摘要:

AbstractThe densities of colloidal iron hydroxide (CIH) particles binding to the surfaces of chick embryo fibroblasts were determined before and after transformation with wild type Rous sarcoma virus and a temperature sensitive (ts) mutant of this virus. On the basis of in vitro behavior, cells transformed by the ts virus manifest a malignant phenotype at 36°C (permissive temperature) and appear normal at 41°C (non‐permissive temperature). At the permissive temperatures there is a significant increase in CIH particle‐binding to spaces of cell surface between microvilli on the wild type and ts transformed cells. At the non‐permissive temperature this significant increase in binding is only observed on the wild type transformant, while the density found on the ts transformant is not significantly different from the untransformed state. Therefore, in vitro characteristics of normalcy and malignancy are reflected in changes in the CIH binding properties of the cell surface spaces between microvilli.The CIH densities observed on the microvilli are significantly different from the density on the spaces between them for each of the classes of cells studied at either temperature. The microvilli are found to bind a lower density of particles in five of the six cases. No correlations between microvilli particle density and transformation to in vitro malignant characteristics were o

ISSN:0021-9541    

DOI:10.1002/jcp.1040910302

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1977

数据来源: WILEY

摘要:

AbstractA liquid culture system is described whereby proliferation of haemopoietic stem cells (CFU‐S), production of granulocyte precursor cells (CFU‐C), and extensive granulopoiesis can be maintained in vitro for several months. Such cultures consist of adherent and non‐adherent populations of cells. The adherent population contains phagocytic mononuclear cells, “epithelial” cells, and “giant fat” cells. The latter appear to be particularly important for stem cell maintenance and furthermore there is a strong tendency for maturing granulocytes to selectively cluster in and around areas of “giant fat” cell aggregations. By “feeding” the cultures at weekly intervals, between 10 to 15 “population doublings” of functionally normal CFU‐S regularly occurs. Increased “population doublings” may be obtained by feeding twice weekly. The cultures show initially extensive granulopoiesis followed, in a majority of cases, by an accumulation of blast cells. Eventually both blast cells and granulocytes decline and the cultures contain predominantly phagocytic mononuclear cells.Culturing at 33°C leads to the development of a more profuse growth of adherent cells and these cultures show better maintenance of stem cells and increased cell density.When tested for colony stimulating activity (CSA) the cultures were uniformly negative. Addition of exogenous CSA caused a rapid decline in stem cells, reduced granulopoiesis and an accumulation

ISSN:0021-9541    

DOI:10.1002/jcp.1040910303

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1977

数据来源: WILEY

摘要:

AbstractThe proliferation of 3T3, 3T6 and SV3T3 cells was examined by time lapse cinephotography under a number of different growth conditions. It was found that the frequency distributions of intermitotic times of cells with widely different proliferation rates are qualitatively and quantitatively explained by the transition probability model of the cell cycle (Smith and Martin, 1973). The behaviour of quiescent cells was characterized by very low values of the transition probability. No “out of cycle” or G0compartment of cells was detectable. From a consideration of these results and those in the literature it appears that the rate of cell proliferation is determined by the value of the “transition probability” (P), and that it is the biochemical manifestation of this parameter that regulates cell growth in vitro and

ISSN:0021-9541    

DOI:10.1002/jcp.1040910304

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1977

数据来源: WILEY

摘要:

AbstractResting lymphocytes are in the G0phase of the cell cycle. Upon activation by PHA, they progress into G1with accompanying increased protein and RNA synthesis, initiate DNA synthesis and divide. We have studied the kinetics of inhibition of macromolecular synthesis during activation in the absence of single amino acids. Three types of kinetics are observed. In the absence of tryptophan or isoleucine, stimulated lymphocytes show a normal increase in protein and RNA synthesis during the first 30 hours of stimulation, initiate DNA synthesis but are subsequently inhibited. In phenylalanine‐deficient medium, no DNA synthesis occurs in spite of a slight increase in protein synthesis. No increase in macromolecular synthesis is observed in medium lacking any one of the other essential amino acids (eg: lysine).Our results indicate that the kinetics of macromolecular synthesis in tryptophan‐deficient medium is the result of a limited reserve of protein‐bound tryptophan which becomes exhausted after 30 hours. On the other hand, delayed inhibition of synthesis in isoleucine‐deficient medium probably reflects an initially low requirement for this amino acid followed by inhibition of the synthesis of isoleucine‐rich proteins involved in some late event of stimulation. Partial deprivation of lysine results in kinetics of protein synthesis similar to that in tryptophan‐ or isoleucine‐deficient media. The results indicate that the kinetics of macromolecular synthesis during activation of lymphocytes in the absence of an essential amino acid is a function of the quantitative requirement for that amino acid, at a given time during stimulation.Upon replacement of lysine, lymphocytes inhibited by lysine deficiency begin RNA and protein synthesis immediately and at a rate faster than that of unstimulated cultures to which PHA is added. They also initiate DNA synthesis earlier and therefore, are closer to the S phase than resting lymphocytes. It is concluded that lymphocytes stimulated in the absence of lysine are activated even though no overall increase in macromolecular synthesis is observed. Furthermore, the kinetics of DNA synthesis following reversal of inhibition by phenylalanine suggests that lymphocytes stimulated during phenylalanine deprivation become arrested at most six hours before S. These results indicate that amino acid deficiencies lead to arrest of activated lymphocytes at various stages of stimulation, depending on how stringent these def

ISSN:0021-9541    

DOI:10.1002/jcp.1040910305

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1977

数据来源: WILEY

摘要:

AbstractWe sought a cultured cell line with Proline Oxidase activity to study the regulation and physiologic role of the enzyme in mammalian tissues. Among the cell lines tested, only LLC‐RK1cells, derived from rabbit kidney, had significant Proline Oxidase activity; the Kmfor proline of the enzyme from these cells was similar to that for the liver enzyme. LLC cells, Proline Oxidase positive, were able to convert proline to CO2. In contrast, CHL cells, Proline Oxidase negative, did not have this capability. The presence of Proline Oxidase in LLC cells and the absence of the enzyme in fibroblasts suggest that Proline Oxidase may serve as a marker enzyme for distinguishing parenchymal kidney cells from fibroblasts in culture. Cells transformed by SV40 virus and cells transformed by methylcholanthrene had activities higher than the parent cell line, but this effect of transformation could not be generalized to all transformed cells. Finally, L‐hydroxy proline at 100‐fold greater concentration than substrate L‐proline failed to decrease proline oxidation. This finding suggests distinct degradative enzymes for these two amin

ISSN:0021-9541    

DOI:10.1002/jcp.1040910306

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1977

数据来源: WILEY

摘要:

AbstractThe effects of Fibroblast Growth Factor (FGF) and Epidermal Growth Factor (EGF) on the proliferation of bovine vascular endothelial cells has been examined. FGF induces the initiation of DNA synthesis and cell proliferation in cloned endothelial cells of fetal and adult origin at concentrations as low as 1 ng/ml and is saturating at 50 ng/ml. EGF had no effect over the same range of concentrations. The mitogenic effect of FGF is blocked by a crude extract of cartilage. Platelet extract is also mitogenic for vascular endothelial cells although to a lesser extent than the purified FGF. In contrast to vascular endothelial cells, both EGF and FGF are mitogenic for vascular smooth muscle cells although EGF is less mitogenic than FGF at 100 ng/ml. The mitogenic effect of EGF and FGF on vascular smooth muscle is not blocked by the addition of a crude extract of cartilage, thus demonstrating the specificity of the chalone like effect of cartilage crude extract for endothelial cells.

ISSN:0021-9541    

DOI:10.1002/jcp.1040910307

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1977

数据来源: WILEY

摘要:

AbstractIncubation of primary human fibroblasts in serum‐free medium with small concentrations of thrombin, trypsin or plasmin resulted in manyfold increase in total DNA synthesis and in the number of3H‐thymidine labelled cells. Rise in the frequency of mitoses indicates that the proteases stimulated also cell division. Because proteases induced only a fraction of cells to proliferate increase in the total number of cells remained moderate. Calf, horse and rabbit serum inhibited the growth stimulating effect of trypsin but chicken, dog and monkey serum were permissive. Specific inhibitors of proteases prevented the stimulation of cell proliferation suggesting strongly that proteases act in virtue of their enzymatic activ

ISSN:0021-9541    

DOI:10.1002/jcp.1040910308

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1977

数据来源: WILEY

摘要:

AbstractMinute virus of mice (MVM), a non‐defective parvovirus, has been shown to infect cultures of non‐pluripotent differentiated teratocarcinoma‐derived cells, but pluripotent (and “nullipotent”) embryonal carcinoma cells derived from the same teratocarcinoma resist MVN infection. Somatic cell hybrids between an embryonal carcinoma line and Friend erythroblastic leukemia cells are also resistant to MVM, even though Friend cells are susceptible. Among three blastocyst‐derived lines tested, only one, a parietal yolk sac cell line, resists MVM infection. These results suggest that teratocarcinoma cultures may provide useful systems in which to study the cellular factors which mediate susceptibility to this teratogenic and onco

ISSN:0021-9541    

DOI:10.1002/jcp.1040910309

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1977

数据来源: WILEY

摘要:

AbstractMeasurements made on contraction latencies inSpirostomumsuggest that mechanical stimulation causes contractions to be initiated by the release of small amounts of calcium from a store tightly coupled to the contractile apparatus. Contraction to electrical stimulation appears to result from the gross electrophoretic mobilization of large amounts of calcium from a loosely coupled store. Contraction latencies to mechanical stimulation were three milliseconds and were independent of stimulus strength, previous stimulation, and contraction probability. For 0.5‐millisecond biphasic electrical stimulation the contraction latencies varied widely. Latencies to initial contractions were dependent on stimulus strength: from 1.0 milliseconds for a stimulus that caused a 100% probability of contraction to 2.0 milliseconds for a stimulus that caused a 10% probability of contraction. Latencies of contraction to electrical stimulation were also dependent upon previous stimulation, lengthening to over 300 milliseconds after ten minutes of stimulation. Initial contraction latencies were not affected by previous stimulation to the other (electrical or mechanical) stimulus modality. Repeated electrical stimulation also reduced the animal's resting length and slowed the rate of post contraction re‐extension, whereas mechanical stimulation did not have these effe

ISSN:0021-9541    

DOI:10.1002/jcp.1040910310

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1977

数据来源: WILEY

摘要:

AbstractElectron microprobe analyses of calcium distribution in the ciliated protozoan,Spirostomum ambiguum, indicated several calcium rich sites. One site was an endoplasmic distribution of calcium coincident with phosphorus which corroborates previous findings of hydroxyapatite deposits withinSpirostomum. These apatite deposits were distributed throughout the endoplasm, but not within the nuclei or the contractile vacuole. Calcium was also detected within the cortical region. Cortical calcium was in greater concentration in the anterior portion of the organism and decreased towards the posterior end (region containing the contractile vacuole). Phosphorus and potassium were also detected as gradients from the anterior end, whereas magnesium was detected in the same density throughout the cortical region. Line scans of cortical regions suggested (1) distributions of calcium within mitochondria and/or vesicles, and (2) calcium associated with bundles of microfilaments.

ISSN:0021-9541    

DOI:10.1002/jcp.1040910311

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1977

数据来源: WILEY