ISSN:0021-9541    

DOI:10.1002/jcp.1040680202

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

年代:1966

数据来源: WILEY

摘要:

AbstractIsolated single giant synapses from the squid stellate gangalion, analyzed for cholinesterase activity with the microgasometric magnetic diyer method had a high activity compared to that of pieces of pre‐ and postsynaptic axon

ISSN:0021-9541    

DOI:10.1002/jcp.1040680203

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

年代:1966

数据来源: WILEY

摘要:

AbstractHuman platelets, exposed to hematoporphyrin and light, were depleted of potassium and acid phosphatase. A linear relationship was demonstrated between the per cent depletion of potassium from irradiated platelets and the log dose of hematoporphyrin. The initial release of potassium and acid phosphatase from irradiated platelets was first order. Rate constants demonstrated that potassium was released five times faster than acid phosphatase. At 4°C, release of both potassium and acid phosphatase was the same as at 37°C. These results are compared to previous data on the release of serotonin from irradiated platelet

ISSN:0021-9541    

DOI:10.1002/jcp.1040680204

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

年代:1966

数据来源: WILEY

摘要:

AbstractNaturally‐decapitated spermatozoa were separated into motile flagella and head and immotile flagella by differential and density gradient centrifugation. In preparations microscopically free of cross‐contamination after repeated centrifugation, the heads appeared to be enzymatically inert, while there was virtually no change in the specific activity of the immotile flagella which had been subjected to as much manipulation as the heads. The non‐motile flagella had almost twice the acetylcholinesterase and about one‐third the apyrase activity of the motile flagella. The flagella appear to contain a structurally‐bound adenosinetriphosphatase which may be identical with the “spermosin” extracted fr

ISSN:0021-9541    

DOI:10.1002/jcp.1040680205

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

年代:1966

数据来源: WILEY

摘要:

AbstractPig thymus tissue was cultured with organ culture techniques in the presence and absence of phytohemagglutinin in the culture medium. Morphologic and autoradiographic observations indicate that in the pig, lymphocytes capable of responding to phytohemagglutinin are located predominantly in the medulla of the thymus.

ISSN:0021-9541    

DOI:10.1002/jcp.1040680206

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

年代:1966

数据来源: WILEY

摘要:

AbstractElectrically stimulated contraction ofSpirostomum ambiguumwas investigated by high speed cinematography (up to 6,000 pps). Contraction is completed in about 4 msec following a latent period of up to 30 msec. Reduction in length during contraction followed a sigmoid curve, and final length was about 50% of the original length. Contraction always started at the end of the animal directed towards the anode. When the length of each half was measured separately, it was found that the cathodal end lagged about 1 msec in all cases observed. Rate of contraction was increased when the external calcium contraction was increased, and was decreased in Ca‐free and K‐free solutions, but was unchanged in K‐rich solutions. These results are interpreted in terms of contraction being associated with a relative increase of calcium bound to the contractile protein. The differential migration of potassium and calcium ions in an electric current would result in a temporary lowering of K+at the anodal end of the animal, hence a relative rise would take place in the Ca++available for binding. The results of experiments using changed calcium and potassium concentrations can be explained by this hypothesis which is in general agreement with modern work on muscle contraction and relax

ISSN:0021-9541    

DOI:10.1002/jcp.1040680207

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

年代:1966

数据来源: WILEY

摘要:

AbstractIt has been known for over 100 years that when the protoplasm of protozoan cells respond to electrical stimulation by contraction, contraction always starts at theanodalend (e.g.,Spirostomum, Jones, Jahn and Fonseca, 1965). It also is known that the cell membrane of protozoa does not have a self‐propagating depolarizing action potential of the type found in axons and muscle cells.If we assume that contraction of the cytoplasmic protein is caused by an increased association of calcium with the protein, as known for muscle, these antithetical facts can easily be explained. Another necessary assumption is that all of the anionic sites on the protein have associated counterions, in accordance with the theories of Debye‐Hückel, Ling, and Eisenman.On the basis of known ionic electrical mobilities it can be predicted for cells with non‐excitable membranes that calcium (1) is removed from both the inside and the outside of the membrane at the cathodal end and is added to both sides at the anodal end, (2) is added to cytoplasmic protein throughout the cell, but is added more rapidly at the anodal end, and (3) is made available for addition to cytoplasmic protein at the cathodal end, as it is released from the membrane. In a cell with an excitable membrane the above will be true, and furthermore (4) the action current will release larger quantities of calcium than those resulting directly from the stimulus. For these reasons it is predictable that in cells with a non‐excitable membrane, contraction should start at the anodal end, whereas in cells with excitable membranes, it should start at the cathodal end, and that is exactly wha

ISSN:0021-9541    

DOI:10.1002/jcp.1040680208

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

年代:1966

数据来源: WILEY

摘要:

AbstractLog phase cultures ofTetrahymena pyriformisW excrete orthophosphate, a purine, and a pyrimidine when suspended in a non‐nutrient buffered medium. Ribonucleic acid has been established as the primary source of these catabolic products. Thirty per cent of the total cellular RNA was degraded in three hours under the conditions of growth and suspension employed. The size of the phosphorus pools of these ciliates was determined during the period of RNA degradation; the internal acid‐soluble organic phosphate and the cellular orthophosphate pools remained constant for five hours at 20% and 5% of the total cell phosphorus respectively. The ultraviolet‐absorbing materials excreted with the orthophosphate were identified as hypoxanthine and uracil. A pentose, presumably ribose, was excreted in small quantities, but was not equivalent in amount to the orthophosphate and did not parallel the pattern of release of the anion. The excretion of orthophosphate, hypoxanthine, and uracil is correlated with the catabolism of RNA as it has been demonstrated in these

ISSN:0021-9541    

DOI:10.1002/jcp.1040680209

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

年代:1966

数据来源: WILEY

摘要:

AbstractNet RNA degradation occurs inTetrahymem pyrifmmiswhen this ciliate is suspended in a non‐nutrient medium. The quantity and quality of the excretion products is at least partially under the control of the ionic content and the tonicity of the cellular environment. The excretion of ultraviolet‐absorbing materials was found to be elevated by sodium ions in a medium isotonic to the culture fluid, or by a hypertonic environment. Magnesium counteracted these effects.In isotonic suspension, sodium and magnesium ions lowered orthophosphate excretion; however, sodium altered the nature of the phosphate products so that acidlabile phosphates were also excreted rather than solely orthophosphate. Similar results were obtained in a hypertonic environment with or without sodium.The degree of purine and pyrimidine loss from the cells in all conditions of suspension was reflected in the amount of RNA degraded. The ion and tonicity effects apparently reflect events which alter the stability of the RNA and the properties of the membrane system, resulting in changes in both the rate of RNA degradation and the nature of the excreted products. The rates of orthophosphate excretion appear to be affected by changes in the acid‐base balance within the cell which may be governed by the cation levels. The manipulation of the ionic content and tonicity of the medium offers a convenient method for obtaining cells reduced in RNA co

ISSN:0021-9541    

DOI:10.1002/jcp.1040680210

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

年代:1966

数据来源: WILEY

摘要:

AbstractIn homogenates ofTetrahymena pyriformis, five hydrolases — phosphatase, ribonuclease, deoxyribonuclease, proteinase, amylase — with acid pH optima were found. Over 75% of their activity is sedimentable with a centrifugal force of 250,000 g. min. Only 17% of the acid phosphatase and ribonuclease is active when assayed in the presence of 0.25 M sucrose at 0°. Exposure to a lowered osmotic pressure, freezing and thawing, and incubation at temperatures over 0° result in activation of the latent phosphatase and ribonuclease. After isopycnic centrifugation in a sucrose density gradient the hydrolases show a broad distribution which differs greatly from those of enzymes associated with mitochondria (succinate dehydrogenase) or with peroxisomes (catalase). The results are interpreted as evidence that the five acid hydrolases studied are localized in lysosomes which represent a distinct population of subcellular particles inTetrah

ISSN:0021-9541    

DOI:10.1002/jcp.1040680211

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

年代:1966

数据来源: WILEY