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1.
Self-organized nanogels responding to tumor extracellular pH: pH-dependent drug release and in vitro cytotoxicity against MCF-7 cells 总被引:1,自引:0,他引:1
The principal objective of this study was to fabricate doxorubicin-loaded self-organized nanogels composed of hydrophobized pullulan (PUL)-Nalpha-Boc-L-histidine (bHis) conjugates. Their responses to tumor extracellular pH (pHe) were determined, and they were also evaluated with regard to their anticancer efficacy against breast cancer cell lines (MCF-7). bHis was grafted to a PUL-deoxycholic acid (DO) conjugate (PUL-DO) via an ester linkage. PUL-DO/bHis conjugates with two different degrees of bHis substitutions (PUL-DO/bHis36 and PUL-DO/bHis78) were synthesized. PUL-DO/bHis nanogels formed via dialysis at a pH of 8.5 evidenced larger particle sizes (<140 nm) and lower critical aggregation concentrations (CACs) than did the PUL-DO nanogels (90 nm). The pH-dependent CAC of PUL-DO/bHis78 changed dramatically, from 1.2 microg/mL at pH 8.5, to 10 at 7.0, and to 660 at 6.2. A similar tendency in pH-dependent size was also noted. The ionization of the imidazole ring in bHis is principally responsible for pH dependency. The bHis moieties function as a switching tool responding to external pH. Doxorubicin (DOX)-loaded nanogels were assessed for pH-dependent releasing kinetics. The release rate of DOX from the PUL-DO/bHis78 nanogels increased significantly with reductions in pH. This resulted in increased cytotoxicity (30% cell viability at a dose of 10 microg/mL DOX equivalent) against sensitive MCF-7 cells at a pH of 6.8 and low cytotoxicity at pH 7.4 (65% cell viability at an identical dose). The results show that PUL-DO/bHis nanogels may potentially be employed as anti-tumor drug carriers. 相似文献
2.
Yan Hu Xianran He Lei Lei Shucai Liang Guofu Qiu Xianming Hu 《Carbohydrate polymers》2008,74(2):220-227
Various novel carboxymethyl pachyman-deoxycholic acid conjugates (CMPD) were synthesized using carboxymethylated pachyman (CMP) as a hydrophilic segment and Deoxycholic Acid (DOCA) as a hydrophobic segment. The degree of DOCA substitution (DS) in CMPD conjugates, which was determined by elemental analysis, can reach to 30.0, 49.2, or 54.9 DOCA groups per hundred sugar residues of CMP. Structural characteristics of these CMPD conjugates were investigated by using 1H NMR, dynamic light scattering, zeta potential, transmission electron microscopy (TEM) and fluorescence spectroscopy. The CMPD conjugates provided apparently smaller monodispersed self-aggregates in water, with mean diameters decreasing with increasing of DOCA DS in the range of 98–158 nm. Zeta potentials of the CMPD self-aggregated nanoparticles indicated that the nanoparticles were covered with negatively charged CMP shells. TEM images demonstrated that the nanoparticles were spherical in shape. The critical aggregation concentration (cac) of the CMPD nanoparticles (1.55 × 10−2–5.89 × 10−3 mg/mL) was comparatively low which implies that the CMPD self-assembled nanoparticles form at low concentration in aqueous solution. 相似文献
3.
Sarigüllü Ozgüney I Yeşim Karasulu H Kantarci G Sözer S Güneri T Ertan G 《AAPS PharmSciTech》2006,7(4):E39-E45
The aim of this study was to evaluate and compare the in vitro and in vivo transdermal potential of w/o microemulsion (M)
and gel (G) bases for diclofenac sodium (DS). The effect of dimethyl sulfoxide (DMSO) as a penetration enhancer was also examined
when it was added to the M formulation. To study the in vitro potential of these formulations, permeation studies were performed
with Franz diffusion cells using excised dorsal rat skin. To investigate their in vivo performance, a carrageenan-induced
rat paw edema model was used. The commercial formulation of DS (C) was used as a reference formulation. The results of the
in vitro permeation studies and the paw edema tests were analyzed by repeated-measures analysis of variance. The in vitro
permeation studies found that M was superior to G and C and that adding DMSO to M increased the permeation rate. The permeability
coefficients (Kp) of DS from M and M+DMSO were higher (Kp=4.9×10−3±3.6×10−4 cm/h and 5.3×10−3±1.2×10−3 cm/h, respectively) than the Kp of DS from C (Kp=2.7×10−3±7.3×10−4 cm/h) and G (Kp=4.5×10−3±4.5×10−5 cm/h). In the paw edema test, M showed the best permeation and effectiveness, and M+DMSO had nearly the same effect as M.
The in vitro and in vivo studies showed that M could be a new, alternative dosage form for effective therapy. 相似文献
4.
Chung Eun Chang Seung-Cheol Kim Jae-Seong So Hyun Shik Yun 《Biotechnology and Bioprocess Engineering》2001,6(2):128-132
Bacterial vaginosis can be treated by restoring the normal vaginal flora using lactobacilli.Lactobacillus crispatus KLB46 that was isolated from the human vagina has a strong antimicrobial activity and was grown in a batch and in a continuous
fermentor. During batch cultivation, the maximum specific growth rate ofL. crispatus KLB 46 was 0.63 h−1 and the highest viable cell count (1.9×109 CFU/mL) was obtained at pH 5.5.L. crispatus KLB 46 did not grow well at either pH 3.5 or 7.5. During continuous cultivation, the highest viable cell count (1.53×109 CFU/mL) was obtained at a dilution rate of 0.32 h−1. However, the maximum productivity of viable cells was obtained at a dilution rate of 0.52 h−1, and was 7.33×1011 CFU L−1 h−1, that is approximately 5 times higher than that obtained from batch culture. 相似文献
5.
Determination of the kinetics of permeation of dimethyl sulfoxide in isolated corneas 总被引:2,自引:0,他引:2
Corneal cryopreservation requires that endothelial cells remain viable and intercellular structure be preserved. High viability
levels for cryopreserved endothelial cells have been achieved, but preserving intercellular structure, especially endothelial
attachment to Descemet's membrane, has proved difficult. Cell detachment apparently is not caused by ice, suggesting osmotic
or chemical mechanisms. Knowledge of the permeation kinetics of cryoprotectants (CPAs) into endothelial cells and stroma is
essential for controlling osmotic and chemical activity and achieving adequate tissue permeation prior to cooling. Proton
nuclear magnetic resonance (NMR) spectroscopy was used to assess the permeation of dimethyl sulfoxide (DMSO) into isolated
rabbit corneas. Corneas with intact epithelia were exposed to isotonic medium or 2.0 mol/L DMSO for 60 min and subsequently
transferred to 2.0 or 4.0 mol/L DMSO, respectively, at 22, 0, or −10°C. DMSO concentration in the cornea was measured vs time.
The Kedem-Katchalsky model was fitted to the data. Hydraulic permeability (m3/N·s) is 7.1×10−13+216%-11% at 22°C, 8.2×10−13+235%−21% at 0°C, and 1.7×10−14+19% −16% at −10°C. The reflection coefficient is 1.0+2%−1% at 22°C and 0°C, and 0.9±5% at −10°C. Solute mobility (cm/s) is
5.9×10−6+6%–11% at 22°C, 3.1×10−6+12%−11% at 0°C, and 5.0×10−8 cm/s+59%−40% at −10°C. 相似文献
6.
The chronic effect (duration of exposure 218 days) of polychlorinated biphenyls (PCBs) and the prolonged effect of the short-term
action of chlorophos or of N-methyl-N′-nitro-N-nitrosoguanidine (MNNG) during embryogenesis upon the sensitivity of intestinal glycosidases to Cu and Zn was studied in
roach (Rutilus rutilus (L.) underyearlings. The Cu+2 and Zn+2 ions at concentrations ranging from 0.1 to 25 mg/L in vitro cause a 10–77% decrease in amylolytic activity in the intestinal
mucosa of control roach. An elevated level of PCBs (50.8 ng/g wet weight of food and 426 ng/g dry weight of ground) increased
the sensitivity of glycosidases to Cu and Zn. The embryotoxic action of chlorophos at concentrations of 1 × 10−6−1 × 10−2 mg/L in most cases increased the inhibitory effect of Cu but decreased that of Zn. As a rule, MNNG (3 × 10−7−3 × 10−1 mg/L) reduced the glycosidase sensitivity to the effect of metal ions. The magnitude and direction of the effect depend on
the nature and concentration of toxicants. 相似文献
7.
O. M. Tsivileva E. A. Loshchinina O. E. Makarov V. E. Nikitina 《Applied Biochemistry and Microbiology》2012,48(3):280-289
The auxin formation in a submerged culture of the xylotrophic basidiomycete Lentinus edodes (Berk.) Sing (Lentinula edodes (Berk.) Pegler) (shiitake) is studied. Biologically active substances of an indole nature are identified, “the effect of
small doses” of which lies in not only the stimulation of growth of the mycelium (indole-3-acetic acid, 2 × 10−7–2 × 10−4 g/l), but also in the induction of tryptophan-independent paths of auxin biosynthesis. The above-mentioned path is realized
in the presence of exogenous indole (1 × 10−3–1 × 10−4 g/l), as well as while inducing the biosynthesis of indole-3-acetic acid by its microadditives (1 × 10−5−1 × 10−8 g/l), and is accompanied by the formation of anthranilic acid (up to 1.5 mg/l). Induction of the generative development stage
of shiitake by indole derivatives is revealed. It was found that among the studied compounds only indoleacetamide at a concentration
of an order of ×10−4 g/l in the culture fluid of L. edodes had a pronounced stimulatory effect on the formation of shiitake’s brown mycelial film. 相似文献
8.
Yong Hua He Dong Sheng Shen Cheng Ran Fang Yin Mei Zhu 《World journal of microbiology & biotechnology》2006,22(10):1095-1104
Summary Four strains of bacteria, 9 strains of fungi and 20 strains of actinomycetes capable of utilizing metsulfuron-methyl as sole carbon and energy source were isolated from a metsulfuron-methyl-treated soil by the enrichment culture method. A fungus named DS11F was selected as the most highly effective one according to the maximum tolerance concentration of 1,200 mg l−1 and metsulfuron-methyl-degrading rate of 0.0716 g g−1 cells h−1, and was identified as an unknown strain of Penicillium sp. on the basis of colony growth, morphology and biochemical characteristics.␣Through liquid pure culture, the optimal metsulfuron-methyl-degrading conditions of DS11F were determined to be metsulfuron-methyl concentration 22.6 mg l−1, inoculum concentration 12.25 mg l−1, pH 7.0 and temperature 30°C. As additional C sources, supernatant of soaked compost could increase metsulfuron-methyl degradation by 8%, but glucose was ineffective. DS11F inoculation was found to significantly enhance the degradation of metsulfuron-methyl in soil, with the reduction of the concentration reaching 50% in 6 days. Admixture of compost could promote metsulfuron-methyl degradation to some extent. The growth of the inocula in the soils remained dominant and degradation resumed immediately when metsulfuron-methyl was applied again. The results show that addition of the isolated Penicillium sp. enhances the degradation of metsulfuron-methyl in water and soil. 相似文献
9.
Zhan F Chen W Wang Z Lu W Cheng R Deng C Meng F Liu H Zhong Z 《Biomacromolecules》2011,12(10):3612-3620
Endosomal pH-activatable doxorubicin (DOX) prodrug nanogels were designed, prepared, and investigated for triggered intracellular drug release in cancer cells. DOX prodrugs with drug grafting contents of 3.9, 5.7, and 11.7 wt % (denoted as prodrugs 1, 2, and 3, respectively) were conveniently obtained by sequential treatment of poly(ethylene glycol)-b-poly(2-hydroxyethyl methacrylate-co-ethyl glycinate methacrylamide) (PEG-b-P(HEMA-co-EGMA)) copolymers with hydrazine and doxorubicin hydrochloride. Notably, prodrugs 1, 2, and 3 formed monodispersed nanogels with average sizes of 114.4, 75.3, and 66.3 nm, respectively, in phosphate buffer (PB, 10 mM, pH 7.4). The in vitro release results showed that DOX was released rapidly and nearly quantitatively from DOX prodrug nanogels at endosomal pH and 37 °C in 48 h, whereas only a minor amount (ca. 20% or less) of drug was released at pH 7.4 under otherwise the same conditions. Confocal laser scanning microscope (CLSM) observations revealed that DOX prodrug nanogels delivered and released DOX into the cytosols as well as cell nuclei of RAW 264.7 cells following 24 h incubation. MTT assays demonstrated that prodrug 3 had pronounced cytotoxic effects to tumor cells following 72 h incubation with IC(50) data determined to be 2.0 and 3.4 μg DOX equiv/mL for RAW 264.7 and MCF-7 tumor cells, respectively. The corresponding polymer carrier, PEG-b-P(HEMA-co-GMA-hydrazide), was shown to be nontoxic up to a tested concentration of 1.32 mg/mL. These endosomal pH-activatable DOX prodrug nanogels uniquely combining features of water-soluble macromolecular prodrugs and nanogels offer a promising platform for targeted cancer therapy. 相似文献
10.
Sharma Madhu Sood Anil Nagar P.K. Prakash Om Ahuja Paramvir Singh 《Plant Cell, Tissue and Organ Culture》1999,58(2):111-118
Micropropagation of tea (Camellia sinensis (L.) O. Kuntze) has been widely attempted but commercial exploitation of this method is limited by heavy losses during the
hardening procedures. In the present study, optimization of time of harvesting (spring and early summer) of microshoots, shoot
size, soil pH (4.0–6.4), plant growth regulator treatment (IBA; 500 mg l-1, 30 min) CO2 (9.09/10×10−5 mol l-1 to 10.22/10×10-5 mol l-1 and 20/11×10−5 mol l-1 to 80/13×10−7 mol l-1) enrichment and light (15 μ mol m-2 s-1) conditions in specially designed hardening chambers, made a significant impact on the percent of success for hardening.
Following the standardized procedure, up to 71.6% root induction and 73% survival could be achieved. Successful field transfer
was also accomplished.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
11.
Paclitaxel and 10-deacetylbaccatin III (10-DAB III) were produced in suspension cultures of Taxus × media var. Hicksii grown in shake-flasks and in a 7-l bioreactor reaching, in the bioreactor, 4.4 mg l−1 (on day 14) and 37.5 mg l−1 (on day 11). In shake-flasks the highest total content of paclitaxel and 10-DAB III was 7.3 mg l−1 (on day 4) and 8.8 mg l−1 (on day 18). Phenylalanine, at 0.05 mM, increased paclitaxel accumulation in cells cultivated in bioreactor and flasks 30-fold and 9-fold (from 0.02 mg l−1 to 0.6 mg l−1 and to 0.2 mg l−1, respectively). The 10-DAB III content in cells from flasks was increased from 0.4 mg l−1 to 1.6 mg l−1. 相似文献
12.
Combination of dextran sulfate and recombinant trypsin on aggregation of Chinese hamster ovary cells
Yu Jing Cunchao Zhang Tuo Fu Cheng Jiang Kai Ma Dapeng Zhang Sheng Hou Jianxin Dai Hao Wang Xueguang Zhang Geng Kou Yajun Guo 《Cytotechnology》2016,68(2):241-248
In laboratory scale therapeutical protein production, cell clumps form typically in shake flasks, which hinders cell growth and decreases protein yield. To minimize clumps during the culture of Chinese hamster ovary cells, we employed the combination of two reagents, dextran sulfate (DS) and recombinant trypsin (r-trypsin). Our results showed that both DS and r-trypsin could diminish cell aggregation when adding them respectively, but clumps were still noticed obviously. In order to further mitigate cell agglomerate, a combination of 1.2 g/L DS and 8.0 mg/L r-trypsin was employed and no clumps were found under the bright field microscope. Strikingly, the highest viable cell density of combination group was increased from 5.12 × 106 to 7.13 × 106 cells/mL, while the integral of viable cells concentration was raised from 35.13 × 106 to 60.87 × 106 cells·days/mL, and the culture period was prolonged by 4 days. In addition, the antibody integrity was maintained in the combination group compared with that of the control. 相似文献
13.
Antibody-based fusion proteins are the next generation of antibody therapies for cancer and other diseases. CD20 antigen,
which is overexpressed on cell membranes in nearly 95% of cases of B-cell Non-Hodgkin’s Lymphoma, is an attractive target
for the therapy of B-lymphoid malignancies. Lidamycin (LDM) is a potent enediyne-containing antitumor antibiotic that now
has entered phase II clinical trials. In this study, we prepared an engineered fusion protein, scFv-LDP, consisting of an
anti-CD20 scFv fragment and the apoprotein LDP of LDM using DNA recombination. After purification and refolding, scFv-LDP
was found to bind specifically to CD20-positive lymphoma cells using ELISA and indirect immunofluorescent cytochemical staining
assays. The energized fusion protein scFv-LDP-AE was obtained using molecular reconstitution of the active chromophore AE
of LDM and scFv-LDP. MTT assay revealed potent cytotoxicity of scFv-LDP-AE to CD20-positive Raji and Daudi cells, with IC50 values of 1.21×10−11 and 6.24×10−11 mol L−1, respectively. An in vivo subcutaneous xenograft model of CD20-positive B cell lymphoma in BALB/c (nu/nu) mice was also utilized. Drugs were given
intravenously on day 14 and 21 after tumor transplantation. In terms of maximal tolerated doses, scFv-LDP-AE at 0.3 mg kg−1 suppressed tumor growth by 79.3%, and LDM at 0.05 mg kg−1 by 68.6% (P<0.05). Results suggested scFv-LDP-AE could be a potential candidate for tumor-targeting therapy. 相似文献
14.
Li WB Gerstmann U Giussani A Oeh U Paretzke HG 《Radiation and environmental biophysics》2008,47(1):101-110
The mysterious death of Mr. Alexander Litvinenko who was most possibly poisoned by Polonium-210 (210Po) in November 2006 in London attracted the attention of the public to the kinetics, dosimetry and the risk of this high
radiotoxic isotope in the human body. In the present paper, the urinary excretion of seven persons who were possibly exposed
to traces of 210Po was monitored. The values measured in the GSF Radioanalytical Laboratory are in the range of natural background concentration.
To assess the effective dose received by those persons, the time-dependence of the organ equivalent dose and the effective
dose after acute ingestion and inhalation of 210Po were calculated using the biokinetic model for polonium (Po) recommended by the International Commission on Radiological
Protection (ICRP) and the one recently published by Leggett and Eckerman (L&E). The daily urinary excretion to effective dose
conversion factors for ingestion and inhalation were evaluated based on the ICRP and L&E models for members of the public.
The ingestion (inhalation) effective dose per unit intake integrated over one day is 1.7 × 10−8 (1.4 × 10−7) Sv Bq−1, 2.0 × 10−7 (9.6 × 10−7) Sv Bq−1 over 10 days, 5.2 × 10−7 (2.0 × 10−6) Sv Bq−1 over 30 days and 1.0 × 10−6 (3.0 × 10−6) Sv Bq−1 over 100 days. The daily urinary excretions after acute ingestion (inhalation) of 1 Bq of 210Po are 1.1 × 10−3 (1.0 × 10−4) on day 1, 2.0 × 10−3 (1.9 × 10−4) on day 10, 1.3 × 10−3 (1.7 × 10−4) on day 30 and 3.6 × 10−4 (8.3 × 10−5) Bq d−1 on day 100, respectively. The resulting committed effective doses range from 2.1 × 10−3 to 1.7 × 10−2 mSv by an assumption of ingestion and from 5.5 × 10−2 to 4.5 × 10−1 mSv by inhalation. For the case of Mr. Litvinenko, the mean organ absorbed dose as a function of time was calculated using
both the above stated models. The red bone marrow, the kidneys and the liver were considered as the critical organs. Assuming
a value of lethal absorbed dose of 5 Gy to the bone marrow, 6 Gy to the kidneys and 8 Gy to the liver, the amount of 210Po which Mr. Litvinenko might have ingested is therefore estimated to range from 27 to 1,408 MBq, i.e 0.2–8.5 μg, depending
on the modality of intake and on different assumptions about blood absorption. 相似文献
15.
A flow cytometric protocol for titering recombinant adenoviral vectors containing the green fluorescent protein 总被引:1,自引:0,他引:1
Hitt DC Booth JL Dandapani V Pennington LR Gimble JM Metcalf J 《Molecular biotechnology》2000,14(3):197-203
As the use of adenoviral vectors in gene therapy protocols increases, there is a corresponding need for rapid, accurate, and
reproducible titer methods. Multiple methods currently exist for determining titers of recombinant adenoviral vector, including
optical absorbence, electron microscopy, fluorescent focus assay, and the “gold standard” plaque assay. This paper introduces
a novel flow cytometric method for direct titer determination that relies on the expression of the green fluorescent protein
(GFP), a tracking marker incorporated into several adenoviral vectors. This approach was compared to the plaque assay using
10−4-to 10−6-fold dilutions of a cesium-chloride-purified, GFP expressing adenovirus (AdEasy+GFP+GAL). The two approaches yielded similar
titers: 3.25±1.85×109 PFU/mL versus 3.46±0.76×109 green fluorescent units/(gfu/mL). The flow cytometric method is complete within 24 h in contrast to the 7×10 days required
by the plaque assay. These results indicate that the GFU/mL is an alternative functional titer method for fluorescent-tagged
adenoviral vectors. 相似文献
16.
To determine the chemical and physicochemical characteristics of dissolved organic carbon in the Ado River and the Yasu River,
the main rivers flowing into Lake Biwa, the adsorption behavior onto hydrous iron oxide (HIO) and the reactivity to KMnO4 oxidant were investigated in parallel with measurement of the distribution profiles of dissolved organic carbon (DOC) along
the rivers. In one year of observation at the mouths of the two rivers, DOC concentrations were found to vary in the Ado over
the range 0.28–1.21 mg C l−1 and in the Yasu over the range 1.01–2.68 mg C l−1. Act-DOC, one of the fractions separated from the total DOC by its adsorption-active character onto HIO at pH 4, was thought
primarily to control the variation of total DOC, as in Lake Biwa. The int-DOC, another fraction separated by its adsorption-inert
or -inactive character onto HIO, remained at almost a steady value around 0.18 ± 0.07 mg C l−1 in the Ado, which was lower than that (0.35 ± 0.05 mg C l−1) in Lake Biwa. The act-DOC in river waters was reactive to KMnO4 oxidant, showing a linear relation with the amount of permanganate consumed for the reaction (chemical oxygen demand: COD).
In river waters, the relation can be approximated by a straight line expressed as COD (mg O2 l−1) = 0.64 × act-DOC (mg C l−1) − 0.02. In contrast, in the lake water the relation was COD (mg O2 l−1) = 0.97 × act-DOC (mg C l−1) − 0.50.
Received: March 3, 1999 / Accepted: December 2, 1999 相似文献
17.
Khanh Dang Vu Rajeshwar Dayal Tyagi José R. Valéro Rao Y. Surampalli 《Bioprocess and biosystems engineering》2010,33(6):691-700
Bacillus thuringiensis var. kurstaki biopesticide was produced in batch and fed-batch fermentation modes using starch industry wastewater as sole substrate. Fed-batch
fermentation with two intermittent feeds (at 10 and 20 h) during the fermentation of 72 h gave the maximum delta-endotoxin
concentration (1,672.6 mg/L) and entomotoxicity (Tx) (18.5 × 106 SBU/mL) in fermented broth which were significantly higher than maximum delta-endotoxin concentration (511.0 mg/L) and Tx
(15.8 × 106 SBU/mL) obtained in batch process. However, fed-batch fermentation with three intermittent feeds (at 10, 20 and 34 h) of
the fermentation resulted in the formation of asporogenous variant (Spo−) from 36 h to the end of fermentation (72 h) which
resulted in a significant decrease in spore and delta-endotoxin concentration and finally the Tx value. Tx of suspended pellets
(27.4 × 106 SBU/mL) obtained in fed-batch fermentation with two feeds was the highest value as compared to other cases. 相似文献
18.
David I. Dunstan Debbie P. Lashta Susan I. Kikcio Trevor A. Thorpe 《In vitro cellular & developmental biology. Plant》1992,28(1):33-38
Summary The effects of sucrose concentration, addition of ammonium nitrate, and exposure to N6-benzyl-adenine (BA) on multiplication potential with shoots derived from shoot cultures of 17- to 20-yr-old Douglas fir trees
[Pseudotsuga menziesii (Mirb.) Franco] were compared. Each of these conditions, when compared independently, affected recurrent shoot multiplication
and influenced shoot development, as measured by the abundance of shoot apices. Sucrose concentration was influential, the
use of 25 g · liter−1 providing twice the multiplication obtained with 20 g · liter−1, and 14 × that obtained with the 30 g · liter−1 concentration routinely used (tree 11). Ammonium nitrate usage also improved multiplication, a 2.5 times improvement being
obtained after incorporation of 100 mg · liter−1 NH4NO3 into the medium (tree 33). Shoot cultures were responsive but relatively sensitive to addition of BA, the best improvement
in multiplication (5 times) being obtained with brief exposures to 3 mg · liter−1 BA (tree 11). Although shoot cultures were responsive to the conditions investigated, differences in shoot multiplication
and development were not displayed for several weeks. It was not possible therefore to repeat all the treatments with more
than one genotype; however, when this was possible a genotype-dependent variation in response was evident. 相似文献
19.
Zanaty R. Komy Rabei M. Gabar Ahmed A. Shoriet Rehab M. Mohammed 《World journal of microbiology & biotechnology》2006,22(9):975-982
Summary The ability of Pseudomonas
aeruginosa to accumulate Cd(II) ions from wastewater industries was experimentally investigated and mathematically modelled. From the potentiometric titration and non-ideal competitive analysis (NICA) model, it was found that the biomass contains three acidic sites. The values of proton binding (pK
i
=1.66±3.26×10−3, 1.92±1.63×10−4 and 2.16±3.79×10−4) and binding constant of cadmium metal ions (pK
M1=1.99±2.45×10−3 and pK
M2=1.67±4.08×10−3) on the whole surface of biomass showed that protonated functional groups and biosorption of Cd(II) ions could be attributed to a monodentate binding to one acidic site, mainly the carboxylic group. From the isothermal sorption experimental data and Langmuir model, it was also found that the value of Langmuir equilibrium (pK
f) constant is 2.04±2.1×10−5 suggesting that the carboxyl group is the main active binding site. In addition, results showed that the maximum cadmium capacity (q
max) and affinity of biomass towards cadmium metal ions (b) at pH 5.1 and 20 min were 96.5±0.06 mg/g and 3.40×10−3± 2.10×10−3, respectively. Finally, interfering metal ions such as Pb(II), Cu(II), Cr(III), Zn(II), Fe(II), Mn(II), Ca(II) and Mg(II) inhibited Cd(II) uptake. Comparing the biosorption of Cd(II) by various Pseudomonas isolates from contaminated environment samples (soil and sewage treatment plant) showed that maximum capacities and equilibrium times were different, indicating that there was a discrepancy in the chemical composition between biomasses of different strains. 相似文献
20.
E. A. Kudryavtseva A. S. Savvichev S. V. Aleksandrov T. A. Kanapatskii N. V. Pimenov 《Microbiology》2012,81(3):348-359
The numbers, biomass, and production of bacterioplankton were determined in the Russian Sector of the Gdansk Basin (Baltic Sea) in 2007–2009. Significant spatial and temporal variations were determined. During the year, bacterial activity increased with increasing water temperature and higher availability of organic substrates. The lowest bacterial production (0.01–31.63 mg C m−3 day−1) was observed in late winter and late autumn, while the highest (0.17–341.70 mg C m−3 day−1) occurred in spring and summer. Since bacterial numbers and biomass were found to depend on the weather conditions and the terrigenous inflow, significant variations were observed from year to year. The highest and lowest numbers and biomass of bacterioplankton determined in summer were 0.09–1.10 × 106 cells mL−1 and 2–22 mg C m−3 for July 2007 and 1.96–11.23 × 106 cells mL−1 and 23–123 mg C m–3 for July 2009. The values of these parameters were the highest along the coast and decreased towards the open sea. 相似文献