摘要:

AbstractThe effect of serum albumin on the washout of K42from isolated frog sartorius muscles, previously labeledin vitrowith this isotope, has been investigated. Incorporation of 1% serum albumin in the washout fluid has been found to cause a significant reduction in the rate constant for K42loss from the muscle fibers. A similar reduction in the rat constant for K42efflux was observed when the medium, though not containing protein, was exhaustively dialyzed before use against a solution containing serum albumin. Addition of 10−6M HgCl2to “dialyzed” Ringer increased the rate of loss of K42from the fibers. Effects similar to those obtained with serum albumin were observed when 10−4M cysteine was incorporated in the washout fluid. 3‐mercapto‐propanol gave rise to transient reductions in the rate of K42efflux, but, following prolonged exposure to this agent, the efflux rate was increased. 2′3‐dimercapto‐propanol (BAL) increased the rate of K42loss from the fibers. It is suggested that this effect of serum albumin is due to its sequestering action on toxic substances (tentatively identified as heavy metals) normally present in trace amounts in R

ISSN:0021-9541    

DOI:10.1002/jcp.1040670202

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

年代:1966

数据来源: WILEY

摘要:

AbstractCells ofTetrahymena pyriformishave been cold‐synchronized using a repetitive cycle of six, two‐hour cold shocks (9.5°C) alternating with decreasing periods (60–30 minutes) at 28°C. This system gives a maximum division index of 70–80% occurring at 90 minutes from the end of the last synchronizing cold‐treatment (EC). Examination of the division sensitivity of these cells to actinomycin D applied continuously at ten‐minute intervals from EC reveals that division is essentially blocked until approximately 40 minutes past EC, after which a rapid decrease is sensitivity to the inhibitor occurs. Coinciding with this period of high sensitivity is the occurrence of a peak of C14uridine incorporation at 40 minutes past EC. Inhibition of this peak is correlated with an inhibition of division, whereas strong inhibition of RNA synthesis beyond 60 minutes past EC has little effect on division activity. The similarity of these findings with those of the heat‐synchronized system is discussed with the suggestion that both heat‐ and cold‐synchronizing treatments result in the synchronous resynthesis of a division‐assoc

ISSN:0021-9541    

DOI:10.1002/jcp.1040670203

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

年代:1966

数据来源: WILEY

摘要:

AbstractHeat production was measured calorimetrically in the turtle,Pseudemys scripta elegans, (a) while submerged and (b) while partially submerged and breathing various gas mixtures. Submersion resulted in a profound reduction of heat production (80%). This reduction was not merely a response to the diveper se, but depended on the oxygen concentration available to the turtle prior to the onset of the dive. Heat production while breathing gas mixtures with different O2concentrations was unchanged down to 5% O2. At 3% O2, heat production was 50% of normal, and at 100% N2, it was 20% of normal. Uptake of dissolved O2from water was found to be 6% of the O2uptake from air by these turtles. These results suggest that following diving, there is a profound reduction in metabolic rate, but not until the O2stores are depleted. This low rate is primarily anaerobic and only a very low oxidative metabolism can be supported by O2extracted from the water.

ISSN:0021-9541    

DOI:10.1002/jcp.1040670204

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

年代:1966

数据来源: WILEY

摘要:

AbstractRabbit skeletal muscle homogenates were fractionated by differential centrifugation over the range 2,000−35,000 × G, and the calcium pumping activity of each fraction was assayed, together with the sensitivity of this activity to ryanodine. The greatest ryanodine sensitivity was found in material sedimenting between 2,000−4,000 × G, with decreasing sensitivities seen in the successively lighter fractions.Muscle mitochondria accumulated calcium slowly, the process being essentially insensitive to ryanodine but greatly inhibited by azide. With oxalate present in the incubation medium the ryanodine‐sensitive fractions showed no inhibition by azide or by dinitrophenol; when oxalate was omitted the pumping activity decreased greatly but now was inhibited by azide and little affected by ryanodine.Although the cellular origin of the sensitive calcium pumping element is not yet known, it appears that it is derived from the sarcoplasmic reticulum rather than from mitochondria, and may represent a substructure of the reticulum possessing specialized pharmacological pro

ISSN:0021-9541    

DOI:10.1002/jcp.1040670205

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

年代:1966

数据来源: WILEY

摘要:

AbstractTwo new alleles, C and c, involved in mating type expression were demonstrated. A dominant allele, C(cycler), must be present for the expression of the rhythm involving a sequential alternation of the two complementary mating types (III and IV). Cultures can be entrained with light‐dark cycles. The phase of each clone can be characterized by its III to IV and IV to III transitions in relation to the zero hour of a given light‐dark cycle. Phase is a stable phenotypic trait during asexual reproduction, but following sexual reproduction it does not display Mendelian segregation. Instead phase is determined through nuclear differentiation, i.e., the trait is controlled by differently determined macronuclear alagen (caryonidal inheritance) which normally segregate at the second cell division after conjugation. The phase of a clone within its genetic limits is a function of the photofractions and the light intensities used in the entraining treatment. By examining a number of clones a variety of phase angles between the mating type cycle and the entraining light‐dark cycle are found. Dividing cells which are sexually unreactive and therefore do not express the rhythm can be entrained and following entrainment, phase is inherited through repeated cell replications at a rate greater than one fission a day in continuous darkness or continuous dim light. This result unique to this system indicates that the cellular processes underlying the phase and period of this circadian rhythm persist (unexpressed: sexual reactivity requires slight starvation) through repeated cell replications even when the division cycle is considerably shorter than the expressed circadian period. The rhythm has a circadian period in continuous darkness or light (tested for six days) of less than 24 hours. The reversal of mating type ceases in continuous light at higher intensities. Cells homozygous for the recessive allele, c(acyclic), do not reverse mating type but are either mating type III or IV, again as a consequence of nuclear differentiation. Since individual cells with the dominant allele express both mating types, differentiation for mating type can not involve the absence in the macronucleus of mating type determining fa

ISSN:0021-9541    

DOI:10.1002/jcp.1040670206

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe morphologic, functional, and biochemical changes produced by hematoporphyrin and light in human platelets have been characterized. by phase microscopy the cells appeared swollen and resembled signet rings; by electron microscopy they showed considerable loss of cytoplasm and their contour was smoother than normal. irradiated platelets were not aggregable by thrombin and calcium chloride, although they contained clottable protein, and were incapable of supporting clot retraction. a linear relationship was demonstrated between the per cent depletion of serotonin from irradiated platelets and the log dose of hematoporphyrin. the depletion of serotonin from these platelets was related lineraly to the log of time of exposure to light during the initial six minutes of exposure; but thereafter continued at a constant rate. the temperature of incubation influenced directly the rate of depletion of serotonin from irradiated platelets but did not influence the movement of serotonin into these platelets. atp was diminished considerably in irradiated platelets. these changes are attributable to damage to the membrane of the platelet by hematoporphyrin and light.These studies provide additional information about the blood platelet in terms of its response to photodynamic action.

ISSN:0021-9541    

DOI:10.1002/jcp.1040670207

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

年代:1966

数据来源: WILEY

摘要:

AbstractA linear relationship was demonstrated between the reciprocals of the concentration of free hematoporphyrin and the moles of hematoporphyrin taken up by the platelet in the dark. radiated platelets took up more hematoporphyrin than did controls; this increase in uptake was accounted for by the movement of the dye across the damaged membrane of the cell. platelets irradiated at 4°c remained impermeable to hematoporphyrin until warmed to 37°c. during the initial three to four minutes of exposure to light at 37°c, there was no additional uptake of hematoporphyrin by platelets in comparison to controls. between six to ten minutes irradiation, the uptake of hematoporphyrin increased linearly with the log time of irradiation. thereafter, no further uptake occurred. a further increase in uptake of dye was demonstrated by both control and irradiated platelets at a reduced ph. this study enables a correlation to be made between the effects of hematoporphyrin on the platelet and the uptake of this agent by the platel

ISSN:0021-9541    

DOI:10.1002/jcp.1040670208

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe response of thymic lymphocytes of the pig to phytohemagglutinin was studied with H3thymidine in cultures, from 0–72 hours. At the beginning of the culture period 6–18% of lymphocytes were in DNA synthesis. during the first 24 hours a sharp decrease in the number of DNA synthesizing cells was observed in bothphaand control cultures, although pha cultures consistently showed small but significantly greater numbers of DNA synthesizing cells. this was followed by a definite peak in DNA synthesis and mitotic response of a minority of the cells inphacultures between 48–54 hours, whereas in control cultures activity ceased. in addition, a small proportion of the progeny of initially DNA synthesizing medium sized lymphocytes was apparently stimulated by pha and found in mitosis by 48 hours.It was concluded that the thymus contains a fraction of lymphocytes, not in the mitotic cycle, which are capable of being transformed byphato mitotic activity. the data also suggests some stimulation of cells already in the mitotic

ISSN:0021-9541    

DOI:10.1002/jcp.1040670209

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

年代:1966

数据来源: WILEY

摘要:

AbstractThe respiratory activity of avian blood cells was determined with samples of whole blood from individual male and female chickens. this oxygen consumption represents only that of the cells since no measurable activity was found in the plasma samples. the precision of determining respiratory activity was examined statistically and found to be approximately that obtained with a blood cell count but much less precise than the packed cell volume determination. the variability of cell count and mean corpuscular volume indicates that neither is a good means for expressing oxygen consumption – the most meaningful basis is oxygen consumption per milliliter of cells. the relationship between blood cell respiration and temperature is describe

ISSN:0021-9541    

DOI:10.1002/jcp.1040670210

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

年代:1966

数据来源: WILEY

摘要:

AbstractBy the “labeled mitoses” method of Quastler and Sherman and others, the cell cycle of the germinative zone cells of the bullfrog lens epithelium has been characterized. It has been shown that this cycle lasts approximately 83 days with the DNA synthetic phase enduring 100 hours and G2, 11 hours. G1occupies over 90% of the total time. the duration of mitosis itself has not been precisely determined. the length of the synthetic phase was corroborated by double labeling with c14and h3‐thymidine.When the temperature is raised by 6°c, from 24° to 30° the cycle is compressed by 40%.When the nongerminative, central cells of bullfrog lens epithelium are activated (stimulated to undergo DNA synthesis and mitosis) by injury or throughin vitroculture, the length of the cycle also appears to decrease. in thein vitroexperiments the generation time, as judged by the period elapsing between two successive bursts of DNA synthesis involving the same cells, amounts to 177–190 hours at 24°c. by raising the temperature to 30°c the time from injury or isolation until the appearance of the first wave of mitosis is re

ISSN:0021-9541    

DOI:10.1002/jcp.1040670211

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

年代:1966

数据来源: WILEY