scholarly journals OXYGEN TENSION AND THE RATES OF MITOSIS AND INTERPHASE IN ROOTS

1962 ◽  
Vol 13 (3) ◽  
pp. 365-371 ◽  
Author(s):  
J. E. Amoore
Keyword(s):  
Oxygen Tension ◽  
Cent Oxygen ◽  
Low Oxygen ◽  
Root Tips ◽  
Pea Root ◽  
Wide Range ◽  
Oxygen Tensions ◽  
Mitotic Figures

The object of this work was to determine the influence of a wide range of oxygen tensions upon the relative rates of respiration, mitosis, and interphase in pea root tips, compared with the normal rates of these processes in air. From the rates of disappearance of mitotic figures in excised tips kept in various oxygen tensions, the relative rates of mitosis were found to decrease gradually from 122 per cent in 100 per cent oxygen to 24 per cent in 0.0007 per cent oxygen. From the mitotic indices of intact seedlings, the relative rates of interphase were found to decrease sharply from 82 per cent in 10 per cent oxygen to 6 per cent in 5 per cent oxygen. The data on relative rates of respiration, mitosis, and interphase in root tips were compared, and it was shown that the three processes are perfectly distinct in their quantitative relationships to low oxygen tensions.

scholarly journals STUDIES ON BONE MARROW IN VITRO

Blood ◽  
1948 ◽  
Vol 3 (2) ◽  
pp. 165-174 ◽  
Author(s):  
A. ROSIN ◽  
M. RACHMILEWITZ
Keyword(s):  
Bone Marrow ◽  
Oxygen Tension ◽  
Gas Mixtures ◽  
Cent Oxygen ◽  
Low Oxygen ◽  
Bone Marrow Cultures ◽  
Oxygen Tensions ◽  
Marrow Cultures

Abstract The effect of various oxygen tensions on explanted bone marrow fragments was studied. It was found that gas mixtures containing 1, 3, 5, 10 and 12 per cent oxygen have an injurious effect on hemic cells. Bone marrow maintained in these gas mixtures showed various degrees of degeneration, which was the more pronounced the lower the oxygen tension. Mitotic activity was also found to be reduced under the influence of low oxygen tension. Bone marrow cultures maintained in a gas mixture containing 15 per cent oxygen did not show appreciable changes and were similar to the controls. Increased rate of maturation and multiplication occurred in bone marrow cultures maintained in an excess of oxygen, i.e. 50 per cent. The significance of these findings in the light of observations on the effect of anoxia in vivo has been discussed, and reported findings on the effect of low oxygen tensions on other tissues in vitro have been briefly reviewed.

Dependence of mitosis and respiration in roots upon oxygen tension

1961 ◽  
Vol 154 (954) ◽  
pp. 109-129 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Oxygen Uptake ◽  
Oxygen Tension ◽  
Oxygen Requirement ◽  
Anaerobic Conditions ◽  
Root Tips ◽  
Carbon Dioxide Output ◽  
Lower Oxygen ◽  
Oxygen Tensions ◽  
The Relationship

Excised pea-root tips were incubated for 4 h in gas mixtures containing 0.00001 to 100% oxygen, in order to determine the effect upon mitosis. Below 0.0005% oxygen, mitosis was completely arrested. Between 0.001 and 0.02% oxygen, cells initially in mitosis completed division, but no more cells started dividing. Between 0.05 and 0.2% oxygen, cells initially in interphase entered division, but did not finish. Above 0.5% oxygen, all cells not prevented from dividing by excision finished division within 4 h. After exposure to 0.05% oxygen for 4 h, an excessive proportion of cells was found in prophase; in 0.1% oxygen an excess of metaphases, and in 0.2% oxygen an excess of telophases resulted. The oxygen uptake and carbon dioxide output of root tips were measured in a range of oxygen tensions and in anaerobic conditions. The relationship between oxygen uptake and oxygen tension was hyperbolic; a half maximum rate of oxygen uptake was obtained at about 10% oxygen. It was concluded that the respiration of root tips was limited by slow diffusion of oxygen through the tissue. From the carbon dioxide output it was estimated that the amount of energy available to isolated root tips under anaerobic conditions was about 1% of that available under aerobic conditions. Possible mechanisms whereby extreme oxygen-lack could arrest mitosis were considered. It was shown that the arrest was not due to abolition of a gross supply of energy. No evidence was obtained as to what other mechanism might be operative. An hypothesis was formulated in an attempt to explain the complicated relationship between mitosis and oxygen tension. It was assumed that the visible phases of mitosis are immediately preceded by a phase with a higher requirement for oxygen than mitosis, and that preceding this is an earlier phase with a lower oxygen requirement than mitosis.

scholarly journals PARTICIPATION OF A NON-RESPIRATORY FERROUS COMPLEX DURING MITOSIS IN ROOTS

1962 ◽  
Vol 13 (3) ◽  
pp. 373-381 ◽  
Author(s):  
J. E. Amoore
Keyword(s):  
Carbon Monoxide ◽  
Cytochrome Oxidase ◽  
Hydrogen Cyanide ◽  
Iron Complex ◽  
Cent Oxygen ◽  
Root Tips ◽  
Systematic Survey ◽  
Divalent State ◽  
Pea Root ◽  
Ferrous Complex

A systematic survey was undertaken, of the effects of carbon monoxide and hydrogen cyanide (in the presence of 20 per cent oxygen), in darkness and light, on the relative rates of respiration, mitosis, and interphase in pea root tips. The inhibition of respiration by carbon monoxide was light-sensitive, but the inhibition by hydrogen cyanide was light-stable. The inhibitions were presumably due to combination of the inhibitor with the iron of cytochrome oxidase, in its divalent and trivalent forms respectively. In contrast, the inhibitions of mitosis by both poisons proved to be light-sensitive. The light-sensitive inhibition of mitosis by carbon monoxide shows that an iron complex is responsible for the process. That the inhibition of mitosis by hydrogen cyanide is also light-reversible shows that, in contrast with cytochrome oxidase, the mitotic iron complex remains always in the divalent state. The relative affinities of the mitotic ferrous complex, in molar units, were 0.68 for CO/O2, and 0.37 for HCN/O2. The properties of the complex are analogous to, yet distinct from, Gastrophilus haemoglobin and reduced cytochrome oxidase. It is considered that the arrest of mitosis by oxygen lack, carbon monoxide, and hydrogen cyanide is definitely due to interference with this unidentified, non-respiratory ferrous complex.

In Vitro Studies of Erythropoiesis

Blood ◽  
1955 ◽  
Vol 10 (6) ◽  
pp. 612-615 ◽  
Author(s):  
E. D. THOMAS
Keyword(s):  
Bone Marrow ◽  
Oxygen Tension ◽  
In Vitro Studies ◽  
Cent Oxygen ◽  
In Vitro Synthesis ◽  
Heme Synthesis ◽  
Rabbit Bone ◽  
Oxygen Tensions ◽  
Effect Of Oxygen

Abstract The effect of various oxygen tensions on the in vitro synthesis of heme by rabbit bone marrow was measured. At levels above 4 per cent oxygen there was no effect of oxygen tension on heme synthesis. Total anoxia stopped heme synthesis completely. No level of oxygen tension was found to stimulate heme synthesis.

scholarly journals THE EFFECT OF LOW OXYGEN TENSION ON TISSUE METABOLISM (RETINA)

1943 ◽  
Vol 26 (5) ◽  
pp. 467-472 ◽  
Author(s):  
Francis N. Craig ◽  
Henry K. Beecher
Keyword(s):  
Lactic Acid ◽  
Oxygen Tension ◽  
Acid Production ◽  
Lactic Acid Production ◽  
Reciprocal Relationship ◽  
Cent Oxygen ◽  
Low Oxygen ◽  
Rat Retina ◽  
Low Oxygen Tension ◽  
Phosphate Medium

Lactic acid production by rat retina in a medium containing phosphate was studied chemically. One half as much lactic acid was found as in a medium containing bicarbonate. In our experience the rate of respiration in a phosphate medium was sensitive to oxygen tension, for it was 38 per cent lower at 10 per cent and 51 per cent lower at 5 per cent oxygen than at 100 per cent oxygen. Previously Laser had reported no decrease in respiration at 5 per cent oxygen in phosphate medium. In phosphate medium, when the oxygen tension was varied, respiration and glycolysis bore a reciprocal relationship to each other. In bicarbonate medium, when the oxygen tension was lowered from 95 per cent to 5 per cent there was no significant change in the respiration, but glycolysis was increased nearly to the anaerobic level. This agrees with the earlier experiment of Laser in bicarbonate medium and adds support to his conclusion that the rate of glycolysis is controlled by oxygen tension rather than by the rate of respiration, under the conditions of the experiment.

Oxygen Pressure in Urine and Its Relation to Intrarenal Blood Flow

1958 ◽  
Vol 195 (1) ◽  
pp. 120-132 ◽  
Author(s):  
D. W. Rennie ◽  
R. B. Reeves ◽  
J. R. Pappenheimer
Keyword(s):  
Oxygen Tension ◽  
Oxygen Pressure ◽  
Cell Separation ◽  
Venous Blood ◽  
Alternative Mechanism ◽  
Low Oxygen ◽  
Arterial Blood ◽  
Anesthetized Dogs ◽  
Intrarenal Blood Flow ◽  
Oxygen Tensions

Oxygen tensions in renal pelvic urine, renal venous blood and arterial blood ( Pu, Pv, Pa) were measured in anesthetized dogs breathing oxygen tensions of 150, 760 and 1900 mm Hg. In dogs having high Diodrast extraction ratios, the respective values for Pu were 27, S.E. ± 3; 49 ± 5 and 120 ± 7 mm Hg. Corresponding values for Pv were 50 ± 3, 96 ± 8 and 858 ± 47 mm Hg. Renal O2 consumption was unaffected by oxygen tension; therefore, the increasing Pv– Pu cannot be interpreted as a gradient across tubule cells. In dogs having low Diodrast extraction ratios, Pu was higher (e.g. 72 ± 6 mm Hg in contrast to 49 ± 5 at 1 atm. O2). These results, which are difficult to explain by classical renal hemodynamics, can be accounted for by the cell-separation theory. Assuming that urine oxygen is equilibrated with peritubular capillary blood it is possible to calculate peritubular relative to arterial hematocrit ( HT/ Ha). HT/ Ha, so calculated, averages 0.52 ± .06 for high extraction kidneys and 0.96 ± .06 for low extraction kidneys, thus relating low Diodrast extraction to failure of cell-separation. An alternative mechanism, involving equilibration of urine oxygen with medullary, rather than peritubular, blood could also explain the facts provided that the hematocrit of medullary blood is low. Further work is required to localize the region of low oxygen tension within the kidney: the present results indicate, however, that the region concerned is supplied with blood of low red cell concentration. Oxygen in human bladder urine is largely determined by gaseous equilibration with ureteral walls and cannot be used as a measure of intrarenal oxygen pressure.

scholarly journals THE RELATION BETWEEN FOVEAL VISUAL ACUITY AND ILLUMINATION UNDER REDUCED OXYGEN TENSION

1940 ◽  
Vol 23 (5) ◽  
pp. 613-630 ◽  
Author(s):  
R. A. McFarland ◽  
M. H. Halperin
Keyword(s):  
Visual Acuity ◽  
Oxygen Tension ◽  
Cent Oxygen ◽  
Large Decrease ◽  
Atmospheric Conditions ◽  
Normal Value ◽  
Oxygen Tensions ◽  
The Right ◽  
Very High ◽  
Intensity Axis

1. The foveal visual acuity of eleven subjects was studied in relation to illumination under normal atmospheric conditions and at simulated altitudes of 10,000 feet (14.3 per cent O2) and 18,000 feet (10.3 per cent O2). A mask was used to administer the desired mixtures of oxygen and nitrogen. At the end of each experiment, measurements were made while inhaling 100 per cent oxygen from a cylinder. A red filter (No. 70 Wratten) was used so as to study only the behavior of the cones of the retina. 2. The logarithm of illumination was plotted horizontally (abscissa) and the logarithm of visual acuity vertically (ordinate). The reduced oxygen tensions resulted in a shift of the curve to the right, along the intensity axis, the extent of the change being 0.24 of a log unit at 14.3 per cent O2 and 0.47 of a log unit at 10.3 per cent O2. These effects were completely counteracted within a few minutes by inhaling oxygen. 3. As a consequence of the shape of the curve, such a shift to the right resulted in a relatively large decrease of visual acuity at low illuminations. At increasing light intensities anoxia produced less and less change, until at very high illuminations the decrease was negligible. Thus with 10.34 per cent O2 the visual acuity at 0.144 photons decreased an average of 0.344 of a log unit, to 45 per cent of its normal value. At 1320 photons, however, it decreased only 0.026 of a log unit, to 94 per cent of its normal value for that intensity.

Arrest of mitosis in roots by oxygen-lack or cyanide

1961 ◽  
Vol 154 (954) ◽  
pp. 95-108 ◽  
Keyword(s):  
Cell Division ◽  
Mitotic Index ◽  
Mitotic Arrest ◽  
Sodium Cyanide ◽  
Root Tips ◽  
Pea Root ◽  
Mitotic Figures ◽  
Number Of Cells

Excised pea-root tips were incubated in various conditions, in order to determine the effect upon mitosis. In air the mitotic index rapidly decreased, but in an atmosphere of oxygen-free nitrogen (containing less than 0·001% oxygen) mitotic figures persisted for up to 24 h. Counts of the total number of cells showed that the persistence of mitotic figures represented an arrest of mitosis by anaerobiosis, and not a continuation of cell division as had previously been surmized. The effects of oxygen-lack were simulated by 10 -2 M-sodium cyanide. Mitotic arrest persisted for only about 4 h if industrial nitrogen (containing about 0·05% oxygen) was used, or if 10 -3 M-cyanide was employed. The cells thus partially arrested slowly continued the normal course of mitosis, and did not merely revert directly to interphase. Similar results were obtained with different kinds of roots, and with intact seedlings. The results were in accordance with an hypothesis that all stages of cell division depend upon the presence of oxygen, but that the visible stages of mitosis are less dependent than is the stage of entering mitosis.

The respiratory responses of Carcinus maenas to declining oxygen tension

1976 ◽  
Vol 65 (2) ◽  
pp. 309-322 ◽  
Author(s):  
A. C. Taylor
Keyword(s):  
Heart Rate ◽  
Cardiac Output ◽  
Oxygen Tension ◽  
Rate Ratio ◽  
Carcinus Maenas ◽  
Level Of Activity ◽  
Wide Range ◽  
Oxygen Tensions ◽  
High Level ◽  
Respiratory Responses

The degree of respiratory independence shown by Carcinus under conditions of declining oxygen tension is dependent on the animal's level of activity. Inactive Carcinus are capable of maintaining respiratory independence down to a Po2 of 60–80 mmHg. This is achieved primarily by an increase in ventilation volume such that the amount of oxygen made available at the respiratory surfaces remains constant over a wide range of oxygen tension. The Po2 at which this can no longer be maintained corresponds closely to the Po2 at which respiratory independence is lost. Under normoxic conditions the Po2 of the post- and prebranchial blood was 97 and 18 mmHg respectively. At the high oxygen tensions prevailing in the postbranchial blood the respiratory pigment is fully saturated. Under conditions of declining oxygen tension the heart rate remains more or less constant until the Po2 reaches 60–80 mmHg, the onset of bradycardia coinciding with the loss of saturation of the haemocyanin. Although cardiac output falls during hypoxia, the capacity rate ratio remains approximately constant, which enables the effectiveness of oxygen uptake by the blood to remain at a high level.

scholarly journals RESPIRATORY EFFECTS UPON THE VISUAL THRESHOLD

1942 ◽  
Vol 25 (6) ◽  
pp. 891-903 ◽  
Author(s):  
George Wald ◽  
P. V. Harper ◽  
H. C. Goodman ◽  
H. P. Krieger
Keyword(s):  
Carbon Dioxide ◽  
Absolute Threshold ◽  
Normal Rate ◽  
Cent Oxygen ◽  
Breathing Patterns ◽  
Low Oxygen ◽  
Cent Carbon Dioxide ◽  
Visual Threshold ◽  
Oxygen Tensions ◽  
Breathing Room

Measurements are reported of the effects of respiratory stresses upon the absolute threshold of peripheral (rod) vision. Since subjects were kept wholly dark adapted and the photochemical system of the rods therefore stationary, the changes recorded may be assumed to have originated more centrally. To this degree the measurements provide a quantitative index of central nervous imbalance. Breathing room air or 32 to 36 per cent oxygen at about double the normal rate causes the visual threshold to fall to approximately half the normal value within 5 to 10 minutes. This change is due primarily to alkalosis induced by the hyperventilation, and can be abolished or reversed by adding carbon dioxide to the inspired mixtures. Normal or rapid breathing of 2 per cent carbon dioxide causes no change in threshold; with 5 per cent carbon dioxide the threshold is approximately doubled. Breathing 10 per cent oxygen at the normal rate also approximately doubles the threshold. This effect is compensated in part by rapid breathing. When 10 per cent oxygen is breathed at twice the normal rate the threshold usually falls at first, then slowly rises to supernormal levels. Due primarily to variations in their breathing patterns subjects yield characteristically different responses on sudden exposure to low oxygen tensions with breathing uncontrolled. The threshold may either rise or fall; and on release from anoxia it may rise, or fall to normal or subnormal levels. The threshold adjusts to anoxia rapidly; exposures lasting 5 to 6 hours do not produce greater or more persistent changes than those of much shorter duration.

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