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141.
Summary Activation of lymphocytes by interleukin-2 (IL-2) induces lymphokine-activated killer (LAK) cells that show promising effects on tumour growth in clinical trials. We examined the effect of the superantigen staphylococcal enterotoxin A (SEA) on anti-tumour activity of freshly prepared human lymphocytes. Picomolar amounts of SEA rapidly induced cytotoxic activity against K562 and Raji cells as well as some natural-killer(NK)-resistant tumour cell lines. Cytotoxic activity was not dependent on target cell expression of either major histocompatibility complex (MHC) class I or II antigens as shown using mutated cell lines. Cell-sorting experiments showed that the activity was expressed by NK (CD5CD56+) as well as T (CD5+) cells, although the former contained the majority of cytotoxic activity. NK cells could not be directly activated by SEA. In contrast, SEA activated purified T cells to the same extent as in bulk cultures. It is suggested that SEA activation of NK cells is secondary to that brought about by lymphokines produced by T cells. Activation of LAK cells with SEA was comparable in magnitude as well as target cell spectrum to that of IL-2. In addition to the LAK-like cytotoxic activity induced by SEA, a superimposed cytotoxicity towards target cells expressing MHC class II antigens coated with SEA was observed. This staphylococcal-enterotoxin-dependent cell-mediated cytotoxicity (SDCC) was exclusively mediated by T cells. It is well established that MHC class II antigens function as receptors for staphylococcal enterotoxins on mammalian cells and that the complex between MHC class II antigen and — SEA apparently functions as a target structure for activated T cells with target cell lysis as a consequence. Activation of T lymphocytes with IL-2 also resulted in the capability to mediate SDCC. Staphylococcal enterotoxins represent a novel way of inducing anti-tumour activity in human lymphocytes, which could be of value in therapeutic applications.  相似文献   
142.
Summary Conditions were used where the action of porcine pancreatic phospholipase A2 on phospholipids can be followed in the absence of added calcium and the catalytic activity is supported by the calcium brought with the nanomolar enzyme. Therefore, alterations in the enzyme velocity resulting from the presence of spermine or spermidine could be specifically studied using 1-palmitoyl-2-(pyren-1-yl)hexanoyl-sn-glycero-3-phosphocholine (PPHPC) and 1-palmitoyl-2-(pyren-1-yl)hexanoyl-sn-glycero-3-phosphoglycerol (PPHPG) as substrates. Both spermine and spermidine activated the hydrolysis of PPHPG fourfold at polyamine/phospholipid molar ratios of approximately 11 and 121, respectively. Double-reciprocal plots of enzyme activityvs. PPHPG concentration revealed the enhancement to be due to increased apparentV max while the apparentK m was slightly increased. In the presence of 4mm CaCl2 inhibition by polyamines of PPHPG hydrolysis by phospholipase A2 was observed. Using synthetic diamines we could further demonstrate that two primary amino groups are required for the activation. In the absence of exogenous CaCl2 polyamines inhibited the hydrolysis of PPHPC by phospholipase A2. The presence of 4mm CaCl2 reversed this inhibition and a twofold activation was observed at 10 m spermine. The results obtained indicate that the activation of PLA2 by spermine and spermidine is produced at the level of the substrate, PPHPG. This implies the formation of complexes of phosphatidylglycerol and polyamines with defined stoichiometries.  相似文献   
143.
Summary The net loss of KCl observed in Ehrlich ascites cells during regulatory volume decrease (RVD) following hypotonic exposure involves activation of separate conductive K+ and Cl transport pathways. RVD is accelerated when a parallel K+ transport pathway is provided by addition of gramicidin, indicating that the K+ conductance is rate limiting. Addition of ionophore A23187 plus Ca2+ also activates separate K+ and Cl transport pathways, resulting in a hyperpolarization of the cell membrane. A calculation shows that the K+ and Cl conductance is increased 14-and 10-fold, respectively. Gramicidin fails to accelerate the A23187-induced cell shrinkage, indicating that the Cl conductance is rate limiting. An A23187-induced activation of42K and36Cl tracer fluxes is directly demonstrated. RVD and the A23187-induced cell shrinkage both are: (i) inhibited by quinine which blocks the Ca2+-activated K+ channel. (ii) unaffected by substitution of NO 3 or SCN for Cl, and (iii) inhibited by the anti-calmodulin drug pimozide. When the K+ channel is blocked by quinine but bypassed by addition of gramicidin, the rate of cell shrinkage can be used to monitor the Cl conductance. The Cl conductance is increased about 60-fold during RVD. The volume-induced activation of the Cl transport pathway is transient, with inactivation within about 10 min. The activation induced by ionophore A23187 in Ca2+-free media (probably by release of Ca2+ from internal stores) is also transient, whereas the activation is persistent in Ca2+-containing media. In the latter case, addition of excess EGTA is followed by inactivation of the Cl transport pathway. These findings suggest that a transient increase in free cytosolic Ca2+ may account for the transient activation of the Cl transport pathway. The activated anion transport pathway is unselective, carrying both Cl, Br, NO 3 , and SCN. The anti-calmodulin drug pimozide blocks the volume- or A23187-induced Cl transport pathway and also blocks the activation of the K+ transport pathway. This is demonstrated directly by42K flux experiments and indirectly in media where the dominating anion (SCN) has a high ground permeability. A comparison of the A23187-induced K+ conductance estimated from42K flux measurements at high external K+, and from net K flux measurements suggests single-file behavior of the Ca2+-activated K+ channel. The number of Ca2+-activated K+ channels is estimated at about 100 per cell.  相似文献   
144.
Development and Characterization of Pantothenic Acid Transport in Brain   总被引:1,自引:1,他引:0  
In vitro, the transport of [3H]pantothenic acid into and from rabbit brain slices was studied. In newborn rabbits and throughout development, forebrain and cerebellar slices were able to accumulate and phosphorylate [3H]pantothenic acid comparably to slices from adults. The accumulation and phosphorylation of [3H]pantothenic acid by adult forebrain slices were not decreased by substitution of LiCl for NaCl in the artificial CSF or by addition of short-chain fuels (e.g., 5 mM pyruvate or acetoacetate) to the medium. However, probenecid and ouabain (both 1 mM) and medium-chain fatty acids (e.g., 0.1 mM octanoate, nonanoate, and decanoate) profoundly inhibited [3H]pantothenic acid accumulation by forebrain slices but not intracellular phosphorylation and conversion to [3H]CoA. There in vitro results suggest that brain slices accumulate pantothenic acid by a saturable system (probably facilitated diffusion) that is sensitive to inhibition by probenecid and medium-chain fatty acids.  相似文献   
145.
Passive influx of 45Ca2+ into non-growing corn root tissue ( Zea mays L.) was increased as a result of actions (cutting, rubbing, chilling, heating, acidifying) or agents (cyanide, uncouplers) known to depolarize the cell membrane, and was decreased by actions (washing) or agents (fusicoccin) known to hyperpolarize it. These responses indicate the presence of Ca2+ channels which are voltage controlled. If the injuries were extensive, however, voltage control was lost and hyperpolarization with fusicoccin was expressed by increased 45Ca2+ influx. Control could be regained by tissue washing, and millimolar levels of external Ca2+ would protect against loss of control. Influx of Ca2+ was strongly inhibited by La3+, but only weakly by verapamil. Intact roots showed greater cold shock sensitivity in maturing cells than in growing cells. We conclude that corn roots normally restrict Ca2+ influx by a mechanism linked to hyper-polarization of the plasmalemma.
Calcium ions which enter cold-shocked tissue are partially extruded during the early phase of recovery by a process stimulated by fusicoccin and subject to uncoupling.  相似文献   
146.
The dependence of gamma-aminobutyric acid (GABA) and acetylcholine (ACh) release on Ca2+ was comparatively studied in synaptosomes from mouse brain, by correlating the influx of 45Ca2+ with the release of the transmitters. It was observed that exposure of synaptosomes to a Na+-free medium notably increases Ca2+ entry, and this condition was used, in addition to K+ depolarization and the Ca2+ ionophore A23187, to stimulate the influx of Ca2+ and the release of labeled GABA and ACh. The effect of ruthenium red (RuR) on these parameters was also investigated. Of the three experimental conditions used, the absence of Na+ in the medium proved to be the most efficient in increasing Ca2+ entry. RuR inhibited by 60-70% the influx of Ca2+ stimulated by K+ depolarization but did not affect its basal influx or its influx stimulated by the absence of Na+ or by A23187. The release of ACh was stimulated by K+ depolarization, absence of Na+ in the medium, and A23187 in a strictly Ca2+-dependent manner, whereas the release of GABA was only partially dependent on the presence of Ca2+ in the medium. The extent of stimulation of ACh release was related to the extent of Ca2+ entry, whereas no such correlation was observed for GABA. In the presence of Na+, RuR did not affect the release of the transmitters induced by A23187. In the absence of Na+, paradoxically RuR notably enhanced the release of both ACh and GABA induced by A23187, in a Ca2+-dependent manner.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
147.
Experiments were undertaken to define the role of two calcium-associated enzyme systems in modulating transmitter-stimulated production of cyclic nucleotides in rat brain. Cyclic AMP (cAMP) accumulation was examined in cerebral cortical slices using a prelabeling technique. The enhancement of isoproterenol-stimulated cAMP production by alpha-adrenergic and gamma-aminobutyric acid-B (GABAB) agonists was reduced by exposing the tissue to EGTA, a chelator of divalent cations, or quinacrine, a nonselective inhibitor of phospholipase A2. Likewise, chronic (2 weeks) administration of corticosterone decreased the alpha-adrenergic and GABAB receptor modulation of second messenger production. Neither cyclooxygenase nor lipoxygenase inhibitors selectively influenced the facilitating response of alpha-adrenergic and GABAB agonists. Other experiments revealed that although norepinephrine and 6-fluoronorepinephrine stimulated inositol phosphate (IP) production in cerebral cortical slices with potencies equal to those displayed in the cyclic nucleotide assay, selective alpha 1-adrenergic agonists were less efficacious on IP formation and were without effect in the cAMP assay. Conversely, a selective alpha 2-adrenergic receptor agonist facilitated the cAMP response to a beta-adrenergic agonist without affecting IP formation. The rank orders of potency of a series of alpha-adrenergic antagonists suggest that IP accumulation is mediated solely by alpha 1-adrenergic receptors, whereas the augmentation of cAMP accumulation is regulated by a mixed population of alpha-adrenergic sites. The results suggest that the alpha-adrenergic and GABAB receptor-mediated enhancement of isoproterenol-stimulated cAMP formation appears to be more closely associated with phospholipase A2 than phospholipase C and may be mediated by arachidonate or some other fatty acid.  相似文献   
148.
用聚丙烯酰胺凝胶电泳方法分析了流行性感冒病毒重组株京生75-29R2 T1(H3N2)及冷适应株31-广(H3N2)的RNA及多肽。重组株京生75-29R2 T1的HA及M基因系来自流行病毒亲本株/甲/北京/29/75(H3N2),而P_2、NA、NP及NS基因则来自温度敏感母株福R3(H2N2)。流行病毒株甲/穗/03/68(H3N2)在低温条件下经鸡胚尿囊腔传递24代而获得的冷适应疫苗毒株31-广(H3N2)其基因型与野毒株一致。  相似文献   
149.
The effects of adequate and restricted dietary protein and vitamin A on responses to infections by Nippostrongylus brasiliensis and N. brasiliensis plus Eimeria nieshulzi were determined in growing Sprague-Dawley rats. Infected rats experienced anorexia followed by a rebound in consumption that compensated for weight losses during anorexia. On certain days, reductions in the urinary/fecal nitrogen ratio, fecal and absorbed nitrogen, and apparent nitrogen and dry matter digestibilities occurred with the combined infections but not with those by nematodes alone. Effects of different levels of vitamin A were expressed only as an increase in nitrogen absorption occurring during the post-anoretic increase in appetite found with infected rats and in rats restricted in protein but receiving the higher level of the vitamin. Protein level was the most significant treatment effect: rats on high protein performed significantly better than those on low, regardless of the level of the other experimental variables.  相似文献   
150.
日本血吸虫尾蚴的组织化学及扫描电镜观察   总被引:8,自引:1,他引:7  
日本血吸虫尾蚴具有一个头腺、2对前钻腺及3对后钻腺,其解剖学位置、构造、化学成分及功能均有区别。钻腺分泌物含有多糖酶及蛋白酶。尾蚴的前端系特化的头器结构,它具有半月形嵴、钻腺开口及乳突。  相似文献   
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