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151.
Immunotargeting of daunomycin to localized and metastatic human colon adenocarcinoma in athymic mice
Esther Hurwitz Ruth Adler Daniel Shouval Hiroshi Takahashi Jack R. Wands Michael Sela 《Cancer immunology, immunotherapy : CII》1992,35(3):186-192
Summary A monoclonal antibody (designated SF25), which recognizes a protein antigen expressed on a large number of human colon carcinomas, was used for drug targeting. Daunomycin-antibody conjugates were prepared by two previously described procedures. In one, the drug was bound to the antibody through a spacer of small molecular mass (cis-aconitic acid), while in the other a dextran bridge served as the link between drug and antibody. High substitution rates of drug to antibody were obtained using the latter binding procedure. Both conjugates were tested in vitro against two human colon carcinoma cell lines, LS180 and KM-12. The efficacy of a daunomycin-dextran-SF25 antibody conjugate was tested against colon carcinoma LS180 tumors transplanted at different sites into athymic mice. The specific conjugate was significantly more inhibitory to a subcutaneous tumor growth than its components or their mixture. SF25 antibody alone showed antitumoral effects against all three forms of transplanted tumor tested, namely, local, metastatic or intrahepatic, whereas daunomycin, on its own, was effective only against the subcutaneous tumor. Binding of daunomycin to dextran partially improved its inhibitory activity against the metastatic tumor. The conjugate, daunomycin-dextran-SF25 antibody reduced the number of metastatic foci, increased the survival rate and delayed death. Yet against lymph node metastases it was not significantly better than a mixture of both constituents. However, results obtained with an intrahepatic tumor, a model that mimics the natural progression of the disease, resembled those described with the subcutaneous tumor. Daunomycin-dextran-SF25 antibody was significantly more effective than all components separately and than a mixture of drug and antibody, provided a highly drug-substituted conjugate was used. 相似文献
152.
Stefan Jansson Eran Pichersky Roberto Bassi Beverley R. Green Masahiko Ikeuchi Anastasios Melis David J. Simpson Michael Spangfort L. Andrew Staehelin J. Philip Thornber 《Plant Molecular Biology Reporter》1992,10(3):242-253
We propose a nomenclature for the genes encoding the chlorophylla/b-binding proteins of the light-harvesting complexes of photosystem I and II. The genes encoding LHC I and LHC II polypeptides
are namedLhca1 throughLhca4 andLhcb1 throughLhcb6, respectively. The proposal follows the general format recommended by the Commision on Plant Gene Nomenclature. We also present
a table for the conversion of old gene names to the new nomenclature. 相似文献
153.
The large family of signal transducing proteins known as G proteins are heterotrimers that dissociate into an independent α-subunit and βγ-subunit complex after ligand binding or other stimulation. For Gα, at least 30 distinct sequences representing 10 different classes have been identified. On the other hand, cDNAs for only three Gβ-subunit genes have been isolated so far. All three of the Gβ genes have been chromosomally mapped in the human, but only two in the mouse. Using a human retinal cDNA for the third G protein β-subunit, we have mapped the corresponding gene, termed Gnb-3, to mouse Chromosome 6 with somatic cell hybrids and have positioned it distal to but near the marker Raf-1 by analysis of the progeny of three genetic crosses. 相似文献
154.
Contribution of organic acids to the acidification of the rhizosphere of maize seedlings 总被引:3,自引:0,他引:3
The participation of organic acids in the process of soil acidification was related to other H+ pumping processes. The ratio between efflux of organic acids and proton secretion of maize roots was determined with the
use of a pH-stat combined with a collecting system for organic acids. Changes in the composition of carboxylic acids influenced
by nitrogen supply were monitored by HPLC and via enzymatic conversion. The following substances were found to be secreted
by maize roots: glycolate, glyoxylate, fumarate, 2-oxoglutarate and oxalate. Malate, however, could not be detected.
There is no organic acid dominantly secreted by the roots, but changes are observed during aging which might result from deficiencies
of nutrients e.g. P.
Fertilization of N-deficient plants with urea leads to a significant change in the composition of acids secreted. In this
case, oxalate was additionally detected with a concomitant increase in glyoxylate, indicating important changes in metabolism.
Acidification of the rhizosphere is predominantly maintained by secretion of protons, not by efflux of organic acids, which
contributed 0.2 to 0.3% to this process only. The role of organic acids in nutrient uptake is discussed. 相似文献
155.
Internal seiches in Lake Constance: influence on plankton abundance at a fixed sampling site 总被引:1,自引:0,他引:1
During thermal stratification, pronounced internal seiches occurin Lake Constance with periods of 46 days The amplitudesreach 12 m at the sampling site in berlinger See (northwesternpart of Lake Constance). Seiches change the thickness of thewarm and generally biologically rich epilimnion and, thus, alsothe areal abundance of planktonic organisms at a fixed samplingsite. The potential impact of seiche-dnven changes of epilimneticthickness on observed plankton abundance was calculated usingcontinuously recorded temperature profiles and weekly verticalprofiles of plankton biomass. Observed plankton biomass wasrecalculated by taking into account the effect of changing layerthickness in order to give a more realistic picture of biomasschanges caused by waxing and waning of populations Our calculationsimply that changes of strata thickness do not mask the generalseasonal trend in population dynamics (e g. spring bloom andclear water phase), estimates of average yearly standing stockare not significantly affected if sampling is done at leastweekly. However, changes of strata thickness can alter arealplankton abundance at the sampling site by a factor of 2 within2 days During pronounced seiches, areal abundance of phytoplankton,which generally exhibit a stronger vertical gradient than-mostother plankton, may be changed by a factor of 34 withinhours Hence, at our sampling site, the impact of changes instrata thickness cannot be ignored for detailed analysis ofpopulation dynamics of autotrophs involving comparisons betweensingle observations 相似文献
156.
Michael J. MacDonald 《Bioscience reports》1991,11(3):165-170
Coenzyme Q (CoQ0) and other quinones were shown to be potent insulin secretagogues in the isolated pancreatic islet. The order of potency was CoQ0benzoquinonehydroquinonemenadione. CoQ6 and CoQ10 (ubiquinone), duroquinone and durohydroquinone did not stimulate insulin release. CoQ0's insulinotropism was enhanced in calcium-free medium and CoQ0 appeared to stimulate only the second phase of insulin release. CoQ0 inhibited inositol mono-, bis- and trisphosphate formation. Inhibitors of mitochondrial respiration (rotenone, antimycin A, FCCP and cyanide) and the calcium channel blocker verapamil, did not inhibit CoQ0-induced insulin release. Dicumarol, an inhibitor of quinone reductase, did not inhibit CoQ0-induced insulin release, but it did inhibit glucose-induced insulin release suggesting that the enzyme and quinones play a role in glucose-induced insulin release. Quinones may stimulate insulin release by mimicking physiologically-occuring quinones, such as CoQ10, by acting on the plasma membrane or in the cytosol. Exogenous quinones may bypass the quinone reductase reaction, as well as many reactions important for exocytosis. 相似文献
157.
In an attempt to find mild virus strains that would cross-protect sgainst vanilla necrosis potyvirus (VNPV), Vanilla fragrans plants in Tonga were surveyed for the presence of mild or symptomless potyvirus infections. Potyviruses were detected by indirect ELISA using a commercially available portyvirus group monoclonal anibody. From 28 plants with mild or symptomless infections two portyvirus isolates, designated V1 and V3, included systemic infections in Nicotiana benthamiana following mechanical inoculation. V1, which causes a mild mottle in N. benthamiana, is serologically related to VNPV, while V3 which causes mild vein banding is serologically unrelated to VNPV. Prior inoculation with V1 protected N. benthamiana against the severe mosaic symptoms of VNPV when challenge inoculated after 14 and 21 days, but not after 7 days. When V3 was used as the protecting strain, cross-protection was observed in some, but not all plants, when chalenged with VNPV after 14 and 21 days. 相似文献
158.
Summary We have devised techniques to culture whole, dissected embryos of Drosophila melanogaster. We examine multiple aspects of the morphological and physiological development of the epidermis, musculature, nervous system, and internal organs in this cultured preparation, and show that in vitro development closely parallels normal embryogenesis. These techniques permit a wide range of experimental manipulations during embryogenesis and allow us to extend observations through late embryonic stages, after cuticle deposition. Applications of this technique are presented. 相似文献
159.
Ming Shiang James C. Linden Ali Mohagheghi Karel Grohmann Michael E. Himmel 《Applied microbiology and biotechnology》1991,34(5):591-597
Summary Fed-batch fermentations of Acidothermus cellulolyticus utilizing mixtures of cellulose and sugars were investigated for potential improvements in cellulase enzyme production. In these fermentations, we combined cellulose from several sources with various simple sugars at selected concentrations. The best source of cellulose for cellulase production was found to be ball-milled Solka Floc at 15 g/l. Fed-batch fermentations with cellobiose and Solka Floc increased cell mass only slightly, but succeeded in significantly enhancing cellulase synthesis compared to batch conditions. Maximum cellulase activities obtained from fermentations initiated with 2.5 g cellobiose/l and 15 g Solka Floc/l were 0.187 units (U)/ml, achieved by continuous feeding to maintain <0.1 g cellobiose/l, and 0.215 U/ml using the same initial medium when 2.5 g cellobiose/l was step-fed after the sugar was nearly consumed. In batch, dual-substrate systems consisting of simple sugars with Solka Floc, substrate inhibition was evident in terms of specific growth rates, specific productivity values, and maximum enzyme yields. Limiting concentrations of glucose or sucrose at 5 g/l, and cellobiose at 2.5 g/l, in the presence of Solka Floc, yielded cellulase activities of 0.134, 0.159, and 0.164 U/ml, respectively.
Offprint requests to: M. E. Himmel 相似文献
160.
Karnam R. Purushotham Tivadar Zelles Michael G. Humphreys-Beher 《Molecular and cellular biochemistry》1991,102(1):19-33
The involvement of protein phosphorylation in isoproterenol (ISO)-mediated proliferation in the rat parotid gland was investigated by labeling the cells with [32P] orthophosphate. An increased (4–6 fold) incorporation of the radiolabel was noted in the total parotid gland homogenates of ISO-treated animals when compared to controls. Plasma membrane, nuclear membrane and cytoplasm were isolated, the proteins separated by SDS/PAGE and the phosphoproteins detected by autoradiography. Two phosphoproteins with apparent Mr of 45 and 170 kDa were identified in the cytoplasm while the 170 kDa phosphoprotein also appeared as part of plasma membrane. Transfer of these proteins to nitrocellulose followed by Western blot detection with an antiphosphotyrosine monoclonal antibody showed reactivity with the 170 kDa region of the plasma membrane and cytoplasm. Separate in vitro studies involving incubations of rat parotid slices with 0.2 mM ISO and [3H] myo-inositol for 1 min induced inositol phosphate hydrolysis resulting in a significant increase in inositol-bis and -tris phosphate production. Inositol phosphate production can be blocked by pre-incubation with a mixed -adrenergic receptor antagonist but not with physiological concentrations of - or 1-specific adrenergic receptor antagonists, indicating the ISO effects are mediated through the 2-adrenergic receptors. The inclusion of calmodulin antagonists along with ISO prevented the expression of cell-surface galactosyltransferase and retarded gland hypertrophy and hyperplasia. These results suggest that ISO treatment leads to the phosphorylation of target proteins which may be involved in signal transduction pathways leading to cell proliferation.Abbreviations InsP1, InsP2, InSP3
inositol mono-, bis-, and tris-phosphates
- UDP
Uridine diphosphate
- PMSF
phenylmethylsulfonylfluoride
- SDS
sodium dodecyl sulfate
- TFP
Trifluoperazine
- P-tyr
phosphotyrosine
- Gal Tase
galactosyltransferase 相似文献