共查询到20条相似文献,搜索用时 31 毫秒
1.
We have fused the epidermal growth factor (EGF) to the amino terminus of Pseudomonas exotoxin A (PE) to create a cytotoxic agent, designated EGF-PE, which preferentially kills EGF-receptor-bearing cells. In
this study, we analyzed the effect of the Ia domain, the binding domain, of PE on the cytotoxicity of EGF-PE towards EGF-receptor-bearing
cells and tried to develop a more potent EGF-receptor-targeting toxin. EGF-PE molecules with sequential deletions at the amino
terminus of PE were constructed and expressed in E. coli strain BL21(DE3). The cytotoxicity of these chimeric toxins was then examined. Our results show that the amino-terminal and
carboxy-terminal regions of the Ia domain of PE are important for the cytotoxicity of a PE-based targeting toxin. To design
a more potent PE-based EGF-receptor-targeting toxin, a chimeric toxin, named EGF-PE(Δ34–220), which had most of the Ia domain
deleted but retained amino acid residues 1–33 and 221–252 of this domain, was constructed. EGF-PE(Δ34–220) has EGF-receptor-binding
activity but does not show PE-receptor-binding activity and is mildly cytotoxic to EGF-receptor-deficient NR6 cells. As expected,
EGF-PE(Δ34–220) is a more potent cytotoxic agent towards EGF-receptor-bearing cells than EGF-PE(Δ1–252), where the entire
Ia domain of PE was deleted. In addition, EGF-PE(Δ34–220) was shown to be extremely cytotoxic to EGF-receptor-bearing cancer
cells, such as A431, CE81T/VGH, and KB-3-1 cells. We also found that EGF-PE(Δ34–220) was highly expressed in BL21(DE3) and
could be easily purified by urea extraction. Thus, EGF-PE(Δ34–220) can be a useful cytotoxic agent towards EGF-receptor-bearing
cells.
Received : 20 May 1994 / Received last revision : 9 September 1994 / Accepted : 28 September 1994 相似文献
2.
Wang H Van Blitterswijk CA Bertrand-De Haas M Schuurman AH Lamme EN 《In vitro cellular & developmental biology. Animal》2004,40(8-9):268-277
Summary The number of medical applications using autologous fibroblasts is increasing rapidly. We investigated thoroughly the procedure
to isolate cells from skin using the enzymatic tissue dissociation procedure. Tissue digestion efficiency, cell viability,
and yield were investigated in relation to size of tissue fragments, digestion volume to tissue ratio, digestion time, and
importance of other protease activities present in Clostridium histolyticum collagenase (CHC) (neutral protease, clostripain, and trypsin). The results showed that digestion was optimal with small
tissue fragments (2–3 mm3) and with volumes tissue ratios ≥2 ml/g tissue. For incubations ≤10 h, the digestion efficiency and cell isolation yields
were significantly improved by increasing the collagenase, neutral protease, or clostripain activity, whereas trypsin activity
had no effects. However, a too high proteolytic activity of one of the proteases present in CHC digestion solution or long
exposure times interfered with cell viability and cell culture yields. The optimal range of CHC proteases activities per milliliter
digestion solutions was determined for digestions ≤10 h (collagenase 2700–3900 Mandl U/ml, neutral protease 5100–10,000 caseinase
U/ml, and clostripain 35–48 BAEE U/ml) and for longer digestions (>14 h) (collagenase 1350–3000 U/ml, neutral protease 2550–7700
U/ml, and clostripain 18–36 U/ml). Using these conditions, a maximum fibroblast expansion was achieved when isolated cells
were seeded at 1×104 cells/cm2. These results did not only allow selection of optimal CHC batches able to digest dermal tissue with an high cell viability
but also significantly increased the fibroblast yields, enabling us to produce autologous dermal tissue in a clinically acceptable
time frame of 3 wk. 相似文献
3.
Localization and Identification of Populations of Phosphatase-Active Bacterial Cells Associated with Activated Sludge Flocs 总被引:4,自引:0,他引:4
Abstract
The majority of phosphatase (PO4ase) activity detected in fresh aerobic activated sludge from a municipal wastewater treatment plant was associated with suspended
floc material. PO4ase activity appeared to be localized in discrete bacteria-containing areas of the floc matrix based on the distribution of
nucleic acid–stained cells and precipitated fluorescent crystals produced as a result of reaction of the enzyme(s) with the
artificial substrate ELF™-PO4. Of the total floc-associated bacterial cells that stained positive with the nucleic acid–binding fluorochrome acridine orange
(AO), 8.8 ± 1.2% displayed PO4ase activity based on the proximity of AO-stained cells to precipitated ELF crystals. Using a 16S rRNA oligonucleotide probe
specific for the cytophaga–flavobacteria group, it was determined that 17–20% of the floc-associated bacteria that probed
positive also displayed PO4ase activity. Furthermore, 35–45% of the ELF fluorescence was associated with bacterial cells that probed positive for the
cytophaga–flavobacteria group. The results suggest that the cytophaga–flavobacteria, as a group, is important in mediating
the liberation of inorganic orthophosphate (Pi) from phosphomonoesters of detrital organic phosphate (organic-P) in the aerobic activated sludge process of wastewater treatment.
Received: 17 March 1999; Accepted: 9 June 1999 相似文献
4.
The effect of cisplatin on five glutathione-related enzymes was studied in liver, kidney, and Dalton lymphoma cells of tumor-bearing
mice. In liver, the activities of glutathione S-transferase, glutathione peroxidase, catalase, and superoxide dismutase decreased approximately 30–40%, 60–67%, 35–50% and
70–80% respectively, while glutathione reductase increased about 36–45% after cisplatin treatment. In kidney, catalase activity
decreased by 47–82% at all time points (24–96 h) of cisplatin treatment, while glutathione S-transferase activity decreased significantly (~24%) mainly at 72 h of treatment. An increase in glutathione reductase (~1.5–2.5
times), glutathione peroxidase (significant at 24 h, 47%), and superoxide dismutase (~15–60%) was noted in kidney after the
treatment. In Dalton lymphoma cells, the activities of glutathione S-transferase, glutathione peroxidase, and catalase decreased very distinctly (~2–5, 2–5 and 5–11 times, respectively) at all
time points, but glutathione reductase decreased significantly only at 72 h of cisplatin treatment. Interestingly, the superoxide
dismutase activity in Dalton lymphoma cells increased initially at 24–48 h and then decreased (~60%) during later periods
(72–96 h) of treatment. Cisplatin treatment caused a decrease in glutathione level in Dalton lymphoma cells (~14–20%) and
kidney (~18–28%) but no change in liver. In view of the results, a definite correlation with the changes in glutathione concentrations
and enzymatic activities in a tissue could not be firmly derived. It is suggested that the changes in various glutathione-related
enzymes and glutathione levels in the tissues of the host during cisplatin-mediated chemotherapy could affect cellular antioxidant
defense potential, which may play an important contributory role in cisplatin-mediated toxicity, particularly nephrotoxicity,
and anticancer activity in the host.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
G. A. Hitman G. C. Toms B. J. Boucher L. Garde P. Baker J. Awad H. Festenstein 《Immunogenetics》1989,30(6):427-431
Cytokines and their related enzyme pathways may play a part in the development of insulin-dependent diabetes mellitus (IDDM).
We have therefore studied the activity of the enzyme 2′–5′ oligoadenylate synthetase (which is induced by both interferon
and the tumour necrosis factors) in circulating mononuclear cells from 40 subjects with IDDM and 32 healthy control subjects.
There was no difference in mean basal enzyme activity between the two groups. A polymorphism of the 2′–5′ oligoadenylate synthetase
gene, not previously described, was found using the restriction enzymeBam HI. There was no association of 2′–5′ oligoadenylate synthetase genotypes with IDDM, but there was a significant correlation
between basal 2′–5′ oligoadenylate synthetase activity and 2′–5′ oligoadenylate synthetase genotypes. Significantly higher
mean basal levels of 2′–5′ oligoadenylate synthetase activity were associated with HLA-DQA 4.6 phenotype (determined using
the restriction enzymeTaq 1 and a DQA probe) and HLA-DR3 (determined serologically), whereas significantly lower mean levels of enzyme activity were
associated with HLA-DQA 5.5 and HLA-DR7, in both IDDM and control subjects. An analysis of variance confirmed that these associations
were independent 2′–5′ oligoadenylate synthetase genotype. Likewise, a significantly higher mean level of enzyme activity
was associated with the heterozygous 1/3 insulin-related genotype in the IDDM subjects only. This study therefore suggests
that the possession of certainHLA haplotypes might be associated with differing levels of basal 2′–5′ oligoadenylate synthetase activity. 相似文献
6.
D. Ferbus U. Testa M. Titeux F. Louache M. N. Thang 《Molecular and cellular biochemistry》1985,67(2):125-133
Summary Variations in the (2′–5′) oligoadenylate synthetase (2–5 A synthetase) level were examined prior to and during the differentiation
in culture of the human monocyte cell line U937 and the promyelocytic cell line HL60 in an attempt to reveal whether the enzyme
is actively involved in hematopoietic cell maturation. The basal level of this enzyme was much higher in U937 than in HL60
cells. The activity of 2–5 A synthetase was enhanced in both cell lines in response to α, β interferons.
During cell differentiation, ten markers were measured. The level of the enzyme rose during the process of cellular maturation
in both cell lines. The 2–5 A synthetase activity observed in differentiated HL60 and U937 cells was comparable to that observed
in mature normal granulocytes and monocytes respectively. Induction of U937 differentiation by chemicals was associated with
detectable production of IFN. The increase in enzyme activity observed was mostly dependent on endogenous production of interferon,
since it was inhibited by interferon antibodies. Kinetic studies showed that in U937 cells 2–5 A synthetase was expressed
prior to several of the differentiation markers. The rise in the enzyme's level observed during the differentiation of HL60
cells was independent of endogenous production of interferon, since it was not inhibited by the addition of anti-interferon
antibodies.
These results suggest that different biochemical and molecular mechanisms are responsible for the induction of 2–5 A synthetase
observed during the differentiation of hematopoietic cells. In any case, 2–5 A synthetase can be considered as a biochemical
marker of cell status and differentiation in hematopoietic cells. 相似文献
7.
8.
During tumor growth and invasion, the endothelial cells from a relatively quiescent endothelium start proliferating. The exact
mechanism of switching to a new angiogenic phenotype is currently unknown. We have examined the role of intracellular cAMP
in this process. When a non-transformed capillary endothelial cell line was treated with 2 mM 8Br-cAMP, cell proliferation
was enhanced by ∼70%. Cellular morphology indicated enhanced mitosis after 32–40 h with almost one-half of the cell population
in the S phase. Bcl-2 expression and caspase-3, -8, and -9 activity remained unaffected. A significant increase in the Glc3Man9GlcNAc2-PP-Dol biosynthesis and turnover, Factor VIIIC N-glycosylation, and cell surface expression of N-glycans was observed in cells treated with 8Br-cAMP. Dol-P-Man synthase activity in the endoplasmic reticulum membranes also
increased. A 1.4–1.6-fold increase in HSP-70 and HSP-90 expression was also observed in 8Br-cAMP treated cells. On the other
hand, the expression of GRP-78/Bip was 2.3-fold higher compared to that of GRP-94 in control cells, but after 8Br-cAMP treatment
for 32 h, it was reduced by 3-fold. GRP-78/Bip expression in untreated cells was 1.2–1.5-fold higher when compared with HSP-70
and HSP-90, whereas that of the GRP-94 was 1.5–1.8-fold lower. After 8Br-cAMP treatment, GRP-78/Bip expression was reduced
4.5–4.8-fold, but the GRP-94 was reduced by 1.5–1.6-fold only. Upon comparison, a 2.9-fold down-regulation of GRP-78/Bip was
observed compared to GRP-94. We, therefore, conclude that a high level of Glc3Man9GlcNAc2-PP-Dol, resulting from 8Br-cAMP stimulation up-regulated HSP-70 expression and down-regulated that of the GRP-78/Bip, maintained
adequate protein folding, and reduced endoplasmic reticulum stress. As a result capillary endothelial cell proliferation was
induced. 相似文献
9.
Background
Tat is being tested as a component of HIV vaccines. Tat activity has been mainly investigated on cells of lymphoid/hematopoietic lineages. HIV-1, however, is known to infect many different cells of both solid organs and mucosal surfaces. The activity of two-exon (aa 1–101) and synthetic (aa 1–86) Tat was studied on mammary and amniotic epithelial cells cultured under low serum conditions. 相似文献10.
He Meng Ji-Yao Chen Lan Mi Pei-Nan Wang Mei-Ying Ge Yang Yue Ning Dai 《Journal of biological inorganic chemistry》2011,16(1):117-123
Bovine serum albumin (BSA)-coated CdTe/ZnS quantum dots (BSA–QDs) were selected to conjugate with folic acid (FA), forming
FA–BSA–QDs. This study aims to develop these small FA–BSA–QDs (less than 10 nm) for the diagnosis of cancers in which the
FA receptor (FR) is overexpressed. The enhancement of cellular uptake in FR-positive human nasopharyngeal carcinoma cells
(KB cells) for FA–BSA–QDs was found by means of confocal fluorescence microscopy under single-photon and two-photon excitation.
The uptake enhancement for FA–BSA–QDs was further evaluated by flow-cytometric analysis in 104 KB cells, and was about 3 times higher than for BSA–QDs on average. The uptake enhancement was suppressed when KB cells had
been pretreated with excess FA, reflecting that the enhancement was mediated by the association of FR at cell membranes with
FA–BSA–QDs. When human embryonic kidney cells (293T) (FR-negative cells) and KB cells, respectively, were incubated with FA–BSA–QDs
(1 μM) for 40 min, the FA–BSA–QD uptake by 293T cells was much weaker than that by KB cells, demonstrating that FA–BSA–QDs
could undergo preferential binding on FR-positive cancer cells. These characteristics suggest that FA–BSA–QDs are potential
candidates for cancer diagnosis. 相似文献
11.
Erk is involved in the differentiation induced by diallyl disulfide in the human gastric cancer cell line MGC803 总被引:3,自引:0,他引:3
Ling H Zhang LY Su Q Song Y Luo ZY Zhou XT Zeng X He J Tan H Yuan JP 《Cellular & molecular biology letters》2006,11(3):408-423
Diallyl disulfide (DADS) is a major constituent of garlic. Previously, we found that DADS both inhibited proliferation in
human gastric cancer cells in vitro and in vivo, and induced G2/M arrest. In this study, we investigated whether this differentiation effect was induced by DADS in human
gastric cancer MGC803 cells, and whether it was related to an alteration in ERK activity. The results showed that the growth
of MGC803 cells was inhibited by DADS. Cells treated with DADS displayed a lower nucleocytoplasmic ratio and tended to form
gland and intercellular conjunction structures. The ConA-mediated cell agglutination ratio and cells’ ALP specific activity
decreased. In MGC803 cells, dye transfer was limited to a few cells neighbouring the dye-injected cell and to a depth of 1–2
layers beneath the scrape site. However, after treatment with DADS, the LY (Lucifer Yellow) was transferred to several cells
immediately neighbouring the microinjected cell and to a depth of 2–4 cell layers from the scrape site. This indicated that
DADS induced differentiation in MGC803 cells. Western blot analysis revealed that although DADS did not influence the quantity
of ERK1/2 protein expressed, it did decrease its phosphorylation in a concentration-dependent manner, compared with the controls.
At 30 mg·L−1, DADS inhibited the activation of ERK1/2 in 15–30 min. These results suggested that the DADS-induced differentiation of MGC803
cells involved an alteration of the ERK1/2 signaling pathway. 相似文献
12.
G.-J. Shen B. A. Annous R. W. Lovitt M. K. Jain J. G. Zeikus 《Applied microbiology and biotechnology》1996,45(3):355-362
Butyribacterium methylotrophicum produced more butyrate when grown on lactate than when grown on glucose, and only acetate was detected during growth on pyruvate.
Higher levels of NADH were found in butyrate-producing than in acetate-producing cells. The addition of neutral red, an electron-flow
modulator, to cells growing on pyruvate altered the carbon and electron flow from acetate plus H2 synthesis to butyrate synthesis. Enzymatic analysis suggested that pyruvate was produced from glucose via an Embden-Meyerhof-Parnas
pathway. Pyruvate was further metabolized to butyryl-CoA via, β-hydroxybutyryl-CoA and butyryl-CoA dehydrogenases. Lactate
dehydrogenase, unlike butyryl-CoA dehydrogenase, was inducible and detected only in lactate-grown cells. Both of these dehydrogenases
utilized 2,6-dichloroindophenol and other artificial electron acceptors but not NAD(P). Ferredoxin–NAD oxidoreductase levels
were highest in lactate and lowest in pyruvate-grown cells. Cells contained both a ferredoxin–neutral-red reductase activity
and a neutral-red–NAD reductase activity that coupled electron flow to butyrate synthesis. These results showed that butyrate
synthesis by B. methylotrophicum was regulated by the carbon source and was dependent on the cellular NADH/NAD ratios, and the levels and direction of ferredoxin-
and NAD-linked oxidoreductases.
Received: 3 August 1995/Received revision: 31 October 1995/Accepted: 10 November 1995 相似文献
13.
Ram Sarup Singh Ranjeeta Bhari Jatinder Singh Ashok Kumar Tiwary 《World journal of microbiology & biotechnology》2011,27(3):547-554
Mucin-specific lectin from mycelium of Aspergillus nidulans was purified using anion exchange and gel filtration chromatographic techniques with an overall recovery of 32% and 21.97-fold
purification. The purified lectin migrated as a single band in SDS–PAGE with an apparent molecular mass of 34 kDa. Carbohydrate
analysis revealed that it is a glycoprotein with total sugar content of 2.54%. Optimal agglutination was observed when serially
diluted lectin was incubated with human type O erythrocyte suspension at pH 7.0–8.0 and temperature 20–30°C. Lectin was found
to be completely stable within pH 5.0–8.0 and temperature at or below 40°C. Demetallization by extensive dialysis against
EDTA did not alter its haemagglutination activity. Lectin activity was reduced to half after 24 h incubation with urea and
thiourea, with no such effect of guanidine HCl. The lectin showed potent mitogenic response towards mouse splenocytes, attaining
a maximum at 200 μg/ml as compared to untreated control cells. Mitogenic lectins are invaluable tools to assess the functioning
of immune cells. None of the microfungal lectin has yet been investigated for mitogenic activity. This is the first report
on mitogenic activity of lectin from Aspergillus sp. 相似文献
14.
Theodosia Kazazoglou Eleni Fleischer-Lambropoulos Taxiarchis Geladopoulos Susan Kentroti Costas Stefanis Antonia Vernadakis 《Neurochemical research》1996,21(5):609-614
In this study, we were interested to compare the responsiveness to growth factors, NGF, b-FGF and EGF and cytokines, IL1β,
and TNF-α, in late passages (74–79) C6 glial cells committed astrocytes and astrocytes of advanced passages (26–28) in cultures
derived from aged mouse cerebral hemispheres (MACH). Cultures were grown in either DMEM or chemically defined medium (CDM/TIPS)
in order to test the effects of growth factors or cytokines. The activity of glutamine synthetase (GS), a marker for astrocytes,
was used as a test parameter. We found that treatment with growth factors increased GS activity in both glial cell culture
systems with the exception of EGF in C-6 glial cells. Treatment with cytokines markedly decreased GS activity in the late
passage C6 glial cells whereas only TNF-α had a similar effect on MACH astrocytes. In view of the generally opposite effects
of growth factors and cytokines on GS activity, we-speculate that these molecules which are also endogenously present in glial
cells may play a role in the maintenance of cellular homeostasis. 相似文献
15.
C. A. Savary Monica L. Grazziutti Bohuslav Melichar Donna Przepiorka Ralph S. Freedman Richard E. Cowart D. M. Cohen E. J. Anaissie Darren G. Woodside Bradley W. McIntyre Duane L. Pierson Neal R. Pellis John H. Rex 《Cancer immunology, immunotherapy : CII》1997,45(5):234-240
We studied the potential of multidimensional flow cytometry to evaluate the frequency and maturation/activation status of
dendritic cells in minimally manipulated peripheral blood mononuclear cell preparations (i.e., only separated on Ficoll-Hypaque)
of normal donors and cancer patients. A rare subset of HLA-DR+ leukocytes (less than 1% mononuclear cells) was detected in blood of normal donors that displayed all the features of dendritic
cells: these cells had high forward-light-scatter characteristics and coexpressed CD4, CD86 and CD54 surface antigens, but
lacked the lineage-associated surface markers of T cells, B cells, monocytes, granulocytes or NK i.e. they were CD3–, CD19–, CD20–, CD14–, CD11b–, CD16–, CD56–). These physical and phenotypic properties were virtually identical to those of immunomagnetically sorted leukocytes characterized
as dendritic-cells on the basis of morphology, phenotype and high stimulatory activity in allogeneic mixed-lymphocyte cultures.
Using this flow-cytometric approach we observed that the frequency of dendritic cell-like cells in peripheral blood mononuclear
cell specimens of cancer patients receiving chemotherapy alone or those recovering from stem cell transplantation was significantly
lower than that of normal individuals (mean ± SE: 0.36 ± 0.05%, 0.14 ± 0.06%, and 0.75 ± 0.04% respectively). Multidimensional
flow-cytometric analysis of dendritic cells might represent an important new tool for assessing immunocompetence, and for
monitoring the effects of therapeutic regimens on the immune system.
Received: 20 June 1997 / Accepted: 14 August 1997 相似文献
16.
The coloration of cells of the cyanobacterium Synechococcus sp. PCC 7002 changed from normal blue-green to yellow-green when cells were grown at 15° C in a medium containing nitrate
as the sole nitrogen source. This change of coloration was similar to a general response to nutrient deprivation (chlorosis).
For the chlorotic cells at 15° C, the total amounts of phycobiliproteins and chlorophyll a decreased, high levels of glycogen accumulated, and growth was arithmetic rather than exponential. These changes in composition
and growth occurred in cells grown at low (50 μE m–2 s–1) as well as high (250 μE m–2 s–1) light intensity. After a temperature shift-up to 38° C, chlorotic cells rapidly regained their normal blue-green coloration
and normal exponential growth rate within 7 h. When cells were grown at 15° C in a medium containing urea as the reduced nitrogen
source, cells grew exponentially and the symptoms of chlorosis were not observed. The decrease in photosynthetic oxygen evolution
activity at low temperature was much smaller than the decrease in growth rate for cells grown on nitrate as the nitrogen source.
These studies demonstrate that low-temperature-induced chlorosis of Synechococcus sp. PCC 7002 is caused by nitrogen limitation and is not the result of limited photosynthetic activity or photodamage to
the photosynthetic apparatus, and that nitrogen assimilation is an important aspect of the low-temperature physiology of cyanobacteria.
Received: 24 April 1997 / Accepted: 5 August 1997 相似文献
17.
Carina Nielsen Maximilian Casteel Andrea Didier Richard Dietrich Erwin Märtlbauer 《Mycotoxin Research》2009,25(2):77-84
Trichothecene cytotoxicity of type A (T-2 toxin and HT-2 toxin), type B (deoxynivalenol, DON, and nivalenol, NIV), and type
D (satratoxins G and H) compounds was determined comparatively by using eight permanent human cell lines (Hep-G2, A549, CaCo-2,
HEp-2, A204, U937, RPMI 8226, and Jurkat). Viability of cells was measured by a water-soluble tetrazolium (WST-1) reagent
cell proliferation assay assessing mitochondrial metabolic activity. Toxicity was expressed as the toxin concentration inhibiting
50% of cell viability (IC50). Depending on the chemotype of the tested trichothecenes, relative cytotoxic activity differed by a factor of 100–1,000,
and the corresponding IC50 values were in the range from 2.2 nmol/l (satratoxin H on Jurkat and U937 cells) to 4,900 nmol/l (deoxynivalenol on HEp-2
cells). In contrast, the specific toxicity of each individual mycotoxin towards different cell lines was within remarkable
close limits, and between-cell line differences were much smaller than previously reported. For the cell lines tested, IC50 values were 4.4–10.8 nmol/l for T-2 toxin, 7.5–55.8 mol/l for HT-2 toxin, 600–4,900 nmol/l for DON, 300–2,600 nmol/l for
NIV, and 2.2–18.3 nmol/l for satratoxins G/H. In addition, for the first time, the toxic activity of trichothecenes on primary
cell culture of human endothelial cells (HUVEC) was tested. The susceptibility of this cell line was comparable to the other
cell lines tested, with IC50 values ranging from 16.5 nmol/l (T-2 toxin) to 4,500 nmol/l (DON). The results suggest that the current focus of cytotoxicological
studies on trichothecenes on lymphoid cell lines may lead to an underestimate of their potential on other target cell systems. 相似文献
18.
Harry Walter Eugene J. Krob Rosalinda B. Wenby Herbert J. Meiselman 《Cell biochemistry and biophysics》1990,16(3):139-148
Rats were injected with59Fe-ferrous citrate and bled thereafter at different times (16 h to 49 d). This gave rise to red cell populations in which
cells corresponding in age to the time elapsed between injection and bleeding were labeled. The anticoagulant used was either
acid-citrate-dextrose (ACD) with a pH adjusted to 7.3 or ACD (pH 5.1). Final pH of the collected blood was about 7.2–7.4 in
the former case and 6.4–6.7 in the latter. Red cells were then centrifuged (5) and approximately 7–10% of the packed cells
from the top and 7–10% from the bottom of the cell column collected. When reticulocytes are the predominant labeled red cell
population, as in blood obtained for about 24 h after isotope injection, a fractionation of these cells and mature erythrocytes
is in evidence only when blood is collected at the higher pH. Thus, at pH 7.2–7.4 ratios of specific radioactivities of cells
in top fraction/cells in an unfractionated sample are about 3, whereas at pH 6.4–6.7, the analogous ratios are 1 or less.
These differences in specific activity ratios, as a function of pH at collection, virtually disappear after about 4 d following
isotope injection.
The lower pH is known to increase the volume and decrease the density of mature red blood cells. The marked effect of pH on
cellular fractionation could be correlated with the smaller change in rat reticulocyte density and volume in acid medium.
At pH 6.4–6.7, the densities of mature erythrocytes and reticulocytes are so close that their physical separation by centrifugation
is not feasible. 相似文献
19.
Roles of complex gangliosides in the development of experimental autoimmune encephalomyelitis 总被引:1,自引:0,他引:1
We induced experimental autoimmune encephalomyelitis (EAE) inGM2/GD2 synthase knockout mice (GM2/GD2–/–), whichcannot synthesize complex gangliosides, such as GM1, GD1a, GD1b,GT1b, and GQ1b, to investigate the roles of complex gangliosidesin the pathogenesis of this disease. We used myelin-oligodendrocyteglycoprotein (MOG) as an immunogen. In active immunization EAE,the severity of clinical score was not different but the diseaseonset was significantly delayed in GM2/GD2–/– comparedwith those in wild-type mice. When we transferred MOG-reactiveT cells from GM2/GD2–/– or wild-type mice to wild-typemice, no significant differences were observed between the twogroups. In contrast, when we transferred MOG-reactive T cellsfrom wild-type mice to GM2/GD2–/– or to wild-typemice, the onset of EAE in GM2/GD2–/– mice was delayed.The recall response of MOG-specific T cells, the function ofantigen presenting cells, or the expression of several adhesionmolecules in the endothelium were not significantly differentbetween GM2/GD2–/– and wild-type mice. On the otherhand, quantitative analysis of cellular infiltration in thecentral nervous system (CNS) on day 9 of active immunizationEAE showed that the CD4+ cell number in the CNS isolated fromGM2/GD2–/– mice was significantly less than thatfrom wild-type mice. It indicated that the delayed onset ofEAE in GM2/GD2–/– mice was due to the delay of themigration of pathogenic T cells into the CNS. Thus, the complexgangliosides may be involved in the T cell–endothelialcell interaction in the pathogenetic process of EAE. 相似文献
20.
M Guilloux-Benatier O Pageault A Man M Feuillat 《Journal of industrial microbiology & biotechnology》2000,25(4):193-197
Oenococcus oeni exhibited extracellular β (1→3) glucanase activity. This activity increased when cells were cultivated with glycosidic cell-wall
macromolecules. In addition, the culture supernatant of the organism effectively lysed viable or dead cells of Saccharomyces cerevisiae. This lytic activity appeared in the early stationary phase of bacterial growth. Yeast cells at the end of the log phase
of growth were the most sensitive. The optimum temperature for lysis of viable yeast cells was 40°C, which is very different
from the temperatures observed in enological conditions (15–20°C). Moreover, the rate of the lytic activity was significantly
lower in comparison with yeast cell wall-degrading activities previously measured in various other microorganisms. Therefore,
yeast cell death that is sometimes observed during the alcoholic fermentation could hardly be attributed to the lytic activity
of O. oeni. Journal of Industrial Microbiology & Biotechnology (2000) 25, 193–197.
Received 27 December 1999/ Accepted in revised form 14 July 2000 相似文献