摘要:

AbstractThe levels of carbohydrates were measured in cells before and after transformation with DNA and RNA‐containing oncogenic virus. The most consistent finding was a markedly lower content of L‐fucose in all transformed cells relative to their normal counterpart. The cell pellet from a line of Chinese hamster cells transformed with polyoma or SV‐40 viruses showed a marked decrease in the level of carbohydrates. However, when the carbohydrate levels were calculated for the whole system (cells plus wash) the transformed cells except for L‐fucose had almost the same amount of carbohydrate as the controls. The levels of various carbohydrates in cells transformed by Rous sarcoma virus were the same or were elevated above the controls. Here consideration of the washes did not alter the results. Possible explanations for the results and causes of error in these comparative studies are di

ISSN:0021-9541    

DOI:10.1002/jcp.1040800202

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

年代:1972

数据来源: WILEY

摘要:

AbstractDensity dependent inhibition of cell replication is released in stationary cultures of BALB/c‐3T3 fibroblasts by the potent tumor promoter for mouse skin, phorbol myristate acetate (PMA). The saturation density of these cultures, which is dependent on the serum concentration of the medium, is increased by PMA. Cell division, which can be induced by PMA or serum in stationary monolayers of BALB/c‐3T3 cells, is not blocked by several inhibitors of proteolytic enzymes or the plant lectins, concanavalin A or wheat germ agglutinin. Induction of cell replication by PMA or serum does not appear to be dependent on proteolytic activity, and the membrane sites associated with this induction appear to be distinct from the agglutinin‐binding

ISSN:0021-9541    

DOI:10.1002/jcp.1040800203

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

年代:1972

数据来源: WILEY

摘要:

AbstractIncubation of rat liver parenchymal cell suspensions at 37° results in degradation, to acid‐soluble material, of 15% of cellular RNA at 30 minutes and 40% at three hours, beyond which there is little, if any, further degradation. The RNA which remains in the acid‐insoluble form in the cells up to 30 minutes appears to exist largely in the native state. However, after 30 minutes, the acidinsoluble RNA of the cells is found to be partially depolym‐erised. These observations suggest the activation of an intracellular nuclease on dispersion of the liver tissue to a single cell suspension and incubation at 37°. This nuclease appears to be responsible also for the degradation, reported earlier, of exogenous RNA taken up by the cells. Activation of the nuclease is not due to depletion of pool of ATP or of other ribonucleotides from the cells, during either dispersion of the tissue or incubation at 37°. Incubation of the cells at 28°, or of liver slices at 37°, does not lead to any significant degradation to acid‐soluble material, or to partial depolymerisation, of RNA. Analysis of RNA obtained from cells incubated at 37° for various periods showed that chromatography on methylated albumin‐kiesulguhr (MAK) and Sephadex columns is not suitable for detecting partial depolymerisation of cellular RNA; RNA shown to be partially depolymerised by analysis on sucrose density gradient, in an analytical ultracentrifuge, and on a cellulose column, gave the normal pattern in MAK o

ISSN:0021-9541    

DOI:10.1002/jcp.1040800204

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe response of unfertilized sea urchin eggs stimulated with continuous D.C. was studied using cinematographic techniques. As reported by previous workers, the initiation of the response was anodal in polarity and followed a typical strength‐duration curve. However, the anodal response may be swelling and/or contraction, depending on the amplitude of the applied stimulus, i.e., the magnitude of the contraction is directly related to the applied stimulus and is a graded response. It is suggested that the phenomena of anodal swelling and anodal contraction represent a continuum of responses based on ion exchang

ISSN:0021-9541    

DOI:10.1002/jcp.1040800205

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

年代:1972

数据来源: WILEY

摘要:

AbstractHemopoietic colony formation in agar occurred spontaneously in mass cultures of marrow cells obtained from a number of species (guinea pig, rat, lamb, rabbit, pig, calf, human and Rhesus monkey). This contrasted with the observation that colony formation by mouse bone marrow exhibited an absolute requirement for an exogenous source of a colony stimulating factor. Analysis of spontaneous colony formation in Rhesus monkey marrow cultures revealed the presence of a cell type in hemopoietic tissue, capable of elaborating colony stimulating factor when used to condition media or as feeder layers. Equilibrium density gradient centrifugation separated colony stimulating cells fromin vitrocolony forming cells in monkey bone marrow. Separation studies on spleen, blood and marrow characterized the stimulating cells as of intermediate density, depleted or absent in fractions enriched for cells of the granulocytic series and localized in regions containing lymphocytes and monocytes. Adherence column separation of peripheral blood leukocytes showed the stimulating cells to be actively adherent, unlike the majority of lymphocytes, and combined adherence column and density separation indicated that stimulating cells were present in hemopoietic tissue within the population of adherent lymphocytes or monocytes.

ISSN:0021-9541    

DOI:10.1002/jcp.1040800206

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe electrical response of the taste cells of the frog fungiform papillae to four fundamental taste solutions (NaCl, acetic acid, quinine‐HCl and sucrose) was studied by using the intracellular recording technique. The average value of resting membrane potential was 22.5 mV, inside negative. Each of the four taste solutions applied to the tongue produced a slow depolarizing potential, the receptor potential, on which no spike potential was superimposed. The amplitude of the receptor potentials increased linearly as a function of the logarithm of the concentration of the stimulus. Amplitudes of depolarizations to a given taste stimulation varied from one cell to another even within a single taste bud. Most of the cells responded to more than two of the four basic taste solutions. Sensitivity patterns in terms of the number of effective solutions and the relative effectiveness of different kinds of solutions were variable among cells. Statistical analysis suggests that at the receptor membranes of the taste cells, the sensitivities for the four basic stimuli are independent and rando

ISSN:0021-9541    

DOI:10.1002/jcp.1040800207

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

年代:1972

数据来源: WILEY

摘要:

AbstractCalcium‐influx associated with the action potential was studied in squid giant axons using an EDTA‐free preparation of aequorin as a probe. Associated with an individual action potential there was a transient increase in aequorin luminescence and the time course of this increase was examined on a kinetic basis. The luminescent response associated with a train of action potentials was compared with that expected on the basis of superposition of individual responses. The analyses of luminescence curves produced by long trains of action potentials were complicated by failure of superposition. A long pulse of inward current was found to produce a very large enhancement of luminesce

ISSN:0021-9541    

DOI:10.1002/jcp.1040800208

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

年代:1972

数据来源: WILEY

摘要:

AbstractActivities of two membrane associated enzymes, viz. 5′‐nucleo‐tidase (EC 3.1.3.5) and alkaline phosphatase (EC 3.1.3.1) are known to be altered by glucocorticoid treatment of cells in culture. In certain HeLa cell lines, their activity is elevated, while in others, it is decreased. In order to confirm the data obtained previously with cell homogenates, cells were fractionated essentially as described by Bosmann, Hagopian and Eylar ('68) after 96 hours exposure to 0.5 μg/ml prednisolone. This treatment resulted in changes both in the specific activity and in the distribution of the two enzymes among the isolated membrane fractions. The alterations in specific activity in the individual membrane fractions reflected changes previously observed in preparations from whole cells. A shift in distribution of total enzymatic activity to fractions of higher density occurred in both cell lines in response to the steroid. These results may be indicative of cellular membrane alterations as a consequence of steroid tre

ISSN:0021-9541    

DOI:10.1002/jcp.1040800209

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe study of the cytological evolution of the foetal thymus enables us to distinguish an early foetal period (up to 20 weeks) from a late foetal period. The cytological maturation is achieved at 20 weeks of gestation. The thymus in the late foetal phase is comparable to that of the child.The study of the lymphopoietic function shows a higher activity in the foetal thymus up to 20–22 weeks, lymphopoiesis is also slightly increased, in the thymus of the child up to the age of three years. The study of the contribution of the various cell types to the cellularity of the thymus, emphasizes the importance of the medium lymphocytes in the early foetal period. The small lymphocytes though to a lesser extent, are also capable of division in the foetal thymus and in the infantile thymus. Incorporation of uridine is also increased in the early foetal thymus.Cytological composition and lymphopoiesis of the foetal thymus and lymph node, have been compare

ISSN:0021-9541    

DOI:10.1002/jcp.1040800210

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe effects of cytochalasin B or low concentrations of adenosine 3′,5′‐monophosphate (cyclic AMP) were tested on melanophores in hanging drop preparations of neural fold explants fromXenopus laevisembryos in Barths' solution. After one week in culture, the melanophores were punctate in this medium. Cyclic AMP at 5 mM consistently caused reversible morphological transformation of these cells to the stellate state, whether they were situated within an epithelial outgrowth or isolated on the surface of the coverglass. Only the isolated melanophores consistently responded to 1 mM cyclic AMP. Cytochalasin B at 1–10 μg/ml caused aggregation of melanin granules in stellate cells, but left long, narrow cell branches containing some melanosomes. Its effect was at least partially reversible and appeared to be dose dependent. At 1% concentration, dimethyl sulfoxide caused melanin di

ISSN:0021-9541    

DOI:10.1002/jcp.1040800211

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

年代:1972

数据来源: WILEY