摘要:

AbstractArtificially maintained colonies of the colonial marine hydroidHydractinia echinataare endogenously limited in lateral growth and usually develop in a circular pattern with a closed periderm. Further lateral growth consists of free stolons. Preliminary studies of tissue compatibility in regenerating explants indicate that fusion generally fails to occur if the opposing explants are of differing sex, from different individuals of the same sex, or if peripheral explant contact occurs after free stolons have begun to form. Of the three aforementioned causes of fusion failure, the most important factor appears to be the timing of peripheral explant contact. If regenerating explants contact each other before the endogenous circular growth pattern is achieved, fusion will occur regardless of sex and/or individuality. Incompatibility between explants from the same individual may be because of periderm development inhibition in some instances. However, the failure of free stolon fusion between explants from the same individual suggests the development of “temporal specificity” once the endogenous limit of lateral growth is achie

ISSN:0021-9541    

DOI:10.1002/jcp.1040690202

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

年代:1967

数据来源: WILEY

摘要:

AbstractLabeling index as well as the duration of DNA synthesis in alveolar cells of C3H mouse mammary gland at various stages of development was determined by autoradiographic methods. Labeling index of the alveolar cells is highest during pregnancy followed by a marked decrease in the lactating gland. The labeling index of the prelactating cells is significantly reduced after the same cells are transplanted into virgin females. Duration of DNA synthesis in the alveolar cells at eighth and fifteenth day of pregnancy is 14.1 and 8.2 hours respectively. During early lactogenesis, duration of DNA synthesis in the mammary alveolar cells was estimated as 8.5 hours. There is a 2–3 fold increase of the DNA replication time (21.5 hours) in the outgrowth cells of 15 day prelactating tissue after transplantation into virgin host.A possible role of the hormones of pregnancy, estrogens and progesterone for stimulation of DNA synthesis in the prelactating tissue has been discussed. It has been suggested that the marked inhibition of DNA synthesis in the lactating tissue may be due to the increased stimulation of the same tissue by endogenous adrenocorticoid hormones. Variability of the duration of DNA synthesis (8.5–21.5 hours) in alveolar cells indicates that in mouse mammary gland, DNA synthetic time is not an unadjustable process. Control of DNA synthesis in mouse mammary gland cells by exogenous 17‐β‐estradiol and progesterone has been previously reported (Bresciani, '65). It is suggested that the same hormones of endogenous origin also may influence the duration of DNA synthesis and cell proliferation during mamm

ISSN:0021-9541    

DOI:10.1002/jcp.1040690203

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

年代:1967

数据来源: WILEY

摘要:

AbstractStudies were made of the stimulation by 2,4‐dinitrophenol (DNP) of an adenosine triphosphatase (ATPase) in stromata of human erythrocytes. Activation by 2,4‐dinitrophenol occurs in the range 10−5to 10−3M and was seen in whole cells, ghosts reconstituted with Mg and ATP, and in osmotic ghosts prepared at a low ratio of cells to water. Phloretin and phloridzin also activated the DNP sensitive system but inhibited it at higher concentrations. DNP increased the Kmand Vmaxvalues of the enzyme equally. The DNP sensitive and Na++ K+sensitive enzymes of the stromata were compared. The activities of the two ATPases are additive, require the presence of Mg++and require that the substrate be located at the inner surface of the membrane. The two enzymes differ in their substrate specificity, in their sensitivity to inhibition by ouabain and phloretin and in their sensitivity to some factor in hemolysates. The possible roles of this system in the erythrocyte were di

ISSN:0021-9541    

DOI:10.1002/jcp.1040690204

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

年代:1967

数据来源: WILEY

摘要:

AbstractAcid phosphatase activity has been studied in the amebaMayorella palestinensis. Optimum activity of the enzyme was found to be at a pH of 3.2. The enzyme is inhibited by fluoride ion, but is not sensitive to Mg++.The activity was found to be correlated with age of culture. Two maxima have been obtained, one from cultures in the logarithmic phase, and the other during the period of maximal cell encystation. These results suggest that acid phosphatase play an important role in cell metabolism during growth and differentiation processes of this ameba.

ISSN:0021-9541    

DOI:10.1002/jcp.1040690205

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

年代:1967

数据来源: WILEY

摘要:

AbstractColloidal stability theory is discussed to accomodate the conditions imposed by biological systems. It is shown that to obtain potential curves with secondary minima, Hamaker's constant must be in the range of 1–5 × 10−14ergs. The effect of increasing the dielectric constant is shown in theory to lower the surface potential and electrophoretic mobility but to increase the total energy of interaction. Calculations made from the theory predict the forces between model cells to be ca. 4.0 × 10−7dynes.By cone‐plate shearing of cell aggregates, the most successful of several techniques tried and discussed, at shear rates approaching 1 × 10−4second−1(1.5 × 10−4dynes) semi‐complete disaggregation was achieved although cell disruption was apparent; analysis of blood viscosity data indicates 5–10 × 10−7dynes are required to separate red cells suspended in plasma. Colloidal stability theory, while not applicable to cell systems associated by special areas of attachment, seems to describe the physicochemical interaction of freely moving or r

ISSN:0021-9541    

DOI:10.1002/jcp.1040690206

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

年代:1967

数据来源: WILEY

摘要:

AbstractA comparative study of some physico‐chemical properties of alkaline phosphatase of a human cell line, the EUE, with high level of enzyme and one of its clonal derivatives the E6D, with low activity, has been carried out.Electrophoretic analysis reveals a multiple banding pattern within each line and qualitative differences between the two lines. The alkaline phosphatase activity of the E6D cell extracts is almost completely inhibited by 5 × 10−2M inorganic phosphate while in the EUE the enzymic activity is reduced to one third under these conditions. The enzymes of the two lines show also a different thermostability which is not referable to extrinsic factors, as demonstrated by mixing experiments. The time course of heat inactivation at 70°C suggests molecular heterogeneity in each line, and a prevalence of a thermostable fraction in the cells with low activity and a thermolabile one in those with high enzymic levels. A rough estimate of inactivation constants does not rule out the possibility that the molecular species in the two lines are the same but in different proportions. The cytological analysis confirms the relationship between the number of small acrocentric chromosomes and alkaline phosphatase levels. The significance of the biochemical data in relation to the proposed model of a gene dosage effect is disc

ISSN:0021-9541    

DOI:10.1002/jcp.1040690207

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

年代:1967

数据来源: WILEY

摘要:

AbstractA two‐stage procedure has been used to obtain hemopoietic spleen colonies derived from single precursor cells containing radiation‐induced chromosomal markers. Of a total of 46 colonies examined, 17 were found to contain cells with abnormal karyotypes. In each of the 17 marked colonies, 90% or more of the dividing cells in the colony carried the same marker. Cell suspensions prepared from each of the individual colonies were tested for their content of dividing cells possessing recognizable differentiated functions. Metaphase cells with peroxidase‐positive granules in their cytoplasm were considered to be members of the granulopoietic series, while metaphase cells which contained Fe55were considered to be members of the erythropoietic series. Results were obtained for 12 of the marked colonies, and in nine of these, the percentage of metaphases lacking the marker was less than the percentage of metaphases which were scored as erythropoietic, and also was less than the percentage of metaphases scored as granulopoietic. This is the result which would be expected if the marker were present in both erythropoietic and granulopoietic cells. These results provide support for the view that colony forming hemopoietic stem cells are multipotent, and that differentiation along more than one pathway can occur during the formation of macroscopic splenic col

ISSN:0021-9541    

DOI:10.1002/jcp.1040690208

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

年代:1967

数据来源: WILEY

摘要:

AbstractReaction of the slowly penetrating organic mercurial compound parachloromercuribenzene sulfonate (PCMBS) with intact erythrocytes has been characterized. Addition of concentrations of PCMBS which result in binding within the interior of the membrane of more than 1.9 × 10−18moles/cell produces alterations in Na+and K+permeability, but does not affect choline permeability. However, the increased cation permeability is observed only after a lag period of over two hours. After ten hours, a spontaneous slow “recovery” to normal rates of K+leakage occurs at 25°C but not at 2°C. Subsequent to the effects on cation balance, increasing degrees of hemolysis occur, interpreted as colloid osmotic lysis. The relationships between the binding of the agent and its effects are as follows: a small, rapid initial uptake does not affect cation permeability; the subsequent slower uptake is associated with increased leakage of K+and Na+; and the recovery at 25°C is associated with desorption of about half of the PCMBS due to competition by soluble thiol substances released into the medium from the cells. Desorption and “recovery” can be mimicked at any time by addition of small amounts of protein in the medium. The half of the PCMBS that cannot be desorbed is assumed to be bound by the hemoglobin inside the cell. The sulfhydryl groups involved in control of cation permeability constitute only a fraction of the total within the membrane (4–18%). They are located within the interior of the membrane separated from the medium and from the interior of the cell by diffusion ba

ISSN:0021-9541    

DOI:10.1002/jcp.1040690209

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

年代:1967

数据来源: WILEY

摘要:

AbstractCultured Chinese hamster cells incorporated radioactivity from glucosamine‐1‐14C into surface sialic acid and into trypsin‐removable material distinct from the surface sialoglycans. Cells prelabeled with glucosamine‐1‐14C and then transferred to medium containing unlabeled glucosamine progressively lost counts to the medium for many hours. Such chase experiments suggested a more rapid turnover of trypsinremovable material than of surface‐bound sialic acid. Further studies of the regeneration of surface sialic acid showed that the actinomycin D‐resistant portion of the process involved emergence of an intracellular precursor onto the cell surface. An earlier portion of the process was inhibited by actinomycin D, and at least three steps were inhibited by puromycin or

ISSN:0021-9541    

DOI:10.1002/jcp.1040690210

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

年代:1967

数据来源: WILEY

摘要:

AbstractRibonucleic acid polymerase and deoxyribonucleic acid polymerase have been partially purified from bovine lymphosarcoma, lymph node, and thymus. An examination of the deoxyribonucleic acid requirements of the two enzymes indicates that “native” deoxyribonucleic acid is the preferred template for ribonucleic acid synthesis; heat‐denatured deoxyribonucleic acid is considerably less active. The primer requirements for deoxyribonucleic acid synthesis differ: “native” deoxyribonucleic acid is usually inactive, while denatured deoxyribonucleic acid is active. The two enzymes also differ in pH optima and in their requirements for metal

ISSN:0021-9541    

DOI:10.1002/jcp.1040690211

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

年代:1967

数据来源: WILEY