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11.
Peter A. Lando Gunnar Hedlund Mikael Dohlsten Terje Kalland 《Cancer immunology, immunotherapy : CII》1991,33(4):231-237
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 (CD5–CD56+) 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
12.
Michael R. Ibbotson 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1991,168(1):91-102
This paper describes the morphology and response characteristics of two types of paired descending neurons (DNs) (classified as DNVII1 and DNIV1) and two lobula neurons (HR1 and HP1) in the honeybee, Apis mellifera.
相似文献
1. | The terminal arborizations of the lobula neurons are in juxtaposition with the dendritic branches of the DNs (Figs. 2, 3b, 5). Both of the DNs descend into the ipsilateral side of the thoracic ganglia via the dorsal intermediate tract (Fig. 6) and send out many blebbed terminal branches into the surrounding motor neuropil (Figs. 3c, 7). |
2. | Both the lobula and descending neurons respond in a directionally selective manner to the motion of widefield, periodic square-wave gratings. |
3. | The neurons have broad directional tuning curves (Figs. 10, 11). HR1 is maximally sensitive to regressive (back-to-front) motion and HP1 is maximally sensitive to progressive (front-to-back) motion over the ipsilateral eye (Fig. 11). DNVII1 is maximally sensitive when there is simultaneous regressive motion over the ipsilateral eye and progressive motion over the contralateral eye (Fig. 12a). Conversely, DNIV1 is optimally stimulated when there is simultaneous progressive motion over the ipsilateral eye and regressive motion over the contralateral eye (Fig. 12b). |
4. | The response of DNIV1 is shown to depend on the contrast frequency (CF) rather than the angular velocity of the periodic gratings used as stimuli. The peak responses of both regressive and progressive sensitive DNs are shown to occur at CFs of 8–10 Hz (Figs. 13, 14). |
13.
Transmembrane diffusion of hydrophobic antimicrobial agents and cell surface hydrophobicity in Bacteroides fragilis 总被引:1,自引:0,他引:1
The transmembrane diffusion of hydrophobic antimicrobial agents, e.g. lincomycin and clindamycin, was examined in Bacteroides fragilis which is sensitive to these agents. The results showed that these agents penetrate efficiently through the outer membrane. Cell surface hydrophobicity measured by the partition assay between water and p-xylene revealed that the cell surface of B. fragilis is more hydrophobic than that of Salmonella typhimurium or Pseudomonas aeruginosa. Furthermore, treatment with low concentrations of surfactant caused cell lysis. These results suggest that the cell surface hydrophobicity in B. fragilis plays an important role in the efficient transmembrane penetration of hydrophobic compounds. This efficiency explains the susceptibility of B. fragilis to hydrophobic antimicrobial agents. 相似文献
14.
Summary 1-Methylguanine and 7-methylguanine, both metabolic products of tRNA degradation, are known to induce transformation of Chinese hamster fibroblasts in culture. The effects of these compounds on the cell membrane have been studied by the method of Concanavalin A-mediated hemadsorption. 1-Methylguanine or 7-methylguanine induced a 50% increase of Con A-mediated hemadsorption within 20 hours of exposure of the cells to the agent at a concentration of 10-5 M. This alteration was reversed within 13 days when the cells were grown in the control medium. Prolonged treatment with 1-methylguanine or 7-methylguanine resulted in changes which were only slowly reversed during growth of the cells in the control medium. The effect of the methylated purines on the cell membrane could be completely inhibited by simultaneous addition of dibutyryl-cAMP at a concentration of 10-5 M. The possible mechanism of cell membrane alteration by methylated purines and its relevance to transformation in vitro are discussed. 相似文献
15.
Anita K. Costa Dominic F. Heffel Thomas M. Schieble James R. Trudell 《In vitro cellular & developmental biology. Plant》1987,23(7):501-506
Summary Inasmuch as it is known that the toxicity of anesthetic agents is potentiated by hypoxia and that the reductive metabolism
of these agents results in the formation of lipid hydroperoxides, we investigated the toxicity of hydroperoxides under low-oxygen
concentrations. We found that hypoxia exacerbates the toxicity oft-butyl hydroperoxide, shifting the dose-response curve oft-butyl hydroperoxide vs. lysis of hepatocytes approximately an order of magnitude to the left. Furthermore, although at the
end of a 4-h exposure to 0.5% O2 hepatocyte monolayers seemed normal by three indices (release of51Cr and serum glutamate transaminase or exclusion of trypan blue), they were completely lysed after an additional 20 h reoxygenation
at 20%. O2. In contrast, monolayers exposed to 2% O2 for 4 h seemed normal after 20 h reoxygenation. However, cells exposed to both a subtoxic dose of hydroperoxide and 4 h of
2% O2, although seeming healthy at the end of the hypoxic period, were completely lysed within 20 h after reoxygenation.
The study was supported by grant OH 00978 from the National Institutes for Occupational Safety and Health, Atlanta, Georgia. 相似文献
16.
D. J. Conklin H. B. Lillywhite K. R. Olson R. E. Ballard A. R. Hargens 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,165(7):518-526
The effects of vasoactive agonists on systemic blood vessels were examined with respect to anatomical location and gravity acclimation in the semi-arboreal snake, Elaphe Obsoleta. Major blood vessels were reactive to putative neurotransmitters, hormones or local factors in vessel specific patterns. Catecholamines, adenosine triphosphate, histamine and high potassium (80 mM) stimulated significantly greater tension per unit vessel mass in posterior than anterior arteries. Anterior vessels were significantly more sensitive to catecholamines than midbody and posterior vessels. Angiotensin II stimulated significantly greater tension in carotid artery than in midbody and posterior dorsal aorta. Arginine vasotocin strongly contracted the left and right aortic arches and anterior dorsal aorta. Veins were strongly contracted by catecholamines, high potassium and angiotensin II, but less so by adenosine triphosphate, arginine vasotocin and histamine. Precontracted vessels were relaxed by acetylcholine and sodium nitroprusside, but not by atrial natriuretic peptide or bradykinin. Chronic exposure of snakes to intermittent hypergravity stress (+1.5 Gz at tail) did not affect the majority of vessel responses. These data demonstrate that in vitro tension correlates with known patterns of sympathetic innervation and suggest that catecholamines, as well as other agonists, are important in mediating vascular responses to gravitational stresses in snakes.Abbreviations
ACH
acetylcholine
-
ADA
anterior dorsal aorta
-
ANG II
salmon asn1-val5-angiotensin II
-
ANP
rat ile26-atrial natriuretic peptide
-
ATP
adenosine triphosphate
-
AVT
arginine vasotocin
-
BK
human bradykinin
-
BL
total body length
-
CA
carotid artery
-
CONT
control
-
EC
50
effective concentration producing 50% maximal response
-
EPI
epinephrine
- + G
z
earth's gravity force
-
HI-G
high gravity acclimation
-
HI K
+
80 mM high potassium
-
JV
jugular vein
-
LAA
left aortic arch
-
MDA
midbody dorsal aorta
-
MPV
midbody portal vein
-
MS
Mackenzie's solution
-
NEPI
norepinephrine
-
pD
2
log EC50
-
PDA
posterior dorsal aorta
-
PPV
posterior portal vein
-
RAA
right aortic arch
-
SNP
sodium nitroprusside 相似文献
17.
Zuhal Keskil Cem Z. G rgü n Ugur Hodoglugil Hakan Zengil 《Chronobiology international》1996,13(6):465-475
The presence of time-dependent variations in the in vitro sensitivity of aorta preparations to either vasoconstricting or relaxing agents was investigated in rats maintained in light from 08: 00 to 20: 00 and in darkness from 20: 00 to 08: 00. Rat thoracic aorta rings were obtained from animals sacrificed at four different times of the day. The rat aorta was found to be more sensitive to the constricting effect of phenylephrine at 15: 00, and of 5-hydroxytryptamine at 21: 00. On the other hand, both endothelium-dependent and -independent relaxations were more remarkable at 03: 00 than at other times of the day. These variations represented significant circadian rhythms when analyzed by analysis of variance. Different in vitro responsiveness to these agents might reflect changes in the sensitivity and/or number of related receptors in vascular preparations. In conclusion, the circadian time of animal sacrifice to obtain vascular preparations constitutes an important aspect of the research method and a key determinant of findings. (Chronobiology International, 13(6), 465-475, 1996) 相似文献
18.
Gabriel Gutiérrez Josep Casadesús Jose L. Oliver Antonio Marine 《Journal of molecular evolution》1994,39(4):340-346
E. coli genes that contain a high frequency of the tetranucleotide CTAG are also rich in the tetramers CTTG, CCTA, CCAA, TTGG, TAGG, and CAAG (group-I tetramers). Conversely, E. coli genes lacking CTAG are rich in the tetranucleotides CCTG, CCAG, CTGG, and CAGG (group-II tetramers). These two gene samples differ also in codon usage, amino acid composition, frequency of Dcm sites, and contrast vocabularies. Group-I tetramers have in common that they are depleted by very-short-patch repair (VSP), while group-II tetramers are favored by VSP activity. The VSP system repairs G:T mismatches to G:C, thereby increasing the overall G+C content of the genome; for this reason the CTAG-rich sample has a lower G+C content than the CTAG-poor sample. This compositional heterogeneity can be tentatively explained by a low level of VSP activity on the CTAG-rich sample. A negative correlation is found between the frequency of group-I tetramers and the level of gene expression, as measured by the Codon Adaptation Index (CAI). A possible link between the rate of VSP activity and the level of gene expression is considered.Correspondence to: A. Marine 相似文献
19.
Maryna van de Venter Derek Litthauer Willem Oelofsen 《Journal of cellular biochemistry》1994,54(1):1-10
Adipocyte precursors from the stromal vascular fraction of human adipose tissue were allowed to differentiate in serum-free defined medium, whereafter their catecholamine stimulated lipolytic response was compared to that of mature isolated human adipocytes. Seventy-five to ninety percent of the fibroblast-like cells accumulated lipid droplets and glycerol-3-phosphate dehydrogenase activities of 1,000–2,800 mU/mg protein were measured in cell homogenates of differentiated cells. Lipolysis could be stimulated by both isoproterenol and norepinephrine in both differentiated preadipocytes as well as mature adipocytes. The results obtained with β-adrenergic agents suggested the presence of a higher affinity receptor in differentiated preadipocytes as compared to mature adipocytes. Mature adipocytes responded well to β-adrenergic agents, but no antilipolytic α2-adrenergic response was observed in the differentiated preadipocytes. The presence of Gi proteins in the differentiated preadipocytes was suggested by the antilipolytic effect of adenosine as well as the lipolytic activity generated by pertussis toxin. In conclusion, our medium supported the differentiation of a very high percentage of human preadipocytes which developed a sensitive β-adrenergic lipolytic response but which lacked an α2-adrenergic antilipolytic response. 相似文献
20.
HPLC and 1H-NMR methods for the quantitation of the (R)-enantiomer in (?)-(S)-timolol maleate were developed and validated. The HPLC method requires a 25 cm × 4.6 mm 5 μm Chiracel OD-H (cellulose tris-3,5-dimethylphenylcarbamate) column, a mobile phase of 0.2% (v/v) diethylamine and 4% (v/v) isopropanol in hexane at a flow rate of 1 ml/min and UV detection at 297 nm. A system suitability test was devised to verify the separation of the (R)- and (S)-enantiomers of timolol from other drug-related impurities. The NMR method requires the use of a high-field NMR spectrometer (>360 MHz) and a chiral solvating agent, (?)-(R)-2,2,2-trifluoro-1-(9-anthrylethanol) (R-TFAE). The limits of quantitation were 0.05% and 0.2% (m/m) for HPLC and NMR, respectively. The methods were applied to the determination of the (R)-enantiomer in eight lots of raw material. The results for the two methods were in very good agreement, with results ranging from 0.1 to 4.1% (m/m) by HPLC and none detected to 4.3% (m/m) by NMR. The USP method for specific rotation was found to be unsuitable for detecting the presence of low levels of the (R)-enantiomer in (?)-(S)-timolol maleate. © 1994 Wiley-Liss, Inc. 相似文献