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The morphological changes in the gill chloride cells of the armored catfish, Hypostomus tietensis , were investigated after 15 days' exposure to either distilled or hard water. The thickness of the water–blood barrier in the lamellae increased significantly in fish kept in distilled water due to the high proliferation of chloride cells. The apical surface of about 68% of chloride cells was sharply reduced by the development of an apical crypt with a sponge-like surface, although no change in the chloride cell fractional area was found. In contrast, H. tietensis kept in Na+ , Cl− and Ca2+ rich water displayed no significant changes in the number of chloride cells or in their apical surface morphology compared with the control fish. Chloride cell response to ion challenge in H. tietensis suggested the involvement of different strategies to maintain homeostasis in ion-poor water, which may be related to the life history of species. 相似文献
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Rapid immunofluorescent determination of cells in the S phase in pea root meristems: An alternative to autoradiography 总被引:2,自引:0,他引:2
Photosystem II (PS II) activity and the localization of ribulose-l,5-bisphosphate (RuBP) carboxylase (EC 4.1.1.39) were studied in primary leaves of young maize plants ( Zea mays L. cv. Fronica) by tetra-nitro-blue-tetrazoliumchloride reduction and immunolocalization, respectively. In tissue of 3-day-old plants all chloroplasts were structurally identical. From day 4 they developed into their typical appearance of mesophyll and bundle sheath chloroplasts. First PS II-activity was present in both types of chloroplasts. From day 4 it disappeared in bundle sheath chloroplasts concomitant with the loss of grana. RuBP carboxylase on the other hand was only present in bundle sheath chloroplasts at all stages of development. Thus, the control of the development of the photosystems and the Calvin cycle enzymes seem to differ. 相似文献
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Summary Genetic determinants of the Muc+ character were investigated in two ropy strains,Lactobacillus delbrueckii ssp.bulgaricus 201 andL. casei ssp.casei NCIB 4114, which secrete a large amount of slime in culture media. Plasmid DNA analysis revealed the presence of two plasmids (4.5 and 2.3 Mdal) inL. casei ssp.casei, whileL. delbrueckii ssp.bulgaricus was plasmid free, suggesting a chromosomal location of Muc+ character in this strain. Curing experiments carried out onL. casei ssp.casei NCIB 4114 indicated a correlation between the Muc+ phenotype and the 4.5 Mdal plasmid. 相似文献
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Agnese Molinari Graziella Orefici Gianfranco Donelli Cristina Von Hunolstein Silvia Paradisi Giuseppe Arancia 《The Histochemical journal》1988,20(9):526-530
Summary We describe the use of lectins as specific stabilizing agents for the polysaccharide capsular components of two Gram-positive bacteria,Streptococcus agalactiae andStreptococcus bovis. Treatment of bacterial suspensions with wheatgerm agglutinin and concanavalin A allowed better morphological preservation as well as immunoelectron microscopic localization of a capsular component (lipoteichoic acid) by employing specific antibodies and the protein A-gold technique. Data obtained indicate that lectins are useful agents in preserving highly water-soluble capsular components during the electron microscopy procedures for both unembedded and embedded samples. 相似文献
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Sergio Sgorbati Marisa Levi Elio Sparvoli Federica Trezzi Giovanni Lucchini 《Physiologia plantarum》1986,68(3):471-476
Cytometry and flow cytometry were used to study characteristics of fluorescence of the DNA-DAPI complex in nuclei released from different fresh and formaldehyde-fixed pea ( Pisum sativum L. cv. Lincoln) tissues. The two methods of isolation are compared and discussed as well as their possible use for quantitative analysis of DNA in plant tissues. With fixed tissues it is possible to obtain a number of nuclei sufficient for the flow cytometric analysis, even using small amounts of plant tissue. 相似文献
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A statistical analysis was performed on the data resulting from an international collaborative study of the Ames test according to a standardized experimental protocol, which involved the comparative testing of 4NQO (4 doses), in 3 separate experiments for each of the 38 participating laboratories, by using a common reference (R) culture and in-house laboratory (L) cultures of 5 strains of S. typhimurium. Despite some toxicity phenomena recorded at the highest dose of 4NQO, the majority of the dose-response curves in individual laboratories were linear on a bi-log scale and their mean values fitted a linear regression framework. Scattering of data around mean values of laboratories was Gaussian-like even at the highest dose of 4NQO, toxic effects being expressed as a dose-related increase of variance. A weighted least-square analysis could therefore take into account toxic effects without resorting to a sophisticated non-linear model incompatible with log transformation. Various analytical approaches--e.g. the weighted estimates of linear regression parameters, a multifactor (laboratory, experiment, dose, culture of each strain) analysis of variance with all the possible interactions, the assessment of correlations in individual laboratories and of coefficients of variation for induced and spontaneous mutability--could detect some statistically significant differences between L and R cultures. However, at a critical evaluation on an individual basis, only few of these differences, without any peculiar involvement of given strains, were convincing in view of the existence of real phenomena of genetic drift. Therefore, on the whole, the genetic drift of Salmonella tester strains appears to lend a negligible contribution to the considerable inter- and intra-laboratory variability detected in this study. With a background variability between replications averaging 26%, a dose-related variability was evident both between experiments (28-54%) and between laboratories (44-127%). 相似文献
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The reaction of ribose with horseradish peroxidase in the presence of H2O2 is accompanied by light emission. The detection of horseradish peroxidase Compound II (FeO2+) indicates that the enzyme participates in a normal peroxidatic cycle. Hydrogen peroxide converts horseradish peroxidase into Compound I (FeO3+) which in turn is converted into Compound II by abstracting a hydrogen atom from ribose forming a ribosyl radical. In aerated solutions oxygen rapidly adds to the ribosyl radical. Based on the spectral characteristics and the enhancement of the chemiluminescence by chlorophyll-a, xanthene dyes, D2O and DABCO, it is suggested that the excited species, apparently triplet carbonyls and 1O2, are formed from the bimolecular decay of the peroxyl radicals via the Russell mechanism. 相似文献
10.
B. Eva Villaroya Luis A. Oro Fernando J. Lahoz Andrew J. Edwards Miguel A. Ciriano Pablo J. Alonso Antonio Tiripicchio Marisa Titipicchio Camellini 《Inorganica chimica acta》1996,250(1-2):241-264
The multiple coordination possibilities of 1,8-naphthyridine-2-one (HOnapy) and 5,7-dimethyl-1,8-napthyridine-2-one (HOMe2napy) ligands allow the synthesis of a variety of tri- di- and mononuclear complexes, showing fluxional behaviour and frequent exchange of the coordinated ML2 fragments. Thus, reactions of [M2(μ-OMe)2(cod)2] (cod = 1,5-cyclooctadiene) with HOnapy and HOMe2napy yield the compounds of the general formula [M(μ-OR2napy) (cod)]n (M = Ir, R = Me (1a, 1b, H (2); M = Rh, R = Me (3a, 3b). They crystallise as inconvertible yellow (a) and purple/orange (b) forms and also show a puzzling behaviour in solution. X-ray diffraction studies on both forms (3a, 3b) and spectroscopic data reveal that the yellow forms are mononuclear complexes whilst the dark-coloured crystals contain dinuclear complexes. In solution, the nuclearity of the complexes depends on the solvent. In addition both types of complexes are fluxional. The mixed-ligand complexes [M2(μ-OMe2napy)2(CO)2(cod)] M = Ir (5), Rh (6) have been isolated and characterised; they are found to be intermediates in the synthesis of the trinuclear complexes [M3(μ3-OMe2napy)2(CO)2(cod)2]+ M = Rh (8), Ir (9). Reactions of [IrCl(CO)2(NH2-p-tolyl] with the complexes [Rh(μ-OR2napy)(diolefin)]n followed by addition of a poor donor anion is a general one-pot synthesis for the hetertrinuclear complexes [Rh2Ir(μ3-OR2napy)2(CO)2(diolefin)2]+ (R=Me, DIOLEFIN = cod (10), tetrafluorobenzo-barrelene (tfbb) (11), 2,5-norbornadiene (nbd) (12); R=H, DIOLEFIN=cod (13)). This synthesis follows a stepwise mechanism from the mononuclear to the trinuclear complexes in which mixed-ligand heterodinuclear complexes are involved as intermediates of the type [(diolefin)Rh(μ-OMe2napy)2Ir(CO)2]. Heteronuclear complexes which possess the core [RhIr2]3+, such as [RhIr2(μ3-OR2napy)2(CO)2(cod)2]BF4 (R=Me (14), H (15)), result from the reaction of 1 or 2 with [Rh(CO)2Sx]+ (S = solvent). The trinuclear complexes undergo two chemically reversible one-electron oxidation processes. The chemical oxidation of 10, 14 and 9 with silver salts gives the mixed-valence trinuclear radicals [Rh2Ir(μ3-OMe2napy)2(CO)2(cod)2]2+ (16), [RhIr2(μ3-OMe2napy)2(CO)2(cod)2]2+ (17) and [Ir3(μ3-OMe2napy)2(CO)2(cod)2]2+ (18), which have been isolated as the perchlorate and tetrafluoroborate salts. The EPR spectrum of 16 indicates that the unpaired electron is essentially in an orbital delocalised on the metals. The molecular structures of the complexes 3a, 3b, 6, 10b and 16a are described. Crystals of 3a are triclinic, P-1, with a = 9.7393(2), b = 14.0148(4), c = 16.0607(4) Å, α = 88.122(3), β = 83.924(3), γ = 87.038(3)°, Z = 4; 3b crystallises in the Pna2i orthorhhombic space group, with a = 16.7541(3), B = 11.7500(8), c = 17.7508(7) Å, Z = 4; complex 6 is packed in the monoclinic space group P2i/c, a = 9.6371(1), b = 11.8054(4), c = 27.2010(9) Å, β = 90.556(4)°, Z = 4; crystals of 10b are monoclinic, P21/n, with a = 17.546(7), b = 13.232(6), c = 17.437(8) Å, β = 106.18(1)°, Z = 4; crystals of 16a are triclinic, P-1, with a = 10.318(4), b = 12.562(6), C = 19.308(8) Å, α = 92.12(8), β = 97.65(9), γ = 90.68(5)°, Z = 2. The five different structures show the coordination versatility of the OMe2napy molecule as ligand, which behaves as a N,N′-chelating (3a), bidentate N,O-donor (3b, 6), or as a tridentate N,N′,O-donor bridging ligand (10b, 16a). 相似文献