摘要:

AbstractErythropoiesis was suppressed in CDF1female mice using one of three different techniques: hypertransfusion, daily injections of low doses of actinomycin D, or post‐hypobaric polycythemia. Spleens and bone marrows of these mice contained increased numbers of stem cells as determined by transplantation into lethally irradiated syngeneic mice. These stem cells were capable of producing both erythrocytic and granulocytic progeny. An increase in the number of multipotential stem cells or increases in the numbers of both unipotential granulocytic and erythrocytic stem cells is compatible with these observations and implies that hematopoietic stem cells may have a basic rate of division that is in part independent of stimuli to differentiate. The implications of these findings for the possible modification of antineoplastic drug‐induced bone marrow toxicity are discus

ISSN:0021-9541    

DOI:10.1002/jcp.1040790112

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe rate of synthesis of different hemoglobin (Hb) species — embryonic, primitive, definitive, and adult — in the circulating red cells of the chick embryo have been measured. On the fifth day of chick embryogenesis, there is a marked decrease in the capability of these red cells to synthesize Hb. The rates of synthesis of embryonic and primitive Hb decrease markedly compared to that of definitive and adult Hb. On the fourth day of embryogenesis nucleic acid synthesis drops sharply in these cells. These decreases in metabolic activity preceed the disappearance of the primitive erythrocyte from the chick embryo circulation. It appears that the primitive cell line is specifically shut off with respect to its metabolic activities and possibly destroyed at this t

ISSN:0021-9541    

DOI:10.1002/jcp.1040790113

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe effect of di‐ and trivalent cations on the membrane potential of the Ehrlich ascites tumor cell has been investigated using micro‐electrode techniques. In solutions free of multivalent cations the average membrane potential for 46 cells was 8.3 ± 0.5 mv (SE). However, the potentials were not stable and decayed with a half‐time of about six seconds. Addition of Ca++decreased the rate of decay and concomitantly increased the membrane potential. The magnitude of these effects was a function of the Ca++concentration. At the optimum concentration (2 mM), the half‐time of decay was increased to 12 seconds and the membrane potential was raised to 17.8 ± 1.7 mv (SE). The related alkaline‐earth cations, Sr++, Ba++and Mg++had similar effects on both the stability and magnitude of the membrane potential. The effect of La+++, which was qualitatively similar to that of the divalent cations, was also concentration dependent. However, 100‐fold lower concentrations were adequate to achieve comparable effects. Moreover, membrane potentials were stable for up to ten minutes in La+++‐containing solutions. Variations in intracellular Cl−content induced by temperature changes were paralleled by changes in membrane potentials. However, the potentials were not those expected for a si

ISSN:0021-9541    

DOI:10.1002/jcp.1040790114

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

年代:1972

数据来源: WILEY

摘要:

AbstractThe distribution of sedimentation velocities was determined, by a photoelectric method, for human erythrocytes at low concentrations in Ringer solution. The light absorption at 414 nm was measured, as a function of time, 10 mm below the top of the column. From the frequency distribution of cell velocities that of Rs√ρ‐σ was found; Rsbeing the Stokes' radius, ρ the cell density and σ the density of the solution. Cell density was measured by the phthalate method and the mean Stokes' radius was found to be 2.58 μm. The size distributions showed some skewness but were in good general agreement with those measured by Celloscope counter, and with reported measurements from photomicrographs of cells in hanging drop suspensions. The skewness was much less than that encountered with electric sensing zone instruments (e.g. Celloscope) and the sedimentation method, being based on entirely different premises, provides an important check on such data. The skewness is due to a bias in the orientation of human erythrocytes during sedimentation. This bias may be a characteristic of biconcave cells; it could be absent in many species and reliable measurements of size distribution would then be

ISSN:0021-9541    

DOI:10.1002/jcp.1040790115

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

年代:1972

数据来源: WILEY

摘要:

AbstractPig kidney cells exhibit resistance to puromycin when cultured at high cell densities, growing progressively in otherwise lethal concentrations of drug. Comparison of population growth of cultures inoculated at different densities indicates that survival in puromycin is a function of cell density. Uptake of puromycin from culture media is less at higher cell densities resulting in decreased inhibition of protein synthesis by puromycin. Enhanced survival in puromycin at high population densities is attributed to reduced accumulation of puromycin from the culture media.

ISSN:0021-9541    

DOI:10.1002/jcp.1040790116

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

年代:1972

数据来源: WILEY

ISSN:0021-9541    

DOI:10.1002/jcp.1040790117

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

年代:1972

数据来源: WILEY

摘要:

AbstractRates of secretion of milk constituents (fat, protein, lactose, Na+and K+) in the lactating goat were measured under normal circumstances and after injections of ouabain. In all experiments a close association was noted in the secretion rates for protein, lactose and K+. Under the influence of ouabain, the concentration of Na+in the milk tended to rise and that of K+to fall. The rate of milk fat secretion varied independently from the rates for the other constituents. It is reasonably assumed that the principal mechanism of milk protein secretion is by emptying of Golgi vesicles through the plasma membrane. The close correlation in rates for protein, lactose and K+supports the contention that all three are assembled in Golgi vesicles and secreted by the same mechanism.

ISSN:0021-9541    

DOI:10.1002/jcp.1040790118

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

年代:1972

数据来源: WILEY

ISSN:0021-9541    

DOI:10.1002/jcp.1040790119

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

年代:1972

数据来源: WILEY

ISSN:0021-9541    

DOI:10.1002/jcp.1040790101

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

年代:1972

数据来源: WILEY