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941.
R. Godbout B. L. Gallie R. A. Phillips 《In vitro cellular & developmental biology. Plant》1984,20(6):479-485
Summary A variant nontransformed clone, I21, was selected from the spontaneously transformed mouse fibroblast line, IT22. Selection
was done by plating IT22 in methylcellulose and picking single cells after 2 d. Cultures derived from these single cells were
selected again and one clone, I21, derived from the second round of selection was characterized extensively. I21 and IT22
have the same plating efficiency (PE) on plastic, but in agarose they differ by 1000-fold. In comparison to IT22, I21 has
a normal morphological appearance, a lower saturation density, a higher viability in stationary phase, an increased doubling
time, an increased chromosome content, and is unable to form tumors in nude mice. I21 has remained remarkably stable in culture
and has not reverted to the transformed phenotype for at least 300 generations in culture. Over 100 clones of I21, expanded
to 106 cells, failed to show an increased PE in agarose. Even expansion of the rare colonies of I21 that grow in agarose failed
to produce clones similar to IT22.
The research was supported by the Medical Research Council and the National Cancer Institute of Canada. R. Godbout was supported
by a 1967 Science Scholarship and by an MRC Studentship. B. L. Gallie is a Research Associate of the Ontario Cancer Treatment
and Research Foundation. 相似文献
942.
B. Delhotal F. Lemonnier M. Couturier C. Wolfrom M. Gautier A. Lemonnier 《In vitro cellular & developmental biology. Plant》1984,20(9):699-706
Summary The effect of fructose as a substitute for glucose in cell culture media was investigated in human skin fibroblast and liver
cell cultures. Cells were grown for between 2 and 10 days in identical flasks in four different media, containing 5.5, mmol·1−1 and 27.5 mmol·I−1 glucose and fructose, respectively. In the presence of fructose, cell growth was stimulated, but less in liver cells than
fibroblasts. At Day 6, increases were observed in [3H]thymidine incorporation, protein levels, and amino acid consumption, and a reduction was noted in ATP levels. In media containing
5.5, mmol·1−1 glucose or fructose, consumption of fructose was four times lower than that of glucose at Day 3 and did not rise until Day
6. In fructose media, the lactate production was very low (four to five times less than that of glucose) and the pH values
were always higher. Some findings were different for the fibroblasts and liver cells, owing to the specific characteristics
of these two cell types in culture; this applied especially to the effects of glucose and fructose concentrations of 27.5
mmol·1−1. Several possible explanation for the stimulation of cell growth in fructose medium were discussed.
This work was supported by grants for the Institut National de la Santé et de la Recherche Médicale (ATP 82-79-114) and the
Unité d'Enseignement et de Recherche, Le Kremlin-Bicêtre, Université Paris-Sud (C. R. 848). 相似文献
943.
Sex cell contact in Chlamydomonas is due to complementary sex-specific glycoproteins (mating-type substances, MTSs). Their interaction causes an instantaneous but labile flagella agglutination between sexually different gametes. The dynamic nature of this contact permits partner exchange between agglutinated gametes and accounts for the transitoriness of the contact, flagella adhesion being terminated upon ensuing pairing. This paper describes molecular events that underlie the adhesion potential of differentiated (+) gametes. In the contact-establishing interaction with its receptors on the (?) flagella, the agglutinin of differentiated (+) gametes is inactivated. Compensating for this inactivation, the adhesion potential of gametes in agglutination is sustained by continuous replenishment of the inactivated MTS by newly synthesized units. If this glycoprotein neosynthesis is blocked by tunicamycin (TUM), the adhesiveness of differentiated (+) gametes ceases. It is postulated that this complex interaction with incapacitation and neosynthesis forms the basis of the dynamic nature of the flagella contact and eventually accounts for its termination at pairing. 相似文献
944.
Lun He Kurt J. Isselbacher Jack R. Wands Howard M. Goodman Chiaho Shih Andrea Quaroni 《In vitro cellular & developmental biology. Plant》1984,20(6):493-504
Summary A human hepatocellular carcinoma cell line (FOCUS—Friendship of China and United States) was derived from a patient with primary
hepatocellular carcinoma. This cell line has been in continuous culture over an 18-mo period. The morphological and ultrastructural
features of FOCUS are consistent with its neoplastic hepatocellular orgin. FOCUS cells contain aspartate aminotransferase
and glucose-6-phosphatase activity. In addition, α1-antitrypsin, fibrinogen, alpha fetoprotein, and carcinoembryonic antigens were detectble in the cytoplasm of the cultured
cells by immunochemical staining techniques. The karyotype of the FOCUS cell is human in origin and it contains human DNA
sequences as detected by molecular hybridization analysis. The FOCUS cells do not show evidence of density-dependent inhibition
of growth under confluent conditions. Repeated growth curves over an 18-mo period were identical, revealing a doubling time
of 42 to 48 h. The malignant potential of FOCUS cells was further demonstrated by their ability to lead to gross tumor formation
after subcutaneous infection into nude mice. From one of the solid tumors grown in nude mice, recultured cell lines have been
established and found to have properties identical to the original FOCUS cell line. This FOCUS cell line represents an additional
model for further investigation of tumor specific antigens and the relationship between hepatitis B virus (HBV) and hepatocellular
carcinoma. Preliminary molecular characterization has indicated the existence of integrated HBV sequences within the FOCUS
genome. 相似文献
945.
James S. Clegg 《Cell biochemistry and biophysics》1984,6(3):153-169
Cysts of the crustaceanArtemia are a useful model for studies on intracellular water because they are capable of essentially complete and reversible desiccation.
We have used a variety of techniques on this system, the present work being an attempt to estimate the density of intracellular
water (ρw). The density of individual cysts was evaluated from sedimentation velocity. Heptane displacement methods were used to determine
the volume of a known mass of cysts, from which the density was calculated. The two methods produce comparable results. It
was shown that the densities and water contents of large masses of cysts accurately reflect those of individual cysts. Cyst
densities (ρc) were determined over the entire range of water content from 0 to 0.63 weight fraction of water (W
f), and temperature dependence was measured for 0.61W
f over 2–41°C. The following refer to 25°C. No marked change was detected in ρc until the water content exceeded 0.15W
f, at which ρc decreased as a linear function of Wf to maximum water content. However, the cyst does not behave ideally in the sense that
the densities of the nonaqueous components and added water are not additive as a function ofW
f. The partial specific volume of water in cysts at maximum hydration was estimated to be 3% larger than that of pure water.
These observations are compared with density measurements on other systems, and with previous findings on the physical properties
of water in this system. 相似文献
946.
我们用二相电泳方法在小鼠畸胎瘤系统中发现小鼠胚胎内细胞团标志蛋白双联体(分子量39,000,p14.4—4.5)也存在于未分化的胚胎癌细胞株(PSAI-NG2、F9、PCC3)中,但在已分化细胞株滋养层母细胞癌TDM1中用二相电泳方法不能检查到这蛋白。把EC细胞分为细胞质、细胞核、染色体三部分再进行检查,可以清楚地看到这蛋白主要存在于染色体部分。把染色体再分成0.35M NaCl可溶性,2M NaCl可溶性及2M NaCl不溶性三个组份时,则这蛋白出现在0.35M NaCl可溶性组分中,表明它是与染色体疏松结合的非组蛋白染色体蛋白。这蛋白是一种耐热性蛋白,在80℃受热10分钟不能使它变性。用制备型SDS聚丙烯酰胺凝胶电泳对经热处理的0.36M NaCl可溶性染色体蛋白进行分离,可得到电泳纯的小鼠内细胞团标志蛋白。由于这蛋白约占细胞总蛋白0.6%,与染色体疏松结合,又与早期胚胎细胞的多能性相关,提示它在维持多能细胞染色体构象方面有重要作用。 相似文献
947.
Melinda M. Smith Frances W. Robinson Tomoyuki Watanabe Tetsuro Kono 《生物化学与生物物理学报:生物膜》1984,775(2):121-128
The glucose transport activity solubilized from the basal and plus insulin forms of the Golgi-rich fraction of adipocytes was partially characterized, and the results were compared with those of the activity obtained from the plus insulin form of the plasma membrane-rich fraction. The transport activity was determined in a cell-free, reconstituted, system. Prior to reconstitution, the activities in the three preparations were all (a) stable at 0°C for at least 4 h, but not at 37°C or above; (b) most stable at pH 7–9, and (c) less stable in Tes than in Tris buffer. After reconstitution, the three activities were all (d) stable at 0°C, (e) most active at pH 5.5, (f) mildly stimulated by divalent cations, (g) unaffected by insulin or 1 mM of several SH-blocking agents, (h) inhibited by heavy metal ions, 10–100 mM of monovalent salts, organic solvents, several sugar isomers, and specific sugar-transport inhibitors. The rates of d-glucose uptake by the three liposome preparations were all inhibited more strongly by 2-deoxy-d-glucose or than by d-glucose. These data indicate that the general properties of the glucose transport activity in the Golgi-rich fraction are similar to those of the activity in the plasma membrane-rich fraction. 相似文献
948.
The activity of the neutral, Mg2+-stimulated sphingomyelinase of cultured neuroblastoma cells (N1E-115) is enriched in the plasma membrane fraction and is reduced following treatment of intact or broken cells with trypsin, α-chymotrypsin, papain, and protease. Two protease-sensitive enzymes of the cell interior (lactate dehydrogenase and NADPH-cytochrome c reductase) are not affected by protease treatment of intact cells. These results indicate that the neutral, Mg2+-stimulated sphingomyelinase is oriented externally on the plasma membrane of the cultured neuroblastoma cell. 相似文献
949.
950.
Donald M. Gray Dimitrij Lang Ekkehard Kuner Marilyn Vaughan John Sutherland 《Analytical biochemistry》1984,136(1):247-250
The design of a thin quartz cell suitable for absorption and circular dichroism measurements in the vacuum ultraviolet is described. Important features of the cell are (1) that it can be disassembled for cleaning and reproducibly reassembled with path lengths up to 0.3 mm, and (2) that strain in the windows from the compressed sample can be relieved by a sample overflow port. The latter feature allows the cell to be used for circular dichroism as well as absorption measurements. 相似文献