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21.
William D. Meek Walter L. Davis 《In vitro cellular & developmental biology. Plant》1986,22(12):725-737
Summary The potent fungal metabolite cytochalasin D (CD) and cationized ferritin (CF) are used in combination to test for negative
charge distribution on blebs (knobs). Two established human epithelial cell lines, WISH and HeLa, that display blebs in various
phases of the cell cycle or under certain culture conditions (37,46) are investigated. CD alone, applied at a low concentration
(1.0 μg/ml) and for a short time period (3 min), causes blebs to appear as the prevalent surface feature. These are filled
mainly with free ribosomes. Additionally, feltlike mats, presumed to be disorganized, compacted microfilaments, are formed
directly beneath the cell membrane. These are especially evident in the cortical cytoplasm below the blebs or bleb clusters.
CF (0.345 mg/ml), applied for a 5-min period after CD administration (1.0 μg/ml) for 3 min, appears along the surface of microvilli,
at the base of blebs, and in vesicles beneath the bleb clusters. In some cases, microfilaments (6 nm in diameter) are closely
related to the vesicles. CF does not preferentially bind to the apical cell membrane of blebs. Above areas of the subplasmalemmal
microfilaments, CF membrane binding is apparent, even under circumstances where the filaments are disorganized by cytochalasin
treatment. These results seem to show the following: (a) bleb membranes are different from the remainder of the cell and do
exhibit a loss of negative charge and (b) surface charge may be dependent on the presence or structural integrity of membrane-related
6-nm microfilaments.
The support of this research by a grant from the Baylor College of Dentistry and The Oklahoma College of Osteopathic Medicine
and Surgery is gratefully acknowledged. The assistance of Dr. J. H. Martin, Department of Pathology, Baylor University Medical
Center, is also greatly appreciated. 相似文献
22.
R E Gibson W J Rzeszotarski E M Jagoda B E Francis R C Reba W C Eckelman 《Life sciences》1984,34(23):2287-2296
We have prepared a radioiodinated ligand which binds with high affinity to the muscarinic acetylcholine receptor (m-AChR). A derivative of 3-quinuclidinyl benzilate, [125I] labeled (R) 1-aza-bicyclo(2.2.2)oct-3-yl (R,S)-alpha-hydroxy-alpha-(4-[125I]iodophenyl)phenyl acetate (4- IQNB ) exhibits an affinity for the m-AChR from corpus striatum higher than that of (R) [3H] QNB. Additionally, [125I] 4- IQNB exhibits receptor selectivity for the M1 receptor since the affinity for the receptor from dog and rat heart is lower than that using dog or rat corpus striatum. 相似文献
23.
Three experiments demonstrate that inescapable footshock delivered to unrestrained rats produces analgesia as well as performance deficits in subsequent one-way shuttle acquisition. Both the performance and the antinociceptive effects are prevented by pretreatment with as little as 0.1 mg/kg i.p. of the opiate antagonist, naltrexone. These studies suggest that both effects are mediated through opiate receptors with similar underlying naltrexone pharmacodynamics. 相似文献
24.
Shyamali Mukherjee Mihir Nag Tultul Nayyar Indrani Maitra Parul Chakrabarti Pramod R. Dasgupta 《Journal of biosciences》1986,10(3):311-317
The effect of estradiol-17β and progesterone given separately as well as in combination on the rate of hydrogen peroxide formation
and lipid peroxidation in the uteri of ovariectomized rats was studied. Estradiol in 3μg dose per day per animal elicited maximum stimulatory response and progesterone (100μg), on the other hand, was without any such effect. However, progesterone given along with estradiol completely prevented the
effect due to the latter. In the same way, vitamin E, a well known antioxidant was found to be extremelv effective in protecting
the uterus from the highly peroxidative action of estradiol-17β. 相似文献
25.
Biochemical significance of enhanced activity of fluorinated 1,25-dihydroxyvitamin D3 in human cultured cell lines 总被引:1,自引:0,他引:1
Several human cancer cells possess receptors for 1,25-dihydroxyvitamin D3[1,25-(OH)2D3]. In these cells 1,25-(OH)2D3 has a biphasic concentration-dependent regulatory effect on cell replication and specifically induces its own metabolism. We have studied the effects on these parameters of the native hormone together with those of two analogues fluorinated at the 24-carbon and of 1,24R,25-trihydroxyvitamin D3[1,24R,25-(OH)3D3]. The difluorinated analogue 24,24-difluoro-1,25-(OH)2D3[24,24-F2-1,25-(OH)2D3] is an approximately fivefold more potent inhibitor of cellular replication than the native hormone, while 1,24R,25-(OH)3D3 is about fivefold less potent. This enhanced potency of the fluorinated analogue parallels its enhanced potency in in vivo studies of its effects on calcium and mineral metabolism. However, although the analogue retains replication stimulatory activity, it is clearly no more potent than the native hormone in this activity: 1,24R,25-(OH)3D3 has no significant stimulatory activity. Exposure of the cells to 1,25-(OH)2D3 at 0.05 nM for 6 h increases the subsequent conversion of labelled hormone to aqueous phase soluble compounds by 6.7-fold. None of the other compounds had a similar effect at this concentration. At 10 nM all 1-hydroxylated compounds increased aqueous phase radioactivity about equally (13 to 17-fold); this effect is still specific since 25-OH D3 had no such effect even at 10 nM. Studies on the effects of the fluorinated analogues upon receptor binding of hormone in cell cytosols and uptake of hormone by intact cells clearly demonstrate that the enhanced activity of these analogues is not due to higher receptor affinity or more rapid access to intracellular receptor.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
26.
Gideon Bach Elizabeth F. Neufeld 《Biochemical and biophysical research communications》1983,112(1):198-205
The biosynthesis of arylsulfatase A was studied in cultured fibroblasts by pulse-chase labeling with [2-3H]mannose; the enzyme was isolated by immunoprecipitation and denaturing polyacrylamide gel electrophoresis. In normal fibroblasts, and in fibroblasts from a patient with multiple sulfatase deficiency, the enzyme was synthesized as a glycoprotein of apparent molecular weight of 59,000; half of it was processed over a period of 4 days to Mr= 57,000. The precursor chain of Mr= 59,000 was secreted in the presence of 10 mM NH4Cl. An immunoprecipitable glycoprotein of normal size was synthesized by fibroblasts from two unrelated patients with metachromatic leukodystrophy, but this material disappeared within twenty hours. In fibroblasts from an individual with pseudodeficiency of arylsulfatase A, the immunoprecipitable precursor glycoprotein was smaller (Mr= 56,000). The synthesis of cross-reactive proteins with altered properties supports the concept of allelic mutations as the genetic basis of metachromatic leukodystrophy and of arylsulfatase A pseudodeficiency. 相似文献
27.
Marion T. Hierowski 《FEBS letters》1983,154(1):92-96
Quantitative analyses of LH-RH-like membrane receptors were performed in five tumors from the transplantable Dunning R3372H rat prostatic adenocarcinoma. The binding of D-Trp6-LH-RH, an agonist of LH-RH, was observed in all 5 tumors. The antagonist [Ac-Dp-Cl-Phe1,2,D-Trp3,D-Lys6,D-Ala10]-LH-RH was bound to 4 tumors. The apparent equilibrium dissociation constant (Kd) for D-Trp6-LH-RH receptor was from 2.6–3.9 × 10?10 M. The apparent equilibrium Bmax values (maximum number of binding sites) were from 17.2–86.0 fmol/mg membrane protein for D-Trp6-LH-RH receptor. The Kd for the antagonist was from 2.4–2.7 × 10?10 M and the Bmax values were from 35.5–66.0 fmol/mg membrane protein. Similar binding studies performed in 6 normal rat prostates showed no binding capacities. 相似文献
28.
M Suda K Nakao T Yoshimasa Y Ikeda M Sakamoto N Yanaihara S Numa H Imura 《Life sciences》1983,32(24):2769-2775
The primary structure of the common precursor of porcine beta-neo-endorphin and dynorphin (preproenkephalin B) has shown the existence of a third leucine-enkephalin (leu-enkephalin) sequence with a C-terminal extension of 24 amino acids. This nonacosapeptide, named leumorphin, was approximately 70 times more potent than leu-enkephalin in inhibiting the contraction of the myenteric plexus-longitudinal muscle preparation of the guinea pig ileum. This action of leumorphin, like those of beta-neo-endorphin and dynorphin, was antagonized less effectively by naloxone than that of leu-enkephalin, but more effectively by Mr2266, an antagonist relatively specific for the kappa type opiate receptor. The inhibitory action of leumorphin or beta-neo-endorphin on the contraction of the guinea pig ileum muscle strip was reduced in a dose-dependent manner by pretreatment with dynorphin and vice versa. Leumorphin as well as beta-neo-endorphin and dynorphin inhibits the contraction of the rabbit vas deferens which is known to have only the kappa type opiate receptor. This action was also effectively antagonized by Mr2266. It is concluded that leumorphin has potent opioid activity and acts at the kappa receptor, like other opioid peptides derived from preproenkephalin B. 相似文献
29.
E. K. Sadanandan Nambiar 《Plant and Soil》1983,71(1-3):37-47
Summary In south-east Australia, where radiata pine (Pinus radiata D. Don) is grown on sandy soils low in nutrients and short of water, early establishment, and rapid growth to canopy closure lead to increased productivity. At this stage demands for nutrients and water are high, and trees respond vigorously to silvicultural inputs.For several months after transplanting in winter roots are confined within a narrow planting wedge, low temperature restricts new root growth and slows recovery from water stress in plants. From spring, depending upon the configuration and vigour of the roots transplanted, lateral roots extend radially throughout the soil.Although there were small decreases in concentration of roots radially from the stems of very young trees, such spatial differences disappeared between ages 2 and 3, so that rooting density was independent of distance from the stem. The pattern of vertical distribution of lateral roots was not influenced by age and 80–90% of the lateral roots were within the top 30 cm soil. Roots developed rapidly as the trees grew towards canopy closure, but in general the rooting densities of these pines are among the lowest reported for plants. In rapidly growing trees approaching canopy closure, the secondary thickening of the lateral roots was sufficient to double the weight of roots without altering root length.Knowledge about root growth and root configuration during the early phase of plantation development will assist management decisions where intensive silviculture is practiced, and hence ensure the most efficient use of nutrients and water. 相似文献
30.
Characterisation of human N-acetyl-beta-hexosaminidase C 总被引:7,自引:0,他引:7
I Braidman M Carroll N Dance D Robinson L Poenaru A Weber J C Dreyfus B Overdijk G J Hooghwinkel 《FEBS letters》1974,41(2):181-184