摘要:

AbstractAnalysis of the equilibrium of the normal biconcave human red cell, in terms of its tension and a pressure inside, suggests a force of attraction between the opposite membranes at the dimple regions. The analogous attraction that causes rouleaux formation is mediated by long‐chain molecules. Single cells hanging on edge between polarizer and analyser, almost “crossed,” were photographed at different angles to the axis of the polarizer. Enlarged prints were scanned by a photometer. For single cells the records showed non‐significant fluctuations of intensity, but mean values for 32 cells showed a very significant sinusoidal variation with angle, as predicted by theory for birefringence in the cell at the dimple region. For the rim region, the averaged data showed no variation with angle. In cells moderately osmotically swollen, birefringence in the centre of the dimple region was absent, but persisted close to the inside of the membranes. The latter disappeared in cells further swollen to a biconvex shape. The data is interpreted as indicating oriented chains of molecules across the interior of the cell at the dimple region. The behaviour on swelling was what had been seen in a model with nylon fibres oriented between the charged plates of a condenser, in which the variation of attractive force with distance was adequate to explain the equilibrium of the red cell m

ISSN:0021-9541    

DOI:10.1002/jcp.1040740202

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

年代:1969

数据来源: WILEY

摘要:

AbstractFour clonal adrenal tumor cell lines which exhibit biochemical lesions in the ACTH‐stimulated steroidogenic pathway have been isolated. Two of these cell lines, designated Y‐6 and OS3, appear to contain their lesions at points proximal to cyclic AMP formation in the ACTH‐stimulated steroidogenic pathway. Growth of Y‐6 and OS3 as tumors in isogenic mice results in a restoration of ACTH sensitivity in both cell lines by mechanisms which do not appear to involve selection or fulfillment of specific nutritional requirements. Growth of Y‐6 and OS3 as tumors in heterogenic mice results in restoration of ACTH sensitivity in Y‐6 but not in OS3, suggesting that the biochemical lesions in these cell lines are at different loci. Two other cell lines, designated OS1 and OS4, possess biochemical lesions in the steroidogenic pathway beyond the formation of cyclic AMP and before the formation of pregnenolone. Growth of OS1 and OS4 as tumors in isogenic mice results in the repair of the biochemical lesions in these cells distal to cyclic AMP formation in the ACTH‐stimulated steroidogenic pathway. The four cell lines described are potentially useful in elucidating the mechanism of action of ACTH in adrenal cells as well as in determining the factors required for maintaining differentiated function in c

ISSN:0021-9541    

DOI:10.1002/jcp.1040740203

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

年代:1969

数据来源: WILEY

摘要:

AbstractInTetrahymena pyriformis, mating type I, variety 1, cycloheximide rapidly and completely inhibited incorporation of14C‐L‐leucine into protein. Actinomycin D (25 μg per ml) inhibited incorporation of14C‐uracil into cold‐TCA‐insoluble material, after a 5–10 minute lag. Frequently a subsequent decline in the amount of radioactivity was observed. Protein synthesis continued in actinomycintreated cultures for a variable time after cessation of RNA synthesis.Oral development was affected by cycloheximide virtually immediately, and by actinomycin D after a 10–15 minute lag. Cells affected by either drug before the onset of oral membranelle formation were permanently arrested in the stomatogenic field phase. Cells affected in the early and middle stages of membranelle formation completed development of membranelles, but did not invariably complete cell division. Cycloheximide, when added at the beginning of membranelle formation, brought about arrest or resorption of membranelles after they were completed. Actinomycin did not elicit resorption, but sometimes brought about blockage during cell division. Cells affected by either drug after membranelles were fully formed (and cell division was just beginning) completed oral development, nuclear divisions, and cell division. These results suggest that concurrent RNA and protein synthesis are essential for the initiation but not for the completion of membranelle differentiation. The results also suggest that a specific messenger RNA(s) with a very short half‐life is required for the synthesis of proteins involved in the initiation of membranelle

ISSN:0021-9541    

DOI:10.1002/jcp.1040740204

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

年代:1969

数据来源: WILEY

摘要:

AbstractThe effects of cycloheximide on synchronizedTetrahymena pyriformisstrain GL‐C were investigated at concentrations ranging from 0.01 to 10 μg/ml. The initial inhibition of protein synthesis was nearly total (>85%) at 1 μg/ml and above, partial (50–80%) at 0.2 to 0.05 μg/ml, and slight (<30%) at 0.02 μg/ml. Eventual recovery of protein synthesis to a rate approaching that of the controls took place at concentrations of 1 μg/ml and less. When the drug was added before a “transition point” at 55 minutes after the end of the synchronizing treatment (EST), cell division was blocked by 10 μg/ml, and delayed at concentrations of 1 μg/ml or less. The duration of delay was related to the degree of initial inhibition, and to the time required for recovery of protein synthesis; it also depended on the time after EST at which the drug was added. At a given concentration, maximum division delay was observed just prior to the “transition point;” this maximum delay was correlated with resorption of differentiating oral primordia, followed by the appearance of new primordia. The lesser delays observed at earlier times were correlated with temporary blockage of development of primordia in the “stomatogenic field” stage. Resumption of oral primordium development was, in both cases, temporally correlated with a substantial recovery of protein synthesis. After the “transition point,” cell division, and completion of oral development, was delayed slightly at the lower concentrations, and more substantially at 1 and 10 μg/ml, with some division‐arrest at the latter concentration. Except for the recovery phenomenon, the developmental responses elicited by cycloheximide were similar to those observed earlier with puromycin.The bearing of these findings on the mechanism of synchronization inTetrahymenais

ISSN:0021-9541    

DOI:10.1002/jcp.1040740205

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

年代:1969

数据来源: WILEY

摘要:

AbstractGrowth of KB cells was inhibited by both spermine and spermidine, but the inhibition is reduced in conditioned medium. The amount of spermine required for 50% inhibition of plating varied according to the type of serum used with medium 199 (calf, fetal bovine, and horse; 0.55, 0.9, and 24 μg/ml respectively). The spermine oxidase activity of the three sera was calf>horse>fetal bovine, which is not the same ordering as was obtained for the inhibition. When the concentration of sera in the media was varied, the inhibition decreased as calf and fetal bovine sera concentration increased, whereas, with horse serum, an increase in serum concentration increased the inhibition. The opposite effects of increasing concentrations of the sera on the inhibition suggest that at least two factors are involved in the inhibition. A scheme which involves three factors (spermine oxidase, another enzyme and its activator) is postulated to account for the inhibitions and reversals observed. Spermine oxidase alone cannot account for the action of polyamine on cells

ISSN:0021-9541    

DOI:10.1002/jcp.1040740206

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

年代:1969

数据来源: WILEY

摘要:

AbstractH3‐Uridine microinjected in the giant axons of the squid is incorporated in a TCA insoluble material. There is no difference between stimulated and resting axons as to the amount incorporated.The amount incorporated is increased if the stimulation precedes the microinjection of the tracer.RNA was purified and characterized from the axoplasm, axon sheaths and from a purified membrane preparation obtained from squid retinal nerv

ISSN:0021-9541    

DOI:10.1002/jcp.1040740207

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

年代:1969

数据来源: WILEY

摘要:

AbstractL cells were cultivated in test medium which contained 14C‐sodium acetate, and the amount of labeled digitonin‐precipitable sterol was assayed in medium and cells. Increasing concentrations of whole serum in the medium had two effects: depressed cellular synthesis and enhanced release of synthesized sterol from the cells. In experiments with delipidized serum containing unesterified cholesterol, cellular sterol synthesis decreased as free cholesterol concentration in the medium increased. In other experiments using medium containing increasing lecithin concentration and no exogenous sterol, the concentration of lecithin markedly influenced the distribution of synthesized sterol between the cells and the medium which then directly influenced the amount of sterol synthesized. These experiments indicate that cell sterol synthesis is regulated by internal levels of free sterol. This, in turn, is a function of cellular sterol flux which is regulated by the concentration and composition of serum lipoprotein in the med

ISSN:0021-9541    

DOI:10.1002/jcp.1040740208

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

年代:1969

数据来源: WILEY

摘要:

AbstractMouse bone marrow cells in suspension were separated into a number of fractions on the basis of cell density by equilibrium density gradient centrifugation, or on the basis of cell size by velocity sedimentation. After each type of separation, the cells from the various fractions were assayed for their ability to form macroscopic spleen colonies in irradiated recipient mice, and for their ability to form colonies in a cell culture system. The results from either separation technique demonstrate that cells in some fractions formed more coloniesin vivothan in the culture system, while cells in other fractions formed more colonies in culture than in the spleen. The results of control experiments indicate that this separation of the two types of colony‐forming cells was not an artifact of the separation procedures. From these experiments it was concluded that the population of cells which form colonies in culture under the conditions used is not identical to the population of cells detected by the spleen colony assa

ISSN:0021-9541    

DOI:10.1002/jcp.1040740209

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

年代:1969

数据来源: WILEY

摘要:

AbstractRNA in the peripheries of various populations of lymph node cells (LNC) has been evaluated by measuring the electrophoretic mobilities of cells, before and after treatment with active or inactivated ribonucleases. Three different populations of LNC were studied: (1) “resting” normal age control LNC; (2) “syngeneic” LNC from irradiated (C3H × C57BL)F1or C3H mice four to six days following transplantation of syngeneic spleen cells; such cells were progeny of lymphopoietic progenitor cells of the spleen; and (3) “allogeneic” LNC from irradiated (C3H × C57BL)F1mice four to six days after grafting C3H (parental) spleen cells; such cells were progeny of lymphopoietic progenitor cells, but also alloantigen‐sensitive cells of the spleen which proliferate in response to the host's alloantigens (a “graft‐versus‐host” immunological reaction). Whereas the normal LNC had no detectable peripheral RNA, the allogeneic and syngeneic LNC did, i.e., ribonuclease reduced their mean electrophoretic mobilities by 13.6 and 9.2 per cent, respectively. Since both allogeneic and syngeneic LNC had peripheral RNA, no specific correlation could be made with immunological activity.3H‐uridine and14C‐thymidine incorporation into lymph nodes was greatest in allogeneic, intermediate in syngeneic and least in age control lymph nodes, indicating a “population shift” in the spleen cell chimeras toward relatively immature, rapidly proliferating cells, which had a relatively high rate of RNA synthesis. Thus, rapidly proliferating lymphoid cells do have RNA in their peripheries, but its relation to specific immunological fun

ISSN:0021-9541    

DOI:10.1002/jcp.1040740210

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

年代:1969

数据来源: WILEY

摘要:

AbstractDiploid human fibroblasts in culture (WI 38) were allowed to reach a stationary phase and were then stimulated to reenter DNA synthesis and cell division by addition of serum to the culture medium. The rate of protein synthesis increased during the first hours after addition of serum reaching at three hours a plateau value that continued for at least 24 hours after serum addition. Inhibition of protein synthesis during the early hours after serum addition abolished the stimulation of DNA synthesis occurring 20 to 28 hours later.Increased protein synthesis was preceded by a rapid decrease in the intracellular pool size of most amino acids. These changes were independent of concomitant protein synthesis. They suggest that serum exerts an immediate effect on the function of the cell membrane.

ISSN:0021-9541    

DOI:10.1002/jcp.1040740211

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

年代:1969

数据来源: WILEY