are discussed in the light of the physiological efficiency and longevity of immobilized cells. 相似文献
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Thirty-six cases of solitary and scintigraphically "cold" thyroid nodules were studied by fine needle aspiration (FNA) cytology, ultrasonography, radionuclide perfusion study (RPS) and xeroradiography with the aim of differentiating the neoplastic from the nonneoplastic nodules. Histologic study of the excised specimens provided the definitive diagnosis in all cases. Of the techniques used in this study, FNA cytology and RPS had the highest sensitivities and specificities. Ultrasonography and xeroradiography were of limited use due to their low sensitivity rates. 相似文献
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Summary The susceptibility of 50 drug resistant strains of Escherichia coli of human gut was determined against ciprofloxacin, acridine orange (AO) and sodium dodecyl sulphate (SDS). Curing efficacy of these agents were worked out at subminimal inhibitory concentrations. Ciprofloaxacin was found a better curing agent for E coli R-plasmids, eliminating R-factors from 48% of the strains followed by SDS and AO which eliminated 24% and 20% of the drug resistance determinants, respectively. Elimination of R-plasmids was found dependent on the concentrations of curing agents and nature of R-plasmids. 相似文献
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Changes in carbohydrate and lipid metabolism during embryonic development inAntheraea mylitta were studied. While carbohydrates were metabolized during early embryogenesis, lipids were catabolised at the later stages.
A significant increase in both total carbohydrates and glycogen on days 5 and 6 suggested the concurrent occurrence of both
gluconeogenesis and glycogenesis. As the development of the embryo proceeds, both lipids and carbohydrates were utilised,
resulting in the increase in the concentration of citrate, pyruvate and lactate. 相似文献
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Glycollic acid, supplied at a concentration of 1 mg l?1, increased the relative growth rate of Skeletonema costatum (Grev.) Cleve growing in bacterized culture at limiting light intensities. There was little or no such effect at intensities approaching saturation. The presence in the medium of alumina, an adsorbent for glycollate, prolonged the lag phase, the cells remaining viable for up to 5 days. Uptake of glycollate was not appreciably affected by the bicarbonate concentration of the medium. After 3 h, 80–92% of the glycollate carbon assimilated was found in the alcohol and benzene insoluble fraction of the cells. This is in agreement with the supposition that glycollate carbon is as-similated directly by the diatom rather than after degradation by bacteria to carbon dioxide. 相似文献
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The beneficial effect of seed priming in improving critical growth stages like seed germination and early growth phases has been accepted by Plant Physiologists for many important field crops. In the present investigation, studies were made to see the effect of heavy metal stress imposed during germination using solution of HgCl2 in four different concentrations (0.0, 0.50, 0.75 and 1.00 mM) in Petri dishes on primed and non-primed seeds of wheat. Priming has been done with distilled water (hydro), Mg(NO3)2 and Ca(NO3)2 (halo) salts. Different germination parameters, such as germination percentage, radicle and plumule lengths, seedling emergence, soluble and insoluble sugar contents and activity of α-amylase in endosperm were studied at different study periods. Primed seeds increased all the germination parameters except insoluble sugar content in respect to non-primed control in the absence of HgCl2. However, the use of primed seeds has shown to overcome the inhibitory effects of heavy metal stress imposed in the form of HgCl2 solution during the period of germination. Hence, the work concludes the mitigating effects of priming under heavy metal stress. 相似文献