摘要:

AbstractAcid phosphatase, alkaline phosphatase, and lactic dehydrogenase activities have been compared in normal human diploid cell strains and in SV40‐transformed heteroploid cell lines derived from them. A higher level of acid phosphatase activity was observed in diploid cultures derived from adult lung than in cultures derived from fetal lung of similar passage levels. The alkaline phosphatase activity of normal diploid fibroblasts was significantly higher than that of SV40‐transformed cell lines derived from them. Generally, the lactic dehydrogenase activities of all these cell cultures were similar.Human diploid cells in culture “age,” in the sense that their ability to proliferate decreases with time during serial subcultivation. Evaluation of the activities of these three enzymes during the “aging” process showed that, although alkaline phosphatase and lactic dehydrogenase activities were similar in “young” and “senescent” cells, acid phosphatase showed a small but significant increase in

ISSN:0021-9541    

DOI:10.1002/jcp.1040690302

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

年代:1967

数据来源: WILEY

摘要:

AbstractBoth two‐wavelength microspectrophotometry of Feulgen‐stained whole nuclei and autoradiography of H3‐thymidine incorporation by giant salivary chromosomes inDrosophila virilisdemonstrate a net decrease in the relative rate of salivary DNA synthesis during the late third instar and prepupal stages of development. Amounts of DNA‐Feulgen per nucleus were distributed into several classes, the means of which closely approximated values projected as geometric multiples of the basic somatic DNA level estimated from hemocyte nuclei of the same larvae. Comparison of DNA polytene class frequencies showed no statistical difference between male larvae of different development stages, although female prepupae showed a greater frequency of nuclei in higher polytene classes when compared to male prepupae of the same age. Comparison of chromosomal H3‐thymidine incorporation with previously described H3‐histidine incorporation suggests that the amino acid labeling, which reaches a maximum during the prepupal period, has a physiological significance distinct from chromosomal endo

ISSN:0021-9541    

DOI:10.1002/jcp.1040690303

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

年代:1967

数据来源: WILEY

摘要:

AbstractRibonuclease was shown to reduce the electrophoretic mobility of a line of cultured mammalian cells (RPMI no. 41), and Ehrlich ascites tumour cells. No reduction was detected in the case of human, mouse or embryonic chick erythrocytes. These data, taken with the various controls, support the hypothesis that RNA is a structural component of the peripheries of two types of cells, but not of erythrocytes from three species.Calcium‐binding was studied in RPMI no. 41 cells, Ehrlich ascites tumour cells, and human and mouse eryhrocytes, by measurement of reduction in cellular electrophoretic mobility in suspending solutions containing various concentrations of calcium chloride. The effect of treating cells with neuraminidase and/or ribonuclease on calcium‐binding was also studied. The results suggest that less calcium binds to the carboxyl groups of peripheral sialic acids than to the phosphates of peripheral, structural RNA. However, calcium apparently binds most avidly to as yet unidentified anionic si

ISSN:0021-9541    

DOI:10.1002/jcp.1040690304

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe light microsomal fraction was isolated from homogenates of rabbit and bullfrog gastric mucosa. On examination with the electron microscope, the light microsomes appear as tubular membranous structures with morphology and dimensions similar to the elements of the smooth‐surfaced endoplasmic reticulum seen in intact oxyntic cells. A K+‐stimulated, Mg++‐requiring p‐nitrophenylphosphatase has been demonstrated in the gastric microsomes. Neither Na+nor ouabain (10−6–10−3M) altered the K+‐stimulated phosphatase. SCN−was not very effective as an inhibitor of the gastric microsomal phosphatase, in contrast to the effect of this anion on the ATPase activity; however, the gastric phosphatase as well as the ATPase are destroyed by phospholipase C, thus showing the lipoprotein nature of these enzymes. Kinetics of the K+activation of the microsomal phosphatase suggest that the K+‐PNPP complex is the active substrate for the enzymic reaction. Rb+, NH4+and Cs+will substitute to some degree for K+as an activator of the microsomal phosphatase. It is pointed out that K+is an essential requirement for HCl secretion in intact gastric mucosa and the replacement of K+with Rb+, Cs+and NH4+is discussed. The K+‐stimulated phosphatase presented in this paper may play a role in th

ISSN:0021-9541    

DOI:10.1002/jcp.1040690305

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

年代:1967

数据来源: WILEY

摘要:

AbstractCultured mammalian cells (RPMI no. 41) in parasynchronous growth were treated, at different stages of the mitotic cycle, with neuraminidase and ribonuclease, separately and sequentially, and their electrophoretic mobilities determined. Changes in the electrophoretic mobility of these cells are probably mainly due to variations in the density of negatively charged groups susceptible to neuraminidase, although variations in groups susceptible to ribonuclease may occur. It is suggested that the observed variations in electrophoretic mobility of different cells may be due to differences in the relative lengths of different life‐cycle phases. Where G2phase is relatively long or G1relatively short the cell populations will hve higher mean electrophoretic mobilitie

ISSN:0021-9541    

DOI:10.1002/jcp.1040690306

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

年代:1967

数据来源: WILEY

摘要:

AbstractSignificantly more calcium per gram protein was found in a relatively pure granule fraction isolated from fresh bovine adrenal medulla than in predominantly mitochondrial fractions isolated from the same tissue. Sixty‐four and 55% of the calcium associated with chromaffin granule and mitochondrial fractions, respectively, was released into the supernatant upon lowering the tonicity of the medium. The per cent calcium released by this procedure was significantly greater for granules than for mitochondria (p<0.05). The amount of calcium per gram protein released into the supernatant also was greater in granule fractions than in mitochondrial fractions (p<0.05). These data, coupled with a previous report that 10−3M EDTA does not markedly decrease the calcium content of whole granules, indicate that the excess calcium of the granule fractions relative to the mitochondrial fractions is maintained within the particles of that fraction. The functional significance of the relatively large amount of calcium in chromaffin granules is not clear.The presence of 150 mM sodium chloride or potassium chloride decreases calcium binding by granule or mitochondrial fragments incubated in 2.2 mM calcium chloride in 0.2 M Tris, pH 7, by about 50%. EDTA, 10−3M, removes all but a small residual of the calcium associated with the granule or mitochondrial fragments whereas lowering the concentration of Tris increases calcium binding to about the same extent in both these subcellular fractions. The calcium‐binding properties of granule and mitochondrial fragments therefore appear to be quantitatively and qualitatively similar. Inhibition of catecholamine release by relatively high concentrations of sodium may be explained by competitive inhibition of calcium binding. Calcium binding by granule fragments decreases with an increase in hydrogen ion concen

ISSN:0021-9541    

DOI:10.1002/jcp.1040690307

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

年代:1967

数据来源: WILEY

摘要:

AbstractThe metabolism of purines and pyrimidines by the ciliated protozoanTetrahymenawas investigated with the use of enzymatic assays and radioactive tracers. A survey of enzymes involved in purine metabolism revealed that the activities of inosine and guanosine phosphorylase (purine nucleoside: orthophosphate ribosyltransferase, E.C. 2.4.2.1) were high, but adenosine phosphorylase activity could not be demonstrated. The apparent Kmfor guanosine in the system catalyzing its phosphorolysis was 4.1 ± 0.6 × 10−3M. Pyrophosphorylase activities for IMP and GMP (GMP: pyrophosphate phosphoribosyltransferase, E.C. 2.4.2.8), AMP (AMP: pyrophosphate phosphoribosyltransferase, E.C. 2.4.2.7), and 6‐mercaptopurine ribonucleotide were also found in this organism; but a number of purine and pyrimidine analogs did not function as substrates for these enzymes. The metabolism of labeled guanine and hypoxanthine by intact cells was consistent with the presence of the phosphorylases and pyrophosphorylases of purine metabolism found by enzymatic studies. Assays for adenosine kinase (ATP: adenosine 5'‐phosphotransferase, E.C. 2.7.1.20) inosine kinase, guanosine kinase, xanthine oxidase (xanthine: O2oxidoreductase, E.C. 1.2.3.2), and GMP reductase (reduced‐NADP: GMP oxidoreductase [deaminating], E.C. 1.6.6.8) were all negative. In pyrimidine metabolism, cytidine‐deoxycytidine deaminase (cytidine aminohydrolase, E.C. 3.5.4.5), thymidine phosphorylase (thymidine: orthophosphate ribosyltransferase, E.C. 2.4.2.4), and uridine‐deoxyuridine phosphorylase (uridine: orthophosphate ribosyltransferase, E.C. 2.4.2.3) were active; but cytidine kinase, uridine kinase (ATP: uridine 5'‐phosphotransferase, E.C. 2.7.1.48), and CMP pyrophosphorylase could not

ISSN:0021-9541    

DOI:10.1002/jcp.1040690308

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

年代:1967

数据来源: WILEY

摘要:

AbstractHeLa cells in monolayer cultures were treated with the following inhibitors of DNA synthesis: mitomycin C, nitrogen mustard, fluorodeoxyuridine, hydroxyurea, arabinofuranosylcytosine and high concentrations of thymidine. The concentration of each inhibitor used was, in most cases, just sufficient to arrest cell multiplication and all produced unbalanced growth in the sense that the synthesis of RNA and protein were only partially inhibited while DNA synthesis stopped. This resulted in approximately 100% increases in RNA and protein content per cell in 48 hours and, since cell volume also increased by 100% during this time, the concentration of RNA and protein per unit cell volume remained constant. It was concluded that cell protein content may be used as an accurate index of variation in cell size in HeLa cells treated with inhibitors of DNA synthesis.

ISSN:0021-9541    

DOI:10.1002/jcp.1040690309

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

年代:1967

数据来源: WILEY

摘要:

AbstractAttempts to synchronize the BHK21 hamster cell C‐13 and its polyoma‐transformed derivative P‐183 with excess thymidine resulted in the observation that the parent cell line could be readily synchronized but the transformed derivative could not. Differences in the growth pattern indicate that excess thymidine (10 mM) stops progress of the virus‐transformed derivative at all stages in the life cycle rather than exclusively in S. The data are suggestive but do not establish that the difference is a result of the presence of the virus

ISSN:0021-9541    

DOI:10.1002/jcp.1040690310

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

年代:1967

数据来源: WILEY

摘要:

AbstractChinese hamster fibroblasts in monolayer cultures were synchronized by accumulating mitotic cells in the presence of Colcemid, removing the mitotic cells with a brief trypsin treatment, and growing them in medium lacking Colcemid. Such cultures grew normally and exhibited no significant deviations from control cultures in their mitotic interval, generation time, DNA synthesis kinetics, or proliferative capacity.The macromolecular composition of 106mitotic cells was chemically determined to be: DNA, 15 μg; RNA, 28 μg; and protein, 190 μg. In stock cultures, the corresponding values were about 60% to 70% of those for mitotic cells.The kinetics of DNA, RNA, and protein synthesis were measured throughout a 12‐hour cell cycle by incorporation of tritiated precursors. DNA synthesis began two hours after, and continued until ten hours after Colcemid recovery, with 40 minute interruptions at five and eight hours. RNA synthesis commenced at one hour and continued linearly until the fifth hour, at which time the rate abruptly doubled. Protein synthesis began immediately after cell division (0.5 hour) and continued linearly until the sixth hour, at which time its rate also doubled.The simplest interpretation of the data suggests that most of the DNA involved in transcription was replicated in the first third of the DNA synthesis period. Thereafter, the rates of RNA and protein synthesis increased because of the doubling of the active template population in each

ISSN:0021-9541    

DOI:10.1002/jcp.1040690311

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

年代:1967

数据来源: WILEY