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1.
Maize (Zea mays L.) cell cultures incorporated radioactivity from [14C]cinnamate into hydroxycinnamoyl-CoA derivatives and then into polysaccharide-bound feruloyl residues. Within 5–20 min, the
CoA pool had lost its 14C by turnover and little or no further incorporation into polysaccharides then occurred. The system was thus effectively a
pulse–chase experiment. Kinetics of radiolabelling of diferulates (also known as dehydrodiferulates) varied with culture age.
In young (1–3 d) cultures, polysaccharide-bound [14C]feruloyl- and [14C]diferuloyl residues were both detectable within 1 min of [14C]cinnamate feeding. Thus, feruloyl residues were dimerised <1 min after their attachment to polysaccharides. For at least
the first 2.3 h after [14C]cinnamate feeding, polysaccharide-bound [14C]diferuloyl residues remained almost constant at ≈7% of the total polysaccharide-bound [14C]ferulate derivatives. Since feruloyl residues are attached to polysaccharides <1 min after the biosynthesis of the latter,
and >10 min before secretion, the data show that extensive feruloyl coupling occurred intra-protoplasmically. Exogenous H2O2 (1 mM) caused little additional feruloyl coupling; therefore, wall-localised coupling may have been peroxidase-limited. In
older (e.g. 4 d) cultures, less intraprotoplasmic coupling occurred: during the first 2.5 h, polysaccharide-bound [14C]diferuloyl residues were a steady 1.4% of the total polysaccharide-bound [14C]ferulate derivatives. In contrast to the situation in younger cultures, exogenous H2O2 induced a rapid 4- to 6-fold increase in all coupling products, indicating that coupling in the walls was H2O2-limited. In both 2- and 4-d-old cultures, polysaccharide-bound 14C-trimers and larger coupling products exceeded [14C]diferulates 3- to 4-fold, but followed similar kinetics. Thus, although all known dimers of ferulate can now be individually
quantified, it appears to be trimers and larger products that make the major contribution to cross-linking of wall polysaccharides
in cultured maize cells. We argue that feruloyl arabinoxylans that are cross-linked before and after secretion are likely
to loosen and tighten the cell wall, respectively. The consequences for the control of cell expansion and for the response
of cell walls to an oxidative burst are discussed.
Received: 19 January 2000 / Accepted: 13 April 2000 相似文献
2.
Summary. Ornithine decarboxylase (ODC) and diamine oxidase (DAO) are important enzymes involved in the metabolism of polyamines (putrescine,
spermidine and spermine). The influence of testosterone (T) and 17, β– estradiol (E2) on the activity of ODC and DAO was examined in cultivated normal rat kidney (NRK) epithelial cells. The results showed an
increase in enzyme activities 4 hours or 12 hours after hormonal treatment. Both T and E2 led to a significant increase (1.6-fold) in ODC protein level as compared to the controls. Cellular concentration of spermidine
and spermine increased (2.2- and 2.6-fold respectively) 4 hours after T addition. A higher levels in concentrations of putrescine
(1.4-fold) and spermine (1.5-fold) 12 hours after E2 treatment were observed. These results suggest that the biosynthesis and terminal oxidation of the polyamines in NRK epithelial
cells are androgen- and estrogen-mediated and depend on the hormonal sensitivity of the cells.
Received April 5, 1999, Accepted December 20, 1999 相似文献
3.
Palmieri G Montella L Aiello C Barbieri F Di Vizio D Schulz S Beninati S Budillon A Caraglia M Insabato L Florio T 《Amino acids》2007,32(3):395-400
Summary. Imatinib, a tyrosine kinase inhibitor directed against the enzymatic domain of KIT protein, was found to produce dramatic
clinical responses in metastatic gastrointestinal stromal tumors (GISTs). However, resistance usually develops thus determining
treatment failure. The present study was performed to analyse the expression of somatostatin receptor (SSTR) subtypes, modulators
of tissue transglutaminase, in a series of GISTs and leiomyosarcomas by immunohistochemistry to identify a new potential therapeutic
target. Sixteen cases (8 males and 8 females, age range: 38–73; 11 GISTs, 4 leiomyosarcomas, 1 leiomyoma) were studied. Immunohistochemical
detection of the relevant SSTRs was performed on paraffin-embedded tissue sections, stained with polyclonal antibodies directed
against the five somatostatin receptor subtypes. We found 7 out of 16 (44%) tumors expressing all SSTRs and 14 out of 16 (87%)
tumors positive for at least 3 subtypes. SSTR2A was the most represented subtype in the tumors studied, being expressed in approximately 70% of cases exhibiting an intense
labeling in most of these cases. The significant expression of SSTRs shown in this series of GISTs and gastrointestinal leiomyosarcomas
suggests a potential therapeutic target to be explored alone and/or in combination with other therapeutic agents in the setting
of refractory GI stromal tumors. 相似文献
4.
Summary. The expression of the protein crosslinking enzyme tissue transglutaminase (TG2, tTG), the ubiquitous member of transglutaminase
family, can be regulated by multiple factors. Although it has been suggested that TG2 can be involved in apoptotic cell death,
high levels of enzyme have also been associated with cell survival in response to different stimuli. Furthermore, evidence
indicates that increases in TG2 production cause enzyme translocation to cell membrane. Cell stress can also lead to TG2 accumulation
on the cell surface and in the extracellular matrix resulting in changes in cell-matrix interactions.
Here, we discuss the underlying mechanisms of TG2 up-regulation induced by various stimuli including glutamate exposure, calcium
influx, oxidative stress, UV, and inflammatory cytokines.
These findings agree with a postulated role for transglutaminases in molecular mechanisms involved in several diseases suggesting
that cross-linking reactions could be a relevant part of the biochemical changes observed in pathological conditions. 相似文献
5.
T. D. Nguyen Melanie J. Smith Peter Hersey 《Cancer immunology, immunotherapy : CII》1997,43(6):345-354
Determinants of T cell responses to tumor cells remain largely unknown. In the present study we have used long-term cultures
of human melanoma cells and autologous peripheral blood lymphocytes to examine the influence of cytokines with T cell growth
activity on the phenotype and cytotoxic and proliferative response of T cells to melanoma. It was found that addition of interleukin-4
(IL-4) inhibited the response of CD8+ T cells and promoted the response of the CD4 subset. IL-2 or IL-7 was effective in increasing melanoma-specific cytotoxic
T lymphocyte (CTL) activity in cultures where CD8 T cells were predominant, whereas IL-4 followed by IL-2 was most effective
in cultures where CD4 T cells predominated. IL-10 or IL-12 inhibited proliferation and CTL activity against melanoma in long-term
cultures. The effects of IL-12 were reproduced in long-term cultures of T cells stimulated with mAb against CD3 and were shown
to depend on prior exposure of T cells to IL-12 before IL-2. As yet unidentified factors, such as co-factor expression on
melanoma, appear to be as important as exogenous cytokines in determining the nature of T cell responses to melanoma. These
results suggest that analysis of responses in long-term culture may assist in defining the role of key cytokines and other
determinants of immune responses to melanoma.
Received: 4 June 1996 / Accepted: 12 November 1996 相似文献
6.
Batch cultures of photoautotrophic cell suspensions of Chenopodiumrubrum L., growing in an inorganic medium on CO2 under a daily balanced light–dark regime of 16 : 8 h could be maintained for approximately 100 d without subcultivation.
The long-lived cultures showed an initial cell division phase of 4 weeks, followed by a stationary phase of another 4 weeks,
after which ageing and progressive cell death reduced the number of living cells and the cultures usually expired after another
3–4 weeks. These developmental phases of the cell culture were characterised with respect to photosynthetic performance, dark
respiration, content of phytohormones and capacity of cell division. Cell division of the majority of the cells finished in
the G1- or G0-phase of the cell cycle, caused by a pronounced decline in the endogenous levels of auxin and cytokinins. Supply
of these growth factors to resting cells resulted in resumption of cytokinesis, at least by some of the cells. However, responsiveness
to the phytohomones declined during the stationary phase, and subcultivation was no longer possible beyond day 60 when the
phases of ageing and death commenced. Ageing was characterised by a further decline in the photosynthetic capacity of the
cells, by a climacteric enhancement of dark respiration, but also by a slight increase in the level of IAA and cytokinins
concomitant with a decrease in ethylene. Similarities and differences between the development of batch-cultured photoautotrophic
cells of C. rubrum and that of a leaf are discussed with respect to using the cell culture as a model for a leaf.
Received: 30 April 1999 / Accepted: 21 August 1999 相似文献
7.
Summary. The objective of this study was to assess the effect of taurine-depletion on cardiovascular responses of rat to vasoactive
agents. Male Wistar-Kyoto (WKY) rats were given either tap water (control) or 3% β-alanine (taurine-depleted) for three weeks.
Thereafter, mean arterial pressure (MAP) and heart rate of the freely moving animal were measured in response to vasoactive
agents. Administration of phenylephine (5–40 μg/kg/min; i.v.) resulted in a similar and significant increase in MAP but a
reduction in heart rate in both control and taurine-depleted groups. On the other hand, administration of sodium nitroprusside
(15–300 μg/kg/min; i.v.) elicited a similar and significant reduction in MAP but increased heart rate in both groups. Lack
of a differential response to phenylephrine and sodium nitroprusside between the two groups suggests that baroreflex regulation
of cardiovascular function is not adversely affected by taurine-depletion. Administration of angiotensin II (0.1–3.0 μg/kg/min;
i.v.) resulted in a dose-related increase in the pressor response and a decrease in heart rate in both groups. However, angiotensin
II-induced pressor response was reduced in the taurine-depleted compared to the control rats (p < 0.05); heart rate was similarly
reduced in both groups. Acute exposure to β-alanine (3 g/kg; i.v., 30-minutes) did not alter angiotensin II-induced hemodynamic
responses. Similarly, incubation of aortic rings with β-alanine (40 mM, 30 minutes) did not affect the contractile responses
to angiotensin II. The results suggest that β-alanine, per se, does not affect angiotensin II-induced responses in rat. However, β-alanine-induced taurine depletion is associated with
a reduction in the pressor response to angiotensin II without impairing baroreflex function.
Received December 17, 1999/Accepted January 12, 2000 相似文献
8.
Two-year-old rosemary (Rosmarinus officinalis L.) plants were subjected to severe stress by exposure to prolonged drought during a Mediterranean summer. Severely stressed
plants recovered completely after the autumn rainfalls although the relative water content remained below 35% for 3 months
and the chlorophyll content of leaves was reduced by up to 85% during the drought. In severe stress: (i) α-tocopherol increased
9-fold per g dry weight and 20-fold per unit of chlorophyll; (ii) lutein and β-carotene contents decreased on a dry-weight
basis, but an 80% increase in lutein and constant levels of β-carotene were observed on a chlorophyll basis; (iii) there were
transient and sustained increases in the de-epoxidation state of the xanthophyll cycle; and (iv) the highly oxidised abietane
diterpene isorosmanol increased 8-fold as a result of the oxidation of carnosic acid. With the autumn rainfalls, water status,
α-tocopherol and violaxanthin recovered first and the levels of photosynthetic pigments and abietane diterpenes increased
later. The photoprotection conferred by the xanthophyll cycle and the antioxidant function of tocopherols, lutein and diterpenes
may help to avoid irreversible damage in severe drought, making possible the recovery of functional membranes after the autumn
rainfalls. Besides, chlorophyll loss reduces the amount of photons absorbed by leaves, which enhances the photoprotective
and antioxidant capacity of leaves per amount of photons absorbed, since the ratios of xanthophylls, α-tocopherol and abietane
diterpenes to chlorophyll increase.
Received: 12 July 1999 / Accepted: 25 November 1999 相似文献
9.
Nath A Chattopadhya S Chattopadhyay U Sharma NK 《Cancer immunology, immunotherapy : CII》2006,55(12):1534-1541
The C–C chemokines, macrophage inflammatory protein (MIP)1α and MIP1β are potent chemoattractants for the monocytes, which form an important component of the stroma of tumor tissue and may regulate tumor growth and associated inflammation. We examined the role of MIP1α and MIP1β in inducing the release of inflammatory cytokines and the generation of tumoricidal monocytes from the peripheral blood monocytes (PBM) of healthy women and patients with carcinoma of breast (CaBr). Interleukin-1 (IL-1) and tumor necrosis factor (TNF) α release by the PBM was markedly stimulated by MIP1α in CaBr patients, but only marginally so in healthy women. In contrast, MIP1β stimulated the release of these cytokines by the PBM of healthy women, but failed to do so in CaBr patients. MIP1α, but not MIP1β, synergized with LPS in inducing the release of IL-1 from the PBM of both healthy women and CaBr patients. Both MIP1α and MIP1β augmented respiratory bursts in PBM and generated tumoricidal PBM that killed T24 cells, MIP1α being more effective in CaBr patients and MIP1β in healthy women. IFN-γ co-stimulated and IL-4 suppressed MIP1α and β-induced cytotoxicity in PBM. The synergy of IFN-γ was more marked with MIP1α than with MIP1β. The differential effects of MIP1α and MIP1β on the PBM of healthy women and CaBr patients co-related with the levels of expression of CCR1 and CCR5 in these monocytes. The expression of CCR5 was higher than that of CCR1 in the PBM of healthy women and the PBM of the CaBr patients showed overexpression of CCR1 and downregulation of CCR5. 相似文献
10.
Summary. 3-Hydroxynorvaline (HNV; 2-amino-3-hydroxypentanoic acid), a microbial L-threonine analogue, is toxic to mammalian cells and
displays antiviral properties. In view of this, we investigated the toxicity and/or potential teratogenicity of HNV in developing
chicken and mouse embryos. HNV was administered to chicken embryos (in ovo; dose 75–300 μmole/egg; 48 h post-incubation) and pregnant Hanover NMRI mice (per os; total dose 900–1800 mg/kg body mass; gestation days 7–9). Control animals received sterile saline solutions. Harvested embryos
(chicken embryos, 10 days post-incubation; mouse embryos; gestation day 18) were fixed in glutaraldehyde and stereomicroscopically
inspected for signs of dysmorphogenesis. Body mass, body and toe length and mortality of chicken embryos, and the body mass
and mortality of mouse embryos were recorded. HNV exposure significantly increased the incidence of embryotoxic (growth retardation,
toxic mortality) and congenital defects in both chicken and mouse embryos. All the observed effects were dose-dependent. In
conclusion, HNV is an embryotoxic and teratogenic compound, which caused significant developmental delay and congenital defects
in developing chicken and mouse embryos. 相似文献
11.
Glycerol 3-phosphate acyltransferase (GPAT, EC 2.3.15) catalyses the first step of the Kennedy pathway for acyl lipid formation.
This enzyme was studied using high-speed particulate fractions from oil palm (Elaeis guineensis Jacq.) tissue cultures and mesocarp acetone powders. The fractions were incubated with [14C]glycerol 3-phosphate and incorporation of radioactivity into Kennedy pathway intermediates studied. Optimal conditions were
broadly similar between the two preparations but those from fruit mesocarp clearly contained more active enzymes for the subsequent
stages of the Kennedy pathway – as exemplified by the appreciable accumulation of radioactivity in triacylglycerol. Experiments
with different acyl-CoA substrates showed that the GPAT in both high-speed particulate preparations had a significant preference
for palmitate. Glycerol 3-phosphate acyltransferase was solubilised from both preparations with optimal solubilisation being
achieved at 0.5% (w/v) CHAPS concentrations. Solubilised GPATs were purified further using DE52 ion-exchange chromatography
and Sephadex G-100 molecular exclusion chromatography. Purifications of up to about 70-fold were achieved. The purified GPATs
showed a strong preference for palmitoyl-CoA compared to other acyl-CoA donors, in keeping with the importance of palmitate
in palm oil.
Received: 22 April 1999 / Accepted: 29 July 1999 相似文献
12.
Summary. This study examined 10 wks of resistance training and the ingestion of supplemental protein and amino acids on muscle performance
and markers of muscle anabolism. Nineteen untrained males were randomly assigned to supplement groups containing either 20 g
protein (14 g whey and casein protein, 6 g free amino acids) or 20 g dextrose placebo ingested 1 h before and after exercise
for a total of 40 g/d. Participants exercised 4 times/wk using 3 sets of 6–8 repetitions at 85–90% of the one repetition maximum.
Data were analyzed with two-way ANOVA (p < 0.05). The protein supplement resulted in greater increases in total body mass, fat-free mass, thigh mass, muscle strength,
serum IGF-1, IGF-1 mRNA, MHC I and IIa expression, and myofibrillar protein. Ten-wks of resistance training with 20 g protein
and amino acids ingested 1 h before and after exercise is more effective than carbohydrate placebo in up-regulating markers
of muscle protein synthesis and anabolism along with subsequent improvements in muscle performance. 相似文献
13.
Gyurko R Siqueira CC Caldon N Gao L Kantarci A Van Dyke TE 《Journal of immunology (Baltimore, Md. : 1950)》2006,177(10):7250-7256
The role of polymorphonuclear neutrophils (PMN) in mediating diabetic tissue damage to the periodontium was investigated in a novel model of chronic hyperglycemia, the Akita mouse. Induction of acute peritoneal inflammation in wild-type (WT) and Akita mice resulted in exaggerated IL-6 response in Akita mice (2.9-fold increase over WT values) and a markedly increased chemokine response (KC, 2.6-fold; MCP-1, 2.6-fold; and MIP-1alpha, 4.4-fold increase over WT values). Chemotaxis to both fMLP and WKYMVm was significantly reduced in isolated Akita PMN compared with WT PMN as measured in a Boyden chamber. Superoxide release in contrast was significantly increased in Akita PMN as measured with cytochrome c reduction. Bone marrow-derived Akita PMN showed partial translocation of p47phox to the cell membrane without external stimulation, suggesting premature assembly of the superoxide-producing NADPH oxidase in hyperglycemia. In vivo studies revealed that ligature-induced periodontal bone loss is significantly greater in Akita mice compared with WT. Moreover, intravital microscopy of gingival vessels showed that leukocyte rolling and attachment to the vascular endothelium is enhanced in periodontal vessels of Akita mice. These results indicate that chronic hyperglycemia predisposes to exaggerated inflammatory response and primes leukocytes for marginalization and superoxide production but not for transmigration. Thus, leukocyte defects in hyperglycemia may contribute to periodontal tissue damage by impairing the innate immune response to periodontal pathogens as well as by increasing free radical load in the gingival microvasculature. 相似文献
14.
Mastoparan induces Ca2+-dependent deflagellation of the unicellular green alga Chlamydomonas moewusii Gerloff, as well as the activation of phospholipase C and the production of inositol 1,4,5-trisphosphate (InsP3; T. Munnik et al., 1998, Planta 207: 133–145). Even in the absence of extracellular Ca2+, mastoparan still induces deflagellation (L.M. Quarmby and H.C. Hartzell, 1994, J Cell Biol 124: 807–815; J.A.J. van Himbergen
et al., 1999, J Exp Bot, in press) suggesting that InsP3 mediates Ca2+ release from intracellular stores. To test this hypothesis, cells were pre-loaded with 45Ca2+ and their plasma membranes permeabilized by digitonin. Subsequent treatment of the cells with mastoparan (3.5 μM) induced
release of intracellular 45Ca2+. Mastoparan also activated phospholipase C in permeabilized cells, as demonstrated by the breakdown of 32P-phosphatidylinositol 4,5-bisphosphate and the production of diacylglycerol. The mastoparan analogues mas7 and mas17 were
also effective and their efficacy was correlated with their biological activity. X-ray microanalysis showed that electron-dense
bodies (EDBs) are a major Ca2+ store in C. moewusii. Analysis of digitonin-permeabilized cells showed that EDBs lost calcium at digitonin concentrations that released radioactivity
from 45Ca2+-labelled cells, suggesting that 45Ca2+ monitored the content of EDBs. X-ray microanaysis of living cells treated with mastoparan also revealed that calcium was
released from EDBs.
Received: 30 December 1998 / Accepted: 25 June 1999 相似文献
15.
Inactivation of DNA replication origins by the cell cycle regulator, trigonelline, in root meristems of Lactuca sativa 总被引:4,自引:0,他引:4
The effects of trigonelline (TRG) on the cell cycle in root meristems of Lactuca sativa L. were examined in the knowledge that TRG is a cell cycle regulator that causes cell arrest in G2, and prevents ligation
of replicons in S-phase. The hypothesis was tested that continuous exposure to TRG would perturb DNA replication which, in
turn, would lengthen the cell cycle and impair root elongation. Using DNA fibre autoradiography, mean replicon size was 31
and 13 μm in the TRG (3 mM) and control treatments, respectively. Trigonelline also resulted in a lengthening of both S-phase
and the cell cycle and a decrease in primary root elongation. Hence, replicon inactivation was responsible for the protracted
S-phase. Trigonelline treatment also resulted in a 1.6-fold increase in fork rate (13.8 μm h−1) compared with the control (8.4 m h−1). The faster fork rate in the larger replicons is in accord with the highly significant positive relationship already established
between fork rate and replicon size for various unrelated higher plants.
Received: 11 October 1999 / Accepted: 23 December 1999 相似文献
16.
Chemokine and chemokine receptor expression in gingival tissues plays a central role in periodontal disease during aging.
In the present study, we explored the modulation of chemokines and chemokine receptors expression in aging rat gingival tissues.
In the 24-month-old (Old) rat gingival tissues, RANTES and CCR5 mRNA and protein levels were 2–4 fold increased over those
of the 6-month-old (Young) rats. The Old rats had considerable enhancement of all three of the studied MAPK activities: extracellular
signal regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38 MAPK. These results suggest that age-related increases in RANTES and CCR5 expression are associated
with increased IκBα, nuclear NF-κB, and MAPK activity in gingival tissues. 相似文献
17.
Herbivore-induced ethylene suppresses a direct defense but not a putative indirect defense against an adapted herbivore 总被引:28,自引:1,他引:28
Herbivory induces both direct and indirect defenses in plants; however, some combinations of these defenses may not be compatible.
The jasmonate signal cascade activated both direct (nicotine accumulations) and indirect (mono- and sesquiterpene emissions)
whole-plant defense responses in the native tobacco Nicotiana attenuata Torr. Ex Wats. Nicotine accumulations were proportional to the amount of leaf wounding and the resulting increases in jasmonic acid (JA)
concentrations. However, when larvae of the nicotine-tolerant herbivore, Manduca sexta, fed on plants or their oral secretions were applied to leaf punctures, the normal wound response was dramatically altered,
as evidenced by large (4- to 10-fold) increases in the release of (i) volatile terpenoids and (ii) ethylene, (iii) increased
(4- to 30-fold) accumulations of endogenous JA pools, but (iv) decreased or unchanged nicotine accumulations. The ethylene
release, which was insensitive to inhibitors of induced JA accumulation, was sufficient to account for the attenuated nicotine
response. Applications of ethylene and ethephon suppressed the induced nicotine response and pre-treatment of plants with
a competitive inhibitor of ethylene receptors, 1-methylcyclopropene, restored the full nicotine response. This ethylene burst,
however, did not inhibit the release of volatile terpenoids. Because parasitoids of Manduca larvae are sensitive to the dietary intake of nicotine by their hosts, this ethylene-mediated switching from direct to a
putative indirect defense may represent an adaptive tailoring of a plant's defense response.
Received: 13 June 1999 / Accepted: 21 August 1999 相似文献
18.
Hultsch C Bergmann R Pawelke B Pietzsch J Wuest F Johannsen B Henle T 《Amino acids》2005,29(4):405-413
Summary. Isopeptide bonds between the ɛ-amino group of lysine and the γ-carboxamide group of glutamine are formed during strong heating
of pure proteins or, more important, by enzymatic reaction mediated by transglutaminases. Despite the wide use of a microbial
transglutaminase in food biotechnology, up to now little is known about the metabolic fate of the isopeptide Nɛ-(γ-glutamyl)-L-lysine. In the present study, N-succinimidyl-4-[18F]fluorobenzoate was used to modify Nɛ-(γ-glutamyl)-L-lysine at each of its two α-amino groups, resulting in the 4-[18F]fluorobenzoylated derivatives, for which biodistribution, catabolism, and elimination were investigated in male Wistar rats.
A significant different biochemical behavior of the two labelled isopeptides was observed in terms of in vitro stability, in vivo metabolism as well as biodistribution. The results suggest that the metabolic fate of isopeptides is likely to be dependent
on how they are reabsorbed – free or peptide bound. 相似文献
19.
This study investigates the effect of different cytokines on the growth and antitumor activity of the α CD3-induced killer
cells CD3-AK, and the potential of the use of CD3-AK cells in cancer immunotherapy. Eight cytokines were tested. Only three
(interleukin-2, -4 and -7) were able to support the growth of CD3-AK cells, which selectively killed different tumor targets
of diversified origin. Culturing in interleukin-4 (IL-4) or IL-7 alone could maintain the growth of CD3-AK cells for 6 – 8
days. Only IL-2 could maintain long-term growth, but further addition of IL-4 exerted an inhibitory effect, which terminated
the cell growth in 2 weeks. In contrast, despite the fact that IL-7 inhibited the proliferation of CD3-AK cells cultured in
IL-2, as determined by [3H]thymidine uptake, the recovery of viable cells was not reduced. In 10 days, CD3-AK cells cultured in IL-2 alone or IL-2
plus IL-7 increased 160- or 176-fold respectively. There is an inverse relationship between the in vitro growth ability and
Fas expression on the CD3-AK cells. Further, IL-7 increased the cytolytic activity of the CD3-AK cells two- to threefold.
CD3-AK cells could be maintained in IL-2 or IL-2 plus IL-7 for 60 – 240 days or more. The long-term-cultured CD3-AK cells
not only possessed a high level of cytolytic activity, but also showed a wide spectrum of killing with different tumor targets;
the normally “resistant” targets, such as EL-4 lymphoma, fibrosarcoma, or melanoma, became susceptible. When the in vivo antitumor
activity of the CD3-AK cells against a non-immunogenic tumor, EL-4, was tested by tumor-neutralization experiments, we found
that only the long-term-cultured cells gave significant protection, with those maintained in both IL-2 and IL-7 giving the
highest degree of protection. Thus, these long-term-cultured CD3-AK cells may have the potential to be used for immunotherapy
of a variety of tumors whatever their immunogenicity.
Received: 7 August 1996/accepted: 10 October 1996 相似文献
20.
Transgenic Nicotiana tabacum and Arabidopsis thaliana plants overexpressing allene oxide synthase 总被引:3,自引:0,他引:3
Allene oxide synthase (AOS), encoded by a single gene in Arabidopsis thaliana (L.) Heynh., catalyzes the first step specific to the octadecanoid pathway. Enzyme activity is very low in control plants,
but is upregulated by wounding, octadecanoids, ethylene, salicylate and coronatine (D. Laudert and E.W. Weiler, 1998, Plant
J 15: 675–684). In order to study the consequences of constitutive expression of AOS on the level of jasmonates, a complete
cDNA encoding the enzyme from A. thaliana was constitutively expressed in both A. thaliana and tobacco (Nicotiana tabacum L.). Overexpression of AOS did not alter the basal level of jasmonic acid; thus, output of the jasmonate pathway in the unchallenged
plant appears to be strictly limited by substrate availability. In wounded plants overexpressing AOS, peak jasmonate levels
were 2- to 3-fold higher compared to untransformed plants. More importantly, the transgenic plants reached the maximum jasmonate
levels significantly earlier than wounded untransformed control plants. These findings suggest that overexpression of AOS
might be a way of controlling defense dynamics in higher plants.
Received: 10 February 2000 / Accepted: 11 March 2000 相似文献