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1.
Chow-Chin Tong Yew-Keong Choong Nor-Aini-B Umar Mohamed-Mustapha Noordin Suhaila Mohamed 《World journal of microbiology & biotechnology》2009,25(4):687-695
Ganoderma lucidum powder using hot water and methanol extraction methods indicated a twofold more active cytotoxic activity with IC50 of 44 ± 3.8 μg/ml in the latter method. The representative dose-response curves of the G. lucidum crude extracts on J558 cell-lines revealed that there were great similarities between the curves which reflected rapid killing
activities. The percentage viability of the J558 cell exposed to these crude extracts was dose dependent only up to 150 μg/ml.
After which, there was no significant reduction when the dose was increased to 200 or 400 μg/ml. The morphological alterations
induced by the crude extract were examined under the phase contrast, fluorescent and electron microscopy. When J558 cells
were treated with doses higher than 50 μg/ml of the crude extract, obvious morphological changes and apoptosis occurred after
72 h. At 400 μg/ml, most of the cells showed necrosis characterized as small fragments with uniformly stained red nuclei.
The apoptotic and necrotic cells increased by 16.5 and 29.1%, respectively whereas the viable cells decreased by as much as
45.6. The mode of cell death via apoptosis was 3.6% higher than necrosis. However, these morphological changes were not observed
in the case of 3T3 cells. Results obtained from scanning electron microscopy and transmission electron microscopy further
confirmed the occurrence of various apoptotic and necrotic features. 相似文献
2.
Monteiro CM Brandão TR Castro PM Malcata FX 《Applied microbiology and biotechnology》2012,94(1):91-100
Microorganisms isolated from sites contaminated with heavy metals usually possess a higher removal capacity than strains from
regular cultures. Heavy metal-containing soil samples from an industrial dumpsite in Northern Portugal were accordingly collected;
following enrichment under metal stress, a consortium of wild microalgae was obtained. Their ability to grow in the presence
of, and their capacity to recover heavy metals was comprehensively studied; the datasets thus generated were fitted to by
a combined model of biomass growth and metal uptake, derived from first principles. After exposure to 15 and 25 mg/L Zn2+ for 6 days, the microalgal consortium reached similar, or higher cell density than the control; however, under 50 and 65 mg/L
Zn2+, 71% to 84% inhibition was observed. Growth in the presence of Hg2+ was significantly inhibited, even at a concentration as low as 25 μg/L, and 90% inhibition was observed above 100 μg/L. The
maximum amount of Zn2+ removed was 21.3 mg/L, upon exposure to 25 mg/L for 6 day, whereas the maximum removal of Hg2+ was 335 μg/L, upon 6 day in the presence of 350 μg/L. The aforementioned mechanistic model was built upon Monod assumptions
(including heavy metal inhibition), coupled with Leudeking–Piret relationships between the rates of biomass growth and metal
removal. The overall fits were good under all experimental conditions tested, thus conveying a useful tool for rational optimisation
of microalga-mediated bioremediation. 相似文献
3.
Hélio V. Nobre-Júnior Ricardo A. Oliveira Flavio D. Maia Marcelle A. S. Nogueira Manoel Odorico de Moraes Mary Anne M. Bandeira Geanne M. Andrade Glauce S. B. Viana 《Neurochemical research》2009,34(6):1066-1075
In the present work, we showed that a chalcone-enriched fraction (CEF) isolated from the stem bark of a Brazilian medicinal
plant, Myracrodruon
urundeuva, presents neuroprotective actions on 6-hydroxydopamine (6-OHDA)-induced neuronal cell death, in rat mesencephalic cells.
In the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium] assay, which is an index of cell viability, CEF (1–100 μg/ml)
reversed in a concentration-dependent manner the 6-OHDA-induced cell death. While cells exposed to 6-OHDA (40 μM) showed an
increased concentration of thiobarbituric acid reactive substances (TBARS), the pretreatment with CEF (10–100 μg/ml) significantly
decreased the 6-OHDA-induced TBARS formation, indicative of a neuroprotection against lipoperoxidation. Furthermore, the drastic
increase of nitrite levels induced by 6-OHDA, indicative of nitric oxide formation and free radicals production, was prevented
by CEF. Double staining with acridine orange/ethidium bromide showed that cultures exposed to 6-OHDA (40 and 200 μM) presented
an increase of apoptotic and necrotic cell numbers in a concentration-dependent manner. CEF (100 μg/ml) protected cells from
apoptosis and necrosis and increased number of cells presenting a normal morphology. The immunohistochemical analysis for
tyrosine hydroxylase (TH) positive neurons indicated that 6-OHDA (40 and 200 μM) caused a concentration-dependent loss of
TH+ and TH− neurons. CEF protected both cells types from 6-OHDA-induced cell death. All together, our results demonstrated
neuroprotective effects of chalcones, which are able to reduce oxidative stress and apoptotic injury caused by 6-OHDA. Our
findings suggest that chalcones could provide benefits, along with other therapies, in neurodegenerative injuries, such as
Parkinson’s disease. 相似文献
4.
Canová NK Kmonícková E Martínek J Zídek Z Farghali H 《Cell biology and toxicology》2007,23(5):337-354
Increased cytosolic calcium ([Ca2+]
i
) and nitric oxide (NO) are suggested to be associated with apoptosis that is a main feature of many liver diseases and is
characterized by biochemical and morphological features. We sought to investigate the events of increase in [Ca2+]
i
and endoplasmic reticulum (ER) calcium depletion by thapsigargin (TG), a selective inhibitor of sarco-ER-Ca2+-ATPases, in relation to NO production and apoptotic and necrotic markers of cell death in primary rat hepatocyte culture.
Cultured hepatocytes were treated with TG (1 and 5 μmol/L) for 0–24 or 24–48 h. NO production and inducible NO synthase (iNOS)
expression were determined as nitrite levels and by iNOS-specific antibody, respectively. Hepatocyte apoptosis was estimated
by caspase-3 activity, cytosolic cytochrome c content and DNA fragmentation, and morphologically using Annexin-V/propidium iodide staining. Hepatocyte viability and mitochondrial
activity were evaluated by ALT leakage and MTT test. Increasing basal [Ca2+]
i
by TG, NO production and apoptotic/necrotic parameters were altered in different ways, depending on TG concentration and
incubation time. During 0–24 h, TG dose-dependently decreased iNOS-mediated spontaneous NO production and simultaneously enhanced
hepatocyte apoptosis. In addition, TG 5 μmol/L produced secondary necrosis. During 24–48 h, TG dose-dependently enhanced basal
NO production and rate of necrosis. TG 5 μmol/L further promoted mitochondrial damage as demonstrated by cytochrome c release. A selective iNOS inhibitor, aminoguanidine, suppressed TG-stimulated NO production and ALT leakage from hepatocytes
after 24–48 h. Our data suggest that the extent of the [Ca2+]
i
increase and the modulation of NO production due to TG treatment contribute to hepatocyte apoptotic and/or necrotic events. 相似文献
5.
D. Claveau I. Pellerin M. Leclerc M.G. Brunette 《The Journal of membrane biology》1998,165(3):265-274
In the rabbit as well as the rat, a Na+/H+ exchanger is expressed in the apical membrane of both the proximal and distal tubules of the renal cortex. Whereas the isoform
derived from the proximal tubule has been extensively studied, little information is available concerning the distal luminal
membrane isoform. To better characterize the latter isoform, we purified rabbit proximal and distal tubules, and examined
the ethylpropylamiloride (EIPA)-sensitive 22Na uptake by the luminal membrane vesicles from the two segments. The presence of 100 μm EIPA in the membrane suspension decreased the 15 sec Na+ uptake to 75.70 ± 4.70% and 50.30 ± 2.23% of the control values in vesicles from proximal and distal tubules, respectively.
The effect of EIPA on 35 mm Na+ uptake was concentration dependent, with a IC50 of 700 μm and 75 μm for the proximal and distal luminal membranes. Whereas the proximal tubule membrane isoform was insensitive to cimetidine
and clonidine up to a concentration of 2 mm, the 35 mm Na+ uptake by the distal membrane was strongly inhibited by cimetidine (IC50 700 μm) and modestly inhibited by clonidine (IC50 1.6 mm).
The incubation of proximal tubule suspensions with 1 mm (Bu2) cAMP decreased the 15-sec EIPA-sensitive Na+ uptake by the brush border membranes to 24.1 ± 2.38% of the control values. Unexpectedly, the same treatment of distal tubules
enhanced this uptake by 46.5 ± 10.3%. Finally, incubation of tubule suspensions with 100 nm phorbol 12-myristate 13-acetate (PMA) decreased the exchanger activity to 58.6 ± 3.04% and 79.7 ± 3.21% of the control values
in the proximal and distal luminal membranes, respectively. In conclusion, the high sensitivity of the distal luminal membrane
exchanger to various inhibitors, and its stimulation by cAMP-dependent protein kinase A, indicate that this isoform differs
from that of the proximal tubule and probably corresponds to isoform 1.
Received: 6 March 1998/Revised: 6 July 1998 相似文献
6.
Cells stimulated with physiological stimuli usually exhibit oscillations in cytosolic Ca2+ concentration ([Ca2+]i), a signal playing central roles in regulation of various cellular processes. For explicating their unknown mechanisms, studies
are commonly conducted in single cells from several cell lines, in particular the human epithelial kidney (HEK293) cell line.
However, [Ca2+]i oscillating responses to agonists in vitro are found difficult to be induced and varied with different types of cells and
agonists. This study shows that treatment of the wild type HEK293 cells with low concentrations of carbachol (1–10 μM), an
agonist of the muscarinic receptor, resulted in non-oscillated but sustained [Ca2+]i increase by loading the cells with 1 μM fura2/AM. However, repetitive and long lasting [Ca2+]i oscillations could be induced in 31.1% of the tested cells loaded with 0.1 μM fura2/AM. Additionally, the occurrence of the
typical Ca2+ spikes further increased to 47.2% and 60.7% when the Ca2+ concentration in the bathing medium was decreased from 1.8 mM to 1.5 mM and the medium temperature was set to 35 ± 1°C from
22 ± 2°C. Therefore, this study provides a useful approach for measuring [Ca2+]i oscillatory response to relevant physiological stimulation in a wild type cell line through the adjustments of the concentrations
adopted for the Ca2+ indicator and extracellular medium Ca2+ and of the temperature set for the experiment. 相似文献
7.
Sulfhydryl-reactive heavy metals increase cell membrane K+ and Ca2+ transport in renal proximal tubule 总被引:1,自引:0,他引:1
Summary The cellular mechanisms by which nephrotoxic heavy metals injure the proximal tubule are incompletely defined. We used extracellular electrodes to measure the early effects of heavy metals and other sulfhydryl reagents on net K+ and Ca2+ transport and respiration (QO2) of proximal tubule suspensions. Hg2+, Cu2+, and Au3+ (10–4
m) each caused a rapid net K+ efflux and a delayed inhibition of QO2. The Hg2+-induced net K+ release represented passive K+ transport and was not inhibited by barium, tetraethylammonium, or furosemide. Both Hg2+ and Ag+ promoted a net Ca2+ uptake that was nearly coincident with the onset of the net K+ efflux. A delayed inhibition of ouabainsensitive QO2 and nystatin-stimulated QO2, indicative of Na+, K+-ATPase inhibition, was observed after 30 sec of exposure to Hg2+. More prolonged treatment (2 min) of the tubules with Hg2+ resulted in a 40% reduction in the CCCP-uncoupled QO2, indicating delayed injury to the mitochondria. The net K+ efflux was mimicked by the sulfhydryl reagents pCMBS and N-ethylmaleimide (10–4
m) and prevented by dithiothreitol (DTT) or reduced glutathione (GSH) (10–4
m). In addition, both DTT and GSH immediately reversed the Ag+-induced net Ca2+ uptake. Thus, sulfhydryl-reactive heavy metals cause rapid, dramatic changes in the membrane ionic permeability of the proximal tubule before disrupting Na+, K+-ATPase activity or mitochondrial function. These alterations appear to be the result of an interaction of the metal ions with sulfhydryl groups of cell membrane proteins responsible for the modulation of cation permeability. 相似文献
8.
Cadmium nephrotoxicity in human proximal tubule cell cultures 总被引:2,自引:0,他引:2
Debra J. Hazen-Martin Donald A. Sens John G. Blackburn Mary Ann Sens 《In vitro cellular & developmental biology. Plant》1989,25(9):784-790
Summary Human proximal tubule kidney cells grown in a serum-free tissue culture medium were exposed to concentrations of CdCl2 in a range of 0.5 to 10μg/ml. Cells were observed from 1 to 20 d upon initiation of cadmium in the culture fluid. Both confluent
and subconfluent populations of cells were treated and evaluated for cytotoxicity. Both populations exhibited a concentration-dependent
toxicity to ionic cadmium. For cells treated with 2.0 to 10 μg/ml Cd, the decreases in cell numbers were largely irreversible.
However, cells treated with Cd in a range of 0.5 to 1.0 μg/ml exhibited a partial recovery of cell number and control morphology.
In this range, recovery was more efficient in the subconfluent cultures. Fine structural alterations in Cd-treated tubule
cells included condensation of nuclear chromatin, loss of microvilli structure, disorganization of lateral membrane interdigitation,
as well as decreased uptake of aminoglycoside antibiotics as evidenced by decreased numbers of myeloid bodies in these cells.
The results of this study imply that use of a human proximal tubule culture system has potential in discerning structural
and functional effects of cadmium as well as other nephrotoxic metals and compounds on the human kidney.
This paper was presented at a Symposium on the Physiology and Toxicology of the Kidney In Vitro co-sponsored by The Society
of Toxicology (SOT) and the Tissue Culture Association held at the 27th annual meeting of the SOT in Dallas, Texas in 1988.
This work was supported by the Johns Hopkins Center for Alternatives to Animal Testing. 相似文献
9.
Jeyaraman Vikramathithan Gali Nirmal kumar Pandurangan Muthuraman Kotteazeth Srikumar 《The protein journal》2010,29(7):481-486
A thermo stable xylanase was purified and characterized from the cladodes of Cereus pterogonus plant species. The enzyme was purified to homogeneity by ammonium sulfate (80%) fractionation, ion exchange and size exclusion
chromatography. The enzyme showed a final specific activity of 216.2 U/mg and the molecular mass of the protein was 80 KDa.
The optimum pH and temperature for xylanase activity were 5.0 and 80 °C, respectively,. With oat spelt xylan as a substrate
the enzyme yielded a Km value of 2.24 mg/mL and a Vmax of 5.8 μmol min−1 mg−1. In the presence of metal ions (1 mM) such as Co2+,Mn2+, Ni2+, Ca2+ and Fe3+ the activity of the enzyme increased, where as strong inhibition of the enzyme activity was observed with the use of Hg2+, Cd2+, Cu2+, while partial inhibition was noted with Zn2+ and Mg2+. The substrate specificity of the xylanase yielded maximum activity with oat spelt xylan. 相似文献
10.
The adipokine leptin and oncotic protein albumin are endocytosed in the proximal tubule via the scavenger receptor megalin. Leptin reduces megalin expression and activates cell signalling pathways that upregulate fibrotic protein expression. The aim of this study was to investigate if leptin uptake in proximal tubule cells was via the albumin-megalin endocytic complex. In immortalised proximal tubule Opossum kidney cells (OK) fluorescent leptin and albumin co-localised following 5 min exposure, however there was no co-localisation at 10, 20 and 30 min exposure. In OK cells, acute exposure to leptin for 2 h did not alter NHE3, ClC-5, NHERF1 and NHERF2 mRNA. However, acute leptin exposure increased NHERF2 protein expression in proximal tubule cells. In OK cells, immunoprecipitation experimentation indicated leptin did not bind to ClC-5. Leptin uptake in OK cells was enhanced by bafilomycin and ammonium chloride treatment, demonstrating that uptake was not dependent on lysosomal pH. Thus, it is likely that two pools of megalin exist in proximal tubule cells to facilitate separate uptake of leptin and albumin by endocytosis. 相似文献
11.
Huang HK Tokashiki M Maeno S Onaga S Taira T Ito S 《Journal of industrial microbiology & biotechnology》2012,39(1):55-62
A heat-labile phenolic acid decarboxylase from Candida guilliermondii (an anamorph of Pichia guilliermondii) was purified to homogeneity by simple successive column chromatography within 3 days. The molecular mass was 20 kDa by sodium
dodecyl sulfate–polyacrylamide gel electrophoresis and 36 kDa by gel-filtration chromatography, suggesting that the purified
enzyme is a homodimer. The optimal pH and temperature were approximately 6.0 and 25°C. Characteristically, more than 50% of
the optimal activity was observed at 0°C, suggesting that this enzyme is cold-adapted. The enzyme converted p-coumaric acid, ferulic acid, and caffeic acid to corresponding products with high specific activities of approximately 600,
530, and 46 U/mg, respectively. The activity was stimulated by Mg2+ ions, whereas it was completely inhibited by Fe2+, Ni2+, Cu2+, Hg2+, 4-chloromericuribenzoate, N-bromosuccinimide, and diethyl pyrocarbonate. The enzyme was inducible and expressed inside the cells moderately by ferulic
acid and p-coumaric acid and significantly by non-metabolizable 6-hydroxy-2-naphthoic acid. 相似文献
12.
Andreazza R Okeke BC Pieniz S Brandelli A Lambais MR Camargo FA 《Biological trace element research》2011,143(2):1182-1192
Environmental copper contamination is a serious human health problem. Copper reductase is produced by microorganisms to facilitate
copper uptake by ATPases into the cells increasing copper biosorption. This study assessed the reduction of Cu(II) by cell-free
extracts of a highly copper-resistant bacterium, Pseudomonas sp. strain NA, isolated from vineyard soil contaminated with copper. Both intact cells and cell-free extract of Pseudomonas sp. strain NA displayed substantial reduction of Cu(II). Intact cells reduced more then 80 mg L−1 of Cu(II) from medium amended with 200 mg L−1 of copper after 24 h of incubation. Cell-free extract of the isolate reduced more than 65% of the Cu(II) at initial copper
concentration of 200 mg L−1 after 24 h. Soluble protein production was high at 72 h of incubation at 100 mg L−1 of copper, with more then 60 μg L−1 of total soluble protein in cell-free extract recorded. Cu(II) reduction by isolate NA was increased when copper concentration
increased for both intact cells and cell-free extract. Results indicate that Pseudomonas sp. strain NA produces copper reductase enzyme as the key mechanism of copper biotransformation. 相似文献
13.
Isabelle Genestie Jean-Paul Morin Christophe Guery Gerd Bode Giocondo Lorenzon 《In vitro cellular & developmental biology. Animal》1997,33(9):692-702
Summary The aim of this study was to better characterize rabbit proximal kidney tubule cells cultured on collagen IV-coated porous
inserts, as compared to the same cells seeded in standard plastic wells. Total protein contents in confluent monolayers on
permeable membranes were about twofold higher than those measured in confluent cultures in plastic wells. Microscopy examinations
suggested that such a difference was probably due to a higher cell density and to an impressive development of the apical
brush-border membrane. Moreover, measurement of unidirectional transport of p-aminohippuric acid and tetraethylammonium bromide confirmed the high polarization level of cultures on porous inserts. Results
of methyl(α-d-[U-14C]glyco)pyranoside uptake suggested that cell phenotype was probably influenced by culture conditions. Analysis of different
markers as a function of time in culture showed decreases of alkaline phosphatase (AP), γ-glutamyltranspeptidase (GGT), and
Na+-K+-ATPase activities as well as increases in LDH, ATP, and glutathione levels, similar to those formerly reported for cells
cultured in standard plastic plates. However, comparative data from 6-d-old monolayers have shown that AP, GGT, Na+-K+-ATPase, glutathione reductase (GRED), and selenium-dependent glutathione peroxidase (Se-GPX) activities were 2.8-, 2.6-,
1.6-, 1.2-, and 2.1-fold, respectively, better preserved on precoated permeable membranes. On the other hand, this paper reports
for the first time in the literature that GRED and Se-GPX, two phase II detoxification enzymes, were well maintained in cultures
of rabbit proximal kidney tubule cells. Our results show that culturing rabbit proximal kidney tubule cells on collagen IV-coated
porous membranes was accompanied by an improvement of both morphological and biochemical properties of the cells. 相似文献
14.
The role of H+-ATPase in proximal tubule cell pH regulation was studied by microperfusion techniques and by confocal microscopy. In a first
series of experiments, proximal S3 segments of rabbit kidney were perfused ``in vitro' while their cell pH was measured by
fluorescence microscopy after loading with BCECF. In Na+- and Cl−-free medium, cell pH fell by a mean of 0.37 ± 0.051 pH units, but after a few minutes started to rise again slowly. This
rise was of 0.17 ± 0.022 pH units per min, and was significantly reduced by bafilomycin and by the Cl− channel blocker NPPB, but not by DIDS. In a second series of experiments, subcellular vesicles of proximal tubule cells of
S3 segments of mouse kidney were studied by confocal microscopy after visualization by acridine orange or by Lucifer yellow.
After superfusion with low Na+ solution, which is expected to cause cell acidification, vesicles originally disposed in the basolateral and perinuclear
cell areas, moved toward the apical area, as detected by changes in fluorescence density measured by the NIH Image program.
The variation of apical to basolateral fluorescence ratios during superfusion with NaCl Ringer with time was 0.0018 ± 0.0021
min−1, not significantly different from zero (P > 0.42). For superfusion with Na+0 Ringer, this variation was 0.081 ± 0.015 min−1, P < 0.001 against 0. These slopes were markedly reduced by the Cl− channel blocker NPPB, and by vanadate at a concentration that has been shown to disrupt cytoskeleton function. These data
show that the delayed alkalinization of proximal tubule cells in Na+-free medium is probably due to a vacuolar H+-ATPase, whose activity is stimulated in the presence of Cl−, and dependent on apical insertion of subcellular vesicles. The movement of these vesicles is also dependent on Cl− and on the integrity of the cytoskeleton.
Received: 11 April 2000/Revised: 14 August 2000 相似文献
15.
Deniz Özkan Deniz Yüzbaşıoğlu Fatma Ünal Serkan Yılmaz Hüseyin Aksoy 《Cytotechnology》2009,59(2):73-80
The organophosphorous insecticide acephate was tested for its ability to induce in vitro cytogenetic effect in human peripheral
lymphocytes by using the chromosomal aberrations (CAs), sister chromatid exchange (SCE) and micronuclei (MN) assay. The level
of nuclear DNA damage of acephate was evaluated by using the comet assay. Concentrations of 12.5, 25, 50, 100 and 200 μg mL−1 of acephate were used. All concentrations of acephate induced significant increase in the frequency of CAs and in the formation
of MN dose dependently (r = 0.92 at 24 h, r = 0.95 at 48 h for CAs, r = 0.87 for MN). A significant increase was observed in induction of SCE at 50, 100 and 200 μg mL−1 concentrations during 24 h treatment and at all concentrations (except 12.5 μg mL−1) during 48 h treatment period in a dose-dependent manner (r = 0.84 at 24 h, r = 0.88 at 48 h). Acephate did not affect the replicative index and cytokinesis-block proliferation index (CBPI). However,
it significantly decreased the mitotic index at all three highest concentrations (50, 100, 200 μg mL−1) for 24 h treatment and at all concentrations (except 12.5 μg mL−1) for 48 h treatment, dose-dependently (r = 0.94 at 24 h, r = 0.92 at 48 h). A significant increase in mean comet tail length was observed at 100 and 200 μg mL−1 concentrations compared with negative control in a concentration-dependent manner (r = 0.94). The mean comet tail intensity was significantly increased at only 200 μg mL−1 concentration. The present results indicate that acephate is a clastogenic, cytotoxic agent and it causes DNA damage at high
concentrations in human lymphocytes in culture. 相似文献
16.
Wenhui Wang Yang Wang Stefan Silbernagl Hans Oberleithner 《The Journal of membrane biology》1988,101(1):259-265
Summary Experiments were performed in intact proximal tubules of the doubly perfused kidney and in fused proximal tubule cells ofRaha esculenta to evaluate the dependence of intracellular pH (pHi) on cell membrane potential applying pH-sensitive and conventional microelectrodes. In proximal tubules an increase of the K– concentration in the peritubular perfusate from 3 to 15 mmol/liter decreased the peritubular cell membrane potential from –55±2 to –38±1 mV paralleled by an increase of pH
i
, from 7.54±0.02 to 7.66±0.02. The stilbene derivative DIDS hyperpolarized the cell membrane potential from –57 ± 2 to –71 ±4 mV and led to a significant increase of the K–-induced cell membrane depolarization, but prevented the K–-induced intracellular alkalinization. Fused proximal tubule cells were impaled by three microelectrodes simultaneously and cell voltage was clamped stepwise while pH
i
changes were monitored. Cell membrane hyperpolarization acidified the cell cytoplasm in a linear relationship. This voltage-induced intracellular acidification was reduced to about one-third when HCO3 ions were omitted from the extracellular medium. We conclude that in proximal tubule cells pH
i
depends on cell voltage due to the rheogenicity of the HCO
3
–
transport system. 相似文献
17.
Ana Flávia Azevedo Carvalho Maurício Boscolo Roberto da Silva Henrique Ferreira Eleni Gomes 《Journal of microbiology (Seoul, Korea)》2010,48(4):452-459
An α-glucosidase enzyme produced by the fungus Thermoascus aurantiacus CBMAI 756 was purified by ultra filtration, ammonium sulphate precipitation, and chromatography using Q Sepharose, Sephacryl
S-200, and Superose 12 columns. The apparent molecular mass of the enzyme was 83 kDa as determined in gel electrophoresis.
Maximum activity was observed at pH 4.5 at 70°C. Enzyme showed stability stable in the pH range of 3.0–9.0 and lost 40% of
its initial activity at the temperatures of 40, 50, and 60°C. In the presence of ions Na+, Ba2+, Co2+, Ni2+, Mg2+, Mn2+, Al3+, Zn2+, Ca2+ this enzyme maintained 90–105% of its maximum activity and was inhibited by Cr3+, Ag+, and Hg2+. The enzyme showed a transglycosylation property, by the release of oligosaccharides after 3 h of incubation with maltose,
and specificity for short maltooligosaccharides and α-PNPG. The Km measured for the α-glucosidase was 0.07 μM, with a Vmax of 318.0 μmol/min/mg. 相似文献
18.
Han Gil Choi Ki Hoon Lee Hyun Il Yoo Pil Jun Kang Young Sik Kim Ki Wan Nam 《Journal of applied phycology》2008,20(5):729-735
The effects of temperature, irradiance, and daylength on Sargassum horneri growth were examined at the germling and adult stages to discern their physiological differences. Temperature–irradiance
(10, 15, 20, 25, 30°C × 20, 40, 80 μmol photons m−2s−1) and daylength (8, 12, 16, 24 h) experiments were carried out. The germlings and blades of S. horneri grew over a wide range of temperatures (10–25°C), irradiances (20–80 μmol photons m−2s−1), and daylengths (8–24 h). At the optimal growth conditions, the relative growth rates (RGR) of the germlings were 21% day−1 (25°C, 20 μmol photons m−2s−1) and 13% day−1 (8 h daylength). In contrast, the RGRs of the blade weights were 4% day−1 (15°C, 20 μmol photons m−2s−1) and 5% day−1 (12 h daylength). Negative growth rates were found at 20 μmol photons m−2s−1 of 20°C and 25°C treatments after 12 days. This phenomenon coincides with the necrosis of S. horneri blades in field populations. In conclusion, we found physiological differences between S. horneri germlings and adults with respect to daylength and temperature optima. The growth of S. horneri germlings could be enhanced at 25°C, 20 μmol photons m−2s−1, and 8 h daylength for construction of Sargassum beds and restoration of barren areas. 相似文献
19.
Chen SP Wu JL Su YC Hong JR 《Apoptosis : an international journal on programmed cell death》2007,12(6):1043-1060
Nervous necrosis virus (NNV)-induced, host cell apoptosis mediates secondary necrosis by an ill-understood process. In this
study, redspotted grouper nervous necrosis virus (RGNNV) is shown to induce mitochondria-mediated necrotic cell death in GL-av
cells (fish cells) via cytochrome c release, and anti-apoptotic proteins are shown to protect these cells from death. Western blots revealed that cytochrome
c release coincided with disruption of mitochondrial ultrastructure and preceded necrosis, but did not correlate with caspases
activation. To identify the mediator(s) of this necrotic process, a protein synthesis inhibitor (cycloheximide; CHX; 0.33 μg/ml)
was used to block cytochrome c release as well as PS exposure and mitochondrial membrane permeability transition pore (MMP) loss. CHX (0.33 μg/ml) completely
blocked viral protein B2 expression, and partly blocked protein A, protein α, and a pro-apoptotic death protein (Bad) expression.
Overexpression of B2 gene increased necrotic-like cell death up to 30% at 48 h post-transfection, suggesting that newly synthesized protein (B2)
may be involved in this necrotic process. Finally, necrotic death was prevented by overexpression of Bcl-2 family proteins,
zfBcl-xL and xfMcl-1a. Thus, new protein synthesis and release of cytochrome c are required for RGNNV-induced necrotic cell death, which can be blocked by anti-apoptotic Bcl-2 members.
J.-L. Wu and J.-R. Hong contributed equally to the research. 相似文献
20.
T. Nørgaard 《Histochemistry and cell biology》1979,63(1):103-113
Summary A quantitative fluorimetric method is described for estimating the activity of glucose-6-phosphate dehydrogenase in isolated fractions of rabbit nephron from the superficial part of the renal cortex: macula densa, proximal convoluted tubule, distal convoluted tubule and glomerulus. The mean activity in the macula densa region was 2.5×10–18 mol/m3/min, which was about twice the mean activity of the proximal and distal tubular cells and four times that of the glomeruli. As glucose-6-phosphate dehydrogenase is located in the cytoplasm, the average cytoplasmic enzyme activity of the different tubular cells was calculated: macula densa activity was 4.0×10–18 mol/m3/min whilst proximal tubular cells showed about a third, and distal tubular cells about a quarter of this activity. 相似文献